Association Between Body Mass Index and Overall Survival in Patients With Colorectal Cancer in Taiwan

Colorectal cancer (CRC) represents an increasing global health burden. Evidence suggests that body mass index (BMI) may influence survival in CRC; however, large-scale data from Asian populations and sex-specific differences remain limited. We investigated the association between BMI and overall survival among patients with CRC in Taiwan.

We conducted a nationwide cohort study using the Taiwan Cancer Registry linked with National Health Insurance claims for patients with CRC diagnosed between 2011 and 2020. A total of 96,500 patients were categorized as underweight (<18.50 kg/m²), normal weight (18.50-23.99 kg/m²), overweight (24.00-26.99 kg/m²), or obese (≥27.00 kg/m²).

During follow-up to December 2021, 37,728 deaths occurred. Compared with normal BMI, underweight status was associated with higher mortality [adjusted hazard ratio (aHR)=1.61, 95% confidence interval (CI)=1.55-1.67], whereas overweight (aHR=0.80, 95%CI=0.78-0.82) and obesity (aHR=0.77, 95%CI=0.75-0.80) were associated with reduced mortality risk. Sex-stratified analyses demonstrated consistent trends across both sexes: underweight status significantly increased mortality in men (aHR=1.70, 95%CI=1.63-1.79) and women (aHR=1.52, 95%CI=1.45-1.60), whereas overweight and obesity remained protective factors for both sexes (all p<0.05).

These findings exhibit a significant association between BMI and mortality in patients with CRC. Underweight status confers increased mortality, while overweight or obesity is associated with improved survival in both men and women.