Table 3

Independent effects of gestational age, birth weight and male gender on durations of oxygen therapy and hospitalisation, and on being discharged home on oxygen, and contrasts between eras, adjusting for gestational age, birth weight and gender

	Variable
Outcome	Gestation-per week	Birth weight-per 100 g	Male	1991–92 versus 1997	2005 versus 1997
Duration of oxygen therapy (days)^*	−9.0 (−11.1 to −6.8)^†; p<0.001	−7.7 (−10.1 to −5.4)^†; p<0.001	13.0 (5.2 to 20.9)^†; p<0.001	11.9 (2.3 to 21.5)^†; p=0.15	11.4 (1.2 to 21.6)^†; p=0.029
Duration of the primary hospitalisation (days)	−4.7 (−6.4 to −3.0)^†; p<0.001	−5.9 (−7.8 to −4.0)^†; p<0.001	8.0 (1.6 to 14.3)^†; p−0.014	0.3 (7.5 to 8.0)^†; p=0.94	13.1 (4.9 to 21.3)^†; p=0.002
Discharged home on oxygen	0.76 (0.68 to 0.85)^‡; p<0.001	0.90 (0.81 to 1.0)^‡; p=0.048	1.82 (1.29 to 2.56)^‡; p=0.001	1.33 (0.88 to 2.01)^‡; p=0.18	0.96 (0.61 to 1.52)^‡; p=0.87

↵* During the primary hospitalisation only.
↵† Mean difference and 95% CI.
↵‡ OR and 95% CI.