Residential green and blue space associated with lower risk of adult-onset inflammatory bowel disease: Findings from a large prospective cohort study

Background: We investigated the associations between residential green space and blue space (water) and inflammatory bowel disease (IBD) incidence, which have rarely been examined. Methods: We performed a longitudinal analysis using data of the UK Biobank study, a large prospective cohort. Incident cases of IBD were ascertained through linkage to health administrative datasets. Residential green space, blue space and natural environment (land coverage percentage) were estimated using land use data. Cox proportional hazard regression models were used to determine the associations between the exposures and IBD incidence with adjustment for a wide array of potential confounders. Results: A total of 216,868 participants without IBD at baseline were studied with an average follow-up of 11.7 years, contributing to 2.5 million person-years. During the follow-up, 1271 incident IBD cases were identified. In fully adjusted models, participants with green space coverage at 300 m buffer in the 2nd and 3rd tertiles had 18.2% [HR = 0.818, 95% confidence interval (CI): 0.715, 0.936] and 15.4% (HR = 0.846, 95%CI: 0.736, 0.972) lower risks of incident IBD compared with those in the 1st tertile, respectively. Similar results were found for blue space [HR = 0.858 (95%CI: 0.750, 0.982) for 2nd vs 1st tertile; HR = 0.785 (95%CI: 0.685, 0.899) for 3rd vs 1st tertile]. Negative associations were also observed for natural environment. Stronger associations were observed in participants from more deprived areas. Conclusions: Our study suggests that residential green space, blue space and natural environment might be protective factors against IBD.