Effectiveness of Indiana's Statewide Smoke-Free Indoor Air Law in Reducing Prevalence of Adult Cigarette Smoking.

Indiana recently implemented a statewide smoke-free indoor air law that has prohibited smoking in both restaurants and non-hospitality workplaces. Evidence for the effectiveness of the recent statewide smoke-free indoor law may persuade 14 states that do not have any statewide smoke-free laws to enact such laws. We evaluated the effectiveness of Indiana's State Smoke-Free Air Law, implemented July 2012, in reducing adult smoking prevalence. We analyzed samples of U.S. adults using a nonequivalent control group design with multi-year, cross-sectional data from the 2011-2016 Behavioral Risk Factor Surveillance System ( N= 2,259,014). Four state groups with different levels of comprehensiveness in regard to statewide smoke-free indoor air laws in 2011-2016 served as the comparison groups, namely those with: (1) no law; (2) a partial law (prohibiting smoking in either one or two of these three settings, namely non-hospitality workplaces, restaurants, and bars); (3) a comprehensive law (prohibiting smoking in all non-hospitality workplaces, restaurants, and bars); and (4) those that changed from a partial to a comprehensive law. We used a difference-in-differences approach with multiple logistic regressions to assess the net effect of the policy with a secular trend removed. The decline rate of cigarette smoking in Indiana was steeper, from 21.2% in 2011-2012 to 17.8% in 2013-2016, than in states in our four comparison groups, which suggests a significant reduction in adult cigarette smoking prevalence above and beyond the downward secular trend observed. All the comparison groups showed higher odds of cigarette smoking than Indiana (adjusted odds ratios range from 1.08 to 1.16). Although a long-term effect of Indiana's State Smoke-Free Air Law has yet to be evaluated, current data indicate that such a policy appears to be effective in reducing smoking prevalence. The implementation of statewide smoke-free indoor air laws in all restaurants and non-hospitality workplaces may help reduce smoking rates in the 14 states that still do not have any statewide smoke-free indoor air laws.