Systematic reviews and meta-analyses on the effects of active and passive smoking on respiratory health outcomes: the SmokeHaz online resource

Abstract

BackgroundActive and passive smoking increases the risk of respiratory disease in adults and children, but communication of the magnitude of these effects in a manner that is accessible and usable by public and policy makers presents a challenge. We have therefore developed a unique online resource, SmokeHaz, which summarises the effect of smoking on a range of health outcomes, focusing on respiratory diseases. MethodsWe conducted a series of definitive systematic reviews and meta-analyses of longitudinal, nested case-control, and cohort studies. We identified eligible studies using electronic databases (Medline, Embase, and Web of Science, published from 1985 to 2013), conference proceedings, websites, reference lists of reviews and studies, and through contact with experts. No language restrictions were imposed. Random effect meta-analyses were used to pool the findings. Heterogeneity was explored with subgroup analyses, and publication bias was assessed with funnel plots. FindingsWe included a total of 216 articles, none of which disclosed tobacco industry funding. Our reviews confirmed substantially increased risks of lung cancer (risk ratio 10·9, 95% CI 8·3–14·4, n=34), chronic obstructive pulmonary disease (4·0, 3·2–5·1, n=22), and asthma (1·6, 1·1–2·4, n=8) among adult smokers, though these effects were all strongly related to quantity smoked. Exposure to passive smoking significantly increased the risk of several respiratory diseases in childhood, including asthma, wheeze, lower respiratory infections, and reduced lung function, and in adults lung cancer (1·4, 1·2–1·7, n=13). In addition to these expected findings, our reviews showed that active smoking significantly increased the risk of asthma exacerbations, sleep apnoea (2·0, 1·02–3·8 n=2), and tuberculosis (1·6, 1·2–2·1, n=4), and that passive smoking increased the risk of tuberculosis in adults (1·44, 1·02–2·01, n=2). InterpretationThe findings from the systematic reviews have been translated into easily digestible content and published on the SmokeHaz website. We are now evaluating the effectiveness, usability, and accessibility of the website for the public and policy makers. FundingThe research has been independently funded by the European Respiratory Society (ERS) and has been carried out by the UK Centre for Tobacco and Alcohol Studies, with the oversight of the ERS Tobacco Control Committee. The content of the website has been approved by the Executive Committee of ERS and developed by the European Lung Foundation.