To determine whether professional soccer players are at increased risk of amyotrophic lateral sclerosis (ALS).

Since the observation of several deaths from ALS among Italian professional soccer players, an association between ALS and soccer has been postulated. Repeated injuries, mostly in the head, are reported more frequently by ALS patients than the general population. An association between exercise and ALS has also been suggested, but results are conflicting. Clinical and experimental observations suggest an association between ALS and use of non-steroidal anti-inflammatory agents and dietary supplements, including branched-chain amino acids.

All professional soccer players who practiced in the period 1959-2000 were identified through the archives of the Panini soccer cards, the major Italian football cards publisher. These individuals represent the exposed cohort. For each player, date and place of birth, playing role and team history were recorded. Each player was followed since the year of start of professional activity. Incident ALS cases among the exposed were all soccer players firstly diagnosed with ALS during the period 1959-2016. Expected incidence rate was the number of cases/100,000 person-years expected in the cohort using a well-defined Italian population for reference. Standardized incidence ratio (SIR) was the ratio between observed and expected incidence rate.

33 individuals in the cohort developed ALS. The number of expected cases was 17.6. The SIR was 1.9 (95% CI 1.3-2.6) in the entire sample and 4.7 (95% CI 2.7-7.5) in subjects aged less than 45 years at diagnosis. The median age at diagnosis was 43.3 yr. Compared to the median age of onset of ALS in the general population (62.5 yr; range 56.0-72.2 yr), the disease in former soccer players occurred 21.9 years earlier.

Soccer players are at higher risk of developing ALS than the general population. The disease develops at an earlier than expected age.