Purpose: It remains controversial whether environmental tobacco smoke increases the risk of allergic diseases. The present prospective cohort study examined whether in utero exposure to maternal smoking and postnatal exposure to environmental tobacco smoke were associated with the development of wheeze, asthma, and atopic eczema in Japanese infants.
Methods: Study subjects included 763 infants. Data were obtained through the use of questionnaires completed by the mother during pregnancy and at 2 to 9 and 16 to 24 months postdelivery. Information regarding maternal smoking during pregnancy and postnatal exposure to environmental tobacco smoke was collected at 2 to 9 months postdelivery, and information on allergic symptoms was collected when the infant was between 16 to 24 months of age. Cases were defined according to criteria of the International Study of Asthma and Allergies in Childhood for wheeze and atopic eczema. Additionally, doctor-diagnosed asthma and atopic eczema were identified. Adjustment was made for maternal age, family income, maternal and paternal education, parental history of asthma, atopic eczema, allergic rhinitis, indoor domestic pets, baby's older siblings, baby's sex, birth weight, and time of surveys.
Results: The cumulative incidence of wheeze, atopic eczema, doctor-diagnosed asthma, and doctor-diagnosed atopic eczema was 22.1%, 18.6%, 4.3%, and 9.0%, respectively. Maternal smoking during pregnancy was not related to the risk of wheeze, whereas postnatal maternal smoking in the same room as the child increased the risk of wheeze. No significant association was observed between perinatal tobacco smoke exposure and the development of asthma and atopic eczema.
Conclusions: Our findings suggest that postnatal maternal smoking might be associated with an increased risk of wheeze in Japanese infants.