Cerebrospinal Fluid β-Amyloid and Tau Are Not Associated with Risk of Delirium: A Prospective Cohort Study in Older Adults with Hip Fracture

Associations between Alzheimer's disease biomarkers and postoperative delirium or cognitive dysfunction: A meta-analysis and trial sequential analysis of prospective clinical trials

BACKGROUND

The relationship between Alzheimer's disease biomarkers and postoperative complications, such as postoperative delirium (POD) and postoperative cognitive dysfunction (POCD), remains a subject of ongoing debate.

OBJECTIVE

This meta-analysis aimed to determine whether there is an association between perioperative Alzheimer's disease biomarkers and postoperative complications.

DESIGN

We conducted a meta-analysis of observational clinical studies that explored the correlation between Alzheimer's disease biomarkers and POD or POCD in patients who have undergone surgery, following PRISMA guidelines. The protocol was previously published (INPLASY: INPLASY202350001).

DATA SOURCES

A comprehensive search was conducted across PubMed, Embase, Web of Science, and Cochrane databases until March 2023.

ELIGIBILITY CRITERIA

Surgical patients aged at least 18 years, studies focusing on POD or POCD, research involving Alzheimer's disease biomarkers, including Aβ or tau in blood or cerebrospinal fluid (CSF), and availability of the full text.

RESULTS

Our meta-analysis included 15 studies: six focusing on POD and nine on POCD. The findings revealed a negative correlation between preoperative CSF β-amyloid 42 (Aβ42) levels and the onset of POD [mean difference -86.1, 95% confidence interval (CI), -114.15 to -58.05, I2 : 47%]; this association was strongly supported by trial sequential analysis (TSA). A similar negative correlation was discerned between preoperative CSF Aβ42 levels and the incidence of POCD (-165.01, 95% CI, -261.48 to -68.53, I2 : 95%). The TSA also provided robust evidence for this finding; however, the evidence remains insufficient to confirm a relationship between other Alzheimer's disease biomarkers [β-amyloid 40 (Aβ40), total tau (T-tau), phosphorylated tau (P-tau), and Aβ42/T-tau ratio] and POD or POCD.

CONCLUSION

The study results indicate a negative correlation between preoperative CSF Aβ42 levels and the occurrence of both POD and POCD. Future investigations are warranted to identify the predictive cutoff value of preoperative CSF Aβ42 for POD and POCD.

Presence of Preoperative Neurodegeneration Biofluid Markers in Patients with Postoperative Delirium

BACKGROUND

The pathophysiology of delirium is incompletely understood, including what molecular pathways are involved in brain vulnerability to delirium. This study examined whether preoperative plasma neurodegeneration markers were elevated in patients who subsequently developed postoperative delirium through a retrospective case-control study.

METHODS

Inclusion criteria were patients of 65 yr of age or older, undergoing elective noncardiac surgery with a hospital stay of 2 days or more. Concentrations of preoperative plasma P-Tau181, neurofilament light chain, amyloid β1-42 (Aβ42), and glial fibrillary acidic protein were measured with a digital immunoassay platform. The primary outcome was postoperative delirium measured by the Confusion Assessment Method. The study included propensity score matching by age and sex with nearest neighbor, such that each patient in the delirium group was matched by age and sex with a patient in the no-delirium group.

RESULTS

The initial cohort consists of 189 patients with no delirium and 102 patients who developed postoperative delirium. Of 291 patients aged 72.5 ± 5.8 yr, 50.5% were women, and 102 (35%) developed postoperative delirium. The final cohort in the analysis consisted of a no-delirium group (n = 102) and a delirium group (n = 102) matched by age and sex using the propensity score method. Of the four biomarkers assayed, the median value for neurofilament light chain was 32.05 pg/ml for the delirium group versus 23.7 pg/ml in the no-delirium group. The distribution of biomarker values significantly differed between the delirium and no-delirium groups (P = 0.02 by the Kolmogorov-Smirnov test) with the largest cumulative probability difference appearing at the biomarker value of 32.05 pg/ml.

CONCLUSIONS

These results suggest that patients who subsequently developed delirium are more likely to be experiencing clinically silent neurodegenerative changes before surgery, reflected by changes in plasma neurofilament light chain biomarker concentrations, which may identify individuals with a preoperative vulnerability to subsequent cognitive decline.

EDITOR’S PERSPECTIVE

Prospective analysis of plasma amyloid beta and postoperative delirium in the Interventions for Postoperative Delirium: Biomarker-3 study

BACKGROUND

The effect of postoperative delirium on the amyloid cascade of Alzheimer's dementia is poorly understood. Using early postoperative plasma biomarkers, we explored whether surgery and delirium are associated with changes in amyloid pathways.

METHODS

We analysed data from 100 participants in the Interventions for Postoperative Delirium: Biomarker-3 (IPOD-B3) cohort study in the USA (NCT03124303 and NCT01980511), which recruited participants aged >65 yr undergoing non-intracranial surgery. We assessed the relationship between the change in plasma amyloid beta ratio (AβR; Aβ42:Aβ40) and delirium incidence (defined by the 3-Minute Diagnostic Confusion Assessment Method) and severity (quantified by the Delirium Rating Scale-Revised-98, the study's primary outcome). We also tested the relationship between plasma amyloid beta and intraoperative variables.

RESULTS

Across all participants, the plasma AβR increased from the preoperative period to postoperative Day 1 (Wilcoxon P<0.001). However, this increase was not associated with delirium incidence (Wilcoxon P=0.22) or peak severity after adjusting for confounders (log[incidence rate ratio]=0.43; P=0.14). Postoperative Day 1 change in plasma AβR was not associated with postoperative Day 1 change in plasma tau, neurofilament light, or inflammatory markers (interleukin [IL]-1β, IL-1Ra, IL-2, IL-4, IL-6, IL-8, IL-10, and IL-12), or with operative time or low intraoperative arterial pressure.

CONCLUSIONS

Perioperative changes in plasma amyloid do not appear to be associated with postoperative delirium. Our findings do not support associations of dynamic changes in amyloid with postoperative delirium.

