Table 2. Univariate analysis between wheeze and covariates in three age groups.

		3 month group			18 month group			36 month group
		OR	95%CI	P	OR	95%CI	P	OR	95%CI	P
Gender
	Female	reference	―	―	reference	―	―	reference	―	―
	Male	1.51	1.40–1.63	<0.001	1.43	1.36–1.51	<0.001	1.37	1.29–1.46	<0.001
Birth season
	Spring (Mar. to May)	reference	―	―	reference	―	―	reference	―	―
	Summer (Jun. to Aug.)	1.23	1.10–1.36	<0.001	0.85	0.79–0.92	<0.001	1.00	0.91–1.09	0.981
	Autumn (Sep. to Nov.)	1.09	0.98–1.21	0.118	0.81	0.75–0.88	<0.001	1.22	1.12–1.33	<0.001
	Winter (Dec. to Feb.)	0.91	0.81–1.01	0.084	0.80	0.74–0.87	<0.001	1.14	1.05–1.25	0.003
Birth order
	First	reference	―	―	reference	―	―	reference	―	―
	Second and after	1.21	1.12–1.31	<0.001	1.05	1.00–1.11	0.07	0.96	0.90–1.02	0.208
Paternal bronchial asthma
	No	reference	―	―	reference	―	―	reference	―	―
	Yes	1.45	1.29–1.64	<0.001	1.75	1.60–1.92	<0.001	2.40	2.18–2.64	<0.001
Maternal bronchial asthma
	No	reference	―	―	reference	―	―	reference	―	―
	Yes	1.75	1.56–1.96	<0.001	2.16	1.98–2.36	<0.001	2.79	2.55–3.05	<0.001
Parental allergic disease
	No	reference	―	―	reference	―	―	reference	―	―
	Yes	1.36	1.24–1.49	<0.001	1.50	1.41–1.60	<0.001	1.83	1.70–1.97	<0.001