Race Not a Clear Factor in Diabetic Retinal Disease

NEWARK, N.J., Sept. 11 -- Race does not seem to substantially affect diabetic retinopathy in type 1 diabetes, according to a six-year study of African Americans here.

The proportion of African-American patients who developed diabetic retinopathy was similar to the proportion previously reported for mostly white patients in a Wisconsin study, said Monique S. Roy, M.D., of the New Jersey Medical School here.

In addition, the risk factors for diabetic retinopathy progression were the same among black patients were poor glycemic control, hypertension, duration of diabetes, and age, Dr. Roy and Mahmoud Affouf, Ph.D., of Kean University in Union, N.J., reported in the September issue of Archives of Ophthalmology. These risk factors are also the same as those reported for whites.

However, as glycemic and blood pressure control tend to be poorer in African American patients, they may benefit from closer monitoring of these conditions to help prevent diabetic retinopathy, the authors said.

The study included 483 African-American adults and children with type 1 diabetes who were originally part of the New Jersey 725 study, established in 1993. Of these, about 41% had no diabetic retinopathy, 35% had mild diabetic retinopathy, and 24% had moderate to severe diabetic retinopathy at baseline. In 1999, the 483 patients underwent a follow-up clinical evaluation that included an eye exam and photographs of the retina to assess retinopathy.

Of those without diabetic retinopathy at baseline, 72.3% had developed the disease over the six-year period, the study found. Of those with diabetic retinopathy at baseline, 56% had progressed to proliferative diabetic retinopathy, and nearly 16% had developed macular edema.

For comparison, the figures from the Wisconsin Epidemiologic Study of Diabetic Retinopathy, which included mostly white patients, showed 41% of patients without DR developing it over a four year period. Of those with the disease, 10.5% progressed to proliferative diabetic retinopathy, and 8.2% to macular edema.

The researchers characterized the progression of diabetic retinopathy as "very high" in both studies, noting that the figures were smaller in the Wisconsin study because of its shorter follow-up time (four years versus six years).

As has been found for whites, glycemic control was a chief risk factor. African Americans with diabetic retinopathy and the poorest glycemic control were more than 20 times more likely than those with the best control to progress to proliferative diabetic retinopathy (odds ratio=20.12; 95% confidence interval=4.7 to 86.7), the authors reported.

Hypertension was another risk factor that blacks and whites shared. African Americans with diabetic retinopathy and baseline hypertension were more than three times more likely than their counterparts with normal blood pressure to progress to proliferative diabetic retinopathy (OR=3.68; 95% CI=2.1 to 6.4).

The prevalence of hypertension was 44% in the African American study. Of these, 25% were not receiving anti-hypertensive medication, the authors noted. And of those who were on medication, nearly half (49.4%) did not have their blood pressure under control.

Progression to proliferative diabetic retinopathy was also significantly linked to age (P=.006) and duration of diabetes (P<.001). These risk factors have been reported in studies of predominantly white patients, the authors said.

"Poor glycemic control and systemic hypertension are two modifiable risk factors significantly associated with progression of diabetic retinopathy," the authors said. "Because glycemic and blood pressure control in this population are poor, measures to improve medical care and ensure regular dilated eye examination to detect vision-threatening diabetic retinopathy may reduce morbidity from the disease."