The number of Americans killed by strokes each year is declining dramatically, according to data compiled by the National Heart, Lung and Blood Institute, a division of the National Institutes of Health.

The stroke death rate, when adjusted for age changes in the population, has decline 36.1 percent since 1962, with more than two-thirds of that drop occurring since 1972, the year a major, continuing national campaign was begun to identify and treat those suffering from high blood pressure.

Speaking yesterday morning to a meeting of the Black Health Providers Task Force on High Blood Pressure Education and Control, Dr. Robert Levy called the decline one of "gross proportions... One has to give very high credit to increased awareness and attention to high blood pressure.

In the 1940s and 1950s, stroke was declining at about.7 percent a year, and in the 1960s it was declining at about 1.5 percent a year," said Levy, director of the Heart, Lung and Blood Institute.

"In the 1960s we had antihypertensive drugs (medication to lower high blood preasure, or hypertension) introduced for the first time," said Levy, "but the fact is that since 1972, stroke deaths have been declining at an amazing rate, greater han 5 percent a year."

The National High Blood Pressure Education Campaign began in 1972, with announcements on radio, television and in newspapers, and community efforts to make people aware of the perils of high blood pressure -- the so-called "silent killer."

Dr. John Laragh, master professor of medicine at Cornell Medical School and head of the hypertension and cardiovascular center at New York Hospital in New York City, said the decline "is a consequence of the national program to identify and treat high blood pressure.

"I'm sure we're identifying more people with high blood pressure than ever before, and more are being treated," Laragh said.

The sharp decline in stroke-related deaths coincides with an overall decline in deaths due to cardiovascular disease.

It is impossible to say positively that the informational campaign has caused the decline in stroke deaths, Levy conceded. But he pointed out that hypertension is the leading cause of strokes, and visits to physicians for treatment of hypertension have increased 48.5 percent since the beginning of the campaign, while all visits to physicians have increased by only about 5 percent.

According to Dr. William Mroczek, director of the hypertension and hemodynamics laboratory at D.C. General Hospital, "communitywide, the demand for treatment of hypertension is overwhelming. Several people per week spontaneously call the hospital and ask if they can get into the hypertension clinic." The clinic is now caring for 2,500 people, Mroczek said.

There was a "greater than 50 percent decrease in admissions to D.C. General for strokes" between 1972 and 1976, said Mroczek, "but that does not take into account population shifts and declining utilization of the hospital."

Overall admissions to D.C. General declined between 30 and 40 percent during the same period, according Dr. Stanford Roman, the hospital's medical director, but hospital officials say much of that shift has resulted from a decline in admission of patients with less serious illnesses.

One of the "dramatic things" about the national decline in stroke deaths, said Levy, is that it "has declined as precipitously, if not more so, in the nonwhite population as in the white population."

While an estimated 35 million Americans suffer from high blood pressure, the condition is much more common among blacks than whites, and no one really knows why, according to Dr. Charles Curry, chairman of the department of cardiovascular medicine at Howard University Hospital.

"There are certain factors that seem to predispose to hypertension," said Curry, "such as a high salt intake. In areas of the world where they don't use salt, such as among Eskimos, they don't have hypertension. In areas with high salt intake, like Japan," it is a major problem, he said.

There is a theory, said Curry, that more blacks may experience hypertension than whites "because blacks eat a high salt diet. But this is controversial, because in areas of the South studies have shown that whites and blacks eat the same diet, and yet hypertension among blacks in those areas is twice as high as that in whites."

Mroczek believes that blacks have a "genetic predisposition (to develop hypertension) and this is allowed to be expressed by a variety of environmental factors," such as a high salt diet.

It has traditionally been difficult to convince people they need treatment for hypertension because "it is an asymptomatic disease," said Curry. "They have no way to know their blood pressure's high. Once they start to take medication they start feeling bad. They may feel lethargic, tired, they may be dizzy, they may have sexual disfunction," he said.

Properly treated, however, most of the side effects can be eliminated, he said. According to Curry, patients being treated for hypertension should be seen by a physician at least every three months, and everyone else over the age of 40 should have his or her blood pressure checked on an annual basis.