Is exposure to secondhand smoke associated with cognitive parameters of children and adolescents?--a systematic literature review.

PURPOSE Despite the known association of second hand smoke (SHS) with increased risk of ill health and mortality, the effects of SHS exposure on cognitive functioning in children and adolescents are unclear. Through a critical review of the literature we sought to determine whether a relationship exists between these variables. METHODS The authors systematically reviewed articles (dated 1989-2012) that investigated the association between SHS exposure (including in utero due to SHS exposure by pregnant women) and performance on neurocognitive and academic tests. Eligible studies were identified from searches of Web of Knowledge, MEDLINE, Science Direct, Google Scholar, CINAHL, EMBASE, Zetoc, and Clinicaltrials.gov. RESULTS Fifteen articles were identified, of which 12 showed inverse relationships between SHS and cognitive parameters. Prenatal SHS exposure was inversely associated with neurodevelopmental outcomes in young children, whereas postnatal SHS exposure was associated with poor academic achievement and neurocognitive performance in older children and adolescents. Furthermore, SHS exposure was associated with an increased risk of neurodevelopmental delay. CONCLUSIONS Recommendations should be made to the public to avoid sources of SHS and future research should investigate interactions between SHS exposure and other risk factors for delayed neurodevelopment and poor cognitive performance.