Do Grandmaternal Smoking Patterns Influence the Etiology of Childhood Asthma?

BACKGROUND: Animal data suggest that tobacco smoke exposure of a mother when she is in utero influences DNA methylation patterns in her offspring and that there is an effect on the respiratory system, particularly airway responsiveness. The only study, to our knowledge, in humans suggests that there is a similar effect on asthma. The present study tests whether an association with respiratory problems can be confirmed in a large population study and aims to determine whether in utero exposure of the father has similar effects on his offspring. METHODS: Information from the Avon Longitudinal Study of Parents and Children was used to compare the offspring of women and of men who had themselves been exposed to cigarette smoke in utero; separate analyses were performed for children of women smokers and nonsmokers. The outcome measures were trajectories of history of early wheezing, doctor-diagnosed asthma by age 7 years, and results of lung function and methacholine challenge tests at 8 years. A variety of social and environmental factors were taken into account; offspring sexes were examined separately. RESULTS: There was no association with any outcome in relation to maternal prenatal exposure. There was some evidence of an increase in asthma risk with paternal prenatal exposure when the study mother was a nonsmoker (adjusted OR, 1.17; 95% CI, 0.97-1.41). This was particularly strong for girls (adjusted OR, 1.39; 95% CI, 1.04-1.86). CONCLUSIONS: We did not find that maternal prenatal exposure to her mother’s smoking had any effect on her children’s respiratory outcomes. There was suggestive evidence of paternal prenatal exposure being associated with asthma and persistent wheezing in the granddaughters.