Hospitalization, Alzheimer's Disease and Related Neuropathologies, and Cognitive Decline

2024 Alzheimer's disease facts and figures

This article describes the public health impact of Alzheimer's disease (AD), including prevalence and incidence, mortality and morbidity, use and costs of care and the ramifications of AD for family caregivers, the dementia workforce and society. The Special Report discusses the larger health care system for older adults with cognitive issues, focusing on the role of caregivers and non-physician health care professionals. An estimated 6.9 million Americans age 65 and older are living with Alzheimer's dementia today. This number could grow to 13.8 million by 2060, barring the development of medical breakthroughs to prevent or cure AD. Official AD death certificates recorded 119,399 deaths from AD in 2021. In 2020 and 2021, when COVID-19 entered the ranks of the top ten causes of death, Alzheimer's was the seventh-leading cause of death in the United States. Official counts for more recent years are still being compiled. Alzheimer's remains the fifth-leading cause of death among Americans age 65 and older. Between 2000 and 2021, deaths from stroke, heart disease and HIV decreased, whereas reported deaths from AD increased more than 140%. More than 11 million family members and other unpaid caregivers provided an estimated 18.4 billion hours of care to people with Alzheimer's or other dementias in 2023. These figures reflect a decline in the number of caregivers compared with a decade earlier, as well as an increase in the amount of care provided by each remaining caregiver. Unpaid dementia caregiving was valued at $346.6 billion in 2023. Its costs, however, extend to unpaid caregivers' increased risk for emotional distress and negative mental and physical health outcomes. Members of the paid health care and broader community-based workforce are involved in diagnosing, treating and caring for people with dementia. However, the United States faces growing shortages across different segments of the dementia care workforce due to a combination of factors, including the absolute increase in the number of people living with dementia. Therefore, targeted programs and care delivery models will be needed to attract, better train and effectively deploy health care and community-based workers to provide dementia care. Average per-person Medicare payments for services to beneficiaries age 65 and older with AD or other dementias are almost three times as great as payments for beneficiaries without these conditions, and Medicaid payments are more than 22 times as great. Total payments in 2024 for health care, long-term care and hospice services for people age 65 and older with dementia are estimated to be $360 billion. The Special Report investigates how caregivers of older adults with cognitive issues interact with the health care system and examines the role non-physician health care professionals play in facilitating clinical care and access to community-based services and supports. It includes surveys of caregivers and health care workers, focusing on their experiences, challenges, awareness and perceptions of dementia care navigation.

Selective serotonin reuptake inhibitor use, age-related neuropathology and cognition in late-life

The objective of this study was to evaluate an association of selective serotonin reuptake inhibitor (SSRI) use with late life cognitive decline and further investigate the association with brain pathology. Using the data are from two harmonized clinical-pathologic cohort studies with annual cognitive testing we found that SSRI use was associated with significantly faster global cognitive decline and this association was present in those with and without pre-existing cognitive impairment at the time of SSRI initiation. In separate analyses of persons who died during the study and underwent neuropathologic examination, SSRI use was related to higher level of paired helical filament tau tangles and faster rate of global cognitive decline. However, when SSRI use and tangles were included in the same model, the association of SSRI use with rate of global cognitive decline was reduced by more than 50% and no longer statistically significant. SSRI use was associated with higher postmortem level of tau tangles, possibly because SSRI are being used to treat neurobehavioral symptoms associated with dementia, and this relationship appears to partly account for the association of SSRI use with more rapid cognitive decline.

Disparities in 30-day readmission rates among Medicare enrollees with dementia

BACKGROUND

Readmissions contribute to excessive care costs and burden for people living with dementia. Assessments of racial disparities in readmissions among dementia populations are lacking, and the role of social and geographic risk factors such as individual-level exposure to greater neighborhood disadvantage is poorly understood. We examined the association between race and 30-day readmissions in a nationally representative sample of Black and non-Hispanic White individuals with dementia diagnoses.

