A landmark study1 of nearly 20,000 players has produced what researchers are calling the clearest population-level evidence to date linking professional football to neurodegenerative disease, and the implications reach far beyond professional football.
The study, conducted by researchers at Mass General Brigham, Boston University, and the Concussion & CTE Foundation, found that NFL players are nearly four times more likely to die from neurodegenerative disease than the general population. That includes dementia and Parkinson’s disease, two conditions that affect tens of millions of people worldwide and for which age is typically the primary risk factor. These findings strengthen a growing body of evidence suggesting that repeated head impacts sustained over years of play contribute to long-term brain health risks.
Here’s what you need to know (especially parents who are worried about their kids playing contact sports football, soccer, hockey, or rugby).
About the study
Researchers analyzed health records from 19,824 NFL players who competed between 1960 and 2019, making this the largest retrospective cohort study of its kind. They compared player mortality rates across every official cause of death against national rates for the general population.
NFL players had lower overall mortality than the general population, which was unsurprising due to their lifelong commitment to fitness. But the data revealed NFL players were nearly four times more likely to die from neurodegenerative disease. Even after accounting for other known risk factors, neurodegenerative mortality was still three times higher for players compared to the general population.
The study broke down the findings by disease:
Dementia: NFL players died from dementia at 3.8 times the rate of the general population
Parkinson’s disease: NFL players died from Parkinson’s at 3.88 times the rate of the general population
Younger players: Those who died before age 60 had more than 12 times the neurodegenerative death rate of the general population
Career length: Players with five or more seasons had nearly double the risk of neurodegenerative death compared to those who played one to four seasons
That last finding is particularly significant. It points to a dose-response relationship, meaning the more football a player plays, the higher the risk. This pattern mirrors what researchers have found in studies of CTE (chronic traumatic encephalopathy), a degenerative brain disease linked to repeated head trauma.
Why the 4x number may actually understate the risk
NFL players, as a group, are exceptionally healthy. They have lower rates of cancer, cardiovascular disease, and suicide compared to the general population. The study introduces a concept called the STARS effect—Selection Through Athletic Resilience Survivor—to explain this. The same traits that enable someone to become a professional athlete, including physical resilience, discipline, lower rates of early illness, and better access to medical care, also tend to support longer overall survival.
In other words, NFL players would be expected to have lower rates of brain disease than the average person, not higher ones. The fact that they have dramatically elevated rates instead suggests the true relationship between playing football and neurodegenerative disease may be even stronger than the fourfold increase implies.
The study noted that neurodegenerative deaths were actually highest among players who tend to have the fewest other health conditions. Linemen, who generally have higher body weight and related health issues like sleep apnea, had half the dementia mortality compared to non-linemen. This further emphasizes that the brain disease risk seen in football players is not explained by general poor health.
What contact sports do to the brain
The NFL study is the largest of its kind, but it’s far from the first evidence linking contact sports to brain diseases.
Researchers have identified CTE in athletes across a wide range of sports, including boxing, soccer, rugby, ice hockey, and wrestling. Over 97% of CTE cases have been found in individuals with known exposure to repeated head impacts, and there is a robust dose-response relationship between CTE and years of football play.
A separate 2023 case series2 found CTE in 41% of deceased contact sport athletes under the age of 30, the majority of whom played American football, ice hockey, soccer, rugby, and wrestling. And this isn’t the only sign that the damage may begin earlier than previously understood.
How to reduce the risk for people playing contact sports
This research doesn’t mean every child who plays football or soccer is destined for cognitive complications. But it does mean that the number and severity of head impacts a young athlete accumulates over their playing career matters. Research shows that subconcussive hits (impacts that don’t cause noticeable symptoms) may still affect brain health over time. The cumulative load is what researchers believe drives long-term risk, not any single blow.
Parents, coaches, and leagues all have a role in reducing that exposure. Here are some practical things that can be done to reduce risk of brain damage:
Limit full-contact practice time: Research shows that subconcussive hits (impacts that don’t cause noticeable symptoms) may still affect brain health over time. The cumulative load is what researchers believe drives long-term risk, not any single blow. Leagues and schools that have capped full-contact practice sessions have seen reductions in head impact exposure. Advocate for these policies if they’re not already in place.
Prioritize technique: roper form, especially in tackling and blocking, reduces the frequency and severity of head impacts. Look for programs and coaches who emphasize technique-based training.
Take concussions seriously: A concussed brain is more vulnerable to a second impact before it has fully healed. Never push for a same-day return to play after a suspected concussion. Symptoms should fully resolve before an athlete returns to contact, with medical clearance from a qualified provider.
Consider the sport and position: Some sports and positions carry higher head impact exposure than others. This doesn’t mean you have to avoid contact sports altogether, but it’s worth factoring into decisions about participation and position.
Stay informed. The science on CTE and repetitive head impacts is still evolving. Organizations like the Concussion & CTE Foundation and the CDC’s Heads Up program4 offer updated guidance for parents, coaches, and athletes.
The takeaway
This study shows, with more data than ever before, that playing in the NFL significantly raises the risk of dying from dementia or Parkinson’s disease. And the more seasons a player competes, the higher that risk climbs.
The evidence connecting contact sports to brain disease has been building for years, across multiple sports and multiple countries. This study adds the strongest population-level data yet to that body of work. Sports are a great physical and mental outlet for kids and adults alike. Contact sports come with a unique risk. Whether you’re a player, parent, or coach, having protocols in place (i.e. limited contact practices, practicing with the right equipment, etc.) is crucial for protecting brain health.
