Inflammatory bowel disease (IBD) is associated with a lower risk of developing Parkinson disease (PD), according to a recent study. Using a case-control design, researchers identified 89,790 newly diagnosed PD cases and 118,095 population-based controls aged >65 years using comprehensive Medicare data from 2004-2009 including detailed claims data. They classified IBD using International Classification of Diseases version 9 (ICD-9) diagnosis codes and used logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs) to evaluate the association between PD and IBD. They found:

• PD was inversely associated with IBD overall and with both Crohn's disease and ulcerative colitis.
• Potential indicators of disease severity were inversely associated with PD.