Risk of amyotrophic lateral sclerosis and history of physical activity: a population-based case-control study.

OBJECTIVE: To assess in greater detail than previous studies the purported association between a history of physical activity and amyotrophic lateral sclerosis (ALS).
METHODS: A population-based case-control study was used to identify risk factors for ALS. Case patients were from 3 counties of western Washington State who were newly diagnosed as having ALS by a neurologist. Two control subjects matched with each case patient for sex and age within 5 years were identified by random digit telephone dialing or random selection from Medicare eligibility lists. All subjects underwent an in-person structured interview including detailed information about physical activity before a reference date, which was the month and year the case patient was diagnosed as having ALS. Various measures of physical activity both at work and leisure time were evaluated using conditional logistic regression taking into account the matching for sex and age.
RESULTS: One hundred seventy-four case patients and 348 control subjects participated in the study. Physical activity was not significantly different between case patients and controls--whether at work, leisure time or both combined, and whether during a person's lifetime (from 10 years before reference date back to age 15 years) or during specific decades before reference date. An exception was that case patients reported having participated in organized sports in high school slightly more frequently than control subjects (odds ratio, 1.52; 95% confidence interval, 1.03-2.25).
CONCLUSION: A history of physical activity has little, if any, effect on the risk of ALS.