Background
Genetic inheritance and perinatal tobacco smoke exposure (TSE) have been proven to be critical for the development of childhood allergic diseases [1, 2]. This study investigated the interactive roles of parental allergic histories and TSE on the development of childhood asthma at 6 years old.
Methods
A birth cohort in southern Taiwan was studied. Information about parental allergic histories, gender, prematurity, TSE, and childhood allergic disease ever diagnosed by a physician were acquired from questionnaire during follow up. Children were asked to follow up at 6 years of age for allergic questionnaire and sensitization examination (CAP system).
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).
Table 1.
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 boys
| All | physician diagnosed asthma | OR | 95%CI | p (compared with A) | |
|---|---|---|---|---|---|
| parent allergic disorder -, TSE- (A) | 30/161 | 18.60% | 1 | ||
| parent allergic disorder +, TSE- | 97/396 | 24.00% | 1.417 | 0.896-2.240 | 0.135 |
| parent allergic disorder -, TSE+ | 13/56 | 23.20% | 1.32 | 0.632-2.757 | 0.459 |
| parent allergic disorder +, TSE+ | 46/135 | 34.10% | 2.257 | 1.325-3.846 | 0.002 |
| Girls | p (compared with A1) | ||||
| parent allergic disorder -, TSE- (A1) | 4/72 | 5.60% | 1 | ||
| parent allergic disorder +, TSE- | 38/196 | 19.40% | 4.089 | 1.404-11.905 | 0.006 |
| parent allergic disorder -, TSE+ | 3/23 | 13.00% | 2.55 | 0.526-12.353 | 0.231 |
| parent allergic disorder +, TSE+ | 20/61 | 32.80% | 8.293 | 2.649-25.964 | <0.001 |
| Boys | p (compared with A2) | ||||
| parent allergic disorder -, TSE- (A2) | 28/89 | 29.20% | 1 | ||
| parent allergic disorder +, TSE- | 59/200 | 29.50% | 1.014 | 0.586-1.755 | 0.961 |
| parent allergic disorder -, TSE+ | 10/33 | 30.30% | 1.054 | 0.441-2.519 | 0.907 |
| parent allergic disorder +, TSE+ | 26/74 | 35.10% | 1.313 | 0.678-2.541 | 0.419 |
Conclusions
In the prospective cohort study, we found that male gender, parental allergic history, and TSE were significantly associated with physician diagnosed asthma by 6 years of age. TSE and parental allergic history had synergistic effect on the physician diagnosed asthma by 6 years of age. This synergistic influence was significant in girls, rather than boys.