Prognostic Nutritional Index, Circulating Bacterial and Viral DNA, and Neurocognitive Vulnerability in Geriatric Inpatients: A Cross-Sectional Study

Background/Objectives: Impaired immunonutritional status is common among hospitalized older adults and may contribute to adverse outcomes through alterations in gut–brain axis pathways involving immune, microbial, and inflammatory mechanisms. The Prognostic Nutritional Index (PNI), a composite marker based on serum albumin and lymphocyte count, may identify patients with altered immunonutritional status and increased clinical vulnerability. This cross-sectional study investigated whether PNI-defined immunonutritional impairment is associated with bacterial and viral DNAemia, inflammation, and neurocognitive conditions in 1016 geriatric patients from the Report-AGE cohort.