Center on Population Health and Aging

Pilot Projects

Pilot Project 2: The Association between Genetic and Environmental Factors and Hypertension

Keith Whitfield (PI), Mark Hayward, Mark Hill, David Vandenbergh, and George Vogler

Specific Aims

Recently, molecular geneticists have made substantial gains in the mapping of genes involved in disease. However, far fewer advances have been made in understanding how genes combine with environmental factors to influence the population's health and very few studies have focused on minorities. Biodemographic research has begun documenting the role that genetic and environmental factors play in determining health, focusing thus far on functional ability and longevity (Christensen et al. 2002; Christensen et al. 2000; Vaupel et al. 1998). The proposed work builds on this line of inquiry, blending genetic and demographic perspectives to investigate the gene-environment sources of hypertension among African Americans. By focusing on hypertension, this study offers an innovative approach to investigate the forces shaping the most prevalent disease afflicting African Americans, a disease that has significant consequences for functional problems and longevity. Using a population-based sample of African American twins from the "Carolina African American Twin Study of Aging" (CAATSA) (NIA grant # 5-RO1-AG13662), the project's specific aims are to:

1. Identify the contributions of genetic and environmental factors for hypertension. Prior research examining genetic and environment influences on health and longevity has focused on cognitive aging, physical functioning and longevity. Here, we extend the traditional decomposition models to the most prevalent fatal condition in the older population.
2. Examine the prevalence of specific genetic risk factors for hypertension. Molecular research has documented three genes associated with hypertension, yet the prevalence of the genotypes in the population is unknown. Here, we document prevalence in a population-based sample of African American twins in North Carolina.
3. Examine the association between specific genetic factors and hypertension. Aim 1's decomposition approach identifies the contributions of genetic and environmental factors but does not permit an analysis of the strength of association between specific genetic and environmental factors. This aim evaluates whether genetic effects are sufficiently potent such that their influence is evident for a disease that is strongly patterned by SES, family characteristics and health risk behaviors
4. Investigate environmental conditions under which genetic risk factors exert the strongest influence on hypertension. Traditional decomposition models do not provide the flexibility to explore non-linearities in the influences of genetic and environmental effects. Here, we use a multivariate approach to evaluate these non-linearities. Although specific theoretical arguments are absent in the scientific literature, we adopt the double jeopardy hypothesis as an orienting premise and hypothesize that genetic effects are most evident under adverse environmental conditions (e.g., among persons with low levels of education and income).

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