Sleep Fragmentation and the Risk of Incident Alzheimer's Disease and Cognitive Decline in Older Persons

Sleep Disorders and Cognitive Dysfunctions in Parkinson's Disease: A Meta-Analytic Study

A relationship between sleep disorders and cognitive dysfunctions was reported in Parkinson's Disease (PD), however, some studies did not confirm the link. A meta-analytic study was performed to investigate the relationship between sleep disorders and cognitive dysfunctions, and to clarify the evolution of cognitive status in PD patients with sleep disorders.The systematic literature search was performed up to November 2020 using PubMed, Scopus, and PsycINFO databases. We included studies published in peer-reviewed journals in English providing results about neuropsychological comparison between patients with or without sleep disorders. Meta-analysis on cross-sectional data included 54 studies for REM Sleep Behavior Disorder (RBD), 22 for Excessive Daytime Sleepiness (EDS), 7 for Obstructive Sleep Apnea (OSA), 13 for Restless Legs Syndrome (RLS), and 5 for insomnia, the meta-analysis on longitudinal data included 7 studies.RBD was related to deficits of global cognitive functioning, memory, executive functions, attention/working memory, language, and visuospatial abilities. EDS was associated with deficits of global cognitive functioning and attention and working memory abilities, whereas RLS and OSA were related to global cognitive dysfunction. Moreover, we revealed that PD patients with RBD and those with EDS performed worse than PD patients without sleep disorders at follow-up rather than baseline evaluation. Our results suggest that sleep disorders are associated with cognitive deficits supporting indirectly that these, especially the REM Sleep Behavior Disorder, reflect abnormalities of frontal networks and posterior cortical areas. Sleep disorders in patients with PD seem to also increase the risk for long-term cognitive decline.

Effects of long sleep time and irregular sleep-wake rhythm on cognitive function in older people

Sleep disturbances and cognitive decline are common in older adults. We aimed to investigate the effects of the total sleep time (TST) and sleep–wake rhythm on executive function and working memory in older adults. In 63 older participants, we measured the TST, wake after sleep onset (WASO), and sleep timing (midpoint between bedtime and wake-up time) using actigraphy. Executive function was evaluated with the trail making test B (TMT-B) and Wisconsin card sorting test (WCST). The number of back task (N-back task) was used to measure working memory. Participants with a TST ≥ 8 h had a significantly lower percentage of correct answers (% correct) on the 1-back task than those with a TST < 8 h. The % correct on the 1-back task was significantly correlated with the TST, WASO, and sleep timing. Multiple regression analyses revealed that the TST and sleep timing were significant factors of the % correct on the 1-back task. The TMT-B score was significantly correlated with the sleep timing. Category achievement on the WCST was significantly correlated with the standard deviation of the sleep timing. Therefore, a long sleep time and an irregular sleep–wake rhythm could have adverse effects on executive function and working memory in older people.

The Relationship Between Coping Strategies and Sleep Problems: The Role of Depressive Symptoms

BACKGROUND

Several studies have proposed that coping strategies are a key predictor of sleep problems. Furthermore, some authors have suggested that depressive symptoms, a factor that is related to both coping strategies and sleep, may play a critical role in this relationship. However, this preliminary research has shown mixed results.

PURPOSE

The aim of this research was to study the relationship between coping strategies (i.e., emotion-focused and problem-focused coping) and sleep, and investigate whether this relationship is direct or mediated by depressive symptoms.

METHODS

Using a cross-sectional design, we tested this idea in a sample of 723 participants from the Midlife in the United States 2 study (mean age = 54.22 years, age range = 25-74 years, 54.40% females, 95.1% had at least a high school education). We applied mediation analyses with bootstrapped bias-corrected 95% confidence intervals to test total, direct, and indirect effects. Coping and depression were assessed using questionnaires. Objective and subjective sleep quantity and quality were measured using the Pittsburgh Sleep Quality Index, sleep diaries, and actigraphy.

RESULTS

The results show that low emotion-focused coping and high problem-focused coping are associated with lower depressive symptoms, which, in turn, are associated with better objective and subjective sleep quality. Moreover, greater use of emotion-focused coping is related to more perceived sleep time.

CONCLUSIONS

This study sheds light on the process of the development of sleep problems in people who use different coping strategies. It offers explanations for the association between emotion-focused and problem-focused coping and sleep problems, via depressive symptoms.

Decoding Causal Links Between Sleep Apnea and Alzheimer’s Disease

Obstructive sleep apnea (OSA) and Alzheimer’s disease (AD) are two common chronic diseases with a well-documented association. Whether the association is causal has been highlighted by recent evidence reporting a neurobiological link between these disorders. This narrative review discusses the brain regions and networks involved in OSA as potential vulnerable areas for the development of AD neuropathology with a particular focus on gender-related implications. Using a neuroimaging perspective supported by neuropathological investigations, we provide a new model of neurodegeneration common to OSA and AD, that we have called OSA-AD neurodegeneration in order to decode the causal links between these two chronic conditions.

Intermittent Light Exposures in Humans: A Case for Dual Entrainment in the Treatment of Alzheimer's Disease

Circadian sleep disorders are common among American adults and can become especially acute among older adults, especially those living with Alzheimer's disease (AD) and mild cognitive impairment (MCI), leading to the exacerbation of symptoms and contributing to the development and advancement of the diseases. This review explores the connections between circadian sleep disorders, cognition, and neurodegenerative disease, offering insights on rapidly developing therapeutic interventions employing intermittent light stimuli for improving sleep and cognition in persons with AD and MCI. Light therapy has the potential to affect sleep and cognition via at least two pathways: (1) a regular and robust light-dark pattern reaching the retina that promotes circadian phase shifting, which can promote entrainment and (2) 40 Hz flickering light that promotes gamma-wave entrainment. While this is a new area of research, preliminary evidence shows the potential of dual circadian and gamma-wave entrainment as an important therapy not only for those with AD, but for others with cognitive impairment.

Brain changes associated with sleep disruption in cognitively unimpaired older adults: A short review of neuroimaging studies

Ageing is characterized by a progressive decline of sleep quality. Sleep difficulties are increasingly recognized as a risk factor for Alzheimer's disease (AD), and have been associated with cognitive decline. However, the brain substrates underlying this association remain unclear. In this review, our objective was to provide a comprehensive overview of the relationships between sleep changes and brain structural, functional and molecular integrity, including amyloid and tau pathologies in cognitively unimpaired older adults. We especially discuss the topography and causality of these associations, as well as the potential underlying mechanisms. Taken together, current findings converge to a link between several sleep parameters, amyloid and tau levels in the CSF, and neurodegeneration in diffuse frontal, temporal and parietal areas. However, the existing literature remains heterogeneous, and the specific sleep changes associated with early AD pathological changes, in terms of topography and neuroimaging modality, is not clearly established yet. Notably, if slow wave sleep disruption seems to be related to frontal amyloid deposition, the brain correlates of sleep-disordered breathing and REM sleep disruption remain unclear. Moreover, sleep parameters associated with tau- and FDG-PET imaging are largely unexplored. Lastly, whether sleep disruption is a cause or a consequence of brain alterations remains an open question.

Sleep Deprivation, a Link Between Post-Traumatic Stress Disorder and Alzheimer's Disease

An estimated 5 million Americans are living with Alzheimer's disease (AD), and there is also a significant impact on caregivers, with an additional 16 million Americans providing unpaid care for individuals with AD and other dementias. These numbers are projected to increase in the coming years. While AD is still without a cure, continued research efforts have led to better understanding of pathology and potential risk factors that could be exploited to slow disease progression. A bidirectional relationship between sleep deprivation and AD has been suggested and is well supported by both human and animal studies. Even brief episodes of inadequate sleep have been shown to cause an increase in amyloidβ and tau proteins, both well-established contributors toAD pathology. Sleep deprivation is also the most common consequence of post-traumatic stress disorder (PTSD). Patients with PTSD frequently present with sleep disturbances and also develop dementia at twice the rate of the general population accounting for a disproportionate representation of AD among U.S. Veterans. The goal of this review is to highlight the relationship triad between sleep deprivation, AD, and PTSD as well as their impact on molecular mechanisms driving AD pathology.

