CTE Risk in Sports

CTE Risk and the Most Dangerous Sports for Repetitive Head Impacts

Chronic traumatic encephalopathy, commonly known as CTE, is a neurodegenerative disease associated with exposure to repetitive head impacts. These impacts include diagnosed concussions as well as blows that produce no obvious immediate symptoms. Research increasingly indicates that cumulative exposure—the number, force, rotational acceleration, and frequency of impacts sustained over time—may be more relevant to CTE risk than a person's reported number of concussions alone.

CTE is defined by a distinctive pattern of abnormal phosphorylated tau protein around small blood vessels at the depths of cortical sulci. At present, a definitive diagnosis requires examination of brain tissue after death. Researchers are investigating blood and cerebrospinal-fluid biomarkers, brain imaging, neurological testing, and other methods that might eventually permit diagnosis during life, but no validated clinical test is yet available.

The evidence does not support a single universal ranking of dangerous sports. A sport may rank highly for diagnosed concussions, cumulative subconcussive impacts, catastrophic injuries, or neuropathologically confirmed CTE without ranking equally in every category. Risk also varies according to age, sex, playing position, competition level, career duration, rules, training practices, and previous injury history.

CTE, Concussion, and Repetitive Head Impacts

A concussion is a form of traumatic brain injury caused by forces transmitted to the brain. It may produce headaches, dizziness, confusion, memory problems, balance difficulties, mood changes, sleep disturbances, or other symptoms. Repetitive head impacts are a broader category that includes concussions and impacts that do not produce recognized symptoms.

This distinction is important because athletes can accumulate hundreds or thousands of impacts without being diagnosed with repeated concussions. Studies involving helmet sensors, instrumented mouthguards, video analysis, blood biomarkers, and brain imaging have found measurable changes in some athletes after seasons of play or controlled impact exposure even when no concussion was diagnosed.

CTE pathology and traumatic encephalopathy syndrome are also not interchangeable. CTE refers to the neuropathological disease identified after death. Traumatic encephalopathy syndrome is a research diagnosis describing certain cognitive, behavioral, or neurological symptoms in people with substantial repetitive-head-impact exposure. Such symptoms may have many possible causes and do not prove that a living person has CTE.

Brain-bank studies have established that CTE occurs in former athletes, including young and amateur participants. However, donated brains are not representative samples of everyone who played a sport. Families may be more likely to donate the brain of an athlete who experienced neurological or behavioral problems. Consequently, the percentage of CTE cases in a brain bank cannot automatically be treated as the prevalence among all participants.

Sports With the Greatest Repetitive-Impact Concerns

American Football

American football has some of the strongest evidence connecting cumulative head-impact exposure with CTE. Autopsy research has documented CTE in athletes ranging from former youth and college players to professionals. Studies have also identified a dose-response relationship: longer participation in tackle football is associated with greater odds and severity of CTE pathology among examined brain donors.

Football players experience markedly different exposures according to position. Linemen and linebackers commonly sustain very large numbers of impacts, many of which are not diagnosed as concussions. Quarterbacks, running backs, and other positions may experience fewer impacts but sometimes receive collisions of greater magnitude. Research reconstructing lifetime exposure suggests that cumulative impact force and rotational acceleration predict CTE pathology more effectively than concussion counts alone.

The effects of beginning tackle football at a young age remain contested. Some studies associate exposure before age 12 with earlier cognitive, behavioral, or mood problems, while other studies have not found clear independent associations with later-life health. The evidence is considerably clearer that tackle football produces far more head impacts than flag football. Studies of children have found tackle players sustaining many times the impact exposure recorded among flag-football participants.

Rugby

Rugby repeatedly ranks among the sports with the highest diagnosed concussion incidence. Systematic reviews and direct comparisons have often placed rugby above American football, ice hockey, and association football when risk is measured as concussions per athletic exposure or playing hour.

Former international rugby players have shown elevated rates of certain neurodegenerative diseases compared with population controls. CTE pathology has also been identified in former rugby union and rugby league players, including some young athletes. Autopsy samples remain too selective to establish the prevalence of CTE across the entire rugby population.

Tackles are a principal source of rugby head injuries. Forwards may accumulate more impacts than backs, and both the tackler and ball carrier can be injured. Attempts to lower legal tackle height have produced mixed results. Some community-level trials reduced concussion rates, while an earlier elite trial unexpectedly increased concussions among tacklers. These findings demonstrate that rule changes must be evaluated for unintended effects rather than assumed to be effective.

Boxing and Mixed Martial Arts

Boxing occupies a distinctive position because deliberate blows to an opponent's head are an accepted method of winning. The historical condition known as dementia pugilistica is now generally understood within the CTE spectrum. Longer careers, more bouts, repeated sparring, and greater overall fighting exposure have been associated with neurological abnormalities.

Research involving professional fighters has linked greater exposure with smaller brain volumes, slower processing speed, balance impairment, and other cognitive or neurological changes. Routine boxing practice can produce temporary changes in memory, motor control, and brain function even without a recognized concussion.

Mixed martial arts also carries substantial risk because of punches, kicks, elbows, knockouts, technical knockouts, and impacts with the ground. Video studies suggest that fighters may sustain concussion before a bout is stopped. Direct strikes generally produce greater rotational head acceleration than most throws or takedowns, although falls and grappling-related impacts can also cause serious injury.

Ice Hockey

Ice hockey combines speed, collisions, contact with boards, falls onto a hard surface, fighting at some levels, and body checking. It consistently appears among sports with high concussion incidence. Autopsy research has identified a dose-response association between years of hockey participation and CTE pathology among donated brains.

Body checking is one of the clearest modifiable risk factors in youth hockey. Studies comparing leagues have generally found greater injury and concussion risk when checking is permitted. Delaying or prohibiting body checking among younger athletes is therefore one of the better-supported prevention measures in sports concussion research.

Soccer

Association football usually produces fewer diagnosed concussions than rugby or American football, but intentional heading creates a distinctive source of repeated subconcussive exposure. Professional outfield players have shown higher neurodegenerative-disease risk than population controls, while goalkeepers—who head the ball much less frequently—have generally not shown the same increase.

Defenders and centre backs commonly accumulate the greatest heading exposure. Former professional defenders have shown greater neurodegenerative-disease risk than goalkeepers, strengthening concern that cumulative heading may contribute to long-term outcomes. Postmortem examinations have identified CTE in some former soccer players, although Alzheimer's disease and other pathologies frequently coexist.

The research is not entirely consistent. Some studies report cognitive, imaging, motor, or blood-biomarker changes following repetitive heading, while others find no major deterioration. These differences may reflect exposure measurement, participant age, sex, playing level, technique, career duration, and study design. The precise lifetime risk attributable to heading remains unresolved.

Other Sports With Significant Head-Injury Risk

Wrestling and Lacrosse

Wrestling has ranked among the highest-concussion-risk collegiate sports in some surveillance studies. Takedowns, throws, falls, and body-to-body collisions create repeated opportunities for head impacts. Although football produces more concussions per team because of roster size, individual wrestlers may experience a particularly high concussion rate.

Lacrosse exposes athletes to player collisions, falls, sticks, and balls. Men's and women's lacrosse have different injury mechanisms: body contact is especially important in the men's game, while sticks and balls account for many head injuries in the women's game. Instrumented-mouthguard studies show that both versions of the sport can produce impacts capable of generating substantial head acceleration and estimated brain strain.

Equestrian and Cycling Sports

Not every dangerous sport involves intentional contact. Equestrian sports carry serious head-injury risk because riders can fall from a substantial height while moving at speed. Helmets reduce skull fractures, intracranial bleeding, and severe structural injuries, but they cannot eliminate concussion.

Cycling produces a substantial number of sports-related traumatic brain injuries through crashes, falls, and collisions with motor vehicles or fixed objects. Because of its widespread participation, cycling can generate a large overall injury burden even though riders do not routinely strike their heads as part of normal participation. Helmet use provides important protection against severe head injury but does not make a cyclist immune to concussion.

Skiing, Snowboarding, and Cheerleading

Skiing and snowboarding involve speed, falls, aerial maneuvers, collisions, and impacts with hard surfaces or objects. Snowboarding and freestyle skiing frequently appear in research on sports with elevated concussion or head-injury incidence. Children and young adults may be particularly prominent among emergency-department cases.

Cheerleading carries neurological risk through falls from stunts, pyramids, tumbling, and aerial maneuvers. Although its overall injury rate has declined in some surveillance periods, reported concussions have increased. Qualified supervision, appropriate practice surfaces, progressive skill training, and restrictions on unsafe stunts are central prevention measures.

Water Polo, Basketball, Volleyball, Baseball, and Softball

Water polo athletes can receive repeated blows from other players and the ball, often under conditions that make impacts difficult for officials to observe. Goalkeepers and offensive centers may face especially high exposure. Seasonal studies have associated cumulative impacts with changes in brain functional connectivity, although the clinical meaning of these findings remains uncertain.

Concussions also occur in sports not traditionally described as collision sports. Basketball players may be injured through player contact or falls. Volleyball players can be struck by the ball or collide with teammates, equipment, or the floor. In baseball and softball, being struck in the head by a ball is a leading concussion mechanism, particularly among children.

Sex, Age, Position, and Career Duration

Risk cannot be determined from the sport's name alone. Several studies report higher diagnosed concussion rates among female athletes than male athletes participating in comparable sports such as soccer and basketball. Possible explanations include biomechanical and physiological differences, neck strength, symptom recognition, and reporting behavior. These factors remain under investigation.

