The association between delirium and the apolipoprotein E epsilon 4 allele: new study results and a meta-analysis

Update on Perioperative Delirium

A strong association between frailty and in-hospital delirium in nonsurgical patients has been shown. Physical and cognitive frailties have been associated with decline and dysfunction in the frontal cognitive domains. Risk factors for frailty are similar to risk factors for postoperative delirium (POD). Frailty can be screened and diagnosed by various tools and instruments. Different anesthetic techniques have been studied to decrease the incidence of POD. However, no anesthetic technique has been conclusively proven to decrease the risk of POD. Patients with dementia develop delirium more often, and delirium is associated with accelerated cognitive decline.

Hemoglobin level, degree of mobilization, and pneumonia are associated with the development of postoperative delirium in cemented hemiarthroplasty after femoral neck fracture

PURPOSE

The aim of this retrospective study was to identify independent prognostic factors for developing a postoperative delirium (POD) in patients suffering from a proximal femoral neck fracture and treated by implantation of a hemiprosthesis.

METHODS

A retrospective study, including patients with hip hemiarthroplasty due to a femoral neck fracture between 2011 and 2020 was performed. Demographic data, preexisting conditions, intra-/postoperative complications, mobilization and laboratory results were extracted from the patients' charts. The different parameters were analyzed comparing patients with and without POD.

RESULTS

412 patients, mean age of 81 ± 9.58 years were included, 66.5% (n = 274) were female, 18.2% (n = 75) of them developed a POD. Significantly higher incidence of POD was associated with older age (p < 0.001), lower level of haemoglobin (p < 0.001), higher post-surgery interleukin 6 (IL 6) level (p = 0.008), higher postoperative level of leukocytes (p = 0.01). Patients with POD received more units of packed red blood cells (PRBC) (p = 0.007). Patients with no mobility limitations pre-operatively developed POD less frequently (p = 0.01), whereas suffering from pneumonia (p = 0.03) or limited mobility postoperatively increased the risk of POD (p < 0.001).

CONCLUSION

This study could help to identify patients with a risk for developing POD after a hemiarthroplasty in femoral neck fractures. As a consequence, frequent controls of Hb, IL 6 and leucocytes levels to avoid anemia and infections, as well as the well surgical treatment to guarantee a good postoperative outcome.

APOEε4, in-hospital delirium and long-term cognitive impairment: A longitudinal memory clinic study

INTRODUCTION

Delirium is common among hospitalized elderly. Previous short-term studies reported inconsistent associations between APOEε4 allele, in-hospital delirium, and post-delirium cognitive impairment. We examined the association of APOEε4 allele with in-hospital delirium and long-term cognitive outcomes following delirium.

METHODS

The electronic medical records were linked to the Korean National Health Insurance Service database of all citizens from January 2002 to July 2019. The study population consisted of 1057 memory clinic visitors with APOE genotype, longitudinal neuropsychological tests, and hospitalization records. Incident in-hospital delirium was defined as the initiation of antipsychotics during hospitalization after excluding prevalent users. Incidence analysis was conducted using Cox proportional hazards models, while longitudinal outcomes were analyzed using multivariable mixed models with an interrupted time series design.

RESULTS

At baseline, APOEε4 carriers (N = 298, 28.2%) performed poorly on cognitive tests compared to non-carriers (CDR-SB mean±SD: 3.3 ± 3.5 vs 2.8 ± 2.9, P = 0.016; MMSE 22.3 ± 5.8 vs 23.2 ± 5.2, P = 0.029). The carriers developed more in-hospital delirium than noncarriers after covariate adjustments (HR 1.96, 95%CI 1.30-2.96, P = 0.002). The APOEε4 allele also had a more detrimental impact on four out of the five cognitive and functional measurements after the delirium (beta estimates of post-delirium change by APOEε4 for CDR-SB = 3.20, P < 0.001; CDR = 0.60, P < 0.001; KIADL = 0.99, P < 0.001; SIADL = 14.07, P < 0.001). These findings remained robust even after adjusting for covariates.

CONCLUSIONS

APOEε4 carriers demonstrated robust associations with in-hospital delirium and exhibited more post-delirium cognitive and functional impairment compared to non-carriers. Individuals with APOEε4 allele may need more attention to prevent in-hospital delirium and post-delirium cognitive and functional deterioration.

Update on Perioperative Delirium

A strong association between frailty and in-hospital delirium in nonsurgical patients has been shown. Physical and cognitive frailties have been associated with decline and dysfunction in the frontal cognitive domains. Risk factors for frailty are similar to risk factors for postoperative delirium (POD). Frailty can be screened and diagnosed by various tools and instruments. Different anesthetic techniques have been studied to decrease the incidence of POD. However, no anesthetic technique has been conclusively proven to decrease the risk of POD. Patients with dementia develop delirium more often, and delirium is associated with accelerated cognitive decline.

