Randomized controlled smoking cessation study: transient increase in plasma high density lipoprotein but no change in lipoprotein oxidation resistance

Low plasma levels of high density lipoprotein (HDL) and high levels of low density lipoprotein (LDL) as well as smoking are known risk factors in coronary heart disease. It has been suggested that oxidative modification renders LDL atherogenic. We investigated the influence of smoking cessation on plasma lipid and lipoprotein levels and on the ability of lipoproteins to resist oxidation in vitro (lag time). A total of 182 healthy smokers who smoked more than 15 cigarettes per day were randomized to stop smoking (smoking cessation group, n = 100) or to continue smoking for 4 weeks (control group, n = 82). The smoking cessation group was followed up after 26 weeks. After 4 weeks, the HDL level had increased from mean +/- SD 1.36 +/- 0.34 to 1.48 +/- 0.40 mmol l-1 (p < 0.001) in 62 successful quitters, while levels were unchanged in the control group (72 subjects in per-protocol analysis). However, after 26 weeks there was no change in HDL (1.34 +/- 0.36 vs. 1.36 +/- 0.35 mmol l-1) in 29 subjects from the smoking cessation group who fulfilled the study. Plasma levels of very low density lipoprotein (VLDL), LDL, total cholesterol, triglycerides and oxidation resistance of VLDL + LDL did not show significant changes any time during the study for either group. Thus, plasma levels of lipids and lipoproteins as well as oxidation resistance of lipoproteins seem unaffected by smoking cessation for 26 weeks.