Global, regional, and national burden of colorectal cancer attributable to central obesity: a population attributable fraction analysis

Background Central obesity is a major risk factor for colorectal cancer (CRC) and may better reflect obesity-related risk than body mass index (BMI). Its global burden, however, remains poorly quantified. We aimed to estimate the number and proportion of CRC cases attributable to central obesity in 2022 across global, regional, and national levels. Methods We estimated population attributable fractions (PAFs) by combining sex-specific prevalence of central obesity from national surveys with pooled relative risks from meta-analysis. Central obesity was defined as elevated waist circumference using standardised sex- and ethnicity-specific thresholds, accounting for variation in definitions via probabilistic modelling. We addressed missing data through multiple imputation. CRC incidence estimates for 2022 were obtained from GLOBOCAN for 185 countries. Monte Carlo simulations propagated uncertainty in exposure prevalence and risk estimates. Results In 2022, an estimated 311 418 (95% uncertainty interval 242 603-378 880) CRC cases were attributable to central obesity, corresponding to a global PAF of 16.2% (12.6-19.7). PAFs were higher in females (18.2%, 13.0-23.3) than in males (14.5%, 9.6-19.3), though age-standardised rates (ASRs) were slightly higher in males. The highest PAF was in North America, and the highest ASRs in Australia-New Zealand and northern Europe. PAFs and ASRs declined with decreasing income levels among males but not females. Regional variation in sex differences was substantial, with higher female PAFs in parts of Africa and Asia, and smaller or reversed gaps in high-income settings. In high-income countries, the estimated 10-year CRC risk at screening age (55-69 years) was 1.32% in males with central obesity versus 0.90% in those without, and 0.92% versus 0.64% in females, corresponding to one excess CRC case per 236 (180-353) men and 357 (279-502) women. Conclusions Central obesity accounts for a substantial share of the global CRC burden, with large geographical variability. Applying established waist circumference thresholds in surveillance and incorporating central obesity into individual risk stratification may inform more effective CRC screening and prevention strategies.