NOCTURNAL BLOOD-PRESSURE IN TREATED HYPERTENSIVE AFRICAN-AMERICANS COMPARED TO TREATED HYPERTENSIVE EUROPEAN-AMERICANS

Previous studies have shown that African Americans (blacks) tend to ha ve higher nocturnal blood pressure than European Americans (whites). T he study presented here was undertaken to determine whether treatment of hypertension influences nocturnal blood pressure differently in bla cks than in whites. To answer this question, this study measured noctu rnal blood pressure by ambulatory blood pressure monitoring (ABPM) in treated hypertensive blacks and whites whose daytime blood pressures w ere comparable. Inclusion criteria for this study were: diagnosis of e ssential hypertension, absence of renal failure, and documentation of antihypertensive therapy, diabetic status, proteinuria status, and bod y weight. All of the black patients in our programs who underwent ABPM and met the above criteria were included in this study. White patient s were included on the basis of having the same inclusion criteria as blacks and showing, by ABPM, daytime mean arterial pressure (MAP) in t he same range as that of the blacks selected for this study, The resul ts of nocturnal blood pressure were unknown to the investigators when the patients were selected for this study. In the blacks (N = 62) and whites (N = 72) selected for study, the mean daytime (0600 to 2200 h) MAP was 107 +/- 1 SE mm Hg for both the black and white cohorts, To as sess nocturnal blood pressure, the period from 0100 to 0500 h was chos en because it likely encompassed an interval of sleep, which is associ ated with the nadir of nocturnal blood pressure. This interval was ter med 0100 to 0500 h, ''middle night.'' Mean middle night MAP was 97 +/- 12 mm Hg in blacks versus 90 +/- 14 mm Hg in whites (P < 0.006, unpai red t test), The greater middle night MAP in blacks compared with whit es was a result of the higher diastolic pressure in blacks (80 +/- 11 mm Hg) versus whites (75 +/- 11 mm Hg) (P = 0.003). Mean middle night systolic blood pressure was numerically higher in blacks than whites ( 131 +/- 18 mm Hg versus 128 +/- 17 mm Hg), but this difference did not achieve statistical significance. The higher middle night blood press ure in blacks versus whites could not be explained by differences betw een the groups in daytime MAP, age, gender, body weight, serum creatin ine level, proteinuria, diabetic status, or greater use of short-actin g antihypertensive agents in blacks versus whites. It was concluded th at when treated hypertensive blacks and whites are matched for the sam e daytime blood pressure, blacks tend to have significantly higher noc turnal blood pressure than whites. The magnitude of this difference su ggests that it could contribute importantly to the greater target-orga n damage that is seen in hypertensive blacks compared with hypertensiv e whites.