How high is too high when it comes to blood pressure? New research suggests a reading a few points below the official benchmark for high blood pressure significantly increases the risk of heart attacks and strokes.

"The lower your blood pressure, the better off you are," said one of the researchers, Dr. Ramachandran Vasan, of Boston University School of Medicine. "Our findings emphasize the need for people to maintain optimal levels of blood pressure."

The study of 6,859 men and women in today's New England Journal of Medicine concluded those with so-called high-normal blood pressure are two to three times more likely to have a heart attack, stroke or heart failure in 10 years than those with what is considered optimal or ideal blood pressure.

About 13 percent of adults in the United States have hypertension, or high blood pressure, and 19 percent have high-normal blood pressure, Vasan said.

"Individuals with high-normal blood pressure are a large chunk of the population and physicians need to share this information with them; that there is now data to suggest they could be at increased risk," he said.

The findings do not mean the 20 million Americans with high-normal readings should start taking drugs, Vasan said.

"We support the recommendation that you should adopt nonpharmacological measures to reduce it," he said, such as eating a diet low in saturated fats and salts, and high in grains, fruits and vegetables.

Blood pressure is the force of blood in the arteries and is measured in two numbers. The high number, systolic, is the pressure when the heart contracts. The lower number, diastolic, is the pressure between beats when the heart relaxes.

High blood pressure is above 140 over 90; high-normal is 130-139 over 85-89; normal is 120-129 over 80-84 and optimal is less than 120 over 80.

Those with high-normal blood pressure are often older, overweight, have high cholesterol or diabetes — all possible contributors to heart disease, Vasan said.

Current guidelines suggest diet and exercise to lower high-normal blood pressure. Vasan said research is needed to determine whether more aggressive treatment, including medication, is warranted.

However, the finding "that high-normal blood pressure is more akin to high blood pressure than it is to normal pressure is an important advance," said Dr. Julio Panza, of Washington Hospital Center in Washington, D.C.

If studies show treatment is beneficial, the threshold for treating blood pressure with medications could be lowered, Panza wrote in an accompanying editorial.

"Depending on what other studies in the future show, it may have a significant implication," Panza said.

The study funded by the National Heart, Lung and Blood Institute reviewed data from the Framingham Heart Study, which has followed participants from the Boston suburb for more than 50 years.

Vasan and his colleagues looked at groups of patients, excluding those with high blood pressure or heart disease. They followed the rest for 12 years to find the rate of heart attack, stroke or heart failure.

Of those with high-normal blood pressure, 4 percent of the women and 8 percent of the men under 65 had an incident. In older participants, 65 to 90, the rate was 18 percent for women and 25 percent for men.  {probably over a 10 year time period}

The researchers calculated the women were about three times more likely and the men were about two times more likely to have a cardiovascular event than those with optimal blood pressure.

Abstract from NE Journal of Medicine Nov 1, 2001

Ramachandran S. Vasan, M.D., Martin G. Larson, Sc.D., Eric P. Leip, M.S., Jane C. Evans, Ph.D., Christopher J. O'Donnell, M.D., M.P.H., William B. Kannel, M.D., M.P.H., and Daniel Levy, M.D.

Methods We investigated the association between blood-pressure category at base line and the incidence of cardiovascular disease on follow-up among 6859 participants in the Framingham Heart Study who were initially free of hypertension and cardiovascular disease.

Results A stepwise increase in cardiovascular event rates was noted in persons with higher base-line blood-pressure categories. The 10-year cumulative incidence of cardiovascular disease in subjects 35 to 64 years of age who had high-normal blood pressure was 4 percent (95 percent confidence interval, 2 to 5 percent) for women and 8 percent (95 percent confidence interval, 6 to 10 percent) for men; in older subjects (those 65 to 90 years old), the incidence was 18 percent (95 percent confidence interval, 12 to 23 percent) for women and 25 percent (95 percent confidence interval, 17 to 34 percent) for men. As compared with optimal blood pressure, high-normal blood pressure was associated with a risk-factor–adjusted hazard ratio for cardiovascular disease of 2.5 (95 percent confidence interval, 1.6 to 4.1) in women and 1.6 (95 percent confidence interval, 1.1 to 2.2) in men.

Conclusions High-normal blood pressure is associated with an increased risk of cardiovascular disease. Our findings emphasize the need to determine whether lowering high-normal blood pressure can reduce the risk of cardiovascular disease.