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 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. Key words: asthma, breast-feeding, cockroach, day care, farm environment, herbicide, pesticide, sibship size, wood smoke. 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. The full version of this article is available for free in HTML or PDF formats. |