Children Learning About Second-hand Smoke: Cluster randomised-controlled trial

Lead Research Organisation: University of York
Department Name: Health Science


Breathing in other people's exhaled smoke is called second-hand smoking. Second-hand smoke (SHS) contains harmful chemicals and is a serious health hazard to non-smokers. SHS is estimated to cost more than 800,000 lives per year, worldwide. Children are worst affected; almost a third of deaths from SHS exposure occur in children. A large proportion of the overall burden of diseases due to SHS in children is due to lung diseases such as asthma and chest infections and lung cancer. SHS exposure can also lead to meningitis in children. Children exposed to SHS are more likely to be hospitalised, fall short of their academic potential and take up smoking themselves as compared to those living in smoke-free environments. Recognising SHS as a public health threat, most countries have introduced bans on smoking in enclosed public spaces, which has significantly reduced adults' exposure to SHS. However, for many children, cars and homes remain the most likely places for them to breathe SHS. The only possible way to protect them from SHS is to make cars and homes completely smoke-free.

For the last few years, we have been working with schools, parents and children to develop and test a school-based intervention called, 'Smoke-Free Intervention (SFI). It consists of six teaching lessons delivered by schoolteachers, four fun activities and one educational take home resource. Teaching lessons help to increase pupils' knowledge about the harms caused by breathing second-hand smoke. Fun activities include storytelling, role-playing, quizzes and games. These activities help to motivate children to act and feel confident in talking to adults to persuade them not to smoke inside homes. The take-home resource helps children to show what they have learned in school and to negotiate with their families to "sign-up" to a voluntary contract to make their homes smoke-free. The results of this work show that it is possible to encourage children to discuss with their families ways of restricting smoking inside their homes. Our pilot study also showed that it is possible to recruit and retain schools and children and collect the necessary data for such studies. Inspired by our pilot work, we now propose a large study in Bangladesh and Pakistan where SHS is a major public health problem and a priority for policy makers. Through our work in these countries for several years, we have established collaborations with schools, local communities and policy makers. We wish to examine how effective SFI is, in reducing children's exposure to SHS in homes. We are also interested to see if SFI can improve children's lung health, academic performance and general quality of life, and if it can reduce their health service use. To provide accurate answers to these important questions, we will recruit a total of 66 schools and 2,636 children between 9-12 years of age. We will randomly allocate schools to two arms: arm 1 and arm 2. School teachers in arm 1 will receive training and resources on SFI. School teachers will then deliver SFI in classrooms to the children. Those in arm 2, will not deliver anything about SHS to the children. They will receive SFI to deliver only after the completion of the trial. We will also use objective measurements including testing children saliva for cotinine (a chemical compound derived from nicotine) to assess whether our intervention has reduced their SHS exposure. We will also record their respiratory symptoms such as coughing and wheezing and measure their lung functions and quality of life. We will undertake these measurements as described above using internationally agreed standards. During the study, we will repeat these assessments at regular intervals. Using economics, we will also assess whether SFI is value for money. We will run discussion groups with some children to ask about their experience of negotiating a smoke-free home; and interview some parents and teachers to investigate the likely obstacles to implementing SFI.

Technical Summary

Second-hand smoke (SHS) exposure costs 800,000 lives a year. Children in developing countries are worst affected as smoke-free laws are only partially implemented. Private homes and cars remain a key source of SHS exposure. There is limited evidence on non-legislative interventions designed to protect children from SHS exposure. Following the success of two feasibility studies and a pilot trial, we plan to evaluate a school-based approach to protect children from SHS exposure in Bangladesh and Pakistan - countries with a strong commitment to smoke-free environments but with high levels of SHS exposure in children.
We aim to assess the effectiveness and cost-effectiveness of a school-based Smoke-Free Intervention (SFI) in reducing children's exposure to SHS and the frequency and severity of respiratory symptoms. SFI, a behavioural intervention, consists of two 45-minute sessions delivered by schoolteachers over two consecutive days in classroom settings. Each session includes classroom presentations, a quiz, interactive games, storytelling and role-play. In our feasibility work, these activities helped children learn negotiation skills and develop confidence in persuading their parents/carers to implement smoking restrictions in their homes.
We will conduct a two-arm cluster randomised controlled-trial in Dhaka and Karachi. We will recruit and randomise 66 schools (2,636 children); half will be allocated to receive SFI (arm 1) and the other half usual education (arm 2). A change in salivary cotinine -a highly sensitive and specific biomarker of SHS exposure- is the primary outcome. Secondary outcomes include frequency and severity of respiratory symptoms, healthcare contacts, school absenteeism, smoking uptake, lung functions and quality of life. An economic and process evaluation will also be conducted. The investigators' expertise and track record within the field is complemented by their extensive links with schools and with policy makers in the two countries.

Planned Impact

CLASS III trial findings are likely to have a big impact: (a) By tackling adult smoking behaviours at homes, we are aiming to improve health outcomes of children in Bangladesh and Pakistan- our study will be one of three MRC-funded studies assessing and demonstrating the effect of modifying smoking behaviours through community-based approaches in South Asia. (b) It will improve the health of the most vulnerable - SHS disproportionately affects women and children with devastating health and economic consequences. If successful and taken up, our intervention would lead to a reduction in the burden of disease among the most vulnerable. (c) Knowledge translation and scaling up into policy and practice - Our research is grounded within implementation science, attempting to answer questions that are highly relevant to programme managers. Being research partners, the findings will be owned by policy makers and advocates in health and education sector, enabling the adoption, scaling up and sustainability of such intervention. (d) A new model of programme implementation - Bangladesh and Pakistan, like many other low- and middle-income countries, lacks infrastructure to provide comprehensive health promotion through their health services. In this study, we will develop knowledge on how best to support local schools in becoming aware, owning and delivering health promotion. (e) Addressing Sustainable Development Goals - By tackling smoking behaviours, our proposal indirectly, creates opportunities for families to have more disposable income (SDG 1) to spend on food (SDG 2), and children's education (SDG 4). Addressing tobacco use is likely to promote gender equality (SDG 5) and maternal and child health (SDG 3) and reduce child mortality (SDG 3). Reduction in tobacco demand also cuts down pesticide use and deforestation leading to environmental sustainability (SDG 13 & 15). Protecting children from second-hand smoking can enhance their educational attainment (SDG 4) leading to improved economy (SDG 8).


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Khokhar MA (2020) Smoke-Free Policies in the Global South. in Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco