Association football (soccer) is the most popular sport in the world, and the growing recognition that playing soccer is associated with CTE has significant public health implications. However, the health benefits of playing sport are also recognised to reduce all cause mortality, particularly from cardiovascular causes. A public health policy limiting or restricting access to contact sports, which is not carefully considered, may therefore cause more harm than good. This retrospective case control study identified former professional footballers and compared mortality outcomes with a cohort of matched controls.
7,676 registered soccer players were recruited by searching the records of the Scottish football museum and professional soccer clubs for registered professionals. The records (name and date of birth) were then linked with the community health number (a health record number unique to each individual in Scotland) on a probabilistic basis. Former soccer players were matched to other individuals in the community health record by age, sex and deprivation index in a 1:3 ratio, resulting in a 23,028 strong control cohort. Outcomes were derived from death certificates (all-cause mortality; neurodegenerative disease; circulatory disease and respiratory disease). Prescribing data and deprivation indices were derived from national records. The analysis used cox-proportional hazard models, with a study endpoint of either mortality or December 2016.
Mortality in soccer players was lower until age 70, and increased thereafter (overall hazard ratio 0.87). Mortality from circulatory disease and respiratory disease was lower in soccer players compared with controls, but mortality from neurodegenerative disease was higher and this disparity persisted even when mortality for cardiovascular and respiratory cause was accounted for (hazard ratio 3.53). Players had a higher risk of dementia, motor neurone disease and Parkinson’s disease, and more frequent prescription of dementia related drugs than controls. In a subgroup analysis all-cause mortality and mortality secondary to neurodegenerative disease did not differ between outfield players and goalkeepers, but goalkeepers had fewer prescriptions for dementia related drugs than outfield players, consistent with known lower rates of traumatic brain injury (TBI) in goalkeepers.
Comment: Whilst this study is retrospective, the outcomes are based on death certificates and conclusions supported by prescribing records. The method for accounting for deprivation has some limitations as it is based on last known address, potentially missing historical deprivation. Furthermore the algorithm for linking soccer club records to health records is not described in the paper in detail and all the participants were male, limiting generalisability. However, even with these caveats, the evidence that repeated low level concussions increase the risk of neurodegenerative disease and physical activity reduces the risk of cardio-respiratory disease are biologically plausible and supported by multiple outcomes.
Mackay DF et al. NEJM. 2019; 381(19): 1801–8.