Table 1. Characteristics of patients across hospitalizations.
| Variables | Overall (n=11,155) | Silent period (n=5375) | Season-matched alert period (n=5780) | Missing, n (%) | P value | |
|---|---|---|---|---|---|---|
| Age (years), median (IQR) | 67.0 (55.0-77.0) | 67.0 (55.0-77.0) | 67.0 (55.0-77.0) | 0 (0) | .90 | |
| Sex, n (%) | .19 | |||||
|
Female |
5632 (50.5) | 2679 (49.8) | 2953 (51.1) | 0 (0) | ||
| Male | 5523 (49.5) | 2696 (50.2) | 2827 (48.9) | 0 (0) | ||
| BMI (kg/m2), mean (SD) | 24.3 (4.1) | 24.3 (4.0) | 24.3 (4.2) | 1787 (16.02) | .58 | |
| Vital signs | ||||||
| Diastolic blood pressure (mm Hg), mean (SD) | 76.7 (12.1) | 76.9 (12.0) | 76.6 (12.2) | 4 (0.04) | .27 | |
| Pulse (beats per min), mean (SD) | 79.4 (14.7) | 79.1 (14.7) | 79.8 (14.7) | 4 (0.04) | .01 | |
| Respiratory rate (breaths per min), median (IQR) | 20.0 (18.0-20.0) | 20.0 (19.0-20.0) | 20.0 (18.0-20.0) | 4 (0.04) | <.001 | |
| Systolic blood pressure (mm Hg), mean (SD) | 127.4 (20.1) | 127.7 (20.4) | 127.1 (19.9) | 4 (0.04) | .13 | |
| SpO2 (%), median (IQR) | 97.0 (96.0-98.0) | 97.0 (96.0-98.0) | 97.0 (96.0-98.0) | 2634 (23.61) | .03 | |
| Temperature (°C), mean (SD) | 36.8 (0.4) | 36.8 (0.4) | 36.8 (0.4) | 6 (0.05) | .18 | |
| Laboratory values | ||||||
| Bilirubin (mg/dL), median (IQR) | 0.5 (0.4-0.8) | 0.5 (0.4-0.8) | 0.5 (0.4-0.8) | 2928 (26.25) | <.001 | |
| Creatinine (mg/dL), median (IQR) | 0.8 (0.6-1.0) | 0.8 (0.6-1.0) | 0.8 (0.6-1.0) | 2362 (21.17) | .15 | |
| C-reactive protein (mg/dL), median (IQR) | 0.7 (0.1-3.9) | 0.6 (0.1-3.7) | 0.7 (0.1-4.2) | 3605 (32.32) | .24 | |
| HCO3 (mmol/L), mean (SD) | 24.4 (5.7) | 24.6 (5.5) | 24.3 (5.8) | 9437 (84.60) | .21 | |
| Hematocrit (%), mean (SD) | 35.7 (6.0) | 35.6 (6.1) | 35.7 (6.0) | 1719 (15.41) | .21 | |
| Lactate (mmol/L), median (IQR) | 2.0 (1.2-4.3) | 2.2 (1.3-4.0) | 1.9 (1.1-4.3) | 10,890 (97.62) | .51 | |
| PCO2 (mm Hg), mean (SD) | 38.3 (10.2) | 38.4 (10.0) | 38.2 (10.3) | 9437 (84.60) | .69 | |
| pH, mean (SD) | 7.4 (0.1) | 7.4 (0.1) | 7.4 (0.1) | 9437 (84.60) | .17 | |
| Platelets (103/µL), mean (SD) | 218.9 (80.6) | 218.7 (81.5) | 219.0 (79.7) | 1719 (15.41) | .87 | |
| PO2 (mm Hg), median (IQR) | 92.0 (78.0-113.0) | 91.0 (78.0-114.0) | 93.0 (78.0-112.0) | 9437 (84.60) | .85 | |
| Potassium (mEq/L), mean (SD) | 4.1 (0.6) | 4.0 (0.6) | 4.1 (0.6) | 2732 (24.49) | .01 | |
| Sodium (mEq/L), median (IQR) | 141.0 (138.0-142.0) | 141.0 (139.0-142.0) | 140.0 (138.0-142.0) | 2728 (24.46) | .001 | |
| White blood cell count (103/µL), median (IQR) | 7.0 (5.5-9.2) | 6.9 (5.5-9.2) | 7.0 (5.5-9.3) | 1719 (15.41) | .41 | |
| Baseline scores, median (IQR) | ||||||
| NEWSa | 3.0 (3.0-4.0) | 3.0 (3.0-4.0) | 4.0 (3.0-5.0) | 549 (4.92) | <.001 | |
| MEWSb | 1.0 (1.0-1.0) | 1.0 (1.0-1.0) | 1.0 (1.0-1.0) | 549 (4.92) | .05 | |
| APACHE IIc | 13.0 (9.0-18.0) | 13.0 (9.0-18.0) | 13.0 (10.0-18.0) | 9911 (88.85) | .23 | |
| CCId (comorbidity) | 3.0 (2.0-5.0) | 3.0 (2.0-5.0) | 3.0 (2.0-5.0) | 0 (0) | .58 | |
a
NEWS: National Early Warning Score
b
MEWS: Modified Early Warning Score
c
APACHE II: Acute Physiology and Chronic Health Evaluation II
d
CCI: Charlson Comorbidity Index