July 18 (UPI) -- Having either a high top or bottom number of a blood pressure reading can each predict cardiovascular risk, a new study says.
The systolic and the diastolic readings -- which are the top and bottom numbers -- both independently forecast the risk of heart attack and stroke, according to research published Thursday in New England Journal of Medicine. This contradicts a long-held belief that only the top number matters.
The systolic number represents the force with which the heart pumps blood into the arteries, while the diastolic number shows pressure on the arteries in between pumps.
The researchers say some past research even recommended ignoring the diastolic number completely.
"There has been a pendulum-swing over the years toward the view that systolic hypertension is the only thing that matters when it comes to conveying a risk of adverse outcomes like heart attack or stroke," Alexander C. Flint, a stroke specialist at Kaiser Permanente and study lead author, told UPI. "I decided to use the 'big data' available in Kaiser Permanente to address this important issue -- do systolic and diastolic hypertension both contribute to cardiovascular risk?"
For the study, the researcher examined more than 36 million blood pressure readings from 1 million Kaiser Permanente patients in Northern California between 2007 and 2016.
The study's findings apply whether a high blood pressure read at 140/90 mmHg or 130/80 mmHg. The American College of Cardiology and American Heart Associate recently changed its guidelines to define high blood pressure as anything over 130/80mmHg.
"Because we find that both systolic and diastolic blood pressure convey risk above each of the thresholds for hypertension in the new AHA/ACC guidelines, we also hope that our results will serve to underscore the importance of following these guidelines by identifying patients with hypertension who are at higher risk so that their blood pressure can be more tightly controlled," Flint said.