Average cholesterol counts: not low enough.

For decades, doctors have been hammering home the warning that excess cholesterol raises a person's risk of heart disease. Yet epidemiological studies have shown that two-thirds of the people with heart disease in North America have no more than average amounts of cholesterol in their blood.

These studies suggest that the average cholesterol concentration-210 milligrams per deciliter of blood (mg/dl)-is, in fact, too high.

Now a new study, the Cholesterol and Recurrent Events (CARE) trial, powerfully buttresses this view. The study found that heart attack survivors who reduce the cholesterol in their blood below the norm can lower their risk of a repeat heart attack.

"These results demonstrate that for patients with coronary disease in North America, the average cholesterol level is too high and can contribute to the recurrence of cardiovascular events," assert Frank M. Sacks of Harvard Medical School in Boston and his colleagues in the Oct. 3 New England Journal of Medicine.

The 5-year study followed 4,159 heart attack survivors age 21 to 75 at 80 medical centers in the United States and Canada. All of the participants began the trial with near-average concentrations of total cholesterol and of low-density lipoprotein (LDL). LDL is known as bad cholesterol for its deadly propensity to form artery-clogging plaque.

A total of 2,081 participants took 40 milligrams of the cholesterol- lowering drug pravastatin each day. The remainder took a placebo.

Sacks and his colleagues regularly tested the cholesterol in participants' blood. The researchers relied primarily on measurements of LDL to gauge the effectiveness of pravastatin in lowering cholesterol and to assess relative heart disease risk.

They found that pravastatin lowered mean LDL concentrations by 32 percent- from 139 mg/dl to 98 mg/dl. This effect lasted for the full 5 years of the study, and it held the treatment group's average LDL to a concentration 28 percent below that of the placebo group.

This sharp drop paid off in vital ways for people in the treatment group.

Compared with the placebo group, those taking the drug reduced their risk of heart attack by 24 percent, the researchers say.

The rate of fatal heart attacks was 37 percent lower in the treatment group than in the placebo group, the study found. Those who took the drug were also 26 percent less likely to undergo coronary bypass surgery and 23 percent less likely to have artery-clearing balloon angioplasty. Moreover, people taking the drug had 31 percent fewer strokes, according to the report.

Although the benefits of lowering cholesterol were most pronounced in people who began the study with the highest concentrations of LDL in their blood, the benefits also extended to those who had lower LDL concentrations at the outset.

For instance, participants whose initial LDL measurements placed them in the bottom one-third of the group still cut their heart attack rate by 15 percent after they began taking pravastatin. "I think this study should give physicians a lot of impetus to treat their coronary patients with cholesterol-lowering drugs and in general to pay more attention to cholesterol," Sacks says.

Basil Rifkind of the National Heart, Lung, and Blood Institute in Bethesda, Md., concurs. "Most people who have had heart disease should be on cholesterol treatment."

The study does not suggest that people who have not had heart attacks should take cholesterol-lowering drugs. "Whether half the population should be taking pravastatin is another question," Sacks says. Rifkind agrees with that concern about the drug's long-term safety. "This is not a 10-day course of penicillin. When you prescribe these drugs, you're putting patients on them for 10 or 20 years."