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

Delirium superimposed on dementia (DSD) occurs when patients with pre-existing dementia develop delirium. This complication causes patients to become impaired, posing safety concerns for both hospital staff and patients. Furthermore, there is an increased risk of worsening functional disability and death. Despite medical advances, DSD provides both diagnostic and therapeutic challenges to providers. Identifying at-risk patients and providing personalized medicine and patient care can decrease disease burden in a time-efficient manner. This review delves into bioinformatics-based studies of DSD in order to design and implement a personalized medicine-based approach. Our findings suggest alternative medical treatment methods based on gene-gene interactions, gene-microRNA (miRNA) interactions, gene-drug interactions, and pharmacogenetic variants involved in dementia and psychiatric disorders. We identify 17 genes commonly associated with both dementia and delirium including apolipoprotein E (ApoE), brain-derived neurotrophic factor (BDNF), catechol-O-methyltransferase (COMT), butyrylcholinesterase (BChE), acetylcholinesterase (AChE), DNA methyltransferase 1 (DNMT1), prion protein (PrP), tumor necrosis factor (TNF), serine palmitoyltransferase long chain base subunit 1 (SPTLC1), microtubule-associated protein tau (MAPT), alpha-synuclein (αS), superoxide dismutase 1 (SOD1), amyloid beta precursor protein (APP), neurofilament light (NFL), neurofilament heavy, 5-hydroxytryptamine receptor 2A (HTR2A), and serpin family A member 3 (ERAP3). In addition, we identify six main genes that form an inner concentric model, as well as their associated miRNA. The FDA-approved medications that were found to be effective against the six main genes were identified. Furthermore, the PharmGKB database was used to identify variants of these six genes in order to suggest future treatment options. We also looked at previous research and evidence on biomarkers that could be used to detect DSD. According to research, there are three types of biomarkers that can be used depending on the stage of delirium. The pathological mechanisms underlying delirium are also discussed. This review will identify treatment and diagnostic options for personalized DSD management.

Apolipoprotein E4 allele is genetically associated with risk of the short- and medium-term postoperative cognitive dysfunction: A meta-analysis and trial sequential analysis

The aim of systematic review and meta-analysis was to investigate whether APOE4 was associated with postoperative neurologic dysfunction occurrence in short- or medium-term among surgical patients and to study the potential genetic association among these two entities. We searched electronic databases for reserch studies to evaluate the association of APOE4 with postoperative delirium (POD) or short- and medium term postoperative cognitive dysfunction (POCD). Twenty-two trials (16 prospective and six retrospective) with 6734 patients were included. APOE4 alleles was shown significantly associated with POCD within 1 week (odds ratio, OR, 1.89, 95% confidence interval, CI, 1.36 to 2.6278, p < 0.01) in the random-effects model. A significant association was also noted between APOE4 and POCD in medium-term, 1-3 months, after surgery (OR: 1.67, 95% CI: 1.003-2.839, p = 0.049). However, APOE4 was not significantly associated with POCD 1 year after surgery (OR: 0.98, 95% CI: 0.57-1.70, p = 0.9449) and POD (OR: 1.28, 95% CI: 0.85-1.91, p = 0.23). In conclusion, APOE4 alleles was genetically associated with short- and medium-term postoperative neurological dysfunction and future screening or preventive strategies derived is highly potential to improve outcomes.

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.

The complex interaction of genetics and delirium: a systematic review and meta-analysis

The objective is to understand genetic predisposition to delirium. Following PRISMA guidelines, we undertook a systematic review of studies involving delirium and genetics in the databases of Pubmed, Scopus, Cochrane Library and PsycINFO, and performed a meta-analysis when appropriate. We evaluated 111 articles, of which 25 were finally included in the analysis. The studies were assessed by two independent researchers for methodological quality using the Downs and Black Tool and for genetic analysis quality. We performed a meta-analysis of 10 studies of the Apolipoprotein E (APOE) gene, obtaining no association with the presence of delirium (LOR 0.18, 95% CI - 0.10-0.47, p = 0.21). Notably, only 5 out of 25 articles met established criteria for genetic studies (good quality) and 6 were of moderate quality. Seven studies found an association with APOE4, the dopamine transporter gene SCL6A3, dopamine receptor 2 gene, glucocorticoid receptor, melatonin receptor and mitochondrial DNA haplotypes. One genome-wide association study found two suggestive long intergenic non-coding RNA genes. Five studies found no association with catechol-o-methyltransferase, melatonin receptor or several interleukins genes. The studies were heterogenous in establishing the presence of delirium. Future studies with large samples should further specify the delirium phenotype and deepen our understanding of interactions between genes and other biological factors.

Current Challenges in the Recognition and Management of Delirium Superimposed on Dementia

Delirium occurring in a patient with preexisting dementia is referred to as delirium superimposed on dementia (DSD). DSD commonly occurs in older hospitalized patients and is associated with worse outcomes, including higher rates of mortality and institutionalization, compared to inpatients with delirium or dementia alone. This narrative review summarizes the screening, diagnosis, management, and pathophysiology of DSD and concludes by highlighting opportunities for future research. Studies were identified via Medline and PsycINFO keyword search, and handsearching reference lists. Conceptually, DSD could be considered an "acute exacerbation" of dementia precipitated by a noxious insult akin to an acute exacerbation of heart failure or acute on chronic renal failure. However, unlike other organ systems, there are no established biomarkers for delirium, so DSD is diagnosed and monitored clinically. Because cognitive dysfunction is common to both delirium and dementia, the diagnosis of DSD can be challenging. Inattention, altered levels of arousal, and motor dysfunction may help distinguish DSD from dementia alone. An informant history suggestive of an acute change in cognition or alertness should be investigated and managed as delirium until proven otherwise. The key management principles include prevention, identifying and treating the underlying precipitant(s), implementing multicomponent interventions to create an ideal environment for brain recovery, preventing complications, managing distress, and monitoring for resolution. Informing and involving family members or caregivers throughout the patient journey are essential because there is significant prognostic uncertainty, including the risk of persistent cognitive and functional decline following DSD and relapse. Furthermore, informal carers can provide significant assistance in management. Emerging evidence demonstrates that increased exposure to delirium is associated with neuronal injury and worse cognitive outcomes although the mechanisms through which this occurs remain unclear. Given the clinical overlap between delirium and dementia, studying shared pathophysiological pathways may uncover diagnostic tests and is an essential step in therapeutic innovation.

