Relationships between sleep quality and brain volume, metabolism, and amyloid deposition in late adulthood

Cardiorespiratory Fitness Modifies Influence of Sleep Problems on Cerebrospinal Fluid Biomarkers in an At-Risk Cohort

BACKGROUND

Previous studies indicate that cardiorespiratory fitness (CRF) and sleep are each favorably associated with Alzheimer's disease (AD) pathophysiology, including reduced amyloid-β (Aβ) and tau pathology. However, few studies have examined CRF and sleep in the same analysis.

OBJECTIVE

To examine the relationship between sleep and core AD cerebrospinal fluid (CSF) biomarkers among at-risk healthy late-middle-aged adults and determine whether CRF modifies this association.

METHODS

Seventy-four adults (age = 64.38±5.48, 68.9% female) from the Wisconsin Registry for Alzheimer's Prevention participated. Sleep was evaluated using the Medical Outcomes Study Sleep Scale, specifically the Sleep Problems Index I (SPI), which incorporates domains of sleep disturbance, somnolence, sleep adequacy, and shortness of breath. Higher scores indicate greater sleep problems. To assess CRF, participants underwent a graded exercise test. CSF was collected via lumbar puncture, from which Aβ42, total-tau (t-tau), and phosphorylated-tau (p-tau) were immunoassayed. Regression analyses examined the association between SPI and CSF biomarkers, and the interaction between SPI and CRF on these same biomarkers, adjusting for relevant covariates.

RESULTS

Higher SPI scores were associated with greater p-tau (p = 0.027) and higher t-tau/Aβ42 (p = 0.021) and p-tau/Aβ42 (p = 0.009) ratios. Analyses revealed significant SPI*CRF interactions for t-tau (p = 0.016), p-tau (p = 0.008), and p-tau/Aβ42 (p = 0.041); with a trend for t-tau/Aβ42 (p = 0.061). Specifically, the relationship between poorer sleep and these biomarkers was significant among less fit individuals, but not among those who were more fit.

CONCLUSION

In a late-middle-aged at-risk cohort, CRF attenuated the association between poor sleep and levels of select CSF biomarkers. This suggests fitness may play an important role in preventing AD by protecting against pathology, even in impaired sleep.

Highlighting the Role of Cognitive and Brain Reserve in the Substance use Disorder Field

BACKGROUND

Cognitive reserve (CR) refers to the ability of an individual to cope with brain pathology remaining free of cognitive symptoms. This protective factor has been related to compensatory and more efficient brain mechanisms involved in resisting brain damage. For its part, Brain reserve (BR) refers to individual differences in the structural properties of the brain which could also make us more resilient to suffer from neurodegenerative and mental diseases.

OBJECTIVE

This review summarizes how this construct, mainly mediated by educational level, occupational attainment, physical and mental activity, as well as successful social relationships, has gained scientific attention in the last years with regard to diseases, such as neurodegenerative diseases, stroke or traumatic brain injury. Nevertheless, although CR has been studied in a large number of disorders, few researches have addressed the role of this concept in drug addiction.

METHODS

We provide a selective overview of recent literature about the role of CR and BR in preventing substance use onset. Likewise, we will also discuss how variables involved in CR (healthy leisure, social support or job-related activities, among others) could be trained and included as complementary activities of substance use disorder treatments.

RESULTS

Evidence about this topic suggests a preventive role of CR and BR on drug use onset and when drug addiction is established, these factors led to less severe addiction-related problems, as well as better treatment outcomes.

CONCLUSION

CR and BR are variables not taken yet into account in drug addiction. However, they could give us a valuable information about people at risk, as well as patient's prognosis.

A manual-based intervention for carers of people with dementia and sleep disturbances: an acceptability and feasibility RCT

BACKGROUND

It has been estimated that between 25% and 40% of people living with dementia suffer from sleep disturbances, and there are currently no known effective treatments. Sleep disturbances may be the direct result of dementia or due to other comorbidities, such as pain and limited mobility. If carers' sleep is also disturbed, carers too can become tired and stressed, and this sometimes results in the breakdown of care in the home.

OBJECTIVES

To design an evidence-based manualised non-pharmacological therapy for sleep disturbances and test it for feasibility and acceptability.

DESIGN

A single-blind, randomised, parallel-group feasibility trial, with participants randomised 2 : 1 to intervention or treatment as usual (TAU).

SETTING

Five memory services in two London NHS trusts and Join Dementia Research (JDR).

PARTICIPANTS

The study recruited people with dementia and sleep disturbances (who scored ≥ 4 on at least one question on the Sleep Disorders Inventory) and their primary family carers.

