Introduction Efficacy of preventive therapy with statins in reducing mortality and cardiovascular morbidity in patients with and without cardiovascular disease has been shown in clinical settings, but effectiveness results were not reported.

Objectives To evaluate whether chronic statin therapy before infarction reduces mortality within 30 days after acute myocardial infarction (AMI) and investigate potential confounders/effect modifiers (gender, age and comorbidities).

Methods Hospital discharges of AMI patients (≥35 years) resident in the Lazio region in 2007–2008, were selected, excluding patients with AMI or revascularisation procedures (aortocoronary bypass, PTCA) in the preceding 9 years. Statin use (ATC: C10AA, C10B) during 1 year preceding the index admission was assessed through the drug claims information system; patients were defined “partially adherent” with 20%–80% days covered by statin doses and “adherent” with 80% and more coverage. Crude and adjusted 30-day mortality risks of statin users vs nonusers were estimated using logistic regression models. The role of gender and age as effect modifiers, interaction terms were included in the model.

Results Among 6790 AMI patients statin users showed reduced mortality risk compared to nonusers (OR=0.75, 95% CI 0.58 to 0.98 for partially adherent, OR=0.85 95% CI 0.66 to 1.09 for adherent). The protective effect was more evident in females (OR=0.74, 95% CI 0.52 to 1.05 for partially adherent, OR=0.67 95% CI 0.46 to 0.97 for adherent) and in older people (>85 years) (OR=0.84, 95% CI 0.50 to 1.40 for partially adherent, OR=0.51 95% CI 0.29 to 0.91 for adherent).

Conclusions Chronic statin therapy before infarction reduced 30 days mortality in patients with AMI, especially in females and elderly.