METHODS

This retrospective cohort study used 100% Medicare fee-for-service claims from all 2014 hospitalizations nationwide among Medicare enrollees with dementia diagnosis linked to patient, stay, and hospital factors. The sample consisted of 1,523,142 hospital stays among 945,481 beneficiaries. The relationship between all cause 30-day readmissions and the explanatory variable of self-reported race (Black, non-Hispanic White) was examined via generalized estimating equations approach adjusting for patient, stay, and hospital-level characteristics to model 30-day readmission odds.

RESULTS

Black Medicare beneficiaries had 37% higher readmission odds compared to White beneficiaries (unadjusted OR 1.37, CI 1.35-1.39). This heightened readmission risk persisted after adjusting for geographic factors (OR 1.33, CI 1.31-1.34), social factors (OR 1.25, CI 1.23-1.27), hospital characteristics (OR 1.24, CI 1.23-1.26), stay-level factors (OR 1.22, CI 1.21-1.24), demographics (OR 1.21, CI 1.19-1.23), and comorbidities (OR 1.16, CI 1.14-1.17), suggesting racially-patterned disparities in care account for a portion of observed differences. Associations varied by individual-level exposure to neighborhood disadvantage such that the protective effect of living in a less disadvantaged neighborhood was associated with reduced readmissions for White but not Black beneficiaries. Conversely, among White beneficiaries, exposure to the most disadvantaged neighborhoods associated with greater readmission rates compared to White beneficiaries residing in less disadvantaged contexts.

CONCLUSIONS

There are significant racial and geographic disparities in 30-day readmission rates among Medicare beneficiaries with dementia diagnoses. Findings suggest distinct mechanisms underlying observed disparities differentially influence various subpopulations.

Adapting and Testing the Care Partner Hospital Assessment Tool for Use in Dementia Care: Protocol for a 2 Sequential Phase Study

BACKGROUND

Research and policy demonstrate the value of and need for systematically identifying and preparing care partners for their caregiving responsibilities while their family member or friend living with dementia is hospitalized. The Care Partner Hospital Assessment Tool (CHAT) has undergone content and face validation and has been endorsed as appropriate by clinicians to facilitate the timely identification and preparation of care partners of older adult patients during their hospitalization. However, the CHAT has not yet been adapted or prospectively evaluated for use with care partners of hospitalized people living with dementia. Adapting and testing the CHAT via a pilot study will provide the necessary evidence to optimize feasibility and enable future efficacy trials.

OBJECTIVE

The purpose of this paper is to describe the study protocol for the adaptation and testing of the CHAT for use among care partners of hospitalized people living with dementia to better prepare them for their caregiving responsibilities after hospital discharge.

METHODS

Our protocol is based on the National Institutes of Health Stage Model and consists of 2 sequential phases, including formative research and the main trial. In phase 1, we will use a participatory human-centered design process that incorporates people living with dementia and their care partners, health care administrators, and clinicians to adapt the CHAT for dementia care (ie, the Dementia CHAT [D-CHAT]; stage IA). In phase 2, we will partner with a large academic medical system to complete a pilot randomized controlled trial to examine the feasibility and estimate the size of the effect of the D-CHAT on care partners' preparedness for caregiving (stage IB). We anticipate this study to take approximately 60 months to complete, from study start-up procedures to dissemination. The 2 phases will take place between December 1, 2022, and November 30, 2027.

RESULTS

The study protocol will yield (1) a converged-upon, ready-for-feasibility testing D-CHAT; (2) descriptive and feasibility characteristics of delivering the D-CHAT; and (3) effect size estimates of the D-CHAT on care partner preparedness. We anticipate that the resultant D-CHAT will provide clinicians with guidance on how to identify and better prepare care partners for hospitalized people living with dementia. In turn, care partners will feel equipped to fulfill caregiving roles for their family members or friends living with dementia.

CONCLUSIONS

The expected results of this study are to favorably impact hospital-based care processes and outcomes for people living with dementia and their care partners and to elucidate the essential caregiving role that so many care partners of people living with dementia assume.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05592366; https://clinicaltrials.gov/ct2/show/NCT05592366.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/46808.