CLINICAL TRIAL REGISTRATION

.NCT03124303 and NCT01980511.

Relationship between postoperative biomarkers of neuronal injury and postoperative cognitive dysfunction: A meta-analysis

Early biomarkers are needed to identify patients at risk of developing postoperative cognitive dysfunction (POCD). Our objective was to determine neuronal injury-related biomarkers with predictive values for this condition. Six biomarkers (S100β, neuron-specific enolase [NSE], amyloid beta [Aβ], tau, neurofilament light chain, and glial fibrillary acidic protein) were evaluated. According to the first postoperative sampling time, observational studies showed that S100β was significantly higher in patients with POCD than in those without POCD (standardized mean difference [SMD]: 6.92, 95% confidence interval [CI]: 4.44-9.41). The randomized controlled trial (RCT) showed that S100β (SMD: 37.31, 95% CI: 30.97-43.64) and NSE (SMD: 3.50, 95% CI: 2.71-4.28) in the POCD group were significantly higher than in the non-POCD group. The pooled data of observational studies by postoperative sampling time showed significantly higher levels of the following biomarkers in the POCD groups than in the control groups: S100β levels at 1 hour (SMD: 1.35, 95% CI: 0.07-2.64), 2 days (SMD: 27.97, 95% CI: 25.01-30.94), and 9 days (SMD: 6.41, 95% CI: 5.64-7.19); NSE levels at 1 hour (SMD: 0.92, 95% CI: 0.25-1.60), 6 hours (SMD: 0.79, 95% CI: 0.12-1.45), and 24 hours (SMD: 0.84, 95% CI: 0.38-1.29); and Aβ levels at 24 hours (SMD: 2.30, 95% CI: 1.54-3.06), 2 days (SMD: 2.30, 95% CI: 1.83-2.78), and 9 days (SMD: 2.76, 95% CI: 2.25-3.26). The pooled data of the RCT showed that the following biomarkers were significantly higher in POCD patients than in non-POCD patients: S100β levels at 2 days (SMD: 37.31, 95% CI: 30.97-43.64) and 9 days (SMD: 126.37, 95% CI: 104.97-147.76) and NSE levels at 2 days (SMD: 3.50, 95% CI: 2.71-4.28) and 9 days (SMD: 8.53, 95% CI: 7.00-10.06). High postoperative levels of S100β, NSE, and Aβ may predict POCD. The relationship between these biomarkers and POCD may be affected by sampling time.

The potential link between obstructive sleep apnea and postoperative neurocognitive disorders: current knowledge and possible mechanisms

PURPOSE

This narrative review examines the current evidence on whether obstructive sleep apnea (OSA) is associated with postoperative delirium (POD) and postoperative cognitive dysfunction (POCD). The mechanisms that could predispose OSA patients to these disorders are also explored.

SOURCE

Relevant literature was identified by searching for pertinent terms in Medline®, Pubmed, ScopusTM, and Google scholar databases. Case reports, abstracts, review articles, original research articles, and meta-analyses were reviewed. The bibliographies of retrieved sources were also searched to identify relevant papers.

PRINCIPAL FINDINGS

Seven studies have investigated the association between OSA and POD, with mixed results. No studies have examined the potential link between OSA and POCD. If these relationships exist, they could be mediated by several mechanisms, including increased neuroinflammation, blood-brain barrier breakdown, cerebrovascular disease, Alzheimer's disease neuropathology, disrupted cerebral autoregulation, sleep disruption, sympathovagal imbalance, and/or disrupted brain bioenergetics.

CONCLUSION

There is very limited evidence that OSA plays a role in postoperative neurocognitive disorders because few studies have been conducted in the perioperative setting. Additional perioperative prospective observational cohort studies and randomized controlled trials of sleep apnea treatment are needed. These investigations should also assess potential underlying mechanisms that could predispose patients with OSA to postoperative neurocognitive disorders. This review highlights the need for more research to improve postoperative neurocognitive outcomes for patients with OSA.

The inter-relationship between delirium and dementia: the importance of delirium prevention

Delirium and dementia are two frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship. Delirium is an acute confusional state characterized by inattention, cognitive dysfunction and an altered level of consciousness, whereas dementia is an insidious, chronic and progressive loss of a previously acquired cognitive ability. People with dementia have a higher risk of developing delirium than the general population, and the occurrence of delirium is an independent risk factor for subsequent development of dementia. Furthermore, delirium in individuals with dementia can accelerate the trajectory of the underlying cognitive decline. Delirium prevention strategies can reduce the incidence of delirium and associated adverse outcomes, including falls and functional decline. Therefore, delirium might represent a modifiable risk factor for dementia, and interventions that prevent or minimize delirium might also reduce or prevent long-term cognitive impairment. Additionally, understanding the pathophysiology of delirium and the connection between delirium and dementia might ultimately lead to additional treatments for both conditions. In this Review, we explore mechanisms that might be common to both delirium and dementia by reviewing evidence on shared biomarkers, and we discuss the importance of delirium recognition and prevention in people with dementia.

In this Review, Fong and Inouye explore mechanisms that might be common to both delirium and dementia. They present delirium as a possible modifiable risk factor for dementia and discuss the importance of delirium prevention strategies in reducing this risk.

Delirium and dementia are frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship.

Delirium prevention strategies have been shown to reduce not only the incidence of delirium but also the incidence of adverse outcomes associated with delirium such as falls and functional decline.

Adverse outcomes associated with delirium, such as the onset of dementia symptoms in individuals with preclinical dementia, and/or the acceleration of cognitive decline in individuals with dementia might also be delayed by the implementation of delirium prevention strategies.

Evidence regarding the association of systemic inflammatory and neuroinflammatory biomarkers with delirium is variable, possibly as a result of co-occurring dementia pathology or disruption of the blood–brain barrier.

Alzheimer disease pathology, even prior to the onset of symptoms, might have an effect on delirium risk, with potential mechanisms including neuroinflammation and gene–protein interactions with the APOE ε4 allele.