Preoperative Cognitive Impairment and Postoperative Delirium Predict Decline in Activities of Daily Living after Cardiac Surgery-A Prospective, Observational Cohort Study

Cardiac surgery and subsequent treatment in the intensive care unit (ICU) has been shown to be associated with functional decline, especially in elderly patients. Due to the different assessment tools and assessment periods, it remains yet unclear what parameters determine unfavorable outcomes. This study sought to identify risk factors during the entire perioperative period and focused on the decline in activity of daily living (ADL) half a year after cardiac surgery. Follow-ups of 125 patients were available. It was found that in the majority of patients (60%), the mean ADL declined by 4.9 points (95% CI, −6.4 to −3.5; p < 0.000). In the “No decline” -group, the ADL rose by 3.3 points (2.0 to 4.6; p < 0.001). A multiple regression analysis revealed that preoperative cognitive impairment (MMSE ≤ 26; Exp(B) 2.862 (95%CI, 1.192–6.872); p = 0.019) and duration of postoperative delirium ≥ 2 days (Exp(B) 3.534 (1.094–11.411); p = 0.035) was independently associated with ADL decline half a year after the operation and ICU. Of note, preoperative ADL per se was neither associated with baseline cognitive function nor a risk factor for functional decline. We conclude that the preoperative assessment of cognitive function, rather than functional assessments, should be part of risk stratification when planning complex cardiosurgical procedures.

Apolipoprotein E genotype and the association between C-reactive protein and postoperative delirium: Importance of gene-protein interactions

INTRODUCTION

Apolipoprotein E (APOE) status may modify the risk of postoperative delirium conferred by inflammation.

METHODS

We tested whether APOE modifies the established association between C-reactive protein (CRP) and delirium incidence, severity, and duration in 553 noncardiac surgical patients aged 70 and older. High postoperative plasma CRP (≥234.12 mg/L) was defined by the highest sample-based quartile. Delirium was determined using the Confusion Assessment Method and chart review, and severity was determined by the Confusion Assessment Method-Severity score.

RESULTS

APOE ε4 carrier prevalence was 19%, and postoperative delirium occurred in 24%. The relationship between CRP and delirium incidence, severity, and duration differed by ε4 status. Among ε4 carriers, there was a strong relationship between high CRP (vs. low CRP) and delirium incidence (relative risk [95% confidence interval], 3.0 [1.4-6.7]); however, no significant association was observed among non-ε4 carriers (relative risk [95% CI], 1.2 [0.8-1.7]).

DISCUSSION

Our findings raise the possibility that APOE ε4 carrier status may modify the relationship between postoperative day 2 CRP levels and postoperative delirium.

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.

In Thai Nationals, the ApoE4 Allele Affects Multiple Domains of Neuropsychological, Biobehavioral, and Social Functioning Thereby Contributing to Alzheimer's Disorder, while the ApoE3 Allele Protects Against Neuropsychiatric Symptoms and Psychosocial Deficits

The apolipoprotein E epsilon 4 (ApoE4) allele is the strongest genetic risk factor for Alzheimer's disorder (AD) and is associated with semantic and episodic memory deficits. The aim of this study was to examine the associations between ApoE alleles (E2, E3, E4) and genotypes and neuropsychological tests, behavioral functions, and dementia symptoms as assessed using Consortium to Establish a Registry for Alzheimer's Disease (CERAD). This study included 60 patients with Alzheimer's disorder (AD), 60 with mild cognitive disorder (MCI), and 62 normal volunteers. ApoE4 carriers and individuals with E3/E4 and E4/E4 genotypes show an increased incidence of AD, but not MCI. ApoE4 carriers and especially E4/E4 homozygotes show a worse outcome on the CERAD total score, Blessed Dementia Scale, and Short Blessed Test and lower scores on the Verbal Fluency Test, Boston Naming Test, Constructional Praxis Recall, and Word List Memory, Recall, and Recognition. ApoE4 carriers and E4/E3 heterozygotes show higher scores on the Clock Drawing Test. ApoE4 carriers show a worse outcome on the CERAD clinical history scores of memory, language, personality, ADL, orientation, and social skills, while allele AopE3 carriers show better scores on activities of daily living (ADL) and social skills. ApoE3 carriers show lower total weighted, irritability/aggression, and behavioral dysregulation scores on the Behavior Rating Scale for Dementia. The results show that in Thai individuals, the presence of ApoE4 allele is accompanied by a multifarious decline in neurocognitive functions and behavioral features and that ApoE3 may convey protection against neuropsychiatric symptoms and a decline in social skills. ApoE4 and especially the E4/E4 genotype may affect multiple domains of cognitive, biobehavioral, and social functioning thereby contributing to AD phenomenology.

Observational cohort study examining apolipoprotein E status and preoperative neuropsychological performance as predictors of post-operative delirium in an older elective arthroplasty population

Introduction

delirium following surgery is common and is associated with negative outcomes. Preoperative cognitive impairment has been shown to be a risk factor for post-operative delirium. Often the cognitive tests used are cumbersome. This study tests the hypothesis that the quantification of brain vulnerability, using Apolipoprotein E (ApoE) status and neuropsychological tests, both traditional and more easily administered, can quantify the risk of post-operative delirium following elective primary arthroplasty surgery.

Methods

this observational cohort study recruited participants aged 65 years or older admitted prior to elective primary hip or knee arthroplasty. Baseline data was collected and participants underwent neuropsychological testing and had blood taken for ApoE genotyping preoperatively. Post-operatively participants were assessed daily for delirium using the Confusion Assessment Method (CAM) and charts were reviewed where possible for reports of delirium. Univariate and multivariate analyses of preoperative factors were undertaken to identify independent predictors of delirium.