Women's soccer research has found that female players may experience greater linear or rotational acceleration during some headers. Defenders generally perform more headers than midfielders or forwards. Long passes and kicks can produce particularly forceful heading situations. Better technique and lightweight training balls may reduce some exposure, although neither has been proven to eliminate long-term risk.

Age is also important. Developing brains may respond differently to repeated trauma, and young athletes can accumulate years of exposure before reaching adulthood. CTE pathology has been documented in brain donors younger than 30, including amateur athletes, although this does not reveal how commonly the disease occurs in young participants.

Career duration is among the most consistent risk indicators in football and hockey autopsy research. Greater numbers of seasons create more opportunities to accumulate impacts. Playing position, practice structure, previous concussion, style of play, and the amount of contact permitted during training can further alter exposure within the same sport.

Which Sports Are the Most Dangerous?

No single ranking answers every head-injury question. Based on the collected evidence, the major risk patterns can be summarized as follows:

• Rugby frequently ranks at or near the top for diagnosed concussion incidence per exposure.
• American football has particularly strong evidence connecting cumulative impacts and years of participation with CTE pathology.
• Boxing and mixed martial arts involve intentional head strikes and substantial cumulative brain-trauma exposure.
• Ice hockey combines a high concussion rate with repetitive collision exposure and evidence associating longer participation with CTE.
• Soccer creates concern primarily through repeated heading over long careers, especially among outfield players and defenders.
• Wrestling and lacrosse can have high concussion rates despite receiving less public attention than football.
• Equestrian sports, cycling, skiing, and snowboarding carry significant risk of acute or severe brain injury through falls and crashes.
• Cheerleading, water polo, basketball, volleyball, baseball, and softball demonstrate that meaningful concussion risk is not limited to traditional collision sports.

The sport with the highest concussion incidence is not necessarily the sport producing the largest number of injuries, the most cumulative impacts, or the greatest CTE risk. Football may produce a very large number of concussions because of participation and team size, while rugby may have a higher rate per exposure. Boxing may expose an individual directly to repeated head strikes, whereas cycling and equestrian activities may create fewer routine impacts but a substantial risk of severe injury during a crash or fall.

Prevention and Exposure Reduction

The most effective approach is to reduce the number and severity of head impacts rather than relying exclusively on recognizing concussions after they occur. Evidence-supported or promising measures include:

• limiting full-contact football practices;
• substituting flag football for tackle football, particularly for younger children;
• delaying or prohibiting body checking in youth ice hockey;
• enforcing rules against dangerous tackles, head contact, illegal stick contact, and targeting;
• reducing repetitive heading during youth soccer training;
• improving tackling, falling, heading, and landing techniques;
• using age-appropriate neuromuscular and neck-strengthening programs;
• ensuring qualified coaching and supervision;
• removing athletes immediately when concussion is suspected;
• following graduated return-to-learn and return-to-sport protocols;
• preventing same-day return after a suspected concussion; and
• using properly fitted helmets and protective equipment where appropriate.

Helmets are essential for reducing skull fractures and certain severe injuries, but no helmet can prevent all concussions or eliminate the brain's movement inside the skull. Mouthguards may reduce concussion risk in some collision sports, although their primary established function remains protection of the teeth and mouth. Protective equipment should complement—not replace—rules, coaching, exposure limits, and appropriate medical care.

Football studies show that contact-practice limits can substantially reduce head-impact exposure and practice concussions. Youth-hockey research supports restrictions on body checking. Rugby prevention studies show that rule changes can help, but they must be carefully monitored because altered player behavior may transfer risk rather than remove it.

Scientific Uncertainty and the Search for an In-Life Test

Considerable uncertainty remains about why some heavily exposed athletes develop CTE while others apparently do not. Genetics, cardiovascular health, substance use, other neurological diseases, age, total exposure, impact characteristics, and individual biological susceptibility may all affect outcomes.

Later-life cognitive or behavioral symptoms cannot automatically be attributed to CTE. Alzheimer's disease, Lewy body disease, vascular disease, mental-health conditions, sleep disorders, chronic pain, and other health problems may produce overlapping symptoms. Autopsy studies of former soccer and rugby players have frequently found mixed pathologies rather than CTE alone.

Researchers are evaluating tau PET imaging, neurofilament light, phosphorylated tau, GFAP, S100B, advanced MRI, and other possible indicators of repetitive brain trauma. Some findings are promising, but none currently provides a definitive stand-alone diagnosis of CTE during life. Head-impact sensors are also valuable research tools, although their measurements can be affected by device location, fit, calibration, and false detections.

Conclusion

The accumulated evidence indicates that repetitive head impacts deserve attention even when they do not produce diagnosed concussions. Rugby, American football, boxing, mixed martial arts, ice hockey, and soccer present some of the clearest concerns, but their risks differ in form. Rugby often has extremely high concussion incidence; football has extensive evidence connecting cumulative exposure with CTE; combat sports permit deliberate head strikes; hockey combines collision exposure with a preventable body-checking component; and soccer can expose outfield players to thousands of headers over a career.

Other activities—including wrestling, lacrosse, equestrian sports, cycling, skiing, snowboarding, cheerleading, and water polo—can also produce substantial neurological risk. The danger experienced by an individual athlete depends not only on the sport but also on age, sex, position, competition level, rules, training practices, career duration, previous injuries, and cumulative impact forces.

The evidence does not justify assuming that every contact-sport participant will develop CTE, nor does it support dismissing impacts that produce no immediate symptoms. The most responsible response is to reduce unnecessary exposure, recognize and manage concussions promptly, strengthen evidence-based safety rules, and continue long-term research capable of measuring risk in representative athlete populations.

CTE Risk and the Most Dangerous Sports for Repetitive Head Impacts

CTE: Overall Risk and Repetitive Head Impacts

1. Prevalence of Chronic Traumatic Encephalopathy in Athletes With Repetitive Head Impacts: A Systematic Review and Meta-Analysis

[PMID:40194947 | Multiple Authors | Scandinavian Journal of Medicine & Science in Sports | 2025]

A systematic review and meta-analysis of approximately 1,000 former contact-sport athletes found substantial CTE pathology among examined athletes, with particularly high estimates among rugby and American football players. The authors emphasize that estimates based on donated brains should not automatically be interpreted as prevalence among all athletes.

2. Chronic Traumatic Encephalopathy: Criteria for Neuropathological Diagnosis and Relationship to Repetitive Head Impacts

[PMID:36759368 | Ann C. McKee et al. | Acta Neuropathologica | 2023-04]

Reviews modern diagnostic criteria for CTE and the evidence connecting the characteristic tau pathology of the disease with exposure to repetitive head impacts in contact sports.

3. Examining Later-in-Life Health Risks Associated With Sport-Related Concussion and Repetitive Head Impacts

[PMID:37316187 | Grant L. Iverson et al. | British Journal of Sports Medicine | 2023-06]

A systematic review examining dementia, cognitive impairment, neurological disease, and mental-health outcomes among former amateur and professional athletes exposed to concussion and repetitive head impacts.

4. Chronic Traumatic Encephalopathy in Athletes, Players, Boxers and Military: Systematic Review

[PMID:39649931 | Multiple Authors | Systematic Review | 2024]

Reviews neuropathologically confirmed CTE in American football, soccer, rugby, boxing, other athletes, and military personnel exposed to repetitive brain trauma.

5. Chronic Traumatic Encephalopathy: State-of-the-Science Update and Narrative Review

[PMID:39834035 | Multiple Authors | Narrative Review | 2025]

Reviews the evolving scientific evidence surrounding CTE pathology, repetitive head-impact exposure, possible clinical manifestations, biomarkers, and areas of continuing uncertainty.

6. The Neuropathology of Chronic Traumatic Encephalopathy

[PMID:30482357 | Ann C. McKee et al. | Handbook of Clinical Neurology | 2018]

Describes the distinctive tau pathology of CTE and documents cases involving football, hockey, soccer, rugby, boxing, wrestling, baseball, and other repetitive-trauma exposures.

7. Chronic Traumatic Encephalopathy in Athletes: Progressive Tauopathy After Repetitive Head Injury

[PMID:19535999 | Ann C. McKee et al. | Journal of Neuropathology and Experimental Neurology | 2009]

A foundational review describing neuropathologically verified CTE and tracing the condition from its historical recognition in boxers to other athletes repeatedly exposed to head impacts.

8. The First NINDS/NIBIB Consensus Meeting to Define Neuropathological Criteria for CTE

[PMID:26667418 | Ann C. McKee et al. | Acta Neuropathologica | 2016]

Establishes consensus pathological criteria for identifying CTE, particularly abnormal phosphorylated tau concentrated around small blood vessels at the depths of cortical sulci.

9. The Second NINDS/NIBIB Consensus Meeting to Define Neuropathological Criteria for CTE

[PMID:33611507 | Kevin F. Bieniek et al. | Journal of Neuropathology and Experimental Neurology | 2021]

Refines the pathological definition of CTE and establishes standardized approaches for distinguishing low and high levels of CTE neuropathology.

10. National Institute of Neurological Disorders and Stroke Consensus Diagnostic Criteria for Traumatic Encephalopathy Syndrome

[PMID:33722990 | Douglas I. Katz et al. | Neurology | 2021-05-04]

Defines research criteria for traumatic encephalopathy syndrome, a proposed clinical syndrome associated with substantial repetitive-head-impact exposure.

