Systolic, diastolic blood pressures show independent effects on MI, stroke risk
Although systolic blood pressure was the more significant factor, the finding that both measures independently predict adverse outcomes suggests that diastolic pressure should not be ignored, study authors said.
Systolic and diastolic hypertension independently influence the risk of adverse cardiovascular events, regardless of the threshold of hypertension, with the former having greater effect, a study found.
Researchers analyzed data from more than 1.3 million participants and nearly 36.8 million blood pressure measurements in a large, integrated health care delivery system in Northern California. The primary outcome was the effect of systolic and diastolic hypertension on a composite outcome of myocardial infarction (MI), ischemic stroke, or hemorrhagic stroke over an eight-year period. Results were published in the July 18 New England Journal of Medicine.
There were 24,681 MIs, 16,271 ischemic strokes, and 3,334 hemorrhagic strokes. In survival models, both systolic hypertension (≥140 mm Hg; hazard ratio per unit increase in z score, 1.18 [95% CI, 1.17 to 1.18]) and diastolic hypertension (≥90 mm Hg; hazard ratio per unit increase in z score, 1.06 [95% CI, 1.06 to 1.07]) independently predicted the composite outcome. Similar results were seen using the lower threshold of hypertension (≥130/80 mm Hg) defined in the 2017 U.S. hypertension guidelines.
Systolic hypertension of at least 140 mm Hg had a greater effect on adverse outcomes among participants in the lowest quartile of diastolic blood pressure (hazard ratio per unit increase in z score, 1.21; 95% CI, 1.20 to 1.23; P<0.001) than it did among participants in the highest quartile of diastolic blood pressure (hazard ratio per unit increase in z score, 1.16; 95% CI, 1.15 to 1.17; P<0.001). Similar results were seen when systolic hypertension was at least 130 mm Hg (hazard ratio per unit increase in z score, 1.25; 95% CI, 1.23 to 1.27; P<0.001)
“Hypertension guidelines include both systolic and diastolic blood-pressure targets,” the authors wrote. “Despite this, it has been argued, on the basis of data from the Framingham Heart Study, that treatment for hypertension could improve with measurement of only systolic blood pressure. Our results show that this would be inappropriate: although systolic blood pressure indeed had a greater effect, systolic and diastolic blood pressures each independently influenced cardiovascular outcomes, and therefore diastolic blood pressure ought not to be ignored.”