title: Early environmental determinants of asthma risk in a high-risk birth cohort.
abstract: Environmental exposures during early life have been suggested to have the greatest impact on childhood asthma. Our aim was to evaluate the risk factors associated with asthma at age 7 yr in a high-risk cohort that participated in a randomized controlled study on the primary prevention of asthma. Indoor exposures were characterized before birth and at 2 weeks, 4, 8, 12, 18, and 24 months after birth and again at 7 yr. Nasal scrapings for respiratory viruses were done at the same intervals during the first 2 yr. At age 7, the children were assessed by a pediatric allergist and had allergy skin tests. Logistic regression analysis was undertaken to evaluate the effect of exposures on asthma for the entire cohort with adjustment for group allocation. In addition to the lower risk of asthma in the intervention group, we found a higher prevalence of asthma at age 7 for males, those having a positive history of asthma in mother, father, or older siblings, for children residing in Winnipeg and for atopic subjects. Upon adjustment for intervention group assignment and baseline factors, significant environmental risk factors during year 1 included dog ownership and respiratory syncytial viral infection detected at 12 months while maternal smoking was protective. Dog ownership was a significant risk factor in year 2, but highly correlated with dog ownership in year 1. Indoor environmental exposures during year 7 were not associated with asthma at age 7. Maternal smoking at year 7 was associated with a reduced risk of asthma at 7 yr. Early-life exposures were more important determinants than those in later years. A 'window of opportunity' exists for intervention measures to be applied.
authors.affiliation: Occupational and Environmental Lung Disease Unit, Respiratory Division, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada. myeung@interchange.ubc.ca
authors.forename: Moira
authors.initials: M
authors.lastname: Chan-Yeung
authors.forename: Richard G
authors.initials: RG
authors.lastname: Hegele
authors.forename: Helen
authors.initials: H
authors.lastname: Dimich-Ward
authors.forename: Alexander
authors.initials: A
authors.lastname: Ferguson
authors.forename: Michael
authors.initials: M
authors.lastname: Schulzer
authors.forename: Henry
authors.initials: H
authors.lastname: Chan
authors.forename: Wade
authors.initials: W
authors.lastname: Watson
authors.forename: Allan
authors.initials: A
authors.lastname: Becker
mesh_terms: D000485:Allergens / Q000276:immunology*; D000818:Animals; D001249:Asthma / Q000209:etiology* / Q000276:immunology / Q000517:prevention & control; D002170:Canada; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D012307:Risk Factors
chemical_list: D000485:Allergens