Colorectal cancer (CRC) remains a major global health burden, with increasing incidence among younger adults. Obesity and visceral fat accumulation are known contributors to CRC risk, yet conventional anthropometric indices have limitations in accurately capturing abdominal adiposity. The weight-adjusted waist index (WWI), a novel adiposity metric, may offer improved assessment. Data from 17,931 adults aged ≥20 years in NHANES 2009–2020 were analyzed. Multivariate logistic regression models assessed the association between WWI and CRC after adjustment for demographic, clinical, biochemical, lifestyle, and dietary variables. Restricted cubic spline (RCS) modeling and piecewise logistic regression were employed to evaluate nonlinear relationships. WWI demonstrated a significant negative association with CRC prevalence across all models. RCS analysis revealed a nonlinear dose–response pattern, with two inflection points at WWI = 9.852 and WWI = 11.848. A pronounced inverse association was present only within this interval (OR = 0.27; 95% CI 0.16–0.46), whereas no significant association was observed outside it. Subgroup analyses confirmed consistent findings across demographic and clinical strata, except for a significant interaction with smoking status. WWI is nonlinearly associated with CRC in U.S. adults, showing a strong inverse relationship within a specific WWI range. These findings highlight the potential utility of WWI as an alternative adiposity indicator in CRC-related epidemiologic assessments. Prospective studies are warranted to clarify causality and elucidate underlying biological mechanisms. Maintaining WWI within the identified threshold range may be associated with lower CRC prevalence in this population; prospective studies are needed to confirm causality and clinical implications.
Ding et al. (Tue,) studied this question.