Background
Methods
Study design and data source
Definition of hospital volume
Statistical procedure
Results
Study population
Baseline clinical characteristics
Hospital volume | ||||
---|---|---|---|---|
Low (n = 149,182) | Medium (n = 149,507) | High (n = 149,129) | p value | |
Number of hospital | 648 | 190 | 107 | |
Number of patients in each hospital | 400 (276–504) | 810 (692–919) | 1405 (1158–1634) | |
Age (years) | 81 (72–87) | 81 (72–87) | 80 (71–86) | < 0.001 |
Age ≥ 85 years | 53,068 (35.6) | 51,603 (34.5) | 48,549 (32.6) | < 0.001 |
Male sex | 78,205 (52.4) | 79,548 (53.2) | 80,439 (53.9) | < 0.001 |
Body mass index (kg/m2) | 22.1 (19.6–25.0) | 22.2 (19.6–25.0) | 22.0 (19.5–24.8) | < 0.001 |
Hypertension | 96,539 (64.7) | 102,989 (68.9) | 101,547 (68.1) | < 0.001 |
Diabetes mellitus | 45,518 (30.5) | 48,361 (32.3) | 47,140 (31.6) | < 0.001 |
Chronic renal failure | 20,996 (14.1) | 22,222 (14.9) | 22,285 (14.9) | < 0.001 |
Chronic liver disease | 6086 (4.1) | 6185 (4.1) | 5246 (3.5) | < 0.001 |
Chronic respiratory disease | 17,282 (11.6) | 17,707 (11.8) | 15,752 (10.6) | < 0.001 |
Smoking | 43,317 (29.0) | 48,219 (32.3) | 52,262 (35.0) | < 0.001 |
Myocardial infarction | 3,699 (2.5) | 4,182 (2.8) | 4,636 (3.1) | < 0.001 |
Dilated cardiomyopathy | 10,853 (7.3) | 11,463 (7.7) | 11,810 (7.9) | < 0.001 |
Ventricular tachycardia/ventricular fibrillation | 5,751 (3.9) | 6,664 (4.5) | 7,874 (5.3) | < 0.001 |
Shock | 2,918 (2.0) | 3,167 (2.1) | 2,680 (1.8) | < 0.001 |
Anemia | 21,466 (14.4) | 24,775 (16.6) | 25,373 (17.0) | < 0.001 |
Barthel Index | 65 (15–100) | 65 (15–100) | 55 (5–100) | < 0.001 |
New York Heart Association | < 0.001 | |||
Class II | 46,002 (30.8) | 43,519 (29.1) | 40,294 (27.0) | |
Class III | 58,106 (38.9) | 57,366 (38.4) | 55,967 (37.5) | |
Class IV | 45,074 (30.2) | 48,622 (32.5) | 52,868 (35.5) | |
Medications within two days after admission | ||||
Beta blocker | 44,322 (29.7) | 48,517 (32.5) | 55,547 (37.2) | < 0.001 |
Renin-angiotensin system inhibitor | 50,814 (34.1) | 53,377 (35.7) | 62,167 (41.7) | < 0.001 |
Angiotensin converting enzyme inhibitor | 21,565 (14.5) | 23,160 (15.5) | 26,987 (18.1) | < 0.001 |
Angiotensin II receptor blocker | 30,206 (20.2) | 31,180 (20.9) | 36,480 (24.5) | < 0.001 |
Mineralocorticoid receptor antagonist | 44,609 (29.9) | 47,290 (31.6) | 53,716 (36.0) | < 0.001 |
Intravenous inotropic agent | 24,788 (16.6) | 25,138 (16.8) | 28,310 (19.0) | < 0.001 |
Intravenous nitrate | 26,825 (18.0) | 31,741 (21.2) | 34,999 (23.5) | < 0.001 |
Intravenous furosemide | 97,917 (65.6) | 101,240 (67.7) | 105,515 (70.8) | < 0.001 |
Procedures during hospitalization
Hospital volume | ||||
---|---|---|---|---|
Low (n = 149,182) | Medium (n = 149,507) | High (n = 149,129) | p value | |
Respiratory support | 19,689 (13.2) | 23,151 (15.5) | 27,814 (18.7) | < 0.001 |
Hemodialysis | 3594 (2.4) | 3909 (2.6) | 3882 (2.6) | < 0.001 |
Intra-aortic balloon pumping | 916 (0.6) | 1073 (0.7) | 1186 (0.8) | < 0.001 |