INTERVENTION

All participants were given an Actiwatch (CamNtech Ltd, Cambridge, UK) to wear to record their sleep patterns for 2 weeks before randomisation. The intervention group received Dementia RElAted Manual for Sleep; STrAtegies for RelaTives (DREAMS START). This was designed as a six-session, manual-based intervention for carers of people with dementia, delivered by trained and clinically supervised psychology graduates, based on evidence about managing sleep disturbance in people with dementia. It uses the structure of a previous manual-based treatment, STrAtegies for RelaTives (START). Family carers were consulted about structure, content and design. Sessions were interactive, and each involved techniques, tasks to practise between sessions, relaxation and a recapitulation on the previous session. The sessions covered understanding sleep and dementia, making a plan (incorporating information from Actiwatch read-outs and a light box to increase light), daytime activity and routine, difficult night-time behaviours, taking care of your own (carer's) sleep and using the strategies in the future. Carers kept their own manual, light box and relaxation recordings post intervention.

RANDOMISATION AND BLINDING

A statistician created an electronic randomisation list, stratified by site, using random permuted blocks. Those assessing the outcome were blinded to allocation; participants were not blinded.

MAIN OUTCOME MEASURES

Outcomes were assessed at 3 months. (1) Feasibility, defined as the percentage of eligible people who consented to the study recruitment, with an expected value of 50% [95% confidence interval (CI) 41% to 59%]. (2) Acceptability, defined as the percentage of intervention group participants attending ≥ 4 intervention sessions, with an expected value of 75% (95% CI 59% to 87%). The predetermined criterion for progression to the main trial was acceptability of ≥ 70%.

RESULTS

Of 95 eligible patients referred, 63 (66%, 95% CI 56% to 76%) consented between 4 August 2016 and 24 March 2017: 61 from memory clinics and two from JDR. Of these, 62 participants (65%, 95% CI 55% to 75%) were randomised: 42 to the intervention arm and 20 to the TAU arm. Thirty-seven out of 42 participants (88%, 95% CI 75% to 96%) adhered to the intervention.

CONCLUSIONS

The results show that the randomised controlled trial is feasible and that the intervention is acceptable. A higher than expected proportion of eligible patients referred consented to the study and adhered to the intervention.

LIMITATIONS

Participants were not blinded and were recruited only in London.

FUTURE WORK

The results of this trial indicate that a future efficacy trial is warranted.

TRIAL REGISTRATION

Current Controlled Trials ISCTRN36983298.

FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 71. See the NIHR Journals Library website for further project information. Funding was also provided by Camden and Islington NHS Foundation Trust and Barnet, Enfield and Haringey Mental Health NHS Trust to pay for excess treatment costs from therapist training and supervision and intervention delivery.

Disorders of Body Weight, Sleep and Circadian Rhythm as Manifestations of Hypothalamic Dysfunction in Alzheimer's Disease

While cognitive decline and memory loss are the major clinical manifestations of Alzheimer’s disease (AD), they are now recognized as late features of the disease. Recent failures in clinical drug trials highlight the importance of evaluating and treating patients with AD as early as possible and the difficulties in developing effective therapies once the disease progresses. Since the pathological hallmarks of AD including the abnormal aggregation of amyloid-beta (Aβ) and tau can occur decades before any significant cognitive decline in the preclinical stage of AD, it is important to identify the earliest clinical manifestations of AD and elucidate their underlying cellular and molecular mechanisms. Importantly, metabolic and non-cognitive manifestations of AD such as weight loss and alterations of peripheral metabolic signals can occur before the onset of cognitive symptoms and worsen with disease progression. Accumulating evidence suggests that the major culprit behind these early metabolic and non-cognitive manifestations of AD is AD pathology causing dysfunction of the hypothalamus, a brain region critical for integrating peripheral signals with essential homeostatic physiological functions. Here, we aim to highlight recent developments that address the role of AD pathology in the development of hypothalamic dysfunction associated with metabolic and non-cognitive manifestations seen in AD. Understanding the mechanisms underlying hypothalamic dysfunction in AD could give key new insights into the development of novel biomarkers and therapeutic targets.

The Glymphatic System in Diabetes-Induced Dementia

The glymphatic system has emerged as an important player in central nervous system (CNS) diseases, by regulating the vasculature impairment, effectively controlling the clearance of toxic peptides, modulating activity of astrocytes, and being involved in the circulation of neurotransmitters in the brain. Recently, several studies have indicated decreased activity of the glymphatic pathway under diabetes conditions such as in insulin resistance and hyperglycemia. Furthermore, diabetes leads to the disruption of the blood-brain barrier and decrease of apolipoprotein E (APOE) expression and the secretion of norepinephrine in the brain, involving the impairment of the glymphatic pathway and ultimately resulting in cognitive decline. Considering the increased prevalence of diabetes-induced dementia worldwide, the relationship between the glymphatic pathway and diabetes-induced dementia should be investigated and the mechanisms underlying their relationship should be discussed to promote the development of an effective therapeutic approach in the near future. Here, we have reviewed recent evidence for the relationship between glymphatic pathway dysfunction and diabetes. We highlight that the enhancement of the glymphatic system function during sleep may be beneficial to the attenuation of neuropathology in diabetes-induced dementia. Moreover, we suggest that improving glymphatic system activity may be a potential therapeutic strategy for the prevention of diabetes-induced dementia.

