July 17, 2019

Both systolic and diastolic blood pressures independently predicted the risk of heart attack or stroke in a large Kaiser Permanente Northern California study that included more than 36 million blood pressure readings from over 1 million people.

“This research brings a large amount of data to bear on a basic question, and it gives such a clear answer,” said lead author Alexander C. Flint, MD, PhD, a TPMG neurosurgeon at KP Redwood City and adjunct researcher with the Division of Research. “Every way you slice the data, the systolic and diastolic pressures are both important.”

“Effect of Systolic and Diastolic Blood Pressure on Cardiovascular Outcomes,” by Flint et al., was published Wednesday in the New England Journal of Medicine.

Decades of research have shown that high systolic blood pressure is more likely to result in adverse outcomes. As a result, cardiology guidelines and risk estimation tools focus on that number, with some experts arguing that the diastolic number might reasonably be ignored, Dr. Flint said.

The current retrospective study is “the largest by far of its kind,” Dr. Flint said, reviewing 36 million blood pressure readings taken during outpatient visits between 2007 and 2016, from 1.3 million adult Kaiser Permanente members in Northern California.

After adjusting the data for possible confounding factors, the researchers found that while systolic pressure has a greater impact, both systolic and diastolic pressures strongly influenced the risk of heart attack or stroke, regardless of the definition used for high blood pressure (140/90 mm Hg vs. 130/80 mm Hg).

Dr. Flint said the finding that systolic and diastolic hypertension have similar impacts on risk at the lower threshold of 130/80 provides independent support for recent changes that were made in the American College of Cardiology and American Heart Association guidelines, which recommended tighter blood pressure control in higher risk patients with hypertension. The results are also in keeping with findings from the National Institutes of Health’s Systolic Blood Pressure Intervention Trial (SPRINT).

“Controversy has long persisted about whether systolic blood pressure, diastolic blood pressure, or both contribute to cardiovascular risk,” said senior author Deepak L. Bhatt, MD, MPH, executive director of Interventional Cardiovascular Services at Brigham and Women’s Hospital and professor of Medicine at Harvard Medical School. “This analysis using a very large amount of longitudinal data convincingly demonstrates that both are important, and it shows that in people who are otherwise generally healthy, lower blood pressure numbers are better.”

The Kaiser Permanente Northern California Community Benefit Program supported this study.

In addition to Drs. Flint and Bhatt, co-authors were Carol Conell, PhD, with the DOR and Drs. Xiushui Ren, Nader Banki, Sheila Chan, Vivek Rao, and Ronald Melles, all of The Permanente Medical Group.

This article originally appeared in Division of Research