Physical activity as a risk factor for amyotrophic lateral sclerosis-findings from three large European cohorts

There has been a longstanding historic interest in a possible link between amyotrophic lateral sclerosis (ALS) and levels of physical activity, fuelled by high profile athletes intermittently acquiring the disease and raising its profile. Putative mechanisms behind this hypothesis remain unclear but have implicated; oxidative stress, glutamate excitotoxicity, glial activation, anti-apoptotic proteins, neurotrophic factors, and exercise-induced changes in neuron morphology. Previous small observational studies of athletes have suggested certain groups of athletes (including soccer or American football players) may have an increased risk of ALS. More recently, larger scale studies have explored the association of ALS with physical activity in general. The methodology underpinning these studies has been mixed, and the strengths and directions of association have thus far been inconsistent. In this month’s journal club we discuss two recent papers examining links between current and historical physical activity and ALS incidence and mortality in general populations. We also examine a large-scale paper comparing how ALS risk might potentially vary with level of athletic attainment in a selective group of skiers