Football (soccer) players might be at increased risk of neurodegenerative disease, which has led to questions regarding the safety of the sport and recent measures introduced by football associations to reduce heading of the ball.
A Public Health report brought out by Lancet aimed to assess the risk of neurodegenerative disease among male football players in the Swedish top division Allsvenskan, compared with matched controls.
In this cohort study, The Lancet said that male football players who had played in the Swedish top division had a significantly increased risk of neurodegenerative disease compared with population controls. The risk increase was observed for Alzheimer’s disease and other dementias but not for other types of neurodegenerative disease, and among outfield players, but not among goalkeepers. Our study expands on the data that can be used to assess and manage risks in the sport.
The team from the Karolinska Institutet and other research centres published the study in the medical journal, The Lancet. It found 9% of the footballers included were diagnosed with neurodegenerative disease, compared with 6% (3,485 out of 56,168) of the control sample.
There was no significant risk increase for footballers of contracting motor neurone disease, according to the study. Study included 6,007 male football players who played in the Swedish top division between 1924 to 2019 suggests they were 1.5 times more likely to develop neurodegenerative disease compared to population controls.
Elite football players had increased risk of developing Alzheimer’s disease and other dementias, but their risk was not increased for motor neuron disease (including ALS), and their risk of Parkinson’s disease was lower compared to controls.
Unlike outfield players, goalkeepers did not have an increased risk of dementia – supporting the hypothesis that mild head impacts sustained when heading the ball could explain the increased risk in outfield players.
The overall evidence supports the hypothesis that former elite football players are at increased risk of neurodegenerative disease, especially Alzheimer’s disease and other dementias, and that the risk increase is limited to outfield players. However, the magnitude of the association might differ across populations of elite football players, including female players, and whether the findings are generalisable to contemporary football players is uncertain.
In 2019, a cohort study showed that former professional male football players in Scotland had more than 3·5 times higher risk of death with neurodegenerative disease, including Alzheimer’s disease, other types of dementias, motor neuron disease, and Parkinson’s disease, compared with general population controls. The large risk increase was observed for all types of neurogenerative disease, and ranged from a 2-fold increase for death with Parkinson’s disease to a 5-fold increase for death with Alzheimer’s disease.
Another study showed that the proportion of male professional football players in France who died from dementia was increased, although comparisons could only be made with the national average for men in the same age group, the number of outcome events was low, and Parkinson’s disease and amyotrophic lateral sclerosis could not be analysed due to few events.
Studies of amyotrophic lateral sclerosis in Italian and Spanish football players have also been published, although these studies had substantial limitations including the absence of a control group, or incomplete capture of outcome events.
Following the publication of the Scottish study, the Union of European Football Associations—UEFA—and the British football federations updated their guidelines to reduce exposure to heading among youth players. Limits for the number of headers that involve higher forces, such as those following a long pass or from corners kicks, were later introduced for adult amateur players and professional players in England.
The heightened concern regarding the safety of football has impacted practice guidelines for millions of players worldwide and brought the potential risk of neurodegenerative disease associated with the sport into broad public attention. Although it is established that physical activity and participation in sports have important health benefits, further studies of neurodegenerative disease among football players are needed to inform the management of risks in the sport.
The Lancet said that the researchers identified all male football players (amateurs and professionals) who had played at least one game in Allsvenskan from Aug 1, 1924 to Dec 31, 2019 and excluded players whose personal identity number could not be retrieved or be identified in the Total Population Register, and those who were not born in Sweden and who had immigrated to the country after age 15 years.
Football players were matched with up to ten controls from the general population according to sex, age, and region of residence. We used nationwide registers to compare the risk of neurodegenerative disease (diagnoses recorded in death certificates, during hospital admissions and outpatient visits, or use of prescription drugs for dementia) among football players versus controls. We also assessed each type of neurodegenerative disease (Alzheimer’s disease and other dementias, motor neuron disease, and Parkinson’s disease) separately, and compared the risk of neurodegenerative disease among outfield players versus goalkeepers.