Association between Parkinson's Disease and Risk of Cancer: A PRISMA-compliant Meta-analysis

Previous studies exploring associations between Parkinson's disease (PD) and cancer risks provided controversial results. We conducted this study to examine the association between PD and cancer risks among different cancer types in worldwide populations. We searched for articles published before August 2019 in databases PubMed, Web of Science, EMBASE, Medline, and Google Scholar. The multivariate odds ratio (OR)/relative risk (RR) and 95% confidence intervals (CI) were computed to explore associations between PD and risks of different types of cancers. The present study indicated significantly negative associations between PD and risks of all types of cancers, digestive system cancers, lung cancers, and urinary system cancers. Additionally, no significant associations were shown between PD and risks of breast cancers, reproductive system cancers, or hematological malignancies. The study showed significantly positive associations between PD and risks of skin cancers and brain cancers. In conclusion, our investigation showed that PD patients showed reduced overall cancer risk and reduced risk of some types of cancers (digestive system cancers, lung cancers, and urinary system cancers). We need further studies to explore the underlying mechanism of the association between PD and cancers.