Sex-specific threshold effect of albumin-corrected fructosamine on diabetic retinopathy: a nonlinear relationship in women but linear in men — a cross-sectional study

Background Albumin-corrected fructosamine (AlbF) is a short-term glycemic marker that can substitute for HbA1c when HbA1c is unreliable. Studies have linked AlbF to diabetic retinopathy (DR), but it is not known whether the dose-response curve differs between men and women. We investigated this in 1,090 type 2 diabetes patients (433 men, 657 women) from a single Chinese center. Methods Restricted cubic splines were used to model the AlbF-DR relationship separately by sex, with threshold identification via segmented logistic regression. Models included age, BMI, diabetes duration, systolic blood pressure, HbA1c, HDL-C, and medications as covariates. Results Each 10 μmol/g increase in AlbF raised DR risk in both sexes: men OR 1.83 (95% CI 1.39–2.41), women OR 1.58 (95% CI 1.26–1.99). The RCS curves told a different story. Men followed a linear pattern (P for nonlinearity = 0.751). Women showed a threshold near 62.0 μmol/g (P for nonlinearity < 0.001). Below that value, the OR was 2.57 (95% CI 1.74–3.81); above it, the association was no longer significant (OR 1.29, 95% CI 0.69–2.42; P for interaction < 0.001). Sensitivity analyses consistently reproduced this nonlinear pattern. Conclusions The AlbF-DR relationship is linear in men but follows a threshold model in women, with a change point near 62.0 μmol/g. Sex-specific risk modeling may improve DR stratification. Whether the threshold holds in practice will require prospective studies.