Disturbed sleep and diabetes: A potential nexus of dementia risk

Type 2 diabetes (T2D) and sleep disturbance (e.g., insomnia, sleep-disordered breathing) are prevalent conditions among older adults that are associated with cognitive decline and dementia, including Alzheimer's disease (AD). Importantly, disturbed sleep is associated with alterations in insulin sensitivity and glucose metabolism, and may increase the risk of T2D, and T2D-related complications (e.g., pain, nocturia) can negatively affect sleep. Despite these associations, little is known about how interactions between T2D and sleep disturbance might alter cognitive trajectories or the pathological changes that underlie dementia. Here, we review links among T2D, sleep disturbance, cognitive decline and dementia-including preclinical and clinical AD-and identify gaps in the literature, that if addressed, could have significant implications for the prevention of poor cognitive outcomes.

Why could meditation practice help promote mental health and well-being in aging?

Psycho-affective states or traits such as stress, depression, anxiety and neuroticism are known to affect sleep, cognition and mental health and well-being in aging populations and to be associated with increased risk for Alzheimer's disease (AD). Mental training for stress reduction and emotional and attentional regulation through meditation practice might help reduce these adverse factors. So far, studies on the impact of meditation practice on brain and cognition in aging are scarce and have limitations but the findings are encouraging, showing a positive effect of meditation training on cognition, especially on attention and memory, and on brain structure and function especially in frontal and limbic structures and insula. In line with this, we showed in a pilot study that gray matter volume and/or glucose metabolism was higher in six older adult expert meditators compared to 67 age-matched controls in the prefrontal, anterior and posterior cingulate cortex, insula and temporo-parietal junction. These preliminary findings are important in the context of reserve and brain maintenance as they suggest that long-term meditation practice might help preserve brain structure and function from progressive age-related decline. Further studies are needed to confirm these results with larger samples and in randomized controlled trials and to investigate the mechanisms underlying these meditation-related effects. The European Commission-funded project Silver Santé Study will address these challenges by studying 316 older adults including 30 expert meditators and 286 meditation-naïve participants (either cognitively normal or with subjective cognitive decline). Two randomized controlled trials will be conducted to assess the effects of 2-month and 18-month meditation, English learning or health education training programs (versus a passive control) on behavioral, sleep, blood sampling and neuroimaging measures. This European research initiative illustrates the progressive awareness of the benefit of such non-pharmacological approaches in the prevention of dementia and the relevance of taking into account the psycho-affective dimension in endeavoring to improve mental health and well-being of older adults.

Impact of sex steroids and reproductive stage on sleep-dependent memory consolidation in women

Age and sex are two of the three major risk factors for Alzheimer's disease (ApoE-e4 allele is the third), with women having a twofold greater risk for Alzheimer's disease after the age of 75 years. Sex differences have been shown across a wide range of cognitive skills in young and older adults, and evidence supports a role for sex steroids, especially estradiol, in protecting against the development of cognitive decline in women. Sleep may also be a protective factor against age-related cognitive decline, since specific electrophysiological sleep events (e.g. sleep spindle/slow oscillation coupling) are critical for offline memory consolidation. Furthermore, studies in young women have shown fluctuations in sleep events and sleep-dependent memory consolidation during different phases of the menstrual cycle that are associated with the levels of sex steroids. An under-appreciated possibility is that there may be an important interaction between these two protective factors (sex steroids and sleep) that may play a role in daily fluctuations in cognitive processing, in particular memory, across a woman's lifespan. Here, we summarize the current knowledge of sex steroid-dependent influences on sleep and cognition across the lifespan in women, with special emphasis on sleep-dependent memory processing. We further indicate gaps in knowledge that require further experimental examination in order to fully appreciate the complex and changing landscape of sex steroids and cognition. Lastly, we propose a series of testable predictions for how sex steroids impact sleep events and sleep-dependent cognition across the three major reproductive stages in women (reproductive years, menopause transition, and post-menopause).

Sleep and cognitive decline: A prospective nondemented elderly cohort study

OBJECTIVE

To investigate sleep disturbances that induce cognitive changes over 4 years in nondemented elderlies.

METHODS

Data were acquired from a nationwide, population-based, prospective cohort of Korean elderlies (2,238 normal cognition [NC] and 655 mild cognitive impairment [MCI]). At baseline and 4-year follow-up assessments, sleep-related parameters (midsleep time, sleep duration, sleep latency, subjective sleep quality, sleep efficiency, and daytime dysfunction) and cognitive status were measured using the Pittsburgh Sleep Quality Index and Consortium to Establish a Registry for Alzheimer's Disease Assessment, respectively. We used logistic regression models adjusted for covariates including age, sex, education, apolipoprotein E genotype, Geriatric Depression Scale, Cumulative Illness Rating Scale, and physical activity.