Results

between March 2012 and October 2014, 315 participants completed the study with an overall incidence of post-operative delirium of 40/315 (12.7%). Of these 18 fulfilled the CAM criteria for delirium and 22 were deemed delirious by consensus decision based on chart review. ApoE genotype was not associated with post-operative delirium in this cohort. Time taken to complete Colour Trails 2, errors in mini mental state examination and level of pain preoperatively were independent predictors of post-operative delirium.

Conclusions

this study challenges the assertion that ApoE4 genotype predicts post-operative delirium. It replicates previous work suggesting cognitive impairment predicts post-operative delirium and shows for the 1st time that simple cognitive tests can be as effective as more detailed tests.

Cerebrospinal Fluid Apolipoprotein E Levels in Delirium

Background/Aims

Delirium and the apolipoprotein E ε4 allele are risk factors for late-onset Alzheimer disease (LOAD), but the connection is unclear. We looked for an association.

Methods

Inpatients with delirium (n = 18) were compared with LOAD outpatients (n = 19), assaying blood and cerebrospinal fluid (CSF) using multiplex ELISA.

Results

The patients with delirium had a higher Confusion Assessment Method (CAM) score (5.6 ± 1.2 vs. 0.0 ± 0.0; p < 0.001) and Delirium Index (13.1 ± 4.0 vs. 2.9 ± 1.2; p = 0.001) but a lower Mini-Mental State Examination (MMSE) score (14.3 ± 6.8 vs. 20.8 ± 4.6; p = 0.003). There was a reduction in absolute CSF apolipoprotein E level during delirium (median [interquartile range]: 9.55 μg/mL [5.65–15.05] vs. 16.86 μg/mL [14.82–20.88]; p = 0.016) but no differences in apolipoprotein A1, B, C3, H, and J. There were no differences in blood apolipoprotein levels, and no correlations between blood and CSF apolipoprotein levels. CSF apolipoprotein E correlated negatively with the CAM score (r = −0.354; p = 0.034) and Delirium Index (r = −0.341; p = 0.042) but not with the Acute Physiology and Chronic Health Evaluation (APACHE) index, or the MMSE or Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE).

Conclusion

Reduced CSF apolipoprotein E levels during delirium may be a mechanistic link between two important risk factors for LOAD.

A systematic review and meta-analysis of the association between the apolipoprotein E genotype and delirium

The role of apolipoprotein E (APOE) in Alzheimer's disease and other dementias has been investigated intensively. However, the relationship between APOE and delirium has only recently been explored in studies that have included relatively small samples. A meta-analysis of the published pooled data is timely to explore the relationship between APOE and delirium and to inform further research in this topic. PubMed, EBSCOhost, Google Scholar, Scopus, all EBM Reviews (OVID) and the Cochrane Database of Systematic Reviews were searched with relevant keywords and from the references of relevant papers. Ten papers were found that examined the relationship between APOE and delirium. Data were extracted from eight of them and pooled for meta-analysis using random effects with R software. Data from 1762 participants, of whom 479 (27.2%) were diagnosed with delirium, showed low heterogeneity (Q=13.11, d.f.=7, P=0.07; I=44.86%). The possession of the APOE ε4 allele has a small (log odds ratio: 0.18, 95% confidence interval: 0.23-0.59), nonsignificant (P=0.38) effect on the presence of delirium. No publication bias was identified. The metapower of the pooled data was low (α=0.05, power=0.65). On analysing the studies to date, it seems that there is no association between APOE and the occurrence of delirium. We suggest that further studies are needed with greater number of patients to clarify any association as well as to examine for other patterns of association including relevance for subgroups of patients who develop delirium and for effects on the phenotype of delirium and the outcomes.

Does Apolipoprotein E Genotype Increase Risk of Postoperative Delirium?

OBJECTIVE

To determine whether apolipoprotein E (ApoE) is associated with postoperative delirium incidence, severity, and duration in older patients free of dementia at baseline.

METHODS

The authors examined 557 nondemented patients aged 70 years or older undergoing major noncardiac surgery enrolled in the Successful Aging after Elective Surgery Study. Three ApoE measures were considered: ε2, ε4 carriers versus noncarriers, and a three-category ApoE measure. Delirium was determined using the Confusion Assessment Method (CAM) and chart review. We used generalized linear models to estimate the association between ApoE and delirium incidence, severity (peak CAM Severity [CAM-S] score), and days.

RESULTS

ApoE ε2 and ε4 was present in 15% and 19%, respectively, and postoperative delirium occurred in 24%. Among patients with delirium, the mean peak CAM-S score was 8.0 (standard deviation: 4), with most patients experiencing 1 or 2 delirium days (51% or 28%, respectively). After adjusting for age, sex, surgical procedure, and preoperative cognitive function, ApoE ε4 and ε2 carrier status were not associated with postoperative delirium: RR for ε4=1.0, 95% CI: 0.7-1.5 and RR for ε2=0.9, 95% CI: 0.6-1.4. No association between ApoE and delirium severity or number of delirium days was observed.

CONCLUSION

In older surgery patients free of dementia, our findings do not support the hypothesis that the ApoE genotype does not confer either risk or protection in postoperative delirium incidence, severity, or duration. Thus, an important genetic risk factor for Alzheimer disease does not affect risk of delirium.

