Parental inheritance and perinatal tobacco smoke exposure increase the gender-dependent risk of physician diagnosed asthma at preschool age

Results In this cohort study, 748 of the children with complete data were analyzed. 217 (29%) of children had positive parental allergic history, 191 (25.5%) of children had TSE history, and 186 (24.9%) of children had been diagnosed as asthma by a physician in the first 6 years of life. In a regression analysis, physician diagnosed asthma ever in the first 6 years of life were significantly associated with male gender (OR: 1.941, 95% CI: 1.371-2.748, p<0.001), either parent with allergic diseases (OR: 1.548, 95% CI: 1.047-2.288, p=0.028), and TSE (OR: 1.504, 95% CI: 1.038-2.179, p=0.031), but not significantly associated with preterm (p=0.801). TSE with more than 20 cigarettes per day made children significantly higher risky to have physician-diagnosed-asthma than those with smoke exposure less than 20 cigarettes per day or those without smoke exposure (35%, 25% and 22.7% respectively, p=0.003). TSE was not related to physician diagnosed rhinitis, dermatitis or allergic sensitization by 6 years of age (p>0.5). Besides, TSE and parental allergic history had synergistic influence on the physician diagnosed asthma ever in the 6 years of life. This synergistic influence was significant in girls, rather than in boys (Table 1).