Novel strategies, including proteomics, multi-omics, neuroimaging, transcranial magnetic stimulation and EEG, are beginning to reveal how changes in cerebral blood flow, spectral power and connectivity can be associated with delirium; further work is needed to expand these findings to patients with delirium superimposed upon dementia.

Hospital-associated deconditioning: Not only physical, but also cognitive

INTRODUCTION

Hospital-associated deconditioning (HAD) or post-hospital syndrome is well recognized as reduced functional performance after an acute hospitalization. Recommendations for the management of HAD are still lacking, partly due to a poor understanding of the underlying processes. We aimed to review existing data on risk factors, pathophysiology, measurement tools, and potential interventions.

MATERIALS AND METHODS

We conducted a systematic review from bibliographical databases in English, Spanish and French with keywords such as 'post-hospitalization syndrome' or 'deconditioning'. We selected studies that included people aged 60 years or older. Three researchers independently selected articles and assessed their quality.

RESULTS

From 4421 articles initially retrieved, we included 94 studies. Most were related to risk factors, trajectories and measures, and focused on the physical aspects of deconditioning. Risk factors for HAD included age, nutritional status, mobility, and pre-admission functional status, but also cognitive impairment and depression. Regarding interventions, almost all studies were devoted to physical rehabilitation and environmental modifications. Only one study focused on cognitive stimulation.

DISCUSSION

In the last decade, studies on HAD have mostly focused on the physical domain. However, neurological changes may also play a role in the pathophysiology of HAD. Beyond physical interventions, cognitive rehabilitation and neurological interventions should also be evaluated to improve deconditioning prevention and treatment in the hospital setting.

Postoperative delirium and its relationship with biomarkers for dementia: a meta-analysis

OBJECTIVES

This study seeks to identify Alzheimer's and related dementias (ADRD) biomarkers associated with postoperative delirium (POD) via meta-analysis.

DESIGN

A comprehensive search was conducted. Studies met the following inclusion criteria: >18 years of age, identified POD with standardized assessment, and biomarker measured in the AT(N)-X (A = amyloid, T = tau, (N)=neurodegeneration, X-Other) framework. Exclusion criteria: focus on prediction of delirium, delirium superimposed on dementia, other neurologic or psychiatric disorders, or terminal delirium. Reviewers extracted and synthesized data for the meta-analysis.

SETTING

Meta-analysis.

PARTICIPANTS

Patients with POD.

MEASUREMENTS

Primary outcome: association between POD and ATN-X biomarkers. Secondary outcomes involved sample heterogeneity.

RESULTS

28 studies were included in this meta-analysis. Studies focused on inflammatory and neuronal injury biomarkers; there were an insufficient number of studies for amyloid and tau biomarker analysis. Two inflammatory biomarkers (IL-6, and CRP) showed a significant relationship with POD (IL-6 n = 10, standardized mean difference (SMD): 0.53, 95% CI: 0.36-0.70; CRP n = 14, SMD: 0.53, 95% CI: 0.33-0.74). Two neuronal injury biomarkers (blood-based S100B and NfL) were positively associated with POD (S100B n = 5, SMD: 0.40, 95% CI: 0.11-0.69; NFL n = 2, SMD: 0.93, 95% CI: 0.28-1.57). Of note, many analyses were impacted by significant study heterogeneity.

CONCLUSIONS

This meta-analysis identified an association between certain inflammatory and neuronal injury biomarkers and POD. Future studies will need to corroborate these relationships and include amyloid and tau biomarkers in order to better understand the relationship between POD and ADRD.

Association of Depressive Symptoms With Postoperative Delirium and CSF Biomarkers for Alzheimer's Disease Among Hip Fracture Patients

OBJECTIVES

While there is growing evidence of an association between depressive symptoms and postoperative delirium, the underlying pathophysiological mechanisms remain unknown. The goal of this study was to explore the association between depression and postoperative delirium in hip fracture patients, and to examine Alzheimer's disease (AD) pathology as a potential underlying mechanism linking depressive symptoms and delirium.

METHODS

Patients 65 years old or older (N = 199) who were undergoing hip fracture repair and enrolled in the study "A Strategy to Reduce the Incidence of Postoperative Delirium in Elderly Patients" completed the 15-item Geriatric Depression Scale (GDS-15) preoperatively. Cerebrospinal fluid (CSF) was obtained during spinal anesthesia and assayed for amyloid-beta (Aβ) 40, 42, total tau (t-tau), and phosphorylated tau (p-tau)181.

RESULTS

For every one point increase in GDS-15, there was a 13% increase in odds of postoperative delirium, adjusted for baseline cognition (MMSE), age, sex, race, education and CSF AD biomarkers (OR = 1.13, 95%CI = 1.02-1.25). Both CSF Aβ42/t-tau (β = -1.52, 95%CI = -2.1 to -0.05) and Aβ42/p-tau181 (β = -0.29, 95%CI = -0.48 to -0.09) were inversely associated with higher GDS-15 scores, where lower ratios indicate greater AD pathology. In an analysis to identify the strongest predictors of delirium out of 18 variables, GDS-15 had the highest classification accuracy for postoperative delirium and was a stronger predictor of delirium than both cognition and AD biomarkers.

CONCLUSIONS

In older adults undergoing hip fracture repair, depressive symptoms were associated with underlying AD pathology and postoperative delirium. Mild baseline depressive symptoms were the strongest predictor of postoperative delirium, and may represent a dementia prodrome.

Association of CSF Alzheimer's disease biomarkers with postoperative delirium in older adults

INTRODUCTION

The interaction between delirium and dementia is complex. We examined if Alzheimer's disease (AD) biomarkers in patients without clinical dementia are associated with increased risk of postoperative delirium, and whether AD biomarkers demonstrate a graded association with delirium severity.

METHODS

Participants (n = 59) were free of clinical dementia, age ≥ 70 years, and scheduled for elective total knee or hip arthroplasties. Cerebrospinal fluid (CSF) was collected at the time of induction for spinal anesthesia. CSF AD biomarkers were measured by enzyme-linked immunosorbent assay (ELISA) (ADX/Euroimmun); cut points for amyloid, tau, and neurodegeneration (ATN) biomarker status were A = amyloid beta (Aβ)42 <175 pg/mL or Aβ42/40 ratio <0.07; T = p-tau >80 pg/mL; and N = t-tau >700 pg/mL. Confusion Assessment Method (CAM) and CAM-Severity (CAM-S) were rated daily post-operatively for delirium and delirium severity, respectively.

