Table 2.

Rates and Numbers of Admissions to Hospital at Five to 11 Years of Age in Children Born in Norway During 1999 and 2000 at a Gestational Age < 28 Weeks or with a Birth Weight < 1000 Grams and a Regional Control Group Assembled at 11 Years of Age

	All participants			Neonatal bronchopulmonary dysplasiab			Gestational age in weeksc
	Cases n = 232	Controls n = 57	p-values d	Yes n = 165	No n = 207	p-values d	≤25 n = 99	26–27 n = 188	≥28 n = 85	p-valuesd ≤ 25 vs. 26–27	p-valuesd 26–27 vs. ≥28
Admitted 5–11 years of agea
Admitted	67 (29%)	7 (13%)	0.010	34 (31%)	33 (28%)	0.597	18 (36%)	31 (26%)	18 (30%)	0.193	0.576
Admitted for respiratory cause	8 (4%)	1 (2%)	1.000	6 (6%)	2 (2%)	0.158	3 (6%)	3 (3%)	2 (3%)	0.362	1.000
Admissionse	138	7	0.006	77	61	0.451	36	64	38	0.192	0.482
Admissions for respiratory cause	16 (12%)	1 (14%)	0.507	14 (41%)	2 (6%)	0.117	6	8	2	0.273	0.773
Number of admissions per child
Once	38 (57%)	7 (100%)	0.083	17 (50%)	21 (64%)	0.355	11 (61%)	19 (61%)	8 (44%)	0.659	0.463
Twice	14 (21%)	0		7 (21%)	7 (21%)		2 (11%)	6 (19%)	6 (33%)
Three times or more	15 (22%)	0		10 (29%)	5 (15%)		5 (28%)	6 (19%)	4 (22%)

^aFigures are numbers of admitted children (% of group) and admissions

^bDefined as assisted ventilation or oxygen supplementation at 36 weeks postmenstrual age

^cFor analysis regarding gestational age, the fraction born at 26–27 weeks were selected as the reference category (those with gestational age ≥ 28 had birth weights < 1000 grams)

^dIndependent samples Mann-Whitney’s U Test or χ² test, as appropriate. Boldface denotes significant group differences

^eInformation on admissions was given for 229 subjects