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Table 3 Results from multivariate analysis (two time scales). Event-specific regression analyses based on Cox proportional regression models as described in main text. Proportionality could be assumed after the inspection of Schoenfelds’ residuals. Eventspecific hazard ratios are displayed with 95 %-confidence interval in brackets

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

Risk factors MODEL 1a basic time scale: ICU time MODEL 2a basic time scale: calendar time
  MRSA Death without MRSA Discharge without MRSA MRSA Death without MRSA Discharge without MRSA
Patient level covariates       
APACHE II score 11–20 vs. 0–10 1.36 (1.01–1.83) 2.05 (1.90–2.21) 0.62 (0.61–0.63) 1.40 (1.02–1.93) 2.14 (1.97 2.32) 0.64 (0.63–0.65)
APACHE II score 21–30 vs. 0–10 1.52 (1.11–2.09) 4.22 (3.90–4.56) 0.37 (0.36–0.38) 1.53 (1.08–2.17) 4.58 (4.22 4.97) 0.38 (0.37–0.39)
APACHE II score>31 vs. 0–10 1.52 (1.00–2.32) 6.83 (6.28–7.44) 0.25 (0.23–0.26) 1.86 (1.18–2.96) 7.73 (7.05 8.45) 0.25 (0.24–0.26)
Age (years) 0-40 vs. 61–80 1.07 (0.80–1.44) 0.62 (0.57–0.67) 1.08 (1.05–1.10) 0.97 (0.71–1.34) 0.62 (0.57 0.67) 1.05 (1.02–1.08)
Age (years) 40-60 vs. 61–80 0.97 (0.78–1.21) 0.81 (0.77–0.85) 1.00 (1.00–1.01) 0.93 (0.74–1.18) 0.81 (0.77 0.85) 0.99 (0.97–1.01)
Age (years)>80 vs. 61–80 0.73 (0.47–1.11) 1.60 (1.52–1.70) 1.12 (1.09–1.15) 0.71 (0.45–1.11) 1.63 (1.53 1.74) 1.13 (1.10–1.16)
Days in hospital before ICU admission:       
4-6 vs. 0–3 1.15 (0.79–1.68) 1.11 (1.03–1.20) 0.89 (0.86–0.92) 1.30 (0.86–1.97) 1.12 (1.03 1.22) 0.92 (0.89–0.96)
6-10 vs. 0–3 1.16 (0.78–1.73) 1.22 (1.13–1.32) 0.89 (0.86–0.92) 1.00 (0.64–1.56) 1.22 (1.12 1.33) 0.91 (0.88–0.95)
> 10 vs. 0–3 1.10 (0.82–1.48) 1.24 (1.17–1.31) 0.84 (0.81–0.86) 1.21 (0.88–1.66) 1.23 (1.16 1.32) 0.86 (0.83–0.88)
Type of diagnosis:       
Respiratory vs. cardiovascular 1.13 (0.86–1.49) 0.97 (0.92–1.02) 0.76 (0.74–0.77) 1.30 (0.96–1.75) 0.97 (0.92 1.03) 0.77 (0.75–0.79)
Gastrointestinal vs. cardiovascular 1.28 (0.95–1.73) 1.01 (0.95–1.07) 0.84 (0.82–0.86) 1.39 (1.00–1.94) 1.01 (0.94 1.08) 0.84 (0.82–0.86)
Central nervous system vs. cardiovascular 1.18 (0.40–1.55) 1.37 (1.30–1.45) 0.77 (0.75–0.78) 1.32 (0.98–1.77) 1.39 (1.30 1.47) 0.77 (0.75–0.79)
Other diagnoses vs. cardiovascular 0.90 (0.60–1.33) 0.84 (0.76–0.92) 0.86 (0.84–0.89) 0.93 (0.56–1.54) 0.84 (0.76 0.94) 1.01 (0.98–1.05)
Antibiotic treatment 48 h before and/or after ICU admission 1.12 (0.89–1.40) 1.10 (1.05–1.15) 0.76 (0.75–0.78) 1.29 (0.99–1.67) 1.11 (1.06 1.17) 0.72 (0.71–0.74)
Gender 1.14 (0.94–1.40) 1.01 (0.97–1.05) 1.00 (1.00–1.01) 1.22 (0.98–1.52) 1.00 (0.96 1.04) 0.99 (0.97–1.00)
Origin (hospital/ICU vs. community) 0.94 (0.75–1.17) 0.95 (0.91–1.00) 1.03 (1.01–1.05) 0.95 (0.74–1.21) 0.96 (0.91 1.01) 1.02 (1.00–1.04)
Trauma 1.20 (0.40–1.61) 0.67 (0.62–0.73) 0.74 (0.72–0.76) 1.29 (0.94–1.78) 0.66 (0.60 0.72) 0.74 (0.71–0.76)
Second time scale       
Calendar year of admission       
2007 vs. 2006 0.68 (0.51–0.92) 1.05 (0.98–1.13) 0.95 (0.93–0.98)    
2008 vs. 2006 0.57 (0.43–0.78) 1.11 (1.04–1.20) 0.92 (0.90–0.94)    
2009 vs. 2006 0.59 (0.44–0.79) 1.11 (1.03–1.19) 0.88 (0.86–0.91)    
2010+ vs. 2006 0.49 (0.36–0.67) 1.15 (1.07–1.24) 0.94 (0.91–0.96)    
Length of stay       
5-9 vs. 0–4 days     4.63 (3.30–6.48) 1.35 (1.28 1.42) 1.47 (1.44–1.50)
10-14 vs. 0–4 days     4.66 (3.18–6.84) 1.29 (1.20 1.38) 0.85 (0.82–0.87)
>14 vs. 0–4 days     5.42 (3.87–7.57) 1.05 (0.99 1.11) 0.61 (0.59–0.63)