Could Regular Exercise Cause ALS?

The viral popularity of the “ALS Ice Bucket Challenge,” in which people are challenged to either donate money to the Amyotrophic Lateral Sclerosis Foundation or to dump a bucket of ice water over their heads on video, has brought awareness of the neurodegenerative disease into the spotlight.  It has also reinvigorated a long-held debate over the possible link between contact sports, physical exercise, and the risk of ALS.  

In the past, healthcare professionals and the public have connected ALS to athletics, due in part to the disease’s association with Yankees first baseman Lou Gehrig, and to several Italian studies linking the disease to professional soccer players. While the data suggested that high amounts of regular exercise or participation in contact sports could increase the risk of ALS, larger, more in-depth studies were needed to better clarify the results.
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Recently, 2 new studies were published examining this association:

In the first study, investigators interviewed 652 participants with ALS to learn about their exercise and sports histories (professional and amateur), jobs, leisure activities, and history of head injuries, including concussions.¹

The ALS participants were then compared to data taken from 1166 participants without the disease.

The study’s results showed that not only does exercise not heighten risk of ALS manifestation, exercise may, in fact, protect against the onset of symptoms.

“Overall physical activity was associated with reduced odds of having ALS, as were work-related physical activity and organized sports. An inverse correlation was observed between ALS, the duration of physical activity, and the cumulative [metabolic equivalents] scores,” researchers wrote.  

Investigators noted that those with a history of head injuries (2 concussion or more) were more likely to develop ALS compared to individuals without multiple head traumas.

The second analysis pulled together 50 years of data, including the first study, from a pool of epidemiological studies related to risk of ALS and how it is associated with physical activity.²

While the meta-analysis showed that physical activity is not a direct cause of ALS, researchers cautioned that because the pool of studies was associational, they were unable to establish causal relationships.  Therefore, ALS and exercise may, in fact, be associated with other factors like healthy diet, and not associated with one another

The studies are published in the May issue of Annals of Neurology and the July issue of the European Journal of Epidemiology.

-Michelle Canales

References:

Pupillo E, Messina P, Giussani G, et al. Physical activity and amyotrophic lateral sclerosis: a European population-based case-control study. Ann Neurol. 2014 May [epub ahead of print] doi: 10.1002/ana.24150.

Hamidou B, Couratier P, Besancon C, et al. Epidemiological evidence that physical activity is not a risk factor for ALS. Eur J Epidemiol. 2014 July [epub ahead of print] doi: 10.1007/s10654-014-9923-2.