Multimorbidity, readmissions and mortality among older patients with potentially preventable hospitalisations: a Danish nationwide cohort study

PURPOSE: We investigated the association between multimorbidity level, all-cause 30-day readmissions, and post-discharge 30-day mortality. METHODS: Using Danish national registries, we identified patients aged ≥ 65 years hospitalized for ambulatory care-sensitive conditions between 2013-2018. Multimorbidity was defined as having 2-3 (moderate) or ≥ 4 (severe) of 39 chronic conditions. We estimated 30-day cumulative incidence of readmission after discharge and used Cox regression to calculate hazard ratios (HRs) for readmission and mortality. RESULTS: Among 178,445 patients, median age was 78 years (IQR: 71-85), 59% were female. The 30-day readmission rate was 21% for those with severe multimorbidity, compared with 12% for those without multimorbidity and 16% for those with moderate multimorbidity. The hazard of 30-day readmission was elevated for both moderate (HR 1.4, 95% CI 1.4-1.5) and severe (HR 1.9, 95% CI 1.8-1.9) multimorbidity. Additionally, moderate and severe multimorbidity were associated with increased 30-day mortality (HR 1.9, 95% CI 1.7-2.1 and HR 2.6, 95% CI 2.4-2.8, respectively). CONCLUSION: Multimorbidity is associated with increased risk of hospital readmission and mortality, underscoring the need for improved care coordination in acute and post-discharge settings.