Air pollutants and risk of incident upper gastrointestinal bleeding events: A large prospective cohort study.

Currently, most population studies on air pollutants and gastrointestinal health focus on outcomes like chronic gastritis or gastrointestinal cancers, while evidence linking air pollutants to upper gastrointestinal bleeding (UGIB) risk remains unclear. This large prospective cohort study investigated the associations between long-term exposure to ambient air pollutants and the risk of UGIB by utilizing data from 432,773 participants in the UK Biobank, with a median follow-up period of 13.11 years. Cox proportional hazards models were used adjusting for demographic, lifestyle, and socioeconomic factors. Baseline characteristics showed UGIB cases were older (58.3 ± 8.0 vs. 56.4 ± 8.1 years), more likely to be male (50.9 % vs. 45.2 %), and exposed to higher levels of air pollutants. Multivariable-adjusted analyses revealed significant associations for PM2.5 [Q4 vs. Q1: 1.10 (1.06-1.15), P < 0.001], PM10 [Q4 vs. Q1: 1.07 (1.03-1.11), P = 0.002], NO2 [Q4 vs. Q1: 1.15 (1.10-1.20), P < 0.001], and NOx [Q4 vs. Q1: 1.11 (1.07-1.16), P = 0.002]. Subgroup analyses highlighted stronger associations in males. Mediation analysis showed the partial mediating role of vitamin D in the correlation between air pollutants and UGIB. These findings provide robust evidence that PM2.5, PM10, NO2, and NOx is independently correlated with an elevated risk of UGIB, particularly in males. Mechanisms may involve serum vitamin D concentrations. The results underscore the need for air quality interventions to reduce gastrointestinal morbidity, targeting vulnerable populations.