Genetic Ancestry, Social Classification, and Racial Inequalities in Blood Pressure in Southeastern Puerto Rico (Gravlee et al. 2009)

I had posted when this appeared in AAPA 2008, and now the full paper has been published.

Figure 1 shows the relationship between "color" and genetic ancestry. As can be seen, the "color" categories overlap in terms of genetic ancestry, even though their averages are in the right order:

The paper is a powerful reminder that social race is not the same as genomic ancestry, and that racial disparities in an observable trait do not necessarily reflect differential genetic proclivities.

PLoS ONE 4(9): e6821. doi:10.1371/journal.pone.0006821

Genetic Ancestry, Social Classification, and Racial Inequalities in Blood Pressure in Southeastern Puerto Rico

Clarence C. Gravlee et al.

Abstract

Background

The role of race in human genetics and biomedical research is among the most contested issues in science. Much debate centers on the relative importance of genetic versus sociocultural factors in explaining racial inequalities in health. However, few studies integrate genetic and sociocultural data to test competing explanations directly.

Methodology/Principal Findings

We draw on ethnographic, epidemiologic, and genetic data collected in southeastern Puerto Rico to isolate two distinct variables for which race is often used as a proxy: genetic ancestry versus social classification. We show that color, an aspect of social classification based on the culturally defined meaning of race in Puerto Rico, better predicts blood pressure than does a genetic-based estimate of continental ancestry. We also find that incorporating sociocultural variables reveals a new and significant association between a candidate gene polymorphism for hypertension (α2C adrenergic receptor deletion) and blood pressure.

Conclusions/Significance

This study addresses the recognized need to measure both genetic and sociocultural factors in research on racial inequalities in health. Our preliminary results provide the most direct evidence to date that previously reported associations between genetic ancestry and health may be attributable to sociocultural factors related to race and racism, rather than to functional genetic differences between racially defined groups. Our results also imply that including sociocultural variables in future research may improve our ability to detect significant allele-phenotype associations. Thus, measuring sociocultural factors related to race may both empower future genetic association studies and help to clarify the biological consequences of social inequalities.

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