Colonoscopy does not increase the risk of Parkinson’s disease

Abstract Parkinson's disease (PD) is caused by the misfolding and aggregation of α-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. Considering that α-synuclein fibrils can also propagate from the enteric to the central nervous system, α-synuclein may be transmitted through colonoscopy procedures. This study examines a possible association between colonoscopy and PD. We used longitudinal data of 250,000 individuals aged 50+ from 2004-2019 from Germany's largest health insurer. Cox proportional hazard and competing risk models with death as a competing event were estimated to calculate the risk of PD. Models were adjusted for age, sex, reason for colonoscopy and co-morbidities of PD. Colonoscopy was categorized as never receiving colonoscopy, colorectal cancer (CRC) screening without or with biopsy, destruction, excision, laser vaporization or argon plasma coagulation (BDE), and diagnostic colonoscopy without or with BDE. 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% confidence interval: [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 underwent CRC screening had a 40% reduced risk of PD (HR=0.60 [0.53-0.66]), while persons who underwent diagnostic colonoscopy had a 20% reduced risk of PD (HR=0.80 [0.74-0.87]). Individuals who ever had any type of colonoscopy had a lower risk of PD compared to those who never had a colonoscopy, 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.