Meta-analysis for epidemiologic studies on the relationship between smoking and Parkinson's disease.

Many epidemiologic studies on the relationship between smoking and Parkinson's disease (PD) have been conducted. Morens et al. reviewed many articles in the study field and concluded that smoking is inversely associated with the risk of PD. In the present study, the object is to obtain summarized risk estimates of the relationship from the published articles using meta-analysis. Summarized risk estimates on the relationship between smoking and PD were found to be about 0.5 with statistical significance in meta-analysis. Therefore, the result that smoking is inversely associated with the risk of PD is appropriate.