Statin use and risk of Parkinson's disease: a meta-analysis of observational studies.

Inconsistent results regarding the association between statin use and risk of Parkinson's disease (PD) have been reported. We therefore examined the association between statin use and risk of PD by conducting a detailed meta-analysis of all observational studies published regarding this subject. A literature search in the PubMed database was undertaken through April 2012, looking for observational studies evaluating the association between statin use and risk of PD. Combined relative risk (RR) estimates and 95 % confidence intervals (CIs) were calculated using a random-effects model. Subgroup and sensitivity analyses were also performed. A total of eight (five case-control and three cohort) studies contributed to the analysis. There was heterogeneity and publication bias among the studies. Statin use significantly reduced the risk of PD by 23 % (RR 0.77, 95 % CI 0.64-0.92, p = 0.005). However, long-term statin use did not significantly affect the risk of PD (RR 0.72, 95 % CI 0.45-1.13, p = 0.15). Stratification of studies by age and smoking status significantly affected the final estimate (age-adjusted RR 0.61, 95 % CI 0.42-0.86, p = 0.005; age-not-adjusted RR 0.93, 95 % CI 0.83-1.05, p = 0.23 and smoking-adjusted RR 0.60, 95 % CI 0.42-0.87, p = 0.007; smoking-not-adjusted RR 0.92, 95 % CI 0.82-1.02, p = 0.10). Furthermore, sensitivity analysis confirmed the stability of results. Our meta-analysis supports the hypothesis that statin use reduced the risk of PD. Nevertheless, more randomized clinical trials and observational studies are required to confirm this association with underlying biological mechanisms in the future.