Nutritional Status and Inflammation as Mediators of Physical Performance and Delirium in Elderly Community-Acquired Pneumonia Patients: A Retrospective Cohort Study.

Purpose: This study proposes a multiple mediation model to evaluate the association among diminished physical performance, malnutrition, inflammation, and delirium in seniors with community-acquired pneumonia. Patients and Methods: This retrospective cohort study included elderly patients hospitalized for community-acquired pneumonia at the Geriatrics Department of the Second People's Hospital of Lianyungang from January 1, 2020, to January 1, 2024. Logistic regression analysis was conducted to examine the associations among physical performance, nutritional status, C-reactive protein (CRP) levels, and delirium. Mediation models assessed the effects of nutritional status and CRP on the relationship between physical performance and delirium, with subgroup analyses based on diabetes status. Results: A total of 379 patients were included, with a mean age of 80.0±7.4 years, and 51.7% were male. The incidence of delirium during hospitalization was 28.5% (n=108). Subgroup analyses revealed significant correlations between physical performance, nutritional status, and CRP (P<0.001), regardless of diabetes status. After adjusting for confounding variables, CRP was positively associated with delirium, while MNA-SF and SPPB scores showed negative correlations with delirium risk (OR=0.852, 95% CI: 0.730-0.995; OR=0.580, 95% CI: 0.464-0.727, P<0.05). Mediation analyses indicated that MNA-SF scores and CRP significantly mediated the association between SPPB and delirium. Specifically, pathways "SPPB→ MNA-SF→ delirium", "SPPB→ CRP→ delirium", and "SPPB→ MNA-SF→ CRP→ delirium" demonstrated significant mediating effects in patients without diabetes, while only the pathway "SPPB→ MNA-SF→ CRP→ delirium" was significant in those with diabetes. Conclusion: Older patients with community-acquired pneumonia and poor physical performance are more susceptible to delirium, with nutritional status and inflammation as key mediators.