HIGH-DENSITY-LIPOPROTEIN CHOLESTEROL ELEVATION WITH GEMFIBROZIL - EFFECTS OF BASE-LINE LEVEL AND MODIFYING FACTORS

The effects of baseline level and modifying factors on gemfibrozil-ind uced high-density lipoprotein (HDL) cholesterol elevation were studied in 1028 participants with good compliance in the Helsinki Heart Study . The absolute (mmol/L) increment in HDL cholesterol was independent o f baseline when the change in the placebo group (regression toward the mean) was considered. In contrast, absolute reductions in low-density lipoprotein (LDL) cholesterol and triglycerides correlated with their baselines, relative percentage changes being constant. Statistically, this could indicate differences in the mode of action of gemfibrozil: an independent and additive effect on HDL cholesterol and a multiplic ative effect on LDL cholesterol and triglycerides. These differences m ay have a physiologic background because the main effect of gemfibrozi l is in the stable HDL3 subfraction, rather than in the variable HDL2. Only 13% of the variation in gemfibrozil-induced HDL cholesterol chan ges were explained by modifying factors. The bask assumptions in the u ses of absolute or relative changes as a measure of treatment effect a rc discussed.