Table 1:
Baseline patient characteristics, and comparison of patients admitted to hospital with nonsevere and severe influenza with patients in the control group
| Characteristic | No. (%) of patients with nonsevere influenza* n = 598 |
No. (%) of patients in the control group* n = 1493 |
p value† (patients with nonsevere influenza v. controls) | No. (%) of patients with severe influenza* n = 130 |
No. (%) of patients in the control group* n = 333 |
p value† (patients with severe influenza v. controls) | p value‡ (patients with severe v. those with nonsevere influenza) |
|---|---|---|---|---|---|---|---|
| Influenza season | 0.3 | 0.5 | 0.9 | ||||
| 2013/14 | 355 (59.4) | 849 (56.9) | 78 (60.0) | 189 (56.8) | |||
| 2014/15 | 243 (40.6) | 644 (43.1) | 52 (40.0) | 144 (43.2) | |||
| Sex | 0.6 | 0.8 | 0.6 | ||||
| Female | 279 (46.7) | 716 (48.0) | 64 (49.2) | 168 (50.5) | |||
| Male | 319 (53.3) | 777 (52.0) | 66 (50.8) | 165 (49.5) | |||
| Age, yr | 0.7 | 0.9 | 0.6 | ||||
| 65–79 | 340 (56.9) | 837 (56.1) | 71 (54.6) | 179 (53.8) | |||
| ≥ 80 | 258 (43.1) | 656 (43.9) | 59 (45.4) | 154 (46.2) | |||
| No. of major chronic conditions§ | 0.2 | 0.1 | 0.07 | ||||
| 0 | 76 (12.7) | 238 (15.9) | 14 (10.8) | 58 (17.4) | |||
| 1 | 197 (32.9) | 472 (31.6) | 31 (23.8) | 84 (25.2) | |||
| > 1 | 325 (54.3) | 783 (52.4) | 85 (65.4) | 191 (57.4) | |||
| Pulmonary disease | 262 (43.8) | 362 (24.2) | < 0.001 | 55 (42.3) | 91 (27.3) | 0.002 | 0.8 |
| Diabetes | 187 (31.3) | 542 (36.3) | 0.03 | 48 (36.9) | 124 (37.2) | 1 | 0.2 |
| Cardiovascular disease | 162 (27.1) | 498 (33.4) | 0.005 | 62 (47.7) | 153 (45.9) | 0.7 | < 0.001 |
| Pneumonia in the previous 2 yr | 72 (12.0) | 82 (5.5) | < 0.001 | 19 (14.6) | 22 (6.6) | 0.006 | 0.4 |
| Corticosteroid treatment in the previous month | 33 (5.5) | 35 (2.3) | < 0.001 | 11 (8.5) | 8 (2.4) | 0.003 | 0.2 |
| Barthel Index score < 40 | 50 (8.4) | 153 (10.2) | 0.2 | 16 (12.3) | 32 (9.6) | 0.4 | 0.2 |
| Smoking | 0.2 | 0.1 | 0.8 | ||||
| Never smoked | 316 (52.8) | 851 (57.0) | 67 (51.5) | 206 (61.9) | |||
| Previously smoked | 234 (39.1) | 534 (35.8) | 54 (41.5) | 105 (31.5) | |||
| Currently smokes | 48 (8.0) | 108 (7.2) | 9 (6.9) | 22 (6.6) | |||
| No. of visits to primary care in the previous yr | 0.2 | 0.3 | 0.006 | ||||
| 0–2 | 176 (29.7) | 499 (33.6) | 54 (42.9) | 115 (35.1) | |||
| 3–10 | 270 (45.5) | 642 (43.2) | 53 (42.1) | 154 (47.0) | |||
| > 10 | 147 (24.8) | 346 (23.3) | 19 (15.1) | 59 (18.0) | |||
| Visited hospital in previous year | 411 (69.2) | 1094 (73.7) | 0.04 | 94 (75.2) | 235 (71.9) | 0.5 | 0.2 |
| Admission to hospital ≥ 7 d within onset | 133 (22.2) | NA | 20 (15.4) | NA | 0.08 | ||
| Length of hospital stay, mean ± SD; d | 10 ± 9 | 13 ± 11 | < 0.001 | 17 ± 14 | 14 ± 12 | 0.02 | < 0.001 |
| Antiviral treatment | 521 (88.9) | NA | 119 (92.2) | NA | 0.3 | ||
| Pneumococcal vaccination | |||||||
| 23-Valent polysaccharide vaccine | 117 (19.6) | 221 (14.8) | 0.008 | 18 (13.8) | 56 (16.8) | 0.4 | 0.1 |
| 13-Valent conjugate vaccine | 12 (2.0) | 11 (0.7) | 0.01 | 1 (0.8) | 2 (0.6) | 1 | 0.3 |
| Current season influenza vaccination | 312 (52.2) | 862 (57.7) | 0.02 | 47 (36.2) | 191 (57.4) | < 0.001 | 0.001 |
| Prior season influenza vaccination | |||||||
| Current season - 1 | 329 (55.0) | 872 (58.4) | 0.2 | 47 (36.2) | 182 (54.7) | < 0.001 | < 0.001 |
| Current season - 2 | 327 (54.7) | 846 (56.7) | 0.4 | 51 (39.2) | 186 (55.9) | 0.001 | 0.001 |
| Current season - 3 | 324 (54.2) | 823 (55.1) | 0.7 | 48 (36.9) | 171 (51.4) | 0.005 | < 0.001 |
Note: NA = not applicable, SD = standard deviation.
Unless stated otherwise.
Comparison of patients with influenza and controls (patients admitted to hospital) using the χ2 test, Fisher exact test or t test.
Comparison of patients with severe and nonsevere influenza using the χ2 test, Fisher exact test or t test.
Chronic diseases that were present at baseline, including pulmonary disease, renal disease, diabetes, immunocompromising conditions, neurologic disease, cancer, chronic liver disease, body mass index ≥ 40 kg/m2, cardiovascular disease, neuromuscular disease, cognitive dysfunction and rheumatologic disease.