RESULTS

Aβ42, tau, and p-tau mean pg/mL (SD) were 361.5 (326.1), 618.3 (237.1), and 97.1 (66.1), respectively, for those with delirium, and 550.4 (291.6), 518.3 (213.5), and 54.6 (34.5), respectively, for those without delirium. Thirteen participants (22%) were ATN positive. Delirium severity by peak CAM-S [mean difference (95% confidence interval)] was 1.48 points higher (0.29-2.67), P = 0.02 among the ATN positive. Delirium in the ATN-positive group trended toward but did not reach statistical significance (23% vs. 7%, p = 0.10). Peak CAM-S [mean (SD)] in the delirium group was 7 (2.8) compared to no delirium group 2.5 (1.3), but when groups were further classified by ATN status, an incremental effect on delirium severity was observed, such that patients who were both ATN and delirium negative had the lowest mean (SD) peak CAM-S scores of 2.5 (1.3) points, whereas those who were ATN and delirium positive had CAM-S scores of 8.7 (2.3) points; other groups (either ATN or delirium positive) had intermediate CAM-S scores.

DISCUSSION

The presence of AD biomarkers adds important information in predicting delirium severity. Future studies are needed to confirm this relationship and to better understand the role of AD biomarkers, even in pre-clinical phase, in delirium.

Neurovascular and immune mechanisms that regulate postoperative delirium superimposed on dementia

Objective

The present work evaluates the relationship between postoperative immune and neurovascular changes and the pathogenesis of surgery‐induced delirium superimposed on dementia.

Background and rationale

Postoperative delirium is a common complication in many older adults and in patients with dementia including Alzheimer's disease (AD). The course of delirium can be particularly debilitating, while its pathophysiology remains poorly defined.

Historical evolution

As of 2019, an estimated 5.8 million people of all ages have been diagnosed with AD, 97% of whom are >65 years of age. Each year, many of these patients require surgery. However, anesthesia and surgery can increase the risk for further cognitive decline. Surgery triggers neuroinflammation both in animal models and in humans, and a failure to resolve this inflammatory state may contribute to perioperative neurocognitive disorders as well as neurodegenerative pathology.

Updated hypothesis

We propose an immunovascular hypothesis whereby dysregulated innate immunity negatively affects the blood‐brain interface, which triggers delirium and thereby exacerbates AD neuropathology.

Early experimental data

We have developed a translational model to study delirium superimposed on dementia in APPSwDI/mNos2^−/− AD mice (CVN‐AD) after orthopedic surgery. At 12 months of age, CVN‐AD showed distinct neuroimmune and vascular impairments after surgery, including acute microgliosis and amyloid‐β deposition. These changes correlated with attention deficits, a core feature of delirium‐like behavior.

Future experiments and validation studies

Future research should determine the extent to which prevention of surgery‐induced microgliosis and/or neurovascular unit dysfunction can prevent or ameliorate postoperative memory and attention deficits in animal models. Translational human studies should evaluate perioperative indices of innate immunity and neurovascular integrity and assess their potential link to perioperative neurocognitive disorders.

Major challenges for the hypothesis

Understanding the complex relationships between delirium and dementia will require mechanistic studies aimed at evaluating the role of postoperative neuroinflammation and blood‐brain barrier changes in the setting of pre‐existing neurodegenerative and/or aging‐related pathology.

Linkage to other major theories

Non‐resolving inflammation with vascular disease that leads to cognitive impairments and dementia is increasingly important in risk stratification for AD in the aging population. The interdependence of these factors with surgery‐induced neuroinflammation and cognitive dysfunction is also becoming apparent, providing a strong platform for assessing the relationship between postoperative delirium and longer term cognitive dysfunction in older adults.

CSF Beta-amyloid 1-42 Concentration Predicts Delirium Following Elective Arthroplasty Surgery in an Observational Cohort Study

OBJECTIVE

To test the hypothesis that APOE ε4 status and cerebrospinal fluid (CSF) Aβ42, T-tau and P-tau would independently predict the risk of postoperative delirium.

BACKGROUND

Delirium following surgery is common and associated with adverse outcomes. Age and cognitive impairment are consistent risk factors for postoperative delirium.

METHODS

This observational cohort study recruited 282 participants aged 65 years or older, without a diagnosis of dementia, admitted for primary elective hip or knee arthroplasty. Cognitive tests were undertaken preoperatively, blood and CSF were sampled at the time of spinal anesthesia, and participants were assessed daily postoperatively for delirium.

RESULTS

Increasing age (P = 0.04), preoperative comorbidity (P = 0.03), type of surgery (P = 0.05), intravenous opioid usage (P = 0.04), and low CSF Aβ42 (P < 0.01) were independent predictors of postoperative delirium.

CONCLUSIONS

This study is the first to show an independent association between CSF Aβ42 and delirium incidence in an elective surgical population, suggesting that postoperative delirium may indicate incipient Alzheimer disease.

The trajectory of C-reactive protein serum levels in older hip fracture patients with postoperative delirium

OBJECTIVES

Important precipitating risk factors for delirium such as infections, vascular disorders, and surgery are accompanied by a systemic inflammatory response. Systemic inflammatory mediators can induce delirium in susceptible individuals. Little is known about the trajectory of systemic inflammatory markers and their role in the development and outcome of delirium.

METHODS

This is a prospective cohort study of older patients undergoing acute surgery for hip fracture. Baseline characteristics were assessed preoperatively. During hospital admission, presence of delirium was assessed daily according to the Confusion Assessment Method criteria. This study compared the trajectory of serum levels of the C-reactive protein (CRP) between people with and without postoperative delirium. Blood samples were taken at baseline and at postoperative day 1 through postoperative day 5.

