Parkinson’s disease and colorectal cancer risk—A nested case control study

• Previous studies suggested a role for gut microbiota in the pathogenesis of both Parkinson’s disease and colorectal cancer (CRC).
• The current population representative study demonstrated an inverse association between Parkinson’s disease and CRC risk.
• There was no significant association with past antibiotic exposure, disease duration or Parkinson’s specific therapy.

BackgroundA pro-inflammatory gut microbiota was described in both Parkinson’s disease and colorectal cancer (CRC) and recently α-synuclein was demonstrated in the enteric nervous system. We sought to evaluate the association between Parkinson’s disease and CRC.MethodsWe conducted a nested case-control study using a large primary-care database. Cases were defined as all individuals with CRC. Up to 4 controls were matched with each case based on age, sex, practice-site and duration of follow-up. The primary exposure of interest was diagnosis of Parkinson’s disease prior to CRC as well as disease duration, and Parkinson’s specific therapies. The primary analysis was a conditional logistic-regression to estimate odds ratios (ORs) and 95% confidence interval (95%CI).ResultsThe study included 22,093 CRC cases and 85,833 matched controls. Past medical history of Parkinson’s disease >1 year before index-date was associated with lower CRC risk (OR 0.74, 95%CI 0.59–0.94). The inverse association was more prominent among females compared to males (0.64, 95%CI 0.42–0.96 and 0.8, 95%CI 0.60–1.07, respectively). While patients who received no therapy or therapy with dopamine agonists had a non-significant decrease in cancer risk, patients who were treated with dopamine had a non-significant elevated cancer risk.ConclusionParkinson’s disease is inversely associated with CRC risk.