Table 2: Two level random intercept negative binomial regression models for length of stay and bed days per person per year. IRR is incidence rate ratio compared to the reference category – the ratio of expected length of stay or number of bed days.
| Length of Stay | Bed days per year | |||||||
|---|---|---|---|---|---|---|---|---|
|
|
|
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| IRR | 95% CI | P value | IRR | 95% CI | P value | |||
| Financial year | ||||||||
| Change per year | 0.96 | 0.96 | 0.96 | <0.01 | 0.98 | 0.98 | 0.98 | <0.01 |
| Gender | ||||||||
| Male | 1 (ref) | 1 (ref) | ||||||
| Female | 1.02 | 1.02 | 1.03 | <0.01 | 1.01 | 1 | 1.01 | 0.02 |
| Ethnic group | ||||||||
| White | 1 (ref) | 1 (ref) | ||||||
| Indian | 0.94 | 0.93 | 0.96 | <0.01 | 1.03 | 1.02 | 1.05 | <0.01 |
| Pakistani | 0.99 | 0.97 | 1 | 0.03 | 1.04 | 1.02 | 1.05 | <0.01 |
| Bangladeshi | 1.01 | 0.98 | 1.03 | 0.58 | 1.02 | 1 | 1.04 | 0.12 |
| Black | 1.05 | 1.04 | 1.06 | <0.01 | 1.03 | 1.02 | 1.04 | <0.01 |
| Chinese | 0.87 | 0.82 | 0.91 | <0.01 | 1.01 | 0.97 | 1.06 | 0.6 |
| Mixed | 1.04 | 1.02 | 1.06 | <0.01 | 1 | 0.99 | 1.02 | 0.74 |
| Other | 1 | 0.99 | 1.02 | 0.52 | 1.05 | 1.03 | 1.06 | <0.01 |
| Age group | ||||||||
| Under 1 | 1.85 | 1.83 | 1.86 | <0.01 | 2.36 | 2.34 | 2.37 | <0.01 |
| 1 to 4 | 0.97 | 0.96 | 0.98 | <0.01 | 1.05 | 1.04 | 1.05 | <0.01 |
| 5 to 9 | 1 (ref) | 1 (ref) | ||||||
| 10 to 14 | 1.24 | 1.23 | 1.25 | <0.01 | 1.13 | 1.12 | 1.13 | <0.01 |
| 15 to 19 | 1.39 | 1.38 | 1.41 | <0.01 | 1.22 | 1.22 | 1.23 | <0.01 |
| Main diagnostic group | ||||||||
| Malignant neoplasms (C) | 0.37 | 0.36 | 0.37 | <0.01 | 1.24 | 1.21 | 1.27 | <0.01 |
| Benign neoplasms (D) | 0.74 | 0.68 | 0.8 | <0.01 | 1.17 | 1.09 | 1.25 | <0.01 |
| Metabolic (E) | 0.83 | 0.81 | 0.84 | <0.01 | 1.13 | 1.11 | 1.15 | <0.01 |
| Mental/behavioural (F) | 0.95 | 0.95 | 0.96 | <0.01 | 0.87 | 0.87 | 0.88 | <0.01 |
| Nervous system (G) | 1 (ref) | 1 (ref) | ||||||
| Congenital (Q) | 0.82 | 0.81 | 0.83 | <0.01 | 0.98 | 0.98 | 0.99 | <0.01 |
| Other (R) | 0.99 | 0.98 | 1.01 | 0.29 | 0.74 | 0.73 | 0.74 | <0.01 |
| Deprivation category | ||||||||
| 1 (most deprived) | 1(ref) | 1 (ref) | ||||||
| 2 | 1.01 | 1 | 1.02 | 0.03 | 0.99 | 0.99 | 1 | 0.01 |
| 3 | 1.03 | 1.02 | 1.04 | <0.01 | 0.99 | 0.98 | 1 | 0.01 |
| 4 | 0.98 | 0.98 | 0.99 | <0.01 | 0.98 | 0.97 | 0.99 | <0.01 |
| 5 (least deprived) | 0.97 | 0.96 | 0.98 | <0.01 | 0.98 | 0.97 | 0.99 | <0.01 |
| Government Office Region of Residence | ||||||||
| North East | 1.15 | 1.14 | 1.17 | <0.01 | 1 | 0.99 | 1.01 | 0.75 |
| North West | 1 (ref) | 1 (ref) | ||||||
| Yorkshire and Humber | 1.21 | 1.2 | 1.23 | <0.01 | 1.02 | 1.01 | 1.03 | <0.01 |
| East Midlands | 1.21 | 1.19 | 1.22 | <0.01 | 1.04 | 1.03 | 1.05 | <0.01 |
| West Midlands | 1.21 | 1.2 | 1.23 | <0.01 | 1.01 | 1 | 1.02 | 0.04 |
| East of England | 1.15 | 1.14 | 1.16 | <0.01 | 1.03 | 1.02 | 1.04 | <0.01 |
| London | 1.06 | 1.05 | 1.08 | <0.01 | 1.03 | 1.02 | 1.04 | <0.01 |
| South East | 1.21 | 1.2 | 1.23 | <0.01 | 1.03 | 1.02 | 1.04 | <0.01 |
| South West | 1.07 | 1.06 | 1.08 | <0.01 | 1 | 0.99 | 1.01 | 0.97 |
| Model parameters | ||||||||
| Degrees of freedom | 34 | 34 | ||||||
| Log likelihood | -3072235 | -2379091 | ||||||
| BIC | 6144956 | 4758646 | ||||||