No Evidence for a Causal Relationship Between Cancers and Parkinson's Disease

Background: Epidemiological data suggest that cancer patients have a reduced risk of subsequent Parkinson's disease (PD) development, but the prevalence of PD in melanoma patients is often reported to be increased. Causal relationships between cancers and PD have not been fully explored. Objective: To study causal relationship between different cancers and PD. Methods: We used GWAS summary statistics of 15 different types of cancers and two-sample Mendelian randomization to study the causal relationship with PD. Results: There was no evidence to support a causal relationship between the studied cancers and PD. We also performed reverse analyses between PD and cancers with available full summary statistics (melanoma, breast, prostate, endometrial and keratinocyte cancers) and did not find evidence of causal relationship. Conclusion: We found no evidence to support a causal relationship between cancers and PD and the previously reported associations could be a result of genetic pleiotropy, shared biology or biases.