Environmental Health Perspectives
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Environmental Health Perspectives (EHP) is a monthly journal of peer-reviewed research and news on the impact of the environment on human health. EHP is published by the National Institute of Environmental Health Sciences and its content is free online. Print issues are available by paid subscription.DISCLAIMER
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Environmental Health Perspectives Volume 112, Number 6, May 2004
Early-Life Environmental Risk Factors for Asthma: Findings from the Children's Health Study

Muhammad Towhid Salam, Yu-Fen Li, Bryan Langholz, and Frank Davis Gilliland

Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA

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. Key words: , , , , , , , , . Environ Health Perspect 112:760-765 (2004) . doi:10.1289/ehp.6662 available via http://dx.doi.org/ [Online 9 December 2003]

Address correspondence to F.D. Gilliland, Department of Preventive Medicine, USC Keck School of Medicine, 1540 Alcazar St., CHP 236, Los Angeles, CA 90033 USA. Telephone: (323) 442-1096. Fax: (323) 442-3272. E-mail: gillilan@usc.edu

This study was supported by the California Air Resources Board (contract 94-331) , the National Institute of Environmental Health Sciences, (grants 1P01 ES09581 and 5P30 ES07048) , the U.S. Environmental Protection Agency (grant R826708-01) , the National Heart, Lung, and Blood Institute (grant 1R01HL61768) , and the Hastings Foundation.

The authors declare they have no competing financial interests.

Received 13 August 2003 ; accepted 9 December 2003.

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