DATA from the Korean National Health Insurance Service, encompassing over 5.3 million participants, found that ex-smokers with fewer than 8 pack-years (PY) of smoking history showed no increased cardiovascular disease (CVD) risk compared to those who had never smoked. However, for individuals who had accumulated 8 or more PY, the risk reduction was gradual, requiring more than 25 years for their CVD risk to align with that of never-smokers. These findings highlight the prolonged impact of heavy smoking on cardiovascular health even after quitting.
The study aimed to investigate how smoking cessation affects CVD risk in relation to lifetime smoking burden, with a particular focus on the number of years necessary for ex-smokers to reach the CVD risk levels of never-smokers. Using a retrospective cohort design, researchers analysed data from individuals’ smoking habits recorded by the Korean National Health Insurance Service between January 2006 and December 2008. Participants were categorized as current, ex-, or never-smokers and were excluded if their smoking status changed during the study or was unclear. Follow-up occurred every two years until December 2019, and data analysis was conducted in 2022. The primary outcome was the incidence and hazard ratio for CVD, including events such as cardiovascular death, myocardial infarction, stroke, and heart failure. The median cumulative smoking exposure was 14.0 PY for current smokers and 10.5 PY for ex-smokers, with the median cessation duration being 4 years among ex-smokers.
Results showed a clear dose-dependent relationship between cumulative smoking and CVD incidence. Ex-smokers with fewer than 8 PY demonstrated a return to baseline CVD risk comparable to never-smokers within 10 years of quitting. However, for those with at least 8 PY, the risk reduction was significantly delayed, taking over 25 years to reach a similar risk level as never-smokers. These findings suggest that heavier smoking history is associated with longer-lasting cardiovascular risks, emphasizing the importance of both the duration and intensity of smoking on long-term health outcomes.
Clinically, these results indicate that ex-smokers with a history of heavy smoking (≥8 PY) should be managed with an approach similar to that of current smokers due to their sustained elevated risk. This may entail continued cardiovascular risk screening and preventive interventions long after smoking cessation. For lighter ex-smokers, achieving a never-smoker risk level relatively soon after quitting suggests that smoking cessation support can be particularly beneficial. Future research should investigate targeted interventions to accelerate risk reduction for heavy ex-smokers, potentially improving cardiovascular outcomes in this high-risk group.
Reference
Cho JH et al. Smoking cessation and incident cardiovascular disease. JAMA Netw Open. 2024;7(11):e2442639.
