Alcohol intake and risk of Parkinson's disease: a meta-analysis of observational studies.
BACKGROUND
The association of alcohol intake with risk of Parkinson's disease remains unclear.


METHODS
Pertinent studies were identified in PubMed and EMBASE. The fixed-effect or random-effect model was selected based on heterogeneity. The dose-response relationship was assessed by restricted cubic splines.


RESULTS
We included 32 articles, involving 677,550 subjects (9994 cases). The smoking-adjusted risk of Parkinson's disease for the highest versus lowest level of alcohol intake was relative risk (RR) 0.78 (95% confidence interval [CI], 0.67-0.92) overall, 0.86 (95% CI, 0.75-0.995) in prospective studies, and 0.74 (95% CI, 0.58-0.96) in matched case-control studies. A significant association was found with beer (0.59; 95% CI, 0.39-0.90) but not with wine and liquor, and for males (0.65; 95% CI, 0.47-0.90) after a sensitivity analysis but not for females. The risk of Parkinson's disease decreased by 5% (0.95; 95% CI, 0.89-1.02) for every 1 drink/day increment in alcohol intake in a linear (Pfor nonlinearity  = 0.85) dose-response manner.


CONCLUSIONS
Alcohol intake, especially beer, might be inversely associated with risk of Parkinson's disease