A new study of nearly 20,000 former National Football League players provides what researchers describe as the clearest population-level evidence linking professional football to neurodegenerative disease. The findings have implications that extend beyond professional sports.
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 a neurodegenerative disease, such as dementia and Parkinson’s disease, compared to the general population. Age is typically the primary risk factor for these conditions, which affect tens of millions of people worldwide.
Researchers analyzed health records from 19,824 NFL players who competed between 1960 and 2019. This is the largest retrospective cohort study of its kind. They compared player mortality rates across all official causes of death against national rates for the general population.
NFL players had lower overall mortality than the general population, which researchers attributed to their lifelong commitment to fitness. However, the data showed they 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.
The study broke down the findings by disease. NFL players died from dementia at 3.8 times the rate of the general population. They died from Parkinson’s disease at 3.88 times the rate. Players who died before age 60 had more than 12 times the neurodegenerative death rate. Players with five or more seasons had nearly double the risk of neurodegenerative death compared to those who played one to four seasons.
This last finding 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 chronic traumatic encephalopathy (CTE), a degenerative brain disease linked to repeated head trauma.
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, or Selection Through Athletic Resilience Survivor, to explain this. The same traits that enable someone to become a professional athlete, including physical resilience and better access to medical care, also tend to support longer overall survival.
Because NFL players would be expected to have lower rates of brain disease than the average person, the fact that they have dramatically elevated rates suggests the true relationship may be even stronger than the fourfold increase implies. The study noted that neurodegenerative deaths were highest among players who tend to have the fewest other health conditions. Linemen, who generally have higher body weight and related health issues, had half the dementia mortality compared to non-linemen.
This NFL study is the largest of its kind, but it is not 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.
A separate 2023 case series found CTE in 41% of deceased contact sport athletes under the age of 30. The majority played American football, ice hockey, soccer, rugby, and wrestling. A 2025 study found that repeated head trauma causes brain cell loss and inflammation in young athletes before the hallmark changes of CTE even appear, suggesting the injury process starts well before any diagnosis is possible.
This research does not mean every child who plays football or soccer will have 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 do not cause noticeable symptoms, may still affect brain health over time. The cumulative load is what researchers believe drives long-term risk.
Leagues and schools that have capped full-contact practice sessions have seen reductions in head impact exposure. Proper form in tackling and blocking reduces the frequency and severity of head impacts. A concussed brain is more vulnerable to a second impact before it has fully healed. Symptoms should fully resolve before an athlete returns to contact, with medical clearance from a qualified provider. Some sports and positions carry higher head impact exposure than others.
The science on CTE and repetitive head impacts is still evolving. 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.