Care Partner Inclusion of People Hospitalized With Alzheimer Disease and Related Dementias: Protocol for a Mixed Methods Systems Engineering Approach to Designing a Health Care System Toolkit

BACKGROUND

Research and policy demonstrate the value and need for the systematic inclusion of care partners in hospital care delivery of people living with Alzheimer disease and related dementias (ADRD). Support provided to care partners through information and training regarding caregiving responsibilities is important to facilitating their active inclusion and ultimately improving hospital outcomes of people living with ADRD. To promote care partners' active inclusion, a toolkit that guides health systems in the identification, assessment, and training of care partners is needed. User-centered approaches can address this gap in practice by creating toolkits that are practical and responsive to the needs of care partners and their hospitalized family members and friends living with ADRD.

OBJECTIVE

This paper describes the study protocol for the development and refinement of the ADRD Systematic Hospital Inclusion Family Toolkit (A-SHIFT). A-SHIFT will provide health care systems with guidance on how to effectively identify, assess, and train care partners of hospitalized persons living with ADRD.

METHODS

The A-SHIFT study protocol will use a 3-aimed, convergent mixed method approach to iteratively develop and refine the toolkit. In Aim 1, we will use a systems-engineering approach to characterize patterns of care partner inclusion in hospital care for people living with ADRD. In Aim 2, we will partner with stakeholders to identify and prioritize health care system facilitators and barriers to the inclusion for care partners of hospitalized people living with ADRD. In Aim 3, we will work with stakeholders to co-design an adaptable toolkit to be used by health systems to facilitate the identification, assessment, and training of care partners of hospitalized people living with ADRD. Our convergent mixed method approach will facilitate triangulation across all 3 aims to increase the credibility and transferability of results. We anticipate this study to take 24 months between September 1, 2022, and August 31, 2024.

RESULTS

The A-SHIFT study protocol will yield (1) optimal points in the hospital workflow for care partner inclusion, (2) a prioritized list of potentially modifiable barriers and facilitators to including care partners in the hospitalization of people living with ADRD, and (3) a converged-upon, ready for feasibility testing of the toolkit to guide the inclusion of care partners of people living with ADRD in hospital care.

CONCLUSIONS

We anticipate that the resultant A-SHIFT will provide health systems with a readiness checklist, implementation plan, and resources for identifying, assessing, and training care partners on how to fulfill their caregiving roles for people living with ADRD after hospital discharge. A-SHIFT has the potential to not only improve care partner preparedness but also help reduce health and service use outcomes for people living with ADRD after hospital discharge.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/45274.

Association of Indication for Hospitalization With Subsequent Amyloid Positron Emission Tomography and Magnetic Resonance Imaging Biomarkers

BACKGROUND

Hospitalization in older age is associated with accelerated cognitive decline, typically preceded by neuropathologic changes. We assess the association between indication for hospitalization and brain neurodegeneration.

METHODS

Included were participants from the Mayo Clinic Study of Aging, a population-based longitudinal study, with ≥1 brain imaging available in those older than 60 years of age between 2004 and 2017. Primary analyses used linear mixed-effects models to assess association of hospitalization with changes in longitudinal trajectory of cortical thinning, amyloid accumulation, and white matter hyperintensities (WMH). Additional analyses were performed with imaging outcomes dichotomized (normal vs abnormal) using Cox proportional hazards regression.

RESULTS

Of 2 480 participants, 1 966 had no hospitalization and 514 had ≥1 admission. Hospitalization was associated with accelerated cortical thinning (annual slope change -0.003 mm [95% confidence interval (CI) -0.005 to -0.001], p = .002), but not amyloid accumulation (0.003 [95% CI -0.001 to 0.006], p = .107), or WMH increase (0.011 cm3 [95% CI -0.001 to 0.023], p = .062). Interaction analyses assessing whether trajectory changes are dependent on admission type (medical vs surgical) found interactions for all outcomes. While surgical hospitalizations were not, medical hospitalizations were associated with accelerated cortical thinning (-0.004 mm [95% CI -0.008 to -0.001, p = .014); amyloid accumulation (0.010, [95% CI 0.002 to 0.017, p = .011), and WMH increase (0.035 cm3 [95% CI 0.012 to 0.058, p = .006). Hospitalization was not associated with developing abnormal cortical thinning (p = .407), amyloid accumulation (p = .596), or WMH/infarctions score (p = .565).

