Background: Smoker’s paradox usually refers to the common observation of a favourable outcome of smoker patients in acute myocardial infarction. The interpretation of this phenomenon is still controversial and not fully explained. We aimed at assessing whether smoking could be associated with mortality in a large cohort of prospectively enrolled patients with ST segment elevation myocardial infarction (STEMI) referred to primary percutaneous coronary intervention (PCI).
Methods: From April 2006 to December 2018 a population of 2456 STEMI patients treated with primary PCI were prospectively enrolled in the MATRIX registry. Ischemic time, clinical, demographics, angiographic data and 1-year follow-up were collected.
Results: Among 2546 patients admitted with STEMI 1007 (41%) were current smokers. Smokers were 10 years younger and had lower crude in-hospital and 1-year mortality (1.5% vs 6%, p<0.0001 and 5% vs 11%, p<0.0001), shorter ischemic time (203 [147-299] vs 220 [154-334] minutes, p=0.002) and shorter decision time (60 [30-135] vs 70 [36-170] minutes, p=0.0063). After adjustment for different risk factors using Cox regression model, age [adjHR: 1.11 (95%CI: 1.03 – 1.18) – p<0.01] and ischemic time [adjHR: 1.01 (95%CI: 1.01 – 1.02) – p<0.05] appeared to be the confounder factor of the relationship between smoking and in hospital mortality.
Conclusions: In our large prospectively-enrolled population the so-called “smoker’s paradox” is explained by the shorter ischemic time and younger age of the smoking population. Our data shows that smokers were admitted to the hospital for STEMI about 10 years before non-smokers, with a premature coronary atherothrombosis that could be the price to pay for smoking. Smokers had non-significant different risk of in-hospital mortality compared to non-smoking.