Time-dependent relation between smoking cessation and improved exercise tolerance in apparently healthy middle-age men and women

Background: Smoking is an independent cardiovascular risk factor and correlates with reduced exercise tolerance. However, data on the time dependent effect of smoking cessation on exercise tolerance are limited. Design and methods: We investigated 17,115 men and women who were annually screened at the Institute for Medical Screening of the Chaim Sheba Medical Centre. All subjects had their smoking status documented and performed an exercise stress testing (EST) according to Bruce protocol at each visit. Subjects were divided at baseline into four groups: active smokers (N=2858), recent quitters (smoking cessation 2 years before baseline EST; N=861), remote quitters (smoking cessation >2 years before the baseline EST; N=3856) and never smokers (N=9810). Baseline and follow up EST duration were compared among the four groups. Results: Recent quitters demonstrated a 2.4-fold improvement in their EST duration compared with active smokers (improvement of 24±157 vs. 10±157 s, respectively, p=0.02). Multivariate logistic regression showed that recent quitters were 26% more likely to improve their exercise tolerance compared with active smokers (95% confidence interval (CI) 1.08-1.47, p=0.003). Assessing smoking status as a time-dependent covariate during four consecutive visits demonstrated that recent quitters were 17% more likely to improve their exercise tolerance compared with active smokers (95% CI 1.02-1.34, p=0.02), with a less pronounced benefit among remote quitters (hazard ratio=1.11, 95% CI 1.02-1.21; p=0.01). Conclusions: Smoking cessation is independently associated with improved exercise tolerance. The benefits of smoking cessation are evident within the first two years of abstinence.