| Factor | Adjusted OR* (95% CI) |
| Age, yr† | |
| < 65 (ref) | 1.00 |
| 65–74 | 1.26 (1.23–1.30) |
| 75–84 | 1.49 (1.43–1.55) |
| ≥ 85 | 2.05 (1.90–2.21) |
| Sex | |
| Female (ref) | 1.00 |
| Male | 1.15 (1.13–1.16) |
| Neighbourhood household income‡ | |
| Highest quintile (ref) | 1.00 |
| Next to highest quintile | 0.99 (0.96–1.03) |
| Middle quintile | 1.01 (0.98–1.04) |
| Next to lowest quintile | 1.03 (0.98–1.09) |
| Lowest quintile | 1.01 (0.98–1.05) |
| Admissions to hospital in previous year† | |
| 1 (ref) | 1.00 |
| ≥ 2 | 1.11 (1.09–1.14) |
| Physician clinic visits in previous year† | |
| ≤ 6 (ref) | 1.00 |
| ≥ 7 | 0.97 (0.94–1.00) |
| Charlson Comorbidity Index† | |
| ≤ 1 (ref) | 1.00 |
| ≥ 2 | 1.87 (1.80–1.94) |
| Primary length of stay† longer than cohort median | |
| No (ref) | 1.00 |
| Yes | 1.20 (1.17–1.23) |
| Hospital-free interval† longer than cohort median | |
| No (ref) | 1.00 |
| Yes | 1.03 (1.00–1.05) |
| Residence in chronic care facility at readmission | |
| No (ref) | 1.00 |
| Yes | 1.31 (1.25–1.37) |
| Most responsible diagnosis for readmission§ | |
| Cardiac arrest | 7.23 (5.70–9.18) |
| Malignant neoplasm | 3.57 (3.16–4.03) |
| Sepsis | 3.10 (2.72–3.53) |
| Liver disease | 2.29 (2.03–2.59) |
| Pneumonia | 1.87 (1.69–2.07) |
| Nephrolithiasis | 0.44 (0.41–0.47) |
| Nonspecific abdominal pain | 0.40 (0.36–0.43) |
| Nonspecific chest pain | 0.26 (0.24–0.28) |
| Syncope and collapse | 0.24 (0.22–0.27) |
| Prostatic hypertrophy | 0.24 (0.20–0.29) |
| Miscellaneous (ref) | 1.00 |
| Arrival by ambulance at readmission | |
| No (ref) | 1.00 |
| Yes | 1.95 (1.88–2.01) |
| Year of readmission† | |
| 1994–1999 (ref) | 1.00 |
| 2000–2005 | 0.95 (0.92–0.99) |
| 2006–2010 | 0.87 (0.83–0.92) |
| Sector of secondary hospital | |
| Community (ref) | 1.00 |
| Academic | 0.70 (0.59–0.82) |
| Case volume of secondary hospital† | |
| Lower (ref) | 1.00 |
| Higher | 1.04 (0.86–1.25) |
Note: CI = confidence interval, OR = odds ratio, ref = reference group. *Adjusted for age, sex, neighbourhood average household income, rural residence, year of readmission, Charlson comorbidity index, primary length of stay, most responsible diagnosis at readmission to hospital, arrival by ambulance at readmission, chronic care facility residency at readmission, admission to hospital in previous year, physician clinic visits in previous year, hospital-free interval and secondary hospital case volume and sector. †Variables were analyzed as continuous data but are presented here in categories to facilitate interpretation. ‡Missing data were coded as such and included in analyses; however, this was uncommon (< 0.003% of all data) and not presented here. §The 5 diagnostic categories with the greatest effect on mortality and the 5 with the least effect were selected for presentation here. For a full listing, see eTable 8 in Appendix 1.