Advantages of short-term antimicrobial treatment for pneumonia and aspiration pneumonia in older patients aged over 65: A nationwide inpatient database study

The duration of antimicrobial therapy required to treat community-acquired pneumonia is often longer than expected, likely because of the high number of such inpatients in developed countries with aging populations. In this study, we evaluated the effects of short-term treatments for both pneumonia and aspiration pneumonia in older Japanese adults using the nation's inpatient database. Inpatients aged ≥ 65 years who were admitted to the hospital for pneumonia or aspiration pneumonia between April 1, 2018, and October 31, 2018, were included. We compared patients treated <i>via</i> intravenous antibiotics for 3-7 days to control patients treated with a similar regimen for 8-28 days, using inverse probability of treatment-weighted Cox regression. The primary outcome was relapse or readmission for pneumonia and death within 30 days after completing antimicrobial therapy. The secondary outcomes were average treatment effect for <i>Clostridioides difficile</i> infection (CDI), chest drainage, and length of hospital stay. The total number of eligible patients was 72,294. The hazard ratio for the primary outcome was 1.04 (95% confidence interval: 0.99-1.10). The mean length of hospital stay was shortened to 9.74 days (range, 9.34-10.1) in the short-term treatment group. The prevalence rates of CDI and chest drainage did not differ significantly between the short- and long-term treatment groups. We observed no statistically significant difference in clinical outcomes between the older adults with pneumonia including aspiration pneumonia who received short- <i>vs</i> long-term antimicrobial therapy.