Amirhossein Ashnaei - Department of Modern Sciences and Technologies, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
Zahra Farjami - Department of Modern Sciences and Technologies, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
Neshat Ebrahimi - Laboratory of Cedars-Sinai Medical Center, Los Angles, California, USA
Negar Khodaeinia - National Research Center of Genetic Engineering and Biotechnology (NIGEB), Department of Medical Genetics, Tehran, Iran

According to the recent studies, many scientists indicated the inverse relation between caffeine consumption and the risk of Parkinson’s disease (PD). Though, heterogeneity consequences between studies impede a precise estimation of this association. We conducted a systematic review and meta-analysis of epidemiological investigations to estimate the effect of caffeine exposure on PD. Systematic search of Embase, PubMed, Science Direct and Google Scholar databases was done between 2015-2018 with the terms of Parkinson’s disease AND Caffeine . We included Cohort, case-control and cross-sectional studies. Data extraction was done using a standardized data extraction tool in Microsoft Office Excel 2013. Heterogeneity was quantified using the I2 statistic. Of 20 articles, 15 ones had the qualitative criteria for inclusion in our study. The summary RR for 8 cohort studies indicated the relation of caffeine consumption and PD was 0.65 (95% CI, 0.58– 0.72], with moderate heterogeneity (I2= 27.3%). For 4 case-control studies, the RR was 0.73 (95%CI: 0.65–80; I2=6.5%), and for 3 cross-sectional studies, the RR was 0.66 (95%CI: 0.59–0.80; I2= 45.6%). Conclusion: This study confirms an inverse relation between caffeineconsumption and the risk of incidence with PD.