A randomized trial of parental behavioral counseling and cotinine feedback for lowering environmental tobacco smoke exposure in children with asthma: results of the LET'S Manage Asthma trial

Abstract

Background: Secondhand tobacco smoke exposure impairs the control of pediatric asthma. Evidence of the efficacy of interventions to reduce children's exposure and improve disease outcomes has been inconclusive.

Methods: Caregivers of 519 children aged 3 to 12 years with asthma and reported smoke exposure attended two baseline assessment visits, which involved a parent interview, sampling of the children's urine (for cotinine assay), and spirometry (children≥5 years). The caregivers and children (n=352) with significant documented exposure (cotinine≥10 ng/mL) attended a basic asthma education session, provided a third urine sample, and were randomized to the Lowering Environmental Tobacco Smoke: LET'S Manage Asthma (LET'S) intervention (n=178) or usual care (n=174). LET'S included three in-person, stage-of-change-based counseling sessions plus three follow-up phone calls. Cotinine feedback was given at each in-person session. Follow-up visits at 6 and 12 months postrandomization repeated the baseline data collection. Multivariate regression analyses estimated the intervention effect on the natural logarithm of the cotinine to creatinine ratio (lnCCR), use of health-care services, and other outcomes.

Results: In the sample overall, the children in the LET'S intervention had lower follow-up lnCCR values compared with the children in usual care, but the group difference was not significant (β coefficient=-0.307, P=.064), and there was no group difference in the odds of having>one asthma-related medical visit (β coefficient=0.035, P=.78). However, children with high-risk asthma had statistically lower follow-up lnCCR values compared with children in usual care (β coefficient=-1.068, P=.006).

Conclusions: The LET'S intervention was not associated with a statistically significant reduction in tobacco smoke exposure or use of health-care services in the sample as a whole. However, it appeared effective in reducing exposure in children at high risk for subsequent exacerbations.

Trial registry: ClinicialTrials.gov; No.: NCT00217958; URL: clinicaltrials.gov.

Figure 1.

Case progress through the LET’S study. * = Includes patients whose primary care providers were not notified, did not respond, and did not assent, or whose parents could not be successfully contacted. † = Includes patients whose parents failed to keep two or more LET’S prerandomization appointments. ‡ = Reasons for ineligibility include failure to meet the urinary cotinine criterion of > 10 ng/mL from one or more of the three prerandomization urine analyses. LET’S = Lowering Environmental Tobacco Smoke: LET’S Manage Asthma trial.

Figure 2.

Distribution of the mean baseline and mean follow-up log CCR values, by group. The mean value is represented by the + sign, and the median value is represented by the horizontal line in the box. The box represents the interquartile range of values (25th-75th percentiles). The lowest and highest hash marks represent the minimum and maximum observations, respectively. The mean baseline lnCCR is based on the mean of the three prerandomization urinalyses. The mean baseline lnCCR in the LET’S group = 2.53 (± 1.07), and in the usual care (UC) group = 2.68 (± 1.07). The mean follow-up lnCCR is based on the mean of the 6-month and 12-month follow-up urinalyses. The mean baseline lnCCR in the LET’S group = 1.11 (± 1.84), and in the UC group = 0.98 (± 1.83). □ = UC group; = LET’S intervention group. CCR = cotinine to creatinine ratio; lnCCR = natural logarithm of the cotinine to creatinine ratio. See Figure 1 legend for expansion of the other abbreviation.

Figure 3.

A, Distribution of asthma-related medical visits during the prerandomization year, by group. The LET’S group = 1.66 visits per year (± 1.86), the UC group = 1.72 visits per year (± 2.13). B, Distribution of asthma-related medical visits during the follow-up year, by group. The LET’S group = 1.26 visits per year (± 1.73), the UC group = 1.30 visits per year (± 1.94). □ = UC group; = LET’S intervention group. See Figure 1 and 2 legends for expansion of the abbreviations.

Figure 4.

Distribution of mean baseline and follow-up log CCR values, by group and high-risk status. The mean value is represented by the + sign, and the median value is represented by the horizontal line in the box. The box represents the interquartile range of values (25th-75th percentiles). The lowest and highest hash marks represent the minimum and maximum observations, respectively. The mean baseline lnCCR is based on the mean of the three prerandomization urinalyses. The mean follow-up lnCCR is based on the mean of the 6-month and 12-month follow-up urinalyses. Among children who are at high risk, the mean baseline lnCCR in the LET’S group = 2.72 (± 1.15), and in the UC group = 2.49 (± 0.99). The mean follow-up lnCCR in the LET’S group = 0.32 (± 1.82), and in the UC group = 1.07 (± 1.81). Among children who are not at high risk, the mean baseline lnCCR in the LET’S group = 2.67 (± 1.05), and in the UC group = 2.53 (± 1.09). The mean follow-up lnCCR in the LET’S group = 1.15 (± 1.80), and in the UC group = 1.12 (± 1.86). □ = UC group; = LET’S intervention group. See Figures 1 and 2 legends for expansion of the abbreviations.