Risk factors for aspiration in community-acquired pneumonia: analysis of a hospitalized UK cohort

Abstract

Background: There is a move toward finding clinically useful "phenotypes" in community-acquired pneumonia: groups of patients displaying distinct clinical characteristics, microbiology, and prognosis. Aspiration pneumonia is an intuitive clinical phenotype; however, to date there are no recognized diagnostic criteria, and data regarding outcomes in suspected aspiration are limited.

Methods: An observational study of 1348 patients hospitalized with community-acquired pneumonia in the United Kingdom examined both short- and long-term outcomes for patients at risk of aspiration pneumonia. Patients were defined as "at risk" in the presence of chronic neurologic disorders, esophageal disorders and dysphagia, impaired conscious level, vomiting, or witnessed aspiration. The primary outcome was 30-day mortality. Secondary outcomes included 1-year mortality, readmissions, and recurrent pneumonia within 1 year.

Results: Some 13.8% of the cohort were classified as "at risk of aspiration." These patients were older (median age, 74 years [interquartile range, 60-84] vs 66 years [interquartile range, 49-77]; P < .0001) and more likely to have comorbidities (chronic liver disease 11.3% vs 3.7%, P < .0001; congestive heart failure 28% vs 17.1%, P = .0004; and stroke 26.9% vs 9.5%, P < .0001). Patients at risk of aspiration pneumonia had a poorer short-term outcome (30-day mortality 17.2% vs 7.7%, P < .0001), but after adjusting for their greater severity of illness and comorbidities this difference was not significant (odds ratio 1.05; 95% confidence interval [CI], 0.63-1.76; P = .8). However, patients with aspiration risk factors were at greater risk of poor long-term outcomes with increased 1-year mortality (hazard ratio [HR], 1.73; 95% CI, 1.15-2.58), increased risk of rehospitalization (HR, 1.52; 95% CI, 1.21-1.91), and a strong association with recurrent admissions with pneumonia (HR, 3.13; 95% CI, 2.05-4.78) after multivariable adjustment.

Conclusions: Using risk factors to identify patients at risk of aspiration pneumonia identifies a distinct clinically useful phenotype of patients with greater severity of disease and poorer long-term outcomes.

Keywords: Aspiration; Comorbidity; Microbiology; Mortality; Pneumonia; Prognosis; Severity.