TABLE 6.

JOINT EFFECTS OF ACTIVE SMOKING AND ALLERGY ON NEWLY DIAGNOSED ASTHMA, RELATIVE RISK AND 95% CONFIDENCE INTERVAL, CHILDREN'S HEALTH STUDY 1993–2003

Smoking in Previous Week	Children without Allergies	Children with Allergies	Interaction p Value
None	1 (—)	1.1 (0.8–1.4)	0.006
⩽ 6 Cigarettes	2.4 (1.1–4.9)	0.7 (0.1–5.1)
7+ Cigarettes	5.2 (2.4–10.9)	0.7 (0.1–5.1)

Relative risks (Hazard ratios) and corresponding 95% confidence intervals were obtained from Cox's proportional hazard model with separate baseline hazard for sex and age (in yr) at study entry. All models are adjusted for race/ethnicity, community, maternal smoking during the children's postnatal period, and numbers of other smokers in the home.