RESULTS

In participants with NC, long sleep latency (>30 minutes), long sleep duration (≥7.95 hours), and late midsleep time (after 3:00 am) at baseline were related to the risk of cognitive decline at 4-year follow-up assessment; odds ratio (OR) was 1.40 for long sleep latency, 1.67 for long sleep duration, and 0.61 for late midsleep time. These relationships remained significant when these variables maintained their status throughout the follow-up period. Newly developed long sleep latency also doubled the risk of cognitive decline. In those with MCI, however, only long sleep latency reduced the chance of reversion to NC (OR = 0.69).

INTERPRETATION

As early markers of cognitive decline, long sleep latency can be used for elderlies with NC or MCI, whereas long sleep duration and relatively early sleep time might be used for cognitively normal elderlies only. Ann Neurol 2018;83:472-482.

Caregiver-Reported Sleep Disturbances Are Associated With Behavioral and Psychological Symptoms in an Asian Elderly Cohort With Cognitive Impairment-No Dementia

OBJECTIVE

Sleep disturbances were found to be associated with more behavioral and psychological symptoms (BPS) in early patients with Alzheimer's disease (AD). However, data on preclinical stages of dementia are lacking. Hence, the present study sought to investigate the association between sleep disturbances and BPS in dementia-free elderly with varying severity of cognitive impairment in an Asian sample.

METHODS

Community-living elderly were recruited and administered a comprehensive cognitive battery (vascular dementia battery [VDB]) and the Neuropsychiatric Inventory to assess symptoms of sleep disturbances and BPS. Severity of cognitive impairment was diagnosed and classified as no cognitive impairment (NCI), cognitive impairment-no dementia (CIND) -mild (1-2 impaired domains on the VDB), and CIND-moderate (≥3 impaired domains on the VDB). Analysis of variance was conducted to assess the associations between the presence of sleep disturbances and BPS scores in each diagnostic group. Logistic regression was used to examine whether the coexistence of sleep disturbances and other BPS was associated with CIND-moderate, which is known to carry a higher risk of progression to AD.

RESULTS

Among 839 elderly, 79 (9.4%) reported sleep disturbances. Participants with sleep disturbances had higher total BPS burden than those without among CIND participants but not in NCIs. Furthermore, CIND-moderate participants with sleep disturbances had more delusions, hallucinations, anxiety, depression, irritability, aberrant motor behavior, and appetite change ( P < .05). The presence of both sleep disturbances and other BPS was associated with CIND-moderate (odds ratio: 2.5, 95% confidence interval: 1.1-5.5).

CONCLUSIONS

Sleep disturbances are associated with higher total BPS burden and specific BPS among elderly patients with cognitive impairment, particularly those with CIND moderate, which carries higher risk of developing dementia.

Altered Regional Homogeneity in Chronic Insomnia Disorder with or without Cognitive Impairment

BACKGROUND AND PURPOSE

Many studies have shown that insomnia is an independent factor in cognitive impairment, but the involved neurobiological mechanisms remain unclear. We used regional homogeneity to explore the specific neurobiologic indicators of chronic insomnia disorder with mild cognitive impairment.

MATERIALS AND METHODS

Thirty-nine patients with insomnia were divided into a group with and without cognitive impairment; we also included a control group (n = 28). Abnormalities in brain functional activity were identified by comparing the regional homogeneity values for each brain region among the groups.

RESULTS

Subjective insomnia scores were negatively correlated with cognitive impairment after controlling for age, sex, and educational effects. Regions with significant differences in regional homogeneity values in the 3 groups were concentrated in the right medial prefrontal cortex, the right superior frontal gyrus, and the left superior occipital gyrus. Meanwhile, subjective insomnia scores were negatively correlated with the strength of the decreased regional homogeneity in the right medial prefrontal cortex. The increased regional homogeneity value in the right superior frontal gyrus was positively correlated with the Montreal Cognitive Assessment score in patients.

CONCLUSIONS

Our results indicate that decreased regional homogeneity values in the medial prefrontal cortex and increased regional homogeneity values in the cuneus may be important neurobiologic indicators of chronic insomnia disorder and accompanying cognitive impairment. Overall, our study described the regional homogeneity of the whole brain in chronic insomnia disorder with mild cognitive impairment and could be the basis for future studies.

