Table 4.

The combined effects of pairs of environmental exposures on asthma age-of-onset

	Paternal smoking	Serious chest illness	Brick house type
Carpet exposure	0.8 (0.6–1.3)	3.2 (1.7–6.0)***	1.7 (1.1–2.5)*
Paternal smoking	NA	1.2 (0.6–2.5)	0.9 (0.6–1.4)
Serious chest illness	NA	NA	2.2 (1.2–4.0)*

Results are presented as: odds ratio (95% confidence interval).

^*P < 0.05;

^**P < 0.0005.