The goal of this study is to characterize the effect of skin pigmentation on serum 25- hydroxycholecalciferol (vitamin D) levels, and, in turn, ascertain their association with blood pressure among women as they age. This doctoral research will test hypothesized relationships of skin color and vitamin D with blood pressure using existing data, repository resources, and newly-acquired data from the Study of Women's Health Across the Nation (SWAN). Literature suggests that vitamin D regulates the renin-angiotensin system and, by extension, blood pressure. Skin melanin content determines the amount of Vitamin D conversion via ultraviolet blue. Persons geographically distant from the equator seasonally lack ultraviolet-blue for adequate vitamin D synthesis, which compounds the decline in vitamin D production and absorption with age. These findings form the basis for the hypothesis that a missing link in the racial disparity in blood pressure is that many African Americans, who largely have darker skin than whites, obtain insufficient sunlight due to geographical location and limited outdoor exposure which, leads to inadequate vitamin D for healthy regulation of blood pressure. This is compounded by the effects of aging. The study will be implemented in SWAN, an ongoing multi-ethnic, multi-site longitudinal community-based study of women (aged 42-52 at baseline) recruited at seven United States sites, now in its 13th year. This study will use Michigan site data where the sample includes 218 white and 325 black women. Available resources include blood pressures, food frequency, dietary supplement history, and serum samples available to evaluate vitamin D. Interview-based measures of body exposure to sunlight and reflectometer-determined skin coloration will be ascertained for this doctoral research. Repeated measures analysis will be used to address within-subject correlations. Understanding the intersection of skin color, behavioral factors and chronic disease risk is important in addressing underlying causes of race/ethnic disparities in blood pressure.
This study will combine blood pressures, food frequency, dietary supplement history from existing data, serum samples to assay vitamin D from repository resources, and newly-acquired skin color data from the longitudinal, multi-ethnic Study of Women's Health Across the Nation (SWAN) to characterize the effect of skin pigmentation on serum 25-hydroxycholecalciferol (vitamin D) and blood pressure among women as they age.