Genetic variation in Aquaporin-4 moderates the relationship between sleep and brain Aβ-amyloid burden

The glymphatic system is postulated to be a mechanism of brain Aβ-amyloid clearance and to be most effective during sleep. Ablation of the astrocytic end-feet expressed water-channel protein, Aquaporin-4, in mice, results in impairment of this clearance mechanism and increased brain Aβ-amyloid deposition, suggesting that Aquaporin-4 plays a pivotal role in glymphatic function. Currently there is a paucity of literature regarding the impact of AQP4 genetic variation on sleep, brain Aβ-amyloid burden and their relationship to each other in humans. To address this a cross-sectional observational study was undertaken in cognitively normal older adults from the Australian Imaging, Biomarkers and Lifestyle (AIBL) study. Genetic variants in AQP4 were investigated with respect to self-reported Pittsburgh Sleep Quality Index sleep parameters, positron emission tomography derived brain Aβ-amyloid burden and whether these genetic variants moderated the sleep-Aβ-amyloid burden relationship. One AQP4 variant, rs72878776, was associated with poorer overall sleep quality, while several SNPs moderated the effect of sleep latency (rs491148, rs9951307, rs7135406, rs3875089, rs151246) and duration (rs72878776, rs491148 and rs2339214) on brain Aβ-amyloid burden. This study suggests that AQP4 genetic variation moderates the relationship between sleep and brain Aβ-amyloid burden, which adds weight to the proposed glymphatic system being a potential Aβ-amyloid clearance mechanism and suggests that AQP4 genetic variation may impair this function. Further, AQP4 genetic variation should be considered when interpreting sleep-Aβ relationships.

Healthy minds from 0-100 years: Optimising the use of European brain imaging cohorts ("Lifebrain")

The main objective of "Lifebrain" is to identify the determinants of brain, cognitive and mental (BCM) health at different stages of life. By integrating, harmonising and enriching major European neuroimaging studies across the life span, we will merge fine-grained BCM health measures of more than 5,000 individuals. Longitudinal brain imaging, genetic and health data are available for a major part, as well as cognitive and mental health measures for the broader cohorts, exceeding 27,000 examinations in total. By linking these data to other databases and biobanks, including birth registries, national and regional archives, and by enriching them with a new online data collection and novel measures, we will address the risk factors and protective factors of BCM health. We will identify pathways through which risk and protective factors work and their moderators. Exploiting existing European infrastructures and initiatives, we hope to make major conceptual, methodological and analytical contributions towards large integrative cohorts and their efficient exploitation. We will thus provide novel information on BCM health maintenance, as well as the onset and course of BCM disorders. This will lay a foundation for earlier diagnosis of brain disorders, aberrant development and decline of BCM health, and translate into future preventive and therapeutic strategies. Aiming to improve clinical practice and public health we will work with stakeholders and health authorities, and thus provide the evidence base for prevention and intervention.

Excessive Sleepiness and Longer Nighttime in Bed Increase the Risk of Cognitive Decline in Frail Elderly Subjects: The MAPT-Sleep Study

Objective: To identify self-reported sleep-wake disturbances that increase the risk of cognitive decline over 1-year follow-up in frail participants.

Background: Risk factors for cognitive impairment need to be better identified especially at earliest stages of the pathogenesis. Sleep-wake disturbances may be critical factors to consider and were thus being assessed in this at-risk population for cognitive decline.

Methods: Frail elderly participants aged ≥70 years were selected from a subsample of the Multi-domain Alzheimer Preventive Trial (MAPT) for a sleep assessment (MAPT-sleep study) at 18-month follow-up (M18). Sleep-wake disturbances were evaluated using a clinical interview (duration of daytime and nighttime sleep, time in bed, number of naps, and presence of clinically-defined sleep disorders) and numerous validated questionnaires [Epworth Sleepiness Scale for excessive daytime sleepiness (EDS), Insomnia Severity Scale and Berlin Questionnaire]. Cognitive decline was defined as a difference between the MMSE and cognitive composite scores at M24 and M36 that was ranked in the lowest decile. Multivariate logistic regression models adjusted for several potential confounding factors were performed.

Results: Among the 479 frail participants, 63 developed MMSE-cognitive decline and 50 cognitive composite score decrease between M24 and M36. Subjects with EDS had an increased risk of MMSE decline (OR = 2.46; 95% CI [1.28; 4.71], p = 0.007). A longer time spent in bed during night was associated with cognitive composite score decline (OR = 1.32 [1.03; 1.71], p = 0.03). These associations persisted when controlling for potential confounders. Patients with MMSE score decline and EDS had more naps, clinically-defined REM-sleep Behavior Disorder, fatigue and insomnia symptoms, while patients with cognitive composite score decline with longer time in bed had increased 24-h total sleep time duration but with higher wake time after onset.

Conclusions: The risk of cognitive decline is higher in frailty subjects with EDS and longer nighttime in bed. Early detection of sleep-wake disturbances might help identifying frail subjects at risk of cognitive decline to further propose sleep health strategies to prevent cognitive impairment.

http://www.clinicaltrials.gov NCT00672685; Date of registration May, 2nd 2008.

