Gender-specific differences in effects of prenatal and postnatal environmental tobacco smoke exposure on respiratory symptoms in 23,474 children with and without allergic predisposition: results from 25 districts of northeast China.

To assess the interaction of environmental tobacco smoke (ETS) exposure and allergic predisposition regarding respiratory health among Chinese children, a sample of 23,474 children (6-13 years old) was studied from 25 districts in Liaoning province, China. The results showed that children without allergic predisposition were more susceptible to ETS than children with allergic predisposition. Among children without allergic predisposition, ETS exposure was associated with more respiratory symptoms and diseases in boys than in girls; In utero ETS exposure was associated with history of asthma (OR, 1.86; 95% CI, 1.44-2.40) and current asthma (OR, 2.25; 95% CI, 1.48-3.44) only among boys without allergic predisposition. Among children with allergic predisposition, more associations between ETS exposure and respiratory symptoms and diseases were detected in girls. In conclusion, ETS exposure was more evident in boys without family atopy history and more associations were detected in girls with family atopy history.