Table 4.

Risk factors related to longer length of hospital stay. Univariate and multivariate Cox regression analysis

	Univariable analysis			Multivariable analysis
	HR	95% CI	P value	HR	95% CI	P value
Sex (male)	0.956	0.870–1.051	0.354
Gestational age (weeks)	1.073	1.029–1.120	< 0.001	1.077	1.033–1.122	< 0.001
Birth weight (g)	1.000	1.000–1.000	0.033	1.000	1.000–1.000	0.766
Weight at admission (Kg)	1.147	1.093–1.203	< 0.001	1.003	0.904–1.112	0.960
Age (months)	1.057	1.032–1.083	< 0.001	1.062	1.035–1.091	< 0.001
Underlying disease	0.685	0.484–0.971	0.033	0.578	0.400–0.836	0.004
Prematurity	0.750	0.577–0,974	0.031	1.049	0.705–1.562	0.812
Caesarean section	0.951	0.779–1.161	0.620
Personal history atopy	0.916	0.637–1.319	0.638
Apnea	0.417	0.275–0.632	< 0.001	0.725	0.465–1.130	0.155
Sepsis	0.275	0.129–0.585	< 0.001	0.253	0.117–0.548	< 0.001
Breastfeeding	0.910	0.748–1.106	0.341
*Ventilatory support	0.347	0.283–0.425	< 0.001	0.332	0.267–0.413	< 0.001
PICU admission	0.413	0.329–0.518	< 0.001	0.863	0.623–1.196	0.376
RSV	0.883	0.707–1.104	0.275	0.979	0.747–1.283	0.877
Rhinovirus/enterovirus	1.038	0.853–1.262	0.713
Coronavirus	0.679	0.486–0.949	0.023	0.770	0.523–1.134	0.185
Bocavirus	0.802	0.574–1.120	0.195	0.956	0.627–1.457	0.833
Parainfluenza	0.812	0.568–1.161	0.254
Human Metapneumovirus	0.766	0.511–1.148	0.197	0.740	0.486–1.126	0.159
Adenovirus	1.293	0.815–2.049	0.275
Infuenza	0.774	0.481–1.243	0.289
Viral coinfection	0.769	0.635–0.932	0.007
†Viral co-detections
None			0.011			0.002
2 Virures ≥ 3 Viruses	0.831 0.644	0.672–1.029 0.474–0.875	0.090 0.005	0.858 0.568	0.688–1.071 0.410–0.785	0.176 < 0.001

h and 95% CIs are from Cox regression. Bold indicates statistical significance (p < 0.05)

RSV Respiratory syncytial virus

* Ventilatory support includes: HFNC oxygen therapy, NIV and IMV.

† Viral co-detection: Reference group = none