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New Guidelines
After 25 years of progress in treating and controlling high blood pressure, improvements have begun to slow. Recent data show a slight rise in stroke, increases in kidney disease and heart failure, and a leveling in the death rate from heart disease among U.S. adults.
In response to this troubling trend, the National Heart, Lung, and Blood Institute (NHLBI) has issued new guidelines for the treatment and prevention of hypertension. The report, which was released in November 1997 and is the sixth issued by the agency since 1972, emphasizes lifestyle changes such as losing excess weight, exercising regularly, and eating a diet rich in fruits and vegetables and low-fat dairy foods.
And, for the first time, the NHLBI stratifies patients by blood pressure stage (1, 2, or 3) and into risk groups (A, B, or C). For example, a person with stage 1 hypertension -- 140-159 systolic pressure (the upper number) and 90-99 diastolic (the lower one) -- with no cardiovascular disease, organ damage, or other risk factors (risk group A) is advised to make dietary and exercise changes for a year before turning to medication. The previous guidelines called for initiation of drug therapy after 3-6 months of lifestyle modifications.
About 50 million adults in the United States have high blood pressure readings of 140/90 mm Hg or greater. The systolic reading measures arterial pressure when the heart contracts; the diastolic number is the pressure between heartbeats.
If left untreated, hypertension can lead to kidney disease, stroke, and heart attack. Cardiovascular disease is the leading cause of death among Americans; stroke is the third biggest killer.
Experts believe that many Americans have become complacent about managing their blood pressure because therapy is usually lifelong, some medications have troubling side effects and can be expensive, and hypertension has no symptoms until organ damage occurs.
Now the NHLBI recommends that all Americans -- not just those with hypertension -- follow a diet known as DASH, Dietary Approaches to Stop Hypertension. Low in fat and rich in fruits, vegetables, whole grains, and dairy products, this eating plan significantly and quickly lowered blood pressure in hypertensive participants enrolled in a multicenter study published in the April 17, 1997, issue of the New England Journal of Medicine.
The 459 volunteers were randomly assigned to a control diet based on what most Americans eat (37% of calories from fat); a similar regimen with added fruits and vegetables; or a "combination" diet that contained 2-7% of calories from fat, plenty of fruits and vegetables, grains, low-fat or nonfat dairy products, and small amounts of meat, fish, or poultry, and nuts. (For more detail on the DASH diet, see the Web site http://dash.bwh. harvard.edu).
After following the combination, or DASH, plan for eight weeks, those with hypertension had an average 11.4 mm Hg drop in systolic and 5.5 mm Hg reduction in diastolic pressure -- results comparable to some drug therapies. Participants with borderline-high pressure experienced improvements as well, suggesting that the DASH diet may keep some people from developing hypertension in the first place. The diet higher in fats but also rich in fruits and vegetables also lowered pressure, but not by as much as the DASH plan. All reductions occurred without people changing their salt intake, alcohol consumption, or weight -- factors known to influence blood pressure. (See box.)
When medications are needed, thiazide diuretics or beta-blockers (propranolol, timolol) are recommended as the first line of treatment for hypertension that is not complicated by other diseases. Diuretics lower blood pressure by promoting the excretion of sodium and water by the kidney; beta-blockers decrease the rate and force at which the heart pumps blood into the arteries.
For the first time, the guidelines recommend specific classes of drugs for hypertensive people with various medical conditions. Those with diabetes and accompanying kidney damage should be given ACE inhibitors (captopril, enalapril), which facilitate blood flow by reducing vessel constriction. Heart attack survivors should be treated with beta-blockers and sometimes ACE inhibitors. Heart failure patients should receive ACE inhibitors and diuretics. And people with isolated systolic hypertension, where only the upper number is raised, should start with diuretics. The report advises against using the short-acting calcium channel blocker nifedipine, because some studies suggest that this form of the drug can aggravate or even promote heart problems.
Because African-Americans tend to develop hypertension earlier in life than Caucasians and have higher blood pressure, they and their doctors should be especially mindful of the disease. Blacks have an 80% greater rate of death from stroke and a 50% higher rate of death from heart disease than whites. This group also has an increased sensitivity to salt, and the report recommends that diuretics be used as an initial treatment because they remove salt from the body.
Hypertension is a major risk factor for many serious health problems, so prevention makes a great deal of sense. For those who already have high blood pressure, it is critical to work with a physician to keep pressure down. Prevention and treatment can mean the difference between life and death.
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