The association between secondhand smoke and sleep‐disordered breathing in children: A systematic review

OBJECTIVE: To systematically review existing literature on the association between secondhand smoke and sleep-disordered breathing in children. DATA SOURCES: PubMed, Embase, Cochrane CENTRAL, Web of Science, and Scopus. REVIEW METHODS: Inclusion criteria included English-language papers containing original human data, with seven or more subjects and age <18 years. Data were systematically collected on study design, patient demographics, clinical characteristics/outcomes, and level of evidence. Two investigators independently reviewed all manuscripts. RESULTS: The initial search yielded 72 abstracts; 18 articles were ultimately included with a total study population of 47,462 patients. Fifteen (83%) articles found a statistically significant association between secondhand smoke and sleep-disordered breathing. All were case-control studies. Quality of articles based on the Newcastle-Ottawa scale averaged 5.8/9 stars. Secondhand smoke was characterized by serum cotinine testing in only two (11%) studies. Sleep-disordered breathing was quantified by polysomnography in only four (22%) of the studies and only one (6%) classified subject using polysomnography exclusively. Habitual snoring was the most common form of sleep-disordered breathing studied in 14/18 (78%) studies, whereas obstructive sleep apnea was reported in one (6%) study and sleep-related hypoxia in another (6%) study. CONCLUSIONS: Although the majority of studies included in this review found a significant association between secondhand smoke and sleep-disordered breathing, all of them were evidence level 3b, for an overall grade of B (Oxford Centre for Evidence-based Medicine). Further higher-quality studies should be performed in the future to better evaluate the relationship between second- smoke and sleep-disordered breathing in children.