Residential altitude and incident gastrointestinal disease in middle-aged and older adults: a nationwide cohort study

Background Acute exposure to high altitude has been associated with gastrointestinal symptoms. However, whether long-term residential altitude influences the risk of incident gastrointestinal disease (GID) remains unclear. Methods This study utilized nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2020. Residential altitude was estimated according to the elevation of participants’ county-level residential administrative units and categorized into lower-altitude (< 1,000 m) and middle-altitude (≥ 1,000 m) groups. Propensity score matching (PSM) with a 1:4 ratio was performed to balance baseline characteristics. Cox proportional hazards models were applied to estimate the association between altitude and incident GID. Restricted cubic spline (RCS) regression was applied to assess potential nonlinear associations. Subgroup analyses and sensitivity analyses using inverse probability of treatment weighting (IPTW) and the full cohort (n = 10,345) were conducted to evaluate robustness of the primary findings. Results Among 6,099 participants in the matched cohort, 850 (13.9%) developed incident GID during the follow-up period. Compared with residents in low-altitude regions, participants living in middle-altitude areas exhibited an elevated risk of incident GID (HR = 1.24, 95% CI: 1.06–1.45, P = 0.008). There was a significant dose-response association between altitude and GID risk ( P for trend < 0.001), and RCS analysis further confirmed a significant nonlinear relationship ( P for nonlinear = 0.042), whereby GID risk reached a plateau at altitudes above 1,000 m. Subgroup analyses revealed a significant effect modification by educational attainment. Sensitivity analyses based on the full cohort and IPTW yielded consistent results. Conclusions Higher residential altitude was associated with an increased risk of incident GID among middle-aged and older adults in China, with a nonlinear exposure-response pattern. These findings suggest that residential altitude may represent a potential environmental factor of gastrointestinal health in aging populations.