Genetics of Hypertension in Blacks

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00005387
Recruitment Status : Completed
First Posted : May 26, 2000
Last Update Posted : July 12, 2016
Information provided by:
National Heart, Lung, and Blood Institute (NHLBI)

Brief Summary:
To investigate the genetic determinants of hypertension in three populations of the African diaspora, with a major focus on clarifying the role of genes that code for the renin-angiotensin system (RAS).

Condition or disease
Cardiovascular Diseases Heart Diseases Hypertension

Detailed Description:


This community-based study in three geographically distinct populations of West African heritage with contrasting levels of hypertension risk was one of the first comprehensive examinations of the genetics of hypertension in African Americans. The study focused on the renin-angiotensin system (RAS) because it was the only physiological arm of blood pressure control for which candidate genes had been securely linked to the risk of hypertension. Polymorphisms at the angiotensinogen locus varied considerably between Blacks and whites. The documented Black:white differences in the RAS system emphasized the importance of determining whether RAS genes contributed to the excessively high risk of hypertension experienced by African Americans. The study generated unique information about the variability of the RAS loci in populations of West African heritage, and the contribution of this variability to hypertension risk. The data from the study, including the DNA specimens, also represented a valuable resource for future work on the genetics of hypertension in this important ethnic group.


The primary goals of this study were: 1) Determine the extent to which genetic variability of the RAS genes influenced the distribution of blood pressure (and of RAS intermediate phenotypes) within each population, and contrast the results across populations; 2) Use family studies, within each population, to determine the degree-of familial aggregation of blood pressure, and of the RAS intermediate phenotypes; 3) Use segregation analysis to determine the contribution of 'major genes' to the familial aggregation of blood pressure and of hypertension, and determine whether RAS genes cosegregate with hypertension, or with RAS intermediate phenotypes; 4) Evaluate whether the different prevalence of hypertension in each community reflected differences in their genetic background. The study sites included Ibadan, Nigeria, Kingston, Jamaica, and Maywood, IL. At each site, genetic and epidemiological data were collected from individuals, sampled as follows: individuals comprising 100 five- member structured family sets (proband, spouse, two sibs, one offspring, or half-sib), equally ascertained from the highest and lowest quartiles of the blood pressure distribution, as defined by an ongoing community-wide survey; unrelated singletons, also sampled equally from the highest and lowest blood pressure quartiles. The following measurements were obtained from all participants. Epidemiological variables: blood pressure, height, weight, waist/hip ratio, skinfolds, urine sodium/potassium and sociodemographic variables; Intermediate phenotypes: Plasma levels of angiotensinogen, renin and angiotensin-converting enzyme (ACE); Genotypes: A set of DNA polymorphisms at the four main RAS loci (angiotensinogen, renin, ACE and the angiotensin II-type l receptor).

The study was renewed in FY 2000. To further elucidate the environmental pathways, the investigators conducted a substudy cross-classifying participants on the major risk determinants (ie, obesity and sodium intake) and they examined gene-environment interactions directly. They used a genome scan in linkage analysis to identify new chromosomal regions of interest. They also examine two new candidate loci (adducin and beta-2 adrenergic receptor) and conducted association studies using single nucleotide polymorphisms. They used the full range of analytic tools, including segregation, linkage and cladistic analysis.

The study was renewed again in FY 2005 to : supplement evidence of hypertension causation on chromosomes 6,7, and 11 with a new set of dense markers and to search for positional candidate genes for hypertension at the two best regions; identify the genes under the linkage peak(s), find appropriate single nucleotide polymorphisms for a frequency of greater than 10% and conduct association/linkage disequilibrium mapping; replicate these findings in additional case-control studies and assess potential gene-environment interactions.

Study Type : Observational
Study Start Date : September 1995
Actual Primary Completion Date : December 2008
Actual Study Completion Date : December 2008

Information from the National Library of Medicine

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Ages Eligible for Study:   up to 100 Years   (Child, Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
No eligibility criteria

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00005387

Sponsors and Collaborators
National Heart, Lung, and Blood Institute (NHLBI)
OverallOfficial: Richard Cooper Loyola University

Publications: Identifier: NCT00005387     History of Changes
Other Study ID Numbers: 4293
R01HL053353 ( U.S. NIH Grant/Contract )
First Posted: May 26, 2000    Key Record Dates
Last Update Posted: July 12, 2016
Last Verified: December 2008

Additional relevant MeSH terms:
Cardiovascular Diseases
Heart Diseases
Vascular Diseases