The researchers found that high normal blood pressure can damage the kidney's ability to clear toxins from the blood. In addition, they found this level of blood pressure can cause an enlarged heart, which increases the likelihood of heart failure.
The study is being presented this week at the American Heart Association's annual High Blood Pressure Research Conference in Washington, D.C.
It's more evidence of increased risk for people with a borderline form of high blood pressure called prehypertension, a new category the AHA established earlier this year.
Anyone with a systolic (top number) reading of 120 or over, or a diastolic (bottom) reading of 80 or over is considered high-normal or prehypertensive. These people are at increased risk of heart disease and stroke, says the AHA.
An estimated 23% of the population has prehypertension. An additional 25% or more have full-blown high blood pressure.
Increased Risk to Organs
In this study of 265 people with normal blood pressure, 108 had blood pressure in the "high-normal" prehypertensive range, reports Pierre Fesler, a researcher with Hospital Lapeyronie in Montpellier, France.
In follow-up examinations, he saw a trend that as blood pressure increased, so did the likelihood of kidney and heart damage. In fact:
- 7% of people with optimal blood pressure (less than 120/80) had some organ damage.
- 13% with normal pressure (less than 130/85) had some damage.
- 23% with high-normal pressure (130-139/85-89) had damage.
Of 28 patients he followed for about six years, 13 of 16 with high-normal blood pressure became hypertensive -- which also seems to be a trend, Fesler reports. Patients with this level of high blood pressure also showed signs of kidney and heart damage, he adds.