Secondhand Smoke Exposure and Adverse Asthma Events Among Low-Income Michigan Children

Abstract

More than eight percent of United States’ children have asthma, with more than half having an asthma exacerbation annually. Minority children and those living in low income households are more likely to experience adverse asthma events and to be exposed to secondhand smoke (SHS), a potent trigger of exacerbations. State smoking bans are associated with reductions in SHS exposure and rates of cardiovascular and respiratory events. This study assesses the impact of Michigan's Dr. Ron Davis Smoke Ban on asthma exacerbations among low-income children and identifies potential effect modification by individual and area level exposures on that association. A cohort of 98,277 children with full coverage in Michigan Medicaid programs and health care utilization consistent with a diagnosis of persistent asthma contributed 4,335,439 months to the cohort between 2007 and 2012. The 48,500 adverse asthma events (representing exacerbations) identified from administrative claims data were compared to area level estimates of neighborhood disadvantage and indicators of exposure to smoking bans. Rates of adverse asthma events were associated with non-white race, younger age, poor asthma control in identification year and increasing neighborhood deprivation. The ban was associated with a 17 percent reduction in asthma events (95% CI: 12-21 percent), adjusting for age group, sex, race/ethnicity, calendar month, prior poor control, prior local smoking ban, and neighborhood disadvantage. The 17 percent reduction is equivalent to 9,400 asthma events during the follow up period, which would have resulted more than $11,000,000 in emergency department charges alone. Children in prior poor control had a larger reduction in adverse asthma events after ban enactment than those with no prior evidence of poor control. Use of asthma medications exhibited similar reductions in the post-Ban period. The injury visit rate showed a smaller reduction, suggesting the reduction in asthma events was not solely due to a secular trend. These findings support the continued enforcement of Michigan’s Ban and provide evidence for the importance of environmental policy for improving asthma management in Michigan. This cohort provides a data model for other jurisdictions needing to assess or predict the impact of a smoking ban.