Coronary heart disease is a leading killer in the United States and there has been a big push to get people to lower their risk. But a new review casts doubt on whether large-scale interventions to reduce multiple cardiac risk factors really work.

These efforts include programs to reduce cholesterol levels and blood pressure, treat diabetes and encourage people to stop smoking and start exercising.

But although health promotions - like counseling, education and drug therapy - may have small effects on coronary risk factors, they have no clear impact on death rates or disease in large groups of people, found reviewers led by Dr. Shah Ebrahim, a professor of public health at the London School of Hygiene and Tropical Medicine.

Among the 39 studies they analyzed, comprising more than 140,000 patients, Ebrahim and colleagues found some positive results. However, "the small reductions in risk factors may reflect problems with the design of the trials - and consequently did not translate into reductions in morbidity and mortality" in the review population as a whole, Ebrahim said.

One problem may be that changes measured are based on the patients who remained in the study and ignore those who dropped out, the reviewers said.

However, they added, a statistically insignificant - but noteworthy - 10 percent reduction in mortality from heart disease could have been missed because of the way in which the overall review was constructed.

"Despite the very large number of participants in the trials, we cannot exclude a small beneficial effect of this sort of health promotion," Ebrahim said.

The review appeared in The Cochrane Library, published by The Cochrane Collaboration, an international organization that evaluates medical research. These reviews draw their conclusions about best medical practices based on evidence from several clinical studies on a given topic, after the reviewers consider both the content and quality of these studies.

Of the studies, the clearest benefit seen was with the use of drugs for lowering blood pressure and cholesterol. The patients who were at highest risk to begin with were the ones who benefited most, the review found.

Interventions may still be quite beneficial for selected populations, Ebrahim said. People at high risk of coronary heart disease should make every attempt to reduce their risk factors through lifestyle changes and may also need blood pressure and cholesterol-lowering drugs, he added.

People at low or moderate risk may also benefit, but whether this is cost-effective may vary from case to case, Ebrahim said.

"More intensive interventions might be expected to produce better effects, although those used in many of the trials would far exceed what is feasible in routine practice," Ebrahim and colleagues said.

"In a clinical trial, you have adequate infrastructure to see that patient is doing what he is supposed to," said Robert DeBusk, M.D., a professor of cardiovascular medicine at Stanford University School of Medicine. "Clinical trial is not real-world."

In a clinical trial, study coordinators and others check up on patients to see if they are following the intervention protocol, whether it is diet, exercise or drug therapy, DeBusk said. In practice, a physician does not have the time to follow-up like that, he said, and bringing that level of intervention would call for a systemic change in the health care system.

However, he said that care managers - nurses tasked with keeping program patients on track - have been proven to be effective in reducing risk factors and mortality and morbidity.

Coronary heart disease involves blockages or other problems of the coronary arteries, the arteries that supply the heart itself with blood. In England, interventions are now being targeted to the patients who are at greatest risk for heart disease.

Ebrahim S, et al. Multiple risk factor interventions for primary prevention of coronary heart disease. The Cochrane Database of Systematic Reviews 2006, Issue 4.

The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit cochrane for more information.