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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. SpokesComments to Author , and Jeremy M. McAnulty
Author affiliations: Author affiliation: New South Wales Department of Health, Sydney, New South Wales, Australia

Main Article

Table 4

Comparison of characteristics of patients with cases of pandemic (H1N1) 2009 influenza by time from symptom onset to medical attention, Sydney, Australia, 2009*

Patient characteristic
Medical attention within 48 h OR (95% CI)
p value
Yes, no. (%) patients, n = 235
No, no. (%) patients, n = 60
Sex
M 97 (41) 24 (40)
F
138 (59)
36 (60)
1.1 (0.6–1.9)
0.8576
Age, y
16–25 33 (14) 5 (8) 1.1 (0.3–4.3)
26–35 44 (19) 9 (15) 0.8 (0.3–2.8)
36–45 47 (20) 11 (18) 0.7 (0.2–2.3)
46–55 50 (21) 20 (33) 0.4 (0.1–1.3)
56–65 32 (14) 10 (17) 0.6 (0.2–1.8)
>65
29 (12)
5 (8)

0.3677
Aboriginal status
Nonindigenous 229 (97) 58 (97) 0.7409
Indigenous
6 (3)
2 (3)
0.8 (0.1–3.9)

Body mass index†
Underweight (<18.5) 13 (6) 2 (3) 1.6 (0.3–7.8)
Normal (18.5–24.9) 65 (28) 16 (27) 0.4457
Overweight (25.0–29.9) 67 (29) 10 (17) 1.6 (0.7–3.9)
Obese 1 (30–34.9) 38 (16) 12 (20) 0.8 (0.3–1.8)
Obese 2 (35–39.9) 23 (10) 6 (10) 0.9 (0.3–2.7)
Obese 3 (>40)
19 (8)
8 (13)
0.6 (0.2–1.6)

Health condition‡
Asthma 89 (38) 24 (40) 0.3607
No regular medication 16 (7) 9 (15)
Regular medication 73 (31) 15 (25) 1.4 (0.7–2.6)
Heart disease§ 31 (13) 7 (12) 1.2 (0.5–2.8) 0.703
Kidney disease 8 (3) 2 (3) 1.0 (0.2–4.9) 0.9785
Mental health problem 34 (14) 17 (28) 0.4 (0.2–0.8) 0.0129
Neurologic problem 14 (6) 8 (13) 0.4 (0.2–1.0) 0.0586
Immunosuppression 22 (9) 6 (10) 0.9 (0.4–2.4) 0.8803
Obstructive sleep apnea 26 (11) 10 (17) 0.6 (0.3–1.4) 0.2399
Lung disease 46 (20) 11 (18) 1.1 (0.5–2.2) 0.828
Diabetes 48 (20) 10 (17) 1.3 (0.6–2.7) 0.5141
Liver disease 16 (7) 5 (8) 0.8 (0.3–2.3) 0.6823
Pregnancy
33 (14)
7 (12)
1.3 (0.5–3.2)
0.6008
Smoking status¶
Nonsmoker 113 (48) 26 (43)
Current or former smoker
121 (51)
34 (57)
0.8 (0.5–1.5)
0.493
Influenza vaccine in 2009# 86 (37) 19 (32) 1.3 (0.7–2.3) 0.4507

*OR, odds ratio; CI, confidence interval.
†Data missing for 10 case-patients who received medical attention within 48 h and 6 who did not.
‡Groups are not mutually exclusive.
§Data were missing for 6 case-patients who received medical attention within 48 h.
¶Data were missing for 1 case-patient who received medical attention within 48 h.
#Vaccination information was missing for 2 case-patients and 1 control.

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