Exploring the Pathophysiology of Delirium: An Overview of Biomarker Studies, Animal Models, and Tissue-Engineered Models

Protein Alterations in Patients with Delirium after Cardiac Surgery: An Exploratory Case-Control Substudy of the VISION Cardiac Surgery Biobank

BACKGROUND

Delirium is an acute state of confusion associated with adverse postoperative outcomes. Delirium is diagnosed clinically using screening tools; most cases go undetected. Identifying a delirium biomarker would allow for accurate diagnosis, application of therapies, and insight into causal pathways. To agnostically discover novel biomarkers of delirium, a case-control substudy was conducted using the Vascular Events in Surgery Patients Cohort Evaluation (VISION) Cardiac Surgery Biobank. The objective was to identify candidate biomarkers to investigate in future studies.

METHODS

The study gathered a convenience sample of 30 patients with delirium on postoperative day 1 matched to 30 controls by age, sex, ethnicity, center, and cardiopulmonary bypass time. The Olink Explore 3K platform was used to identify blood protein alterations on postoperative day 3. Protein concentrations were expressed as normalized protein expression units (log 2 fold scale). Protein expression was compared between cases and controls using a paired t test and identified significantly different biomarkers based on a false discovery rate-adjusted P value of less than 0.05.

RESULTS

Of 2,865 unique serum proteins, 26 (0.9%) were significantly associated with delirium status; all were elevated in cases versus controls at a false discovery rate of less than 0.05. Pathway analysis identified calcium-release channel activity ( Padj = 0.02) and GTP-binding ( Padj = 0.005) functions as characteristic of proteins associated with delirium. The top three differentially expressed biomarkers were FKBP1B ( Padj = 0.003), C2CD2L ( Padj = 0.004), and RAB6B ( Padj = 0.004). The inflammatory biomarker interleukin-8 (CXCL8; mean difference = 2.36; P = 3.6 × 10- 4 ) was also associated with delirium.

CONCLUSIONS

The study identified 26 biomarkers significantly associated with delirium; all are novel except for interleukin-8. An association between delirium and recognized neuroinflammatory proteins or markers of brain injury was not identifed, which supports using biomarkers to differentiate between delirium and other neurologic conditions. While exploratory, the study's findings support using biomarkers to diagnose postoperative delirium and validate using agnostic screens to identify potential delirium biomarkers.

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.