What is the evidence that raising HDL cholesterol levels reduces the risk of CHD?
A low concentration of HDL cholesterol, especially if accompanied by elevations of plasma total cholesterol or triglyceride, is a powerful predictor of premature CHD. Studies of people who are free of CHD (primary prevention), such as in the Helsinki Heart Study, suggest that the incidence of future cardiac events may be reduced by raising HDL levels in people who have low HDL concentrations. The people with the highest coronary risk in the Helsinki Heart Study were those in whom mild to moderate elevations of plasma triglyceride and plasma total cholesterol were accompanied by reduced levels of HDL cholesterol. Treatment with gemfibrozil resulted in an increase in HDL cholesterol, a decrease in the levels of plasma triglyceride and plasma total cholesterol and a 65% reduction in the incidence of cardiac events.3 There is also evidence that interventions which increase the level of HDL cholesterol are of benefit to patients who already have CHD (secondary prevention). In one such secon