CONCLUSIONS

Medical hospitalizations were associated with accelerated cortical thinning, amyloid accumulation, and WMH increases. These changes were modest and did not translate to increased risk for crossing the abnormality threshold.

The effect of all-cause hospitalization on cognitive decline in older adults: a longitudinal study using databases of the National Health Insurance Service and the memory clinics of a self-run hospital

BACKGROUND

Cognitive decline is common in older adults and imposes a burden on public health. Especially for older adults, hospitalization can be related to decreased physical fitness. This study aimed to investigate the quantitative association between hospitalization and cognitive decline.

METHODS

This was a retrospective cohort study. We performed a longitudinal study by using the combined database from the Korean National Health Insurance Service (NHIS) and memory clinic data of its self-run hospital. We identified whether hospitalized, the number of hospitalizations, and the total hospitalization days through the claim information from the NHIS database. We also identified whether hospitalization was accompanied by delirium or surgery with general anesthesia for subgroup analysis. Primary outcome was the clinical dementia rating-sum of boxes (CDR-SB) score. Secondary outcomes were mini-mental state examination (MMSE) score, clinical dementia rating (CDR) grade, and Korean-instrumental activities of daily living (KIADL) score. Multivariable mixed models were established.

RESULTS

Of the 1810 participants, 1200 experienced hospitalization at least once during the observation period. The increase in CDR-SB was significantly greater in the hospitalized group (β = 1.5083, P < .001). The same results were seen in the total number of hospitalizations (β = 0.0208, P < .001) or the total hospitalization days (β = 0.0022, P < .001) increased. In the group that experienced hospitalization, cognitive decline was also significant in terms of CDR grade (β = 0.1773, P < .001), MMSE score (β = - 1.2327, P < .001), and KIADL score (β = 0.2983, P < .001). Although delirium (β = 0.2983, P < .001) and nonsurgical hospitalization (β = 0.2983, P < .001) were associated with faster cognitive decline, hospitalization without delirium and with surgery were also related to faster cognitive decline than in the no hospitalization group.

CONCLUSION

Cognitive decline was quantitatively related to all-cause hospitalization in older adults. Moreover, hospitalizations without delirium and surgery were also related to cognitive decline. It is vital to prevent various conditions that need hospitalization to avoid and manage cognitive dysfunction.

Is hospitalization a risk factor for cognitive decline in older age adults?

OBJECTIVES

Many studies document cognitive decline following specific types of acute illness hospitalizations (AIH) such as surgery, critical care, or those complicated by delirium. However, cognitive decline may be a complication following all types of AIH. This systematic review will summarize longitudinal observational studies documenting cognitive changes following AIH in the majority admitted population and conduct meta-analysis (MA) to assess the quantitative effect of AIH on post-hospitalization cognitive decline (PHCD).

METHODS

We followed Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Selection criteria were defined to identify studies of older age adults exposed to AIH with cognitive measures. 6566 titles were screened. 46 reports were reviewed qualitatively, of which seven contributed data to the MA. Risk of bias was assessed using the Newcastle-Ottawa Scale.

RESULTS

The qualitative review suggested increased cognitive decline following AIH, but several reports were particularly vulnerable to bias. Domain-specific outcomes following AIH included declines in memory and processing speed. Increasing age and the severity of illness were the most consistent risk factors for PHCD. PHCD was supported by MA of seven eligible studies with 41,453 participants (Cohen's d = -0.25, 95% CI [-0.02, -0.49] I² 35%).

CONCLUSIONS

There is preliminary evidence that AIH exposure accelerates or triggers cognitive decline in the elderly patient. PHCD reported in specific contexts could be subsets of a larger phenomenon and caused by overlapping mechanisms. Future research must clarify the trajectory, clinical significance, and etiology of PHCD: a priority in the face of an aging population with increasing rates of both cognitive impairment and hospitalization.

