Parkinson's disease and cancer: a systematic review and meta-analysis of over 17 million participants.

Research overview

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ObjectiveTo systematically review and qualitatively evaluate epidemiological evidence on associations between Parkinson's disease (PD) and cancer via meta-analysis.Data sourcesMEDLINE via PubMed, Web of Science and EMBASE, until March 2021.Study selectionIncluded were publications that (1) were original epidemiological studies on PD and cancer; (2) reported risk estimates; (3) were in English. Exclusion criteria included: (1) review/comments; (2) biological studies; (3) case report/autopsy studies; (4) irrelevant exposure/outcome; (5) treated cases; (6) no measure of risk estimates; (7) no confidence intervals/exact p values and (8) duplicates.Data extraction and synthesisPRISMA and MOOSE guidelines were followed in data extraction. Two-step screening was performed by two authors blinded to each other. A random-effects model was used to calculate pooled relative risk (RR).Main outcomes and measuresWe included publications that assessed the risk of PD in individuals with vs without cancer and the risk of cancer in individuals with vs without PD.ResultsA total of 63 studies and 17 994 584 participants were included. Meta-analysis generated a pooled RR of 0.82 (n=33; 95% CI 0.76 to 0.88; pConclusionsPD and total cancer were inversely associated. This inverse association persisted for both smoking-related and non-smoking-related cancers. PD was positively associated with melanoma. These results provide evidence for further investigations for possible mechanistic associations between PD and cancer.Prospero registration numberCRD42020162103.

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