ArticlesEffect of smoke-free legislation on perinatal and child health: a systematic review and meta-analysis
Introduction
Smoking is estimated to kill 5·7 million people each year, and effective tobacco control is a key instrument for reduction of global mortality and rates of non-communicable diseases.1, 2 The WHO Framework Convention for Tobacco Control provides a valuable means to implement and evaluate tobacco control measures.3, 4 As part of six key recommendations the implementation of smoke-free environments is advocated as an instrument to reduce the estimated 600 000 deaths and 10·9 million disability-adjusted life-years (DALYs) globally due to second-hand smoke exposure each year.1, 5 In support of this recommendation, there is now emerging evidence that smoke-free laws can effectively reduce second-hand smoke exposure and improve population health.6 A 2012 meta-analysis showed a 15% reduction in cardiovascular events and a 24% reduction in admissions to hospital for respiratory diseases after introduction of smoke-free legislation.7 However, although 177 nations have now ratified the Framework Convention for Tobacco Control, at present, only 16% of the world's population is covered by comprehensive smoke-free laws.5
A broad appreciation of the population health effects of smoke-free legislation might help to further strengthen its mandate. Most studies have focused on the evaluation of adult outcomes; however, children account for more than a quarter of all deaths and more than half of all DALYs due to second-hand smoke exposure.1 The effect of in-utero and early-life exposures on health in childhood and later life is a growing specialty of research interest with major public health implications.8 Children are particularly vulnerable to the adverse effects of second-hand smoke because their lungs and immune system are still undergoing development. The first reports of detrimental health effects of parental smoking on paediatric respiratory health date back to the early 1970s.9 Second-hand smoke has since been linked to a range of adverse outcomes during early-life including stillbirth, preterm birth, low birthweight, congenital anomalies, neonatal and infant mortality, asthma, and respiratory infections.10, 11, 12 Furthermore, recent studies implicate childhood second-hand smoke exposure in the development of non-communicable diseases in later life.13, 14 40% of children worldwide are regularly exposed to second-hand smoke,1 which is of great concern because they are generally unable to influence their own level of exposure. Smoke-free legislation has been shown to reduce second-hand smoke exposure in children and increase the proportion of smoke-free homes in several countries.15, 16, 17, 18, 19
Emerging evidence now shows particular benefits of smoke-free legislation on early-life health.20, 21, 22, 23 However, only a small minority of the world's population is covered by comprehensive smoke-free laws, and this proportion is increasing slowly.5 This slow increase could at least partly be because of uncertainty about the potential health benefits, particularly concerning child health. A comprehensive assessment is therefore warranted to obtain a well informed appreciation of the effect of smoke-free public and work environments on early-life health and to inform national and international policy decisions on implementation of smoke-free legislation.
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Search strategy and selection criteria
We followed the methods detailed in a peer-reviewed systematic review protocol that is registered with PROSPERO (CRD42013003522).24 We searched online databases of medical literature (Medline, Embase, Google Scholar, ISI Web of Science, Cochrane Central Register of Controlled Trials, Trip, Cumulative Index to Nursing and Allied Health [CINAHL], Allied and Complementary Medicine Database [AMED], CAB International, Global Health, WHO Global Health Library [regional and global indexes], SciELO,
Results
We screened 9228 titles from which we identified 20 potentially eligible studies (figure 1).20, 21, 22, 23, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45 One study reporting a mixed paediatric and adult population was excluded because subgroup analyses for children could not be obtained.45 Eight further studies were excluded because they did not meet EPOC design criteria.37, 38, 39, 40, 41, 42, 43, 44 Appendix p 7 shows the characteristics and findings of the eight excluded
Discussion
This systematic review and meta-analysis presents strong evidence supporting the effectiveness of smoke-free legislation to improve clinically important perinatal and child health outcomes. In particular, pooled estimates suggest that rates of both preterm birth and paediatric hospital admissions for asthma were reduced by 10% after its introduction. Additional reductions in the risk of being born very small for gestational age were identified. This Article adds important information from an
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