Factors associated with intensive-care-unit admission
| Univariate OR | Multivariate-adjusted OR | p Value | ||
| Age (per decade) | 0.90 (0.81 to 1.00) | 0.05 | ||
| Sex | ||||
| Female | 1 (referent) | 0.26 | ||
| Male | 0.79 (0.52 to 1.2) | |||
| Influenza strain | ||||
| H1N1/09 | 2.1 (1.0 to 4.1) | 0.04 | 1.9 (0.9 to 4.0) | 0.08 |
| Other strain | 1 | |||
| Radiologically confirmed pneumonia | 6.7 (4.2 to 10.5) | <0.001 | NI (in causal pathway) | |
| Smoking | NI (missing data) | |||
| Non-smoker | 1 | |||
| Current | 0.87 (0.50 to 1.4) | 0.61 | ||
| Past | 0.51 (0.26 to 0.97) | 0.04 | ||
| Asthma | 0.62 (0.38 to 1.03) | 0.07 | ||
| Chronic obstructive pulmonary disease | 0.48 (0.25 to 0.94) | 0.03 | 0.54 (0.27 to 1.07) | 0.08 |
| Diabetes | 0.91 (0.53 to 1.59) | 0.76 | ||
| Pregnancy | 2.6 (1.3 to 4.9) | 0.004 | 2.5 (1.3 to 4.8) | 0.007 |
| Liver disease | 2.3 (1.1 to 4.9) | 0.03 | 2.8 (1.3 to 5.9) | 0.008 |
| Immunosuppression | 0.92 (0.53 to 1.6) | 0.78 | ||
| Current malignancy | 0.92 (0.46 to 1.84) | 0.82 | ||
| Cardiac failure | 0.83 (0.36 to 1.9) | 0.74 | ||
| Ischaemic heart disease | 0.54 (0.25 to 1.2) | 0.13 | ||
| Obesity | 1.9 (1.1 to 3.2) | 0.03 | NI | |
| Chronic neurological disease | 0.40 (0.17 to 0.97) | 0.12 | ||
| Chronic renal disease | 1.3 (0.63 to 2.8) | 0.46 | ||
NI, not included in final model owing to the high proportion of missing data. Hosmer–Lemeshow goodness-of-fit statistic for final model, p=0.82. NI, not included in final model.