Mortality Risk Following Delirium in Older Inpatients: A Systematic Review and Meta-Analysis

The onset of delirium in older inpatients is associated with worse outcomes, including longer length of hospital stay, loss of functionality, loss of cognitive function, sleep disorders, increased polypharmacy, higher rates of adverse effects, and mortality. Previous studies have analyzed mortality after delirium, but without discriminating between settings, time, or critical conditions.

To assess the pooled incidence of delirium and risk of mortality at different times after hospital admission in older people and its association with mortality and length of stay in hospitalized people aged 65 years or older.

This systematic review and meta-analysis included studies analyzing the incidence of delirium and mortality. MEDLINE, Scopus, and the Web of Science were searched from inception to December 2023. PRISMA guidelines were followed. Inclusion criteria were original peer-reviewed studies in medical hospital areas using validated screening or diagnostic methods and quantifying mortality at admission or after excluding surgical patients. Exclusion criteria were studies that included only participants with a single condition at baseline, such as cancer, pneumonia, or frailty, or who were admitted to a specific unit such as the intensive care unit, as well as studies that assessed delirium in surgical areas. Study quality was assessed with Joanna Briggs Institute Critical Appraisal tools. The statistical analysis was performed in RevMan v5.4.0 (Cochrane Collaboration, Oxford, UK), using a random-effects model to calculate incidence, mortality, and length of hospital stay along with their 95% confidence intervals (CIs). The PROSPERO registration number for the review was CRD42023491604.

In the 32 included studies, the pooled cumulative incidence of delirium was 28.79% (95% confidence interval [CI] 24.06%, 33.51%). The mortality risk was higher in patients who had delirium during admission (odds ratio [OR] 5.23, 95% CI [3.45, 7.93]). This varied by time point: 1 month, OR 3.80 (95% CI 2.40, 6.00); 6 months, OR 3.48 (95% CI [2.01, 6.01]); 12 months, OR 2.73 (95% CI [2.07, 3.60]); 2 years, OR 2.09 (95% CI [1.57, 2.78]); and 5 years, OR 3.34 (95% CI [2.40, 4.64]). In the pooled analysis, mean length of hospital stay was 2.26 days (95% CI [0.54, 3.99]) longer in patients with delirium.

This study shows the markedly increased risk of mortality in older people with delirium during hospital admission and over the first month, in addition to an increased length of stay. The onset of delirium leads to increased use of healthcare resources. These data help to quantify the impact that delirium has on the health of older people, with implications for health system management. The evidence highlights the need to implement preventive pharmacological treatment or multicomponent strategies that minimize the onset of delirium in the older population.

The PROSPERO registration number for the review was: CRD42023491604, available at: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=491604.