Relationship between hemoglobin levels and diabetic retinopathy in Chinese type 2 diabetes mellitus populations: a cross-sectional study

Abstract

Background – Diabetic retinopathy (DR) remains one of the leading causes of visual impairment worldwide. Recent studies have suggested that hemoglobin (Hb) levels may be associated with the risk of DR; however, the evidence has been inconsistent. This study aimed to evaluate the relationship between Hb concentration and the presence of DR among Chinese individuals with type 2 diabetes mellitus (T2DM). Methods – We performed a cross-sectional analysis including 9, 215 patients with T2DM. Hemoglobin levels were categorized into sex-specific tertiles to examine their association with DR. Multivariable logistic regression models were constructed with adjustment for demographic, behavioral, and clinical covariates. Potential nonlinear relationships were explored using restricted cubic spline (RCS) models. Subgroup and sensitivity analyzes were also conducted to assess the robustness of the findings. Results – Among all participants, 1, 757 (19.1%) were diagnosed with DR. The prevalence of DR was significantly higher in the lowest Hb tertile compared with the middle and highest tertiles (24.5% vs. 16.4% vs. 16.6%, P < 0.001). After adjusting for potential confounders, each 1 g/L increase in Hb was associated with a 1% reduction in DR risk (adjusted OR 0.99, 95% CI 0.98-0.99). Compared with the lowest tertile, participants in higher Hb tertiles had a lower likelihood of DR (T2: OR 0.68, 95% CI 0.59-0.78, P < 0.001; T3: OR 0.67, 95% CI 0.58-0.77, P < 0.001). These associations were consistent across predefined subgroups (all P for interaction > 0.05) and remained stable in sensitivity analyzes restricted to complete cases. RCS analysis demonstrated a nonlinear, inverted L-shaped association between Hb and DR in men (P for nonlinearity = 0.041), whereas a linear inverse relationship was observed in women (P for nonlinearity = 0.977). Conclusions – Hb levels are negatively associated with the presence of DR in Chinese patients with T2DM, suggesting that Hb may serve as a useful clinical indicator for DR risk stratification.