Association Between Red Blood Cell Distribution Width to Albumin Ratio (RAR) and Cataract Risk: A Cross-Sectional Study from NHANES 1999–2008

To evaluate the association between red blood cell distribution width to albumin ratio (RAR) and cataract risk among US adults. A cross-sectional study was conducted utilizing the National Health and Nutrition Examination Survey (NHANES) from 1999–2008. RAR was calculated using red blood cell distribution width and serum albumin measurements obtained from mobile examination centers, with higher values indicating greater systemic inflammation and nutritional deficiency. Self-reported history of cataract surgery served as a proxy for cataract diagnosis. Covariates included sociodemographic factors, lifestyle variables, and comorbidities. Multivariable logistic regression models were employed to evaluate the association between RAR and cataract. Restricted cubic spline (RCS) analysis was performed to examine potential nonlinear relationships. Propensity score matching (PSM) was implemented to reduce confounding bias. Finally, subgroup analysis was performed to investigate potential interaction effects. The analytical cohort comprised 26,397 participants, among whom 2,295 (8.70%) had cataract. Cataract patients exhibited significantly higher RAR values (3.22 ± 0.47) compared to non-cataract participants (3.06 ± 0.46). After adjustment for all covariates, a positive association between RAR and cataract was observed, both when RAR was treated as a continuous variable (odds ratio (OR) = 1.412, 95% confidence interval (CI): 1.208–1.649; P < 0.001) and when analyzed categorically by quartiles. Participants in the highest RAR quartile had significantly increased cataract risk relative to the lowest quartile (OR = 1.572, 95% CI: 1.261–1.958; P < 0.001). RCS analysis revealed no evidence of nonlinearity (P for nonlinearity = 0.520). This positive association persisted in a 1:2 PSM analysis. Subgroup analysis revealed no significant interaction effects across covariates, with the RAR–cataract association remaining statistically significant in most subgroups. Elevated RAR is independently associated with higher cataract prevalence, implicating systemic inflammation and nutritional deficiency as modifiable risk factors.