FDA Consumer magazine
July-August 2003 Issue

Research Notebook

New Guidelines Set Lower Mark for High Blood Pressure

The National Heart, Lung, and Blood Institute (NHLBI) has set a new "prehypertension" level of any reading above 120 over 80 mm Hg as part of its new guidelines for the prevention, detection, and treatment of high blood pressure. The new category affects about 22 percent of Americans, or 45 million people.

The guidelines, approved by the Coordinating Committee of the NHLBI's National High Blood Pressure Education Program (NHBPEP), also streamline the steps by which doctors diagnose and treat patients and recommend diuretics as part of the treatment plan for high blood pressure in most patients.

"We also now know that damage to arteries begins at fairly low blood pressure levels--those formerly considered normal and optimal," NHLBI Director Claude Lenfant, M.D., said in announcing the guidelines. "In fact, studies show that the risk of death from heart disease and stroke begins to rise at blood pressures as low as 115 over 75, and that it doubles for each 20 over 10 millimeters of mercury (mm Hg) increase."

The guidelines were prepared by a special NHBPEP committee representing 46 professional, voluntary, and federal organizations and were reviewed by 33 national hypertension experts and policy leaders. The NHBPEP issues new guidelines when warranted by scientific advances. The last guidelines were issued in November 1997.

Results of more than 30 clinical studies worldwide, many of which were funded by the NHLBI, were considered in revising the guidelines.

"These findings have been remarkably consistent in demonstrating the critical importance of lowering blood pressure, irrespective of age, gender, race, or socio-economic status," says Aram V. Chobanian, M.D., dean of the Boston University School of Medicine and chair of the committee that produced the guidelines. "The data allow us to create a set of recommendations that are easier to use than past guidelines, which should in turn make it easier for clinicians to treat their patients' hypertension."

Titled "The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure," the guidelines were published in the May 21, 2003, issue of the Journal of the American Medical Association.

High blood pressure is a major risk factor for heart disease and the chief risk factor for stroke and heart failure, and also can lead to kidney damage. It affects about 50 million Americans--1 in 4 adults.

Treatment seeks to lower blood pressure to less than 140 mm Hg systolic and less than 90 mm Hg diastolic for most people. Treatment for those with diabetes and chronic kidney disease aims to lower blood pressure to less than 130 systolic and less than 80 diastolic.

The guidelines include new data on U.S. control, awareness, and treatment rates for high blood pressure. According to a national survey, 70 percent of Americans with high blood pressure are aware of it, 59 percent are being treated for it, and 34 percent have it under control. Those percentages represent a slight improvement over the rates a decade earlier, when 68 percent of Americans were aware of their high blood pressure, 54 percent were being treated for it, and 27 percent had it under control.

"Though improved, the treatment and control rates are still too low," says Chobanian. "The guidelines stress that most patients will need more than one drug to control their hypertension and that lifestyle measures are a crucial part of treatment."

Another key factor is the need for health care providers to pay more attention to systolic blood pressure in people age 50 and older. "From mid-life on, systolic hypertension is a more important cardiovascular risk factor than diastolic," Chobanian says.

Key aspects of the new guidelines include:

A new "prehypertension" level and merging of other categories.

The new guidelines change the former blood pressure definitions to: normal, less than 120 mm Hg systolic and less than 80 mm Hg diastolic; prehypertension, 120-139 mm Hg systolic and 80-89 mm Hg diastolic; stage 1 hypertension, 140-159 mm Hg systolic and 90-99 mm Hg diastolic; stage 2 hypertension, at or greater than 160 mm Hg systolic and at or greater than 100 mm Hg diastolic.

The guidelines do not recommend drug therapy for those with prehypertension unless it is required by another condition, such as diabetes or chronic kidney disease. But the report advises them--and encourages those with normal blood pressures--to make any needed lifestyle changes. These include losing excess weight, becoming physically active, limiting alcoholic beverages, and following a heart-healthy eating plan, including cutting back on salt and other forms of sodium. The report also recommends that people quit smoking.

As in the 1997 guidelines, the new report recommends that Americans follow the DASH (Dietary Approaches to Stop Hypertension) eating plan, which is rich in vegetables, fruit, and non-fat dairy products. Clinical studies have shown that DASH significantly lowers blood pressure. The decreases are often comparable to those achieved with blood pressure-lowering medication.

Simplified and strengthened drug treatment recommendations.

The guidelines recommend use of a diuretic, either alone or in combination with another drug class, as part of the treatment plan in most patients. The report notes that even though many studies have found diuretics to be effective in preventing hypertension's cardiovascular complications, they currently are not being used sufficiently.

The guidelines also list other drug classes that have been shown to be effective in reducing hypertension's cardiovascular complications: angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers, beta blockers, and calcium channel blockers. The report also gives the "compelling indications"--or high-risk conditions--for which such drugs are recommended as initial therapy.