Postoperative Delirium in the Geriatric Patient

Postoperative delirium, a common complication in older surgical patients, is independently associated with increased morbidity and mortality. Patients older than 65 years receive greater than one-third of the more than 40 million anesthetics delivered yearly in the United States. This number is expected to increase with the aging of the population. Thus, it is increasingly important that perioperative clinicians who care for geriatric patients have an understanding of the complex syndrome of postoperative delirium.

Biomarkers of postoperative delirium and cognitive dysfunction

Elderly surgical patients frequently experience postoperative delirium (POD) and the subsequent development of postoperative cognitive dysfunction (POCD). Clinical features include deterioration in cognition, disturbance in attention and reduced awareness of the environment and result in higher morbidity, mortality and greater utilization of social financial assistance. The aging Western societies can expect an increase in the incidence of POD and POCD. The underlying pathophysiological mechanisms have been studied on the molecular level albeit with unsatisfying small research efforts given their societal burden. Here, we review the known physiological and immunological changes and genetic risk factors, identify candidates for further studies and integrate the information into a draft network for exploration on a systems level. The pathogenesis of these postoperative cognitive impairments is multifactorial; application of integrated systems biology has the potential to reconstruct the underlying network of molecular mechanisms and help in the identification of prognostic and diagnostic biomarkers.

Review of delirium in patients with Parkinson's disease

Parkinson's disease (PD) is common and has a number of associated neuropsychiatric disturbances. Of these, delirium has historically been under-recognised. Delirium is an acute disturbance of attention and awareness that fluctuates, and is accompanied by an additional disturbance of cognition. As delirium is known to carry a particularly poor prognosis in terms of morbidity and mortality, and the relationship between delirium and dementia is becoming better defined, we completed a literature review of delirium in the context of PD. A literature search was completed using the databases PubMed, Embase and Ovid Medline. PubMed (1945-2014) was searched in September 2014; Embase (1974-2014); and Ovid Medline (1946-2014) in October 2014. The search terms 'delirium' and 'Parkinsons' in combination were used. Large studies using a robust definition of delirium were lacking in PD. There is the suggestion that PD is a risk factor for delirium and that delirium negatively impacts upon the motor symptom trajectory. Deficits in the neurotransmitters dopamine and acetylcholine are implicated in the pathophysiology of delirium in PD. Systemic inflammation also appears to have a role. Treatment of delirium in PD should include medication review and cautious use of atypical antipsychotics where pharmacological treatment is indicated. Of the atypical antipsychotics studied, quetiapine has the least extrapyramidal side effects. Evidence suggests a specific link between delirium and PD but well-designed clinical studies to evaluate the prevalence, impact and treatment of delirium in PD are required. Given the potential to improve outcomes through delirium prevention we conclude that delirium in PD is an area worthy of further study.

Quantitative proteomics of delirium cerebrospinal fluid

Delirium is a common cause and complication of hospitalization in older people, being associated with higher risk of future dementia and progression of existing dementia. However relatively little data are available on which biochemical pathways are dysregulated in the brain during delirium episodes, whether there are protein expression changes common among delirium subjects and whether there are any changes which correlate with the severity of delirium. We now present the first proteomic analysis of delirium cerebrospinal fluid (CSF), and one of few studies exploring protein expression changes in delirium. More than 270 proteins were identified in two delirium cohorts, 16 of which were dysregulated in at least 8 of 17 delirium subjects compared with a mild Alzheimer's disease neurological control group, and 31 proteins were significantly correlated with cognitive scores (mini-mental state exam and acute physiology and chronic health evaluation III). Bioinformatics analyses revealed expression changes in several protein family groups, including apolipoproteins, secretogranins/chromogranins, clotting/fibrinolysis factors, serine protease inhibitors and acute-phase response elements. These data not only provide confirmatory evidence that the inflammatory response is a component of delirium, but also reveal dysregulation of protein expression in a number of novel and unexpected clusters of proteins, in particular the granins. Another surprising outcome of this work is the level of similarity of CSF protein profiles in delirium patients, given the diversity of causes of this syndrome. These data provide additional elements for consideration in the pathophysiology of delirium as well as potential biomarker candidates for delirium diagnosis.

Interleukin 6 and apolipoprotein E as predictors of acute brain dysfunction and survival in critical care patients

BACKGROUND

Delirium occurs in up to 80% of intensive care patients and is associated with poor outcomes. The biological cause of delirium remains elusive.

OBJECTIVES

To determine if delirium and recovery are associated with serum levels of interleukins and apolipoprotein E over time and with apolipoprotein E genotype.

METHODS

The sample consisted of 77 patients with no previous cognitive deficits who required mechanical ventilation for 24 to 96 hours. Daily serum samples were obtained for enzyme-linked immunosorbent assay measurements of interleukins 6, 8, and 10 and apolipoprotein E. DNA extracted from blood was analyzed for apolipoprotein E genotyping. The Confusion Assessment Method for the Intensive Care Unit was administered daily on days 2 through 9.

RESULTS

Among the 77 patients, 23% had no delirium, 46% experienced delirium, and 31% experienced coma. Additionally, 77% had delirium or coma (acute brain dysfunction), and compared with other patients, had fewer ventilator-free days (P = .03), longer stay (P = .04), higher care needs at discharge (P = .001), higher mortality (P = .02), and higher levels of interleukin 6 (P = .03), and the APOE*3/*3 apolipoprotein E genotype (P = .05). Serum levels of apolipoprotein E correlated with levels of interleukins 8 and 10. Patients with the E4 allele of apolipoprotein E had shorter duration of delirium (P = .02) and lower mortality (P = .03) than did patients without this allele.

CONCLUSIONS

Apolipoprotein E plays a complex role in illness response and recovery in critically ill patients. The relationship between apolipoprotein E genotype and brain dysfunction and survival is unclear.

