Study Links Salt Sensitivity and Risk of Death

INDIANAPOLIS -- A sensitivity to salt can put individuals at risk of death even if their blood pressure is not elevated, according to a study published Feb. 16 in the Council Supplement of Hypertension, Journal of the American Health Association.

The study is the first to show that salt sensitivity increases the risk of death, as well as other conditions, even for adults with normal blood pressure. Previous studies have found that salt sensitivity increases the risk of death, hypertension, heart attack and other cardiovascular conditions, but this is the first study showing that the risk is increased even for individuals with normal blood pressure.

"Salt Sensitivity, Pulse Pressure, and Death in Normal and Hypertensive Humans," was conducted by researchers at the Indiana University School of Medicine, the Regenstrief Institute for Health Care and the Richard L. Roudebush VA Medical Center. It was funded by the National Heart, Lung and Blood Institute, part of the National Institutes of Health.

"Salt sensitivity increases the risk of death whether or not a person has high blood pressure," says the study's principal investigator Myron Weinberger, M.D., professor of medicine and director of the Hypertension Research Center at IU School of Medicine. "We also found in a prior study that those who were salt sensitive were more likely to develop high blood pressure as they aged. The United States is a 'salt-rich' environment, which exacerbates this problem. Those who are salt sensitive need to take steps to reduce their salt intake and, so, lower their risk of death and cardiovascular diseases."

Salt sensitivity is not the same as the amount of salt ingested; it is a measure of how blood vessels and fluid volume react to salt. In individuals who are salt sensitive, salt intake increases their blood pressure in an exaggerated way and the increased level stays elevated longer.

In this study investigators followed up on individuals who had participated in a hypertension study done more than 25 years ago. The original group included 708 people between the ages of 18 and 80. Of those, researchers located 596 of the original group and, if living, re-examined them. For those deceased, the researchers tried to identify the cause of death and other health problems.

Researchers found that in the 25 intervening years, 123 people or 21 percent of the original group had died from cardiovascular disease or other causes. Participants in the original study who had normal blood pressure but were salt sensitive fared no better than those who were suffered from hypertension. Only those with normal blood pressure who were not salt sensitive at the outset had a significantly better survival rate.

The original study was designed to learn more about the mechanisms involved in how the body controls blood pressure. The current study shows that some of those mechanisms can be life threatening.

"Americans can take advantage of this finding," said Dr. Weinberger. "They don't need to drastically cut back on salt intake to reduce their risk of death or developing hypertension as they age. They will reap the benefit if they reduce their salt intake to 2,400 milligrams a day."

He added that only 10 percent of dietary sodium comes from salt added to food at the table, so people should monitor food labels and note the sodium content in prepared, preserved and processed foods.

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Recipes and suggestions for following a low sodium eating plan are available from the National Health,
Lung and Blood Institute Web site at http://www.nhlbi.nih.gov.

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