Smoking and myocardial infarction case-fatality: hospital and population approach

Smoking is a risk factor for coronary heart disease, but it has been associated with better short-term prognosis in hospitalized patients with acute myocardial infarction. The aims of this study were to determine the association between smoking and myocardial infarction 28-day case-fatality in hospitalized patients and at the population level; and, whether smokers presenting with fatal myocardial infarction are more likely to die before reaching a hospital.

Population-based myocardial infarction registry, carried out in 1997-1998 in seven regions of Spain, used standardized methods to find and analyze suspected myocardial infarction patients (10 654 patients; 7796 hospitalized). Four categories of smoking status were defined: never-smokers, former smokers for more than 1 year, former smokers for less than 1 year, and current smokers.

The main end-point was 28-day case-fatality, found to be 20.1, 17.1, 15.6, and 8.9%, in the four smoking status categories, respectively, for hospitalized patients; and 37.4, 33.0, 24.5, and 23.2%, respectively, at population level. Hospitalized current smokers had lower age, sex, and comorbidity-adjusted 28-day case-fatality than never-smokers (odds ratio=0.71; 95% confidence interval: 0.56-0.90). This association held at population level (odds ratio=0.68; 95% confidence interval: 0.60-0.76), in which former smoking was also associated with lower case-fatality. In fatal cases, recent former smokers presented a lower risk of out-of-hospital death than never-smokers (odds ratio=0.47; 95% confidence interval: 0.29-0.77), whereas current smoking was marginally associated with out-of-hospital death (odds ratio=1.22; 95% confidence interval: 0.99-1.50).

Current smoking is associated with lower 28-day case-fatality in hospitalized myocardial infarction patients. This association held at population level. Among fatal cases, smoking is associated with higher and recent former smoking with lower risk of dying out-of-hospital.