Cigarette smoking is paradoxically associated with low mortality risk after acute myocardial infarction.

Background: Cigarette smoking has been shown to be associated with a decreased risk of death after acute myocardial infarction (AMI), which is also known as the "smokers' paradox." This study aimed to investigate the relationship between smoking and all-cause mortality after AMI.

Methods: We extracted the data of patients who were hospitalized for AMI between November 2005 and September 2010 from nationwide multicenter prospective registries in Korea.

Results: Among a total of 29,199 patients with AMI, 10,251 (42.3%) were current smokers, and 14,006 (57.7%) were nonsmokers. Current smokers were younger, more likely to be male, and had lower frequencies of hypertension, diabetes mellitus, dyslipidemia, and previous history of ischemic heart disease than nonsmokers. The initial presentation was less severe in terms of hemodynamic status, and angiography showed less complex coronary involvement in smokers. The overall mortality rate was 5.4% for current smokers and 9.9% for nonsmokers (hazard ratio [HR], 0.52; 95% confidence interval [CI], 0.47-0.58; p < .001). The gap in risk was attenuated after multivariable adjustment but remained statistically significant (HR, 0.85; 95% CI, 0.76-0.95; p = .005). Propensity score matching corroborated the results of reduced mortality among current smokers (6.7% vs. 7.6%; p = .005).

Conclusions: In this study, in which the patients received up-to-date treatment options, smoking was associated with a 48% decrease in the risk of all-cause mortality at 1 year after AMI.