Table 2

Difference in FEF_25–75 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 asthmatics			Moderate and severe asthmatics
Group	Subgroup	n*	Coefficient (95% CI)†, ml/s 50 ppb O₃	Percentage (95% CI) change‡ FEF_25–75/50 ppb O₃	n	Coefficient (95% CI), ml/s 50 ppb O₃	Percentage (95% CI) change FEF_25–75/50 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 null	Placebo	29	−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)§
	Supplement	33	−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 effect		47.5 (−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 positive	Placebo	49	−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)
	Supplement	47	5.1 (−29.8 to 40.1)	0.3 (−1.6 to 2.2)	26	2.0 (−43.8 to 47.8)	0.1 (−2.4 to 2.6)
	Supplement effect		15.6 (−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)