Smoking is an important risk factor for cardiovascular disease and all-cause mortality. Cardiac rehabilitation (CR) is effective for reducing the risk of recurrent cardiac events through improving cardiorespiratory fitness (CRF). Little is known about the influence of smoking on CRF throughout long-term CR. The purpose of this analysis was to compare CRF trajectories among individuals with positive and negative smoking history enrolled in long-term CR. Participants had a positive smoking history if they currently or formerly smoked (Smoke+, n = 55, mean age = 64.9 ± 9.0 years) and had a negative history if they never smoked (Smoke–, n = 34, mean age = 61.4 ± 9.0 years). CRF (peak oxygen uptake) was measured at baseline and annually thereafter for 6 years. The Smoke+ group had lower CRF compared with the Smoke– group over enrollment (β = −3.29 (SE = 1.40), 95% confidence interval (CI) −6.04 to −0.54, p = 0.02), but there was no interaction of smoking history and enrollment (β = 0.35 (SE = 0.21), 95% CI: −0.06 to 0.77, p = 0.10). Moreover, trajectories were not influenced by pack-years (β = 0.01 (SE = 0.01), 95% CI: −0.01 to 0.04, p = 0.23) or time smoke-free (β = −0.002 (SE = 0.01), 95% CI: −0.02 to 0.02, p = 0.80). Although the trajectories of CRF do not appear to be affected by smoking behaviour, individuals without a history of smoking maintained higher CRF throughout enrollment.
The benefits of long-term exercise-based cardiac rehabilitation on cardiorespiratory fitness are similar between those who have smoked and those who have never smoked. Neither the number of pack-years nor the length of time spent smoke-free influence cardiorespiratory fitness trajectories following long-term cardiac rehabilitation.