Ambulatory blood pressure monitoring and risk of cardiovascular disease: a population based study.

BACKGROUND: Information on the relationship between ambulatory blood pressure (BP) and cardiovascular disease in the general population is sparse.

METHODS: Prospective study of a random sample of 1700 Danish men and women, aged 41 to 72 years, without major cardiovascular diseases. At baseline, ambulatory BP, office BP, and other risk factors were recorded. The end point was a combined end point consisting of cardiovascular mortality, ischemic heart disease, and stroke.

RESULTS: After a mean follow-up of 9.5 years, 156 end points were recorded. In multivariate models, the relative risk (95% confidence interval) associated with increments of 10/5 mmHg of systolic/diastolic ambulatory BP were 1.35 (1.21-1.50) and 1.27 (1.16-1.39). The corresponding figures for office BP were 1.18 (1.09-1.29) and 1.11 (1.03-1.19). Compared with normotension (office BP <140/90 mm Hg; daytime BP <135/85 mm Hg) the relative risks associated with isolated office hypertension (office BP >/=140/90 mm Hg; daytime BP <135/85 mm Hg), isolated ambulatory hypertension (office BP <140/90 mm Hg; daytime BP >/=135/85 mm Hg), and sustained hypertension (office BP >/=140/90 mm Hg; daytime BP >/=135/85 mm Hg) were 0.66 (0.30-1.44), 1.52 (0.91-2.54), and 2.10 (1.45-3.06), respectively. A blunted BP decrease at night was a risk factor (P = .02) in subjects with daytime ambulatory hypertension, but not in subjects with daytime ambulatory normotension (P = .13).

CONCLUSIONS: Ambulatory BP provided prognostic information about cardiovascular disease better than office BP. Isolated office hypertension was not a risk factor and isolated ambulatory hypertension tended to be associated with increased risk. A blunted BP decrease at night was a risk factor in subjects with daytime ambulatory hypertension.