Prospective associations between change in sleep duration and cognitive impairment: Findings from the Singapore Chinese Health Study

BACKGROUND

The relation of changes in sleep duration with risk of cognitive impairment are inconclusive. This study evaluated the prospective relationships of changes in sleep duration with risk of cognitive impairment in Singapore Chinese.

METHODS

We used data from 16,948 Chinese men and women who were aged 45-74 years at baseline (1993-1998) during recruitment into the Singapore Chinese Health Study cohort. Daily sleep duration was assessed at baseline, follow-up 2 (2006 to 2010) and follow-up 3 interviews (2014-2016). Cognitive function was evaluated with a Singapore-Modified Mini-Mental State Examination at follow-up 3 interviews when participants were 61-96 years old. Multivariable logistic regression models were used to calculate odd ratios (ORs) and 95% confidence intervals (95% CIs) for cognitive impairment.

RESULTS

Of the 16,948 participants, 14.4% were defined to have cognitive impairment. Compared with 7 h/day sleep at both baseline and follow-up 2, the OR (95% CI) for cognitive impairment was 1.50 (1.04-2.16) for those who maintained long sleep duration (≥9 h/day), 2.18 (1.37-3.45) for those who prolonged sleep from short duration (≤5 h/day) to long duration (≥9 h/day), and 1.55 (1.20-2.02) for those who prolonged sleep from recommended duration (7 h/day) to long duration. The highest risk was observed in those who shortened sleep from long to short duration (2.93, 1.35-6.34).

LIMITATIONS

Measures of sleep were self-reported.

CONCLUSIONS

Substantial changes in sleep duration over time were associated with higher risks of cognitive impairment. The findings underscore the importance of maintaining optimal sleep duration for the prevention of cognitive impairment.

Sleep in the Aging Brain

We have entered an era of a steep increase in the absolute and relative number of older people. This well-come phenomenon represents a major challenge for health care. However, maturational changes in sleep associated with aging do not easily appear as main factors, even though sleep alterations in the aging process lead to many detrimental consequences. In this editorial paper, we summarize the present knowledge about the main aging-related sleep modifications and their relevance for health problems and cognitive decline. Then, we present the papers published in the Special Issue “Disturbances of Sleep Among Older People”.

Systemic inflammation as a moderator between sleep and incident dementia

STUDY OBJECTIVES

To determine whether C-reactive protein (CRP), a marker of systemic inflammation, moderates the association between sleep and incident dementia.

METHODS

We studied Framingham Heart Study participants who completed at baseline a serum CRP assessment and in-home polysomnography to measure sleep duration, sleep efficiency, sleep latency, wake after sleep onset (WASO), number of awakenings, arousal index, and apnea-hypopnea index. Participants were divided into groups according to their CRP level: low (<1 mg/L), average (1-3 mg/L), and high inflammation (>3 mg/L). Surveillance for outcomes (incident all-cause and Alzheimer's disease [AD] dementia) commenced at baseline and continued up to 22.5 years.

RESULTS

In 291 participants (mean age 67.5 ± 4.9 years, 51.6% men) followed for 13.4 ± 5.4 years, we observed 43 cases of all-cause dementia, 33 of which were clinically consistent with AD. Whereas no direct association between CRP or sleep exposures was observed with incident dementia, CRP levels interacted with nighttime wakefulness when predicting both incident all-cause and AD dementia. In the high CRP group, longer WASO (hazard ratio [HR], 2.89; 95% CI, 1.31-6.34) and more nighttime awakenings (HR, 4.55; 95% CI, 1.19-17.38) were associated with higher risk of incident dementia. In the low CRP group, fewer nighttime awakenings were associated with a higher risk of incident dementia (HR, 0.07; 95% CI, 0.01-0.68).

CONCLUSIONS

Our findings suggest that inflammation moderates the association between sleep, particularly nighttime wakefulness, and dementia risk. The presence of inflammation may be an important determinant in evaluating how sleep disturbances relate to neurodegeneration.

Examining sleep deficiency and disturbance and their risk for incident dementia and all-cause mortality in older adults across 5 years in the United States

BACKGROUND

Sleep disturbance and deficiency are common among older adults and have been linked with dementia and all-cause mortality. Using nationally representative data, we examine the relationship between sleep disturbance and deficiency and their risk for incident dementia and all-cause mortality among older adults.

METHODS

The National Health and Aging Trends Study (NHATS) is a nationally-representative longitudinal study of Medicare beneficiaries in the US age 65 and older. Surveys that assessed sleep disturbance and duration were administered at baseline. We examined the relationship between sleep disturbance and deficiency and incident dementia and all-cause mortality over the following 5 years using Cox proportional hazards modeling, controlling for confounders.

RESULTS

Among the sample (n = 2,812), very short sleep duration (≤5 hours: HR = 2.04, 95% CI: 1.26 - 3.33) and sleep latency (>30 minutes: HR = 1.45, 95% CI: 1.03 - 2.03) were associated with incident dementia in adjusted Cox models. Difficulty maintaining alertness ("Some Days": HR = 1.49, 95% CI: 1.13 - 1.94 and "Most/Every Day": HR = 1.65, 95% CI: 1.17 - 2.32), napping ("Some days": HR = 1.38, 95% CI: 1.03 - 1.85; "Most/Every Day": HR = 1.73, 95% CI: 1.29 - 2.32), sleep quality ("Poor/Very Poor": HR = 1.75, 95% CI: 1.17 - 2.61), and very short sleep duration (≤5 hours: HR = 2.38, 95% CI: 1.44 - 3.92) were associated with all-cause mortality in adjusted Cox models.

CONCLUSIONS

Addressing sleep disturbance and deficiency may have a positive impact on risk for incident dementia and all-cause mortality among older adults.

Sleep and its regulation: An emerging pathogenic and treatment frontier in Alzheimer's disease

A majority of patients with Alzheimer's disease (AD) experience some form of sleep disruption, including nocturnal sleep fragmentation, increased daytime napping, decreased slow-wave sleep (SWS, stage N3), and decreased rapid-eye-movement sleep (REM). Clinical studies are investigating whether such sleep disturbances are a consequence of the underlying disease, and whether they also contribute to the clinical and pathological manifestations of AD. Emerging research has provided a direct link between several of these sleep disruptions and AD pathophysiology, suggesting that treating sleep disorders in this population may target basic mechanisms of the disease. Here, we provide a comprehensive review of sleep disturbances associated with the spectrum of AD, ranging from the preclinical stages through dementia. We discuss how sleep interacts with AD pathophysiology and, critically, whether sleep impairments can be targeted to modify the disease course in a subgroup of affected AD patients. Ultimately, larger studies that fully utilize new diagnostic and experimental tools will be required to better define the most relevant sleep disturbance to target in AD, the interventions that best modulate this target symptom, and whether successful early intervention can modify AD risk and prevent dementia.

Association between sleep disturbance with motoric cognitive risk syndrome in Chinese older adults

BACKGROUND AND PURPOSE

Sleep disturbance and cognitive impairment are common and related in the elderly population worldwide. The aim of the present study was to explore the association between sleep disturbance and motoric cognitive risk (MCR) syndrome, which is characterized by subjective cognitive complaints and objective slow gait in older individuals without dementia or any mobility disability in the community-dwelling elderly Chinese population.

METHODS

We recruited 940 participants aged ≥65 years from November 2016 to March 2017 in the Ningbo Community Study on Aging (NCSA). Self-reported sleep duration and sleep-quality variables, comprehensive geriatric evaluation, as well as indicators for diagnosing MCR syndrome were evaluated in this cross-sectional study.

RESULTS

Multiple logistic regression analysis showed that a 1-SD increase in night (1.1 h) and 24-h sleep duration (1.3 h) was associated, respectively, with a 21% (95% confidence interval [CI], 1%-47%; p = 0.04) and 30% (95% CI, 3%-64%; p = 0.03) higher odds of having MCR syndrome. Considering sleep duration as a categorical variable, longer night-sleep duration (>8.5 h) was associated with MCR syndrome (OR, 2.03; p = 0.02) compared to shorter night-sleep duration (<8 h). For sleep-quality factors, increasing frequency of trouble falling asleep, waking early or easily, nightmares, and taking sleep drugs were significantly associated with MCR syndrome after adjusting for potential covariables (all p for trend < 0.05), but not for self-perceived sleep quality (p for trend = 0.10).

