Apolipoprotein E ɛ4 (APOE ɛ4) Allele is Associated with Long Sleep Duration Among Elderly with Cognitive Impairment

Objectively measured prolonged sleep is associated with plasma cytokines in older adults with mild cognitive impairment

This study aimed to determine whether objective sleep time is associated with the concentrations of various plasma cytokines in older adults with mild cognitive impairment (MCI). In total, 118 adults with MCI (66 women; mean age: 75.7 years) participated in this prospective cohort study. All participants were required to wear a wristband sensor for 7.8 days, on average, every 3 months for 1 year and undergo measurement of 27 plasma cytokines using multiplex immunoassays. After adjusting for potential confounders, the associations of total sleep time with cytokine concentrations were assessed by multiple linear regression analysis. The total sleep time was significantly correlated with plasma interleukin (IL)-9 and macrophage inflammatory protein (MIP)-1β levels (r = 0.239, p = 0.009, and r = 0.242, p = 0.008, respectively). Moreover, these associations remained significant after adjusting for covariates, including demographic characteristics, lifestyle-related diseases, and apolipoprotein E status (β = 0.272, 95% confidence interval: 0.095-0.448, p = 0.003, and β = 0.27, 95% confidence interval: 0.092-0.449, p = 0.003, respectively). Thus, this study is the first to demonstrate the association between objective prolonged sleep and higher plasma IL-9 and MIP-1β levels in older adults with MCI.

Day-to-day sleep variability with Alzheimer's biomarkers in at-risk elderly

INTRODUCTION

Measuring day-to-day sleep variability might reveal unstable sleep-wake cycles reflecting neurodegenerative processes. We evaluated the association between Alzheimer's disease (AD) fluid biomarkers with day-to-day sleep variability.

METHODS

In the PREVENT-AD cohort, 203 dementia-free participants (age: 68.3 ± 5.4; 78 males) with a parental history of sporadic AD were tested with actigraphy and fluid biomarkers. Day-to-day variability (standard deviations over a week) was assessed for sleep midpoint, duration, efficiency, and nighttime activity count.

RESULTS

Lower cerebrospinal fluid (CSF) ApoE, higher CSF p-tau181/amyloid-β (Aβ)42, and higher plasma p-tau231/Aβ42 were associated with higher variability of sleep midpoint, sleep duration, and/or activity count. The associations between fluid biomarkers with greater sleep duration variability were especially observed in those that carried the APOE4 allele, mild cognitive impairment converters, or those with gray matter atrophy.

DISCUSSION

Day-to-day sleep variability were associated with biomarkers of AD in at-risk individuals, suggesting that unstable sleep promotes neurodegeneration or, conversely, that AD neuropathology disrupts sleep-wake cycles.

Roles of ApoE4 on the Pathogenesis in Alzheimer's Disease and the Potential Therapeutic Approaches

The Apolipoprotein E ε4 (ApoE ε4) allele, encoding ApoE4, is the strongest genetic risk factor for late-onset Alzheimer's disease (LOAD). Emerging epidemiological evidence indicated that ApoE4 contributes to AD through influencing β-amyloid (Aβ) deposition and clearance. However, the molecular mechanisms of ApoE4 involved in AD pathogenesis remains unclear. Here, we introduced the structure and functions of ApoE isoforms, and then we reviewed the potential mechanisms of ApoE4 in the AD pathogenesis, including the effect of ApoE4 on Aβ pathology, and tau phosphorylation, oxidative stress; synaptic function, cholesterol transport, and mitochondrial dysfunction; sleep disturbances and cerebrovascular integrity in the AD brains. Furthermore, we discussed the available strategies for AD treatments that target to ApoE4. In general, this review overviews the potential roles of ApoE4 in the AD development and suggests some therapeutic approaches for AD. ApoE4 is genetic risk of AD. ApoE4 is involved in the AD pathogenesis. Aβ deposition, NFT, oxidative stress, abnormal cholesterol, mitochondrial dysfunction and neuroinflammation could be observed in the brains with ApoE4. Targeting the interaction of ApoE4 with the AD pathology is available strategy for AD treatments.

Cretan Aging Cohort-Phase III: Methodology and Descriptive Characteristics of a Long-Term Longitudinal Study on Predictors of Cognitive Decline in Non-Demented Elderly from Crete, Greece

Identifying modifiable factors that may predict long-term cognitive decline in the elderly with adequate daily functionality is critical. Such factors may include poor sleep quality and quantity, sleep-related breathing disorders, inflammatory cytokines and stress hormones, as well as mental health problems. This work reports the methodology and descriptive characteristics of a long-term, multidisciplinary study on modifiable risk factors for cognitive status progression, focusing on the 7-year follow-up. Participants were recruited from a large community-dwelling cohort residing in Crete, Greece (CAC; Cretan Aging Cohort). Baseline assessments were conducted in 2013-2014 (Phase I and II, circa 6-month time interval) and follow-up in 2020-2022 (Phase III). In total, 151 individuals completed the Phase III evaluation. Of those, 71 were cognitively non-impaired (CNI group) in Phase II and 80 had been diagnosed with mild cognitive impairment (MCI). In addition to sociodemographic, lifestyle, medical, neuropsychological, and neuropsychiatric data, objective sleep was assessed based on actigraphy (Phase II and III) and home polysomnography (Phase III), while inflammation markers and stress hormones were measured in both phases. Despite the homogeneity of the sample in most sociodemographic indices, MCI persons were significantly older (mean age = 75.03 years, SD = 6.34) and genetically predisposed for cognitive deterioration (APOE ε4 allele carriership). Also, at follow-up, we detected a significant increase in self-reported anxiety symptoms along with a substantial rise in psychotropic medication use and incidence of major medical morbidities. The longitudinal design of the CAC study may provide significant data on possible modifiable factors in the course of cognitive progression in the community-dwelling elderly.

