| Adjusted model: weighted count of clinical conditions* | Adjusted model: potentially preventable unplanned admissions† | |||
|---|---|---|---|---|
| Odds ratio (95% CI) | P value | Odds ratio (95% CI) | P value | |
| Male | 1.15 (1.10–1.19) | <0.001 | 1.30 (1.19–1.42) | <0.001 |
| Age | 1.04 (1.02–1.06) | <0.001 | 1.00 (0.96–1.04) | 0.83 |
| Age2 | 1.06 (1.06–1.07) | <0.001 | 1.06 (1.05–1.07) | <0.001 |
| Scottish Index of Multiple Deprivation | ||||
| 1 (least deprived) | Reference | <0.001 | Reference | <0.001 |
| 2 | 1.09 (1.00–1.18) | 1.28 (1.06–1.55) | ||
| 3 | 1.22 (1.13–1.32) | 1.51 (1.26–1.82) | ||
| 4 | 1.32 (1.22–1.44) | 1.48 (1.22–1.80) | ||
| 5 (most deprived) | 1.61 (1.48–1.75) | 1.76 (1.45–2.13) | ||
| Number of clinical conditions | ||||
| None | Reference | <0.001 | Reference | <0.001 |
| 1 | 1.31 (1.20–1.42) | 1.54 (1.13–2.11) | ||
| 2 | 1.59 (1.41–1.79) | 2.04 (1.34–3.10) | ||
| 3 | 1.70 (1.46–1.98) | 2.22 (1.33–3.72) | ||
| 4 or 5 | 2.09 (1.76–2.48) | 2.67 (1.49–4.80) | ||
| ≥6 | 3.05 (2.43–3.83) | 3.94 (2.12–7.34) | ||
| Number of medications | ||||
| None | 0.65 (0.61–0.70) | <0.001 | 0.59 (0.44–0.81) | <0.001 |
| 1–3 | Reference | Reference | ||
| 4–6 | 1.50 (1.37–1.65) | 2.01 (1.36–2.97) | ||
| 7–9 | 2.35 (2.09–2.64) | 2.37 (1.40–4.00) | ||
| ≥10 | 3.80 (3.33–4.34) | 7.95 (4.56–13.86) | ||
| Interaction between clinical conditions and number of medications | ||||
| Number of conditions × no medications | 1.25 (1.17–1.33) | <0.001 | 1.13 (0.98–1.29) | 0.007 |
| Number of conditions × 4–6 medications | 0.87 (0.82–0.92) | 0.90 (0.79–1.01) | ||
| Number of conditions × 7–9 medications | 0.76 (0.72–0.81) | 0.94 (0.82–1.09) | ||
| Number of conditions × ≥10 medications | 0.76 (0.71–0.81) | 0.82 (0.71–0.95) | ||
The effect of age is given in terms of an odds ratio for a change of 10 years. P values are based on joint test of overall variability across categories.
An additional model was constructed by replacing the simple clinical condition count with a weighted count of certain conditions based on the original Charlson index 31. This index is weighted based on mortality. A pragmatic approach was used in developing modified weightings, because the list of conditions included in the Charlson index is not concordant with the list of 40 conditions included in our own analysis. For example, we cannot include HIV/AIDS (albeit rare in Scotland, and probably less strongly associated with admission since highly active antiretroviral therapy use became routine) and are unable to distinguish solid/blood cancers, severity of liver disease, complications of diabetes, or hemiplegia resulting from stroke. The following conditions were included to create a weighted count (weightings in parentheses as per the original Charlson index): ischaemic heart disease (1), heart failure (1), stroke (1), dementia (1), chronic obstructive pulmonary disease (1), connective tissue/rheumatological conditions (1), viral hepatitis or chronic liver disease (1), diabetes (1), chronic kidney disease (2) and cancer (2).
A further model was constructed to examine the alternative outcome of potentially preventable unplanned admissions, which are a subset of the main outcome. Potentially preventable admissions are those for conditions which are considered most preventable by better primary and outpatient care, and were defined using a standard NHS Scotland list 32.