RESULTS

Forty-one out of 121 patients developed postoperative delirium after hip fracture surgery. Longitudinal analysis of the trajectory of serum CRP levels using the Generalized Estimating Equations (GEE) method identified that higher CRP levels were associated with postoperative delirium. CRP levels were higher from postoperative day 2 through postoperative day 5. No significant differences in serum CRP levels were found when we compared patients with short (1-2 days) and more prolonged delirium (3 days or more).

CONCLUSIONS

Delirium is associated with an increased systemic inflammatory response, and our results suggest that CRP plays a role in the underlying (inflammatory-vascular) pathological pathway of postoperative delirium.

Effects of an abnormal mini-mental state examination score on postoperative outcomes in geriatric surgical patients: a meta-analysis

Background

Perioperative cognitive impairment (CI) following surgeries is prevalent in geriatric surgical population aged 60 and older. This meta-analysis was designed to investigate whether the Mini-Mental State Examination (MMSE) has prognostic value on adverse outcomes in aged surgical patients.

Methods

PubMed, Cochrane, Embase and Medline through the Ovid were searched. Meta-analyses were carried out for CI versus non-cognitive impairment (NCI). Quality of evidence was assessed by the GRADE approach.

Results

One randomized controlled trial, two retrospective cohort trials, and 18 prospective cohort trials were included in the meta-analysis. Perioperative diagnosis of CI by the MMSE had higher rates of patients suffering from postoperative delirium (POD) [odd ratio (OR) 5.02, 95% confidence interval (CI) 3.27, 7.71, P < 0.00001], in-hospital mortality (OR 7.51, 95% CI 2.17, 26.02, P = 0.001), mortality within 1 year (OR 2.53, 95% CI 1.95,3.29, P < 0.00001). Postoperative CI patients had no extended length of stay in orthopedic [standardized mean difference (SMD) -0.10, 95% CI -0.20, 0.17, P = 0.91)] nor rehabilitation wards ((SMD, 0.04; 95% CI, − 0.23 to 0.31; P = 0.78).

Conclusion

Older patients with perioperative CI were more likely to suffer from POD and mortality. The MMSE showed certain value on risk stratification and prognosis evaluation in geriatric surgical population.

Trial registration

PROSPERO CRD42018108739.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0735-5) contains supplementary material, which is available to authorized users.

Pre-operative biomarkers and imaging tests as predictors of post-operative delirium in non-cardiac surgical patients: a systematic review

Background

Post-operative delirium (POD) is a common post-operative complication in elderly individuals and imposes a significant health and financial burden. Identifying predictive biomarkers may help understand the pathophysiology of POD. Our objective is to summarize the evidence of pre-operative biomarkers and imaging tests to predict POD in patients undergoing non-cardiac surgery.

Methods

A systematic search of English language articles in MEDLINE, EMBASE, Cochrane Database, PsychINFO, PubMed and ClinicalTrials. Gov up to January 2018 was performed. Studies that used biomarkers or imaging tests to predict POD and a validated POD assessment tool were included. Animal studies, paediatric, cardiac and intracranial surgery were excluded. Risk of bias was assessed using the Quality In Prognosis Study tool.

Results

Thirty-four prospective cohort studies involving 4424 patients were included. Nineteen studies described serum tests [Interleukin-6, Insulin-like Growth Factor 1, C-Reactive Protein (CRP), cholinesterases, apolipoprotein-E genotype, leptin, hypovitaminosis, hypoalbuminaemia, gamma-amino butyric acid], 10 described cerebral-spinal fluid tests (monoamine precursor, melatonin, acute phase proteins, S100B and neurofibrillary tangles), and 5 described imaging tests. Two studies had high risk of bias due to unclear outcome measurement and study participation. CRP was significantly associated with POD in 5 studies. Other biomarkers were either examined by only a single study or two or more studies with conflicting results.

Conclusion

CRP is the most promising biomarker associated with POD. However, we are still in the early stages in identifying biomarkers and imaging tests that may further understanding of the pathophysiology of POD.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0693-y) contains supplementary material, which is available to authorized users.

Debate article: Antipsychotic medications are clinically useful for the treatment of delirium

Prescribing of antipsychotic medications for patients with delirium remains controversial. Concerns exist that these vulnerable and frail patients may be prescribed antipsychotics inappropriately as a substitute for non-pharmacological approaches when identifiable causes are not found or they challenge ward processes. Moreover, recent evidence suggests that antipsychotics may cause more harm than good in the palliative care patient group with delirium. On the other hand, guidelines in the United Kingdom and the Netherlands support prescribing of antipsychotics in certain circumstances, and a large European survey has revealed that antipsychotics tend to be prescribed first line for hyperactive delirium. Never before, therefore, is there a greater need to examine whether indeed these medications are clinically useful for the treatment of delirium. With this in mind, evidence-based arguments for and against prescribing antipsychotics for the treatment of delirium are presented in this debate article. The paper concludes with a moderation piece to help guide clinical practice.

CSF biomarkers in delirium: a systematic review

OBJECTIVE

In recent years, there has been a blossoming of studies examining cerebrospinal fluid (CSF) as a method of studying the pathophysiology of delirium. We systematically reviewed the literature for CSF studies in delirium and provide here a summary of the implications for our understanding of delirium pathophysiology. We also summarise the methods used for CSF analysis and discuss challenges and implications for future studies.

METHODS

In this systematic review, we screened MEDLINE, EMBASE, PsycINFO, Web of Science, PubMed and the Cochrane Library for articles on CSF biomarkers in delirium, published on 3 September 2016. Studies were required to use Diagnostic and Statistical Manual of Mental Disorders or International Classification of Diseases criteria for delirium or a validated tool. We excluded case reports. There were no other restrictions on study type.

RESULTS

We identified 3280 articles from our initial search, and 22 articles were included in this review. All studies were prospective, including over 400 patients with delirium and 700 controls. More than 70 different biomarkers were studied. Studies could not be compared with each other for meta-analysis because of their heterogeneity and varied widely in their risk of bias and quality assessments.

