Tea consumption and risk of Parkinson's disease: A meta-analysis

The results of studies on the association between tea consumption and Parkinson's disease (PD) have been inconsistent. Therefore, the aim of this study was to perform an updated meta-analysis to better resolve any association between tea consumption and PD. We searched PubMed, Embase, and the Cochrane Library - from their commencement to November 2016 - for qualified studies that evaluated the associations between tea drinking and risk of PD. A total of nine case-control studies and three prospective cohort studies were included. The meta-analysis showed that tea consumption was associated with a reduced risk of developing PD(OR, 0.82; 95% CI, 0.69-0.98) when case-control studies and prospective cohort trials were considered together. Subgroup analysis on the category of tea consumption and risk of PD showed that black tea was not associated with PD (OR: 0.89; 95% CI, 0.64-1.24; I-2=0.0%), but other kinds of tea was associated with a reduced risk of developing PD (OR: 0.67; 95% CI, 0.48-0.95; I-2=0.0%). Subgroup analysis on the dose of tea consumption and PD risk showed that drinking more than one cup of tea daily was associated with a reduced risk of developing PD in case-control studies (OR: 0.38; 95% CI, 0.22-0.66; I-2=0.0%). No indication of publication bias was found. In conclusion, the current evidence showed that tea consumption was associated with a reduced risk of developing PD. The results of our subgroup analysis suggested that people who drinking more than one cup of non-black tea daily might have a reduced risk of developing PD.