Advising parents of asthmatic children on passive smoking: randomised controlled trial.

Objective: To investigate whether parents of asthmatic children would stop smoking or alter their smoking habits to protect their children from environmental tobacco smoke.
Design: Randomised controlled trial.
Setting: Tayside and Fife, Scotland.
Participants: 501 families with an asthmatic child aged 2-12 years living with a parent who smoked.
Intervention: Parents were told about the impact of passive smoking on asthma and were advised to stop smoking or change their smoking habits to protect their child's health.
Main Outcome Measures: Salivary cotinine concentrations in children, and changes in reported smoking habits of the parents 1 year after the intervention.
Results: At the second visit, about 1 year after the baseline visit, a small decrease in salivary cotinine concentrations was found in both groups of children: the mean decrease in the intervention group (0.70 ng/ml) was slightly smaller than that of the control group (0.88 ng/ml), but the net difference of 0.19 ng/ml had a wide 95% confidence interval (-0.86 to 0.48). Overall, 98% of parents in both groups still smoked at follow up. However, there was a non-significant tendency for parents in the intervention group to report smoking more at follow up and to having a reduced desire to stop smoking.
Conclusions: A brief intervention to advise parents of asthmatic children about the risks from passive smoking was ineffective in reducing their children's exposure to environmental tobacco smoke. The intervention may have made some parents less inclined to stop smoking. If a clinician believes that a child's health is being affected by parental smoking, the parent's smoking needs to be addressed as a separate issue from the child's health.