Systolic blood pressure levels among adults with hypertension and incident cardiovascular events: the atherosclerosis risk in communities study

Abstract

Importance: Studies document a progressive increase in heart disease risk as systolic blood pressure (SBP) rises above 115 mm Hg, but it is unknown whether an SBP lower than 120 mm Hg among adults with hypertension (HTN) lowers heart failure, stroke, and myocardial infarction risk.

Objective: To examine the risk of incident cardiovascular (CV) events among adults with HTN according to 3 SBP levels: 140 mm Hg or higher; 120 to 139 mm Hg; and a reference level of lower than 120 mm Hg.

Design, setting, and participants: A total of 4480 participants with HTN but without prevalent CV disease at baseline (years 1987-1989) from the Atherosclerosis Risk in Communities Study were included. Measurements of SBP were taken at baseline and at 3 triennial visits; SBP was treated as a time-dependent variable and categorized as elevated (≥140 mm Hg), standard (120-139 mm Hg), and low (<120 mm Hg). Multivariable Cox regression models included baseline age, sex, diabetes status, BMI, high cholesterol level, smoking status, and alcohol intake.

Main outcomes and measures: Incident composite CV events (heart failure, ischemic stroke, myocardial infarction, or death related to coronary heart disease).

Results: After a median follow-up of 21.8 years, a total of 1622 incident CV events had occurred. Participants with elevated SBP developed incident CV events at a significantly higher rate than those in the low BP group (adjusted hazard ratio [HR], 1.46; 95% CI, 1.26-1.69). However, there was no difference in incident CV event-free survival among those in the standard vs low SBP group (adjusted HR, 1.00; 95% CI, 0.85-1.17). Further adjustment for BP medication use or diastolic BP did not significantly affect the results.

Conclusions and relevance: Among patients with HTN, having an elevated SBP carries the highest risk for cardiovascular events, but in this categorical analysis, once SBP was below 140 mm Hg, an SBP lower than 120 mm Hg did not appear to lessen the risk of incident CV events.

Figure 1. Adjusted Hazard Ratios (HRs) of Incident Cardiovascular Events by Time-Varying Systolic Blood Pressure (SBP) Level Category Among Participants With Hypertension

The Atherosclerosis Risk in Communities Study (1987–2010) stratified by composite event (heart failure, ischemic stroke, or combination measure myocardial infarction/incidence of coronary heart disease death [MI/CHD]) (A), heart failure (B), ischemic stroke (C), and MI/CHD (D). Elevated BP is defined as an SBP of 140 mm Hg or higher; standard BP, an SBP of 120 to 139 mm Hg; and low BP, an SBP of lower than 120 mm Hg. The vertical lines through the HRs represent 95% CIs.

Figure 2. Unadjusted Cardiovascular Event-Free Survival Among Participants With Hypertension by Systolic Blood Pressure (SBP) Category

The Atherosclerosis Risk in Communities Study (1987–2010) stratified by composite event (heart failure, ischemic stroke, or combination measure myocardial infarction/incidence of coronary heart disease death [MI/CHD]) (A), heart failure (B), ischemic stroke (C), and MI/CHD (D). Elevated BP is defined as an SBP of 140 mm Hg or higher; standard BP, an SBP of 120 to 139 mm Hg; and low BP, an SBP of lower than 120 mm Hg.