Patterns of Symptom Tracking by Caregivers and Patients With Dementia and Mild Cognitive Impairment: Cross-sectional Study

BACKGROUND

Individuals with dementia and mild cognitive impairment (MCI) experience a wide variety of symptoms and challenges that trouble them. To address this heterogeneity, numerous standardized tests are used for diagnosis and prognosis. myGoalNav Dementia is a web-based tool that allows individuals with impairments and their caregivers to identify and track outcomes of greatest importance to them, which may be a less arbitrary and more sensitive way of capturing meaningful change.

OBJECTIVE

We aim to explore the most frequent and important symptoms and challenges reported by caregivers and people with dementia and MCI and how this varies according to disease severity.

METHODS

This cross-sectional study involved 3909 web-based myGoalNav users (mostly caregivers of people with dementia or MCI) who completed symptom profiles between 2006 and 2019. To make a symptom profile, users selected their most personally meaningful or troublesome dementia-related symptoms to track over time. Users were also asked to rank their chosen symptoms from least to most important, which we called the symptom potency. As the stage of disease for these web-based users was unknown, we applied a supervised staging algorithm, previously trained on clinician-derived data, to classify each profile into 1 of 4 stages: MCI and mild, moderate, and severe dementia. Across these stages, we compared symptom tracking frequency, symptom potency, and the relationship between frequency and potency.

RESULTS

Applying the staging algorithm to the 3909 user profiles resulted in 917 (23.46%) MCI, 1596 (40.83%) mild dementia, 514 (13.15%) moderate dementia, and 882 (22.56%) severe dementia profiles. We found that the most frequent symptoms in MCI and mild dementia profiles were similar and comprised early hallmarks of dementia (eg, recent memory and language difficulty). As the stage increased to moderate and severe, the most frequent symptoms were characteristic of loss of independent function (eg, incontinence) and behavioral problems (eg, aggression). The most potent symptoms were similar between stages and generally reflected disruptions in everyday life (eg, problems with hobbies or games, travel, and looking after grandchildren). Symptom frequency was negatively correlated with potency at all stages, and the strength of this relationship increased with increasing disease severity.

CONCLUSIONS

Our results emphasize the importance of patient-centricity in MCI and dementia studies and illustrate the valuable real-world evidence that can be collected with digital tools. Here, the most frequent symptoms across the stages reflected our understanding of the typical disease progression. However, the symptoms that were ranked as most personally important by users were generally among the least frequently selected. Through individualization, patient-centered instruments such as myGoalNav can complement standardized measures by capturing these infrequent but potent outcomes.

ATP Synthase and Mitochondrial Bioenergetics Dysfunction in Alzheimer's Disease

Alzheimer's Disease (AD) is the most common neurodegenerative disorder in our society, as the population ages, its incidence is expected to increase in the coming decades. The etiopathology of this disease still remains largely unclear, probably because of the highly complex and multifactorial nature of AD. However, the presence of mitochondrial dysfunction has been broadly described in AD neurons and other cellular populations within the brain, in a wide variety of models and organisms, including post-mortem humans. Mitochondria are complex organelles that play a crucial role in a wide range of cellular processes, including bioenergetics. In fact, in mammals, including humans, the main source of cellular ATP is the oxidative phosphorylation (OXPHOS), a process that occurs in the mitochondrial electron transfer chain (ETC). The last enzyme of the ETC, and therefore the ulterior generator of ATP, is the ATP synthase. Interestingly, in mammalian cells, the ATP synthase can also degrade ATP under certain conditions (ATPase), which further illustrates the crucial role of this enzyme in the regulation of cellular bioenergetics and metabolism. In this collaborative review, we aim to summarize the knowledge of the presence of dysregulated ATP synthase, and of other components of mammalian mitochondrial bioenergetics, as an early event in AD. This dysregulation can act as a trigger of the dysfunction of the organelle, which is a clear component in the etiopathology of AD. Consequently, the pharmacological modulation of the ATP synthase could be a potential strategy to prevent mitochondrial dysfunction in AD.