CONCLUSIONS

The 22 studies identified in this review reveal a small but growing literature, in which many of the important hypotheses in delirium pathogenesis have been examined, but from which few firm conclusions can currently be drawn. Nevertheless, the overall interpretation of the literature supports the vulnerable brain concept, that is, that biomarker evidence of, for example, Alzheimer's disease pathology and/or neuroinflammation, is associated with delirium.

Delirium symptoms are associated with decline in cognitive function between ages 53 and 69 years: Findings from a British birth cohort study

INTRODUCTION

Few population studies have investigated whether longitudinal decline after delirium in mid-to-late life might affect specific cognitive domains.

METHODS

Participants from a birth cohort completing assessments of search speed, verbal memory, and the Addenbrooke's Cognitive Examination at age 69 were asked about delirium symptoms between ages 60 and 69 years. Linear regression models estimated associations between delirium symptoms and cognitive outcomes.

RESULTS

Period prevalence of delirium between 60 and 69 years was 4% (95% confidence interval 3.2%-4.9%). Self-reported symptoms of delirium over the seventh decade were associated with worse scores in the Addenbrooke's Cognitive Examination (-1.7 points; 95% confidence interval -3.2, -0.1; P = .04). In association with delirium symptoms, verbal memory scores were initially lower, with subsequent decline in search speed by the age of 69 years. These effects were independent of other Alzheimer's risk factors.

DISCUSSION

Delirium symptoms may be common even at relatively younger ages, and their presence may herald cognitive decline, particularly in search speed, over this time period.

Alzheimer's-related cortical atrophy is associated with postoperative delirium severity in persons without dementia

Patients with dementia due to Alzheimer's disease (AD) have increased risk of developing delirium. This study investigated the relationship between a magnetic resonance imaging (MRI)-derived biomarker associated with preclinical AD and postoperative delirium. Participants were older adults (≥70 years) without dementia who underwent preoperative MRI and elective surgery. Delirium incidence and severity were evaluated daily during hospitalization. Cortical thickness was averaged across a published set of a priori brain regions to derive a measure known as the "AD signature." Logistic and linear regression was used, respectively, to test whether the AD signature was associated with delirium incidence in the entire sample (N = 145) or with the severity of delirium among those who developed delirium (N = 32). Thinner cortex in the AD signature did not predict incidence of delirium (odds ratio = 1.15, p = 0.38) but was associated with greater delirium severity among those who developed delirium (b = -1.2, p = 0.014). These results suggest that thinner cortices, perhaps reflecting underlying neurodegeneration due to preclinical AD, may serve as a vulnerability factor that increases severity once delirium occurs.

Risk factors of delirium in elderly patients with hip fracture

Background: Delirium is a leading cause of death and disability in the elderly with hip fracture. Identifying reliable risk factors for delirium is critical to support optimal outcomes for prevention and reducing delirium.

Objective: To quantify the reported factors associated to delirium for patients with hip fracture.

Methods: Electronic databases were searched (including Medline, Pub Med, CINAHL, EMBASE, Evidence Based Medicine Reviews, Cochrane Review, Web of Science, and PsycINFO) to identify all studies, published in English language that evaluated the risk factors of delirium hospitalized people with hip fracture. Two reviewers independently assessed methodology quality and extracted relevant data. The data from the included studies were summarized, and pooled estimates were calculated for 12 risk factors.

Results: Thirty-seven studies were included in the review and 25 in the meta-analysis. The incidence of delirium was 32.4% (95% confidence interval [CI] = 25.9%-39.5%). Six predisposing and four precipitating factors predicted delirium among older patients with hip fracture confirmed. The predisposing factors included advanced age (ES = 1.06, 95% CI = 1.03-1.09), male sex (ES = 1.34, 95% CI = 1.08-1.68), impairment of cognition (ES = 2.91, 95% CI = 1.91-4.42), and function (ES = 1.75, 95% CI = 1.39-2.2), comorbidity (ES = 1.59, 95% CI = 1.30-1.96), and health problems (ES = 2.64, 95% CI = 2.04-3.42). Precipitating factors were hypo- or hypernatremia (ES = 1.73, 95% CI = 1.14-2.64), depression (ES = 4.07, 95% CI = 1.95-8.49), more than three prescribed drugs (ES = 1.28, 95% CI = 1.10-1.49), and drugs including opioids (ES = 2.13, 95% CI = 1.42-3.18) and anticholinergic agents (ES = 2.10, 95% CI = 1.60-2.75).

Conclusion: This meta-analysis result provides evidence that these risk factors have a significant impact on delirium in elders with hip fracture during hospitalization. Developing formal screening, and effective preventive and management strategies for delirium is important.

Neuroinflammatory challenges compromise neuronal function in the aging brain: Postoperative cognitive delirium and Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that targets memory and cognition, and is the most common form of dementia among the elderly. Although AD itself has been extensively studied, very little is known about early-stage preclinical events and/or mechanisms that may underlie AD pathogenesis. Since the majority of AD cases are sporadic in nature, advancing age remains the greatest known risk factor for AD. However, additional environmental and epigenetic factors are thought to accompany increasing age to play a significant role in the pathogenesis of AD. Postoperative cognitive delirium (POD) is a behavioral syndrome that primarily occurs in elderly patients following a surgical procedure or injury and is characterized by disruptions in cognition. Individuals that experience POD are at an increased risk for developing dementia and AD compared to normal aging individuals. One way in which cognitive function is affected in cases of POD is through activation of the inflammatory cascade following surgery or injury. There is compelling evidence that immune challenges (surgery and/or injury) associated with POD trigger the release of pro-inflammatory cytokines into both the periphery and central nervous system. Thus, it is possible that cognitive impairments following an inflammatory episode may lead to more severe forms of dementia and AD pathogenesis. Here we will discuss the inflammation associated with POD, and highlight the advantages of using POD as a model to study inflammation-evoked cognitive impairment. We will explore the possibility that advancing age and immune challenges may provide mechanistic evidence correlating early life POD with AD. We will review and propose neural mechanisms by which cognitive impairments occur in cases of POD, and discuss how POD may augment the onset of AD.

