Prognostic Effect of the Nocturnal Blood Pressure Fall in Hypertensive Patients: The Ambulatory Blood Pressure Collaboration in Patients With Hypertension (ABC-H) Meta-Analysis

Abstract

The prognostic importance of the nocturnal systolic blood pressure (SBP) fall, adjusted for average 24-hour SBP levels, is unclear. The Ambulatory Blood Pressure Collaboration in Patients With Hypertension (ABC-H) examined this issue in a meta-analysis of 17 312 hypertensives from 3 continents. Risks were computed for the systolic night-to-day ratio and for different dipping patterns (extreme, reduced, and reverse dippers) relative to normal dippers. ABC-H investigators provided multivariate adjusted hazard ratios (HRs), with and without adjustment for 24-hour SBP, for total cardiovascular events (CVEs), coronary events, strokes, cardiovascular mortality, and total mortality. Average 24-hour SBP varied from 131 to 140 mm Hg and systolic night-to-day ratio from 0.88 to 0.93. There were 1769 total CVEs, 916 coronary events, 698 strokes, 450 cardiovascular deaths, and 903 total deaths. After adjustment for 24-hour SBP, the systolic night-to-day ratio predicted all outcomes: from a 1-SD increase, summary HRs were 1.12 to 1.23. Reverse dipping also predicted all end points: HRs were 1.57 to 1.89. Reduced dippers, relative to normal dippers, had a significant 27% higher risk for total CVEs. Risks for extreme dippers were significantly influenced by antihypertensive treatment (P<0.001): untreated patients had increased risk of total CVEs (HR, 1.92), whereas treated patients had borderline lower risk (HR, 0.72) than normal dippers. For CVEs, heterogeneity was low for systolic night-to-day ratio and reverse/reduced dipping and moderate for extreme dippers. Quality of included studies was moderate to high, and publication bias was undetectable. In conclusion, in this largest meta-analysis of hypertensive patients, the nocturnal BP fall provided substantial prognostic information, independent of 24-hour SBP levels.

Keywords: blood pressure; blood pressure monitoring, ambulatory; hypertension; meta-analysis; publication bias.