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.