Colonoscopy and Subsequent Risk of Parkinson’s Disease

Background: Parkinson's disease (PD) is caused by the misfolding and aggregation of a-synuclein in neurons into toxic oligomers and fibrils that have prion-like properties allowing them to infect healthy neurons and to be transmitted to animal models of PD by injection or oral exposure. Given a-synuclein fibrils' potential transmission on the gut-brain axis, a-synuclein may be transmitted through colonoscopy procedures. Objective: This study examines a possible association between colonoscopy and PD. Methods: Longitudinal health insurance data of 250,000 individuals aged 50+ from 2004-2019 was analyzed. Cox proportional hazard and competing risk models with death as a competing event were estimated to calculate the risk of PD. Colonoscopy was categorized as never receiving colonoscopy, colorectal cancer (CRC) screening without or with biopsy, destruction or excision (BDE), and diagnostic colonoscopy without or with BDE. Results: We identified 6,422 new cases of PD among 221,582 individuals. The Cox model revealed a significantly increased risk of PD for patients who ever had a diagnostic colonoscopy without or with BDE (HR = 1.31; 95% CI: [1.23-1.40]; HR= 1.32 [1.22-1.42]) after adjustment for age and sex. After controlling for covariates and death, persons who ever underwentCRCscreening had a 40% reduced risk ofPD(CRHR = 0.60 [0.54-0.67]), while persons who underwent diagnostic colonoscopy had a 20% reduced risk of PD (CRHR = 0.81 [0.75-0.88]). Conclusions: Colonoscopy does not increase the risk of PD, after adjusting for death and covariates. Individuals who underwent only CRC screening had the lowest risk of PD, which may be a result of a more health-conscious lifestyle.