While high blood pressure is considered the most important risk factor for strokes, new findings target even slightly high blood pressure as a danger.
People whose blood pressure was above normal -- known as pre-hypertension -- were 55% more likely to have a stroke compared with people with normal blood pressure, according to an analysis of 518,520 adults involved in 12 studies on blood pressure and stroke occurrence. The report was published Wednesday online in Neurology. One in three adults in the USA has pre-hypertension.
The authors suggest treatments more aggressive than altering lifestyle might be necessary if future studies support the findings.
Current treatments for lowering pre-hypertension, defined by a systolic blood pressure (when the heart is pumping) of 120-139 or a diastolic blood pressure (when the heart is at rest) of 80-89, include losing weight, exercising, reducing salt intake and stopping smoking. In addition, physicians might recommend drug therapy for patients with pre-hypertension plus other diseases, including prediabetes and diabetes.
The findings are adding to discussions about when to start drug intervention, according to Seemant Chaturvedi, a doctor not associated with the study.
Normal blood pressure is below 120 (systolic) and below 80 (diastolic). Medicine for lowering blood pressure isn't typically started until patients have hypertension -- blood pressure that is 140/90 or higher.
But the numbers for hypertension could fall. This kind of adjustment happened with total cholesterol numbers: 240, once considered an ideal total number, gradually dropped to below 200.
"It could be similar to what happened with cholesterol numbers," says Chaturvedi, director of the stroke program at Wayne State University and a fellow of the American Academy of Neurology. "Everyone knows those have been ratcheted down."
Pre-hypertension was classified in 2003 by the National Heart, Lung, and Blood Institute's National High Blood Pressure Education Program. Experts flagged it as a precursor to hypertension -- but not a risk factor for stroke -- and called for more studies on the condition. The 12 studies reported on were all completed after 2003.
Other findings:
People younger than 65 with pre-hypertension were nearly 68% more likely to have a stroke compared with those with normal blood pressure.
The risk for people whose blood pressure was in the 130-139 range was 79% higher than those with normal blood pressure.
"Pre-hypertension is very controversial,'' says the study's lead author, Bruce Ovbiagele, director of the stroke prevention program at the University of California-San Diego. "When it was first classified, people accused the experts of creating a fake class of people all needing to be on drugs.''
Physician Karen Furie, who was not associated with study, said in an e-mail that the 55% risk of stroke is moderate and that pre-hypertension is a "very plausible" risk factor for stroke, adding that it often leads to hypertension.
"The significance of this paper is that it represents the synthesis of roughly a half-million subjects,'' says Furie, a fellow of the American Academy of Neurology. "The conclusions appropriately call for additional studies."
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