ApoE in Alzheimer’s disease: pathophysiology and therapeutic strategies

Alzheimer’s disease (AD) is the most common cause of dementia worldwide, and its prevalence is rapidly increasing due to extended lifespans. Among the increasing number of genetic risk factors identified, the apolipoprotein E (APOE) gene remains the strongest and most prevalent, impacting more than half of all AD cases. While the ε4 allele of the APOE gene significantly increases AD risk, the ε2 allele is protective relative to the common ε3 allele. These gene alleles encode three apoE protein isoforms that differ at two amino acid positions. The primary physiological function of apoE is to mediate lipid transport in the brain and periphery; however, additional functions of apoE in diverse biological functions have been recognized. Pathogenically, apoE seeds amyloid-β (Aβ) plaques in the brain with apoE4 driving earlier and more abundant amyloids. ApoE isoforms also have differential effects on multiple Aβ-related or Aβ-independent pathways. The complexity of apoE biology and pathobiology presents challenges to designing effective apoE-targeted therapeutic strategies. This review examines the key pathobiological pathways of apoE and related targeting strategies with a specific focus on the latest technological advances and tools.

Bidirectional relationship between nocturnal subjective sleep duration and cognitive performance in Chinese over 45 years old: a national representative longitudinal study

Introduction

Previous studies have inconsistent associations between changes in sleep duration and cognitive function and have not separated interindividual effects from intraindividual effects. This study aimed to examine the bidirectional associations between subjective night sleep duration and cognitive function while differing intraindividual and interindividual effects.

Methods

A national representative sample was obtained from China Health and Retirement Longitudinal Study during 2011–2018. Night sleep duration and potential confounders were assessed and collected by questionnaires. Cognition was assessed in three categories (orientation, executive function, and memory), and z scores were used for global cognitive performance. The random intercept cross-lagged panel model was used to examine the temporal associations during 2011–2018.

Results

Across 9404 participants over 45, at interindividual level, moderate (β= -0.014) and long sleepers (β= -0.06) had positive association between sleep duration and cognitive decline after adjusted covariates, but short sleepers had negative associations between sleep duration and cognitive decline (β = 0.87). At intraindividual level, prolonged sleep duration predicted better cognition for short (β= -0.021 at wave2-3; β= -0.04 at wave3-4) and moderate (β= -0.017 at wave3-4) sleepers.

Conclusion

For short sleepers, longer subjective nocturnal sleep duration predicted better cognitive performance; but moderate and long sleepers showed opposite results—short and moderate sleepers with prolonged subjective nocturnal sleep duration would have later cognitive decline. Our findings tentatively suggested that an increased subjective night sleep duration and subjective long sleep duration could be regarded as useful tools for identifying middle- and old adults at higher risks of progressing to cognitive decline.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-03468-8.

Association between the self-reported duration and quality of sleep and cognitive function among middle-aged and older adults in China

BACKGROUND

The World Alzheimer Report showed that 46.8 million people suffered from dementia in 2015. This study examined how the duration and quality of sleep are associated with cognition among older adults in China.

METHOD

Data were drawn from waves 2011, 2013, and 2015 of the China Health and Retirement Longitudinal Study (CHARLS), including noninstitutionalized adults aged 45 and older (n=10,768). Cognition was measured by interview-based assessments of mental status (TICS-10), episodic memory, and visuospatial abilities. Sleep duration was categorized as long, medium, or short and sleep quality was categorized as good, fair, or poor.

RESULTS

Sleep duration had an inverted U-shape relationship with cognitive scores (P <.001); and sleep quality had a positive linear relationship with cognitive scores (P <.001). Short and long sleep durations were associated with consistently lower cognition scores with increasing age (both P <.001); and fair and poor quality of sleep were associated with consistently lower levels of cognition (both P <.001). Tests of interactions between sleep duration and sleep quality showed that participants reporting long durations of sleep with poor quality of sleep had the lowest overall cognitive scores.

LIMITATIONS

Self-reported methods were used to measure sleep quality and duration and thus our findings underscore the need for more evidence-based research to improve prevention efforts and tailor interventions to reduce cognitive decline among Chinese older adults.

CONCLUSIONS

Suboptimal sleep duration and quality were associated with poor cognition. Cognitive scores were lowest among those who reported long durations of sleep that were of poor quality.