American Football

11. Prevalence of Chronic Traumatic Encephalopathy at Death in NFL Players

[Daniel H. Daneshvar et al. | The BMJ | 2026-08-25]

A major population-based analysis concluded that at least 24.5 percent of former NFL players who died during 2016–2021 had confirmed CTE, establishing a conservative minimum estimate rather than simply calculating the percentage among donated brains.

12. Clinicopathological Evaluation of Chronic Traumatic Encephalopathy in Players of American Football

[Jesse Mez et al. | JAMA | 2017-07-25]

Examined 202 deceased former football players and identified CTE in 177, including 110 of 111 former NFL players whose brains had been donated. The authors stressed that the brain-bank sample was not representative of all football players.

13. Duration of American Football Play and Chronic Traumatic Encephalopathy

[PMID:31589352 | Jesse Mez et al. | Annals of Neurology | 2020]

Found a strong dose-response relationship between years of tackle-football participation and CTE pathology, with each additional year of play associated with greater odds of CTE.

14. Leveraging Football Accelerometer Data to Quantify Associations Between Repetitive Head Impacts and CTE

[PMID:37340004 | Daniel H. Daneshvar et al. | Nature Communications | 2023-06-20]

Reconstructed lifetime head-impact exposure for hundreds of football brain donors and found cumulative impact force and rotational acceleration predicted CTE better than reported concussion counts.

15. Head Impact Exposure in Collegiate Football Players

[PMID:21872862 | Joseph J. Crisco et al. | Journal of Biomechanics | 2011]

More than 286,000 impacts were recorded. Linemen and linebackers received particularly frequent impacts, while quarterbacks and running backs experienced some of the larger-magnitude impacts.

16. Frequency and Location of Head Impact Exposures in Individual Collegiate Football Players

[PMID:21062178 | Steven Rowson et al. | Journal of Athletic Training | 2010]

Shows that head-impact frequency varies substantially by football position, with linemen and linebackers accumulating particularly large numbers of impacts.

17. Blood and MRI Biomarkers of Mild Traumatic Brain Injury in Non-Concussed Collegiate Football Players

[PMID:38182718 | Multiple Authors | Scientific Reports | 2024]

Found measurable biological changes over a football season among players who had not suffered a diagnosed concussion, illustrating why subconcussive impacts are an important research concern.

18. Effects of Head Trauma Frequency and Intensity on High School Football Players in Different Positions

[PMID:40145709 | Multiple Authors | Applied Neuropsychology | 2025]

Compares high-frequency, lower-intensity positions such as linemen with positions experiencing fewer but often more intense collisions.

19. Computerized Neuropsychological Test Performance of Youth Football Players at Different Positions

[PMID:28631970 | Multiple Authors | Applied Neuropsychology: Child | 2017]

Compared youth linemen with lower-contact positions and found differences in several computerized cognitive measures, highlighting the possible importance of position-specific exposure.

20. Memory Alterations Over a Football Season Are Dependent on Athlete Position-Type and Prior Concussion History

[PMID:42268675 | Multiple Authors | Brain Injury | 2026]

Examines changes in memory across a collegiate football season and investigates how playing position and previous concussion history influence outcomes.

21. Age of First Exposure to Football and Later-Life Cognitive Impairment in Former NFL Players

[PMID:25632088 | Julie M. Stamm et al. | Neurology | 2015-03-17]

Former NFL players who began tackle football before age 12 performed worse on several later-life cognitive measures in this relatively small study.

22. Age of First Exposure to Tackle Football and Chronic Traumatic Encephalopathy

[PMID:29710395 | Michael L. Alosco et al. | Annals of Neurology | 2018]

Earlier football exposure was not associated with greater CTE pathological severity but was associated with earlier reported onset of cognitive and behavioral symptoms among players with CTE.

23. Age of First Exposure to American Football and Long-Term Neuropsychiatric and Cognitive Outcomes

[PMID:28926003 | Michael L. Alosco et al. | Translational Psychiatry | 2017]

Reports associations between younger football exposure and some later-life behavioral, mood, and executive-function problems.

24. Age of First Exposure Is Not Associated With Later-in-Life Cognitive or Mental Health Problems

[PMID:34025554 | Grant L. Iverson et al. | Frontiers in Neurology | 2021]

Provides an important counterpoint, finding no clear association between starting football before age 12 and several later-life health measures in a sample of former high-school players.

25. The Association Between Age of First Exposure to American Football and Later-Life Health Issues

[PMID:40366603 | Multiple Authors | Sports Medicine | 2025]

Another study finding that earlier starting age was not independently associated with several later-life outcomes, while greater concussion history showed stronger associations.

26. Younger Age of First Exposure to American Football and Older-Age Clinical Outcomes

[PMID:41688863 | Sophia B. Nosek et al. | Journal of Neurotrauma | 2026]

Adds newer evidence to the continuing debate over whether age at first football exposure affects later neurological and behavioral outcomes.

27. Pathologically Confirmed CTE in a 25-Year-Old Former College Football Player

[Jesse Mez et al. | JAMA Neurology | 2016-03]

Documents CTE pathology in a young former college football player, demonstrating that neuropathological changes are not confined to elderly retired professionals.

28. Cognitive and Neuropsychiatric Function in Former American Football Players

[Multiple Authors | JAMA Network Open | 2026]

Examines cognitive performance, depression, behavioral symptoms, years of football participation, playing position, and other repetitive-head-impact exposure measures in living former players.

Rugby

29. Epidemiology of Head Injuries Among Football and Rugby Players: Systematic Review and Meta-Analysis

[PMID:42115127 | Giulia Gorgoni et al. | Journal of Science and Medicine in Sport | 2026-06]

Found substantially higher concussion incidence in rugby than association football across age, sex, and participation-level groups.

30. Neurodegenerative Disease Risk Among Former International Rugby Union Players

[PMID:36195436 | Emma R. Russell et al. | Journal of Neurology, Neurosurgery & Psychiatry | 2022]

A Scottish cohort study found former international rugby players had greater risk for several neurodegenerative diseases than matched members of the general population.

31. A Systematic Review and Meta-Analysis of Concussion in Rugby Union

[PMID:25138311 | Andrew J. Gardner et al. | Sports Medicine | 2014]

Reviews concussion incidence across professional, amateur, school, men's, and women's rugby and demonstrates that concussion is a significant injury in match play.

32. Prevalence of CTE in Athletes With Repetitive Head Impacts

[PMID:40194947 | Multiple Authors | Scandinavian Journal of Medicine & Science in Sports | 2025]

In the included autopsy literature, rugby players showed one of the highest pooled proportions of CTE, although brain-donation sampling prevents this figure from being treated as population prevalence.

33. Epidemiology of Head Injuries Focusing on Concussions in Team Contact Sports

[PMID:29349651 | Florian Beaudouin et al. | Sports Medicine | 2018]

Compared elite rugby, football, ice hockey, and American football and found rugby match play among the environments with the highest concussion incidence.

34. Data-Driven Risk Classification of Concussion Rates

[PMID:33721284 | Multiple Authors | Journal of Athletic Training | 2021]

A meta-analysis classifying rugby as the highest-concussion-risk sport in the included collegiate and high-school literature, followed by American football, ice hockey, and wrestling.

35. Incidence and Risk Factors for Sport-Related Concussion in Female Youth Contact and Collision Sports

[PMID:39645635 | Multiple Authors | Sports Medicine | 2024]

Among female youth collision sports examined, rugby union produced particularly high concussion incidence estimates.

Ice Hockey

36. Duration of Ice Hockey Play and Chronic Traumatic Encephalopathy

[PMID:39630446 | Bobak Abdolmohammadi et al. | JAMA Network Open | 2024-12-04]

Found a dose-response relationship between years of hockey participation and CTE pathology among donated brains, with 27 of 28 examined former professional hockey players having CTE.

37. Duration of Ice Hockey Play and Chronic Traumatic Encephalopathy Risk

[Bobak Abdolmohammadi et al. | Neurology | 2022-05-03]

Earlier presentation of research investigating whether increasing years of ice-hockey exposure are associated with increasing CTE risk.

38. Concussion Incidence by Type of Sport

[PMID:39479865 | Multiple Authors | Journal of Orthopaedic & Sports Physical Therapy | 2024]

An overview of systematic reviews identifies ice hockey, rugby, American football, and snowboarding among sports consistently showing relatively high concussion incidence.

39. Incidence of Concussion in Contact Sports: A Systematic Review

[PMID:12963556 | Richard Koh et al. | British Journal of Sports Medicine | 2003]

One of the earlier comparative reviews identifying ice hockey and rugby as sports with especially high concussion incidence.

40. Epidemiology of Head Injuries Focusing on Concussions in Team Contact Sports

[PMID:29349651 | Florian Beaudouin et al. | Sports Medicine | 2018]

Reports substantial concussion risk in elite ice hockey and notes that female hockey players may experience higher concussion rates than male players in some datasets.

Boxing and Mixed Martial Arts

41. Chronic Traumatic Brain Injury Associated With Boxing

[PMID:10946737 | Barry D. Jordan | Seminars in Neurology | 2000]

Reviews chronic neurological injury among professional boxers and identifies longer careers, greater numbers of bouts, and increased sparring as important exposure factors.

