Table 9.

 Hazard ratios (HR) and 95% confidence intervals for asthma from age 2 in relation to exposure to any, airway, and urinary tract/skin antibiotics in first year of life for children with siblings

	Crude			Adjusted*
	Cases†	HR (95% CI)		Cases†	HR (95% CI)
Any	568	0.93 (0.70 to 1.23)		523	0.90 (0.66 to 1.23)
Airway	550	0.98 (0.74 to 1.30)		505	1.01 (0.75 to 1.38)
Urinary tract/skin	120	0.99 (0.56 to 1.74)		107	0.63 (0.32 to 1.25)

*Adjusted for sex, birth weight, gestational age, mode of delivery, respiratory diagnoses as newborn, maternal age at delivery, parity, family situation, maternal exposure to antibiotics in fetal life, age as analysis time scale, and parity included as interaction term with age. Individuals with missing information on included variables excluded.

†All families discordant on asthma are included in analyses, but only those also discordant on exposure contribute to estimates in table, therefore number of cases is number of families with siblings discordant for both antibiotic exposure and asthma.