Effects of Timing and Extent of Smoking, Type of Cigarettes, and Concomitant Risk Factors on the Association Between Smoking and Subclinical Atherosclerosis

Abstract

Background and Purpose— The purpose of this study was to evaluate the effects of timing and extent of smoking, type of cigarettes, and concomitant vascular risk factors (VRFs) on the association between smoking and carotid intima-media thickness (C-IMT) in a lipid clinic population. Methods— 1804 patients (869 men, age 21 to 85 year) participated in the study. Smoking habits were recorded and C-IMTs were measured by B-mode ultrasound. The associations of C-IMT with smoking status (never, former, and current) and with the cigarettes’ content of tar, nicotine, and carbon monoxide (alone or combined to define “light” or “regular” cigarettes) as well as the interactions between smoking status, gender, and VRFs were evaluated before and after adjustment for confounders. Results— C-IMT was highest in current smokers, lower in former, and lowest in never smokers. C-IMT of former and current smokers differed only after data adjustment for variables describing the extent and timing of smoking exposure. C-IMT was positively related to the number of pack-years (number of cigarettes smoked per day [cigarettes/d] multiplied by number of years smoked/20) in both former and current smokers. There were no differences in C-IMT between smokers of cigarettes with high or low nicotine, tar, or carbon monoxide content. Both diabetes and hypertension interacted positively with smoking in determining C-IMTs. Conclusions— In the present cross-sectional observational investigation, carried out in a cohort of patients attending a lipid clinic, consumption of light cigarettes does not reduce the atherogenic effect of smoking on C-IMT. The number of pack-years, cigarettes/d, and years of smoking are relevant covariates in evaluating the effects of smoking on vascular health. The presence of diabetes or hypertension strengthens the association between smoking and cardiovascular risk.