Association between red blood cell distribution width-to-albumin ratio and cancer prevalence in US adults: a NHANES cross-sectional study (1999–2018)

Introduction The red blood cell distribution width-to-albumin ratio (RAR) is a composite biomarker reflecting integrated inflammation and nutrition status. Unlike conventional biomarkers assessing isolated pathways, RAR holistically evaluates their interplay, suggesting potential utility for cancer risk stratification. This study seeks to investigate the association between RAR and cancer in U.S. adults. Methods Using data from 43,094 NHANES participants (1999–2018), we employed multivariable logistic regression to assess RAR-cancer associations. Restricted cubic spline (RCS) evaluated nonlinear association and threshold effects. The study also used subgroup analysis and interaction tests to explore whether the association was stable in the population. Results In the cross-sectional study, 3,893 participants (9.0%) had cancer. RAR was positively associated with cancer among 43,094 participants aged ≥ 20 years. In the fully adjusted model, each per unit increase in RAR was associated with a 30% increase in the likelihood of cancer (OR = 1.30, 95% CI: 1.20 ~ 1.39, P < 0.001). Participants in the top quartile of RAR had a 36% increased risk of cancer than those in the bottom quartile of RAR (OR = 1.36, 95% CI = 1.22 ~ 1.53, P < 0.001). RCS revealed that the association between RAR and cancer was nonlinear (P for nonlinear = 0.028). Subgroup analyses showed that the association between RAR and cancer was significantly stronger in males group (P for interaction < 0.001). Discussion This study demonstrates that a significant correlation was identified between RAR and risk of cancer in U.S. adults, suggesting that RAR may function as a clinically relevant biomarker for risk stratification and provides potential evidence for subsequent pathological mechanism research. Further large-scale prospective studies are warranted to delineate the role of RAR in cancer.