Association of Infection-Related Hospitalization With Cognitive Impairment Among Nursing Home Residents

Importance

Hospitalizations for infections among nursing home (NH) residents remain common despite national initiatives to reduce them. Cognitive impairment, which markedly affects quality of life and caregiving needs, has been associated with hospitalizations, but the association between infection-related hospitalizations and long-term cognitive function among NH residents is unknown.

Objective

To examine whether there are changes in cognitive function before vs after infection-related hospitalizations among NH residents.

Design, Setting, and Participants

This cohort study used data from the Minimum Data Set 3.0 linked to Medicare hospitalization data from 2011 to 2017 for US nursing home residents aged 65 years or older who had experienced an infection-related hospitalization and had at least 2 quarterly Minimum Data Set assessments before and 4 or more after the infection-related hospitalization. Analyses were performed from September 1, 2019, to December 21, 2020.

Exposure

Infection-related hospitalization lasting 1 to 14 days.

Main Outcomes and Measures

Using an event study approach, associations between infection-related hospitalizations and quarterly changes in cognitive function among NH residents were examined overall and by sex, age, Alzheimer disease and related dementias (ADRD) diagnosis, and sepsis vs other infection-related diagnoses. Resident-level cognitive function was measured using the Cognitive Function Scale (CFS), with scores ranging from 1 (intact) to 4 (severe cognitive impairment).

Results

Of the sample of 20 698 NH residents, 71.0% were women and 82.6% were non-Hispanic White individuals; the mean (SD) age at the time of transfer to the hospital was 82 (8.5) years. The mean CFS score was 2.17, and the prevalence of severe cognitive impairment (CFS score, 4) was 9.0%. During the first quarter after an infection-related hospitalization, residents experienced a mean increase of 0.06 points in CFS score (95% CI, 0.05-0.07 points; P < .001), or 3%. The increase in scores was greatest among residents aged 85 years or older vs younger residents by approximately 0.022 CFS points (95% CI, 0.004-0.040 points; P < .05). The prevalence of severe cognitive impairment increased by 1.6 percentage points (95% CI, 1.2-2.0 percentage points; P < .001), or 18%; the increases were observed among individuals with ADRD but not among those without it. After an infection-related hospitalization, cognition among residents who had experienced sepsis declined more than for residents who had not by about 0.02 CFS points (95% CI, 0.00-0.04 points; P < .05). All observed differences persisted without an accelerated rate of decline for at least 6 quarters after infection-related hospitalization. No differences were observed by sex.

Conclusions and Relevance

In this cohort study, infection-related hospitalization was associated with immediate and persistent cognitive decline among nursing home residents, with the largest increase in CFS scores among older residents, those with ADRD, and those who had experienced sepsis. Identification of NH residents at risk of worsened cognition after an infection-related hospitalization may help to ensure that their care needs are addressed to prevent further cognitive decline.

Associations Between Personality Traits and Cognitive Resilience in Older Adults

OBJECTIVES

The goal of this paper was to examine associations between personality traits and resilience to neuropathologic burden.

METHOD

Using data from the Religious Orders Study and the Rush Memory and Aging Project, we identified a total of 1,375 participants with personality, cognitive, and post-mortem neuropathology data. We regressed cognition onto pathology and extracted the residuals as an indicator of cognitive resilience. We then modeled the effect of Big Five personality traits on cognitive resilience, adjusting for demographics, APOE status, medical comorbidities, and cognitive activity. The analytic plan was preregistered prior to data access or analysis, and all scripts and outputs are available online.

RESULTS

Higher neuroticism was associated with greater vulnerability to pathology. Results from exploratory analyses suggest that higher conscientiousness was associated with less cognitive decline relative to the amount of pathology, or greater resilience. Education and cognitive activity did not moderate these associations.

DISCUSSION

Personality may have a pathoplastic effect on neuropathology, as low neuroticism and high conscientiousness are associated with better function despite neuropathologic burden.

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.