Parkinson's disease risks associated with cigarette smoking, alcohol consumption, and caffeine intake

A reduced risk for Parkinson's disease (PD) among cigarette smokers has been observed consistently during the past 30 years. Recent evidence suggests that caffeine may also be protective. Findings are presented regarding associations of PD with smoking, caffeine intake, and alcohol consumption from a case-control study conducted in western Washington State in 1992-2000. Incident PD cases (n = 210) and controls (n = 347), frequency matched on gender and age were identified from enrollees of the Group Health Cooperative health maintenance organization. Exposure data were obtained by in-person questionnaires. Ever having smoked cigarettes was associated with a reduced risk of PD (odds ratio (OR) = 0.5, 95% confidence interval (CI): 0.4, 0.8). A stronger relation was found among current smokers (OR = 0.3, 95% CI: 0.1, 0.7) than among ex-smokers (OR = 0.6, 95% CI: 0.4, 0.9), and there was an inverse gradient with pack-years smoked (trend p < 0.001). No associations were detected for coffee consumption or total caffeine intake or for alcohol consumption. However, reduced risks were observed for consumption of 2 cups/day or more of tea (OR = 0.4, 95% CI: 0.2, 0.9) and two or more cola drinks/day (OR = 0.6, 95% CI: 0.3, 1.4). The associations for tea and cola drinks were not confounded by smoking or coffee consumption.