The Impact of Comorbid Dementia and Diabetes Mellitus on Hospital Patients’ Outcomes: A Systematic Review and Meta-analysis

Previous reviews have demonstrated that dementia and diabetes mellitus, separately, can worsen the hospital outcomes of patients. Unfortunately, there are no systematic evaluations regarding the hospital outcomes of patients with dementia and diabetes mellitus as a comorbidity. Therefore, our review aimed to determine any differences in hospital length of stay, hospital mortality, and hospital readmission between patients with the comorbidity and patients without.

Searches were conducted of Medline, CINHAL, EMBASE, PsychINFO, Web of Science and Google Scholar for original studies. All studies were quality assessed using the Joanna Briggs Institute critical appraisal tools. Where possible, studies were pooled in a meta-analysis to generate odds ratios (OR) with 95% confidence intervals (CI).

Sixteen studies were included in this review. When comparing patients with the comorbidity to patients with dementia, the difference in length of stay was inconclusive, and there was no difference in the odds of hospital mortality (OR = 0.98, 95% CI 0.91–1.06). However, patients with the comorbidity had increased odds of 30-day readmission compared to patients with dementia alone (OR = 1.20, 95% CI 1.14–1.26). When comparing patients with the comorbidity to patients with diabetes, those with the comorbidity had a longer length of stay and but no difference in the odds of hospital mortality (OR = 1.48, 95% CI 0.84–2.62). Additionally, those with the comorbidity may have worse readmission outcomes than those with diabetes alone.

Our findings suggest that patients with comorbid dementia and diabetes mellitus may have worse hospital outcomes. Therefore, we recommend further research to assess these patients’ hospital outcomes to resolve the discrepancies found.