Use of additional drugs for severe hypertension or to lower blood pressure to the desired level.

Most people will need two, and at times three or more, medications to lower blood pressure to the desired level.

The guidelines also recommend that clinicians work with patients on blood pressure goals and a treatment plan.

To raise awareness about the dangers of high blood pressure, the NHLBI is developing special Web pages and educational materials for health care professionals, patients, and the public. These include an updated "Your Guide To Lowering High Blood Pressure" Web page, which can be found at www.nhlbi.nih.gov/hbp/.

"The bottom line is that Americans must change how they think about blood pressure," says Ed Roccella, M.D., NHBPEP coordinator. "The sooner they take action, the better. It's vital that they adopt a heart-healthy lifestyle early, even if their blood pressure is normal."

Study: Tight Glucose Control in Diabetes Lowers Risk of Atherosclerosis

Strict glucose control in type 1 diabetes reduces the risk of atherosclerosis, a benefit that persists for years, according to a study published in the June 5, 2003, issue of The New England Journal of Medicine.

Since 1993, when the Diabetes Control and Complications Trial (DCCT) ended, researchers have known that intensive glucose control greatly reduces the eye, nerve, and kidney damage of type 1 diabetes. Now, researchers conclude, the benefits of tight control also extend to the heart.

"Intensive control is difficult to achieve and maintain, but its benefits are even greater than we realized," says study chair Saul Genuth, M.D., of Case Western University in Cleveland. "The earlier intensive therapy begins and the longer it can be maintained, the better the chances of reducing the debilitating complications of diabetes."

The DCCT was a multicenter study that compared intensive treatment with conventional management of blood glucose in 1,441 people with type 1 diabetes. Intensive treatment involves at least three insulin injections a day or an insulin pump and frequent self-monitoring of blood glucose. The goal of intensive treatment is to keep hemoglobin A1c (HbA1c), which reflects average blood sugar levels over 60 to 90 days, as close to normal (6 percent) as possible. Conventional treatment at the time of the DCCT consisted of one or two insulin injections a day with daily urine or blood glucose testing.

After six and one-half years of the DCCT, HbA1c levels averaged 7 percent in the intensively treated group and 9 percent in the conventionally treated group. When the DCCT ended, those who had been assigned to conventional treatment were encouraged to adopt intensive control and were shown how to do it. Researchers then began a long-term follow-up study of the participants, called the Epidemiology of Diabetes Interventions and Complications (EDIC) study.

The DCCT could not study atherosclerosis because the participants were relatively young, and heart disease takes years to develop. In 1994-1995 and again in 1998-2000, EDIC researchers used ultrasound to measure the thickness of participants' carotid arteries, the two blood vessels in the neck that carry blood from the heart to the brain. Carotid wall thickness reflects the amount of atherosclerosis, or plaque build-up, in the artery. The thicker the arterial wall the greater the risk of later heart attack and stroke.

At the time of their first ultrasound, the diabetic participants' carotid wall thickness was similar to that of non-diabetic controls matched for age and gender. Five years later, however, the participants had thicker arterial walls than those of the non-diabetic group. In addition, the thickness of the carotid walls had increased less in the intensively treated group during the five years than in the conventionally treated group. "This finding strongly suggests that atherosclerosis progressed more slowly in the intensively treated group," noted Genuth.

Carotid thickening was also linked to known cardiovascular risk factors, including age, higher systolic blood pressure, smoking, LDL to HDL cholesterol ratio, and urinary albumin (a measure of kidney function). After adjusting for these factors, the researchers found that the differences in carotid wall thickness between the two groups were due to the differences in blood glucose levels during the DCCT.

"Now we know that intensively controlled glucose significantly reduces the atherosclerosis underlying heart disease just as it reduces damage to the eyes, nerves, and kidneys in people with type 1 diabetes," says David Nathan, M.D., of Massachusetts General Hospital, who co-chaired the DCCT-EDIC research group. "What's striking is that the benefits of intensive control persisted, despite a gradual rise in the HbA1c levels of the intensively treated group during the five years after DCCT ended."

Diabetes prevention is a major initiative of the Department of Health and Human Services.

About 17 million people in the United States have diabetes. About 1 million have type 1 diabetes. Formerly known as juvenile onset or insulin-dependent diabetes, type 1 diabetes usually begins in children and adults under age 30.

Type 2 diabetes accounts for up to 95 percent of all diabetes cases. Most common in adults over age 40, type 2 diabetes affects 6 percent of the U.S. population. It is strongly associated with obesity (more than 80 percent of people with type 2 diabetes are overweight), inactivity, and family history of diabetes, and is higher in some racial or ethnic groups. The prevalence of type 2 diabetes has tripled in the last 30 years, due in large part to the upsurge in obesity.

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