Table 2.

Crude and adjusted analysis of the effects of independent variables on hospitalization in the first year of life, among boys. 1993 Pelotas (Brazil) birth cohort, 2004-2005 follow-up.

Variables	Crude analysis			Adjusted analysis *
	Cumulative incidence ratio	95%CI	p-value	Cumulative incidence ratio	95%CI	p-value
First level
Skin color **			0.005			0.063
White	1.00			1.00
Black/Mixed	1.31	1.09; 1.59		1.20	0.99; 1.45
Family income in 1993 (minimum wages) ***			< 0.001			< 0.001
> 10.0	1.00			1.00
6.1-10.0	1.29	0.66; 2.55		1.38	0.69; 2.76
3.1-6.0	1.85	1.05; 3.23		1.90	1.06; 3.40
1.1-3.0	2.52	2.48; 4.31		2.57	1.47; 4.51
≤ 1.0	2.95	1.71; 5.12		2.94	1.66; 5.24
Second level
Mother smoked during pregnancy **			0.042			0.961
No	1.00			1.00
Yes	1.21	1.01; 1.45		1.00	0.83; 1.21
Father smoked during pregnancy **			0.007			0.033
No	1.00			1.00
Yes	1.27	1.07; 1.52		1.21	1.01; 1.43
Gestational age (weeks) **			< 0.001			< 0.001
≥ 37	1.00			1.00
< 37	2.65	2.20; 3.19		1.85	1.48; 2.31
Low birthweight (< 2,570g) **			< 0.001			< 0.001
No	1.00			1.00
Yes	2.84	2.37; 3.41		2.00	1.60; 2.49

^*Adjusted analysis: the effect of each exposure on the outcome was adjusted for variables in the same or in a higher level

^**Wald’s test for heterogeneity

^***Wald’s test for linear trend.