This analysis used GBD 2023 data to interrogate how conventional age grouping (under 50 vs 50 and older) may conceal burden patterns occurring around the contemporary colorectal cancer (CRC) screening boundary. The authors specifically assessed whether adults aged 45–49 years occupy a threshold-adjacent position not captured by the usual <50 versus ≥50 split. The work focused on incidence, deaths, and disability-adjusted life years (DALYs) over the period 1990–2023.
The study extracted CRC incidence, mortality, and DALY estimates from GBD 2023 and stratified results across four age groups: 15–44, 45–49, 50–74, and 75+ years. Analyses included global trends and stratification by the Sociodemographic Index (SDI). The investigators assessed inequality using concentration indices (CI) and relative slope index of inequality (SII), constructed empirical lower-bound burden frontiers, and performed decomposition of burden change to quantify contributors to rate variation over time.
Several sensitivity analyses were performed as reported in the source: conventional age regrouping (i.e., the typical <50 vs ≥50 cut), decomposition comparing High versus Non-High SDI strata, split-period analyses, and comparisons with adjacent 5-year age groups to test the stability of observed patterns around the screening threshold.
Across 1990–2023, CRC incidence rose most sharply in adults aged 15–44 (+16.8%) and 45–49 (+11.0%). Incidence increases were smaller in those aged 50–74 (+7.5%) and 75+ (+3.6%). By contrast, deaths and DALYs showed clearer declines in age groups above 50 years.
Inequality trends in adults aged 45–49 indicated a narrowing of incidence inequality: the concentration index decreased from 0.304 to 0.253, and the relative SII fell from 1.693 to 1.412. DALY inequality in the 45–49 group also weakened, with the concentration index moving from 0.159 to 0.068 over the study period.
Decomposition analyses for 2010–2023 revealed that the residual rate-change component contributed positively to incidence among adults aged 45–49 globally (31.5%). In contrast, the same component was slightly negative for those aged 50–74 (-2.6%), indicating divergent underlying drivers of incidence change across these age strata.
The authors observed a post-2018 amplification of incidence in High-SDI populations. This amplification was consistent with detection effects related to screening, aligning temporally with changes in screening practice or policy in higher-SDI settings.
The findings indicate that adults aged 45–49 occupy a context-dependent, threshold-adjacent position in the redistribution of global CRC burden. Incidence increases concentrated in younger adults (15–44 and 45–49) contrast with declines in mortality and DALYs in older age groups, suggesting changing detection patterns, disease dynamics, or both.
Narrowing inequality in incidence and DALYs for the 45–49 group suggests that burden redistribution across SDI strata has shifted over time. The positive residual rate-change contribution to incidence in 45–49-year-olds implies additional unexplained factors increasing observed incidence in this age window, whereas the slight negative contribution in 50–74-year-olds suggests different dynamics in older screening-eligible populations.
The observed post-2018 amplification in High-SDI settings is interpreted in the source as consistent with screening-related detection effects, which could elevate measured incidence adjacent to screening thresholds as programs expand or screening eligibility changes.
Using GBD 2023, the authors conclude that adults aged 45–49 frequently occupy a threshold-adjacent position in global CRC burden redistribution. This position is context-dependent, varying with SDI and over time, and manifests as rising incidence for ages just below or at contemporary screening boundaries, coupled with evolving inequality patterns.
The authors explicitly frame these results as informing population-level surveillance and policy evaluation rather than as guidance for individual clinical decision-making.
The analysis highlights that age grouping choices affect observed epidemiologic patterns around screening boundaries. Monitoring 45–49-year-olds as a discrete group may reveal redistribution signals—such as incidence rises and shifting inequality—not apparent when using broad <50 versus ≥50 categories. Policy evaluation and surveillance systems that track age-adjacent groups can better detect screening-related detection effects and changing burden distribution across SDI strata.
The abstract does not provide specific methodological or data limitations beyond the analytic scope described. Details on limitations, data quality considerations, or additional contextual caveats were not reported in the source abstract.
Keywords: Colorectal cancer; DALYs; GBD 2023; SDI; age groups; decomposition; inequality; screening threshold.