Table 1.
Descriptive characteristics of study participants with acute respiratory illness during four influenza seasons
| Characteristic | N (%) | Mean ± SD symptom severity score | P-value 1 |
|---|---|---|---|
| Age (years) |
|
|
|
| 18-49 |
1299 (54.7) |
12.7 ± 4.1 |
< 0.0001 |
| 50-64 |
676 (28.5) |
12.3 ± 4.0 |
|
| ≥ 65 |
399 (16.8) |
10.8 ± 4.2 |
|
| Gender (female) |
1591 (67.0) |
12.6 ± 4.1 |
< 0.0001 |
| Health insurance |
|
|
|
| Private only |
1200 (50.6) |
12.2 ± 3.8 |
0.56 |
| Public-assisted |
1082 (45.6) |
12.4 ± 4.4 |
|
| vNone |
92 (3.9) |
12.2 ± 4.5 |
|
| Study season |
|
|
|
| 2007-08 |
249 (10.5) |
13.0 ± 4.1 |
0.006 |
| 2008-09 |
672 (28.3) |
12.4 ± 4.4 |
|
| 2009-10 |
838 (35.3) |
12.0 ± 4.0 |
|
| 2010-11 |
615 (25.9) |
12.2 ± 4.0 |
|
| Days elapsed between symptom onset and date of enrollment |
|
|
|
| 0 |
67 (2.8) |
10.0 ± 4.1 |
< 0.0001 |
| 1-2 |
654 (27.6) |
12.3 ± 4.0 |
|
| 3-4 |
798 (33.6) |
12.5 ± 4.1 |
|
| 5-6 |
534 (22.5) |
12.2 ± 4.1 |
|
| ≥ 7 |
321 (13.5) |
12.1 ± 4.2 |
|
| Number of ambulatory care visits within the past 5 years |
|
|
|
| 0-20 |
334 (17.4) |
11.6 ± 4.0 |
0.009 |
| 21-40 |
603 (31.4) |
12.0 ± 4.0 |
|
| 41-60 |
474 (24.7) |
12.4 ± 4.1 |
|
| 61-80 |
313 (16.3) |
12.4 ± 4.3 |
|
| 81-100 |
195 (10.2) |
12.7 ± 4.1 |
|
| ≥ 101 |
|
|
|
| Influenza infection |
324 (13.7) |
13.9 ± 3.9 |
< 0.0001 |
| Presence of chronic disease |
|
|
|
| Pulmonary disease |
296 (12.5) |
12.4 ± 4.2 |
0.43 |
| Diabetes |
290 (12.2) |
12.1 ± 4.2 |
0.43 |
| Cardiovascular disease |
322 (13.6) |
11.8 ± 4.4 |
0.05 |
| Blood pressure (systolic/diastolic mmHg) |
|
|
|
| < 120/80 (healthy) |
724 (30.5) |
12.3 ± 3.9 |
0.59 |
| 120-139/80–89 (borderline) |
1159 (48.8) |
12.3 ± 4.2 |
|
| ≥ 140/90 (high) |
491 (20.7) |
12.1 ± 4.3 |
|
| Total cholesterol (mg/dL) |
|
|
|
| < 200 (healthy) |
1644 (69.3) |
12.1 ± 4.1 |
0.002 |
| 200-239 (borderline) |
566 (23.8) |
12.7 ± 4.2 |
|
| ≥ 240 (high) |
164 (6.9) |
12.7 ± 4.1 |
|
| Body mass index (kg/m2) |
|
|
|
| < 25 (healthy) |
465 (19.6) |
12.3 ± 3.9 |
0.01 |
| 25-29 (overweight) |
648 (27.3) |
12.3 ± 4.2 |
|
| ≥ 30 (obese) |
1261 (53.1) |
12.1 ± 4.3 |
|
| Smoking status |
|
|
|
| Never |
1259 (53.0) |
11.9 ± 3.9 |
< 0.0001 |
| Former |
719 (30.3) |
12.5 ± 4.3 |
|
| Current | 396 (16.7) | 12.9 ± 4.4 |
1P-value corresponds to t-test comparing symptom severity score between each characteristic category.