Impact of Smoking Status on Major Adverse Cardiovascular Events in STEMI Patients: A Retrospective Cohort Study in Western Iran.

Background: ST-elevation myocardial infarction (STEMI) remains a major cause of mortality worldwide. Whether smoking status and cumulative exposure influence prognosis in the contemporary era of timely reperfusion and intensive secondary prevention remains uncertain, particularly in populations with very high smoking rates. This study aimed to evaluate the association between smoking status and major adverse cardiovascular events (MACE) among patients with STEMI in western Iran.

Methods: A retrospective cohort study was conducted involving 645 consecutive patients with STEMI at a tertiary center in Western Iran. Patients were stratified by smoking status: never-smokers (n = 356), moderate smokers (<15 pack-years, n = 124), and heavy smokers (≥15 pack-years, n = 165). Outcomes included 1-year all-cause mortality and MACE over 365 days. Cox regression models adjusted for confounders were used to estimate hazard ratio with 95% confidence intervals (HR, 95% CI).

Results: In crude analyses, heavy smokers had lower 1-year mortality (HR = 0.44, 95% CI: 0.22-0.87) and MACE (HR = 0.60, 95% CI: 0.40-0.91) compared to never-smokers. After full adjustment, these associations became non-significant (mortality HR = 0.92, 95% CI: 0.28-3.02; MACE HR = 1.51, 95% CI: 0.81-2.81). Never-smokers were older, more likely female, and had higher comorbidity rates, explaining crude differences. Socioeconomic factors, particularly education, influenced outcomes.

Conclusion: The smoker's paradox is driven by confounders, not a protective effect of smoking. Smoking cessation and addressing socioeconomic disparities are critical for improving STEMI outcomes in high-risk populations.