Population-based case-control study of amyotrophic lateral sclerosis in western Washington State. I. Cigarette smoking and alcohol consumption.

The associations of cigarette smoking and alcohol consumption with the risk of amyotrophic lateral sclerosis (ALS) were investigated in a population-based case-control study conducted in three counties of western Washington State from 1990 to 1994. Incident ALS cases (n = 161) were identified and were matched to population controls (n = 321) identified through random digit dialing and Medicare enrollment files. Conditional logistic regression analysis was used to compute odds ratios adjusted for age, gender, respondent type, and education. The authors found that alcohol consumption was not associated with the risk of ALS. Ever having smoked cigarettes was associated with a twofold increase in risk (alcohol-adjusted odds ratio (OR) = 2.0, 95% confidence interval (CI): 1.3, 3.2). A greater than threefold increased risk was observed for current smokers (alcohol-adjusted OR = 3.5, 95% CI: 1.9, 6.4), with only a modestly increased risk for former smokers (alcohol-adjusted OR = 1.5, 95% CI: 0.9, 2.4). Significant trends in the risk of ALS were observed with duration of smoking (p for trend = 0.001) and number of cigarette pack-years (p for trend = 0.001). The finding that cigarette smoking is a risk factor for ALS is consistent with current etiologic theories that implicate environmental chemicals and oxidative stress in the pathogenesis of ALS.