Table 2.

Predictive patient factors associated with Day-90 mortality in critically ill patients older than 70 years old with COVID-19 stratified on the center variable

	No.	Univariate HR (95% CI)	P value	Multivariate HR (95% CI)	P value
Age, years	1199	–	< 0.001	–
70–75		–		–
75–79		1.32 (1.08–1.60)		–
80–84		2.09 (1.64–2.68)		–
85–91		4.09 (2.97–5.65)		–
Clinical Frailty Scale	1085	–	< 0.001	–	< 0.001
1–3		–		–
4		2.14 (1.71–2.68)		2.24 (1.63–3.09)
5–9		2.81 (2.17–3.64)		2.83 (1.96–4.08)
Body mass index, kg/m2	1096		0.435	–	0.103
< 25				–
25–29		0.96 (0.77–1.20)		1.10 (0.83–1.48)
30–34		0.85 (0.64–1.11)		0.78 (0.55–1.12)
35–39		0.89 (0.61–1.31)		0.90 (0.53–1.51)
≥ 40		1.33 (0.83–2.13)		1.26 (0.72–2.22)
Diabetes	1184	1.43 (1.20–1.71)	< 0.001	1.42 (1.10–1.82)	0.043
Hypertension	1189	1.03 (0.87–1.23)	0.726	0.87 (0.68–1.12)	0.697
Immunodepression	1186	1.31 (0.99–1.74)	0.066	0.97 (0.63–1.48)	0.298
Time between first signs and ICU admission	1109		< 0.001		0.003
< 4 days		–		–
4–7 days		0.88 (0.70–1.12)		0.87 (0.63–1.18)
≥ 8 days		0.50 (0.40–0.64)		0.61 (0.44–0.84)
SOFA Cardiovascular component ≥3	1160	1.74 (1.47–2.07)	< 0.001	2.13 (1.66–2.74)	< 0.001
SOFA renal component ≥3	1140	1.84 (1.37–2.49)	< 0.001	1.39 (0.94–2.05)	0.909
Invasive mechanical ventilation at Day-1	1199	1.66 (1.38–1.99)	< 0.001	–
Renal replacement therapy at Day-1	1188	2.50 (1.67–3.73)	< 0.001	–
ICU admission after March 29th	1199	0.67 (0.56–0.80)	< 0.001	0.70 (0.55–0.89)	< 0.001
PaO2/FiO2 ratio	868		< 0.001	–	0.001
200 < PaO2/FiO2		–		–
100 < PaO2/FiO2 ≤ 200		1.14 (0.90–1.44)		1.28 (0.97–1.69)
PaO2/FiO2 ≤ 100		1.68 (1.30–2.16)		2.35 (1.73–3.19)

Age, invasive mechanical ventilation and renal replacement therapy variables were excluded from multivariate analysis for multicollinearity issue

CI confidence interval, HR hazard ratio, ICU intensive care unit, SOFA Sequential Organ Failure Assessment