Neuropathogenesis of delirium: review of current etiologic theories and common pathways

Delirium is a neurobehavioral syndrome caused by dysregulation of neuronal activity secondary to systemic disturbances. Over time, a number of theories have been proposed in an attempt to explain the processes leading to the development of delirium. Each proposed theory has focused on a specific mechanism or pathologic process (e.g., dopamine excess or acetylcholine deficiency theories), observational and experiential evidence (e.g., sleep deprivation, aging), or empirical data (e.g., specific pharmacologic agents' association with postoperative delirium, intraoperative hypoxia). This article represents a review of published literature and summarizes the top seven proposed theories and their interrelation. This review includes the "neuroinflammatory," "neuronal aging," "oxidative stress," "neurotransmitter deficiency," "neuroendocrine," "diurnal dysregulation," and "network disconnectivity" hypotheses. Most of these theories are complementary, rather than competing, with many areas of intersection and reciprocal influence. The literature suggests that many factors or mechanisms included in these theories lead to a final common outcome associated with an alteration in neurotransmitter synthesis, function, and/or availability that mediates the complex behavioral and cognitive changes observed in delirium. In general, the most commonly described neurotransmitter changes associated with delirium include deficiencies in acetylcholine and/or melatonin availability; excess in dopamine, norepinephrine, and/or glutamate release; and variable alterations (e.g., either a decreased or increased activity, depending on delirium presentation and cause) in serotonin, histamine, and/or γ-aminobutyric acid. In the end, it is unlikely that any one of these theories is fully capable of explaining the etiology or phenomenologic manifestations of delirium but rather that two or more of these, if not all, act together to lead to the biochemical derangement and, ultimately, to the complex cognitive and behavioral changes characteristic of delirium.

Association between APOE epsilon 4 allele and postoperative cognitive dysfunction: a meta-analysis

BACKGROUND

Carriers of the apolipoprotein E epsilon 4 allele (APOEε4) may be at increased risk of postoperative cognitive dysfunction (POCD), but this association has not been reported consistently. We conducted a meta-analysis to derive a more precise conclusion.

METHODS

The PubMed, EBSCO and EMBASE databases were searched for eligible studies published in English before March 2013. The association between APOEε4 and POCD was expressed by the odds ratio (OR) with 95% confidence interval (CI). Funnel plots were constructed and publication bias assessed by Egger's test.

RESULTS

Nine studies encompassing 1063 APOEε4 carriers and 2983 noncarriers were included. At about 1-week postsurgery, a significant association between APOEε4 and POCD was found (OR 1.83, 95% CI: 1.18-2.85), but the association was no longer significant after removing one large study (OR 1.35, 95% CI: 0.92-1.97). Stratified analysis of cardiac/vascular surgery patients also yielded no significant correlation (OR 1.62, 95% CI: 0.80-3.28). One to three months postsurgery, neither the overall analysis (OR 1.56, 95% CI: 0.87-2.81) nor the stratified analysis of cardiac/vascular surgery patients (OR 3.33, 95% CI: 0.55-20.22) indicated a significant correlation. APOEε4 was also not correlated with POCD at 1-year postsurgery (OR 1.15, 95% CI: 0.71-1.86). No evidence of publication bias was revealed by Egger's test.

CONCLUSIONS

The APOEε4 allele was associated with a significantly increased POCD risk about 1-week postsurgery, but the association depended on one large study. No association was found 1-3 months and 1-year postsurgery.

Delirium in the acute phase after stroke and the role of the apolipoprotein E gene

OBJECTIVE

To study the association between the epsilon 4 allele of apolipoprotein E (APOEε4) and delirium in a stroke population.

METHODS

527 consecutive stroke patients were screened for delirium during the first week of admission with the confusion assessment method. In three hundred fifty-three patients genomic DNA isolation was available.

RESULTS

The incidence of delirium after stroke in the 353 patients was 11.3%. There was no association between APOEε4 and delirium. Even after adjustment for IQCODE, stroke localization, stroke subtype, stroke severity, infection, and brain atrophy no association was found (odds ratio: 0.9; 95% confidence interval: 0.4-2.1). Delirium did not last longer in patients with an APOEε4 allele compared to patients without an APOEε4 allele (median: 5.6 days [range: 1-21] versus median: 4.6 days [range: 1-15], p = 0.5).

CONCLUSION

There was no association between the presence of an APOEε4 allele and the occurrence of delirium in the acute phase after stroke.

Predisposing and precipitating factors of delirium after cardiac surgery: a prospective observational cohort study

OBJECTIVE

To comprehensively assess pre-, intra-, and postoperative delirium risk factors as potential targets for intervention.

BACKGROUND

Delirium after cardiac surgery is associated with longer intensive care unit (ICU) stay, and poorer functional and cognitive outcomes. Reports on delirium risk factors so far did not cover the full range of patients' presurgical conditions, intraoperative factors, and postoperative course.

METHODS

After written informed consent, 221 consecutive patients ≥ 50 years scheduled for cardiac surgery were assessed for preoperative cognitive performance, and functional and physical status. Clinical and biochemical data were systematically recorded perioperatively.

