title: Early-life environmental risk factors for asthma: findings from the Children's Health Study.
abstract: Early-life experiences and environmental exposures have been associated with childhood asthma. To investigate further whether the timing of such experiences and exposures is associated with the occurrence of asthma by 5 years of age, we conducted a prevalence case-control study nested within the Children's Health Study, a population-based study of > 4,000 school-aged children in 12 southern California communities. Cases were defined as physician-diagnosed asthma by age 5, and controls were asthma-free at study entry, frequency-matched on age, sex, and community of residence and countermatched on in utero exposure to maternal smoking. Telephone interviews were conducted with mothers to collect additional exposure and asthma histories. Conditional logistic regression models were fitted to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Asthma diagnosis before 5 years of age was associated with exposures in the first year of life to wood or oil smoke, soot, or exhaust (OR = 1.74; 95% CI, 1.02-2.96), cockroaches (OR = 2.03; 95% CI, 1.03-4.02), herbicides (OR = 4.58; 95% CI, 1.36-15.43), pesticides (OR = 2.39; 95% CI, 1.17-4.89), and farm crops, farm dust, or farm animals (OR = 1.88; 95% CI, 1.07-3.28). The ORs for herbicide, pesticide, farm animal, and crops were largest among children with early-onset persistent asthma. The risk of asthma decreased with an increasing number of siblings (ptrend = 0.01). Day care attendance within the first 4 months of life was positively associated with early-onset transient wheezing (OR = 2.42; 95% CI, 1.28-4.59). In conclusion, environmental exposures during the first year of life are associated with childhood asthma risk.
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: Muhammad Towhid
authors.initials: MT
authors.lastname: Salam
authors.forename: Yu-Fen
authors.initials: YF
authors.lastname: Li
authors.forename: Bryan
authors.initials: B
authors.lastname: Langholz
authors.forename: Frank Davis
authors.initials: FD
authors.lastname: Gilliland
mesh_terms: D017668:Age of Onset; D000818:Animals; D001249:Asthma / Q000453:epidemiology / Q000209:etiology*; D002140:California / Q000453:epidemiology; D002244:Carbon; D016022:Case-Control Studies; D002675:Child, Preschool; D003058:Cockroaches; D004781:Environmental Exposure; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016017:Odds Ratio; D010575:Pesticides / Q000506:poisoning; D015995:Prevalence; D012307:Risk Factors; D012906:Smoke; D001335:Vehicle Emissions
chemical_list: D010575:Pesticides; D012906:Smoke; D001335:Vehicle Emissions; D002244:Carbon