Ambulatory hypertension subtypes and 24-hour systolic and diastolic blood pressure as distinct outcome predictors in 8341 untreated people recruited from 12 populations

Abstract

Background: Data on risk associated with 24-hour ambulatory diastolic (DBP24) versus systolic (SBP24) blood pressure are scarce.

Methods and results: We recorded 24-hour blood pressure and health outcomes in 8341 untreated people (mean age, 50.8 years; 46.6% women) randomly recruited from 12 populations. We computed hazard ratios (HRs) using multivariable-adjusted Cox regression. Over 11.2 years (median), 927 (11.1%) participants died, 356 (4.3%) from cardiovascular causes, and 744 (8.9%) experienced a fatal or nonfatal cardiovascular event. Isolated diastolic hypertension (DBP24≥80 mm Hg) did not increase the risk of total mortality, cardiovascular mortality, or stroke (HRs≤1.54; P≥0.18), but was associated with a higher risk of fatal combined with nonfatal cardiovascular, cardiac, or coronary events (HRs≥1.75; P≤0.0054). Isolated systolic hypertension (SBP24≥130 mm Hg) and mixed diastolic plus systolic hypertension were associated with increased risks of all aforementioned end points (P≤0.0012). Below age 50, DBP24 was the main driver of risk, reaching significance for total (HR for 1-SD increase, 2.05; P=0.0039) and cardiovascular mortality (HR, 4.07; P=0.0032) and for all cardiovascular end points combined (HR, 1.74; P=0.039) with a nonsignificant contribution of SBP24 (HR≤0.92; P≥0.068); above age 50, SBP24 predicted all end points (HR≥1.19; P≤0.0002) with a nonsignificant contribution of DBP24 (0.96≤HR≤1.14; P≥0.10). The interactions of age with SBP24 and DBP24 were significant for all cardiovascular and coronary events (P≤0.043).

Conclusions: The risks conferred by DBP24 and SBP24 are age dependent. DBP24 and isolated diastolic hypertension drive coronary complications below age 50, whereas above age 50 SBP24 and isolated systolic and mixed hypertension are the predominant risk factors.

Keywords: ambulatory blood pressure monitoring; blood pressure component; cardiovascular diseases; population.

Figure 1

Incidence of the composite cardiovascular (CV) end point (A) and fatal combined with nonfatal cardiac events (B) in 4 categories of the ambulatory blood pressure. Incidence was standardized to the sex distribution (46.6% women) and mean age (50.8 years) in the whole study population. For each blood pressure category, the number of subjects at risk is given at the beginning of each 4-year interval. The time axis was curtailed at 16 years when ≈10% of participants were still being followed up. Tables III and IV in the online-only Data Supplement provide more detailed information by 2-year intervals up to 22 years on the number of participants at risk, the number of events, and the number of participants no longer followed up. Vertical bars denote the standard error. P values are for the differences across the 4 blood pressure categories.

Figure 2

Ten-year absolute risk of a composite cardiovascular (CV) end point associated with 24-hour diastolic blood pressure (DBP, A) and 24-hour systolic blood pressure (SBP, B) in participants with normal (full line) or elevated (dashed line) systolic pressure (A) or normal or elevated diastolic pressure (B) on ambulatory measurement. The cut-off points for 24-hour hypertension were ≥130 mm Hg systolic and ≥80 mm Hg diastolic, respectively. For each risk function, the number (n) of subjects contributing to the risk function is given. In the Cox regression models, 10-year absolute risk was standardized to the average of the distributions in the whole study population (mean or ratio) of cohort, sex, age, body mass index, smoking and drinking, serum cholesterol, history of cardiovascular disease, and diabetes mellitus. Ne indicates the number of events in each group. P values denote the significance of the independent contribution of diastolic pressure (A) or systolic pressure (B).