42. Boxing—Acute Complications and Late Sequelae: From Concussion to Dementia

[PMID:21173899 | Multiple Authors | Deutsches Ärzteblatt International | 2010]

Reviews acute concussion, repeated head trauma, biochemical evidence of neuronal injury, and dementia pugilistica among boxers.

43. Dementia Pugilistica: A Severe Tribute to a Career

[PMID:25828776 | Sébastien Lepreux et al. | Clinical Neuropathology | 2015]

Describes neuropathological findings in a former professional boxer consistent with the disease now generally included within the CTE spectrum.

44. Neurochemical Profile of Dementia Pugilistica

[PMID:23268705 | Multiple Authors | Journal of Neurotrauma | 2013]

Examines persistent biochemical and structural abnormalities in the brains of former boxers with neuropathologically confirmed dementia pugilistica.

45. Repeated Head Trauma Is Associated With Smaller Thalamic Volumes and Slower Processing Speed

[PMID:25633832 | Charles Bernick et al. | British Journal of Sports Medicine | 2015]

The Professional Fighters Brain Health Study linked greater fighting exposure with smaller brain volumes and slower cognitive processing.

46. Head Injury in Mixed Martial Arts: Epidemiology, Brain Structures and Cognitive Decline

[PMID:33538222 | Multiple Authors | Physician and Sportsmedicine | 2021]

A systematic review found that head trauma represents a large proportion of MMA injuries and discusses potential long-term cognitive and neurodegenerative consequences.

47. Brain Trauma Characteristics for Lightweight and Heavyweight Fighters in Professional MMA

[PMID:34011240 | Multiple Authors | Journal of Science and Medicine in Sport | 2021]

Quantifies the frequency and magnitude of head impacts in professional MMA and demonstrates different impact profiles among weight classes.

48. Dangers of Mixed Martial Arts in the Development of Chronic Traumatic Encephalopathy

[PMID:30658408 | Multiple Authors | International Journal of Environmental Research and Public Health | 2019]

Discusses repetitive head trauma in MMA and presents clinical concerns regarding possible long-term traumatic encephalopathy.

49. Repetitive Head Impacts Among Professional Fighters

[PMID:38418380 | Multiple Authors | Journal of Clinical and Experimental Neuropsychology | 2024]

Examines traumatic encephalopathy syndrome, repetitive-head-impact exposure, and balance impairment among retired professional fighters.

50. Understanding the Consequences of Repetitive Subconcussive Head Impacts in Sport: Brain Changes After Boxing Practice

[PMID:31551732 | Thomas Di Virgilio et al. | Frontiers in Human Neuroscience | 2019]

Amateur boxers showed temporary changes in brain function, motor control, and memory after routine sparring despite not necessarily suffering a diagnosed concussion.

Soccer / Association Football

51. Risk of Cognitive Decline in Professional Soccer Players After Repetitive Subconcussive Impacts

[PMID:42036338 | Tomasz Tykocki | Neurologia Medico-Chirurgica | 2026-06-15]

A recent systematic review and meta-analysis found repetitive soccer heading associated with poorer performance across several cognitive domains, while emphasizing the need for continued longitudinal research.

52. Heading in Soccer Players and Neurologic Outcomes

[PMID:41051987 | Rachael S. Mathew et al. | Journal of Child Neurology | 2026-02]

Reviews evidence from youth through professional soccer and concludes that long-term neurological effects of heading remain incompletely resolved.

53. Quantified Head-Ball Impacts in Soccer: A Preliminary Prospective Study

[PMID:41141398 | Hugh McCloskey et al. | Neurotrauma Reports | 2025]

A small prospective MRI study found changes in white-matter measurements following a controlled series of soccer headers, with greater changes associated with greater impact magnitude.

54. Chronic Traumatic Encephalopathy in Soccer Players: Review of 14 Cases

[PMID:37403989 | Gerard Hageman, Ivar Hageman, Jik Nihom | Clinical Journal of Sport Medicine | 2024-01-01]

Reviews neuropathologically diagnosed CTE in former soccer players and raises concern that frequent heading could contribute to risk even without a history of recognized concussion.

55. Neurodegenerative Disease Among Male Elite Football Players in Sweden

[PMID:36934741 | Multiple Authors | Lancet Public Health | 2023]

Swedish elite outfield players showed higher neurodegenerative-disease risk than population controls, whereas goalkeepers did not show the same increase.

56. Association of Field Position and Career Length With Neurodegenerative Disease in Former Professional Soccer Players

[PMID:34338724 | Emma R. Russell et al. | JAMA Neurology | 2021]

Found the greatest neurodegenerative-disease risk among former defenders and substantially lower risk among goalkeepers, supporting investigation of heading exposure as a possible contributor.

57. Neurodegenerative Disease Mortality Among Former Professional Soccer Players

[PMID:31633894 | Daniel F. Mackay et al. | New England Journal of Medicine | 2019-11-07]

A landmark Scottish study found former professional soccer players had substantially higher mortality from neurodegenerative disease than matched controls.

58. The Neurological Risks of Playing Association Football

[PMID:34824860 | Multiple Authors | Clinical Medicine | 2021]

Reviews evidence surrounding soccer, concussion, heading, dementia, and CTE while emphasizing uncertainties over the precise contribution of heading.

59. Soccer and Chronic Traumatic Encephalopathy: A Short Review and Recommendation

[PMID:29213517 | Multiple Authors | Dementia & Neuropsychologia | 2017]

Discusses reported CTE cases in soccer and examines repetitive heading, concussion, player collisions, and potential preventive rule changes.

60. Chronic Traumatic Brain Injury in Professional Soccer Players

[PMID:9748028 | J.T. Matser et al. | Neurology | 1998-09]

Professional soccer players showed poorer performance in several cognitive domains than non-contact athletes, with results associated with concussion history and heading frequency.

61. Acute and Chronic Brain Injury in United States National Team Soccer Players

[PMID:8775122 | S.E. Jordan et al. | American Journal of Sports Medicine | 1996]

An early study found no clear MRI or cognitive evidence linking routine heading exposure with chronic encephalopathy, illustrating how the scientific evidence has evolved and why conflicting findings should be represented.

62. Heading in Soccer: Dangerous Play?

[PMID:21811187 | Alejandro M. Spiotta, Adam J. Bartsch, Edward C. Benzel | Neurosurgery | 2012]

Reviews biomechanical and clinical research concerning intentional soccer heading and the possibility of cumulative subconcussive brain injury.

Comparing Sports and Identifying the Highest-Risk Activities

63. Data-Driven Risk Classification of Concussion Rates

[PMID:33721284 | Multiple Authors | Journal of Athletic Training | 2021]

Across the studies included in this meta-analysis, rugby ranked highest for concussion incidence, followed by American football, ice hockey, and wrestling.

64. Concussion Incidence by Type of Sport

[PMID:39479865 | Multiple Authors | Journal of Orthopaedic & Sports Physical Therapy | 2024]

Reviews multiple meta-analyses and identifies rugby, snowboarding, ice hockey, and American football as sports with consistently high concussion rates.

65. The Incidence of Concussion in Youth Sports

[PMID:26626271 | Kathryn J. Pfister et al. | British Journal of Sports Medicine | 2016]

Among youth athletes, rugby had the highest concussion incidence in the included literature, followed by ice hockey and American football.

66. Epidemiology of Head Injuries Among Football and Rugby Players

[PMID:42115127 | Giulia Gorgoni et al. | Journal of Science and Medicine in Sport | 2026]

Provides a recent direct comparison showing considerably higher concussion incidence in rugby than association football.

67. Epidemiology of Head Injuries Focusing on Concussions in Team Contact Sports

[PMID:29349651 | Florian Beaudouin et al. | Sports Medicine | 2018]

Directly compares rugby, association football, ice hockey, and American football and illustrates why exposure must be considered separately for games and training.

68. A Systematic Review on Neurodegenerative Diseases in Professional and Varsity Athletes

[PMID:35976476 | Multiple Authors | Neurological Sciences | 2022]

Finds increased evidence of neurological disease among some populations of former soccer and American-football players and CTE among former boxers and football players.

Important Risk Factors Beyond the Name of the Sport

69. Duration of American Football Play and CTE

[PMID:31589352 | Jesse Mez et al. | Annals of Neurology | 2020]

Suggests duration of exposure is critical: longer football careers were strongly associated with increasing CTE probability and pathological severity.

70. Duration of Ice Hockey Play and CTE

[PMID:39630446 | Bobak Abdolmohammadi et al. | JAMA Network Open | 2024]

Demonstrates a similar dose-response pattern in hockey, supporting the hypothesis that accumulated exposure matters across multiple collision sports.

71. Football Accelerometer Data and CTE

[PMID:37340004 | Daniel H. Daneshvar et al. | Nature Communications | 2023]

Suggests cumulative force and rotational acceleration across thousands of hits may be more informative predictors of CTE than simply counting diagnosed concussions.

72. Head Impact Exposure in Collegiate Football Players

[PMID:21872862 | Joseph J. Crisco et al. | Journal of Biomechanics | 2011]

Demonstrates that playing position greatly changes exposure, with linemen accumulating numerous impacts even though many individual collisions are not diagnosed as concussions.

73. Soccer Field Position and Neurodegenerative Disease

[PMID:34338724 | Emma R. Russell et al. | JAMA Neurology | 2021]

The higher risk among defenders compared with goalkeepers provides epidemiological evidence that exposure within the same sport can vary substantially according to position.

