This was a retrospective, cohort study of inpatients admitted to a community-based hospital and a teaching hospital in Japan from January 2015 to December 2018. This study was approved by the institutional review boards of the hospitals and conformed to the provisions of the Declaration of Helsinki (as revised in Brazil 2013).
Functional status was evaluated by the Barthel Index (BI) (range, 0–100, in 5-point increments) of activities of daily living (ADL). ADL was graded into three categories according to the BI: independent, BI 80–100; semi-dependent, BI 30–75; and dependent, BI 0–25. A decline in functional status was considered a decrease in ADL of at least one category. Functional status was assessed at admission and discharge. The need for rehabilitation was determined on the days of admission. Duration of antibiotic treatment was determined by including both parenteral and oral anti-bacterial agents.
Elderly hospitalized CAP patients were divided into two groups: maintained group, without deterioration of functional status; and decreased group, with decreased functional status. All enrolled cases had been diagnosed with CAP according to the definitions of the American Thoracic Society/Infectious Diseases Society of America guideline11. Patients who fulfilled all of the following inclusion criteria were enrolled in the study: 1) age > 64 years; 2) symptoms compatible with pneumonia (e.g., fever, cough, sputum, pleuritic chest pain, or dyspnea); and 3) appearance of new pulmonary infiltrates consistent with pneumonia on chest X-ray or computed tomography. To ensure that all eligible cases were enrolled, the study investigators screened the hospital database for International Classification of Diseases, 10th revision (ICD-10) codes and reviewed hospital medical records.
Cases of healthcare-associated pneumonia (HCAP) and hospital-acquired pneumonia (HAP) were excluded12. Repeated episodes of pneumonia in the same patient within a 2-week period were regarded as a single episode. Cases with complications that occurred during admission (e.g., myocardial infarction, femoral fracture, cerebral infarction) and that would have affected functional status were also excluded.
The primary outcome was the length of hospital stay. Demographic information, duration of antibacterial treatment, comorbidities, laboratory values on admission, vital signs, in-hospital mortality, and site of acquisition for survivors were also collected. Comorbidities were identified according to the Charlson Comorbidity Index13 (CCI). The Pneumonia Severity Index14 (PSI) score was calculated based on data obtained at the time of admission.
The results are presented as numbers and percentages or medians and interquartile ranges unless otherwise indicated. Groups were compared using Wilcoxon rank-sum tests. In order to check effect of rehabilitation affecting functional status, risk factors for decreased functional status were determined using stepwise regression analysis. Confounding variables of decreased functional status, age, sex, BMI, aspiration, dementia, disorder of consciousness (DOC), undergoing rehabilitation, pre-admission ADL, PSI, CCI, and length of hospital stay were chosen as candidates. Using the model of the minimum corrected Akaike’s information criterion (AICc) in the backward direction, the final variables were determined. McNemar’s test was performed to check the effect of rehabilitation in preventing decreased functional status for matched pairs after propensity score analysis. In all instances, two-tailed values of p < 0.05 were considered significant. Data analysis was performed using JMP software (version 15.0; SAS Institute, Cary, NC).