The impact of smoke-free laws on asthma discharges: A multistate analysis

Objectives. This is the first, to my knowledge, multistate, county-level analysis of Healthcare Cost and Utilization Project state inpatient data to examine the relationship between smoke-free laws and asthma discharges. Methods. I used treatment and control groups to examine the effects of state and county or city smoke-free laws separately and together (2002-2009). I compared quarterly county-level discharge rates before and after the implementation of 12 state smoke-free laws, accounting for counties with preexisting county or city smoke-free laws and using the data from 5 states without state smoke-free laws as a control group. I used difference-in-differences models, controlling for year and state fixed effects, state cigarette taxes, seasonality, and numerous county-level factors. Results. I observed statistically significant reductions in asthma discharges after the implementation of county smoke-free laws but no statistically significant effect of state laws besides the effect of county laws or of state laws alone. There was also no statistically significant effect of any smoke-free law on appendicitis discharges. Conclusions. It may be unwise to pursue state smoke-free laws where they have yet to pass; rather, efforts might be better focused at the local level, where there is evidence of a significant impact.