The relationship between hemoglobin levels and diabetic retinopathy.

This study evaluates the relationship between hemoglobin levels and diabetic retinopathy. Hemoglobin values measured in 1991 and 1992 were collected from 1691 subjects attending a diabetic clinic in Oulu, Finland, and the mean values for the two years were used in the analyses. A classification of retinopathy, based on non-mydriatic photographs taken in 1991 and 1992, was used as the outcome variable. Multiple logistic regression analyses, controlled for serum creatinine levels, proteinuria, and other prognostic factors associated with diabetes, showed that the odds ratio of having any retinopathy was 2.0 (95% confidence interval 1.2-3.3) among subjects with a hemoglobin level of less than 12 g/dl, as compared with those having a hemoglobin level > or = 12 g/dl. Among the retinopathic subjects with low hemoglobin levels, the relative odds of having a severe retinopathy rather than a mild one was 5.3 (2.3-12.6). We conclude that subjects with normocytic anemia tended to have an increased risk of retinopathy, especially of the severe form.