Factors driving outcome variability in aspiration and community-acquired pneumonia: a meta-analysis

BACKGROUND: Aspiration community-acquired pneumonia (ACAP) is common among older adults and is associated with worse outcomes than nonaspiration community-acquired pneumonia (CAP). Understanding these differences is essential for improving patient care. OBJECTIVES: To determine the prevalence of ACAP among pneumonia patients and compare clinical outcomes, including hospital length of stay, intensive care unit (ICU) admissions and mortality rates, between patients with ACAP and those with CAP. METHODS: A systematic review and meta-analysis were conducted following MOOSE (Meta-Analysis of Observational Studies in Epidemiology) and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Literature searches in PubMed, Embase and Google Scholar from January 1995 to January 2024 identified studies involving adults diagnosed with CAP or ACAP. Data extraction and quality assessment were performed independently by two reviewers. Random-effects meta-analysis and meta-regression analyses were conducted to identify sources of heterogeneity. RESULTS: 49 samples from 44 studies were included, encompassing 1 277 615 older adults (mean age 80.2 years). The pooled prevalence of ACAP was 25% (95% CI 19-31) and higher in studies with a mean age of 70 years or older at 32% (95% CI 25-39). Compared to CAP patients, those with ACAP had significantly longer hospital stays (mean difference 4.92 days, 95% CI 4.71-5.14), increased ICU admissions (risk ratio 2.33, 95% CI 1.77-3.07), higher in-hospital mortality (risk ratio 2.14, 95% CI 1.73-2.65), higher 30-day mortality (risk ratio 2.56, 95% CI 2.12-3.1), higher 1-year mortality (risk ratio 1.96, 95% CI 1.44-2.66) and greater recurrence rates (risk ratio 1.75, 95% CI 1.44-2.66). Meta-regression identified publication year, patient age, study design, nursing home residency and compliance with therapeutic guidelines as significant moderators explaining heterogeneity. CONCLUSIONS: Patients with ACAP experience significantly worse clinical outcomes than those with CAP. These findings highlight the importance of early identification and management of aspiration risks, adherence to therapeutic guidelines and the need for standardised diagnostic criteria to improve outcomes in this vulnerable population.