The value of ambulatory blood pressure in older adults: the Dublin outcome study

Background: ambulatory blood pressure (ABPM) appears to be a more accurate predictor of cardiovascular outcome than blood pressure (BP) measured in the clinic setting in younger adults. Objectives: the purpose of this study was to determine if ABPM predicted total and cardiovascular mortality independently of clinic BP and other cardiovascular risk factors in those aged 65 years and over. Methods: one thousand one hundred and forty-four individuals aged 65 and over referred to a single BP clinic had 24-h ABP measurement and clinic measurement at baseline off treatment. There were 385 deaths (of which 246 were cardiovascular) during a mean follow-up period of 6.7 years. Results: with adjustment for gender, age, risk indices and also for clinic BP, a higher mean value of ABPM was an independent predictor of cardiovascular mortality. The relative hazard ratio for each 10-mmHg rise in systolic blood pressure (SBP) was 1.10 (1.06-1.18, P < 0.001) for daytime and 1.18 (1.11-1.25, P < 0.001) for night-time SBP. The hazard ratios for each 5-mmHg rise in diastolic blood pressure (DBP) were 1.05 (1.00-1.10, P=NS) for daytime and 1.09 (1.04-1.14, P < 0.001) for night-time diastolic pressure. The hazard ratios for night-time ABPM remained significant after adjustment for daytime ABPM. Conclusions: ambulatory measurement of BP is superior to clinic measurement in predicting cardiovascular mortality in elderly subjects. Night-time BP is the strongest predictor of outcome in this age group.