Smoker pseudo-paradox in ST-segment elevation myocardial infarction patients

Introduction: Cigarette smoking is a preventable cause of cardiovascular morbidity and mortality. Despite the adverse effects of smoking, some studies have reported the term "smoker's paradox', meaning better outcomes in smokers following acute myocardial infarction. Aim: The aim of the present study was to evaluate the relationship between smoking status and one-year mortality in patients with ST-segment elevation myocardial infarction (STEMI). Materials and methods: This was a registry-based cohort study of STEMI patients from Imam-Ali hospital, Kermanshah, Iran. Consecutive STEMI patients (July 2016-October 2018) were stratified by smoking status and followed for one year. Cox proportional models were used to estimate crude, age-adjusted, and full-adjusted hazard ratios with 95% confidence intervals (HR, 95%CI). Results: Of 1975 patients (mean age 60.1 years, 76.6% male) included in the study, 48.1% (n=951) were smokers (mean age 57.7 years, 94.7% male). Crude and age-adjusted HR (95% CI) for the associations of smoking and mortality were 0.67 (0.50-0.92) and 0.89 (0.65-1.22), respectively. After adjusting for age, sex, hypertension, diabetes, body-mass index, anterior wall myocardial infarction, creatine kinase-MB, glomerular filtration rate, left ventricular ejection fraction, low-density lipoprotein cholesterol, and hemoglobin, smoking was associated with increased risk of mortality: HR (95% CI: 1.56 (1.04-2.35). Conclusions: In our study, smoking was associated with an increased risk of mortality. Although the smokers had a better outcome, this would be reversed after controlling for age and the other STEMI associated factors.