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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 2

Risk factors for hospitalization caused by pandemic (H1N1) 2009 influenza for female case-patients and controls of childbearing age, Sydney, Australia, 2009*

Patient characteristic No. (%) case-patients, n = 99 No. (%) controls, n = 181 OR (95% CI) p value Adjusted OR (95% CI) p value
Age, y
16–25 28 (28) 43 (24) 1.4 (0.8–2.6)
26–35 37 (37) 64 (35) 1.3 (0.7–2.2) 0.5233
36–45
34 (34)
74 (41)
Referent



Aboriginal status
Nonindigenous 95 (98) 177 (96) Referent 0.3864
Indigenous
4 (4)
4 (2)
1.9 (0.5–7.6)



Body mass index†
Underweight (<18.5) 8 (9) 9 (5) 2.8 (1.0–8.0)
Normal (18.5–24.9) 31 (33) 99 (57) Referent
Overweight (25.0–29.9) 15 (16) 35 (20) 1.4 (0.7–2.8) 0.0003
Obese 1 (30.0–34.9) 17 (18) 18 (10) 3.0 (1.4–6.6)
Obese 2 (35.0–39.9) 10 (11) 4 (2) 8.0 (2.3–27.3)
Obese 3 (>40)
12 (13)
8 (5)
4.8 (1.8–12.8)



Health condition‡
Asthma 46 (46) 35 (19) Referent
No regular medication 7 (7) 21 (12) 0.9 (0.4–2.3) <0.001 10 (4.0–21.0) <0.0001
Regular medication 39 (39) 14 (8) 7.7 (3.9–15.3)
Heart disease§ 0 1 (0.5) <0.001 0.9871
Kidney disease 0 1 (0.5) <0.001 0.987
Mental health problem 17 (17) 19 (11) 1.8 (0.9–3.6) 0.1139
Neurologic problem 4 (4) 8 (4) 0.9 (0.3–3.1) 0.8809
Immunosupression 1 (1) 2 (1) 0.9 (0.1–10.2) 0.942
Obstructive sleep apnea 10 (10) 4 (2) 5.0 (1.5–16.3) 0.0081
Lung disease 10 (10) 4 (2) 5.0 (1.5–16.3) 0.0081 7 (2.0–28.0) 0.0043
Diabetes 14 (14) 2 (1) 14.7 (3.3–66.3) 0.0005 20 (4.0–103.0) 0.0003
Metabolic disorder 1 (1) 2 (1) 0.9 (0.1–10.2) 0.942
Liver disease 5 (5) 0 >999.9 0.9798
Blood disorder 4 (4) 8 (4) 0.9 (0.3–3.1) 0.8809
Pregnancy
40 (40)
7 (4)
16.9 (7.2–39.6)
<0.001
28 (11.0–70.0)
<0.0001
Smoking status
Nonsmoker 53 (54) 130 (72) Referent
Current smoker 24 (24) 32 (18) 1.8 (1.0–3.4) 0.0057
Former smoker
22 (22)
19 (11)
2.8 (1.4–5.7)



Influenza vaccine in 2009¶ 20 (20) 30 (17) 1.3 (0.7–2.4) 0.4262

*OR, odds ratio; CI, confidence interval.
†8 controls and 6 case-patients missing data.
‡Groups are not mutually exclusive.
§1 control and 3 case-patients missing data.
¶1 case-patient missing data.

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