Global, regional, and national burdens of colorectal cancer and inflammatory bowel disease, 1990–2021 and projections to 2050: a cross-sectional study

BACKGROUND: Colorectal cancer (CRC) and inflammatory bowel disease (IBD) are major, interrelated digestive disorders whose global burdens are evolving with demographic aging, lifestyle westernization, and uneven access to prevention and care. Despite substantial disease-specific analyses, decision-makers still lack an integrated, up-to-date synthesis that jointly quantifies the burdens of CRC and IBD across sociodemographic contexts and provides robust projections to guide equitable resource allocation. This study, using Global Burden of Disease (GBD) 2021 data, addresses these gaps by harmonizing standardized burden metrics, temporal trend analyses, and long-range forecasts to elucidate shared and distinct trajectories of CRC and IBD. It aims to uncover associations between the diseases and prioritize prevention strategies. METHOD: We performed a cross-sectional analysis of GBD data for 1990-2021, covering 204 countries/territories, 21 GBD regions, and five sociodemographic index (SDI) strata. We estimated age-standardized incidence rates (ASIR), prevalence rates (ASPR), mortality rates (ASMR), and age-standardized disability-adjusted life year rate (ASDALYR), with two-sided P < 0.05 considered significant. Temporal changes were quantified using estimated annual percentage change (EAPC) and average annual/period percentage change. Future trajectories were projected using Bayesian age-period-cohort (BAPC) modeling. Analyses and visualization were conducted in R (v4.2.3) and JD_GBDR (v2.24). The study followed STROCSS reporting guidance. RESULTS: Globally, CRC incidence increased from 916.58 thousand in 1990 to 2194.14 thousand in 2021 (an increase of 139.38%), with pronounced heterogeneity across SDI strata. ASIR has been declining in high SDI regions since 2008 (EAPC = -0.25) but rising sharply in medium SDI areas (EAPC = 1.38). CRC prevalence rose by 173.72% overall, with medium-SDI regions experiencing a particularly steep increase (~401.69% over 30 years), contrasting with earlier peaks and partial stabilization in high-SDI settings. Although CRC deaths increased by 83.07% in absolute numbers, ASMR declined from 21.82 to 17.39, consistent with gains from screening and improved treatment in higher-SDI regions. Disability-adjusted life year rates rose 69.49%, while ASDALYR declined, indicating improved diagnostics and prevention. Projections show slow incidence growth to 2039 due to environmental risks, reversing post-2039 with prevention measures; ASPR growth slows, while ASMR and ASDALYR continue declining. For IBD, cases increased from 199.23 to 375.12 thousand (88.28%), with the fastest ASIR growth in medium-SDI regions (EAPC = 1.54); high SDI areas slowed via biologics. Prevalence showed "increasing cases, decreasing rates," with ASPR dropping from 48.02 to 44.88/100 000. Deaths doubled, but ASMR fell to 0.52/100 000; ASDALYR decreased 2.89% in East Asia. Forecasts predict declines in all indicators from 2022 to 2050, with accelerated ASMR drops post-2030, reflecting treatment advancements. CONCLUSION: By jointly appraising CRC and IBD burdens, temporal trends, and long-range projections across 204 countries, this study provides the most comprehensive, policy-relevant synthesis to date. It delineates actionable disparities by SDI strata, clarifies the epidemiologic interrelationship between IBD and CRC risk, and offers decision-grade evidence to prioritize screening, lifestyle modification, and equitable access to effective therapies - thereby advancing global strategies for prevention and control.