Hospital differences in mortality rates after hip fracture surgery in Denmark

Figures & data

Figure 1 Flowchart patient inclusion.

Table 1 Characteristic of the hip fracture population

Overall 30-day mortality	10%
Number of patients in the population	60,004
Number of hospitals	32
Median number of patients at the hospital (min–max)	143–4,193
Age group (years)
65–74 (reference)	19%	11,631
75–84	38%	22,554
>85	43%	25,819
Gender
Men	29%	17,158
Women (reference)	71%	42,846
BMI (kg/m^2)
<19: Underweight	13%	7,503
20–25: Normal (reference)	48%	28,796
>26: Overweight	22%	13,352
Missing	17%	10,353
CCI
0 point: No comorbidity (reference)	18%	10,890
1 point: Low comorbidity	23%	13,826
2 points: Moderate comorbidity	20%	12,246
+3 points: High comorbidity	38%	23,042
Fracture type
Undisplaced femoral neck (reference)	39%	23,508
Displaced femoral neck	8%	4,582
Unspecified femoral neck	6%	3,712
Pertrochanteric	40%	23,802
Subtrochanteric	7%	4,400
Education
Ground school (reference)	49%	29,326
More than ground school	25%	15,032
University degree	9%	5,313
Missing	17%	10,333
Family mean income
Low (reference)	33%	19,905
Medium	33%	20,010
High	34%	20,089
Migration status
Immigrant	3%	1,783
Native (reference)	97%	58,221
Cohabiting status
Living alone (reference)	63%	37,936
Living together	37%	22,068
Employment status
Retired (reference)	90%	53,946
Employed	2%	1,436
Missing	8%	4,622
Fragility
Nursing home residence	14%	8,554
Living in own home (reference)	86%	51,450

Abbreviations: BMI, body mass index; CCI, Charlson comorbidity index.

Table 2 Variation in 30-day mortality

	Simple logistic regression analysis				Multilevel logistic regression analysis
	Model 1		Model 2		Model 3
Specific individual average effects
Sociodemographic score
Low	1.00		1.00		1.00
Medium	1.73	(1.56–1.92)	1.60	(1.44–1.78)	1.60	(1.44–1.78)
High	3.11	(2.82–3.43)	2.70	(2.44–2.98)	2.69	(2.44–2.97)
Very high	5.80	(5.29–6.36)	5.07	(4.62–5.58)	5.10	(4.64–5.61)
BMI^a (kg/m^2)
<19: Underweight			1.59	(1.46–1.72)	1.60	(1.54–1.82)
20–25: Normal (ref.)			1.00		1.00
>26: Overweight			0.68	(0.63–0.74)	0.69	(0.63–0.74)
Missing			1.88	(1.76–2.02)	2.03	(1.88–2.18)
CCI^b
0 point: No comorbidity (ref.)			1.00		1.00
1 point: Low comorbidity			1.29	(1.17–1.42)	1.30	(1.18–1.43)
2 points: Moderate comorbidity			1.32	(1.20–1.45)	1.34	(1.21–1.47)
+3 points: High comorbidity			1.63	(1.50–1.78)	1.65	(1.51–1.80)
Fracture type
Undisplaced femoral neck (reference)			1.00		1.00
Displaced femoral neck			0.76	(0.67–0.86)	0.77	(0.68–0.87)
Unspecified femoral neck			0.99	(0.88–1.11)	0.98	(0.87–1.10)
Pertrochanteric			1.04	(0.98–1.10)	1.04	(0.98–1.11)
Subtrochanteric			1.22	(1.09–1.35)	1.23	(1.10–1.37)
Frailty
Nursing home residence vs living in own home			2.28	(2.14–2.43)	2.29	(2.15–2.44)
General contextual effects
Hospital variance					0.0290	(0.0151–0.0559)
VPC^c/ICC^d hospital (%)					0.87	(0.46–1.67)
MOR hospital					1.18	(1.12–1.25)
AUC	0.671	(0.665–0.678)	0.728	(0.721–0.734)	0.732	(0.725–0.738)
$AU{C}_{\mathrm{\Delta }2-1}($ increment (model 2–mode 1)	Reference		0.057
$AU{C}_{\mathrm{\Delta }3-2}$ (increment model 3–mode 2)			Reference		0.004

Notes: ^aModel 1: Simple logistic regression model adjusted for socioeconomic risk score. ^bModel 2: Simple logistic regression model adjusted for socioeconomic risk score and biomedical characteristics of the patient. ^cModel 3: Multilevel logistic regression model. ^dModel 4: Multilevel logistic regression model adjusted for socioeconomic risk score and biomedical characteristics of the patient and hospital as random effect.

Abbreviations: BMI, body mass index; CCI, Charlson comorbidity index; VPC, variance partition Coefficient; ICC, intra class correlation coefficient, MOR, median odds ratio, AUC, area under the receiver operating characteristic curve.

Figure 2 League table ranking the 32 hospitals according to their unadjusted absolute risk of 30-day mortality with 95 % confidence intervals obtained from a multilevel model.

Figure 3 League table ranking the 32 hospitals according to their adjusted absolute risk of 30-day mortality with 95 % confidence intervals obtained from a multilevel model adjusted by patient-mix.