Table 2

Difference in FEF25–75 related to ozone concentration on the day before spirometric testing according to antioxidant supplementation groups within GSTM1 genotypes among asthmatic children in Mexico City

All asthmaticsModerate and severe asthmatics
GroupSubgroupn*Coefficient (95% CI)†, ml/s 50 ppb O3Percentage (95% CI) change‡ FEF25–75/50 ppb O3nCoefficient (95% CI), ml/s 50 ppb O3Percentage (95% CI) change FEF25–75/50 ppb O3
*The number of subjects in each group is given. The number of observations is: GSTM1 null (placebo 654, supplement 732), GSTM1 positive (placebo 1065, supplement 1039).
†Results and 95% confidence intervals from generalised estimating equation models adjusted for age, height, use of bronchodilator, respiratory symptoms on the day of the spirometric test, minimum temperature, and time since the beginning of the study. Ozone level is 1 hour maximum. During the observation period the mean (SD) 1 hour maximum ozone level was 102 (47) ppb (range 12–309). The Mexican standard is 110 ppb.
‡Percentage change from baseline FEF25−75 for the individual stratum.
§p⩽0.01. All p values were obtained by t test comparing coefficients between the two groups.
¶0.01<p<0.05.
**0.05<p<0.10.
GSTM1 nullPlacebo29−50.5 (−90.1 to−10.9)§−2.9 (−5.2 to −0.6)§18−80.8 (−132.7 to −28.9)§−4.7 (−7.7 to −1.7)§
Supplement33−3.0 (−40.7 to 34.7)−0.2 (−2.3 to1.9)21−7.3 (−54.0 to 39.5)−0.3 (−3.1 to 2.4)
Supplement effect47.5 (−7.2 to 102.2)**2.7 (−0.2 to 5.8)**73.5 (3.8 to 143.2)¶4.4 (0.3 to 8.4)¶
GSTM1 positivePlacebo49−10.5 (−38.7 to 17.7)−0.6 (−2.1 to 0.9)17−34.4 (−75.6 to 6.8)−1.9 (−4.4 to 0.5)
Supplement475.1 (−29.8 to 40.1)0.3 (−1.6 to 2.2)262.0 (−43.8 to 47.8)0.1 (−2.4 to 2.6)
Supplement effect15.6 (−29.2 to 60.4)0.9 (−1.6 to 3.3)36.4 (−29.0 to 101.9)2.0 (−1.7 to 5.7)