Education, Genetic Ancestry, and Blood Pressure in African Americans and Whites

Education, Genetic Ancestry, and Blood Pressure in African Americans and Whites

American Journal of Public Health
August 2012, Volume 102, Number 8
pages 1559-1565
DOI: 10.2105/AJPH.2011.300448

Amy L. Non, Assistant Professor of Anthropology,
Vanderbilt University, Nashville, Tennessee

Clarence C. Gravlee, Associate Professor of Anthropology;  affiliate appointments in the Department of Behavioral Science and Community Health
University of Florida, Gainesville

Connie J. Mulligan, Professor of Anthropology; Associate Director, University of Florida Genetics Institute
University of Florida, Gainesville

  • Objectives. We assessed the relative roles of education and genetic ancestry in predicting blood pressure (BP) within African Americans and explored the association between education and BP across racial groups.
  • Methods. We used t tests and linear regressions to examine the associations of genetic ancestry, estimated from a genomewide set of autosomal markers, and education with BP variation among African Americans in the Family Blood Pressure Program. We also performed linear regressions in self-identified African Americans and Whites to explore the association of education with BP across racial groups.
  • Results. Education, but not genetic ancestry, significantly predicted BP variation in the African American subsample (b = –0.51 mm Hg per year additional education; P = .001). Although education was inversely associated with BP in the total population, within-group analyses showed that education remained a significant predictor of BP only among the African Americans. We found a significant interaction (b = 3.20; P = .006) between education and self-identified race in predicting BP.
  • Conclusions. Racial disparities in BP may be better explained by differences in education than by genetic ancestry. Future studies of ancestry and disease should include measures of the social environment. (Am J Public Health. 2012; 102:1559–1565. doi:10.2105/AJPH.2011.300448)

In recent decades, researchers have struggled to determine the causes of racial disparities in health. Many biomedical researchers have speculated that underlying genetic differences between races may contribute to these disparities. With the increasing availability of high-throughput genotyping platforms, a wealth of genomic data is now available to help address this issue. One consequence is that more researchers are estimating genetic ancestry to capture a presumed genetic basis of racial disparities in health. However, any associations found between genetic ancestry and disease could alternatively be explained by unmeasured environmental factors that are also associated with African genetic ancestry and contribute to health disparities, such as socioeconomic status (SES), neighborhood environment, and psychosocial factors including perceived stress or discrimination. Therefore, to avoid unwarranted inferences about the magnitude of genetic influences on health disparities, it is critical for any analysis of ancestry and disease to include appropriate social–environmental variables.

Social–environmental factors may be especially important when one is studying a complex disease such as hypertension. Complex diseases, by definition, involve multiple environmental and genetic causes, as well as interactions within and between them. Many studies have identified important social–environmental influences on racial inequalities in hypertension, such as SES, psychosocial stressors, and neighborhood environment, whereas other studies have begun to identify relevant genetic variants, such as those in the rennin–angiotensin–aldosterone axis and the adrenergic system. Few studies, however, have examined genetic and environmental factors simultaneously. The limited scope of this research to date has slowed progress toward explaining racial inequalities in hypertension and other complex diseases.

To address the relevance of both genetic and environmental factors in racial inequalities in hypertension, we tested associations between genetic ancestry, education, and blood pressure (BP) among Whites and African Americans in the Family Blood Pressure Program (FBPP) study. A previous analysis of this data set by Tang et al. found no evidence of a statistically significant association between African genetic ancestry and blood pressure. They concluded nonetheless that the results were “suggestive of genetic differences between Africans and non-Africans that influence blood pressure, but such effects are likely to be modest compared to environmental ones.” No environmental variables were included in their study, however. Here we reexamine the FBPP data set to test how the addition of education affects the association between ancestry and BP in African Americans. We also explored the association between education and blood pressure across racial groups. We hypothesized that education would show a greater association with BP than would African ancestry among African Americans, and that the association between education and BP may vary by racial and gender groups…

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