CONCLUSIONS

Long sleep duration, poor sleep quality, and taking sleep drugs were associated with higher odds of having MCR syndrome in the community-dwelling elderly Chinese population. Further research is needed to explore the underlying mechanisms.

Time-Varying Insomnia Symptoms and Incidence of Cognitive Impairment and Dementia among Older US Adults

There is conflicting evidence regarding the association between insomnia and the onset of mild cognitive impairment (MCI) or dementia. This study aimed to evaluate if time-varying insomnia is associated with the development of MCI and dementia. Data from the Health and Retirement Study (n = 13,833) from 2002 to 2014 were used (59.4% female). The Brief Insomnia Questionnaire was used to identify insomnia symptoms which were compiled in an insomnia severity index, ranging from 0 to 4. In analysis, participants' symptoms could vary from wave-to-wave. Dementia was defined using results from the Health and Retirement Study (HRS) global cognitive assessment tool. Respondents were classified as either having dementia, MCI, or being cognitively healthy. Cox proportional hazards models with time-dependent exposure using the counting process (start-stop time) were used for analysis. For each one-unit increase in the insomnia symptom index, there was a 5-percent greater hazard of MCI (HR = 1.05; 95% CI: 1.04-1.06) and dementia (HR = 1.05; 95% CI: 1.03-1.05), after fully adjusting. Using a nationally representative sample of adults age 51 and older, this study found that time-varying insomnia symptoms are associated with risk of MCI and dementia. This highlights the importance of identifying sleep disturbances and their change over time as potentially important risk factors for MCI and dementia.

The Treatment of Sleep Dysfunction in Neurodegenerative Disorders

Sleep dysfunction is highly prevalent across the spectrum of neurodegenerative conditions and is a key determinant of quality of life for both patients and their families. Mounting recent evidence also suggests that such dysfunction exacerbates cognitive and affective clinical features of neurodegeneration, as well as disease progression through acceleration of pathogenic processes. Effective assessment and treatment of sleep dysfunction in neurodegeneration is therefore of paramount importance; yet robust therapeutic guidelines are lacking, owing in part to a historical paucity of effective treatments and trials. Here, we review the common sleep abnormalities evident in neurodegenerative disease states and evaluate the latest evidence for traditional and emerging interventions, both pharmacological and nonpharmacological. Interventions considered include conservative measures, targeted treatments of specific clinical sleep pathologies, established sedating and alerting agents, melatonin, and orexin antagonists, as well as bright light therapy, behavioral measures, and slow-wave sleep augmentation techniques. We conclude by providing a suggested framework for treatment based on contemporary evidence and highlight areas that may emerge as major therapeutic advances in the near future.

The role of sleep disturbances in cognitive function and depressive symptoms among community-dwelling elderly with sleep complaints

OBJECTIVE

The relationships between sleep problems, cognitive impairments, and depression have been established in the aging population. However, less is known about the role of late-life onset insomnia and sex involved in these dyad or tripartite relationships. This study aimed to consider onset age of insomnia and sex in the relationship between sleep parameters, cognition and depression among older adults with current insomnia complaints.

METHOD

A multistep sampling method was adopted to recruit participants with current insomnia complaints in China in 2018. Sleep measures include onset age of insomnia (64 years old or before vs during/after 65), three factors from insomnia severity index (ISI; nighttime, daytime, and perception), excessive daytime sleepiness, and sleep duration. Outcome measures were mini-mental state examination (MMSE) and center for epidemiologic studies depression scale (CESD).

RESULTS

The average age of older adults was 75 (SD = 7.1). Among them, 62% participants are female. In general, older aged, female, late-life onset insomnia as well as interaction of sex * onset age of insomnia were significantly associated with poorer cognition. Yet, age, sex, and onset age of insomnia were not significant indicators for depression. For female participants, later onset of insomnia, nighttime symptoms of insomnia, excessive daytime sleepiness and depression were risk factors for cognitive decline. Nevertheless, only daytime sleepiness, together with depression, were found positively associated with male participants' cognitive decline.

CONCLUSIONS

There were robust associations between daytime sleepiness, depressive symptoms, and poor cognitive performance. More importantly, late-life onset insomnia was particularly indicative for poor cognitive performance among female older adults. Future study should emphasize the specific mechanism involved in changes of sleep patterns in the development of cognitive impairment among older adults. Sex differences in the relationship between onset age of insomnia and cognition also require further attention.

The Reciprocal Interaction Between Sleep and Alzheimer's Disease

It is becoming increasingly recognized that patients with a variety of neurodegenerative diseases exhibit disordered sleep/wake patterns. While sleep impairments have typically been thought of as sequelae of underlying neurodegenerative processes in sleep-wake cycle regulating brain regions, including the brainstem, hypothalamus, and basal forebrain, emerging evidence now indicates that sleep deficits may also act as pathophysiological drivers of brain-wide disease progression. Specifically, recent work has indicated that impaired sleep can impact on neuronal activity, brain clearance mechanisms, pathological build-up of proteins, and inflammation. Altered sleep patterns may therefore be novel (potentially reversible) dynamic functional markers of proteinopathies and modifiable targets for early therapeutic intervention using non-invasive stimulation and behavioral techniques. Here we highlight research describing a potentially reciprocal interaction between impaired sleep and circadian patterns and the accumulation of pathological signs and features in Alzheimer's disease, the most prevalent neurodegenerative disease in the elderly.

Promoting Successful Cognitive Aging: A Ten-Year Update

A decade has passed since we published a comprehensive review in this journal addressing the topic of promoting successful cognitive aging, making this a good time to take stock of the field. Because there have been limited large-scale, randomized controlled trials, especially following individuals from middle age to late life, some experts have questioned whether recommendations can be legitimately offered about reducing the risk of cognitive decline and dementia. Despite uncertainties, clinicians often need to at least make provisional recommendations to patients based on the highest quality data available. Converging lines of evidence from epidemiological/cohort studies, animal/basic science studies, human proof-of-concept studies, and human intervention studies can provide guidance, highlighting strategies for enhancing cognitive reserve and preventing loss of cognitive capacity. Many of the suggestions made in 2010 have been supported by additional research. Importantly, there is a growing consensus among major health organizations about recommendations to mitigate cognitive decline and promote healthy cognitive aging. Regular physical activity and treatment of cardiovascular risk factors have been supported by all of these organizations. Most organizations have also embraced cognitively stimulating activities, a heart-healthy diet, smoking cessation, and countering metabolic syndrome. Other behaviors like regular social engagement, limiting alcohol use, stress management, getting adequate sleep, avoiding anticholinergic medications, addressing sensory deficits, and protecting the brain against physical and toxic damage also have been endorsed, although less consistently. In this update, we review the evidence for each of these recommendations and offer practical advice about behavior-change techniques to help patients adopt brain-healthy behaviors.

The Sleep Side of Aging and Alzheimer's Disease

As we age, sleep patterns undergo significant modifications in micro and macrostructure, worsening cognition and quality of life. These are associated with remarkable brain changes, like deterioration in synaptic plasticity, gray and white matter, and significant modifications in hormone levels. Sleep alterations are also a core component of mild cognitive impairment (MCI) and Alzheimer's Disease (AD). AD night time is characterized by a gradual decrease in slow-wave activity and a substantial reduction of REM sleep. Sleep abnormalities can accelerate AD pathophysiology, promoting the accumulation of amyloid-β (Aβ) and phosphorylated tau. Thus, interventions that target sleep disturbances in elderly people and MCI patients have been suggested as a possible strategy to prevent or decelerate conversion to dementia. Although cognitive-behavioral therapy and pharmacological medications are still first-line treatments, despite being scarcely effective, new interventions have been proposed, such as sensory stimulation and Noninvasive Brain Stimulation (NiBS). The present review outlines the current state of the art of the relationship between sleep modifications in healthy aging and the neurobiological mechanisms underlying age-related changes. Furthermore, we provide a critical analysis showing how sleep abnormalities influence the prognosis of AD pathology by intensifying Aβ and tau protein accumulation. We discuss potential therapeutic strategies to target sleep disruptions and conclude that there is an urgent need for testing new therapeutic sleep interventions.

