A Review of Biomarkers in Delirium Superimposed on Dementia (DSD) and Their Clinical Application to Personalized Treatment and Management

Optimization of the cardiac delirium index by including age, decrease in butyrylcholinesterase actitivity, preoperative HbA1c, and postoperative hemoglobin levels: results of a secondary analysis of a prospective observational study

Introduction

Postoperative delirium (POD) after cardiac surgery significantly affects the perioperative morbidity and mortality. Butyrylcholinesterase (BChE) is an enzyme primarily produced in the liver, which plays a crucial role in the hydrolysis of acetylcholine outside of neuronal synapses, referred to as extraneuronal hydrolysis. The integration of BChE activity into the cardiac delirium (CARDEL) index might increase its predictive power for identifying POD after cardiac surgery. Therefore, the primary aim of this study was to assess the applicability of the CARDEL index and determine whether integrating the BChE activity enables optimization of the predictive model.

Methods

This secondary analysis of a prospective observational study included patients undergoing elective coronary artery bypass graft surgery. BChE activity is expressed in units per liter (U/L), while the BChE drop refers to the percentage decrease in BChE activity from pre- to postoperative levels. POD risk factors were identified using multivariate regression analysis. The predictive power of the CARDEL index and an optimized model including BChE was calculated with receiver operating characteristic (ROC) analysis.

Results

Of 93 included patients, 20 (21.5%) developed POD. Elevated preoperative HbA1c [OR 2.5 (1.2-4.8), p = 0.01], a decrease in BChE activity [%, OR 1.1 (1.0-1.2), p = 0.04], age [1 (0.94-1.1), p = 0.55], and a postoperative hemoglobin change [OR 0.86 (0.78-0.96), p < 0.001] were identified as independent risk factors for POD. While the CARDEL index showed a moderate prediction of POD [AUCROC of 0.74 (0.60-0.87)], the optimization including BChE resulted in a significant prognostic improvement: AUCROC of 0.84 (0.72-0.94, p < 0.001).

Conclusion

Despite the small size of this derivation cohort, this study identified elevated HbA1c as the strongest risk factor for the development of POD, followed by a decrease in BChE activity, postoperative anemia, and age, respectively. By including these parameters to the CARDEL index, its predictive power for the identification of POD significantly improved in this derivation cohort. Moving forward, integrating these findings into clinical practice could enhance early risk stratification and targeted intervention for patients at high risk of POD. Therefore, further research should evaluate these results in a larger, external cohort.

Molecular mechanisms implicated in protein changes in the Alzheimer's disease human hippocampus

This study aimed to elucidate the specific biochemical pathways linked to changes in proteins in the Alzheimer's disease (AD) human hippocampus. Our data demonstrate a constant rise in the expression of four proteins (VGF, GFAP, HSPB1, and APP) across all eleven studies. Notably, UBC was the most centrally involved and had increased expression in the hippocampus tissue of individuals with AD. Modified proteins in the hippocampal tissue were found to activate the innate immune system and disrupt communication across chemical synapses. Four hub proteins (CD44, APP, ITGB2, and APOE) are connected to amyloid plaques, whereas two hub proteins (RPL24 and RPS23) are related to neurofibrillary tangles (NFTs). The presence of modified proteins was discovered to trigger the activation of microglia and decrease the functioning of ribosomes and mitochondria in the hippocampus. Three significant microRNAs (hsa-miR-106b-5p, hsa-miR-17-5p, and hsa-miR-16-5p) and transcription factors (MYT1L, PIN1, and CSRNP3) have been discovered to improve our understanding of the alterations in proteins within the hippocampal tissues that lead to the progression of AD. These findings establish a path for possible treatments for AD to employ therapeutic strategies that specifically focus on the proteins or processes linked to the illness.

Causal relationships between delirium and Alzheimer's disease: a bidirectional two-sample Mendelian randomization study

BACKGROUND

Previous observational studies have reported that delirium has an association with an increased risk of Alzheimer's disease (AD), and that patients with AD have a higher risk of developing delirium. However, due to the limitations of observational study, it is challenging to confirm whether delirium has a causal effect on AD or reverse causation exists.

METHODS

A bidirectional two-sample Mendelian randomization (MR) was performed to investigate the relationship between delirium and AD. Summary statistics from genome-wide association studies of delirium and AD phenotypes were utilized. Inverse-variance weighted (IVW) method was used as the main analysis approach, and additional analyses were performed using MR Egger, weighted median, simple mode and weighted mode to ensure result accuracy. Heterogeneity and horizontal pleiotropy were assessed using Cochran's Q statistics and MR Egger intercept, separately.

RESULTS

The MR analyses showed that genetically predicted delirium was not associated with AD (IVW: odds ratio [OR] 0.98, 95% CI 0.91-1.05, P = 0.544; MR Egger: OR 0.98, 95% CI 0.83-1.15, P = 0.780; weighted median: OR 0.96, 95% CI 0.88-1.05, P = 0.323; simple mode: OR 0.91, 95% CI 0.80-1.04, P = 0.212; weighted mode: OR 0.93, 95% CI 0.83-1.05, P = 0.277). However, in the reverse direction, AD was associated with delirium (IVW: OR 1.32, 95% CI 1.13-1.54, P = 3.91E-04; MR Egger: OR 1.42, 95% CI 1.02-1.98, P = 5.60E-02; Weighted median: OR 1.39, 95% CI 1.18-1.63, P = 8.22E-05; Simple mode: OR 1.41, 95% CI 1.10-1.80, P = 1.41E-02; Weighted mode: OR 1.39, 95% CI 1.16-1.67, P = 3.23E-03).

CONCLUSION

Based on the results of our MR study, there is no bidirectional causality between delirium and AD, delirium is not associated with an increased risk of AD, while genetically predicted AD is a potential causal risk factor for delirium.