Ambient Air Pollution and Risk of Enterotomy, Gastrointestinal Cancer, and All-Cause Mortality among 4,708 Individuals with Inflammatory Bowel Disease: A Prospective Cohort Study

BACKGROUND: Previous studies indicated that air pollution plausibly increases the risk of adverse outcomes in inflammatory bowel disease (IBD) via proinflammatory mechanisms. However, there is scant epidemiological data and insufficient prospective evidence assessing associations between ambient air pollution and clinical outcomes of IBD. OBJECTIVES: We aimed to investigate the associations between ambient air pollution and clinical outcomes among individuals with IBD. METHODS: Leveraging data from the UK Biobank, we included 4,708 individuals with IBD recruited in the period 2006-2010 in this study. A land use regression model was used to assess annual mean concentrations of ambient air pollutants nitrogen including oxides (NOx), nitrogen dioxide (NO2), and particulate matter (PM) with aerodynamic diameter <10 lm (PM10) and PM with aerodynamic diameter <2.5 lm (PM2.5). Individuals with IBD were followed up for incident clinical outcomes of enterotomy, gastrointestinal cancer, and all-cause mortality, ascertained via death registry, inpatient, primary care, and cancer registry data. Cox proportional hazard model was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for the magnitude of the associations. RESULTS: During a mean follow-up of 12.0 y, 265 enterotomy events, 124 incident gastrointestinal cancer, and 420 death events were documented among individuals with IBD. We found that each interquartile range (IQR) increase in exposure to PM2.5 was associated with increased risk of enterotomy (HR = 1.16; 95% CI: 1.00, 1.34, p = 0.043), whereas an IQR increase in exposure to NOx (HR =1.10; 95% CI: 1.01, 1.20, p = 0.016), NO2 (HR =1.16; 95% CI: 1.03, 1.29, p = 0.010), PM10 (HR =1.15; 95% CI: 1.03, 1.30, p = 0.015), and PM2.5 (HR =1.14; 95% CI: 1.02, 1.28, p = 0.019) was associated with increased risk of all-cause mortality among individuals with IBD. We did not observe any significant associations between air pollutants and gastrointestinal cancer in the primary analyses. Consistent results were observed in subgroup and sensitivity analyses. CONCLUSIONS: Ambient pollution exposure was associated with an increased risk of enterotomy and all-cause mortality among individuals with IBD, highlighting the important role of environmental health in improving the prognosis of IBD. https://doi.org/10.1289/EHP12215