To describe the changes in nationwide acute myocardial infarction (AMI) incidence following the implementation of a law banning smoking indoors in restaurants on 1 June 2007.

Retrospective registry study of all hospitalisations for AMI in Finland. All 34 887 hospitalisations for AMI between 1 June 2005 and 31 May 2009 were identified from the Care Register for Health Care (CRHC) and statistics for tobacco consumption were obtained from the National Institute for Health and Welfare. Comorbidities for individual hospitalisations were searched from the CRHC.

The incidence rate of AMI was reduced by 6.3% (95% CI 4.1% to 8.6%; p<0.0001) in the latter half of the study period following the smoking ban when adjusted for age, gender and overall population prevalence of smoking. Short-term incidence of AMI (6-month prior vs 6 months after the smoking ban) was also reduced (4.5%, 95% CI 0.2% to 9.0%; p=0.0399) and was largest in the working middle-aged group (40-50 years) but observed also in the oldest age group (>70 years). The incidence rates declined similarly for men and women.

Banning indoor tobacco smoking in restaurants was associated with a mild additional reduction in AMI incidence on a nationwide level in Finland.