Delirium in older adults is associated with development of new dementia: a systematic review and meta-analysis

Objectives: Observational studies have examined the association between delirium and development of new dementia. However, no recent review has collectively assessed the available evidence quantitatively and qualitatively. We systematically reviewed and critically evaluated the literature regarding the association between delirium and dementia, and calculated the odds of developing new dementia after having delirium.

Methods: This systematic review and meta-analysis was conducted according to Preferred reporting items for systematic reviews and meta-analyses guidelines. MEDLINE, EMBASE and PsycINFO, were searched for English-language articles that compared the incidence of new dementia in older adult (≥65) inpatients with delirium, to inpatients without delirium. A random effects model was used for meta-analysis, and overall effect size was calculated using reported raw data of event counts. The Newcastle-Ottawa Quality Assessment scale assessed risk of bias.

Results: Six observational studies met eligibility criteria, with follow-up times ranging from six months to five years. Four looked at hip fracture surgical patients; one was on cardiac surgery patients and one examined geriatric medical patients. All studies excluded patients with pre-existing dementia. Pooled meta-analysis revealed that older adult inpatients who developed delirium had almost twelve times the odds of subsequently developing new dementia compared to non-delirious patients (OR = 11.9 [95% CI: 7.29-19.6]; p < 0.001).

Conclusions: Older adult inpatients who develop delirium are at significant risk of subsequently developing dementia. This emphasises the importance of delirium prevention and cognitive monitoring post-delirium. The included studies mainly examined post-surgical patients-further research on medical and intensive care unit cohorts is warranted. Future studies should assess whether delirium duration, severity and subtype influence the risk of developing dementia.