Circadian changes in Alzheimer's disease: Neurobiology, clinical problems, and therapeutic opportunities

The understanding of Alzheimer's disease (AD) pathophysiology is an active area of research, and the traditional focus on hippocampus, amyloid and tau protein, and memory impairment has been expanded with components like neuroinflammation, insulin resistance, and circadian rhythm alterations. The bidirectional vicious cycle of neuroinflammation and neurodegeneration on a molecular level may cause functional deficits already long before the appearance of overt clinical symptoms. Located at the crossroads of metabolic, circadian, and hormonal signaling, the hypothalamus has been identified as another brain region affected by AD pathophysiology. Current findings on hypothalamic dysfunction open a broader horizon for studying AD pathogenesis and offer new opportunities for diagnosis and therapy. While treatments with cholinomimetics and memantine form a first line of pharmacological treatment, additional innovative research is pursued toward the development of antiinflammatory, growth factor, or antidiabetic types of medication. Following recent epidemiological data showing associations of AD incidence with modern societal and "life-style"-related risk factors, also nonpharmacological interventions, including sleep optimization, are being developed and some have been shown to be beneficial. Circadian aspects in AD are relevant from a pathophysiological standpoint, but they can also have an important role in pharmacologic and nonpharmacologic interventions, and appropriate timing of sleep, meals, and medication may boost therapeutic efficacy.

The Role of Perioperative Sleep Disturbance in Postoperative Neurocognitive Disorders

Postoperative neurocognitive disorder (PND) increases the length of hospital stay, mortality, and risk of long-term cognitive impairment. Perioperative sleep disturbance is prevalent and commonly ignored and may increase the risk of PND. However, the role of perioperative sleep disturbances in PND remains unclear. Nocturnal sleep plays an indispensable role in learning, memory, and maintenance of cerebral microenvironmental homeostasis. Hospitalized sleep disturbances also increase the incidence of postoperative delirium and cognitive dysfunction. This review summarizes the role of perioperative sleep disturbances in PND and elucidates the potential mechanisms underlying sleep-deprivation-mediated PND. Activated neuroinflammation and oxidative stress; impaired function of the blood-brain barrier and glymphatic pathway; decreased hippocampal brain-derived neurotrophic factor, adult neurogenesis, and sirtuin1 expression; and accumulated amyloid-beta proteins are associated with PND in individuals with perioperative sleep disorders. These findings suggest that the improvement of perioperative sleep might reduce the incidence of postoperative delirium and postoperative cognitive dysfunction. Future studies should further investigate the role of perioperative sleep disturbance in PND.

The sleep and circadian problems of Huntington's disease: when, why and their importance

Introduction

Mounting evidence supports the existence of an important feedforward cycle between sleep and neurodegeneration, wherein neurodegenerative diseases cause sleep and circadian abnormalities, which in turn exacerbate and accelerate neurodegeneration. If so, sleep therapies bear important potential to slow progression in these diseases.

Findings

This cycle is challenging to study, as its bidirectional nature renders cause difficult to disentangle from effect. Likewise, well-controlled intervention studies are often impractical in the setting of established neurodegenerative disease. It is this that makes understanding sleep and circadian abnormalities in Huntington’s disease (HD) important: as a monogenic fully penetrant neurodegenerative condition presenting in midlife, it provides a rare opportunity to study sleep and circadian abnormalities longitudinally, prior to and throughout disease manifestation, and in the absence of confounds rendered by age and comorbidities. It also provides potential to trial sleep therapies at a preclinical or early disease stage. Moreover, its monogenic nature facilitates the development of transgenic animal models through which to run parallel pre-clinical studies. HD, therefore, provides a key model condition through which to gain new insights into the sleep-neurodegeneration interface.

Conclusions

Here, we begin by summarising contemporary knowledge of sleep abnormalities in HD, and consider how well these parallel those of Alzheimer’s and Parkinson’s as more common neurodegenerative conditions. We then discuss what is currently known of the sleep-neurodegeneration cyclical relationship in HD. We conclude by outlining key directions of current and future investigation by which to advance the sleep-neurodegeneration field via studies in HD.

Translational changes induced by acute sleep deprivation uncovered by TRAP-Seq

Sleep deprivation is a global health problem adversely affecting health as well as causing decrements in learning and performance. Sleep deprivation induces significant changes in gene transcription in many brain regions, with the hippocampus particularly susceptible to acute sleep deprivation. However, less is known about the impacts of sleep deprivation on post-transcriptional gene regulation. To identify the effects of sleep deprivation on the translatome, we took advantage of the RiboTag mouse line to express HA-labeled Rpl22 in CaMKIIα neurons to selectively isolate and sequence mRNA transcripts associated with ribosomes in excitatory neurons. We found 198 differentially expressed genes in the ribosome-associated mRNA subset after sleep deprivation. In comparison with previously published data on gene expression in the hippocampus after sleep deprivation, we found that the subset of genes affected by sleep deprivation was considerably different in the translatome compared with the transcriptome, with only 49 genes regulated similarly. Interestingly, we found 478 genes differentially regulated by sleep deprivation in the transcriptome that were not significantly regulated in the translatome of excitatory neurons. Conversely, there were 149 genes differentially regulated by sleep deprivation in the translatome but not in the whole transcriptome. Pathway analysis revealed differences in the biological functions of genes exclusively regulated in the transcriptome or translatome, with protein deacetylase activity and small GTPase binding regulated in the transcriptome and unfolded protein binding, kinase inhibitor activity, neurotransmitter receptors and circadian rhythms regulated in the translatome. These results indicate that sleep deprivation induces significant changes affecting the pool of actively translated mRNAs.

Gender difference in health issues and cognitive functions among an Egyptian normal elderly population

Background

Aging is associated with changes in cognitive functions. However, many other factors may affect cognitive functions and this interaction needs further assessment.

Objectives

To detect gender differences in sleep quality, nutritional status, and health-related quality of life and their impact on performance in verbal fluency tasks among apparently healthy elderly.

Subjects and methods

The study was conducted on 102 normal aged subjects, 51 males and 51 females. Subjects were divided according to age into group ≥ 60 years and group < 60 years as a control. They were subjected to clinical assessment, Medical outcome study Short-Form 36-item Health Survey, Pittsburgh sleep quality index, mini nutritional assessment and Category Verbal fluency for animals and girls’ names.

Results

Among the older group, females had significantly poorer physical and mental health, sleep quality and nutritional status than males (p value 0.001, 0.003, 0.012, and 0.014, respectively). Older females had significantly lower performance in verbal fluency (girls’ names) compared to younger females (p value 0.013), but no significant gender difference was found among the older group. Verbal fluency tasks are correlated to the level of education in both males and females (r 0.392 and 0.42, p value 0.029 and 0.019, respectively), However, in older males, it is also correlated to sleep latency (r 0.41 and p value 0.021).

Conclusion

Older females had poorer sleep quality, lower health-related quality of life and lower nutritional status. No gender difference was found in verbal fluency tasks. Although no single variable could independently affect verbal fluency, education remains the main player in the difference in performance.

Circadian disturbances in Alzheimer's disease progression: a prospective observational cohort study of community-based older adults

BACKGROUND

Circadian disturbances are commonly seen in people with Alzheimer's disease and have been reported in individuals without symptoms of dementia but with Alzheimer's pathology. We aimed to assess the temporal relationship between circadian disturbances and Alzheimer's progression.

METHODS

We did a prospective cohort study of 1401 healthy older adults (aged >59 years) enrolled in the Rush Memory and Aging Project (Rush University Medical Center, Chicago, IL, USA) who had been followed up for up to 15 years. Participants underwent annual assessments of cognition (with a battery of 21 cognitive performance tests) and motor activities (with actigraphy). Four measures were extracted from actigraphy to quantify daily and circadian rhythmicity, which were amplitude of 24-h activity rhythm, acrophase (representing peak activity time), interdaily stability of 24-h activity rhythm, and intradaily variability for hourly fragmentation of activity rhythm. We used Cox proportional hazards models and logistic regressions to assess whether circadian disturbances predict an increased risk of incident Alzheimer's dementia and conversion of mild cognitive impairment to Alzheimer's dementia. We used linear mixed-effects models to investigate how circadian rhythms changed longitudinally and how the change integrated to Alzheimer's progression.

