This is the first study to demonstrate a statistically significant association between ETS exposure reduction and fewer episodes of poor asthma control, respiratory-related ED visits, and hospitalizations. Secondhand smoke exposure within this population of urban school children with asthma was 47%. Exposure in the primary home accounted for 60% of the exposure. Over time, ETS exposure decreased from 47 to 40% among the children enrolled in this clinical trial. Children who had any decrease in ETS exposure had fewer episodes of poor asthma control, ED visits and hospitalizations than those who had the same or increased exposure. This demonstrates the potential importance of ETS exposure reduction as a mechanism to improve asthma control and morbidity.
ETS exposure reduction is a fairly new area of scientific study. A Cochrane review26
of the ETS reduction interventions indicated that few programs produced a statistically significant reduction. Behavioral interventions that employ more intensive strategies are more effective than those that are less intensive,2,18
and a combination approach that includes both counseling and pharmacologic therapy is more effective than either alone.2
To date, only two studies by Winickoff et al19,20
report on a combination approach among smoking parents of children. In these studies, Winickoff et al19,20
report that the number of quit attempts among parents increased and the number of cigarettes smoked in the house and car decreased following the intervention. The 7-day abstinence rates at 2 months in these studies were 18%20
respectively. Behavioral changes noted include fewer smoked cigarettes inside the home, the car, and in the presence of the child.19,20
These studies indicate that ETS exposure reduction among children is feasible; however, this has yet to be linked to changes in asthma outcomes or health care utilization.
The observed reductions in health-care utilization in this study may have significant implications for the economic feasibility of ETS reduction strategies. While ED visits and hospitalizations are relatively uncommon, they are expensive. Therefore, costs associated with ETS reduction strategies could be offset by lower health expenditures in the child. Given that the majority of ETS exposure in the home is due to parental smoking, the most effective ETS reduction strategy may be to provide smoking cessation interventions to parents and possibly other household members. Additionally, smoking cessation has the potential to not only reduce ETS-related health expenditures in the child with asthma but to also offer direct health benefits to nonasthmatic siblings and the smoker himself. The combination of these effects may make smoking cessation interventions the most cost-effective ETS reduction strategy.
Another important finding of this study is that reduction in ETS exposure leads to fewer episodes of poor asthma control that do not necessarily lead to ED visits and hospitalizations. Improved asthma control may increase the number of asthma symptom-free days and improve quality of life. It may also lead to fewer medication needs and urgent health-care visits. If realized, these benefits would make ETS reduction and smoking cessation interventions in parents of children with asthma even more cost-effective. Future studies should examine the cost-effectiveness of providing intensive ETS reduction strategies in combination with pharmocotherapy.
The percentage of children who had at least one ED visit at baseline was higher among those who had a decrease in ETS exposure than the percentage observed in children who did not have an ETS reduction. One explanation is that parents obtained smoking cessation or ETS reduction counseling at the time of the ED visit and complied with the advice. This pattern was also observed in the hospitalization data. If this is true, it may reinforce the notion that ED visits and hospitalizations represent a window of opportunity for intervention as many parents are motivated to quit.27,28
One limitation of this study is that the child's ETS exposure was collected via caregiver report. The disadvantage of this method is the potential for inaccurate reporting, particularly underreporting of the child's exposure. Measures of tobacco metabolites obtained from samples of bodily fluids are often used as objective measures of ETS exposure in children. While these measures are considered to be less subjective, there are a number of limitations to their use including cost and difficulty of obtaining specimens. Parental report and biological samples are correlated; however, Hovell et al29
suggest that parental reports should be confirmed with direct measures of ETS exposure. Emerson et al30
examined the accuracy of ETS exposure measures among asthmatic children and found the reliability estimates for parent-reported tobacco use to be much greater than that of urine cotinine assays. In fact, the reliability of urinary cotinine was 0.04, indicating that the measure was unreliable. Therefore, future work should examine this question prospectively using both parental report and measures of tobacco metabolites as markers of ETS exposure in the children.
Another limitation of this analysis is that the number of children who had a hospitalization or ED visit for asthma was small. These are relatively uncommon events even among children with asthma, and future studies should be powered to detect these differences.
Potential policy implications from these findings include the importance of identifying funding mechanisms to provide ETS reduction and smoking cessation counseling for parents and caregivers of children with asthma. Research to identify the most cost-effective strategy is warranted. It is likely the most cost-effective strategy is a smoking cessation intervention that combines counseling with pharmacologic therapies. This combination approach has been deemed the most effective smoking cessation strategy2
and offers potential health benefits to the child with asthma, nonasthmatic siblings, and the smoker himself.