NHLBI Study Finds High-Normal Blood Pressure Increases Cardiovascular Risk

The study found that those with high-normal blood pressure had a 1.5 to 2.5 times greater risk of suffering a heart attack, a stroke, or heart failure in 10 years than those with optimal blood pressure.

While earlier research had shown that high-normal blood pressure increases the risk of cardiovascular death, this study looked at the risk not only of that but also of nonfatal cardiovascular events. The findings support current clinical practice guidelines calling for lowering of high-normal blood pressure.

High-normal blood pressure is a systolic pressure of 130-139 mm Hg and/or a diastolic pressure of 85-89 mm Hg. About 13 percent of Americans have high-normal blood pressure. By contrast, about 23 percent have hypertension, which is a systolic pressure of 140 mm Hg or higher, or a diastolic pressure of 90 mm Hg or higher.

The study used data from the NHLBI-supported Framingham Heart Study, a landmark epidemiological study that began in 1948. Results appear in the November 1, 2001, issue of the New England Journal of Medicine.

“This study underscores that, when it comes to blood pressure, any elevation over normal puts people at a significant cardiovascular risk,” said NHLBI Director Dr. Claude Lenfant. “While more research is needed on this topic, it’s advisable that high-normal blood pressure be treated.” He added that, for most, treatment would consist of such lifestyle changes as following a healthy eating plan lower in saturated fat and cholesterol, choosing foods low in salt and other forms of sodium, losing extra weight, becoming physically active, and limiting alcoholic beverages.

Dr. Ramachandran Vasan, Associate Professor of Medicine at Boston University School of Medicine and a coauthor of the study, agreed: “This finding is important in order to help Americans add healthy years to their life. Anyone with a high-normal blood pressure should undertake lifestyle changes to lower it to a healthier level.

“Older Americans in particular should do this,” Vasan continued, “since they are especially likely to have other cardiovascular disease risk factors, such as high cholesterol and diabetes, which multiply their risk even more.”

The research involved 6,859 men and women of the original Framingham Heart Study and its Offspring Study. When their initial blood pressure measurements were taken, none of the participants had cardiovascular disease or hypertension.

At the outset, about a quarter of the participants had high-normal blood pressure, about a third had normal blood pressure (systolic pressure of less than 130 and diastolic pressure of less than 85 mm Hg), and about two-fifths had optimal blood pressure (systolic pressure of less than 120 mm Hg and diastolic pressure of less than 80 mm Hg).

Participants were followed for about 12 years. During that time, 397 participants had a cardiovascular event, including 72 who died from cardiovascular disease, 190 who had a heart attack, 85 who had strokes, and 50 who had congestive heart failure.

Cardiovascular events were analyzed separately for men and women for three blood pressure categories (optimal, normal, and high-normal), and for two age groups (35-64 years, and 65 years and older).

Results showed a stepwise increase in cardiovascular events across the three blood pressure categories. In women, the 10-year rates of cardiovascular events when adjusted for age differences were 1.9 percent for those with optimal blood pressure, 2.8 percent for those with normal blood pressure, and 4.4 percent for those with high-normal blood pressure. In men, the 10-year rates of cardiovascular events when adjusted for age differences were 5.8 percent for those with optimal blood pressure, 7.6 percent for those with normal blood pressure, and 10.1 percent for those with high-normal blood pressure.

The incidence of cardiovascular events also increased continuously with age. After 10 years of follow-up, the overall risk of cardiovascular disease in those age 35-64 who had high-normal blood pressure was 4 percent for women and 8 percent for men; in those age 65 or older, the overall risk was 18 percent for women and 25 percent for men.