Hemoglobin levels predicted proliferative diabetic retinopathy incidence

Higher hemoglobin levels appear to predict the incidence of proliferative diabetic retinopathy in patients with type 1 diabetes.

Researchers evaluated this association in 426 patients without proliferative diabetic retinopathy at baseline. The patients were part of the Pittsburgh Epidemiology of Diabetes Complications Study, an 18-year prospective cohort study evaluating childhood-onset type 1 diabetes. Hemoglobin levels ranged from 9.2 g/dL to 20 g/dL; men had a median level of 16.2 g/dL and women had a median level of 14.1 g/dL. Median follow-up time was 14.6 years.

During the course of the study, 206 patients developed proliferative diabetic retinopathy, and the incidence did not vary by sex, with a 48% incidence rate for each men and women. However, in men, hemoglobin levels demonstrated a positive linear relationship with the incidence of proliferative diabetic retinopathy (HR=1.33; 95% CI, 1.10-1.60). In women, this relationship was quadratic (P<.001). The researchers noted that this finding was of interest but likely reflects the smaller sample sizes at the lower ends of the distribution in men at levels ≤13.4g dL, where there was an increased risk for women.

Hemoglobin levels remained predictive of proliferative diabetic retinopathy in both men (P=.004) and women (P=.04) after adjusting for univariately significant covariates.

The researchers noted that other multivariable predictors for proliferative diabetic retinopathy included HbA1c levels and diastolic blood pressure, as well as albumin excretion rate in men and systolic BP and fibrinogen in women.

Hemoglobin levels were also predictive of other markers of retinopathy including macular edema (P<.001 for men and P=.03 for women) and two-step progression (P=.03 for men and P<.001 for women).

Conway BN. Arch Ophthalmol. 2009;127:1494-1499.