Extra-corporeal membrane oxygenation | 132 (0.1) | 160 (0.1) | 158 (0.1) | 0.200 |
Cost (JPY) | 712,555 (474,773–1,144,035) | 743,775 (504,863–1,165,348) | 755,800 (519,243–1,181,185) | < 0.001 |
Cost (USD) | 6556 (4368–10,525) | 6843 (4645–10,721) | 6953 (4777–10,867) | < 0.001 |
Length of hospital stay (days) | 18 (11–29) | 17 (11–28) | 16 (11–25) | < 0.001 |
In-hospital death | 11,068 (7.4) | 10,067 (6.7) | 9687 (6.5) | < 0.001 |
Impact of hospital volume on in-hospital mortality
Univariate logistic regression analysis | Multivariable logistic regression fitted with generalized estimating equation | |||||
---|---|---|---|---|---|---|
Odds ratio | 95% Confidence interval | p value | Odds ratio | 95% Confidence interval | p value | |
Hospital volume | ||||||
Low | Reference | Reference | ||||
Medium | 0.90 | 0.88–0.93 | < 0.001 | 0.91 | 0.83–0.99 | 0.035 |
High | 0.87 | 0.84–0.89 | < 0.001 | 0.86 | 0.78–0.95 | 0.004 |
Age (years) | 1.05 | 1.05–1.06 | < 0.001 | 1.04 | 1.04–1.04 | < 0.001 |
Sex | ||||||
Female | Reference | Reference | ||||
Male | 0.86 | 0.84–0.88 | < 0.001 | 1.27 | 1.23–1.32 | < 0.001 |
Body mass index (kg/m2) | 0.90 | 0.90–0.90 | < 0.001 | 0.95 | 0.95–0.96 | < 0.001 |
Hypertension | 0.43 | 0.42–0.44 | < 0.001 | 0.53 | 0.50–0.55 | < 0.001 |
Diabetes mellitus | 0.78 | 0.76–0.80 | < 0.001 | 1.03 | 0.99–1.06 | 0.120 |
Chronic renal failure | 1.71 | 1.66–1.75 | < 0.001 | 1.57 | 1.51–1.63 | < 0.001 |
Chronic liver disease | 1.33 | 1.26–1.40 | < 0.001 | 1.45 | 1.36–1.55 | < 0.001 |
Chronic respiratory disease | 1.01 | 0.98–1.05 | 0.568 | 0.98 | 0.94–1.03 | 0.473 |
Myocardial infarction | 1.93 | 1.83–2.04 | < 0.001 | 1.46 | 1.35–1.57 | < 0.001 |
Dilated cardiomyopathy | 0.87 | 0.83–0.91 | < 0.001 | 1.19 | 1.13–1.26 | < 0.001 |
Smoking | 0.68 | 0.66–0.69 | < 0.001 | 0.88 | 0.85–0.92 | < 0.001 |
New York Heart Association | ||||||
Class II | Reference | Reference | ||||
Class III | 1.92 | 1.85–1.99 | < 0.001 | 1.68 | 1.58–1.79 | < 0.001 |
Class IV | 4.49 | 4.33–4.66 | < 0.001 | 3.36 | 3.11–3.63 | < 0.001 |
Ventricular tachycardia/ventricular fibrillation | 1.77 | 1.69–1.85 | < 0.001 | 1.97 | 1.83–2.11 | < 0.001 |
Shock | 5.76 | 5.49–6.04 | < 0.001 | 3.20 | 2.85–3.60 | < 0.001 |
Anemia | 1.55 | 1.50–1.59 | < 0.001 | 1.35 | 1.30–1.41 | < 0.001 |
Barthel Index per 10 | 0.84 | 0.83–0.84 | < 0.001 | 0.89 | 0.89–0.90 | < 0.001 |
Administration within two days | ||||||
Beta blocker | 0.61 | 0.59–0.63 | < 0.001 | 0.94 | 0.90–0.97 | < 0.001 |
Renin-angiotensin system inhibitor | 0.41 | 0.40–0.42 | < 0.001 | 0.62 | 0.60–0.65 | < 0.001 |
Mineralocorticoid receptor antagonist | 0.63 | 0.61–0.65 | < 0.001 | 0.83 | 0.80–0.86 | < 0.001 |
Intravenous inotropic agent | 2.88 | 2.81–2.95 | < 0.001 | 2.13 | 2.04–2.23 | < 0.001 |
Intravenous nitrate | 0.64 | 0.62–0.66 | < 0.001 | 0.57 | 0.54–0.60 | < 0.001 |
Intravenous furosemide | 1.32 | 1.29–1.36 | < 0.001 | 0.97 | 0.94–1.01 | 0.172 |