Elite male footballers were 1.5 times more likely to develop neurodegenerative disease compared to population controls, according to an observational study published in The Lancet Public Health journal.
Among male footballers playing in the Swedish top division, 9% (537 out of 6,007) were diagnosed with neurodegenerative disease, compared to 6% (3,485 out of 56,168) population controls.
The football players were both amateur and professional. Sweden was a prominent football nation during the 20th century and many of the players from the top division were competing at the highest international level. However, due to ideals of sportsmanship and amateurism, football clubs in Sweden were not allowed to pay salaries to their football players until the late 1960s.
In recent years, there have been growing concerns about exposure to head trauma in football (soccer) and whether it can lead to increased risk of neurodegenerative disease later in life. A previous study from Scotland suggested that footballers were 3.5 times more likely to develop neurodegenerative disease.  Following this evidence, certain footballing associations implemented measures to reduce heading in younger age groups and training settings. 
Peter Ueda, assistant professor at Karolinska Institutet, Sweden, says, “While the risk increase in our study is slightly smaller than in the previous study from Scotland, it confirms that elite footballers have a greater risk of neurogenerative disease later in life. As there are growing calls from within the sport for greater measures to protect brain health, our study adds to the limited evidence-base and can be used to guide decisions on how to manage these risks.” 
The study used Sweden’s national health registers to look for records of neurodegenerative disease (diagnoses, deaths, or use of prescription drugs for dementia) in 6,007 male football players who had played in the Swedish top division from 1924 to 2019. It compared players’ risk of neurodegenerative disease with population controls, who were people matched with football players according to sex, age, and region of residence . The analysis broke down the risk for different neurogenerative conditions, including Alzheimer’s and other dementias, motor neuron disease, and Parkinson’s disease. It also compared the risks between outfield players and goalkeepers.
Overall, football players had a 1.5 times increased risk of neurogenerative disease compared to controls. 9% (537 out of 6,007) of football players compared to 6% (3485 out of 56,168) of controls were diagnosed with neurodegenerative disease.
The authors caution that although 9% of football players and 6% of controls were diagnosed with neurodegenerative disease during their study, most participants were still alive at the end of data collection, so the lifetime risk of developing neurodegenerative disease for both groups are likely to be higher.
The risk of neurodegenerative disease was 1.5 times higher for outfield players compared to controls but was not significantly higher for goalkeepers compared to controls. Accordingly, in a direct comparison, outfield players had a 1.4 times higher risk of neurodegenerative disease compared to goalkeepers. See table 3 for more details comparing outcomes among outfield players, goalkeepers, and population controls.
Peter Ueda adds, “Importantly, our findings suggest that goalkeepers don’t have the same increased risk of neurodegenerative disease as outfield players. Goalkeepers rarely head the ball, unlike outfield players, but are exposed to similar environments and lifestyles during their football careers and perhaps also after retirement. It has been hypothesised that repetitive mild head trauma sustained through heading the ball is the reason football players are at increased risk, and it could be that the difference in neurodegenerative disease risk between these two types of players supports this theory.” 
Football players had a 1.6 increased risk of Alzheimer’s disease and other dementias compared to controls – with 8% (491 out of 6,007) of footballers being diagnosed with the condition compared to 5% (2889 out of 56,168) of controls.
There was no significant risk increase for football players versus controls observed for motor neuron disease, which includes ALS. The risk of Parkinson’s disease was lower among football players (See Table 2 for more details). Overall mortality was slightly lower among footballers compared to the control group (40% versus 42%).
Björn Pasternak, senior researcher at Karolinska Institutet says, “The lower overall mortality we observed among footballers indicates that their overall health was better than the general population, likely because of maintaining good physical fitness from frequently playing football. Physical activity is associated with a lower risk of dementia, so it could be hypothesized that the potential risks from head impacts are being somewhat offset by having good physical fitness. Good physical fitness may also be the reason behind the lower risk of Parkinson’s disease.”
The authors discuss some limitations of their study. The findings’ generalisability to footballers playing today is uncertain. As neurodegenerative disease usually occurs later in life, most players in the study who were old enough to have developed one of these conditions played elite football during the mid-20th century. Since then, football has changed in many ways that may impact the risk of neurodegenerative disease. It may be that switching from leather to synthetic balls (that do not soak up water and become heavier), having more rigorous training and better equipment, or switching towards a playstyle associated with less head trauma may have reduced the risk. On the other hand, the risk might be higher among footballers who nowadays train and play more intensely from a young age. The study also looked at male elite footballers only, so the study’s generalisability to female elite players and to male and female amateur and youth players is uncertain.