Multiple time scales in modeling the incidence of infections acquired in intensive care units

Table 4 Results from multivariate analysis (subdistribution analysis). Regression analyses based on adapted Cox proportional regression model (Fine & Gray model) as described in main text. Proportionality could be assumed after the inspection of Schoenfelds’ residuals. Subdistribution hazard ratios are displayed with 95 %-confidence interval in brackets

Risk factors	MODEL 3a one time scale subdistribution	MODEL 3b two time scales subdistribution
	approach basic time scale: ICU time	approach basic time scale: ICU time
	subdistribution MRSA
Patient level covariates
APACHE II score 11–20 vs. 0–10	3.05 (2.27–4.11)	3.06 (2.27–4.13)
APACHE II score 21–30 vs. 0–10	4.92 (3.58–6.76)	4.96 (3.61–6.82)
APACHE II score>31 vs. 0–10	5.71 (3.77–8.64)	5.79 (3.82–8.76)
Age (years) 0–40 vs. 61–80	1.14 (0.86–1.53)	1.13 (0.85–1.51)
Age (years) 40–60 vs. 61–80	1.04 (0.83–1.29)	1.04 (0.84–1.30)
Age (years)>80 vs. 61–80	0.46 (0.30–0.71)	0.47 (0.31–0.71)
Days in hospital before ICU admission:
4-6 vs. 0–3	1.32 (0.90–1.92)	1.32 (0.91–1.93)
6-10 vs. 0–3	1.44 (0.97–2.15)	1.44 (0.97–2.15)
> 10 vs. 0–3	1.32 (0.98–1.77)	1.32 (0.98–1.78)
Type of diagnosis:
Respiratory vs. cardiovascular	1.69 (1.29–2.21)	1.71 (1.31–2.25)
Gastrointestinal vs. cardiovascular	1.77 (1.31–2.38)	1.76 (1.31–2.38)
Central nervous system vs. cardiovascular	1.59 (1.21–2.09)	1.60 (1.22–2.11)
Other diagnoses vs. cardiovascular	1.39 (0.96–2.02)	1.40 (0.96–2.03)
Antibiotic treatment 48 h before and/or after ICU admission	1.39 (1.11–1.73)	1.33 (1.06–1.66)
Gender	1.18 (0.96–1.44)	1.17 (0.96–1.43)
Origin (hospital/ICU vs. community)	0.95 (0.76–1.19)	0.96 (0.76–1.20)
Trauma	1.87 (1.34–2.49)	1.80 (1.35–2.41)
Calendar year of admission
2007 vs. 2006		0.71 (0.53–0.96)
2008 vs. 2006		0.64 (0.47–0.86)
2009 vs. 2006		0.73 (0.55–0.97)
2010+ vs. 2006		0.52 (0.38–0.70)

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