Cost-effectiveness of a complex intervention to reduce children's exposure to secondhand smoke in the home

Background: Second-hand smoke (SHS) causes numerous health problems in children such as asthma, respiratory tract infections and sudden infant death syndrome. The home is the main source of exposure to SHS for children, particularly for young children. We estimated the cost-effectiveness of a complex intervention designed to reduce SHS exposure of children whose primary caregiver feels unable or unwilling to quit smoking. Methods: A cost-effectiveness analysis was carried out alongside an open-label, parallel, randomised controlled trial in deprived communities in Nottingham, England. A complex intervention combining behavioural support, nicotine replacement therapy and personalised feedback on home air quality was compared with usual care. A total number of 205 households were recruited, where the main caregivers were aged 18 and over, with a child aged under five years living in their household reporting smoking inside their home. Analyses for this study were undertaken from the National Health Service/Personal Social Services perspective. All costs were estimated in UK pounds (£) at 2013/14 prices. The primary outcome was the incremental cost-effectiveness of change in air quality in the home, measured as average 16-24 h levels of particulate matter of < 2.5 μm diameter (PM 2.5), between baseline and 12 weeks. Secondary outcomes included incremental cost per quitter, quit attempts and cigarette consumption in the home. A non-parametric bootstrap re-sampling technique was employed to explore uncertainty around the calculated incremental cost-effectiveness ratios. Results: The complex intervention achieved reduced PM 2.5 by 21.6 μg/m 3 (95% CI: 5.4 to 37.9), with an incremental cost of £283 (95% CI: £254-£313), relative to usual care. The incremental cost-effectiveness ratio was £131 (bootstrapped 95% CI: £72-£467) per additional 10μg/m 3 reduction in PM 2.5, or £71 (bootstrapped 95% CI: -£57-£309) per additional quitter. Conclusions: This trial targeted a socio-economically disadvantaged population that has been neglected within the literature. The complex intervention was more costly but more effective in reducing PM2.5 compared with the usual care. It offers huge potential to reduce children's' tobacco-related harm by reducing exposure to SHS in the home. The intervention is considered cost-effective if the decision maker is willing to pay £131 per additional 10μg/m 3 of PM 2.5 reduction. Trial registration: The Smoke Free Homes trial was registered with isrctn.com on 29 January 2013 with the identifier ISRCTN81701383.