Background: Because asthma has been associated with exercise and ozone exposure, an association likely mediated by oxidative stress, we hypothesised that glutathione-S-transferase (GST)P1, GSTM1, exercise and ozone exposure have interrelated effects on the pathogenesis of asthma.
Methods: Associations of the well characterised null variant of GSTM1 and four single nucleotide polymorphisms (SNPs) that characterised common variation in the GSTP1 locus with new onset asthma in a cohort of 1610 school children were examined. Children’s exercise and ozone exposure were classified using participation in team sports and community annual average ozone levels, respectively.
Results: A two SNP model involving putatively functional variants (rs6591255, rs1695 (Ile105Va)) best captured the association between GSTP1 and asthma. The risk of asthma was lower for those with the Val allele of Ile105Val (hazard ratio (HR) 0.60, 95% CI 0.4 to 0.8) and higher for the variant allele of rs6591255 (HR 1.40, 95% CI 1.1 to 1.9). The risk of asthma increased with level of exercise among ile105 homozygotes but not among those with at least one val105 allele (interaction p value = 0.02). The risk was highest among ile105 homozygotes who participated in ⩾3 sports in the high ozone communities (HR 6.15, 95% CI 2.2 to 7.4). GSTM1 null was independently associated with an increased risk of asthma and showed little variation with air pollution or GSTP1 genotype. These results were consistent in two independent fourth grade cohorts recruited in 1993 and 1996.
Conclusion: Children who inherit a val105 variant allele may be protected from the increased risk of asthma associated with exercise, especially in high ozone communities. GSTM1 null genotype was associated with an increased risk of asthma.
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Additional supplement published online only at http://thorax.bmj.com/content/vol64/issue3
Funding: This work was supported by the Southern California Environmental Health Sciences Center (grant No 5P30ES007048) funded by the National Institute of Environmental Health Sciences; the Children’s Environmental Health Center (grant Nos 5P01ES009581, R826708-01 and RD831861-01) funded by the National Institute of Environmental Health Sciences and the Environmental Protection Agency; the National Institute of Environmental Health Sciences (grant No 5P01ES011627); the National Heart, Lung and Blood Institute (grant Nos 5R01HL061768 and 5R01HL076647); and the Hastings Foundation.
Competing interests: None.
Ethics approval: Ethics approval was obtained.