Global, regional and national burden of colorectal cancer attributable to low-fiber diet from 1990 to 2021: a systematic analysis of the global burden of disease study 2021.

Background: Low-fiber diet is a modifiable dietary risk factor for colorectal cancer (CRC), but its long-term attributable burden and socioeconomic disparities remain insufficiently characterized. This study aimed to assess the global, regional, and national burden of colorectal cancer attributable to low-fiber diet (CRC-LFD) from 1990 to 2021 and to project future trends. Methods: Data were obtained from the Global Burden of Disease Study 2021. The estimation of CRC-LFD burden was based on the GBD comparative risk assessment framework, which integrates population-level exposure distributions, theoretical minimum risk exposure levels, and relative risks derived from meta-analyses to calculate population attributable fractions. Deaths, disability-adjusted life years (DALYs), age-standardized mortality rates (ASMRs), and age-standardized DALY rates (ASDRs) were analyzed. The Socio-demographic Index (SDI) was used to assess burden patterns across development levels. Das Gupta decomposition was applied to quantify the contributions of population growth, population aging, and epidemiological change. Cross-national inequality was evaluated using the Slope Index of Inequality and Concentration Index. Future trends to 2045 were projected using the Nordpred model. Results: From 1990 to 2021, global DALYs and deaths attributable to CRC-LFD increased by 24 and 36%, respectively, whereas ASDR and ASMR declined. The largest absolute DALY burden occurred in middle SDI regions, while the highest ASDR and ASMR were observed in high SDI regions. Among individuals younger than 80 years, males had higher attributable DALYs and deaths than females. Inequality analyses indicated persistent socioeconomic disparities, with relative inequality showing an increasing trend. Decomposition analysis suggested that, despite declining age-standardized rates, the absolute burden continued to rise mainly because of demographic changes, particularly population growth and aging. Projections indicated that deaths and DALYs would continue to increase by 2045, although ASDR and ASMR were expected to decline. Conclusion: CRC-LFD shows a paradoxical pattern of declining age-standardized rates but increasing absolute burden. These findings highlight the need to incorporate dietary fiber promotion into comprehensive CRC prevention strategies, develop systematic dietary policies, and implement SDI-specific interventions. As an ecological study, the results should be interpreted at the population level and cannot establish individual-level causality.