Table 6 Joint effects of distance of residence from major road, EPHX1 metabolic phenotypes and GSTP1 Ile105Val on lifetime asthma (N  = 2702)
Distance of residence from major road (metres)GSTP1 Ile105ValEPHX1 metabolic phenotypesNo asthma(N*)Lifetime asthma(N*)OR† (95% CI)
⩾75Ile/ValLow/intermediate7201321.19 (0.88 to 1.61)
⩾75Val/ValLow/intermediate215290.94 (0.59 to 1.50)
⩾75Ile/IleHigh141231.03 (0.61 to 1.71)
⩾75Ile/ValHigh158311.35 (0.85 to 2.15)
⩾75Val/ValHigh38142.63 (1.34 to 5.18)
<75Ile/IleLow/intermediate144231.01 (0.60 to 1.69)
<75Ile/ValLow/intermediate171280.89 (0.54 to 1.44)
<75Val/ValLow/intermediate48111.46 (0.71 to 3.03)
<75Ile/IleHigh3191.71 (0.75 to 3.87)
<75Ile/ValHigh30122.61 (1.22 to 5.58)
<75Val/ValHigh568.91 (2.40 to 33.12)
p = 0.04‡
  • *Children with missing data on distance of residence from major road and GSTP1 Ile105Val were excluded.

  • †ORs adjusted for age, sex, race/ethnicity, in utero exposure to maternal smoking, number of smokers at home, community of residence, parental education, health insurance and parental history of asthma.

  • ‡p value for EPHX1 activity phenotype by distance of residence from a major road and by GSTP1 Ile105Val genotype interaction was obtained from likelihood ratio test from a non-stratified model with appropriate interaction terms and was based on 7df.