Broad Comparisons of Concussion and Repetitive Head-Impact Risk

74. About Repeated Head Impacts

| Centers for Disease Control and Prevention | CDC | 2024-05-16

Repeated head impacts include both impacts that cause diagnosed concussions and impacts that cause no immediate symptoms. The CDC emphasizes growing concern about the cumulative neurological effects of repeated sports collisions.

75. Preventing Concussion

| Centers for Disease Control and Prevention | CDC HEADS UP | 2025

Sports organizations can reduce head-impact exposure through safer rules, fewer contact practices, enforcement against dangerous head contact, and alternatives such as flag football.

76. Consensus Statement on Concussion in Sport: Amsterdam 2022

| Jon S. Patricios et al. | British Journal of Sports Medicine | 2023-06-14

The international consensus statement reviews concussion recognition, treatment, prevention, return-to-play decisions, retirement considerations, and research concerning possible long-term neurological effects of sports-related head trauma.

77. Traumatic Brain Injury and Chronic Traumatic Encephalopathy

| National Institute of Neurological Disorders and Stroke | NIH/NINDS | 2026

NINDS describes CTE as a progressive neurological disorder associated with repeated brain trauma and notes reported cases involving boxing, soccer, wrestling, football, rugby, and other activities involving repeated head impacts.

78. The DIAGNOSE-CTE Research Project

| National Institute of Neurological Disorders and Stroke | NIH/NINDS | 2026

The DIAGNOSE-CTE project is investigating whether imaging, blood, spinal-fluid, genetic, and clinical markers can eventually help identify CTE during life rather than only through postmortem neuropathological examination.

79. Avenues for Prevention Using the Epidemiology of Sport-Related Concussion

| Multiple Authors | Journal of Neurosurgery: Pediatrics | 2024

Analysis of more than two million high-school athletes documented more than 25,000 sports-related concussions and demonstrates substantial differences in concussion burden according to sport and sex.

80. Concussion Incidence and Trends in 20 High School Sports

| Multiple Authors | Pediatrics | 2019

Football had the highest concussion rate among the 20 sports examined. Girls had substantially higher concussion rates than boys in comparable sports, illustrating that collision sport participation is not the only determinant of concussion risk.

81. Epidemiology of Concussions Among United States High School Athletes in 20 Sports

| Multiple Authors | American Journal of Sports Medicine | 2012

Football produced the greatest number and highest rate of concussions, followed by boys' ice hockey and boys' lacrosse in concussion rate. Girls' soccer contributed a substantial number of injuries.

82. Epidemiology of Sports-Related Concussion in Seven US High School and Collegiate Sports

| Multiple Authors | Injury Epidemiology | 2017

Among football, soccer, lacrosse, and ice hockey athletes, football showed the highest observed concussion incidence. A recent concussion history was an important predictor of another concussion.

83. Epidemiology of Sport-Related Concussion

| Multiple Authors | Neurologic Clinics | 2021

Reviews concussion epidemiology across sports and identifies football, wrestling, ice hockey, and lacrosse as particularly important collision or contact sports while also noting high rates in women's soccer.

Sex Differences and Female Athletes

84. Sex-Based Differences in the Incidence of Sports-Related Concussion

| Multiple Authors | Systematic Review and Meta-Analysis | 2019

Female athletes had significantly higher reported concussion incidence than male athletes in soccer and basketball, demonstrating that concussion risk can differ substantially between men and women playing comparable sports.

85. Sport-Related Concussion in Female Athletes: A Systematic Review

| Multiple Authors | Systematic Review | 2020

Reviews evidence that female athletes may have different concussion susceptibility, symptom patterns, recovery characteristics, reporting behavior, and biomechanical responses than male athletes.

86. Trends in Concussion Incidence in High School Sports: An 11-Year Study

| Multiple Authors | American Journal of Sports Medicine | 2011

Football had the highest concussion incidence, while girls' soccer had the highest rate among girls' sports. Girls had roughly twice the concussion risk of boys in several comparable sports.

Lacrosse

87. Differences in the Mechanism of Head Impacts Between Men's and Women's Lacrosse

| Multiple Authors | American Journal of Sports Medicine | 2019

Men's lacrosse players commonly experienced head-to-body impacts, whereas stick-to-head impacts were prominent in women's lacrosse. Many impacts that could have resulted in penalties were not penalized.

88. Injury Incidence in Youth, High School, and NCAA Men's Lacrosse

| Multiple Authors | Pediatrics | 2019

Youth boys' lacrosse showed a higher concussion rate than the high-school and NCAA populations studied, demonstrating that significant head-injury exposure can begin well before college.

89. Injuries in High School Girls' and NCAA Women's Lacrosse

| Multiple Authors | Journal of Athletic Training | 2019

Concussion was one of the most important injuries in women's lacrosse and the most common diagnosis for numerous player positions, with sticks and balls contributing importantly to contact injuries.

90. Injuries in High School Boys' and NCAA Men's Lacrosse

| Multiple Authors | Journal of Athletic Training | 2019

Concussion was the most frequent competition diagnosis among high-school boys across player positions, demonstrating the importance of collision exposure in men's lacrosse.

91. Head, Face, and Eye Injuries in Scholastic and Collegiate Lacrosse

| Multiple Authors | American Journal of Sports Medicine | 2007

Concussion constituted a large share of male lacrosse head injuries, while women sustained significant head and facial injuries largely from stick and ball contact.

92. Head Impact Kinematics and Brain Tissue Strains in High School Lacrosse

| Multiple Authors | Journal Article | 2024

Instrumented mouthguards documented head acceleration events in boys' and girls' high-school lacrosse and allowed researchers to estimate resulting brain-tissue strain.

93. Quantifying Head Impact Exposure in Female High School Lacrosse

| Multiple Authors | Journal Article | 2022

Instrumented mouthguards and video verification showed head impacts from sticks, player contact, and falls, with stick contact producing some of the largest measured impact kinematics.

94. Assessing Women's Lacrosse Head Impacts Using Finite Element Modelling

| Multiple Authors | Journal of Biomechanics | 2018

Modeling suggested that falls and ball impacts can generate brain strains within ranges associated with concussion and that protective equipment can reduce some impact forces.

95. Impact Mitigation Properties of Women's Lacrosse Headgear

| Multiple Authors | Annals of Biomedical Engineering | 2022

Laboratory testing found that women's lacrosse headgear could reduce several measures of linear and rotational acceleration under particular impact conditions.

96. Epidemiology of Lacrosse Injuries in High School-Aged Girls and Boys

| Multiple Authors | American Journal of Sports Medicine | 2005

Boys experienced more concussive events associated with player-to-player contact, while girls experienced more overall head injuries involving stick and ball impacts.

Wrestling

97. Wrestling-Related Concussions and Closed Head Injuries Predominantly Occur in High School-Age Athletes

| Multiple Authors | Journal of Sports Medicine and Physical Fitness | 2020

Emergency-department data showed thousands of estimated wrestling-related concussions and closed head injuries annually, with ages 15 and 16 representing particularly prominent groups.

98. Epidemiology of Injuries in NCAA Men's Wrestling

| Multiple Authors | Journal of Athletic Training | 2021

Concussion was the most frequently reported specific injury in NCAA men's wrestling during the surveillance period, while head and face injuries represented a substantial portion of all injuries.

99. First Decade of Web-Based Sports Injury Surveillance: Wrestling

| Multiple Authors | Journal of Athletic Training | 2019

Head and face injuries were common in both high-school and collegiate wrestling, emphasizing the head-impact burden of a sport that involves throws, takedowns, and body-to-body collisions.

100. Epidemiologic Measures for Concussion in NCAA Sports

| Multiple Authors | Journal of Athletic Training | 2016

Men's wrestling had the highest concussion rate and individual concussion risk among the NCAA sports analyzed, although football generated the greatest average number of concussions per team.

Martial Arts, Boxing, and Mixed Martial Arts

101. Ten-Year Patterns of Concussion Injuries Among Martial Arts Disciplines

| Multiple Authors | Journal Article | 2025

Emergency-department data covering karate, jiu-jitsu, taekwondo, MMA, kickboxing, and judo found continuing concussion injuries from falls, strikes, kicks, throws, and other mechanisms.

102. Injuries in Taekwondo: Systematic Review

| Multiple Authors | Systematic Review | 2017

Concussion represented an important injury in taekwondo. The authors suggested consideration of rule changes involving head kicks and greater availability of non-contact participation.

103. Rotational Head Acceleration and Traumatic Brain Injury in Combat Sports

| Multiple Authors | British Medical Bulletin | 2022

A systematic review of boxing, MMA, taekwondo, judo, and wrestling found that direct strikes to the head generated greater rotational acceleration than most throws and takedowns.

104. Concussion and Executive Functions in Combat Sports

| Multiple Authors | Systematic Review | 2024

Most included studies reported impairment in at least some executive functions among combat-sport athletes following concussion, with memory and inhibitory control frequently examined.

105. Epidemiology of Injuries in Mixed Martial Arts

| Reidar P. Lystad et al. | American Journal of Sports Medicine | 2014

The head was the most commonly injured anatomical region in the included MMA studies. Fighters losing by knockout or technical knockout experienced particularly high injury exposure.

106. Occurrence and Outcomes of Concussion and Mild TBI in MMA

| Multiple Authors | Systematic Review | 2022

Reviews studies showing substantial mild traumatic brain injury and concussion exposure among MMA fighters, with reported effects on memory, reaction time, and information-processing speed.