Biomarkers of Brain Damage and Postoperative Cognitive Disorders in Orthopedic Patients: An Update

The incidence of postoperative cognitive dysfunction (POCD) in orthopedic patients varies from 16% to 45%, although it can be as high as 72%. As a consequence, the hospitalization time of patients who developed POCD was longer, the outcome and quality of life were worsened, and prolonged medical and social assistance were necessary. In this review the short description of such biomarkers of brain damage as the S100B protein, NSE, GFAP, Tau protein, metalloproteinases, ubiquitin C terminal hydrolase, microtubule-associated protein, myelin basic protein, α-II spectrin breakdown products, and microRNA was made. The role of thromboembolic material in the development of cognitive decline was also discussed. Special attention was paid to optimization of surgical and anesthetic procedures in the prevention of postoperative cognitive decline.

The interface between delirium and dementia in elderly adults

Delirium and dementia are two of the most common causes of cognitive impairment in older populations, yet their interrelation remains poorly understood. Previous studies have shown that dementia is the leading risk factor for delirium and that delirium is an independent risk factor for subsequent development of dementia. However, a major area of controversy is whether delirium is simply a marker of vulnerability to dementia, whether the effect of delirium is solely related to its precipitating factors, or whether delirium itself can cause permanent neuronal damage and lead to dementia. Ultimately, all of these hypotheses are likely to be true. Emerging evidence from epidemiological, clinicopathological, neuroimaging, biomarker, and experimental studies lends support to a strong relation between delirium and dementia, and to both shared and distinct pathological mechanisms. New preventive and therapeutic approaches that target delirium might offer a sought-after opportunity for early intervention, preservation of cognitive reserve, and prevention of irreversible cognitive decline in ageing.

Delirium and dementia with Lewy bodies: distinct diagnoses or part of the same spectrum?

Dementia with Lewy bodies (DLB) is recognised as the second most common form of dementia in older people. Delirium is a condition of acute brain dysfunction for which a pre-existing diagnosis of dementia is a risk factor. Conversely delirium is associated with an increased risk of developing dementia. The reasons for this bidirectional relationship are not well understood. Our aim was to review possible similarities in the clinical presentation and pathophysiology between delirium and DLB, and explore possible links between these diagnoses. A systematic search using Medline, Embase and Psychinfo was performed. References were scanned for relevant articles, supplemented by articles identified from reference lists and those known to the authors. 94 articles were selected for inclusion in the review. Delirium and DLB share a number of clinical similarities, including global impairment of cognition, fluctuations in attention and perceptual abnormalities. Delirium is a frequent presenting feature of DLB. In terms of pathophysiological mechanisms, cholinergic dysfunction and genetics may provide a common link. Neuroimaging studies suggest a brain vulnerability in delirium which may also occur in dementia. The basal ganglia, which play a key role in DLB, have also been implicated in delirium. The role of Cerebrospinal fluid (CSF) and serum biomarkers for both diagnoses is an interesting area although some results are conflicting and further work in this area is needed. Delirium and DLB share a number of features and we hypothesise that delirium may, in some cases, represent early or 'prodromal' DLB. Further research is needed to test the novel hypothesis that delirium may be an early marker for future DLB, which would aid early diagnosis of DLB and identify those at high risk.

Preoperative cerebrospinal fluid β-Amyloid/Tau ratio and postoperative delirium

Objective

The neuropathogenesis of postoperative delirium remains unknown. Low cerebrospinal fluid (CSF) β-amyloid protein (Aβ) and high CSF Tau levels are associated with Alzheimer's disease. We, therefore, assessed whether lower preoperative CSF Aβ/Tau ratio was associated with higher incidence and greater severity of postoperative delirium.

Methods

One hundred and fifty-three participants (71 ± 5 years, 53% men) who had total hip/knee replacement under spinal anesthesia were enrolled. CSF was obtained during initiation of spinal anesthesia. The incidence and severity of postoperative delirium were determined by Confusion Assessment Method (CAM) and Memorial Delirium Assessment Scale (MDAS) on postoperative day 1 and 2. Aβ40, Aβ42, and Tau levels in the CSF were measured by enzyme-linked immunosorbent assay. The relationships among these variables were determined, adjusting for age and gender.

Results

Participants in the lowest quartile of preoperative CSF Aβ40/Tau and Aβ42/Tau ratio had higher incidence (32% vs. 17%, P = 0.0482) and greater symptom severity of postoperative delirium (Aβ40/Tau ratio: 4 vs. 3, P = 0.034; Aβ42/Tau ratio: 4 vs. 3, P = 0.062, the median of the highest MDAS score) as compared to the combination of the rest of the quartiles. The preoperative CSF Aβ40/Tau or Aβ42/Tau ratio was inversely associated with MDAS score (Aβ40/Tau ratio: −0.12 ± 0.05, P = 0.014, adj. −0.12 ± 0.05, P = 0.018; Aβ42/Tau ratio: −0.65 ± 0.26, P = 0.013, adj. −0.62 ± 0.27, P = 0.022).

Interpretation

Lower CSF Aβ/Tau ratio could be associated with postoperative delirium, pending confirmation of our preliminary results in further studies. These findings suggest potential roles of Aβ and/or Tau in postoperative delirium neuropathogenesis.

Preoperative cerebrospinal fluid cytokine levels and the risk of postoperative delirium in elderly hip fracture patients

Background

Aging and neurodegenerative disease predispose to delirium and are both associated with increased activity of the innate immune system resulting in an imbalance between pro- and anti-inflammatory mediators in the brain. We examined whether hip fracture patients who develop postoperative delirium have altered levels of inflammatory mediators in cerebrospinal fluid (CSF) prior to surgery.

Methods

Patients were 75 years and older and admitted for surgical repair of an acute hip fracture. CSF samples were collected preoperatively. In an exploratory study, we measured 42 cytokines and chemokines by multiplex analysis. We compared CSF levels between patients with and without postoperative delirium and examined the association between CSF cytokine levels and delirium severity. Delirium was diagnosed with the Confusion Assessment Method; severity of delirium was measured with the Delirium Rating Scale Revised-98. Mann–Whitney U tests or Student t-tests were used for between-group comparisons and the Spearman correlation coefficient was used for correlation analyses.

