Table 1.
Baseline Characteristics of the Study Population Before and After PSM Analysis
| Characteristics | Before PSM (N=6655) | After PSM (N=5156) | |||||
|---|---|---|---|---|---|---|---|
| Non‐CAC (N=2616) | CAC (N=4039) | P Value | Non‐CAC (N=2578) | CAC (N=2578) | P Value | SMDa | |
| Age, mean (SD), yb | 69.0 (17.1) | 67.4 (17.3) | <0.001c | 69.3 (17.0) | 69.4 (16.9) | 0.83 | −0.006 |
| <40 | 150 (5.7) | 255 (6.3) | 0.008 | 142 (5.5) | 130 (5.0) | 0.74 | 0.02 |
| 40–49 | 228 (8.7) | 423 (10.5) | 211 (8.2) | 221 (8.6) | −0.01 | ||
| 50–59 | 364 (13.9) | 629 (15.6) | 356 (13.8) | 375 (14.5) | −0.02 | ||
| 60–69 | 454 (17.4) | 723 (17.9) | 449 (17.4) | 436 (16.9) | 0.01 | ||
| 70–79 | 509 (19.5) | 730 (18.1) | 507 (19.7) | 477 (18.5) | 0.03 | ||
| ≥80 | 911 (34.8) | 1279 (31.7) | 913 (35.4) | 939 (36.4) | −0.02 | ||
| Sexb | |||||||
| Women | 819 (31.3) | 1195 (29.6) | 0.14 | 821 (31.8) | 796 (30.9) | 0.45 | 0.02 |
| Men | 1797 (68.7) | 2844 (70.4) | 1757 (68.2) | 1782 (69.1) | −0.02 | ||
| Location of arrestb | |||||||
| Public | 492 (18.8) | 775 (19.2) | 0.70 | 491 (19.0) | 465 (18.0) | 0.35 | 0.03 |
| Residential | 2124 (81.2) | 3264 (80.8) | 2087 (81.0) | 2113 (82.0) | −0.03 | ||
| Witnessed arrestb | |||||||
| Yes | 1092 (41.7) | 1799 (44.5) | 0.03c | 1099 (42.6) | 1105 (42.9) | 0.50 | −0.006 |
| No | 1524 (58.3) | 2240 (55.5) | 1479 (57.4) | 1473 (57.1) | 0.006 | ||
| Bystander CPRb | |||||||
| Yes | 752 (28.7) | 1299 (32.2) | 0.003c | 759 (29.4) | 737 (28.6) | 0.52 | 0.02 |
| No | 1864 (71.3) | 2740 (67.8) | 1819 (70.6) | 1841 (71.4) | −0.02 | ||
| No. of EMTsb | |||||||
| 2 | 1562 (59.7) | 2385 (59.0) | 0.53 | 1570 (60.9) | 1604 (62.2) | 0.62 | −0.03 |
| 3–4 | 1011 (38.6) | 1573 (38.9) | 971 (37.7) | 937 (36.3) | 0.03 | ||
| 5–6 | 43 (1.6) | 81 (2.0) | 37 (1.4) | 37 (1.4) | 0.00 | ||
| EMT certification levelb | |||||||
| Intermediate | 1422 (54.4) | 2194 (54.3) | 0.98 | 1414 (54.8) | 1465 (56.8) | 0.15 | −0.04 |
| Paramedic | 1194 (45.6) | 1845 (45.7) | 1164 (45.2) | 1113 (43.2) | 0.04 | ||
| Type of life supportb | |||||||
| BLS | 1457 (55.7) | 2275 (56.3) | 0.61 | 1448 (56.2) | 1498 (58.1) | 0.16 | −0.04 |
| ALS | 1159 (44.3) | 1764 (43.7) | 1130 (43.8) | 1080 (41.9) | 0.04 | ||
| Prehospital ROSCb | |||||||
| Yes | 112 (4.3) | 224 (5.5) | 0.02c | 117 (4.5) | 116 (4.5) | 0.95 | 0.002 |
| No | 2504 (95.7) | 3815 (94.5) | 2461 (95.5) | 2462 (95.5) | −0.002 | ||
| AEDb | |||||||
| Shockable rhythm | 561 (21.4) | 1044 (25.8) | <0.001c | 523 (20.3) | 533 (20.6) | 0.54 | −0.007 |
| Nonshockable rhythm | 2055 (78.6) | 2995 (74.2) | 2055 (79.7) | 2045 (79.4) | 0.007 | ||
| EMS parameter | |||||||
| Response time, median (IQR), min | 7 (5–9) | 7 (5–9) | 0.01c | 7 (5–9) | 7 (6–9) | 0.006 | |
| Scene time interval, median (IQR), min | 11 (9–14) | 12 (9–15) | 0.01c | 11 (9–14) | 11 (9–14) | 0.01 | |
| Transport time, median (IQR), min | 5 (3–7) | 5 (3–8) | <0.001c | 5 (3–7) | 5 (3–7) | <0.001c | |
| Transport distance, mean (SD), km | 5.3 (2.8) | 6.3 (5.7) | <0.001c | 5.9 (4.1) | 6.1 (5.3) | 0.47 | |
| CPC | |||||||
| 1 | 46 (1.8) | 129 (3.2) | <0.001c | 46 (1.8) | 59 (2.3) | 0.002c | |
| 2 | 21 (0.8) | 68 (1.7) | 19 (0.7) | 35 (1.4) | |||
| 3 | 22 (0.8) | 75 (1.9) | 21 (0.8) | 41 (1.6) | |||
| 4 | 41 (1.6) | 107 (2.6) | 40 (1.6) | 57 (2.2) | |||
| 5 | 2486 (95.0) | 3660 (90.6) | 2452 (95.1) | 2386 (92.6) | |||
Values are expressed as number (percentage) unless otherwise specified. AED indicates automated external defibrillator; ALS, advanced life support; BLS, basic life support; CAC, cardiac arrest center; CPC, Cerebral Performance Category; CPR, cardiopulmonary resuscitation; EMS, emergency medical service; EMT, emergency medical technician; IQR, interquartile range (25%–75%); PSM, propensity score matching; ROSC, return of spontaneous circulation; and SMD, standardized mean difference.
a
For assessing balance after matching.
b
Propensity score adjusted variable.
c
P<0.05.