Prognostic value of nighttime blood pressure in the elderly: A prospectivestudy of 24-hour blood pressure

Although it has been suggested in several reports that 24-h ambulatory bloo d pressure(BP) is a better predicter than casual BP measured in a clinician 's office of the incidence of cardiovascular (CV) events, little informatio n is available concerning the prognostic value of nighttime BP in the elder ly population. Therefore, to evaluate the clinical implications of the nigh ttime BP in the elderly, we prospectively followed-up 324 elderly individua ls (mean age, 77.2 +/- 7.0 years) who had undergone ambulatory BP monitorin g at an annual health examination over a mean follow-up period of 51.5 +/- 22.0 months, and the relationship between BP and CV events was analyzed usi ng Cox's proportional hazard model. For the analysis, 310 participants, exc luding 14 subjects who were withdrawn due to non-CV events, were classed in to two groups, one consisting of 134 individuals who were undergoing treatm ent with an anti-hypertensive drug(medicated group) and another consisting of 176 who were not medicated (nonmedicated group). New cardiovascular even ts developed in 43 cases in the medicated group and in 14 cases in the non- medicated group during the follow-up period. In the medicated group, a line ar relationship was observed be tween BP and the event rates. The hazard ra tio for CV events adjusted for age, sex, and other cardiovascular risks was 1.28 (95% confidence interval [CI], 1.05 to 1.54, p < 0.05) for a 10 mmHg increase of 24-h systolic BP. Corresponding values in 24-h diastolic BP, ni ghttime systolic BP, and nighttime diastolic BP were 1.71 (1.19 to 2.46, p < 0.01), 1.34 (1.13 to 1.58, p < 0.01), and 1.67 (1.20 to 2.31, p < 0.01), respectively. In the non-medicated group, the event rate was least in the s ubgroup in the second-lowest quartile for nighttime systolic BP, with a sli ght non-significant increase in the subgroup of the lowest quartile. It was shown that insufficient control of nighttime BP in the elderly with hypert ension is associated with the development of CV complications.