Genetic, Transcriptome, Proteomic, and Epidemiological Evidence for Blood-Brain Barrier Disruption and Polymicrobial Brain Invasion as Determinant Factors in Alzheimer's Disease

Diverse pathogens are detected in Alzheimer's disease (AD) brains. A bioinformatics survey showed that AD genome-wide association study (GWAS) genes (localized in bone marrow, immune locations and microglia) relate to multiple host/pathogen interactomes (Candida albicans, Cryptococcus neoformans, Bornavirus, Borrelia burgdorferri, cytomegalovirus, Ebola virus, HSV-1, HERV-W, HIV-1, Epstein-Barr, hepatitis C, influenza, Chlamydia pneumoniae, Porphyrymonas gingivalis, Helicobacter pylori, Toxoplasma gondii, Trypanosoma cruzi). These interactomes also relate to the AD hippocampal transcriptome and to plaque or tangle proteins. Upregulated AD hippocampal genes match those upregulated by multiple bacteria, viruses, fungi, or protozoa in immunocompetent cells. AD genes are enriched in GWAS datasets reflecting pathogen diversity, suggesting selection for pathogen resistance, as supported by the old age of AD patients, implying resistance to earlier infections. APOE4 is concentrated in regions of high parasitic burden and protects against childhood tropical infections and hepatitis C. Immune/inflammatory gain of function applies to APOE4, CR1, and TREM2 variants. AD genes are also expressed in the blood-brain barrier (BBB), which is disrupted by AD risk factors (age, alcohol, aluminum, concussion, cerebral hypoperfusion, diabetes, homocysteine, hypercholesterolemia, hypertension, obesity, pesticides, pollution, physical inactivity, sleep disruption, smoking) and by pathogens, directly or via olfactory routes to basal-forebrain BBB control centers. The BBB benefits from statins, NSAIDs, estrogen, melatonin, memantine, and the Mediterranean diet. Polymicrobial involvement is supported by upregulation of bacterial, viral, and fungal sensors/defenders in the AD brain, blood, or cerebrospinal fluid. AD serum amyloid-β autoantibodies may attenuate its antimicrobial effects favoring microbial survival and cerebral invasion leading to activation of neurodestructive immune/inflammatory processes, which may also be augmented by age-related immunosenescence. AD may thus respond to antibiotic, antifungal, or antiviral therapy.

Do Older Adults Need Sleep? A Review of Neuroimaging, Sleep, and Aging Studies

PURPOSE OF REVIEW

Sleep habits, sleep physiology, and sleep disorders change with increasing age. However, there is a longstanding debate regarding whether older adults need sleep to maintain health and daily functioning (reduced-sleep-need view). An alternative possibility is that all older adults need sleep, but that many older adults have lost the ability to obtain restorative sleep (reduced-sleep-ability view). Prior research using behavioral and polysomnography outcomes has not definitively disentangled the reduced-sleep-need and reduced-sleep-ability views. Therefore, this review examines the neuroimaging literature to determine whether age-related changes in sleep cause-or are caused by-age-related changes in brain structure, function, and pathology.

RECENT FINDINGS

In middle-aged and older adults, poorer sleep quality, greater nighttime hypoxia, and shorter sleep duration related to cortical thinning in frontal regions implicated in slow wave generation, in frontoparietal networks implicated in cognitive control, and in hippocampal regions implicated in memory consolidation. Furthermore, poor sleep quality was associated with higher amyloid burden and decreased connectivity in the default mode network, a network that is disrupted in the pathway to Alzheimer's disease.

SUMMARY

All adults need sleep, but cortical thinning and amyloidal deposition with advancing age may weaken the brain's ability to produce restorative sleep. Therefore, sleep in older adults may not always support identical functions for physical, mental, and cognitive health as in young adults.

The Relationship Between Apolipoprotein ε4 Carrier Status and Sleep Characteristics in Cognitively Normal Older Adults

The apolipoprotein (APOE) ε4 allele, a well-described genetic risk factor for late-onset Alzheimer disease (AD), is associated with sleep disturbances even in cognitively normal older adults, although it is not clear whether this association is independent of sleep apnea. We sought to extend previous studies by examining whether cognitively normal older adults without self-reported sleep apnea who carry the APOE ε4 allele have altered sleep characteristics compared to noncarriers. Data from N = 36 (APOE ε4 carriers [n = 9], noncarriers [n = 27]) cognitively normal older adults (Clinical Dementia Rating [CDR] scale = 0) without self-reported sleep apnea were used for these analyses. Participants wore an actigraph for 7 days to determine sleep characteristics. The Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) were used to assess sleep quality and daytime sleepiness, respectively. The APOE ε4 carriers had a higher number of awakenings compared to the noncarriers ( P = .02). There was no significant difference in the PSQI global score and the ESS; however, the PSQI subcomponent of daily disturbances was significantly higher in APOE ε4 carriers ( P = .03), indicating increased daytime dysfunction is related to disrupted sleep. This study provides evidence that individuals who are cognitively normal and genetically at risk of AD may have disrupted sleep. These findings are consistent with prior studies and suggest that sleep disruption may be present in the presymptomatic stages of AD.

