'Smoker's paradox' in young patients with acute myocardial infarction

Of the patients suffering from acute myocardial infarction (AMI), smokers are younger than non-smokers, which may be a major confounding factor causing 'smoker's paradox'. Therefore, in the present study we evaluated the 'smoker's paradox' in young patients with AMI. In all, 1218 young AMI patients (≤ 45 years of age), comprising 990 smokers and 228 non-smokers, were enrolled in the present study. In-hospital and 8 months clinical outcomes were compared between the smokers and non-smokers. Baseline clinical characteristics showed that smokers were more likely to be male (97.9% vs 72.4%; P < 0.001) and had a higher rate of ST-segment elevation myocardial infarction (71.3% vs 59.5%; P = 0.001) than non-smokers. Clinical outcomes showed that smokers had lower rates of in-hospital cardiac death (0.8% vs 3.5%; P = 0.004), total death (0.8% vs 3.5%; P = 0.004) and 8 months cardiac death (1.1% vs 3.9%; P = 0.006) and total death (1.3% vs 4.4%; P = 0.005) than non-smokers. Multivariable logistic analysis showed that current smoking was an independent protective predictor of 8 months cardiac death (odds ratio (OR) 0.25; 95% confidence interval (CI) 0.07-0.92; P = 0.037) and total death (OR 0.26; 95% CI 0.09-0.82; P = 0.021). Subgroup analysis in patients who underwent percutaneous coronary intervention after AMI showed that current smoking was an independent protective predictor of 8 months total major adverse cardiac events (OR 0.47; 95% CI 0.23-0.97; P = 0.041). Current smoking seems to be associated with better clinical outcomes in young patients with AMI, suggesting the existence of the 'smoker's paradox' in this particular subset of patients.