News Release

Hypertension-related eye damage more common in blacks than whites

Peer-Reviewed Publication

American Heart Association

DALLAS, March 25 – For the first time, researchers have shown that hypertensive retinopathy, a form of blood vessel damage in the eye, is twice as common in African Americans as in Caucasians, according to a study in today's rapid access issue of Hypertension: Journal of the American Heart Association.

"Blood vessel damage in the eye is linked with similar changes in the brain and has been shown to be associated with a higher risk of stroke and death, independent of known risk factors," says Tien Yin Wong, M.D., Ph.D., lead author and assistant professor at the Singapore National Eye Center at the National University of Singapore.

The study authors say the findings have important public health implications.

"The higher frequency of this condition in African Americans may explain why they are at higher risk of stroke," he adds. Retinopathy is an important sign that a person's hypertension (high blood pressure) has progressed to a severe stage, causing organ damage.

The higher prevalence of hypertension in blacks compared with the whites in the United States is well documented. Blacks are more likely than whites to develop hypertension-related complications, such as heart problems, kidney disease, and stroke. Blacks also have less access to drugs that treat high blood pressure and a higher death rate from the disease.

Even though the thinking has been that blacks have an excess risk of hypertensive retinopathy, few existing studies make this connection, and the studies were not based on patient groups representative of the general population.

Wong and colleagues designed a community-based study of blacks and whites living in the United States and examined risk factors that may account for possible racial differences in the rate of retinopathy. The study participants were from the Atherosclerosis Risk In Communities (ARIC) study.

It's a population-based study of 15,792 women and men who were 45–65 years old at recruitment in 1987–1989. Participants lived in one of four U.S. communities: Forsyth County, N.C.; Jackson, Miss.; and suburbs of Minneapolis, Minn., and Washington County, Md.

Researchers excluded ARIC participants with health problems such as diabetes because it complicates the assessment of retinopathy. That left 1,860 blacks and 7,874 whites, aged 49 to 73 years, in the study group. Retinal photographs were taken of one randomly selected eye and evaluated for the presence of retinopathy, characterized by flame and blot-shaped retinal hemorrhages and enlarged capillaries. These images were evaluated by experts without access to information about the participants. Participants were interviewed and underwent clinical examination, and laboratory tests.

After adjusting for age and gender, blacks had higher normal blood pressure and were more likely to have hypertension and left-ventricular hypertrophy (thickened heart muscle caused by hypertension). They tended to be less educated, had higher HDL ("good") cholesterol, higher body mass index, and higher blood creatinine levels, which can identify kidney disease. They were less likely to have ever smoked or drunk alcohol.

The prevalence of retinopathy was nearly two times higher in blacks than in whites (7.7 percent versus 4.1 percent). The prevalence of retinopathy in blacks was reduced by about 53 percent, after adjusting the findings to account for the severity of hypertension and other cardiovascular risk factors.

"We found that differences in blood pressure explained about half of the excess prevalence of retinopathy in African Americans," says Wong. "Thus, controlling hypertension in African Americans is probably one method to reduce the higher prevalence of retinopathy." Because these adjustments significantly altered the findings, the researchers conclude that the excess occurrence of hypertensive retinopathy in African Americans is closely linked to racial differences in blood pressure levels and hypertension severity. "Our findings provide the first documentation of higher prevalence of hypertensive retinopathy in African Americans in contemporary, community-based populations in the United States," the authors write.

A secondary analysis that included diabetics found an even higher occurrence of hypertensive retinopathy in African Americans. "We may have underestimated the racial differences in hypertensive retinopathy," they say.

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Co-authors are Ronald Klein, M.D., M.P.H.; Bruce B. Duncan, M.D., Ph.D.; F. Javier Nieto, M.D., Ph.D.; Barbara E.K. Klein, M.D., M.P.H.; David J. Couper, Ph.D.; Larry D. Hubbard, M.A.T.; and A. Richey Sharrett, M.D., Dr.P.H. This study was funded by the National Heart, Lung, and Blood Institute.

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