Effectiveness of an Evidence-based Intervention to Promote Smoke-free Homes: a Randomised Controlled Trial

Second-hand tobacco smoke (SHS) is a mixture of smoke exhaled by a smoker and smoke from the burning end of a cigarette. There are more than 4,000 components in SHS, including toxic substances, irritants and, approximately 70 carcinogens. Since 2004, SHS is defined as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer. Exposure to SHS is an important public health problem as it causes a number of life-threatening diseases, among others lung cancer, stroke, chronic obstructive pulmonary disease, and ischemic heart disease in adults. Moreover, children exposed to SHS are at an increased risk for sudden infant death syndrome, acute respiratory infections, otitis media, and more severe asthma. Globally, SHS exposure was the 13th-leading risk factor for deaths in 2019, accounting for 1.30 million deaths. It contributed to 37.0 million disability adjusted life years worldwide, with 11.2% of the burden seen among children under the age of 5 years. While exposure to SHS in most public places is addressed by smokefree regulations, smoking and, consequently, the exposure to SHS at private places, such as homes, is still prevalent and represents a significant public health challenge.

It is evaluated that globally approximately 40% of youth is exposed to SHS at home. In a survey conducted among schoolchildren in Terrassa (Barcelona) in 2006 we found similar results, 41% of children aged 12-13 years reported exposure to SHS at home. For younger ages, another survey we conducted in Barcelona in 2016 showed that 71% of children younger than 12 years were exposed to SHS and 26% of them were exposed to SHS at home. Previous research in Spain have shown that SHS exposure at home is strongly correlated with family structure, smoking rules in household, number of smokers and non-smokers at home and number of cigarettes smoked; moreover, social disparities exist in SHS exposure among children and therefore, the inequalities in SHS burden persist in the local population.

In Spain, a few initiatives have been undertaken to reduce SHS exposure in children. In 2006, the RESPIR·NET multi-level (individual, family, and school) school-based intervention to prevent the exposure to SHS among schoolchildren (12-14 years old) was developed and tested in the city of Terrassa (Barcelona). While crude data indicated that in the intervention group SHS exposure significantly decreased at home (-16.9%); after adjustment for potential confounders the changes showed to be non-significant. In 2008-2009, the BIBE study aimed to evaluate a brief intervention within the context of primary health care, directed to parents who smoke, in order to reduce SHS exposure of babies. A multicentre, open, cluster-randomised clinical trial showed that parents who received the intervention to avoid SHS better adopted the recommended strategies at home with reduced nicotine concentrations in babies' hair samples.

While these interventions did not target promotion of smoke-free homes specifically, a recent study, part of a larger TackSHS Project (www.tackshs.eu), aimed to design, implement and evaluate a "Measuring for change" intervention to create smoke-free homes among families with children from disadvantaged areas. The intervention, developed by the team of the University of Stirling, is based on providing remote air quality feedback to the participants via short messages and emails. While the intervention resulted in small but significant reduction of SHS exposure, it was not effective in creating smoke-free homes; in addition, the design requiring two home visits and installation of air quality monitors challenged the participants' recruitment.

In summary, currently in Spain a high proportion of households allow smoking resulting in unneglectable prevalence and burden of exposure to SHS at home among adults and children. No comprehensive and systematic support is offered at national or local levels for those who want to create smoke-free homes resulting in a significant gap in health prevention services. Therefore, there is an important need to offer such services to Spanish population.