Table 3.

Ordinary, marginal and multilevel logistic regression results: Odds ratios, OR, describing associations with 30-day mortality for patient-level and hospital-level characteristics

Risk factor	Ordinary		Marginal		Multilevel*
	OR	95% CI	OR	95% CI	OR	95% CI
Patient-level
Age group (< 60 y, reference group):
60-70 y	1.5	(1.2,2.0)	1.5	(1.2-1.8)	1.5	(1.2,2.0)
70-80 y	2.7	(2.1,3.4)	2.4	(2.0-3.0)	2.7	(2.1,3.3)
80+y	3.6	(2.8,4.8)	3.3	(2.7-4.5)	3.7	(2.8,4.9)
Gender (female vs. male)	1.3	(1.1,1.6)	1.3	(1.1-1.5)	1.3	(1.1,1.6)
NYHA Class (I&II, reference group):
III	1.3	(1.1,1.6)	1.3	(1.1-1.6)	1.4	(1.1,1.6)
IV	1.7	(1.4,2.1)	1.6	(1.3-2.0)	1.7	(1.4,2.2)
Urgency of procedure (elective, reference group):
Urgent	2.0	(1.6,2.4)	1.8	(1.5-2.2)	2.0	(1.6,2.4)
Emergency/salvage	5.4	(4.3,7.0)	4.9	(4.0-6.0)	5.5	(4.3,7.0)
Ejection fraction estimate (Mild, > 45%, reference group):
Moderate (30-45%)	1.4	(1.2,1.8)	1.3	(3.0-1.6)	1.4	(1.2,1.8)
Severe (< 30%)	2.3	(1.8,2.9)	2.2	(1.8-2.7)	2.3	(1.8,2.9)
Hypercholesterolaemia	1.0	(0.8, 1.1)	1.0	(0.8-1.1)	1.0	(0.8,1.2)
Preoperative dialysis	2.2	(1.5,3.2)	2.2	(1.5-3.0)	2.2	(1.5,3.2)
Previous cardiac surgery	1.6	(1.3,2.0)	1.6	(1.3-2.0)	1.7	(1.3,2.0)
Procedure type (CABG, reference group):
Valve(s)	1.7	(1.3, 2.2)	1.6	(1.2-2.0)	1.7	(1.3, 2.2)
Valve(s)+CABG	2.2	(1.8, 2.8)	2.0	(1.6-2.6)	2.2	(1.8, 2.8)
Other	3.4	(2.7,4.1)	3.0	(2.4-3.7)	3.4	(2.8,4.2)
Inotropic medication	3.1	(2.4,3.9)	3.0	(2.4-3.7)	3.2	(2.5,4.1)
Peripheral vascular disease	1.7	(1.4,2.1)	1.6	(1.3-2.0)	1.7	(1.4,2.0)
Body mass index (25+ vs. < 25 kg/m2)	0.8	(0.7,1.0)	0.9	(0.7-1.0)	0.8	(0.7,1.0)
Hospital-level
Academic affiliation (teaching vs. non-teaching)	1.2	(0.9,1.7)	1.2	(0.9-1.5)	1.3	(0.8,1.9)
Median of the annual number of cardiac surgeries 2001-2009, per 100 surgeries	0.88	(0.83,0.94)	0.93	(0.9-1.0)	0.91	(0.82,1.1)

*The estimated hospital-level variance, τ², was 0.04.

*The estimated hospital-level variance, τ², was 0.04