107. Craniofacial and Traumatic Brain Injuries in Mixed Martial Arts

| Multiple Authors | Journal Article | 2021

Head injuries were common in sanctioned MMA fights, traumatic brain injuries were prominent, and knockout or technical-knockout bouts produced especially high head-injury rates.

108. Concussion Occurrence and Recognition in Professional Boxing and MMA

| Multiple Authors | Journal Article | 2021

Video analysis suggested concussions frequently occurred before fights were stopped. The fighter sustaining the first identified concussion ultimately lost almost every bout examined.

109. Systematic Review and Meta-Analysis Investigating Head Trauma in Boxing

| Multiple Authors | Journal Article | 2023

Reviews acute and chronic neurological consequences of boxing and reports substantial evidence of concussion, structural brain abnormalities, and cognitive problems among studied boxers.

110. Epidemiology of Injuries During Judo Tournaments

| Multiple Authors | Systematic Review | 2024

The head was the most frequently reported injured body region across the judo tournament literature reviewed, although estimates varied greatly between studies.

111. Severe Head Injuries During Judo Practice

| Multiple Authors | Japanese Clinical Study | 2011

Reports catastrophic judo head injuries, particularly acute subdural hematomas, and highlights the danger of returning to training after earlier symptoms or head trauma.

112. Epidemiology of Competition Injuries in Elite European Judo Athletes

| Multiple Authors | Clinical Journal of Sport Medicine | 2019

The head and neck were the most frequently injured anatomical region in this elite competition cohort, although overall injury rates were lower than those reported for some striking martial arts.

113. Sport-Related Concussions Among Middle- and High-School Students in Japan

| Multiple Authors | Nationwide Epidemiological Study | 2026

Rugby had the highest concussion incidence among the sports examined, followed by judo and karate, identifying martial arts as an important component of adolescent head-injury prevention.

Equestrian Sports

114. Incidence of Concussions and Helmet Use in Equestrians

| Beth W. Glace et al. | Journal of Science and Medicine in Sport | 2023-02

Equestrian participants reported a substantial lifetime burden of concussion, with riding presenting greater incidence than driving or handling horses. Falls remain the central mechanism of head trauma.

115. Does Equestrian Helmet Type Affect Head Injury?

| Sara Gould et al. | Clinical Journal of Sport Medicine | 2025-11-01

More than half of the collegiate riders surveyed reported a fall during one year, and concussion was the most frequently reported head injury. No particular helmet brand or MIPS status clearly eliminated concussion risk.

116. Head and Spinal Injuries in Equestrian Sports

| Jennifer K. Gates and Cindy Y. Lin | Current Sports Medicine Reports | 2020-01

Reviews the substantial traumatic-brain-injury risk created by falls from horses, the height of the rider, and the speed and unpredictability associated with equestrian activities.

117. Helmet Use in Equestrian Athletes: Opportunities for Intervention

| Multiple Authors | Journal Article | 2021

Survey research found a substantial history of head injury among riders and identified inconsistent helmet use as a preventable component of equestrian brain-injury risk.

118. Impact of Helmet Use in Equestrian-Related Traumatic Brain Injury

| Multiple Authors | Journal Article | 2018

Unhelmeted horseback riders had substantially more intracranial hemorrhage and more severe brain injuries than comparable helmeted riders.

119. Do Equestrian Helmets Prevent Concussion?

| Multiple Authors | Sports Medicine | 2019

Examination of helmets from real-world equestrian accidents showed that concussion remained common despite helmet use, while helmets appeared more effective at preventing skull fracture and severe structural injury.

Cycling and Severe Head-Injury Risk

120. Not Just Contact Sports: Significant Numbers of Sports-Related Concussions in Cycling

| Multiple Authors | Journal Article | 2018

A large cyclist survey found a considerable history of concussion, emphasizing that falls and crashes can create a substantial concussion burden outside traditional contact sports.

121. Reporting of Concussion-Like Symptoms After Cycling Crashes

| Multiple Authors | Journal Article | 2020

Cyclists reporting head injury after crashes frequently described concussion symptoms, loss of consciousness, memory loss, and significant helmet damage.

122. Sports- and Recreational Cycling-Related Traumatic Brain Injury

| Multiple Authors | Multicenter Study | 2021

Cycling accounted for the majority of hospitalized sports-related traumatic brain injuries in this Hong Kong study, and helmet use was associated with protection against intracranial hemorrhage.

Skiing, Snowboarding, Cheerleading, and Other Sports

123. Head Injuries Among World Cup Alpine and Freestyle Skiers and Snowboarders

| Multiple Authors | British Journal of Sports Medicine | 2014

Concussion represented the majority of recorded head and face injuries among elite snow-sport athletes. Freestyle skiing had the highest head-injury incidence among the disciplines examined.

124. Incidence of Injuries in Professional Snow Sports

| Multiple Authors | Systematic Review and Meta-Analysis | 2020

Professional skiing and snowboarding carry substantial injury risk, with freestyle skiing showing particularly high overall injury incidence.

125. Skiing- Versus Snowboarding-Related Concussions

| Multiple Authors | Clinical Journal of Sport Medicine | 2017

Emergency-department surveillance found thousands of skiing- and snowboarding-related concussions, with children and young adults showing higher incidence than older participants.

126. Head Injury and Helmet Trends in Alpine Skiing and Snowboarding

| Multiple Authors | Journal of Science and Medicine in Sport | 2020

Head injuries represented roughly one-tenth of reported injuries in western Canadian resorts, with snowboarders experiencing a greater proportion of head injuries than skiers.

127. Systematic Review of Cheerleading Injuries

| Multiple Authors | Systematic Review | 2025

Cheerleading's overall injury rate declined in recent years, but reported concussions increased, highlighting the particular neurological risk created by falls, stunts, pyramids, and aerial maneuvers.

128. Safety in Cheerleading: Epidemiology and Recommendations

| American Academy of Pediatrics | Pediatrics | 2024

Reviews concussion and catastrophic injury risks in youth cheerleading and recommends safety policies, qualified supervision, appropriate surfaces, and improved injury prevention.

129. Progress in Cheerleading Safety

| Multiple Authors | American Journal of Sports Medicine | 2022

Although overall cheerleading injuries declined between 2010 and 2019, estimated concussions and closed head injuries increased substantially.

130. Epidemiology of Cheerleading Stunt-Related Injuries

| Multiple Authors | Journal of Athletic Training | 2009

Stunts accounted for nearly all concussions and closed head injuries recorded in this surveillance study, showing why aerial maneuvers are a central brain-injury prevention target.

131. Epidemiology of Cheerleading Fall-Related Injuries

| Multiple Authors | Journal of Athletic Training | 2009

Most fall-related injuries occurred while athletes attempted stunts or pyramids, with concussion and closed head injuries forming part of the injury burden.

132. Concussion in Field Hockey

| Multiple Authors | Journal Article | 2018

Player collisions were the leading identified concussion mechanism among elite field-hockey players, followed by impacts involving sticks and balls.

133. Dynamics of Concussive Head Impacts in Rugby and Australian Rules Football

| A. S. McIntosh, P. McCrory and J. Comerford | Medicine & Science in Sports & Exercise | 2000-12

Biomechanical analysis of medically confirmed concussions in rugby and Australian rules football found that most involved direct head contact, often from another player's arm, shoulder, or torso.

CTE in Younger and Amateur Athletes

134. Neuropathologic and Clinical Findings in Young Contact Sport Athletes Exposed to Repetitive Head Impacts

| Ann C. McKee et al. | JAMA Neurology | 2023

Researchers examined 152 brain donors younger than 30 who had participated in contact sports. CTE was identified in 63 donors, most with mild-stage disease, demonstrating that CTE pathology can occur in young amateur as well as professional athletes.

135. Amateur Soccer Heading and Acute Elevations in Blood-Based p-Tau217 and S100B

| Multiple Authors | JAMA Neurology | 2026

Real-world soccer matches were used to investigate whether heading exposure produces measurable changes in blood biomarkers associated with neural injury. The study adds new evidence concerning acute biological responses to ordinary soccer heading.

Women's Soccer and Repetitive Heading

136. Changes in Peripheral Blood and Cognitive Performance After Nonconcussive Head Impacts in Elite Female Soccer Players

| Multiple Authors | Journal Article | 2025

Repetitive heading was associated with acute changes in tau and phosphorylated tau in female players as well as short-term changes in attention and cognitive flexibility, suggesting that impacts not diagnosed as concussions may still produce measurable biological responses.

137. Exploring Sex-Based Variations in Head Kinematics During Soccer Heading

| Multiple Authors | Annals of Biomedical Engineering | 2025

Female participants experienced greater linear and angular acceleration during controlled soccer heading than male participants. Differences in head mass were identified as one factor that may contribute to sex-related differences in impact biomechanics.

138. Video Analysis of Head Impacts in Top-Level Female Football Players

| Multiple Authors | Sports Medicine Research | 2026

Analysis of 135 professional women's soccer matches recorded more than 9,000 headers. Defenders performed substantially more headers than midfielders or forwards, identifying position as an important determinant of cumulative exposure.

139. A Prospective Investigation of the Effects of Soccer Heading on Cognitive and Sensorimotor Performances in Semi-Professional Female Players

| Jan Kern, Philipp Gulde and Joachim Hermsdörfer | Frontiers in Human Neuroscience | 2024-02-09

Eighteen months of follow-up did not reveal major cognitive deterioration but found subtle changes in fine motor and postural control associated with heading exposure.

