Longitudinal effects of smoking cessation on carotid artery atherosclerosis in contemporary smokers: The Wisconsin Smokers Health Study

Background and aims: We quantified the effects of smoking and smoking cessation on carotid artery atherosclerosis and wall thickness in two unique cohorts of smokers making a quit attempt. Methods: Our primary analysis included 726 smokers making a quit attempt in a randomized clinical trial with long-term follow-up. Our secondary analysis included 889 smokers making a quit attempt in a subsequent trial. Participants underwent carotid artery ultrasonography at baseline and up to 3 subsequent visits. Primary outcomes were changes in carotid plaque score and intima media-thickness (IMT). We calculated a smoking burden score (SBS) that reflected the number of visits in which participants reported smoking after the quit attempt. Multivariable regression examined relations between SBS and carotid artery outcomes with adjustments for cardiovascular disease risk factors. Results: In the primary analysis, participants were mean (standard deviation) 46.1 (10.3) years old (57.9% female) and smoked 21.1 (8.9) cigarettes per day (CPD). After a median of 7 years, lower SBS predicted less increase in carotid plaque score (Chi-squared = 13.0, p = 0.012). SBS independently predicted change in carotid plaque score (p = 0.007; SBS 0 vs 4) as did baseline CPD (p = 0.024) and age (p<0.0001). SBS did not affect carotid IMT change. In the secondary analysis, increasing SBS was associated with increased likelihood of new plaques over 3 years among participants that smoked >= 15 CPD, (Chi-squared = 6.51, p = 0.011). Conclusions: Smoking cessation is associated with less progression of carotid plaque, but not IMT. Salutary associations of smoking cessation with carotid plaque progression are related to degree of abstinence.