Table 1.
Baseline characteristics stratified by age groups
| Age groups | ||||
|---|---|---|---|---|
| ≤79 years (n = 54 080) | 80–89 years (n = 27 740) | ≥90 years (n = 2320) | P | |
| Demographic characteristics | ||||
| Age | 72 (68–76) | 83 (81–85) | 92 (90–94) | <0.01 |
| Biological sex | ||||
| Male | 32 410 (59.9) | 15 425 (55.6) | 1260 (54.4) | <0.01 |
| Female | 21 670 (40.1) | 12 315 (44.4) | 1055 (45.6) | |
| Race/ethnicity | ||||
| White | 45 100 (86.2) | 24 135 (89.8) | 2050 (91.3) | <0.01 |
| Black | 2905 (5.6) | 660 (2.5) | 40 (1.8) | |
| Hispanic | 2485 (4.7) | 1220 (4.5) | 105 (4.7) | |
| Other | 1840 (3.5) | 865 (3.2) | 50 (2.2) | |
| Insurance | ||||
| Medicare | 45 655 (86.2) | 26 330 (95.8) | 2195 (94.7) | <0.01 |
| Medicaid | 1005 (1.9) | 90 (0.3) | <11 (<0.5)a | |
| Private insurance | 6060 (11.4) | 965 (3.6) | 105 (4.5) | |
| Self-pay | 245 (0.5) | 95 (0.3) | <11 (<0.5)a | |
| Income quartileb | ||||
| I | 12 410 (23.3) | 5440 (19.8) | 315 (13.8) | <0.01 |
| II | 14 335 (26.9) | 7145 (26.0) | 615 (27.0) | |
| III | 14 475 (27.2) | 7720 (28.1) | 595 (26.2) | |
| IV | 12 040 (22.6) | 7135 (26.1) | 750 (33.0) | |
| Hospital characteristics | ||||
| Location/teaching status | ||||
| Rural | 1355 (2.5) | 500 (1.8) | 35 (1.5) | 0.01 |
| Urban non-teaching | 5525 (10.2) | 2750 (9.9) | 300 (12.9) | |
| Urban teaching | 47 200 (87.3) | 24 490 (88.3) | 1985 (85.6) | |
| Bed sizec | ||||
| Small | 5535 (10.2) | 3120 (11.2) | 240 (10.3) | 0.12 |
| Medium | 12 600 (23.3) | 6790 (24.5) | 560 (24.2) | |
| Large | 35 945 (66.5) | 17 830 (64.3) | 1520 (65.5) | |
| Region | ||||
| Northeast | 8530 (15.8) | 4660 (16.8) | 465 (20.0) | <0.01 |
| Midwest | 12 570 (23.2) | 5975 (21.5) | 495 (21.3) | |
| South | 22 125 (40.9) | 10 585 (38.2) | 735 (31.7) | |
| West | 10 855 (20.1) | 6520 (23.5) | 625 (27.0) | |
| Elective admission | 49 715 (92.1) | 25 620 (92.5) | 2110 (91.1) | 0.50 |
| Weekend admission | 455 (0.8) | 250 (0.9) | 25 (1.1) | 0.78 |
| Clinical characteristics | ||||
| Elixhauser comorbidity index | 4 (3–6) | 4 (3–5) | 4 (3–5) | <0.01 |
| Charlson comorbidity index | 2 (1–4) | 2 (1–3) | 2 (1–3) | <0.01 |
| 0 | 11 175 (20.7) | 6080 (21.9) | 575 (24.7) | 0.06 |
| 1 | 13 040 (24.0) | 6655 (24.0) | 550 (23.7) | |
| 2 | 10 315 (19.1) | 5530 (19.9) | 405 (17.5) | |
| ≥3 | 19 550 (36.2) | 9475 (34.2) | 790 (34.1) | |
| Diabetes mellitus | 21 400 (39.6) | 8145 (29.4) | 400 (17.2) | <0.01 |
| Hypertension | 47 230 (87.3) | 24 005 (86.5) | 1975 (85.1) | 0.16 |
| Dyslipidaemia | 33 685 (62.3) | 17 410 (62.8) | 1455 (62.7) | 0.83 |
| Nicotine/tobacco use | 21 835 (40.4) | 10 115 (36.5) | 730 (31.5) | <0.01 |
