The Effect of Race on Circadian Patterns of Blood Pressure: Results from the Dietary Approaches to Stop Hypertension (DASH) Feeding Study
In most studies, American blacks have a blunted nocturnal decline in BP compared to non-blacks. A major limitation of such analyses has been the inability to control for factors that influence BP (diet, weight, physical activity and socioeconomic status). We used data from the run-in period of the DASH feeding study to determine whether racial differences in circadian BP persist after adjusting for traditional determinants of BP. At end of run-in, a 3 week period when all participants had been fed a common diet (3 gm/d of Na, 1.7 gm/d of K), we obtained ambulatory BP. Participants (198 blacks and 156 non-blacks) had a baseline random-zero SBP <160 and DBP of 80-95 mmHg (mean 131/85 mmHg in both groups). Main results are displayed below. In summary, blacks who had the same baseline BP and who ate the same diet as non-blacks had a blunted nocturnal decline in BP, even after adjustment for other factors that influence BP. Sustained nocturnal BP may partially explain the excess burden of BP-related cardiovascular disease in blacks.