Even people whose blood pressure is slightly higher than normal may have a significantly increased risk of stroke, finds a new review of past research.
High blood pressure, or hypertension, is known to be a powerful predictor of a person’s risk of stroke and heart disease. But less has been understood about the health consequences of prehypertension, which affects about one-third of American adults. The new study, published in the journal Neurology, suggests that prehypertensive people have on average a 55% greater risk of stroke than those with normal blood pressure.
Hypertension is defined as having systolic pressure of 140 mm Hg or higher and diastolic pressure of 90 mm Hg or higher. (Systolic pressure, the top number in a blood pressure reading, refers to blood pressure when the heart is pumping; diastolic pressure, the bottom number, refers to pressure between beats.)
Normal blood pressure is systolic pressure below 120 and diastolic pressure less than 80. Prehypertension — a new clinical category introduced by the National Heart, Lung, and Blood Institute in 2003 — falls in between: systolic pressure of 120 to 139 and diastolic pressure of 80 to 89.
But those whose blood pressure registers in the upper half of the prehypertensive range may be at greater risk than those whose pressure is closer to normal. The new study found that the increased stroke risk associated with prehypertension was driven largely by people with systolic pressure of 130 to 139 and diastolic pressure of 85 to 89 — they were 79% more likely to have a stroke than those with normal pressure.
The association wasn’t statistically significant in people in the lower range of prehypertension, the study found.
Further, the elevated risk applied mostly to people younger than 65, who were 68% more likely to have a stroke than those with normal blood pressure. In elderly adults, the association again fell away, probably because the influence of blood pressure was outweighed in this group by risk factors associated with advanced age itself.
The new meta-analysis led by Dr. Bruce Ovbiagele of the University of California, San Diego, included 12 previous studies involving more than 518,000 people in the U.S. and Asia. Participants were followed for anywhere from 3 to 32 years, and the rate of prehypertension in the study groups ranged from 25% to 46%. The association between prehypertension and stroke remained after researchers accounted for other factors like age, sex, diabetes, obesity, cholesterol levels and smoking.
How to treat hypertension? Typically, blood pressure lowering drugs are not recommended, unless prehypertensive patients also have other conditions like diabetes or chronic kidney disease.
The solution is lifestyle changes. If your blood pressure is stealing upward, you should lower the salt in your diet, start exercising and lose weight.