A randomised controlled trial of a complex intervention to reduce children’s exposure to secondhand smoke in the home

Objectives Exposing children to secondhand tobacco smoke (SHS) causes significant harm and occurs predominantly through smoking by caregivers in the family home. We report a trial of a complex intervention designed to reduce secondhand smoke exposure of children whose primary caregiver feels unable or unwilling to quit smoking.

Design An open-label, parallel, randomised controlled trial.

Setting Deprived communities in Nottingham City and County, England

Participants Caregivers resident in Nottingham City and County in England who were at least 18 years old, the main caregiver of a child aged under 5 years living in their household, and reported that they were smoking tobacco inside their home.

Interventions We compared a complex intervention combining personalised feedback on home air quality, behavioural support and nicotine replacement therapy for temporary abstinence with usual care.

Main outcomes The primary outcome was change in air quality in the home, measured as average 16–24  hours levels of particulate matter of  < 2.5  µm diameter (PM2.5), between baseline and 12 weeks. Secondary outcomes included changes in maximum PM2.5, proportion of time PM2.5 exceeded WHO recommended levels of maximum exposure of 25  µg/mg3, child salivary cotinine, caregivers’ cigarette consumption, nicotine dependence, determination to stop smoking, quit attempts and quitting altogether during the intervention.

Results Arithmetic mean PM2.5 decreased significantly more (by 35.2 %; 95%  CI 12.7% to 51.9 %) in intervention than in usual care households, as did the proportion of time PM2.5 exceeded 25  µg/mg3, child salivary cotinine concentrations, caregivers’ cigarette consumption in the home, nicotine dependence, determination to quit and likelihood of having made a quit attempt.

Conclusions By reducing exposure to SHS in the homes of children who live with smokers unable or unwilling to quit, this intervention offers huge potential to reduce children’s’ tobacco-related harm.

Trial registration number ISRCTN81701383.

This trial was funded by the UK National Institute for Health Research (NIHR): RP-PG-0608-10020