FINDINGS

Participants had a median age of 81·8 (IQR 76·3-85·7) years. Risk of developing Alzheimer's dementia was increased with lower amplitude (1 SD decrease, hazard ratio [HR] 1·39, 95% CI 1·19-1·62) and higher intradaily variability (1 SD increase, 1·22, 1·04-1·43). In participants with mild cognitive impairment, increased risk of Alzheimer's dementia was predicted by lower amplitude (1 SD decrease, HR 1·46, 95% CI 1·24-1·72), higher intradaily variability (1 SD increase, 1·36, 1·15-1·60), and lower interdaily stability (1 SD decrease, 1·21, 1·02-1·44). A faster transition to Alzheimer's dementia in participants with mild cognitive impairment was predicted by lower amplitude (1 SD decrease, odds ratio [OR] 2·08, 95% CI 1·53-2·93), increased intradaily variability (1 SD increase, 1·97, 1·43-2·79), and decreased interdaily stability (1 SD decrease, 1·35, 1·01-1·84). Circadian amplitude, acrophase, and interdaily stability progressively decreased over time, and intradaily variability progressively increased over time. Alzheimer's progression accelerated these aging effects by doubling or more than doubling the annual changes in these measures after the diagnosis of mild cognitive impairment, and further doubled them after the diagnosis of Alzheimer's dementia. The longitudinal change of global cognition positively correlated with the longitudinal changes in amplitude and interdaily stability and negatively correlated with the longitudinal change in intradaily variability.

INTERPRETATION

Our results indicate a link between circadian dysregulation and Alzheimer's progression, implying either a bidirectional relation or shared common underlying pathophysiological mechanisms.

FUNDING

National Institutes of Health, and the BrightFocus Foundation.

Characteristics of Sleep Structure Assessed by Objective Measurements in Patients With Amnestic Mild Cognitive Impairment: A Meta-Analysis

Objectives: This study aims to explore the differences of sleep structure between patients with amnestic mild cognitive impairment (aMCI) and elderly people with normal cognition, which will help to provide evidence for the relationship between sleep disturbances and cognitive impairment.

Methods: A systematic review and meta-analysis were conducted on the literature on sleep parameters obtained by polysomnography or actigraphy in patients with aMCI. The PubMed and EMBASE databases were searched up to April 2020. Inclusion and exclusion criteria were established according to evidence-based medicine methods, and data of all eligible studies were meta-analyzed using the Review Manager 5.3 software.

Results: Among the 1,171 literature articles on sleep structure of patients with MCI, eight case-control studies met the inclusion criteria and were included in this meta-analysis. A total of 278 subjects were included, of which 103 were patients with aMCI and 175 were elderly people with normal cognition. The results showed that sleep efficiency (SE) and slow wave sleep (SWS) of patients with aMCI were significantly lower than those of healthy elderly people. Compared with the control group, the percentage of stage 1 of non-rapid eye movement (N1%) in the aMCI patients group increased, and the percentage of stage 2 of non-rapid eye movement (N2%) decreased.

Conclusions: Patients with aMCI may experience more severe sleep disturbances than normal cognitive elderly people. There were specific changes, especially in SE and SWS, in the sleep structure of patients with aMCI when compared to those with normal cognition.

Sleep Disturbance Forecasts β-Amyloid Accumulation across Subsequent Years

Experimental sleep-wake disruption in rodents and humans causally modulates β-amyloid (Aβ) dynamics (e.g., [1-3]). This leads to the hypothesis that, beyond cross-sectional associations, impaired sleep structure and physiology could represent prospective biomarkers of the speed with which Aβ accumulates over time. Here, we test the hypothesis that initial baseline measures of non-rapid eye movement (NREM) sleep slow-wave activity (SWA) and sleep quality (efficiency) provide future forecasting sensitivity to the rate of Aβ accumulation over subsequent years. A cohort of clinically normal older adults was assessed using objective sleep polysomnography in combination with longitudinal tracking of Aβ accumulation with [11C]PiB positron emission tomography (PET) imaging. Both the proportion of NREM SWA below 1 Hz and the measure of sleep efficiency predicted the speed (slope) of subsequent Aβ deposition over time, and these associations remained robust when taking into account additional cofactors of interest (e.g., age, sex, sleep apnea). Moreover, these measures were specific, such that no other macro- and microphysiological architecture metrics of sleep demonstrated such sensitivity. Our data support the proposal that objective sleep markers could be part of a set of biomarkers that statistically forecast the longitudinal trajectory of cortical Aβ deposition in the human brain. Sleep may therefore represent a potentially affordable, scalable, repeatable, and non-invasive tool for quantifying of Aβ pathological progression, prior to cognitive symptoms of Alzheimer's disease (AD).

Obstructive Sleep Apnea and Its Treatment in Aging: Effects on Alzheimer's disease Biomarkers, Cognition, Brain Structure and Neurophysiology

Here we review the impact of obstructive sleep apnea (OSA) on biomarkers of Alzheimer's disease (AD) pathogenesis, neuroanatomy, cognition and neurophysiology, and present the research investigating the effects of continuous positive airway pressure (CPAP) therapy. OSA is associated with an increase in AD markers amyloid-β and tau measured in cerebrospinal fluid (CSF), by Positron Emission Tomography (PET) and in blood serum. There is some evidence suggesting CPAP therapy normalizes AD biomarkers in CSF but since mechanisms for amyloid-β and tau production/clearance in humans are not completely understood, these findings remain preliminary. Deficits in the cognitive domains of attention, vigilance, memory and executive functioning are observed in OSA patients with the magnitude of impairment appearing stronger in younger people from clinical settings than in older community samples. Cognition improves with varying degrees after CPAP use, with the greatest effect seen for attention in middle age adults with more severe OSA and sleepiness. Paradigms in which encoding and retrieval of information are separated by periods of sleep with or without OSA have been done only rarely, but perhaps offer a better chance to understand cognitive effects of OSA than isolated daytime testing. In cognitively normal individuals, changes in EEG microstructure during sleep, particularly slow oscillations and spindles, are associated with biomarkers of AD, and measures of cognition and memory. Similar changes in EEG activity are reported in AD and OSA, such as "EEG slowing" during wake and REM sleep, and a degradation of NREM EEG microstructure. There is evidence that CPAP therapy partially reverses these changes but large longitudinal studies demonstrating this are lacking. A diagnostic definition of OSA relying solely on the Apnea Hypopnea Index (AHI) does not assist in understanding the high degree of inter-individual variation in daytime impairments related to OSA or response to CPAP therapy. We conclude by discussing conceptual challenges to a clinical trial of OSA treatment for AD prevention, including inclusion criteria for age, OSA severity, and associated symptoms, the need for a potentially long trial, defining relevant primary outcomes, and which treatments to target to optimize treatment adherence.

Lifetime Methamphetamine Use Disorder and Reported Sleep Quality in Adults Living with HIV

This study evaluated whether a history of lifetime methamphetamine (MA) use disorder increases risk for poor sleep quality in people with or without HIV infection (HIV+/HIV-). Participants (n = 313) were stratified into four groups based on HIV status and lifetime MA use disorder diagnosis [HIV+/MA+ (n = 84); HIV+/MA- (n = 141); HIV-/MA+ (n = 16); and HIV-/MA- (n = 72)] and compared on global sleep outcomes using the Pittsburgh Sleep Quality Index (PSQI). Significant differences on global sleep were observed between HIV+/MA+ and HIV+/MA- groups, but not between the HIV- groups. Follow-up multiple regression analyses within the HIV+ subgroups examined global sleep scores as a function of MA status and clinical covariates, including those related to HIV disease and demographics. HIV+ individuals with a history of MA use disorder evidenced significantly poorer sleep quality and were more likely to be classified as problematic sleepers than those without a lifetime disorder. This was independent of depressed mood, body mass index, and viral suppression while on treatment. Poorer reported sleep quality among HIV+/MA+ was associated also with multiple adverse functional outcomes, including greater objective cognitive impairment, unemployment, clinical ratings of functional impairment, and self-reported cognitive difficulties, decreased independence in activities of daily living, and poorer overall life quality. Interventions to avoid or curtail MA use in HIV+ individuals may help protect sleep quality and improve functioning.

