Left ventricular hypertrophy and skin color among American blacks.

The association between skin color, a measure of black-white genetic admixture, and left ventricular hypertrophy was examined in 551 black men and women, from three US cities, who underwent electrocardiography and skin reflectance measurements during 1972-1974. The overall prevalence of left ventricular hypertrophy (Minnesota Code 3-1 or 3-3) was 14% (18% in men; 11% in women). Left ventricular hypertrophy was strongly associated with systolic (p less than 0.001) and diastolic (p = 0.001) blood pressure, but less so with skin color (p = 0.09) [corrected]. The prevalence of left ventricular hypertrophy was 16% in the darkest versus 12% in the lightest quartile of skin color. In a multiple logistic regression model, adjusting for systolic blood pressure and blood pressure medication use, the relation between left ventricular hypertrophy and skin color was insignificant (p = 0.18); the odds ratio of having left ventricular hypertrophy in dark (75th percentile of skin color) versus light (25th percentile) skinned blacks after adjustment for systolic blood pressure, systolic blood pressure medications, age, and sex was 1.2 (95 percent confidence interval 0.8-1.8). Overall, the association between left ventricular hypertrophy and skin color was weak and not statistically significant, suggesting that black individuals do not have a genetic susceptibility to the effects of blood pressure on the myocardium. We did not postulate any significant effect modification of this association by sex. However, the data suggest that the association between skin color and left ventricular hypertrophy may be different between men and women.