Climate classification, sociodemographic development, and the burden of inflammatory bowel disease in tropical...

Geographic definitions of the tropics may obscure substantial climatic heterogeneity. Climate classification provides a more ecologically meaningful framework for evaluating inflammatory bowel disease (IBD) in tropical settings. However, few studies have examined tropical IBD burden using an integrated framework that combines climate classification, sociodemographic development, decomposition analysis, frontier analysis, and long-term forecasting.

We analyzed 1990-2023 estimates of IBD incidence, prevalence, mortality, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs) from the Global Burden of Disease Study 2023. Climatic heterogeneity was characterized using the Koppen-Geiger climate classification. Temporal trends were evaluated with estimated annual percentage change (EAPC), and associations with tropical climate proportion and the sociodemographic index (SDI) were examined using Spearman rank correlation. Das Gupta decomposition quantified the contributions of population growth, population aging, and epidemiological change to changes in absolute burden. Frontier analysis and autoregressive integrated moving average (ARIMA) models were used to assess potential for improvement and forecast age-standardized burden through 2050.

In 2023, IBD burden varied substantially across the 96 tropical countries and territories matched to GBD 2023. A higher tropical climate proportion was negatively correlated with the age-standardized incidence rate (ASIR; rho = - 0.279), age-standardized prevalence rate (ASPR; rho = - 0.318), and age-standardized YLD rate (rho = - 0.313). SDI was positively correlated with ASIR (rho = 0.248) and ASPR (rho = 0.270), but negatively correlated with the age-standardized death rate (ASDR; rho = - 0.310), age-standardized YLL rate (rho = - 0.372), and age-standardized DALY rate (rho = - 0.223). Population growth and aging accounted for most increases in absolute burden. For both sexes combined, population growth explained 58.7% of the increase in prevalent cases, 81.2% of the increase in DALYs, and 97.6% of the increase in YLLs. ARIMA forecasts suggested that ASDR would decline from 0.41 to 0.29 per 100,000 between 2024 and 2050. The age-standardized DALY rate was projected to decline from 15.33 to 13.28 per 100,000, and the age-standardized YLL rate from 10.14 to 8.24 per 100,000. Incidence, prevalence, and YLD rates were projected to remain broadly stable.

IBD burden in tropical regions varies across climatic and sociodemographic contexts. Climate-related environmental factors may contribute to geographic differences, but this ecological analysis does not support causal inference.