Five-decade prevalence of delirium in pneumonia, risk factors and associated mortality: a systematic review and meta-analysis.

Publication date: Jul 01, 2025

Delirium can occur in patients with pneumonia, but its prevalence is inconsistent across studies. Unreliable estimates and uncertainty regarding the significance of patient-specific versus microbiological risk factors hinder delirium management and prognosis. Here, we provide robust estimates of delirium prevalence in patients with pneumonia, associated risk factors and association with mortality. We searched five databases (Medline, Cochrane Library, Embase, PsycINFO and Scopus), from inception to 6 August 2024. We included studies in adults hospitalised with pneumonia reporting delirium, encephalopathy or altered mental status. Two investigators extracted data and assessed risk of bias. Summary rates were calculated using random-effects models. We performed prespecified analyses for diagnostic methods, microbiologic factors, clinical factors and mortality, with sensitivity analysis among studies at low risk of bias. The review protocol was registered with PROSPERO: CRD42023385571. Delirium prevalence across 126 studies was 22% (95% CI 18-26%) and higher in studies at low risk of bias (40%, 95% CI 24%-58%; n=11). Standardised assessments yielded higher rates than symptom- or International Classification of Diseases code-based assessments (p

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