Reduced age-associated brain changes in expert meditators: a multimodal neuroimaging pilot study

Aging is associated with progressive cerebral volume and glucose metabolism decreases. Conditions such as stress and sleep difficulties exacerbate these changes and are risk factors for Alzheimer's disease. Meditation practice, aiming towards stress reduction and emotion regulation, can downregulate these adverse factors. In this pilot study, we explored the possibility that lifelong meditation practice might reduce age-related brain changes by comparing structural MRI and FDG-PET data in 6 elderly expert meditators versus 67 elderly controls. We found increased gray matter volume and/or FDG metabolism in elderly expert meditators compared to controls in the bilateral ventromedial prefrontal and anterior cingulate cortex, insula, temporo-parietal junction, and posterior cingulate cortex /precuneus. Most of these regions were also those exhibiting the strongest effects of age when assessed in a cohort of 186 controls aged 20 to 87 years. Moreover, complementary analyses showed that these changes were still observed when adjusting for lifestyle factors or using a smaller group of controls matched for education. Pending replication in a larger cohort of elderly expert meditators and longitudinal studies, these findings suggest that meditation practice could reduce age-associated structural and functional brain changes.

Sleep changes without medial temporal lobe or brain cortical changes in community-dwelling individuals with subjective cognitive decline

INTRODUCTION

Subjective cognitive decline (SCD) is a risk factor for mild cognitive impairment (MCI) and Alzheimer's disease (AD). Although sleep has been shown to be altered in MCI and AD, little is known about sleep in SCD.

METHODS

Seventy cognitively normal community-dwelling participants were classified as SCD (32) or controls (38) using the Subjective Cognitive Decline Questionnaire. Sleep was assessed using actigraphy and diaries. FreeSurfer was used for performing medial temporal lobes (MTLs) and brain cortical parcellation of 3T magnetic resonance images. Multiple regression models were used to assess the presence of sleep, MTL, or regional cortical differences between groups.

RESULTS

Objective sleep was disrupted in SCD participants, which showed increased nighttime wakefulness and reduced sleep efficiency. No group differences emerged in subjective sleep or magnetic resonance imaging outcomes.

DISCUSSION

Objective sleep resulted disrupted in community-dwelling SCD, without any subjective sleep or cortical change. Sleep assessment/intervention in SCD might help prevent/delay AD onset.

Hypersomnia in Neurodegenerative Diseases

Hypersomnia is a common complaint in many patients with neurodegenerative diseases and a major cause of decreased quality of life. This article discusses the prevalence and factors associated with hypersomnia in patients with a variety of neurodegenerative diseases affecting the central nervous system, including tauopathies, synucleinopathies, and other conditions. Common nocturnal sleep problems that may result in daytime hypersomnia are delineated. A clinical approach to hypersomnia in patients with neurodegenerative diseases, recommended diagnostic testing, and available treatment options are also discussed.

Role of Sleep Disturbance in the Trajectory of Alzheimer's Disease

Sleep disturbances such as insomnia, hypersomnia, and circadian rhythm disturbance are common in normal elderly and Alzheimer’s disease (AD) patients. To date, special attention has been paid to sleep disturbance in the clinical course of AD insofar as the interaction of sleep disturbance with the pathogenesis of AD may impact the clinical course and cognitive function of AD patients. This review covers the bidirectional relationship between sleep disturbance and AD pathogenesis; the associations between sleep disturbance and AD-specific neurotransmitters, brain structure, and aspects of sleep disturbance in each phase of AD; and the effects of sleep disturbance on the cognitive functions of patients in each phase of AD. We consider several factors required to exactly interpret the results and suggest a direction for future studies on the role of sleep disturbance in AD.

Detection and Prevention of Cognitive Decline

Current diagnostic and treatment strategies for cognitive decline can help patients maintain cognitive ability and higher levels of function longer. Despite advances in detection and early treatment strategies, many patients do not receive proper assessments and available therapies. A systematic assessment strategy will increase the likelihood of an accurate diagnosis, which can facilitate pharmacologic and non-pharmacologic treatment plans that can have a meaningful impact on prognosis. Available data support the integration of healthy lifestyle strategies in the treatment plan to help to stabilize symptoms and potentially delay future cognitive decline. While investigators continue to pursue more effective detection, treatment, and prevention strategies, the scientific data support the use of symptomatic drug treatments and recommendations for healthy lifestyle behaviors to improve quality of life and potentially stave off future cognitive decline. Success of such healthy lifestyle programs involves educating participants on the connection between lifestyle and disease prevention, offering enjoyable exercises that target the patient's skill level, and providing feedback that motivates participants to continue their healthy behaviors so they become habits.

The interaction of sleep and amyloid deposition on cognitive performance

Sleep difficulties are emerging as a risk factor for dementia. This study examined the effect of sleep and amyloid deposition on cognitive performance in cognitively normal adults. Sleep efficiency was determined by actigraphy. Cerebrospinal fluid Aβ₄₂ levels <500 pg mL^-1 , indicating amyloid deposition, was present in 23 participants. Psychometric tests included the Free and Cued Selective Reminding Test, Trail Making Test A and B, Animal Fluency, Letter Number Sequencing, and the Mini Mental State Examination. The interaction term of sleep efficiency and amyloid deposition status was a significant predictor of memory performance as measured by total Selective Reminding Test scores. While Trail Making Test B performance was worse in those with amyloid deposition, sleep measures did not have an additive effect. In this study, amyloid deposition was associated with worse cognitive performance, and poor sleep efficiency specifically modified the effect of amyloid deposition on memory performance.

