FOR RELEASE:1:30 p.m. ET, WednesdayOctober 25, 2000
CONTACT:Maggie Francis (214) 706-1397
Carole Bullock (214) 706-1279[email protected]
Abstract 36
American Heart Association meeting report: Watching salt intake isn't just for those with high blood pressure
WASHINGTON, Oct. 25 -- For the first time researchers have shown that people who are salt sensitive -- including those who do not yet have high blood pressure -- may have an increased risk of death, according to a study reported today at the 54th Annual Fall Conference of the American Heart Association's Council for High Blood Pressure Research.
The study is the first to show that salt sensitivity is a risk factor for death from cardiovascular disease independent of other risk factors such as smoking or high cholesterol. Salt sensitivity is a measure of how blood pressure responds to sodium. "We also found that the survival rate of salt-sensitive people with normal blood pressure is no better than people with hypertension," says lead author Myron H. Weinberger, professor of medicine and director of the Hypertension Research Center at the Indiana University School of Medicine. "We are hoping to find out why."
Researchers determined salt sensitivity by first giving participants an intravenous salt solution and measuring their blood pressure. One day later, individuals were given a diuretic drug along with a very low salt diet -- which depletes the body's salt stores -- and had their blood pressure measured again. If blood pressure fell by 10 mm/Hg or more between the salt-infusion period and the period of salt depletion, a person was classified as salt-sensitive.
Weinberger's team investigated 708 individuals who had participated in a study they conducted in the early 1970s. That study was the first to show that salt sensitivity, which is linked to hypertension, also occurs in people with normal blood pressure.
Of the original study's participants, between ages 18 and 80 at the time, 278 had hypertension and 430 had normal blood pressure. The team traced 596 of the volunteers; 473 were alive and 123 had died. They could not locate 112 participants. Heart attacks and strokes caused more than half the deaths.
In their analysis, the team found that each year of age increased the risk of death 3 percent, but that salt-sensitive people had double the risk of death compared with those who were not salt sensitive.
"It has been suggested that salt is not an important factor in human disease," says Weinberger. "Every bit of evidence that we have indicates that salt sensitivity can be a very important determinant of future hypertension and future cardiovascular disease risk."
Weinberger and his colleagues are now investigating whether salt-sensitive people with normal blood pressure are more likely to develop hypertension. The researchers are trying to determine how many people in their original study later developed high blood pressure.
"Our preliminary study showed that normal individuals who are salt sensitive have an increase in blood pressure over a period of at least 10 years that is eight times greater than those who are salt resistant," says Weinberger. "When we are finished, we believe this study will give us definitive information about whether salt sensitivity predicts hypertension with increasing age."
This study also found that high pulse pressure alone may not be a risk factor for death. When age and systolic pressure were considered, pulse pressure was no longer independently associated with risk of death.
Pulse pressure is the difference between the top (systolic) and bottom (diastolic) numbers of a blood pressure measurement. A person with a blood pressure of 120/80 mm/Hg would have a pulse pressure of 40. A high pulse pressure is typically considered 50 or 60 and above, and is often a reflection of an increase in systolic pressure due to stiff blood vessels, says Weinberger.
Another finding from this group was that high levels of renin -- an enzyme made in the liver that helps regulate blood pressure -- had a protective effect. The higher the renin level, the less likely people were to die.
Co-authors of the study are Naomi S. Fineberg, Ph.D.; Morris Weinberger, Ph.D.; and S. Edwin Fineberg, M.D.
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NR00-1201 (HBP/Weinberger)
Dr. Myron Weinberger can be reached by phone at (317) 274-8153; by fax at (317) 278-0673; or by e-mail at [email protected]. (Please do not publish phone numbers or e-mail address.)
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