Both Blood Pressure Numbers Matter, New Study Finds

Decades of advice are overturned, doubling the number of numbers to worry about.

As if understanding blood pressure wasn’t confusing enough, a new study suggests doctors and patients need to relearn half of what had been the common wisdom. For decades, health professionals have instructed people to worry about the upper number, called the systolic reading, and not to worry too much about the lower number, called the diastolic reading.

Worry about both, researchers now say. The results affect nearly half of U.s. adults who, by current definitions, have high blood pressure.

The change is based on a review of more than 36 million blood-pressure readings from 1.3 million people and their health outcomes over time—the largest study of its kind, the researchers say.

“This research brings a large amount of data to bear on a basic question, and it gives such a clear answer,” said the study’s lead author Alexander Flint, a stroke specialist at Kaiser Permanente, a conglomerate that runs hospitals and offers health plans. “Every way you slice the data, the systolic and diastolic pressures are both important.”

Systolic pressure, the upper number, measures how hard the heart works.

Diastolic pressure measures the pressure on the arteries as the heart rests between beats.

Until now, some experts were still arguing “that the diastolic number might reasonably be ignored,” Flint said. High systolic pressure does have a greater impact on negative health outcomes, the study finds, but “both systolic and diastolic pressures strongly influenced the risk of heart attack or stroke.” And that’s true whether the measurements are 140/90 or 130/80, meaning anything at those levels or higher is cause for concern.

The findings, detailed in the July 18 issue of the New England Journal of Medicine, are seen as confirming the recently revised minimum threshold for high blood pressure, also called hypertension.

In 2017, the American College of Cardiology and American Heart Association announced new, lower numbers (130/80) as the threshold for hypertension, versus the previous minimum threshold of 140/90. “The…