Adult Americans have lowered their cholesterol levels by 3 to 4 percent in recent years, and federal health officials said it has paid off with dramatic reductions in heart-disease deaths.

While the cholesterol levels fell by 3 to 4 percent from 1960 to 1980, the national Centers for Disease Control said death rates from heart disease dropped from 286 deaths per 100,000 population in 1960 to 180 per 100,000 in 1985. That's a one-third reduction."This is the most dramatic trend in death rates in the world, really," the CDC's Dr. Patrick L. Remington said. "The eyes of the entire world scientific community are on the United States because of heart disease deaths going down so rapidly."

About half the decline in coronary deaths could be attributed to changes in lifestyle, Remington said Thursday, "and maybe a third to a quarter to changes in diet," including the consumption of less fatty foods that cause cholesterol buildup in the arteries.

Blood pressure control may account for the remainder of the reduction, he said.

But the CDC said despite the overall improvement in cholesterol levels, there is room for improvement because only 1 in 10 adult Americans know their current cholesterol level.

Cholesterol, a fatty substance present in the blood, is necessary for cell growth. But Remington said that too much cholesterol clogs arteries, causing heart disease.

Over the past 10 years, the association between high levels of cholesterol and increased risk of coronary heart disease "has been well documented," with a 1 percent decline in cholesterol resulting in a 2 percent decline in the risk of cardiovascular disease, the CDC said.

A serum cholesterol level of 240 milligrams per deciliter or greater is considered high, the CDC said, and 200 to 239 is borderline-high. Less than 200 is considered desirable.

A 1987 phone survey of over 40,000 adults in 32 states and the District of Columbia revealed that fewer than 1 in 10 claimed to know their cholesterol value. But despite the disappointing survey results, the CDC said individual cholesterol awareness appears to be increasing.