Salt Sensitivity Increases Heart Disease Death Risk
Oct. 25, 2000 (Washington) -- For the first time, scientists have shown that a sensitivity to salt can almost double the risk of dying from a heart attack. An estimated one out of four people is salt-sensitive, but the condition is most common in the elderly, African-Americans, and those with high blood pressure.
"What we found was even in those people who were normal when they were initially studied, but had salt sensitivity, their risk of death was the same as if they were hypertensive," Myron Weinberger, MD, professor of medicine at the Indiana University School of Medicine, tells WebMD.
The study was presented here Wednesday at the 54th Annual Fall Conference of the American Heart Association's Council for High Blood Pressure Research. It follows research Weinberger did back in the '70s that opened the door to understanding the phenomenon of salt sensitivity. What Weinberger did then was give study participants a high dose of salt for a day, then rapidly purge it out. If a person's blood pressure dropped more than 10 mm/Hg in the process, the individual was classified as salt-sensitive.
Weinberger decided he would perform a follow-up on the 708 people in the original study to learn what happened to them. He found that 123 of the 596 he tracked had died, more than half from heart attacks and strokes.
"So there's something about salt sensitivity which increases the risk of at least death, and we think ... other cardiovascular events. ... Now the question is why," Weinberger says. Salt sensitivity remains largely a mystery. It may have a genetic origin, or it may by the result of a subtle kidney or blood pressure disorder.
However, it also can be a problem for those people thought to be healthy. "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," Weinberger says. But it's not the kind of problem that's likely to show in a typical doctor visit.
"If it can be determined that someone is salt-sensitive, and then they reduce their salt intake, it may be possible that they can prevent the subsequent development of these events," Weinberger says.
In fact, measuring salt sensitivity turns out to be something of a challenge. A blood pressure reading known as pulse pressure, a number derived by subtracting the low (systolic) number from the high (diastolic) one, didn't turn out to be an accurate death predictor as once thought.
However, correcting the sensitivity problem may not be all that difficult. Weinberger suggests looking carefully at food labels and aiming for a 50% reduction in salt consumption. The American Heart Association's dietary guidelines recommend moderate use of salt and sodium.