| Alcohol abuse | 1055 (2.0) | 165 (0.6) | 15 (0.6) | <0.01 |
| Drug abuse | 245 (0.5) | 45 (0.2) | <11 (<0.5)a | <0.01 |
| Obesity | 11 875 (22.0) | 2955 (10.7) | 75 (3.2) | <0.01 |
| Coronary artery disease | 26 160 (48.4) | 14 410 (51.9) | 1120 (48.3) | <0.01 |
| Peripheral vascular disease | 8580 (15.9) | 4660 (16.8) | 335 (14.4) | 0.19 |
| Congestive heart failure | 21 385 (39.5) | 11 135 (40.1) | 1105 (47.6) | <0.01 |
| Renal failure | 12 660 (23.4) | 7015 (25.3) | 735 (31.7) | <0.01 |
| Dialysis dependent | 1940 (3.6) | 385 (1.4) | 15 (0.6) | <0.01 |
| Liver disease | 1945 (3.6) | 400 (1.4) | <11 (<0.5)a | <0.01 |
| Chronic pulmonary disease | 12 815 (23.7) | 5715 (20.6) | 350 (15.1) | <0.01 |
| Obstructive sleep apnoea | 11 710 (21.7) | 3565 (12.9) | 145 (6.3) | <0.01 |
| Coagulopathy | 2265 (4.2) | 1055 (3.8) | 120 (5.2) | 0.25 |
| Cancer | 1150 (2.1) | 665 (2.4) | 55 (2.4) | 0.52 |
| Malnutrition | 85 (0.2) | 50 (0.2) | <11 (<0.5)a | 0.37 |
| Dementia | 970 (1.8) | 1300 (4.7) | 100 (4.3) | <0.01 |
| Depression | 4955 (9.2) | 1750 (6.3) | 105 (4.5) | <0.01 |
| Previous history | ||||
| Myocardial infarction | 7420 (13.7) | 3380 (12.2) | 235 (10.1) | <0.01 |
| Stroke/TIA | 12 250 (22.7) | 6830 (24.6) | 545 (23.5) | 0.01 |
| Cardiac arrest | 360 (0.7) | 100 (0.4) | <11 (<0.5)a | 0.01 |
| PCI | 9110 (16.8) | 4795 (17.3) | 450 (19.4) | 0.32 |
| CABG | 6980 (12.9) | 4290 (15.5) | 315 (13.6) | <0.01 |
| ICD | 3775 (7.0) | 1660 (6.0) | 105 (4.5) | <0.01 |
| PPM | 7735 (14.3) | 6510 (23.5) | 710 (30.6) | <0.01 |
Data are presented as median (IQR) or n (%). Two authors (M.I. and H.A.) independently verified the International Classification of Diseases, Tenth Revision (ICD-10), codes that corresponded to each comorbidity (see Supplementary material online, Table S1), and any disagreements in inclusion or exclusion of ICD-10 codes were discussed with a third author (M.A).
CABG, coronary artery bypass grafting; ICD, implantable cardioverter-defibrillator; IQR, interquartile range; PCI, percutaneous coronary intervention; PPM, permanent pacemaker; TIA, transient ischaemic attack.
aCell counts < 11 are not reportable per HCUP guidelines.
bEstimated median household incomes are ZIP code-specific, updated annually, and classified into four quartiles indicating the poorest to wealthiest populations.
cBed size categories are based on inpatient beds and are specific to the hospital’s location and teaching status. A more detailed explanation of all the variables in the NIS, including the specific dollar amounts in each category of median household income and the number of hospital beds in each category, is available online (https://www.hcup-us.ahrq.gov/db/nation/nis/nisdde.jsp).