140. Characterization of Head Impact Exposure in Women's Collegiate Soccer

| Multiple Authors | Journal Article | 2021

Instrumented mouthguards showed that purposeful headers accounted for approximately 89 percent of measured head impacts. Long kicks produced particularly high linear and rotational acceleration.

141. The Incidence and Characteristics of Heading in the 2019 FIFA Women's World Cup

| Multiple Authors | Journal Article | 2024

Video analysis found substantial variation in heading exposure according to playing position. Centre backs headed most frequently, while long-distance passes produced many heading situations.

142. Assessing the Association Between On-Field Heading Technique and Head Impact Kinematics in Female Youth Soccer

| Multiple Authors | Journal Article | 2023

Better heading technique was associated with lower rotational acceleration under some match conditions, suggesting that technique training may be one possible method of reducing impact intensity.

143. Examining the Influence of the Get aHEAD Safely in Soccer Program

| Multiple Authors | Journal Article | 2022

A heading-training program improved some measures of neck strength in young female soccer players, although clear reductions in measured head acceleration were not demonstrated.

144. Analysis of Head Impact Biomechanics in Youth Female Soccer Players Following a Heading Intervention

| Multiple Authors | Journal Article | 2021

Researchers examined balance, neurocognitive performance, and impact biomechanics following controlled heading and found that lightweight balls may provide a useful way of teaching technique with reduced impact exposure.

145. Repetitive Soccer Heading Adversely Impacts Short-Term Learning Among Adult Women

| Multiple Authors | Journal of Science and Medicine in Sport | 2022

Greater heading exposure over the preceding year was associated with poorer short-term learning among women but not men in this study, adding evidence that biological responses may differ by sex.

Youth Tackle Football Versus Flag Football

146. Head Impact Exposures Among Youth Tackle and Flag American Football Athletes

| Dana Waltzman et al. | Sports Health | 2021

Sensor measurements from 524 children ages 6 to 14 found tackle-football players experienced approximately 15 times more head impacts per athletic exposure and approximately 23 times more impacts of at least 40g than flag-football players.

147. Differences in Head Impact Exposures Between Youth Tackle and Flag Football Games and Practices

| Multiple Authors | American Journal of Sports Medicine | 2021

Youth tackle players experienced dramatically more head impacts during both games and practices than flag-football athletes. Games produced particularly high exposure among tackle players.

148. A Comparison of Youth Flag and Tackle Football Head Impact Biomechanics

| Robert C. Lynall et al. | Journal of Neurotrauma | 2019

Tackle-football players sustained far more head impacts than flag players. Flag football was not completely free of impacts, but its overall impact frequency was much lower.

149. Head Impact Biomechanics in Youth Flag Football

| Multiple Authors | American Journal of Sports Medicine | 2021

Head impacts occurred even in flag football, although at relatively low frequency. Older children and game participation were associated with greater impact exposure.

150. Youth Exposure to Repetitive Head Impacts From Tackle Football and Long-Term Neurologic Outcomes

| Robert A. Stern et al. | Journal Article/Review | 2019

Reviews the evidence concerning childhood tackle-football exposure and later neurological health, emphasizing both the biological concern surrounding repetitive impacts during brain development and significant remaining scientific uncertainties.

151. Exposure to Head Impacts and Cognitive and Behavioral Outcomes in Youth Tackle Football Players Across Four Seasons

| Multiple Authors | JAMA Network Open | 2021

Children were followed across multiple tackle-football seasons using helmet-based impact sensors and standardized cognitive and behavioral assessments to investigate whether cumulative exposure predicted measurable changes.

152. Head Impact Exposure of a Youth Football Team Over Eight Consecutive Seasons

| Jason C. Dorman et al. | Medicine & Science in Sports & Exercise | 2022

More than 33,000 impacts were measured over eight seasons. Impacts per practice and game declined substantially over time, showing that coaching methods and practice structure can meaningfully reduce exposure.

153. Head Impact Exposure Measured in a Youth Football Team During Practice Drills

| Multiple Authors | Journal of Neurosurgery: Pediatrics | 2018

Different practice drills produced very different exposure patterns. Open-field tackling produced some of the highest-magnitude impacts, while multiplayer tackling generated particularly frequent impacts.

154. Youth Tackle Football Head-Impact Estimation by Players and Parents

| Julianne D. Schmidt et al. | Journal of Athletic Training | 2023

Players and parents were generally unable to estimate actual head-impact frequency, severity, or location accurately, suggesting that repetitive-impact exposure can be difficult to perceive without objective monitoring.

Reducing Football Head Impacts

155. Football Players' Head-Impact Exposure After Limiting Full-Contact Practices

| Multiple Authors | Journal of Athletic Training | 2016

A statewide restriction on full-contact high-school football practices was followed by an approximately 42 percent reduction in head-impact exposure, with particularly large reductions among linemen.

156. Effect of a New Rule Limiting Full-Contact Practice on Concussion Incidence in High School Football

| Multiple Authors | American Journal of Sports Medicine | 2019

Practice concussion rates declined by approximately 57 percent after limits were placed on the amount and duration of full-contact practice.

157. A Helmetless-Tackling Intervention for Decreasing Head Impact Exposure

| Multiple Authors | Journal of Science and Medicine in Sport | 2019

Researchers tested whether controlled tackling and blocking drills without helmets and shoulder pads could encourage players to avoid using their heads as the point of contact.

Water Polo

158. The Epidemiology of Sports-Related Head Injury and Concussion in Water Polo

| Multiple Authors | Frontiers in Neurology | 2016

In a large survey of water-polo participants, 36 percent reported having sustained a concussion while playing. Goalkeepers reported particularly high exposure and concussion prevalence.

159. Patterns of Head Impact Exposure in Men's and Women's Collegiate Club Water Polo

| Multiple Authors | Journal of Science and Medicine in Sport | 2020

Instrumented players demonstrated repeated head impacts during competition. Offensive centers sustained the greatest number of impacts, illustrating substantial position-specific variation.

160. Head Impacts Sustained by Male Collegiate Water Polo Athletes

| Multiple Authors | Journal Article | 2019

Sensors worn across three collegiate seasons documented repeated head impacts, particularly when players occupied offensive positions.

161. Incidence of Concussions in Elite Female Water Polo

| Multiple Authors | Clinical Journal of Sport Medicine | 2023

Ten years of surveillance among elite Canadian women identified repeated concussion injuries. Goalkeepers had particularly high concussion rates.

162. A Dose Relationship Between Brain Functional Connectivity and Cumulative Head Impact Exposure in Collegiate Water Polo Players

| Multiple Authors | Frontiers in Neurology | 2020

Athletes with greater cumulative head-impact exposure showed measurable changes in whole-brain functional connectivity over a season, although conventional cognitive testing did not reveal corresponding major deficits.

163. Effectiveness of Protective Headgear in Attenuating Ball-to-Forehead Impacts in Water Polo

| Multiple Authors | Frontiers in Bioengineering and Biotechnology | 2020

Laboratory testing found that specialized protective water-polo headgear reduced both linear and rotational acceleration compared with conventional caps during simulated ball strikes.

Women's Collegiate Sports Beyond Traditional Collision Sports

164. Beyond Contact: Epidemiology of Concussion Incidence in Women's Collegiate Sports, 2016–2022

| Multiple Authors | Journal of Athletic Training | 2026

Analysis of more than 1,000 concussions among female collegiate athletes found high incidence in volleyball, basketball, water polo, and soccer, demonstrating that substantial concussion risk also exists outside traditional collision sports.

165. Concussions in the Women's National Basketball Association

| Multiple Authors | Orthopaedic Journal of Sports Medicine | 2022

Seventy documented concussions involving 55 WNBA players were identified between 1997 and 2020. The study examined return-to-play timing and performance after concussion.

166. Injuries in US High School Girls' and NCAA Women's Basketball

| Multiple Authors | Journal of Athletic Training | 2019

Concussion was among the most common specific injuries in both high-school and collegiate women's basketball, frequently resulting from contact with another player.

Volleyball

167. Self-Reported Concussion Prevalence and Risk Factors Among Volleyball Players

| Gamze Nedzhipoglu, Amanda Johnson and Nick Dobbin | PLOS ONE | 2025-12-05

Examines concussion prevalence, mechanisms, reporting behavior, and help-seeking among volleyball players, an important sport that historically received much less concussion research than football or rugby.

168. Non-Time-Loss and Time-Loss Injuries in Secondary School Girls' Volleyball

| Multiple Authors | Journal Article | 2022

Head and facial injuries accounted for a meaningful portion of injuries among secondary-school volleyball athletes, with concussion among the diagnoses captured through injury surveillance.

Baseball and Softball

169. Epidemiological Analysis of Pediatric Baseball and Softball Concussions in United States Emergency Departments

| Varag Abed et al. | American Journal of Emergency Medicine | 2023-07

Nearly 55,000 estimated pediatric concussion cases were analyzed. Approximately 63 percent resulted from the player's head being struck by a ball, making ball impact the dominant concussion mechanism.

170. Sport-Related Concussions in Baseball and Softball: Do Mechanisms of Injury Affect Recovery?

| Multiple Authors | Journal Article | 2024

Half of the concussions studied involved head-to-ball contact. Collisions with the ground, wall, or equipment were associated with longer return-to-learn times.

