Tobacco smoke exposure and chronic conditions of childhood.

Two remarkable articles by Kwok et al1 and Brion et al2 in this month’s Pediatrics tighten the evidence around tobacco smoke exposure and chronic conditions of childhood. Their work adds to previous research findings that demonstrated associations between tobacco smoke exposure and various childhood morbidities and mortality (Table 1).3 Indeed, 3 important categories of chronic conditions of childhood (asthma, obesity, and mental health disorders) have small-tomoderate independent associations with tobacco smoke exposure either during pregnancy or in the postnatal period. Dental caries are one of the most common chronic conditions of childhood, and a moderate independent association with tobacco smoke exposure has been described.4 Following a large Hong Kong birth cohort, Kwok et al1 found an association between tobacco smoke exposure of pregnant mothers and subsequent child overweight. The study is methodologically important, because it examined this effect among mothers who themselves did not smoke but were exposed by the father. That paternal smoking also may influence the developmental in utero origins of childhood obesity seems to be a novel finding. Brion et al2 found that a mother’s smoking was associated with her infant’s future mental health, specifically externalizing behaviors, which affect a child’s ability to participate in social activities and make friends. The authors used cross-population comparison,multiple adjustment for socioeconomic and psychological effects, maternal-paternal smoking comparisons, and specific use of behavioral subscales to increase biological plausibility for a specific intrauterine effect. Together, the results of these studies support the need for action to promote tobacco-control activities that would mitigate tobacco exposure throughout child development, starting in the prenatal period.