To explore the association with cigarette smoking for Parkinson's disease (PD).
One hundred and fourteen PD cases and 205 controls matched on gender and race were recruited from ongoing PD prevalence survey and identified at the neurological clinic of Peking Union Medical College Hospital. Face to face questionnaire interview was carried out and data on smoking and alcohol consumption were analyzed in a population-based case control study.
With never-smokers as the reference category, we observed reduced risk for PD among ever smokers (OR = 0.49, 95% CI: 0.30 - 0.79) current smokers (OR = 0.44, 95% CI: 0.23 - 0.86) and ex-smokers (OR = 0.54, 95% CI: 0.30 - 0.96). When comparing with non-smokers, the ever smokers stratified by years of smoking had an inverse association with those whose smoking history longer than 20 years (OR = 0.35, 95% CI: 0.18 - 0.70) and an mild protective association with those who smoked less than 20 years (OR = 0.61, 95% CI: 0.35 - 1.07). Those who had quitted smoking for more than 20 years were less likely to have the disease than never smokers, and those who had quitted for less than 20 years were least likely to have PD. Those current smokers were still least likely to have the disease. Significant inverse gradient with pack-day smoker (trend P < 0.05), and the inverse association for cigarette smoking and PD were found not bing confounded by alcohol consumption.
The inverse association between PD and cigarette smoking and history of cessation was found. Further studies need to provide biochemical evidence on the relation between smoking and its protective effect on PD.