Study: Prehypertension raises stroke risk 55 to 79 percent

Kathleen Blanchard's picture
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People with higher, but what is considered normal blood pressure readings, known as prehypertension, are found to have a 55 percent higher risk for future stroke compared to people with lower blood pressure.

For those whose blood pressure is still considered normal, but in the higher range, the chance of stroke increases 79 percent, in a study that researchers say is “groundbreaking”.

The health threat of stroke from prehypertension, blood pressure that is between120 and 139 mmHg systolic (the top number) and a diastolic reading between 80 and 89 mm Hg (the bottom number), has not been well studied.

Researchers have now identified 12 studies - four from the United States, five from Japan, two from China and one from India, that show higher risk of stroke from “normal”, but higher blood pressure.

According to Bruce Ovbiagele, MD, professor of neurosciences at UC San Diego School of Medicine and senior author of the study,

"This result held regardless of sex, race-ethnicity, blood pressure type (systolic or diastolic) or the type of stroke (ischemic or hemorrhagic)."

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Ischemic stroke occurs from lack of blood flow to the brain and is the most common cause of strokes. Hemorrhagic stroke is the result of sudden bleeding from a weakened blood vessel, according to the American Heart Association, accounting for approximately 13 percent of occurrences.

Ovbiagele explains:

"Prehypertension has been controversial since its inception, with occasional accusations that it would not be used to diagnose sick people, but rather it would label healthy people whose blood pressure was towards the upper reaches of normal as unhealthy, without any compelling reason for doing so.

Others complained that the new designation would needlessly expose people to blood pressure-reduction drugs, all to the benefit of pharmaceutical companies."

Until now there was no evidence that prehypertension might increase the chance of stroke. Clinicians have recently followed guidelines recommending treatment for systolic blood pressure if it is over 115 systolic.

Thomas Hemmen, MD, PhD, director of the UC San Diego Stroke Program and a neurologist at the UC San Diego Sulpizio Cardiovascular Center, not involved in the study, described the finding as “groundbreaking”.

The study, published in the journal Neurology, shows the importance of curbing unhealthy behaviors like high salt intake, smoking, sedentary lifestyle and obesity. Blood pressure drugs to lower prehypertension are not yet recommended until larger studies are done.

The finding clarifies that blood pressure in the normal range, but considered prehypertension – between 120 and 130 for the top number and 80 to 89 for the bottom number – can be a significant risk factor for future stroke, raising the chances as much as 79 percent. The researchers suggest even young people should monitor their blood pressure on a regular basis.

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