Aspiration Pneumonia in Adults: Patient Characteristics, Diagnosis, Treatment, and Outcomes (ASPEN)

Background

Aspiration pneumonia is a clinically important condition in adults, particularly in older people and individuals with dysphagia, neurological disease, frailty, reduced functional ability, and other comorbidities. The diagnosis may be difficult to establish because aspiration is not always witnessed and documentation varies between patients and clinical settings. Diagnostic investigations, microbiological sampling, and antibiotic treatment may also vary in routine clinical practice.

A systematic description of patient characteristics, aspiration-related risk factors, diagnostic approaches, treatment patterns, and clinical outcomes may help identify gaps in clinical documentation and areas for future research. This is particularly relevant to older adults, in whom an episode of pneumonia may be associated with functional decline, prolonged hospitalization, increased care needs, and recurrent healthcare contacts.

Study design and setting

ASPEN (Aspiration Pneumonia Evaluation Network) is a retrospective, observational cohort study conducted in Region Örebro County, Sweden. The study uses existing medical records and does not assign interventions or alter patients' clinical care.

The study population comprises adults aged 18 years or older hospitalized during the period September 2024 through September 2026 with a registered diagnosis of aspiration pneumonia. Patients will be identified through diagnostic coding. The planned primary cohort includes each eligible patient once; subsequent admissions will be handled as follow-up events rather than as new primary cohort observations.

Data collection

Data will be collected through structured review of existing medical records using a predefined data collection form. Variables will include:

Demographic characteristics, living situation, functional status, cognition, communication, nutritional status, and relevant comorbidities.

Risk factors for aspiration and the documentation and classification of the suspected or documented aspiration event.

Clinical presentation, vital signs, laboratory results, radiological findings, and microbiological investigations.

Antibiotic treatment, including antibiotic selection, broad- or narrow-spectrum treatment, anaerobic coverage, treatment duration, changes in treatment, and treatment at discharge where documented.

Other healthcare interventions, clinical deterioration, level of care, intensive or intermediate care, and length of hospital stay.

Discharge destination and follow-up outcomes, including readmission, a new documented episode of aspiration pneumonia, and death within 90 days, where information is available in the records.

Only information documented in the medical record will be recorded. Missing or undocumented information will not be inferred by the reviewer.

Outcomes and analyses

The study will primarily provide a descriptive characterization of the cohort and its clinical course. Analyses will summarize patient characteristics, aspiration-related risk factors, diagnostic investigations, microbiological findings, antibiotic treatment patterns, healthcare utilization, and clinical outcomes.

Exploratory analyses will examine associations between patient and disease characteristics, diagnostic findings, treatment patterns, and documented outcomes where the available data and number of outcome events permit. Antibiotic treatment patterns, including anaerobic coverage and treatment duration, will be described to characterize clinical practice and variation. The study is not designed to establish causal treatment effects or determine which antibiotic regimen is superior.

Ethical considerations

The study involves retrospective review of existing medical records. Ethical review and the necessary approvals will be obtained before the medical record review begins. Data will be handled in accordance with applicable Swedish requirements for research ethics, confidentiality, and personal data protection. Study data will be coded using study-specific identifiers, and direct identifiers will not be included in the analysis dataset.

Purpose and expected contribution

The study aims to provide a structured description of adults hospitalized with aspiration pneumonia in Region Örebro County. It is expected to identify patterns in patient characteristics, diagnostic practice, treatment, clinical course, and outcomes, as well as limitations in the completeness of routinely documented data. The findings will inform future research and the development of more standardized data collection, with particular relevance to older adults, functional outcomes, and healthcare needs.