Skin color, ethnicity, and blood pressure I: Detroit blacks.

Census areas in Detroit were ranked for their stress scores based on instability (e.g., crime, marital break up) and socioeconomic status. Four areas were selected for detailed study: 1) high stress, population predominantly black, 2) white, 3) low stress, population predominantly black, 4) white. A sample was drawn from each area of persons of the predominant race, 25-60 years old, married and living with spouse, and having relatives in the Detroit Area. Nurses interviewed such persons; three blood pressure readings were taken during the first half-hour of medical history, and skin color was rated. Results show that darker skin color, for black males especially, is related to higher pressure, independently of nine control variables (e.g., age, weight, socioeconomic status, etc.). However, younger black males (25-39 years of age) in high stress areas had higher pressure than counterparts in low stress areas, regardless of skin color and relative weight; for older black males (40-59 years of age) darker skin color was correlated with higher pressure, regardless of relative weight or stress area. For 35 blacks whose fathers were from the West Indies, pressures were higher than those with American-born fathers. These findings suggest that varied gene mixtures may be related to blood pressure levels and that skin color, an indicator of possible metabolic significance, combines with socially induced stress to induce higher blood pressures in lower class American blacks.