The Bad News About Prevalence, the Good News About Treatments -- But Pay Attention to the Details

Linda Brookes, MSc


February 14, 2005

In This Article

Is It Genetic? Hypertension Prevalence Varies Widely Among Populations of African Origin

An international study has addressed the question of whether the consistent finding of higher prevalence of hypertension in US blacks compared with whites reflects a particular susceptibility to the condition in African-origin populations. In the January 5 issue of BMC Medicine ,[5] Richard S. Cooper, MD (Loyola University Stritch School of Medicine, Maywood, Illinois) and other researchers report that hypertension prevalence varies widely among both black and white populations in different regions of the world. They believe that when viewed this way, it can be seen that the rates among US blacks are not unusually high, and that the impact of environmental factors among both blacks and whites may have been underappreciated.

Dr. Cooper and colleagues examined patterns of hypertension prevalence in 3 surveys taken among blacks in Africa, the Caribbean, and the United States, and in 8 surveys conducted since 1986 among whites in the United States, Canada, and Europe. Data for the black populations came from the International Collaborative Study on Hypertension in Blacks (ICSHIB)[6] and NHANES III.[7] The data for the white populations came from NHANES III and 7 other surveys that were analyzed previously by Dr. Cooper's group.[8] A standardized analysis strategy was used to examine prevalence estimates in a total of 85,000 participants.

In the African-origin populations, hypertension prevalence was 13.5% in Nigeria, 28.6% in Jamaica, and 44.0% in US blacks. This gradient from East to West parallels the gradient in socioeconomic development and associated lifestyle, the researchers note. In the white populations, hypertension prevalence ranged from 27% to 55%. Hypertension prevalence was higher in all the European populations than in the United States and Canada, as previously reported.

When put in this international context, the prevalence of hypertension in US blacks (44.0%) was close to the mean of all the populations (37.0%). All of the other populations with a prevalence above the mean were European. Differences were seen in gender-specific prevalence between the populations: hypertension was substantially more common in Jamaican women compared with Jamaican men, whereas "relative gender equality" was seen in US blacks. In Europe, the prevalence of hypertension was higher among men in every country.

Dr. Cooper and colleagues suggest that if the differences in hypertension between North American and European populations are occurring in genetically homogeneous populations, "large environmental influences must be at work that are not apparent on the surface." A similar process could be taking place within the social environments of African-origin individuals in the United States, they suggest. They believe that their data demonstrate that "the consistent emphasis given to the genetic elements of racial contrasts" distracts from "the more relevant issue" of defining and intervening in the preventable causes of hypertension, which are likely have a similar impact, regardless of ethnic and racial background.


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