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Delaying the onset of high blood pressure may lower the risk of a stroke, new research suggests.

The study, published Monday in the ľ¹ÏÖ±²¥ journal , found the longer participants had high blood pressure, the greater their risk for stroke and the greater their need for blood pressure-lowering medications. Stroke risk was higher regardless of whether high blood pressure was treated.

"So much of the effort to prevent stroke has focused on blood pressure treatment," said the study's lead author Dr. George Howard, an emeritus distinguished professor of biostatistics at the University of Alabama at Birmingham. "While that's an incredibly important thing to do, we need to shift attention back to efforts to prevent high blood pressure from ever developing."

Nearly half of U.S. adults have high blood pressure, or hypertension, which occurs when the force of blood pushing against the walls of the blood vessels is too strong. It is a major risk factor for heart attacks and strokes.

Blood pressure is considered high in a teen or adult when the systolic, or top number, is at least 130 millimeters of mercury (mmHg) or the diastolic, the bottom number, is at least 80 mmHg. Normal blood pressure is less than 120/80 mmHg. Many people don't realize their blood pressure is too high because there often aren't any symptoms.

The new study followed 27,310 adults in the U.S. for a median of 12.4 years. Their average age was 65.

The longer someone lived with hypertension, the more classes of high blood pressure medications they needed to take. People who had hypertension for 21 years or more were taking 2.28 classes of drugs on average compared to 1.68 classes of medication for those who'd had hypertension for five years or less.

Stroke risk also rose as the years of living with high blood pressure added up, even after researchers adjusted for factors that could have affected the findings, such as whether participants reported using medications to control their high blood pressure. People who had hypertension for up to five years were 31% more likely to have a stroke than people without the condition. Those who had it for six to 20 years were 50% more likely to have a stroke, and those who had high blood pressure for more than two decades were at 67% greater risk for a stroke than participants with normal blood pressure.

The new findings magnify the urgency of identifying and managing any blood pressure issues early – before hypertension develops, said Dr. Shawna Nesbitt, medical director at Parkland Health's Hypertension Clinic and a professor in the department of internal medicine at UT Southwestern Medical Center, both in Dallas.

"It's the duration of exposure to this high pressure that is damaging," said Nesbitt, who was not involved in the study.

Preventing strokes as a consequence of prolonged hypertension could reap a wealth of benefits that extend beyond an individual's health, she said.

"The cost of a stroke is incredibly high," Nesbitt said. "It can cause disability that is lifelong. Treating and controlling blood pressure earlier saves more than the cost of treatment; it prevents the disability that is incurred by people who have strokes and the subsequent loss of quality of life, often including their ability to work. It's the long-term care following a stroke that really affects people and their families."

To make sure blood pressure stays within the normal range, the AHA recommends eating a healthy diet, limiting alcohol, maintaining a healthy weight, managing stress, staying physically active, not smoking and taking medications if needed.