Results

Sixty-one patients were included, of whom 23 patients (37.7%) developed postsurgical delirium. Concentrations of Fms-like tyrosine kinase-3 (P=0.021), Interleukin-1 receptor antagonist (P=0.032) and Interleukin-6 (P=0.005) were significantly lower in patients who developed delirium postoperatively.

Conclusions

Our findings fit the hypothesis that delirium after surgery results from a dysfunctional neuroinflammatory response: stressing the role of reduced levels of anti-inflammatory mediators in this process.

Trial registration

The Effect of Taurine on Morbidity and Mortality in the Elderly Hip Fracture Patient.

Registration number: NCT00497978. Local ethical protocol number: NL16222.094.07.

Delirium motor subtypes in elderly hip fracture patients: risk factors, outcomes and longitudinal stability

OBJECTIVE

Delirium is often accompanied by changes in motor activity but the longitudinal expression of these features and etiological and prognostic significance of clinical subtypes defined by motor activity is unclear.

METHODS

This is a prospective cohort study of elderly patients undergoing hip fracture surgery. Baseline characteristics were assessed preoperatively. During hospital admission presence of delirium was assessed daily according to CAM criteria. This study compared baseline characteristics and outcomes according to a longitudinal pattern of motor subtype expression (predominantly hyperactive, predominantly hypoactive, predominantly mixed, no motor subtype and variable). Motor subtype categorization was performed with the DRS-R98. We also investigated the longitudinal stability of motor subtypes across the delirium episode.

RESULTS

62 patients had experienced in-hospital delirium postoperatively. The full course of the delirium episode could be defined for 42/62 (67.7%) patients. Of the patients with multiple days of delirium only 4/30 (13.3%) patients had a consistent motor subtype profile throughout the delirium episode, while 26/30 (86.7%) patients had a variable course. Of the patients with multiple days of delirium, 5/30 (16.7%) were predominantly hypoactive in profile, 7/30 (23.3%) predominantly hyperactive, 6/30 (20%) predominantly mixed, 1/30 (3.3%) had no motor subtype and 11/30 (36.7%) had a variable profile. Baseline characteristics and outcomes did not differ between the groups.

CONCLUSION

The majority of elderly hip fracture patients in this homogenous sample experienced variable expression of motor subtype over the course of their delirium episodes. The subtype categorization according to dominant motor subtype across the delirium episode identified groups with similar characteristics and outcomes.

Affective functioning after delirium in elderly hip fracture patients

BACKGROUND

Delirium in elderly patients is associated with various long-term sequelae that include cognitive impairment and affective disturbances, although the latter is understudied.

METHODS

For a prospective cohort study of elderly patients undergoing hip fracture surgery, baseline characteristics and affective and cognitive functioning were assessed preoperatively. During hospital admission, presence of delirium was assessed daily. Three months after hospital discharge, affective and global cognitive functioning was evaluated again in patients free from delirium at the time of this follow-up. This study compared baseline characteristics and affective functioning between patients with and without in-hospital delirium. We investigated whether in-hospital delirium is associated with increased anxiety and depressive levels, and post-traumatic stress disorder (PTSD) symptoms three months after discharge.

RESULTS

Among 53 eligible patients, 23 (43.4%) patients experienced in-hospital delirium after hip fracture repair. Patients who had experienced in-hospital delirium showed more depressive symptoms at follow-up after three months compared to the 30 patients without in-hospital delirium. This association persisted in a multivariate model controlling for age, baseline cognition, baseline depressive symptoms, and living situation. The level of anxiety and symptoms of PTSD at follow-up did not differ between both groups.

CONCLUSION

This study suggests that in-hospital delirium is associated with an increased burden of depressive symptoms three months after discharge in elderly patients who were admitted to the hospital for surgical repair of hip fracture. Symptoms of depression in patients with previous in-hospital delirium cannot be fully explained by persistent (sub)syndromal delirium or baseline cognitive impairment.

Predicting delirium duration in elderly hip-surgery patients: does early symptom profile matter?

Background. Features that may allow early identification of patients at risk of prolonged delirium, and therefore of poorer outcomes, are not well understood. The aim of this study was to determine if preoperative delirium risk factors and delirium symptoms (at onset and clinical symptomatology during the course of delirium) are associated with delirium duration. Methods. This study was conducted in prospectively identified cases of incident delirium. We compared patients experiencing delirium of short duration (1 or 2 days) with patients who had more prolonged delirium (≥3 days) with regard to DRS-R-98 (Delirium Rating Scale Revised-98) symptoms on the first delirious day. Delirium symptom profile was evaluated daily during the delirium course. Results. In a homogenous population of 51 elderly hip-surgery patients, we found that the severity of individual delirium symptoms on the first day of delirium was not associated with duration of delirium. Preexisting cognitive decline was associated with prolonged delirium. Longitudinal analysis using the generalised estimating equations method (GEE) identified that more severe impairment of long-term memory across the whole delirium episode was associated with longer duration of delirium. Conclusion. Preexisting cognitive decline rather than severity of individual delirium symptoms at onset is strongly associated with delirium duration.

Evidence-based treatment of delirium in patients with cancer

Delirium is the most common neuropsychiatric complication seen in patients with cancer, and it is associated with significant morbidity and mortality. Increased health care costs, prolonged hospital stays, and long-term cognitive decline are other well-recognized adverse outcomes of delirium. Improved recognition of delirium and early treatment are important in diminishing such morbidity. There has been an increasing number of studies published in the literature over the last 10 years regarding delirium treatment as well as prevention. Antipsychotics, cholinesterase inhibitors, and alpha-2 agonists are the three groups of medications that have been studied in randomized controlled trials in different patient populations. In patients with cancer, the evidence is most clearly supportive of short-term, low-dose use of antipsychotics for controlling the symptoms of delirium, with close monitoring for possible adverse effects, especially in older patients with multiple medical comorbidities. Nonpharmacologic interventions also appear to have a beneficial role in the treatment of patients with cancer who have or are at risk for delirium. This article presents evidence-based recommendations based on the results of pharmacologic and nonpharmacologic studies of the treatment and prevention of delirium.