Cognitive behavioral therapy for insomnia to enhance cognitive function and reduce the rate of Aβ deposition in older adults with symptoms of insomnia: A single-site randomized pilot clinical trial protocol

Lifestyle interventions to increase exercise and improve diet have been the focus of recent clinical trials to potentially prevent Alzheimer's disease (AD). However, despite the strong links between sleep disruptions, cognitive decline, and AD, sleep enhancement has yet to be targeted as a lifestyle intervention to prevent AD. A recent meta-analysis suggests that approximately 15% of AD may be prevented by an efficacious intervention aimed to reduce sleep disturbances and sleep disorders. Chronic insomnia is the most frequent sleep disorder occurring in at least 40% of older adults. Individuals with insomnia are more likely to be diagnosed with Alzheimer's Disease (AD) and demonstrate decline in cognitive function at long-term follow-up. AD is characterized by the accumulation of amyloid-β (Aβ) plaques and tau tangles in the brain, and growing evidence shows impaired sleep contributes to the accumulation of Aβ. An intervention aimed at improving insomnia may be a critical opportunity for primary prevention to slow cognitive decline and potentially delay the onset of AD. Cognitive behavioral therapy for insomnia (CBT-I) is an efficacious treatment for insomnia, but the use of CBT-I to improve cognitive function and potentially reduce the rate of Aβ accumulation has never been examined. Therefore, the objective of the proposed study is to examine the efficacy of CBT-I on improving cognitive function in older adults with symptoms of insomnia. An exploratory aim is to assess the effect of CBT-I on rate of Aβ accumulation.

PER2 C111G polymorphism, cognitive reserve and cognition in subjective cognitive decline and mild cognitive impairment: a 10-year follow-up study

BACKGROUND AND PURPOSE

CLOCK and PER2 genes have been implicated in sleep-wake cycle alterations and neurodegenerative diseases. Our aim was to evaluate the effect of CLOCK T3111C and PER2 C111G on cognitive functioning in subjective cognitive decline (SCD) patients and mild cognitive impairment (MCI) patients at the baseline of a longitudinal study, and the effect of these two polymorphisms on the progression to Alzheimer's disease (AD) of the two groups.

METHODS

Sixty-eight subjects (41 SCD and 27 MCI) who underwent clinical evaluation, neuropsychological assessment, CLOCK and PER2 genotyping at baseline and neuropsychological follow-up every 2 years for a mean time of 10 years were included. Subjects who developed AD (SCD-c and MCI-c) and non-converters (SCD-nc, MCI-nc) were considered.

RESULTS

CLOCK T3111C was detected in 47% of cases (21 SCD, 11 MCI) and PER2 C111G in 19% of cases (eight SCD and five MCI). PER2 G carriers presented lower premorbid intelligence score (P = 0.049), fewer years of education (P = 0.007) and a lower frequency of family history of AD (P = 0.04) than G non-carriers. MCI PER2 G carriers had worse performance in tests assessing memory, executive function, language and visuospatial abilities at baseline. During follow-up, two SCD and 15 MCI subjects progressed to AD: both of the SCD-c subjects presented the PER2 G allele, while none of the SCD PER2 G non-carriers converted to AD (P = 0.003).

CONCLUSION

PER2 seems to have a role in cognitive reserve and cognition in SCD and MCI patients. Nevertheless, further studies are needed to assess the role of PER2 C111G on the risk of progression to AD.

CCCDTD5 recommendations on early non cognitive markers of dementia: A Canadian consensus

Introduction

Cognitive impairment is the hallmark of Alzheimer's disease (AD) and related dementias. However, motor decline has been recently described as a prodromal state that can help to detect at‐risk individuals. Similarly, sensory changes, sleep and behavior disturbances, and frailty have been associated with higher risk of developing dementia. These clinical findings, together with the recognition that AD pathology precedes the diagnosis by many years, raises the possibility that non‐cognitive changes may be early and non‐invasive markers for AD or, even more provocatively, that treating non‐cognitive aspects may help to prevent or treat AD and related dementias.

Methods

A subcommittee of the Canadian Consensus Conference on Diagnosis and Treatment of Dementia reviewed areas of emerging evidence for non‐cognitive markers of dementia. We examined the literature for five non‐cognitive domains associated with future dementia: motor, sensory (hearing, vision, olfaction), neuro‐behavioral, frailty, and sleep. The Grading of Recommendations Assessment, Development, and Evaluation system was used to assign the strength of the evidence and quality of the recommendations. We provide recommendations to primary care clinics and to specialized memory clinics, answering the following main questions: (1) What are the non‐cognitive and functional changes associated with risk of developing dementia? and (2) What is the evidence that sensory, motor, behavioral, sleep, and frailty markers can serve as potential predictors of dementia?

Results

Evidence supported that gait speed, dual‐task gait speed, grip strength, frailty, neuropsychiatric symptoms, sleep measures, and hearing loss are predictors of dementia. There was insufficient evidence for recommending assessing olfactory and vision impairments as a predictor of dementia.

Conclusions

Non‐cognitive markers can assist in identifying people at risk for cognitive decline or dementia. These non‐cognitive markers may represent prodromal symptoms and several of them are potentially amenable to treatment that might delay the onset of cognitive decline.

Objectively measured sleep fragmentation is associated with incident delirium in older hospitalized patients: Analysis of data collected from an randomized controlled trial

Delirium may lead to poor outcomes in hospitalized older adults, and sleep deprivation may contribute to its pathogenesis. Thus, we sought to measure sleep duration and fragmentation using wrist-worn actigraphy in older, hospitalized patients with and without delirium, and to determine if actigraphy-based parameters could be used to predict delirium prior to clinical recognition. We conducted a secondary analysis of data from a recent, randomized clinical trial aimed at preventing inpatient delirium. Participants (n = 70) were aged ≥ 65 years admitted to an internal medicine service. Delirium was defined by the Confusion Assessment Method, or altered mental status identified by a clinician. Sleep measurements were actigraphy-based, and included total sleep time, median sleep bout duration and other measures of sleep fragmentation. We found that total sleep duration was similar between patients with (n = 17) and without (n = 53) delirium (mean 384.9 ± SD 162.7 versus mean 456.6 ± SD 135.8 min; p = .081). Mean sleep bout times were shorter in delirious versus never-delirious patients (median 6.1 [interquartile range 4.3-8.9] versus 7.9 [interquartile range 5.7-11.3] min, p = .048). Patients with delirium had more short sleep bouts (< 10 min) and fewer longer sleep bouts (> 30 min) compared with those without delirium. Increased sleep fragmentation was present prior to the clinical recognition of delirium. Overall, delirium was associated with increased sleep fragmentation detected by actigraphy, and sleep fragmentation might be useful as a biomarker for delirium prediction in the future.

Self-reported obstructive sleep apnea, amyloid and tau burden, and Alzheimer's disease time-dependent progression

INTRODUCTION

Obstructive sleep apnea (OSA) is associated with Alzheimer's disease (AD) biomarkers in cognitively normal (CN) and mild cognitive impaired (MCI) participants. However, independent and combined effects of OSA, amyloid beta (Aβ) and tau-accumulation on AD time-dependent progression risk is unclear.

METHODS

Study participants grouped by biomarker profile, as described by the A/T/N scheme, where "A" refers to aggregated Aβ, "T" aggregated tau, and "N" to neurodegeneration, included 258 CN (OSA-positive [OSA+] [A+TN+ n = 10, A+/TN- n = 6, A-/TN+ n = 10, A-/TN- n = 6 and OSA-negative [OSA-] [A+TN+ n = 84, A+/TN- n = 11, A-/TN+ n = 96, A-/TN- n = 36]) and 785 MCI (OSA+ [A+TN+ n = 35, A+/TN- n = 15, A-/TN+ n = 25, A-/TN- n = 16] and OSA- [A+TN+ n = 388, A+/TN- n = 28, A-/TN+ n = 164, A-/TN- n = 114]) older-adults from the Alzheimer's Disease Neuroimaging Initiative cohort. Cox proportional hazards regression models estimated the relative hazard of progression from CN-to-MCI and MCI-to-AD, among baseline OSA CN and MCI patients, respectively. Multi-level logistic mixed-effects models with random intercept and slope investigated the synergistic associations of self-reported OSA, Aβ, and tau burden with prospective cognitive decline.

