Objectives: Amyotrophic lateral sclerosis (ALS) has been reported to occur with increased incidence amongst physically active people. The role of extrinsic risk factors as physical activity, head trauma and drug/pesticide-exposure in the pathophysiology of ALS and especially in the context of practising sports remains controversial.
Materials and methods: We retrospectively studied exposure to extrinsic factors in 92 ALS patients in the presymptomatic stage. Metabolic equivalents (METs) were calculated and the association of physical activity, drug intake, head trauma and participation in specific sports (football [soccer], ice hockey) with age at symptom-onset was evaluated.
Results: Ninety-five percent of patients considered themselves physically active before symptom-onset. Total MET-values varied broadly and there was no correlation between vigorous physical activity and age at symptom-onset. Mild traumatic brain injury (prevalence = 16.7%) was the most frequent diagnosis after head/neck injury. A history of ≥1 head/neck injuries was associated with a younger age at symptom-onset (61.8 ± 11.0 vs. 54.1 ± 13.0, p = .013). In former football and ice hockey players the rate of vigorous physical activities was increased (p < .05), whereas total MET-values, frequency of head injuries and analgesic intake were not different compared to other ALS patients.
Conclusions: History of head injuries was the only extrinsic risk factor associated with accelerated neurodegeneration in ALS. There was no evidence for extrinsic factors predisposing former football and ice hockey players to ALS. Our data therefore support the hypothesis that not increased physical activity per se, but other unknown environmental factors and/or genetic profile or lifestyle-promoting physical fitness increases ALS susceptibility.
Keywords: amyotrophic lateral sclerosis; football (soccer); head trauma; ice hockey; physical activity.