Effects of smoke-free air law on acute myocardial infarction hospitalization in Indianapolis and Marion County, Indiana

BACKGROUND: A comprehensive smoke-free air law was enacted on June 1, 2012 in most of Marion County, Indiana, including all of the City of Indianapolis. We evaluated changes in acute myocardial infarction (AMI) admission rates in Indianapolis and Marion County before compared to after the law. METHODS: We collected AMI admissions from five Marion County hospitals between May 2007 and December 2014. We used Poisson regression to evaluate the overall effects of the law on monthly AMI hospitalizations, adjusting for month, seasonality, meteorology, air pollution, and hospital utilization. We tested the interactions between the law and AMI risk factors on monthly AMI admission rates to identify subpopulations for which the effects might be stronger. RESULTS: Monthly AMI admissions declined 20% (95% CI 14–25%) in Marion County and 25% (95% CI 20–29%) in Indianapolis after the law was implemented. We observed decreases among never (21%, 95% CI 13–29%), former (28%, 95% CI 21–34%), and current smokers (26%, 95% CI 11–38%); Medicaid beneficiaries (19%, 95% CI 9–29%) and non-beneficiaries (26%, 95% CI 20–31%). We observed decreases among those with a history of diabetes (Yes: 22%, 95% CI 14–29%; No: 25%, 95% CI 18–31%), congestive heart failure (Yes: 23%, 95% CI 16–30%; No: 24%, 95% CI 17–31%), and hypertension (Yes: 23%, 95% CI 17–28%: No: 26%, 95% CI 15–36%). CONCLUSIONS: We observed decreases in AMI admissions comparable with previous studies. We identified subpopulations who benefitted from the law, such as former and current smokers, and those without comorbidities such as congestive heart failure and hypertension. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12889-018-5153-y) contains supplementary material, which is available to authorized users.