Genetic and Environmental Influences on Hypertension, Obesity in African Americans

The subjects studied were all participants in the Howard University Family Study (HUFS), a population based family study of African Americans in the Washington metropolitan area. The major objectives of the HUFS were to: 1) enroll and examine a randomly ascertained cohort of African-American families, along with a set of unrelated individuals, from the Washington DC metropolitan area to study the genetic and environmental basis of common complex diseases including hypertension, obesity and associated phenotypes; 2) to characterize study participants for anthropometry (including weight, height, waist and hip circumferences, body composition measures) and BP; and 3) evaluate the association between genetic variants and selected traits (hypertension, BP and obesity). Participants were sought through door-to-door canvassing, advertisements in local print media and at health fairs and other community gatherings. In order to maximize the utility of this cohort for the study of multiple common traits, families were not ascertained based on any phenotype. During a clinical examination, demographic information was collected by interview. Weight, height, waist circumference and hip circumference were measured using standard methods as follows: Weight was measured in light clothes on an electronic scale to the nearest 0.1 kg, and height was measured with a stadiometer to the nearest 0.1 cm. Body mass index (BMI) was computed as weight in kg divided by the square of the height in meters. Waist circumference was measured to the nearest 0.1 cm at the narrowest part of the torso as seen from the anterior aspect. BP was measured in the sitting position using an oscillometric device (Omron). Three BP readings were taken with a ten minute interval between readings. The reported SBP and DBP readings were the average of the second and third readings. Pulse pressure (PP) was calculated as the difference between the SBP and DBP. Hypertension status was defined as SBP> = 140 mmHg and/or DBP> = 90 mmHg and/or treatment with antihypertensive medication. In the overall cohort, the frequency of hypertension was 35% and among those that were hypertensive, 64% were on antihypertensive medication at the time of the study.