Volume 17, Number 8—August 2011
Research
Case–Control Study of Risk Factors for Hospitalization Caused by Pandemic (H1N1) 2009
Kate A. Ward, Paula J. Spokes
, and Jeremy M. McAnulty
, and Jeremy M. McAnultyTable A1
Comparison of characteristics for case-patients and controls in a study of risk for hospitalization because of pandemic (H1N1) 2009 influenza, Sydney, Australia, 2009*
| Variable |
No. (%) case-patients, n = 302 |
No. (%) controls, n = 603 |
||
| OR (95% CI) |
p value |
|||
| Sex | ||||
| F | 177 (59) | 396 (66) | Referent | |
| M |
125 (41) |
207 (34) |
1.4 (1.0–1.8) |
0.0379 |
| Age, y | ||||
| 16–25 | 40 (13) | 61 (10) | 2.4 (1.4–4.1) | |
| 26–35 | 54 (18) | 92 (15) | 2.1 (1.3–3.5) | |
| 36–45 | 58 (19) | 111 (18) | 1.9 (1.2–3.1) | |
| 46–55 | 72 (24) | 111 (18) | 2.3 (1.4–3.8) | |
| 56–65 | 44 (15) | 105 (17) | 1.5 (0.9–2.5) | |
| >65 |
34 (11) |
123 (20) |
Referent |
0.007 |
| Area of residence in Sydney | ||||
| South East | 34 (11) | 71 (12) | ||
| West | 112 (37) | 229 (38) | ||
| South West | 123 (41) | 239 (40) | ||
| North |
33 (11) |
64 (11) |
||
| Aboriginal status | ||||
| Nonindigenous | 293 (97) | 596 (99) | Referent | |
| Indigenous |
9 (3) |
7 (1) |
2.6 (1–7.1) |
0.0591 |
| Body mass index† | ||||
| Underweight (<18.5) | 15 (5) | 15 (3) | 3.0 (1.4–6.5) | <0.0001 |
| Normal (18.5–24.9) | 85 (30) | 259 (45) | Referent | |
| Overweight (25.0–29.9) | 77 (27) | 175 (30) | 1.3 (0.9–1.9) | |
| Obese 1 (30–34.9) | 51 (18) | 79 (14) | 2.0 (1.3–3.0) | |
| Obese 2 (35–39.9) | 31 (11) | 29 (5) | 3.3 (1.9–5.7) | |
| Obese 3 (>40) |
27 (10) |
21 (4) |
3.9 (2.1–7.3) |
|
| Concurrent conditions‡ | ||||
| Asthma | 114 (38) | 93 (15) | ||
| No regular medication | 25 (8) | 48 (8) | 1.4 (0.8–2.4) | <0.0001 |
| Regular medication | 89 (29) | 45 (7) | 5.4 (3.6–8.0) | |
| Previous hospitalization | 48 (16) | 24 (4) | ||
| Heart disease§ | 40 (14) | 41 (7) | 2.1 (1.3–3.3) | 0.0016 |
| Heart failure | 8 (20) | 1 (2) | ||
| Angina | 10 (25) | 7 (17) | ||
| Heart attack | 8 (20) | 9 (22) | ||
| Congenital condition | 6 (15) | 4 (10) | ||
| Rheumatic fever | 6 (15) | 1 (2) | ||
| Kidney disease¶ | 10 (3) | 8 (1) | 2.5 (1.0–6.5) | 0.0522 |
| Renal failure | 5 (50) | 4 (50) | ||
| Dialysis | 3 (30) | – | ||
| Transplant or waiting list | 4 (40) | – | ||
| Mental health problem | 53 (18) | 49 (8) | 2.4 (1.6–3.6) | <0.0001 |
| Neurologic problem | 24 (8) | 42 (7) | 1.2 (0.7–1.9) | 0.5925 |
| Immunosuppression | 30 (10) | 22 (4) | 2.9 (1.6–5.1) | 0.0002 |
| Obstructive sleep apnea | 37 (12) | 23 (4) | 3.5 (2.1–6.0) | <0.0001 |
| Lung disease | 58 (19) | 31 (5) | 4.4 (2.8–7.0) | <0.0001 |
| Regular medication | 39 (67) | 13 (42) | ||
| Previous hospitalization | 32 (55) | 11 (35) | ||
| Diabetes | 58 (19) | 38 (6) | 3.5 (2.3–5.5) | <0.0001 |
| Metabolic disorder | 3 (1) | 7 (1) | 0.9 (0.2–3.3) | 0.8204 |
| Liver disease | 23 (8) | 20 (3) | 2.4 (1.3–4.4) | 0.0053 |
| Blood disorder | 16 (5) | 16 (3) | 2.1 (1.0–4.2) | 0.0463 |
| Pregnancy | 40 (13) | 7 (1) | 13.0 (5.7–29.4) | <0.0001 |
| First trimester | 5 (13) | 2 (18) | ||
| Second trimester | 7 (18) | 3 (27) | ||
| Third trimester |
28 (70) |
2 (18) |
||
| Smoking status# | ||||
| Nonsmoker | 144 (48) | 372 (62) | Referent | |
| Current smoker | 66 (22) | 82 (14) | 2.1 (1.4–3.0) | 0.0002 |
| Former smoker |
91 (30) |
149 (25) |
1.6 (1.1–2.2) |
|
| Influenza vaccine in 2009** | 107 (36) | 202 (34) | 1.1 (0.8–1.5) | 0.529 |
*OR, odds ratio; CI, confidence interval.
†Groups are not mutually exclusive.
‡Body mass index calculated as weight in kilograms divided by height in meters squared. Data were missing for 16 case-patients and 25 controls.
§Data were missing for 6 case-patients and 12 controls.
¶Data were missing for 2 controls.
#Data were missing for 2 case-patients and 2 controls.
**Vaccination information was missing for 2 case-patients and 1 control.
