Interactions between traffic air pollution and glutathione S-transferase genes on childhood asthma

Table 4 Association of ambient NO₂ level with asthma phenotypes, stratified by GSTP1 genotypes

	GSTT1				P for interaction
	Ile/Ile		Ile/Val or Val/Val
	OR	95%CI	OR	95%CI
Asthma
Low NO2	1		1		0.003
High NO2	0.78	(0.57, 1.06)	1.76	(1.15, 2.70)
Early-onset asthma
Low NO2	1		1		0.10
High NO2	0.88	(0.60, 1.29)	1.45	(0.86, 2.47)
Late-onset asthma
Low NO2	1		1		0.01
High NO2	0.63	(0.37, 1.07)	2.59	(1.24, 5.41)
Active asthma
Low NO2	1		1		0.06
High NO2	0.89	(0.57, 1.39)	1.93	(1.05, 3.57)
Asthma under medication
Low NO2	1		1		0.02
High NO2	0.88	(0.52, 1.49)	2.95	(1.37, 6.32)
Wheeze
Low NO2	1		1		0.01
High NO2	0.90	(0.69, 1.16)	1.54	(1.09, 2.18)

Models are adjusted for age, sex, family income, parental education, parental history of atopy, number of siblings, in utero exposures to maternal smoking, environmental tobacco smoke at home, gestational age and dampness at home.