Altered circadian blood pressure profile and prognosis.

BACKGROUND: In a previous analysis of the Progetto Ipertensione Umbria Monitoraggio Ambulatoriale we found a higher rate of cardiovascular morbid events among hypertensive nondippers than we did among dippers (5.86 versus 1.18 events per 100 person-years, P = 0.0002) for women, whereas the difference between the two groups was smaller and not statistically significant for men (4.15 versus 2.48 events per 100 person-years). These differences held in a multivariate analysis after adjustment for several confounders including average 24 h ambulatory blood pressure. In another analysis, the rate of occurrence of cardiovascular end-points was higher among nondippers than it was among dippers regardless of the definition of day and night (0600-2200 h and 2200-0600 h, awake and asleep, and 1000-2000 h and 2400-0600 h) and of the dividing line between dippers and nondippers (10 versus 0% day-night difference in blood pressure). OBJECTIVE: To test in a subsequent analysis based on a larger sample and a longer follow-up period, for both sexes, the prognostic value of a blunted diurnal rhythm of blood pressure. METHOD: We used the night: day ratio of ambulatory blood pressure, a continuous and normally distributed variable. RESULTS: A night: day systolic blood pressure ratio > 0.899 for men and > 0.909 for women (upper tertiles of distributions) identified a subset of subjects with greater than normal cardiovascular risk for any level of concomitant risk factors, wherease the hight:day diastolic blood pressure ratio was not statistically significant as an independent predictor. The excess risk for subjects in the upper tertile of the night: day systolic blood pressure ratio held after adjustment for several risk markers, including average 24 h ambulatory blood pressure. CONCLUSION: These data suggest that a blunted reduction in blood pressure from day to night predicts an increased cardiovascular morbidity at any level of concomitant risk factors including average 24 h ambulatory blood pressure. Nondippers can be defined in terms of a night: day ambulatory systolic blood pressure ratio > 0.899 for men and > 0.909 for women, regardless of the diastolic blood pressure profile.