Motorsport

171. Brain Health in Former Professional Motorsport Drivers

| Kévin Polet et al. | Sports Medicine - Open | 2026-05-28

Former professional racing drivers with decades of exposure to crashes, concussion, and repeated high g-forces underwent neurological testing and advanced imaging. Abnormalities were common in this small exploratory case series, although the sample was too small to establish population risk.

Australian Rules Football

172. Concussion Incidence and Time-Loss in Australian Football: A Systematic Review

| Claire McNeel et al. | Journal of Science and Medicine in Sport | 2020

Forty-two studies demonstrated substantial concussion incidence in Australian football, although estimates differed considerably by competition level and diagnostic methods.

173. Concussion Incidence and Mechanisms Differ Between Elite Females and Males in Australian Football

| Multiple Authors | Journal of Science and Medicine in Sport | 2024

Elite women experienced more than twice the concussion incidence of elite men in the period examined. Tackling, bumping, head contact, and ground impacts were especially important mechanisms in women's competition.

174. Concussion Incidence and Recurrence in Professional Australian Football: A 14-Year Analysis

| Multiple Authors | Journal of Science and Medicine in Sport | 2017

Long-term surveillance documented 140 concussions and an incidence of 17.6 concussions per 1,000 player match-hours in one professional Australian football team.

175. Concussion in Community Australian Football

| Multiple Authors | Journal Article | 2016

Most concussions occurred through player-to-player body contact or tackling. The study also documented historically concerning rates of athletes returning to the same game after concussion.

Rugby League and Women's Rugby

176. Head Impact Exposure From Match Participation in Women's Rugby League

| Multiple Authors | Journal of Science and Medicine in Sport | 2018

Female rugby-league players experienced an average of approximately 14 head impacts per player per match. Forwards received more impacts and generally greater impact magnitudes than backs.

177. Instrumented Mouthguards in Women's Rugby League

| Multiple Authors | Sports Medicine Research | 2026

Instrumented mouthguards worn by 136 Women's Super League players quantified head-acceleration exposure during the 2024 season and demonstrated substantial differences between positions and individual players.

178. Comparing Match Injuries in Elite Men's and Women's Rugby League

| Multiple Authors | Journal of Science and Medicine in Sport | 2024

Concussion produced the greatest head-and-face injury incidence in both men's and women's Super League rugby. Overall injury incidence was similar between sexes.

Direct Evidence of CTE in Rugby

179. Chronic Traumatic Encephalopathy Neuropathologic Change in Former Australian Rugby Players

| Multiple Authors | Journal Article | 2024

Neuropathologists applied modern consensus CTE criteria to brains from six former elite Australian rugby-code players, expanding pathological evidence beyond American football.

180. The Perils of Contact Sport: CTE Neuropathologic Change in a 23-Year-Old Rugby Union Player

| Edward B. Lee et al. | Acta Neuropathologica | 2023

Neuropathological examination identified CTE changes in a 23-year-old rugby union player, demonstrating that characteristic pathology can develop after comparatively young-age repetitive-impact exposure.

181. Chronic Traumatic Encephalopathy in Two Former Australian National Rugby League Players

| Multiple Authors | Acta Neuropathologica Communications | 2019

Postmortem examinations identified CTE pathology in two former professional Australian rugby-league players, adding rugby league to the sports with neuropathologically confirmed cases.

182. Chronic Traumatic Encephalopathy Is a Common Co-Morbidity but Less Frequent Primary Dementia in Former Soccer and Rugby Players

| Edward B. Lee et al. | Acta Neuropathologica | 2019

CTE pathology was found in several former soccer and rugby players with dementia, but other diseases such as Alzheimer's frequently coexisted and in many cases appeared to be the major cause of dementia.

183. Evidence of Blood-Brain Barrier Disruption in Stage IV Chronic Traumatic Encephalopathy

| Multiple Authors | Neuropathology Research | 2026

Examination of a retired elite rugby-union player with stage IV CTE found evidence of blood-brain-barrier abnormalities overlapping areas containing dense abnormal tau deposition.

Ice Hockey: Body Checking as a Preventable Risk

184. Research Progress on Common Sports Injuries Among Youth Ice Hockey Players and Prevention Strategies

| Multiple Authors | Narrative Review | 2025

Reviews evidence identifying body checking as one of the strongest modifiable concussion risks in youth hockey and reports substantial reductions in injuries after checking restrictions.

185. Concussions in Ice Hockey: NHL Analysis, Systematic Review, and Concussion Protocol Analysis

| Multiple Authors | Journal Article | 2024

More than 1,000 NHL concussions were identified between the 2000–2001 and 2022–2023 seasons. Youth rules eliminating body checking emerged among the strongest evidence-based preventive measures.

186. A Systematic Review of the Association Between Body Checking and Injury in Youth Ice Hockey

| Joel M. Warsh et al. | Clinical Journal of Sport Medicine | 2009

Nearly all comparative studies reviewed found greater injury risk when body checking was permitted, supporting policies that delay or prohibit checking among younger players.

187. Risk Factors for Injury and Severe Injury in Youth Ice Hockey

| Carolyn A. Emery et al. | Injury Prevention | 2010

Meta-analysis identified body checking as an important risk factor for both overall injury and concussion in youth ice hockey.

188. Does Disallowing Body Checking in 13- to 14-Year-Old Ice Hockey Reduce Concussion?

| Multiple Authors | British Journal of Sports Medicine | 2019

Canadian leagues that prohibited body checking were compared with leagues that permitted it, providing direct evidence supporting checking restrictions as a concussion-prevention strategy.

Rugby Rule Changes and Prevention

189. Tackle Behaviour Trial Lowers Concussion and Overall Injury Rates

| Multiple Authors | Journal of Science and Medicine in Sport | 2026

Lowering the legal tackle height in Irish community rugby was associated with substantial reductions in tackle-related concussion among adult men and women, although the same benefit was not clearly demonstrated among schoolboys.

190. Does Reducing Tackle Height Through Law Change Reduce Concussion in Elite Rugby Union?

| Multiple Authors | British Journal of Sports Medicine | 2021

An earlier English trial reduced head-and-neck contact but unexpectedly failed to reduce overall concussion incidence and increased concussion among tacklers, illustrating how rule modifications can have unintended effects.

191. Prevention Strategies and Modifiable Risk Factors for Sport-Related Concussions and Head Impacts

| Carolyn A. Emery et al. | British Journal of Sports Medicine | 2023

Meta-analysis found lower concussion rates with mouthguards in collision sports, restrictions on body checking in youth hockey, limitations on football contact practices, and some rugby neuromuscular-training programs.

192. Pediatric Sport-Related Concussion: Recommendations From the Amsterdam Consensus Statement

| Multiple Authors | Pediatrics | 2023

Reviews prevention and management specifically for children and adolescents and supports measures including hockey body-checking restrictions, mouthguards, and appropriate rugby neuromuscular training.

Biomarkers and the Search for an In-Life CTE Test

193. The Use of Biofluid Markers to Evaluate Sport-Related Subconcussive Head Impact Exposure

| Multiple Authors | Scoping Review | 2024

Reviews research involving tau, phosphorylated tau, neurofilament light, GFAP, S100B, and other biomarkers after repetitive sports impacts. Neurofilament light showed promise, but the evidence remains insufficient for routine clinical diagnosis.

194. 18F-MK-6240 Tau PET in Patients at Risk for Chronic Traumatic Encephalopathy

| Michael L. Alosco et al. | Molecular Neurodegeneration | 2025

Researchers tested a tau PET tracer in former NFL players and postmortem CTE tissue as part of continuing efforts to develop a reliable method for detecting CTE-related tau during life.

195. Measuring Head Impacts: Accelerometers and Other Sensors

| Multiple Authors | Handbook of Clinical Neurology | 2018

Reviews helmet sensors, instrumented mouthguards, accelerometers, and related technologies while emphasizing that measurement error and sensor placement must be considered when interpreting sports head-impact research.

Soccer: Lifetime Exposure and Neurodegeneration

196. Cognitive Effects of Heading in Professional Football: A Systematic Review

| Liam Patel, Julikram Tarafder and Flaminia Ronca | International Journal of Sports Medicine | 2025

Reviews the evidence linking professional soccer heading with cognitive outcomes and places recent heading restrictions for younger players in the context of continuing uncertainty about lifetime risk.

197. Heading Frequency and Risk of Cognitive Impairment in Retired Male Professional Soccer Players

| Multiple Authors | JAMA Network Open | 2023

Among hundreds of retired professional players, researchers investigated whether self-reported frequency of heading during matches and training was associated with later cognitive impairment.

198. Exposure Assessment for Repeated Sub-Concussive Head Impacts in Soccer: The HEADING Study

| Multiple Authors | Journal Article | 2023

Lifetime exposure estimates from former players indicated that defenders experienced the greatest repetitive-head-impact exposure and goalkeepers the least, reinforcing the importance of playing position.

199. Mixed Pathologies Including CTE Account for Dementia in Retired Soccer Players

| Helen Ling et al. | Acta Neuropathologica | 2017

Postmortem study of former soccer players with dementia found CTE-related pathology alongside other neurological diseases, demonstrating that later-life impairment often cannot be attributed to a single pathology.

200. Cortical Thinning in Former Professional Soccer Players

| Multiple Authors | Brain Imaging and Behavior | 2016

MRI research compared former professional soccer players with former non-contact athletes to investigate whether decades of repetitive soccer heading were associated with structural differences in the cerebral cortex.