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High blood pressure of any kind in young adults increases the risk of heart attacks, strokes and other cardiovascular events, according to new findings that shed light on an issue experts say has been understudied.

Blood pressure readings have two measurements. Systolic is the top number and indicates how much pressure the blood exerts against artery walls while the heart beats. Diastolic blood pressure is the bottom number that gauges the pressure between beats. High blood pressure is defined as a systolic reading of 130 or higher or a diastolic reading of 80 or higher, according to guidelines from the American College of Cardiology and ľ¹ÏÖ±²¥.

In young adults, researchers wanted to know which measurement is more important in predicting future cardiovascular disease risk: systolic, diastolic or both?

"The answer is, all of the above," said Dr. Donald Lloyd-Jones, a coauthor of the study and chair of preventive medicine at Northwestern University Feinberg School of Medicine in Chicago.

The study, published Monday in the AHA journal , used information from a Korean database of more than 6 million people ages 20 to 39. Researchers analyzed the risk of heart attack, stroke, heart failure or cardiovascular-related death during 13 years of follow-up.

Those with only high systolic blood pressure between 130-139 had a 36% increased risk compared to those with normal blood pressure. High diastolic blood pressure between 80-89 elevated risk by 32%. For people with both high systolic and high diastolic measurements, risk rose 67%.

"There has been real debate within the community whether modest elevations of systolic blood pressure mean anything in terms of risk in this younger age group," Lloyd-Jones said. "This is new and important information, and we have not had this much data on this population before."

The findings, he said, demonstrate the need to categorize young adults with high blood pressure as having high systolic, high diastolic or both to better pinpoint those at high risk who would benefit from lifestyle changes or blood pressure-lowering medications.

The study fills knowledge gaps about hypertension in the younger age group, said Dr. Joseph Flynn, a professor of pediatrics at the University of Washington School of Medicine in Seattle.

"There's a lot we know about outcomes of hypertension in middle-age and older adults, and there's a pretty good amount of data in hypertension in childhood. But there's a dearth of data for what you do with a 20- or 25-year-old with high blood pressure," said Flynn, who was not involved in the research. "This is exactly the group we need information about."

Yet questions remain. Only 40% of study participants had normal blood pressure, which Flynn said seems very low. "That was definitely striking." As was, he said, how many participants – about 50% to 60% – reported getting no exercise.

Even so, given the large population studied and the number of years they were followed, the findings are of significant value to the medical community, Flynn said.

Lloyd-Jones said he hopes the research provides a springboard for other scientists to examine high blood pressure in young adults more carefully and in other racial and ethnic groups.

"This study shows that the more evidence we see, the more important this issue becomes," he said. "We don't want to unnecessarily label people as hypertensive, but we don't want to miss warning signs either."

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