Ethnic differences in nocturnal blood pressure decline in treated hypertensives

Lack of a nocturnal decline in blood pressure (BP) has been associated with more severe end organ damage in hypertensives, and blacks appear less likely than whites to have a > 10% drop in nighttime BP ("dipping"). Little information is available about the relationship between treatment regimens, ethnic group classification, and dipping in treated hypertensive patient populations. We obtained 24-h ambulatory BP readings in 438 adult white (n = 103), black (n = 200) and Hispanic (n = 135) treated hypertensives. Tycos monitors were connected in patients' homes before their usual morning medication dose time. Research assistants administered a quality-of-life questionnaire, recorded patients' drug regimen, and observed the patients take their morning dose. Monitors were programmed to record BP every 30 min. Dippers were defined as persons who had a drop of > or = 10% decline in average daytime (08:00 to 22:00) compared to nighttime (00:00 to 04:00) BP. Logistic regression modeling was used to assess the relationship between demographic and treatment variables and probability of dipping. Twenty-four-hour average BP was similar in all three ethnic groups. However, the absence of a systolic dip was significantly more common in black and Hispanic men than in white men (OR black v white = 11.54, 95% CI = 3.92 to 34.01; OR Hispanic v white = 7.32, 95% CI = 2.47 to 21.68). There were no ethnic group differences in probability of systolic dipping among women. Absence of a diastolic dip was approximately twice as common in blacks and Hispanics than in whites, with no marked gender-by-ethnic-group interaction in the magnitude of the association. Of the 10 most commonly prescribed antihypertensives, no single drug was positively associated with nocturnal BP decline. Later versus earlier morning dose time, but not once-a-day dosing, was associated with absence of dipping. Treated black and Hispanic hypertensives are less likely to "dip" than non-Hispanic whites. No particular drug was positively associated with dipping.