RESULTS

Independent of TN-status (CN and MCI), OSA+/Aβ+ participants were approximately two to four times more likely to progress to MCI/AD (P < .001) and progressed 6 to 18 months earlier (P < .001), compared to other participants combined (ie, OSA+/Aβ-, OSA-/Aβ+, and OSA-/Aβ-). Notably, OSA+/Aβ- versus OSA-/Aβ- (CN and MCI) and OSA+/TN- versus OSA-/TN- (CN) participants showed no difference in the risk and time-to-MCI/AD progression. Mixed effects models demonstrated OSA synergism with Aβ (CN and MCI [β = 1.13, 95% confidence interval (CI), 0.74 to 1.52, and β = 1.18, 95%CI, 0.82 to 1.54]) respectively, and with tau (MCI [β = 1.31, 95% CI, 0.87 to 1.47]), P < .001 for all.

DISCUSSION

OSA acts in synergism with Aβ and with tau, and all three acting together result in synergistic neurodegenerative mechanisms especially as Aβ and tau accumulation becomes increasingly abnormal, thus leading to shorter progression time to MCI/AD in CN and MCI-OSA patients, respectively.

Seafarers' Physical Activity and Sleep Patterns: Results from Asia-Pacific Sea Routes

Prolonged ocean voyages constrain the regular physical activity and sleep patterns of seafarers. However, there is a lack of information on seafarers’ physical activity and sleep behavior. The purpose of this study was to systematically examine physical activity and sleep patterns among seafarers using a single wrist-worn accelerometer. Fifty-one senior maritime students (mean age = 22.8 years; 80.0% male) in a university navigation department participated in the study. Data were collected from participants on three sea voyages in the Asia-Pacific region. Indicators of moderate to vigorous intensity physical activity (MVPA) and sleep patterns were compared between several conditions: (1) moored versus sailing, (2) on-navigation duty and off- navigation duty, and (3) day versus night navigation duty. Regardless of conditions, low levels of physical activity and short sleep durations were observed. Independent sample t-tests revealed that time spent doing MVPA was significantly higher when participants were off-duty than when they were on-duty (p < 0.001). Physical activity did not significantly differ between the other two conditions. While total sleep duration was not significantly different between mooring and sailing, the results showed that participants awakened more frequently (p = 0.007) and their sleep was more restless (p < 0.001) while sailing. The results demonstrated that developing effective programs to promote physical activity should be a public health priority for the seafaring population, and serious consideration is required to mitigate sleep disruption during sailing.

Local Sleep and Alzheimer's Disease Pathophysiology

Even prior to the onset of the prodromal stages of Alzheimer's disease (AD), a constellation of sleep disturbances are apparent. A series of epidemiological studies indicate that multiple forms of these sleep disturbances are associated with increased risk for developing mild cognitive impairment (MCI) and AD, even triggering disease onset at an earlier age. Through the combination of causal manipulation studies in humans and rodents, as well as targeted examination of sleep disturbance with respect to AD biomarkers, mechanisms linking sleep disturbance to AD are beginning to emerge. In this review, we explore recent evidence linking local deficits in brain oscillatory function during sleep with local AD pathological burden and circuit-level dysfunction and degeneration. In short, three deficits in the local expression of sleep oscillations have been identified in relation to AD pathophysiology: (1) frequency-specific frontal deficits in slow wave expression during non-rapid eye movement (NREM) sleep, (2) deficits in parietal sleep spindle expression, and (3) deficits in the quality of electroencephalographic (EEG) desynchrony characteristic of REM sleep. These deficits are noteworthy since they differ from that seen in normal aging, indicating the potential presence of an abnormal aging process. How each of these are associated with β-amyloid (Aβ) and tau pathology, as well as neurodegeneration of circuits sensitive to AD pathophysiology, are examined in the present review, with a focus on the role of dysfunction within fronto-hippocampal and subcortical sleep-wake circuits. It is hypothesized that each of these local sleep deficits arise from distinct network-specific dysfunctions driven by regionally-specific accumulation of AD pathologies, as well as their associated neurodegeneration. Overall, the evolution of these local sleep deficits offer unique windows into the circuit-specific progression of distinct AD pathophysiological processes prior to AD onset, as well as their impact on brain function. This includes the potential erosion of sleep-dependent memory mechanisms, which may contribute to memory decline in AD. This review closes with a discussion of the remaining critical knowledge gaps and implications of this work for future mechanistic studies and studies implementing sleep-based treatment interventions.

Role of Ovarian Hormones in the Modulation of Sleep in Females Across the Adult Lifespan

Ovarian hormones, including 17β-estradiol, are implicated in numerous physiological processes, including sleep. Beginning at puberty, girls report more sleep complaints than boys, which is maintained throughout the reproductive life stage. Sleep problems are exacerbated during the menopausal transition, evidenced by greater risk for sleep disorders. There is emerging evidence that menopause-associated hormone loss contributes to this elevated risk, but age is also an important factor. The extent to which menopause-associated sleep disturbance persists into postmenopause above and beyond the effects of age remains unknown. Untreated sleep disturbances have important implications for cognitive health, as they are emerging as risk factors for dementia. Given that sleep loss impairs memory, an important knowledge gap concerns the role played by menopause-associated hormone loss in exacerbating sleep disturbance and, ultimately, cognitive function in aging women. In this review, we take a translational approach to illustrate the contribution of ovarian hormones in maintaining the sleep-wake cycle in younger and middle-aged females, with evidence implicating 17β-estradiol in supporting the memory-promoting effects of sleep. Sleep physiology is briefly reviewed before turning to behavioral and neural evidence from young females linking 17β-estradiol to sleep-wake cycle maintenance. Implications of menopause-associated 17β-estradiol loss is also reviewed before discussing how ovarian hormones may support the memory-promoting effects of sleep, and why menopause may exacerbate pathological aging via effects on sleep. While still in its infancy, this research area offers a new sex-based perspective on aging research, with a focus on a modifiable risk factor for pathological aging.

Are symptoms of insomnia in primary care associated with subsequent onset of dementia? A matched retrospective case-control study

Objective: There is evidence from neuroimaging studies of an association between insomnia and early dementia biomarkers, but observational studies have so far failed to show a clear association between insomnia and the later development of dementia. We investigated the association between dementia diagnosis and recording of insomnia symptoms 5-10 years earlier in primary care.Method: A case-control study using data from the Clinical Practice Research Datalink. 15,209 cases with dementia (either Alzheimer's, vascular, mixed or non-specific subtypes) at least 65 years old at time of diagnosis, were matched with the same number of controls on year of birth and gender. We ascertained the presence of insomnia symptoms during a five-year period starting 10 years before the index date. Odds ratios for developing dementia were estimated using logistic regression after controlling for hypnotic exposure and physical and mental health comorbidities.Results: The adjusted odds ratio for dementia in those with previous insomnia was 1.34 (95% CI = 1.20-1.50).Conclusion: There is an association between dementia and previous insomnia. It may be possible to incorporate insomnia into predictive tools for dementia.

The age differences of sleep disruption on mood states and memory performance

Objectives: In the present study, we explored the age differences of mood states and memory performance between younger and older adults after one night of sleep disruption.Method: Twenty-nine younger adults and 30 older adults completed mood states assessments and memory tasks before and after sleep disruption. Participants' sleep was disrupted by periodical phone calls once per hour. Sleep parameters of baseline sleep and disrupted sleep were recorded by actigraphy.Results: Regarding the mood states, older adults were less affected than younger adults, more tolerant of sleep disruption. With respect to memory, younger adults showed increased memory performance after nocturnal sleep, even if this sleep was disrupted. In contrast, older adults' sleep-related memory consolidation was impaired.Conclusion: Periodic sleep disruption for one night resulted in impaired function of older adults' sleep-related memory consolidation and younger adults' mood states. These findings shed light on the understanding of sleep function on memory and emotion. Specifically, sleep disruption might be one of the reasons for older adults' memory decline and it might also be one of the causes for younger adults' emotion disorders. Further investigations on the relationship between sleep disruption, cognitive performance and emotional well-being are needed to find potential ways to prevent and treat the sleep-related neuropsychological impairments in both younger and older adults.

Binocular Vision, Visual Function, and Pupil Dynamics in People Living With Dementia and Their Relation to the Rate of Cognitive Decline and Structural Changes Within the Brain: Protocol for an Observational Study

BACKGROUND

Visual impairment is a common comorbidity in people living with dementia. Addressing sources of visual difficulties can have a significant impact on the quality of life for people living with dementia and their caregivers. Depth perception problems are purportedly common in dementia and also contribute to falls, visuomotor task difficulties, and poorer psychosocial well-being. However, depth perception and binocular vision are rarely assessed in dementia research. Sleep fragmentation is also common for people living with dementia, and binocular cooperation for depth perception can be affected by fatigue. Pupillary responses under cognitive load also have the potential to be a risk marker for cognitive decline in people living with dementia and can be combined with the above measures for a comprehensive evaluation of clinical visual changes in people living with dementia and their relation to changes in cognitive status, sleep quality, and cortical structure or function.