RESULTS

Of the 215 patients remaining for analysis, 31% developed delirium in the intensive care unit. Using logistic regression models, older age [73.3 (71.2-75.4) vs 68.5 (67.0-70.0); P = 0.016], higher Charlson's comorbidity index [3.0 (1.5-4.0) vs 2.0 (1.0-3.0) points; P = 0.009], lower Mini-Mental State Examination (MMSE) score (MMSE, [27 (23-29) vs 28 (27-30) points; P = 0.021], length of cardiopulmonary bypass (CPB) [CPB; 133 (112-163) vs 119 (99-143) min; P = 0.004], and systemic inflammatory response syndrome in the intensive care unit [25 (36.2%) vs 13 (8.9%); P = 0.001] were independently associated with delirium. Combining age, MMSE score, Charlson's comorbidity index, and length of CPB in a regression equation allowed for a prediction of postoperative delirium with a sensitivity of 71.19% and a specificity of 76.26% (receiver operating analysis, area under the curve: 0.791; 95% confidence interval: 0.727-0.845).

CONCLUSIONS

Further research will evaluate if modification of these risk factors prevents delirium and improves outcomes.

Polymorphisms in the melatonin receptor 1B gene and the risk of delirium

BACKGROUND/AIMS

A disturbed sleep-wake rhythm cycle can be seen in delirium and as melatonin regulates this cycle via melatonin receptors, genetic variations in these receptors may contribute to susceptibility to delirium. The purpose of this study was to investigate whether genetic variants in the melatonin receptor 1B (MTNR1B) gene are associated with delirium.

METHODS

Elderly medical and hip surgery patients were included in the study. Five single-nucleotide polymorphisms (SNPs) were determined in the MTNR1B gene, i.e. rs18030962, rs3781638, rs10830963, rs156244 and rs4753426.

RESULTS

In total, 53% of 171 hip fracture patients and 33% of 699 medical patients were diagnosed with delirium. None of the polymorphisms were found to be associated with the occurrence of delirium.

CONCLUSION

Future research could focus on sequencing this gene to look for other functional SNPs in relation to delirium.

Delirium in hospitalized patients: implications of current evidence on clinical practice and future avenues for research--a systematic evidence review

BACKGROUND

Despite the significant burden of delirium among hospitalized adults, critical appraisal of systematic data on delirium diagnosis, pathophysiology, treatment, prevention, and outcomes is lacking.

PURPOSE

To provide evidence-based recommendations for delirium care to practitioners, and identify gaps in delirium research.

DATA SOURCES

Medline, PubMed, the Cochrane Library, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) information systems from January 1966 to April 2011.

STUDY SELECTION

All published systematic evidence reviews (SERs) on delirium were evaluated.

DATA EXTRACTION

Three reviewers independently extracted the data regarding delirium risk factors, diagnosis, prevention, treatment, and outcomes, and critically appraised each SER as good, fair, or poor using the United States Preventive Services Task Force criteria.

DATA SYNTHESIS

Twenty-two SERs graded as good or fair provided the data. Age, cognitive impairment, depression, anticholinergic drugs, and lorazepam use were associated with an increased risk for developing delirium. The Confusion Assessment Method (CAM) is reliable for delirium diagnosis outside of the intensive care unit. Multicomponent nonpharmacological interventions are effective in reducing delirium incidence in elderly medical patients. Low-dose haloperidol has similar efficacy as atypical antipsychotics for treating delirium. Delirium is associated with poor outcomes independent of age, severity of illness, or dementia.

CONCLUSION

Delirium is an acute, preventable medical condition with short- and long-term negative effects on a patient's cognitive and functional states.

Vulnerability: the crossroads of frailty and delirium

Frailty and delirium, although seemingly distinct syndromes, both result in significant negative health outcomes in older adults. Frailty and delirium may be different clinical expressions of a shared vulnerability to stress in older adults, and future research will determine whether this vulnerability is age related, pathological, genetic, environmental, or most likely, a combination of all of these factors. This article explores the clinical overlap of frailty and delirium, describes possible pathophysiological mechanisms linking the two, and proposes research opportunities to further knowledge of the interrelationships between these important geriatric syndromes. Frailty, a diminished ability to compensate for stressors, is generally viewed as a chronic condition, whereas delirium is an acute change in attention and cognition, but there is a developing literature on transitions in frailty status around acute events, as well as on delirium as a chronic, persistent condition. If frailty predisposes an individual to delirium, and delirium delays recovery from a stressor, then both syndromes may contribute to a downward spiral of declining function, increasing risk, and negative outcomes. In addition, frailty and delirium may have shared pathophysiology, such as inflammation, atherosclerosis, and chronic nutritional deficiencies, which will require further investigation. The fields of frailty and delirium are rapidly evolving, and future research may help to better define the interrelationship of these common and morbid geriatric syndromes. Because of the heterogeneous pathophysiology and presentation associated with frailty and delirium, typical of all geriatric syndromes, multicomponent prevention and treatment strategies are most likely to be effective and should be developed and tested.

Biomarkers for delirium--a review

To improve delirium recognition and care, numerous serum biomarkers have been investigated as potential tools for risk stratification, diagnosis, monitoring, and prognostication of delirium. The literature was reviewed, and no evidence was found to support the clinical use of any delirium biomarker, although certain biomarkers such as S-100 beta and insulin-like growth factor-1 and inflammatory markers have shown some promising results that need to be evaluated in future studies with appropriate sample size, prospective designs, and in a more-generalizable population.

