Smoking trajectories and residual cardiovascular risk in patients with stable coronary artery disease: an international cohort study

BACKGROUND AND AIMS: There is a variety of smoking habits trajectories in patients with established stable coronary artery disease (CAD), with unclear consequences on cardiovascular (CV) events. We aimed to clarify the impact of smoking cessation and reduction on long-term cardiovascular outcomes in stable CAD patients, evaluating whether quitting at any stage still provides significant benefits and to what extent. METHODS: The CLARIFY registry included 32,378 outpatients with stable CAD. Smoking history and status were recorded annually during the 5-year follow-up. In active smokers, we studied the effect of smoking cessation or reduction. In former smokers, we analysed the timing of smoking cessation relative to CAD diagnosis and residual CV risk based on years of abstinence. The primary outcome was a composite of CV death and MI. RESULTS: At inclusion, 46.2% of patients were former smokers and 12.5% current smokers. Amongst active smokers, smoking cessation in the stable phase of the disease was associated with improved outcomes, irrespective of timing (aHR 0.56, 95%CI 0.42-0.76, p<0.001). However, smoking quantity reduction was not associated with improved CV outcomes. Among former smokers, 55.7% had quit within a year of CAD diagnosis. Each additional year of smoking post-CAD diagnosis increased CV risk. Former smokers never returned to the CV risk level of never smokers, regardless of years of abstinence. CONCLUSIONS: In stable CAD patients, smoking cessation is associated with significantly better CV outcomes and survival, irrespective of timing of cessation, and should therefore always be a priority. Smoking reduction was not associated with improved CV outcomes. Most former smokers quit within a year of CAD diagnosis, and CV risk increase with each subsequent year of active smoking.