Soccer, neurotrauma and amyotrophic lateral sclerosis: is there a connection?

Trauma has long been hypothesized but never proven to be a risk factor for amyotrophic lateral sclerosis (ALS). This hypothesis may now have a renaissance due to recent reports in the lay press on 'the Italian motoneuron mystery', i.e. the disclosure of 33 diagnosed ALS cases in a subpopulation of 24000 soccer players of the top three Italian divisions from the 1960s to 1996. Could the repetitive brain trauma that soccer players experience for controlling and advancing the ball with their heads represent an environmental risk factor for developing ALS in genetically predisposed individuals? By critically reviewing the scarce literature and 'surrounding evidence' (Medline, CDC, lay press, Italian health officials), we have looked for a potential relationship between (1) soccer and head trauma and (2) head trauma and subsequent development of amyotrophic lateral sclerosis. Whereas the brain traumatizing effect of soccer seems to be out of the question, the findings of the few retrospective studies on ALS and neurotrauma are conflicting. Taken together, however, the literature would still support the concept of soccer, head trauma, and ALS being interrelated, with high levels of athleticism/physical activity perhaps playing an additive part. To further clarify this issue, extensive prospective epidemiological investigations on ALS following neurotrauma as well as carefully designed animal studies will have to be conducted.