Clinical Question

What is a better predictor of mortality: ambulatory or office-based measurement of blood pressure?

Bottom Line

This study supports the guidelines recommending that treatment decisions be based on ambulatory blood pressure measurements rather than in-office blood pressure results. The difference between the two measurements in this cohort was 19/11 mm Hg, which is enough to change the decision to prescribe a medication at all, or to add a second or third medication. (Level of Evidence = 2b)

Synopsis

How we measure things matters. For example, nonfasting lipid levels are a better predictor of mortality than fasting lipid levels. Recent guidelines for hypertension, including those from the U.S. Preventive Services Task Force, have emphasized the need to confirm elevated blood pressure in most patients using some form of ambulatory blood pressure monitoring. This study used data from a large Spanish hypertension registry to look at the association between clinic blood pressure, ambulatory blood pressure, and mortality. The registry includes adults with an indication for ambulatory blood pressure monitoring, such as suspected white coat hypertension, borderline or labile hypertension, or hypertension refractory to treatment. The registry supplies data on clinic blood pressure, measured by automated devices after five minutes of seated rest, and 24-hour ambulatory blood pressure measurements. These data were linked to national vital statistics databases to determine cardiovascular and all-cause mortality. The analysis was adjusted for comorbidities, age, sex, tobacco use, and body mass index. The mean age of patients was 58 years, 58% were male, and only 11% had a diagnosis of cardiovascular disease. During a median 4.7 years of follow-up, there were a total of 3,808 deaths, including 1,295 cardiovascular deaths. The mean ambulatory blood pressure was 129/76 mm Hg, compared with 148/87 mm Hg in the clinic. The clinic blood pressure was measured by an automated device after five minutes of rest, yet far higher than the ambulatory measurements. In the fully adjusted model that adjusted for clinic blood pressure, the hazard ratio for all-cause mortality was 1.58 (95% confidence interval [CI], 1.56 to 1.60) for the ambulatory systolic blood pressure vs. 1.02 (95% CI, 1.00 to 1.04) for the clinic systolic blood pressure adjusted for ambulatory blood pressure. A similar pattern was seen for diastolic blood pressure. The inflection point for an increase in both cardiovascular and all-cause mortality is at a systolic blood pressure of 140 mm Hg to 160 mm Hg. Mortality was not increased in patients with controlled hypertension but was increased in those with white-coat and masked (i.e., normal in clinic, abnormal at home) hypertension.

Study design: Cohort (prospective)

Funding source: Government

Setting: Population-based

Reference: BanegasJRRuilopeLMde la SierraAet alRelationship between clinic and ambulatory blood-pressure measurements and mortality. N Engl J Med2018;378(16):1509–1520.