High blood pressure should be treated earlier with lifestyle changes and in some patients with medication—at 130/80 mm Hg rather than 140/90—according to the first comprehensive new high blood pressure guidelines in more than a decade. The guidelines were published by the American Heart Association (AHA) and the American College of Cardiology (ACC) for detection, prevention, management and treatment of high blood pressure.

The guidelines were presented at the Association’s 2017 Scientific Sessions conference, the premier global cardiovascular science meeting for the exchange of the latest advances in cardiovascular science for researchers and clinicians.

Rather than 1 in 3 U.S. adults having high blood pressure (32%) with the previous definition, the new guidelines will result in nearly half of the U.S. adult population (46%) having high blood pressure, or hypertension. However, there will only be a small increase in the number of U.S. adults who will require antihypertensive medication, authors said. These guidelines, the first update to offer comprehensive guidance to doctors on managing adults with high blood pressure since 2003, are designed to help people address the potentially deadly condition much earlier.

The new guidelines stress the importance of using proper technique to measure blood pressure. Blood pressure levels should be based on an average of two to three readings on at least two different occasions, the authors said.

High blood pressure accounts for the second largest number of preventable heart disease and stroke deaths, second only to smoking. It’s known as the “silent killer” because often there are no symptoms, despite its role in significantly increasing the risk for heart disease and stroke.

Paul K. Whelton, MB, MD, MSc, lead author of the guidelines published in the American Heart Association journal, Hypertension journal and the Journal of the American College of Cardiology, noted the dangers of blood pressure levels between 130-139/80-89 mm Hg.

“You’ve already doubled your risk of cardiovascular complications compared to those with a normal level of blood pressure,” he said. “We want to be straight with people—if you already have a doubling of risk, you need to know about it. It doesn’t mean you need medication, but it’s a yellow light that you need to be lowering your blood pressure, mainly with non-drug approaches.”

Blood pressure categories in the new guideline are:

• Normal: Less than 120/80 mm Hg;
• Elevated: Top number (systolic) between 120-129 and bottom number (diastolic) less than 80;
• Stage 1: Systolic between 130-139 or diastolic between 80-89;
• Stage 2: Systolic at least 140 or diastolic at least 90 mm Hg;
• Hypertensive crisis: Top number over 180 and/or bottom number over 120, with patients needing prompt changes in medication if there are no other indications of problems, or immediate hospitalization if there are signs of organ damage.

The new guidelines eliminate the category of prehypertension, which was used for blood pressures with a top number (systolic) between 120-139 mm Hg or a bottom number (diastolic) between 80-89 mm Hg. People with those readings now will be categorized as having either Elevated (120-129 and less than 80) or Stage I hypertension (130-139 or 80-89).

Previous guidelines classified 140/90 mm Hg as Stage 1 hypertension. This level is classified as Stage 2 hypertension under the new guidelines.

The impact of the new guidelines is expected to be greatest among younger people. The prevalence of high blood pressure is expected to triple among men under age 45, and double among women under 45 according to the report. Damage to blood vessels begins soon after blood pressure is elevated, said Whelton, who is the Show Chwan professor of global public health at Tulane University School of Public Health and Tropical Medicine and