OBJECTIVE

This study aims to characterize the nature of clinical visual changes and altered task-evoked pupillary responses that may occur in people living with dementia and evaluate whether these responses relate to changes in cognitive status (standardized Mini Mental State Examination [MMSE] score), Pittsburgh sleep quality index, and cortical structure or function.

METHODS

This proposed exploratory observational study will enroll ≤210 people with recently diagnosed dementia (within the last 24 months). The following parameters will be assessed on 3 occasions, 4 months apart (plus or minus 2 weeks): visual function (visual acuity and contrast sensitivity), binocular function (motor fusion and stereopsis), task-evoked pupillary responses (minimum and maximum pupil size, time to maximum dilation, and dilation velocity), cognitive status (MMSE score), and sleep quality (Pittsburgh Sleep Quality Index). A subset of patients (n=30) with Alzheimer disease will undergo structural and functional magnetic resonance imaging at first and third visits, completing a 10-day consensus sleep diary to monitor sleep quality, verified by sleep actimetry.

RESULTS

This research was funded in February 2018 and received National Health Service Research Ethics Committee approval in September 2018. The data collection period was from October 1, 2018, to November 30, 2019. A total of 24 participants were recruited for the study. The data analysis is complete, with results expected to be published before the end of 2020.

CONCLUSIONS

Findings will demonstrate how often people with dementia experience binocular vision problems. If frequent, diagnosing and treating them could improve quality of life by reducing the risk of falls and fine visuomotor task impairment and by relieving psychosocial anxiety. This research will also demonstrate whether changes in depth perception, pupillary responses, and quality of vision relate to changes in memory or sleep quality and brain structure or function. If related, these quick and noninvasive eye tests help monitor dementia. This would help justify whether binocular vision and pupillary response testing should be included in dementia-friendly eye-testing guidelines.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR1-10.2196/16089.

Sleep and the aging brain. A multifaceted approach

In the current review we provide a theoretical background on studies examining the association between sleep and brain function. We focus on the association between sleep and cognitive performance, cognitive changes over time and incident dementia as well. We then present some data on the link between sleep and subjective cognitive complaints, in participants without any objective clinical cognitive decline. We conclude with investigating the association between sleep and brain biomarkers, by highlighting the importance of specific genes and specific brain regions' morphometry. The role of sleep is vital in maintaining a healthy aging brain, and multiple factors should be taken under account when investigating this association.

Impact of circadian and diurnal rhythms on cellular metabolic function and neurodegenerative diseases

The 24-h rotational period of the earth has driven evolution of biological systems that serve to synchronize organismal physiology and behavior to this predictable environmental event. In mammals, the circadian (circa, "about" and dia, "a day") clock keeps 24-h time at the organismal and cellular level, optimizing biological function for a given time of day. The most obvious circadian output is the sleep-wake cycle, though countless bodily functions, ranging from hormone levels to cognitive function, are influenced by the circadian clock. Here we discuss the regulation of metabolic pathways by the circadian clock, discuss the evidence implicating circadian and sleep disruption in neurodegenerative diseases, and suggest some possible connections between the clock, metabolism, and neurodegenerative disease.

Sleep, Noninvasive Brain Stimulation, and the Aging Brain: Challenges and Opportunities

As we age, sleep patterns undergo severe modifications of their micro and macrostructure, with an overall lighter and more fragmented sleep structure. In general, interventions targeting sleep represent an excellent opportunity not only to maintain life quality in the healthy aging population, but also to enhance cognitive performance and, when pathology arises, to potentially prevent/slow down conversion from e.g. Mild Cognitive Impairment (MCI) to Alzheimer's Disease (AD). Sleep abnormalities are, in fact, one of the earliest recognizable biomarkers of dementia, being also partially responsible for a cascade of cortical events that worsen dementia pathophysiology, including impaired clearance systems leading to build-up of extracellular amyloid-β (Aβ) peptide and intracellular hyperphosphorylated tau proteins. In this context, Noninvasive Brain Stimulation (NiBS) techniques, such as transcranial electrical stimulation (tES) and transcranial magnetic stimulation (TMS), may help investigate the neural substrates of sleep, identify sleep-related pathology biomarkers, and ultimately help patients and healthy elderly individuals to restore sleep quality and cognitive performance. However, brain stimulation applications during sleep have so far not been fully investigated in healthy elderly cohorts, nor tested in AD patients or other related dementias. The manuscript discusses the role of sleep in normal and pathological aging, reviewing available evidence of NiBS applications during both wakefulness and sleep in healthy elderly individuals as well as in MCI/AD patients. Rationale and details for potential future brain stimulation studies targeting sleep alterations in the aging brain are discussed, including enhancement of cognitive performance, overall quality of life as well as protein clearance.

Circadian Rhythms of Perineuronal Net Composition

Perineuronal nets (PNNs) are extracellular matrix (ECM) structures that envelop neurons and regulate synaptic functions. Long thought to be stable structures, PNNs have been recently shown to respond dynamically during learning, potentially regulating the formation of new synapses. We postulated that PNNs vary during sleep, a period of active synaptic modification. Notably, PNN components are cleaved by matrix proteases such as the protease cathepsin-S. This protease is diurnally expressed in the mouse cortex, coinciding with dendritic spine density rhythms. Thus, cathepsin-S may contribute to PNN remodeling during sleep, mediating synaptic reorganization. These studies were designed to test the hypothesis that PNN numbers vary in a diurnal manner in the rodent and human brain, as well as in a circadian manner in the rodent brain, and that these rhythms are disrupted by sleep deprivation. In mice, we observed diurnal and circadian rhythms of PNNs labeled with the lectin Wisteria floribunda agglutinin (WFA+ PNNs) in several brain regions involved in emotional memory processing. Sleep deprivation prevented the daytime decrease of WFA+ PNNs and enhances fear memory extinction. Diurnal rhythms of cathepsin-S expression in microglia were observed in the same brain regions, opposite to PNN rhythms. Finally, incubation of mouse sections with cathepsin-S eliminated PNN labeling. In humans, WFA+ PNNs showed a diurnal rhythm in the amygdala and thalamic reticular nucleus (TRN). Our results demonstrate that PNNs vary in a circadian manner and this is disrupted by sleep deprivation. We suggest that rhythmic modification of PNNs may contribute to memory consolidation during sleep.

Sleep Fragmentation and Cognitive Trajectories After Critical Illness

BACKGROUND

ICU survivors can experience both cognitive dysfunction and persistent sleep disturbances after hospitalization. Sleep disturbances have been linked with cognitive impairment in various patient populations, and the apolipoprotein E (APOE) genotype has been linked to sleep-related impairments in cognition.

RESEARCH QUESTION

Is there an association between sleep, long-term cognition, and APOE status in ICU survivors?

STUDY DESIGN AND METHODS

We enrolled 150 patients from five centers who had been mechanically ventilated for at least 3 days; 102 patients survived to ICU discharge. Actigraphy and cognitive testing were undertaken at 7 days, 6 months, and 12 months after ICU discharge, and sleep duration, quality, and timing were estimated by actigraphy. APOE single nucleotide polymorphisms were assessed for each patient.

RESULTS

Actigraphy-estimated sleep fragmentation, but not total sleep time or interdaily stability (estimate of circadian rhythmicity), was associated with worse cognitive impairment at 7 days of ICU discharge. No actigraphy-estimated variable of sleep estimation at 7 days post-ICU discharge predicted cognitive impairment or persistent sleep abnormalities at 6 and 12 months of follow-up in subsequently assessed survivors. Possessing the APOE ε4 allele was not significantly associated with sleep disturbances and its presence did not modify the risk of sleep-related cognitive impairment at follow-up.

INTERPRETATION

Sleep fragmentation estimated by actigraphy was associated with worse cognitive performance in hospital, but not at later time intervals. Further research is needed to better delineate the relationship between persistent sleep disturbances and cognition in larger numbers of ICU survivors.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02086877; URL: www.clinicaltrials.gov.