Background: The effect of cigarette smoking on the risk of myocardial infarction (MI) has long been investigated. However, its role on the likelihood of having MI at young age has not been well understood and appreciated. We investigated whether smoking habits can discriminate young individuals with MI from age- and sex-matched controls.
Methods: We enrolled 100 consecutive patients who had survived their first episode of MI before the age of 36 years and 100 age- and sex-matched controls without a history of cardiovascular disease. Smoking habits, physical activity status, body mass index and blood lipids levels were measured in all participants.
Results: 96% of the patients with premature MI and 55% of the controls reported current smoking habits (p<0.001). Moreover, patients had higher levels of total cholesterol, low density lipoprotein cholesterol, triglycerides and lower levels of high density lipoprotein cholesterol (p<0.05). Multivariate logistic regression analysis showed that current smoking increased 6-fold the odds of having a MI (95% CI 1.01 to 37), after controlling for age, sex, body mass index, hypertension, diabetes, physical activity, family history of coronary heart disease and total cholesterol levels. Finally, discriminant analysis showed that pack-years of smoking was the strongest discriminator for MI among all the investigated factors (lambda-Wilks=0.85).
Conclusions: Our study suggests that cigarette smoking seems to play the most important role for having a MI in individuals under the age of 36 years.