Exploring the bi-directional relationship between sleep and beta-amyloid

PURPOSE OF REVIEW

Suboptimal sleep has been reported as both a comorbidity and risk factor for the development of Alzheimer's disease. Previous research suggests that beta-amyloid (Aβ) may be central to this association, with reports indicating a bi-directional relationship between sleep and Aβ. Here, we review recent animal and human studies investigating the relationship between sleep and measures of Aβ, and explore the potential mechanisms underlying this association.

RECENT FINDINGS

Two recent animal studies have provided further support for a bi-directional relationship between sleep and Aβ. In addition, five recent human studies support the notion that higher brain Aβ is linked to poor sleep in cognitively healthy individuals. One of the recent human studies utilized polysomnography to link brain Aβ to a disruption in slow wave activity during sleep, which in turn was associated with decreased hippocampal-dependent memory.

SUMMARY

Recent findings indicate that poor sleep is a risk factor for brain Aβ deposition, and Aβ deposition contributes to sleep disruption. Through the conduct of more mechanistic studies, and both longitudinal and intervention human studies, we can further elucidate the clearly complex nature of the relationship between sleep and Aβ.

Enhanced sleep reverses memory deficits and underlying pathology in Drosophila models of Alzheimer's disease

To test the hypothesis that sleep can reverse cognitive impairment during Alzheimer's disease, we enhanced sleep in flies either co-expressing human amyloid precursor protein and Beta-secretase (APP:BACE), or in flies expressing human tau. The ubiquitous expression of APP:BACE or human tau disrupted sleep. The sleep deficits could be reversed and sleep could be enhanced when flies were administered the GABA-A agonist 4,5,6,7-tetrahydroisoxazolo-[5,4-c]pyridine-3-ol (THIP). Expressing APP:BACE disrupted both Short-term memory (STM) and Long-term memory (LTM) as assessed using Aversive Phototaxic Suppression (APS) and courtship conditioning. Flies expressing APP:BACE also showed reduced levels of the synaptic protein discs large (DLG). Enhancing sleep in memory-impaired APP:BACE flies fully restored both STM and LTM and restored DLG levels. Sleep also restored STM to flies expressing human tau. Using live-brain imaging of individual clock neurons expressing both tau and the cAMP sensor Epac1-camps, we found that tau disrupted cAMP signaling. Importantly, enhancing sleep in flies expressing human tau restored proper cAMP signaling. Thus, we demonstrate that sleep can be used as a therapeutic to reverse deficits that accrue during the expression of toxic peptides associated with Alzheimer's disease.

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THIP can be used to enhance sleep in two Drosophila models of Alzheimer's disease.

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Enhanced sleep reverses memory deficits in fly's expressing human APP:BACE and tau.

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Enhanced sleep restores cAMP levels in clock neurons expressing tau.

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Sleep can be used as a therapeutic to reverse Alzheimer's disease related deficits.

Sleep in Alzheimer's Disease - Beyond Amyloid

Sleep disorders are prevalent in Alzheimer's disease (AD) and a major cause of institutionalization. Like AD pathology, sleep abnormalities can appear years before cognitive decline and may be predictive of dementia. A bidirectional relationship between sleep and amyloid β (Aβ) has been well established with disturbed sleep and increased wakefulness leading to increased Aβ production and decreased Aβ clearance; whereas Aβ deposition is associated with increased wakefulness and sleep disturbances. Aβ fluctuates with the sleep-wake cycle and is higher during wakefulness and lower during sleep. This fluctuation is lost with Aβ deposition, likely due to its sequestration into amyloid plaques. As such, Aβ is believed to play a significant role in the development of sleep disturbances in the preclinical and clinical phases of AD. In addition to Aβ, the influence of tau AD pathology is likely important to the sleep disturbances observed in AD. Abnormal tau is the earliest observable AD-like pathology in the brain with abnormal tau phosphorylation in many sleep regulating regions such as the locus coeruleus, dorsal raphe, tuberomammillary nucleus, parabrachial nucleus, and basal forebrain prior to the appearance of amyloid or cortical tau pathology. Furthermore, human tau mouse models exhibit AD-like sleep disturbances and sleep changes are common in other tauopathies including frontotemporal dementia and progressive supranuclear palsy. Together these observations suggest that tau pathology can induce sleep disturbances and may play a large role in the sleep disruption seen in AD. To elucidate the relationship between sleep and AD it will be necessary to not only understand the role of amyloid but also tau and how these two pathologies, together with comorbid pathology such as alpha-synuclein, interact and affect sleep regulation in the brain.