Pharmacological and nonpharmacological management of delirium in critically ill patients

Delirium is a common yet under-diagnosed syndrome of acute brain dysfunction, which is characterized by inattention, fluctuating mental status, altered level of consciousness, or disorganized thinking. Although our recognition of risk factors for delirium has progressed, our understanding of the underlying pathophysiologic mechanisms remains limited. Improvements in monitoring and assessment for delirium (particularly in the intensive care setting) have resulted in validated and reliable tools such as arousal scales and bedside delirium monitoring instruments. Once delirium is recognized and the modifiable risk factors are addressed, the next step in management (if delirium persists) is often pharmacological intervention. The sedatives, analgesics, and hypnotics most often used in the intensive care unit (ICU) to achieve patient comfort are all too frequently deliriogenic, resulting in a longer duration of ICU and hospital stay, and increased costs. Therefore, identification of safe and efficacious agents to reduce the incidence, duration, and severity of ICU delirium is a hot topic in critical care. Recognizing that there are no medications approved by the Food and Drug Administration (FDA) for the prevention or treatment of delirium, we chose anti-psychotics and alpha-2 agonists as the general pharmacological focus of this article because both were subjects of relatively recent data and ongoing clinical trials. Emerging pharmacological strategies for addressing delirium must be combined with nonpharmacological approaches (such as daily spontaneous awakening trials and spontaneous breathing trials) and early mobility (combined with the increasingly popular approach called: Awakening and Breathing Coordination, Delirium Monitoring, Early Mobility, and Exercise [ABCDE] of critical care) to develop evidence-based approaches that will ensure safer and faster recovery of the sickest patients in our healthcare system.

Postoperative delirium. Part 1: pathophysiology and risk factors

Delirium presents clinically with differing subtypes ranging from hyperactive to hypoactive. The clinical presentation is not clearly linked to specific pathophysiological mechanisms. Nevertheless, there seem to be different mechanisms that lead to delirium; for example the mechanisms leading to alcohol-withdrawal delirium are different from those responsible for postoperative delirium. In many forms of delirium, the brain's reaction to a peripheral inflammatory process is considered to be a pathophysiological key element and the aged brain seems to react more markedly to a peripheral inflammatory stimulus than a younger brain. The effects of inflammatory mediators on the brain include changes in neurotransmission and apoptosis. On a neurotransmitter level, impaired cholinergic transmission and disturbances of the intricate interactions between dopamine, serotonin and acetylcholine seem to play an important role in the development of delirium. The risk factors for delirium are categorised as predisposing or precipitating factors. In the presence of many predisposing factors, even trivial precipitating factors may trigger delirium, whereas in patients without or with only a few predisposing factors, a major precipitating insult is necessary to trigger delirium. Well documented predisposing factors are age, medical comorbidities, cognitive, functional, visual and hearing impairment and institutional residence. Important precipitating factors apart from surgery are admission to an ICU, anticholinergic drugs, alcohol or drug withdrawal, infections, iatrogenic complications, metabolic derangements and pain. Scores to predict the risk of delirium based on four or five risk factors have been validated in surgical patients.

Genetic variations in the interleukin-6 and interleukin-8 genes and the interleukin-6 receptor gene in delirium

OBJECTIVE

The aim of this study was to investigate whether genetic polymorphisms in the interleukin-6 gene (IL6), the IL-6 receptor gene (IL6R), and the IL-8 gene (IL8) were associated with delirium in a population of acutely admitted older patients.

METHODS

This was a prospective cohort study in the Academic Medical Center in Amsterdam, running from April, 2003, through August, 2008. A total of 881 patients, aged 65 years and older, acutely admitted to the medical department or to the surgical department following hip fracture, were included in the study. Delirium was diagnosed by the Confusion Assessment Method. Two single-nucleotide polymorphisms (SNPs) in the IL6 gene, one in the IL6R gene, and one in the IL8 gene were genotyped.

RESULTS

Fifty percent of the 115 surgical patients and 34% of the 605 medical patients experienced delirium. Delirious patients were older (82.8 years vs. 77.6 years) and had more frequent pre-existing functional (64% vs. 36%) or cognitive impairment (83% vs. 26%) (p < 0.001). The determination of polymorphisms had success rates between 87% and 96%. Rs1800697 and rs1800797 in the IL6 gene, rs8192284 in the IL6R gene, and rs4073 in the IL8 gene were not associated with the development of delirium.

CONCLUSION

Recent observations have indicated that IL-6 and IL-8 play a role in delirium in the elderly, but functional genetic variations in the IL6, IL6R, and IL8 genes were not associated with delirium. Still, the inflammatory hypothesis of delirium is gaining ground in the literature on the basis of recent animal research.

Apolipoprotein E gene polymorphism and the risk of intracerebral hemorrhage in the Chinese population

Prior studies investigating the association between apolipoprotein E (APOE) gene polymorphism and the risk of intracerebral hemorrhage (ICH) have been inconsistent and limited to small sample sizes. The aim of this study was to test the hypothesis that APOE gene polymorphisms are associated with the risk of ICH in Chinese Han patients. We enrolled 180 ICH patients and 180 controls. APOE genotype was determined by using a polymerase chain reaction-restriction fragment length polymorphism assay. ICH patients had a significantly lower frequency ɛ3/ɛ3 [odds ratio (OR)=0.45, 95% confidence interval (CI)=0.28, 0.71; p=0.001] and ɛ3 allele (OR=0.51, 95% CI=0.35, 0.76; p=0.001) than healthy controls. ICH patients also had a significantly higher frequency ɛ3/ɛ4 (OR=3.61, 95% CI=1.89, 6.88; p<0.001) and ɛ4 allele (OR=3.00, 95% CI=1.76, 5.13; p<0.001) than healthy controls. This study suggests that the APOE genotype is associated with the risk of ICH in Chinese Han patients.

Is cortisol the key to the pathogenesis of delirium after coronary artery bypass graft surgery?

Postoperative delirium is a serious complication of cardiac surgery. However, the pathophysiology of this mental syndrome is largely unknown. Recent findings suggest an association between elevated level of cortisol and postoperative delirium. Further studies should investigate the mechanisms responsible for excessive perioperative cortisol secretion.