The Relationship Between Sleep Disturbance and Apolipoprotein E ε4 in Adults With Mild Cognitive Impairment and Alzheimer's Disease Dementia: An Integrative Review

BACKGROUND

Apolipoprotein E ε4 (APOE ε4) was shown to be a risk factor for mild cognitive impairment (MCI) and Alzheimer's disease (AD) dementia. When coupled with sleep disturbance, APOE ε4 posed additional risks to cognitive impairment. But the literature on the association between sleep disturbance and the APOE ε4 status of persons who are cognitively impaired has not yet been systematically examined.

OBJECTIVES

To explore and synthesize the relationship between sleep disturbance and APOE ε4 status of adults with MCI and AD.

METHODS

An integrative review was guided by Whittemore and Knafl's methodology. Systematic searches identified studies with multiple sources published before May 20, 2021. A matrix and narrative synthesis was employed to organize and synthesize the findings. Joanna Briggs Institute (JBI) Critical Appraisal tools (2020) were used to evaluate the quality of the selected studies.

RESULTS

A total of 7 studies were included. APOE ε4 was associated with poor sleep quality in terms of the deterioration of nighttime total sleep time, 24-hour total sleep time, rapid eye movement, sleep efficiency, sleep latency, and wake after sleep onset in a population with MCI or AD. The interacted and adjusted relationship between sleep disturbance and APOE ε4 on the progression of cognitive decline was inconsistent.

CONCLUSIONS

There is evidence to support an association between sleep disturbance and APOE ε4 in individuals with cognitive impairment, but a further examination of the relationship between sleep parameters and APOE ε4 is warranted, especially as the causal or dose-response relationship remains unclear.

Non-Pharmacological Treatments of Neuropsychiatric Symptoms in Mild Cognitive Impairment (MCI)

Mild cognitive impairment (MCI) is a syndrome defined by objective cognitive deficits that do not impact functional independence. Individuals with MCI develop dementia at an annual rate of 10 to 15%. Neuropsychiatric symptoms (NPS) are common non-cognitive features of neurocognitive disorders and have a major impact on the wellbeing and quality of life of affected individuals and their families. Non-pharmacological interventions for NPS are considered the first-line treatment because of the limited efficacy and side-effect potential of current pharmacological agents. This article summarizes the literature on non-pharmacological treatments for NPS in MCI. The limited number of studies specific to individuals with MCI and its various etiologies, as well as the overall heterogeneity of research design and methodologies, make the evidence base inconclusive. Nevertheless, some studies support psychosocial interventions aimed at individuals with MCI and their caregivers.

Insomnia symptom severity and cognitive performance: Moderating role of APOE genotype

INTRODUCTION

We evaluated whether insomnia symptom severity was associated with cognitive function, and whether this relationship was modified by biomarkers associated with Alzheimer's disease risk.

METHODS

We examined insomnia symptoms and neuropsychological performance 3.4 years later in 511 dementia-free Framingham Heart Study participants (62.65 ± 8.7 years, 50.9% male). Additionally, we explored insomnia symptoms combined with self-reported short habitual sleep duration and effect modification by apolipoprotein E (APOE) ε4 allele status.

RESULTS

More severe insomnia symptoms were associated with lower performance on global cognition, and immediate and delayed Logical Memory recall, especially when insomnia symptoms were combined with short sleep duration. The association between insomnia symptoms and poorer memory recall was more pronounced in APOE ε4 allele carriers.

DISCUSSION

Insomnia symptom severity was associated with worse subsequent global cognitive and memory performance, which was especially apparent in APOE ε4 allele carriers, suggesting that poor sleep might be particularly detrimental when the brain is already vulnerable to neurodegeneration.

Poor Diet, Long Sleep, and Lack of Physical Activity Are Associated with Inflammation among Non-Demented Community-Dwelling Elderly

Inflammation in elderly is associated with physical and cognitive morbidity and mortality. We aimed to explore the association of modifiable lifestyle parameters with inflammation among non-demented, community-dwelling elderly. A sub-sample of 117 patients with mild cognitive impairment (MCI, n = 63) and cognitively non-impaired controls (CNI, n = 54) were recruited from a large, population-based cohort in Crete, Greece, of 3140 elders (>60 years old). All participants underwent assessment of medical history/physical examination, extensive neuropsychiatric/neuropsychological evaluation, diet, three-day 24-h actigraphy, subjective sleep, physical activity, and measurement of IL-6 and TNFα plasma levels. Associations between inflammatory markers and diet, objective sleep duration, subjective sleep quality, and lack of physical activity were assessed using multivariate models. Regression analyses in the total group revealed significant associations between TNF-α and low vegetable consumption (p = 0.003), and marginally with objective long nighttime sleep duration (p = 0.04). In addition, IL-6 was associated with low vegetable consumption (p = 0.001) and lack of physical activity (p = 0.001). Poor diet and lack of physical activity appear to be modifiable risk factors of inflammation, whereas long sleep appears to be a marker of increased inflammatory response in elderly. Our findings may have clinical implications given the association of inflammatory response with morbidity, including cognitive decline, and mortality in elderly.