Effects of smoking and smoking cessation on lipids and lipoproteins: Outcomes from a randomized clinical trial

BackgroundThe effects of smoking and smoking cessation on lipoproteins have not been studied in a large contemporary group of smokers. This study was designed to determine the effects of smoking cessation on lipoproteins.MethodsThis was a 1-year, prospective, double-blind, randomized, placebo-controlled clinical trial of the effects of 5 smoking cessation pharmacotherapies. Fasting nuclear magnetic resonance spectroscopy lipoprotein profiles were obtained before and 1 year after the target smoking cessation date. The effects of smoking cessation and predictors of changes in lipoproteins after 1 year were identified by multivariable regression.ResultsThe 1,504 current smokers were (mean [SD]) 45.4 (11.3) years old and smoked 21.4 (8.9) cigarettes per day at baseline. Of the 923 adult smokers who returned at 1 year, 334 (36.2%) had quit smoking. Despite gaining more weight (4.6 kg [5.7] vs 0.7 kg [5.1], P < .001], abstainers had increases in high-density lipoprotein cholesterol (HDL-C) (2.4 [8.3] vs 0.1 [8.8] mg/dL, P < .001), total HDL (1.0 [4.6] vs −0.3 µmol/L [5.0], P < .001), and large HDL (0.6 [2.2] vs 0.1 [2.1] µmol/L, P = .003) particles compared with continuing smokers. Significant changes in low-density lipoprotein (LDL) cholesterol and particles were not observed. After adjustment, abstinence from smoking (P < .001) was independently associated with increases in HDL-C and total HDL particles. These effects were stronger in women.ConclusionsDespite weight gain, smoking cessation improved HDL-C, total HDL, and large HDL particles, especially in women. Smoking cessation did not affect LDL or LDL size. Increases in HDL may mediate part of the reduced cardiovascular disease risk observed after smoking cessation.