Sleep characteristics and risk of dementia and Alzheimer's disease: The Atherosclerosis Risk in Communities Study

Association between a healthy lifestyle and dementia in older adults with obesity: A prospective study in the UK biobank

BACKGROUND

The impact of adherence to low-risk lifestyle factors on dementia risk in individuals with obesity remains unclear. We aimed to explore the association between healthy lifestyles with dementia in obese participants.

METHODS

Dementia-free participants from the UK Biobank, aged 50 years or older with obesity (BMI ≥30 kg/m2) at baseline were included. A weighted healthy lifestyle score was calculated incorporating both traditional and emerging lifestyle factors. The primary outcome was all-cause dementia and its subtypes (Alzheimer's disease and Vascular dementia). Cox regression models analyzed the association between healthy lifestyle scores and dementia risk. Restricted cubic splines tested the dose-response. We also examined the effect of lifestyle scores on dementia risk in individuals with normal weight and overweight.

RESULTS

A total of 54,365 participants were included at baseline. During a median follow-up of 14.4 years, 1271 participants developed all-cause dementia, including 537 cases of Alzheimer's disease and 343 cases of vascular dementia. A 20 % increase in the lifestyle score was associated with a 7 % reduction in dementia risk (HR: 0.93; 95 % CI: 0.91,0.96) and a 4 % reduction in Alzheimer's disease risk (HR: 0.96; 95 % CI: 0.92,1.00). The association was stronger in overweight and obese participants. No significant link was found for vascular dementia.

LIMITATIONS

Information on lifestyle behaviors was self-reported and might be prone to measurement error.

CONCLUSIONS

Adherence to a healthy lifestyle may reduce the risk of dementia and Alzheimer's disease in older obese individuals, with a stronger effect observed in those with higher lifestyle scores.

Glymphatic pathway dysfunction in severe obstructive sleep apnea: A meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA), a sleep disorder, is associated with cognitive decline and is potentially linked to glymphatic system dysfunction. This meta-analysis investigates glymphatic function in severe OSA (apnea-hypopnea index ≥30) using the Diffusion Tensor Imaging Analysis along the Perivascular Space (DTI-ALPS) index.

METHODS

This study followed PRISMA guidelines for systematic reviews and meta-analyses. A comprehensive search of PubMed, Web of Science, Scopus, and Embase was conducted from inception to January 20, 2024. Studies investigating the ALPS index in OSA using DTI were included. Analyses included a random-effects meta-analysis, sensitivity analysis, meta-regression, publication bias evaluation (funnel plot, Egger's test, and Begg's test), and risk of bias assessment.

RESULTS

Systematic review identified four studies (137 patients with severe OSA and 170 healthy controls (HCs)). Pooled analysis revealed a significant reduction in the DTI-ALPS index in severe OSA patients compared to HCs (standardized mean difference: -0.95, 95 % CI: -1.46 to -0.44, p < 0.001), indicating impaired glymphatic function. Heterogeneity was moderate to high (I2 = 76.07 %), but sensitivity analyses confirmed robustness. Meta-regression analyses identified the sources of heterogeneity as the apnea-hypopnea index (β = -0.039, p = 0.009) and the Epworth Sleepiness Scale (β = -0.150, p = 0.032), with no effects observed for age or male ratio. Qualitative (funnel plot) and quantitative publication bias assessments (Egger's and Begg's tests) showed no significant bias, and risk of bias evaluations using the Newcastle-Ottawa Scale indicated high methodological quality across studies.

CONCLUSIONS

These findings suggest that severe OSA disrupts glymphatic activity. The DTI-ALPS index emerges as a promising tool for assessing glymphatic dysfunction in OSA.

Exploring the nexus: Sleep disorders, circadian dysregulation, and Alzheimer's disease

We reviewed the connections among Alzheimer's disease (AD), sleep deprivation, and circadian rhythm disorders. Evidence is mounting that disrupted sleep and abnormal circadian rhythms are not merely symptoms of AD, but are also involved in accelerating the disease. Amyloid-beta (Aβ) accumulates, a feature of AD, and worsens with sleep deprivation because glymphatic withdrawal is required to clear toxic proteins from the brain. In addition, disturbances in circadian rhythm can contribute to the induction of neuroinflammation and oxidative stress, thereby accelerating neurodegenerative processes. While these interactions are bidirectional, Alzheimer's pathology further disrupts sleep and circadian function in a vicious cycle that worsens cognitive decline, which is emphasized in the review. The evidence that targeting sleep and circadian mechanisms may serve as therapeutic strategies for AD was strengthened by this study through the analysis of the molecular and physiological pathways. Further work on this nexus could help unravel the neurobiological mechanisms common to the onset of Alzheimer's and disrupted sleep and circadian regulation, which could result in earlier intervention to slow or prevent the onset of the disease.

Sex differences in sleep apnea and Alzheimer's Disease: role of cerebrovascular dysfunction

Obstructive sleep apnea (OSA) significantly impacts cardiovascular health in post-menopausal females. Given that cardiovascular and cerebrovascular diseases are tightly linked, OSA-mediated impacts on cerebrovascular function and Alzheimer's Disease (AD) risk are also likely more manifest in females. This review will: summarize sex differences in cerebrovascular function, review the vascular hypothesis of AD, characterize sex differences in the OSA phenotype and implications for cerebrovascular control, and highlight OSA-mediated AD risk.

Intranasal NAP (Davunetide): Neuroprotection and circadian rhythmicity

In this review we examine the neuroprotective potential of NAP (davunetide), a small peptide derived from Activity-Dependent Neuroprotective Protein (ADNP), in the context of neurodevelopmental and neurodegenerative disorders. ADNP, a protein essential for brain development and function, is associated with tauopathy-related diseases, such as Alzheimer's Disease (AD), and circadian rhythm regulation. NAP enhances microtubule stability and prevents tauopathy. In preclinical studies, NAP shows promise in improving cognitive performance and correcting behavioral deficits in different models. Clinical studies on NAP (davunetide) administered via intranasal delivery have demonstrated its safety, favorable bioavailability, and potential efficacy in improving cognitive function, making it a viable therapeutic option. In the pure tauopathy, progressive supranuclear palsy, NAP (davunetide) significantly slowed disease progression in women in a phase II-III clinical trial. Additionally, the complex interactions between ADNP, associated pathways, and circadian regulation and the extensive NAP compensation upon ADNP deficiency attest to further clinical development. Thus, NAP is an example of a reductionist approach in drug delivery, replacing/enhancing the critical large ADNP-related pathways including dysregulated microtubules and tauopathy with a small brain bioavailable investigational drug, davunetide.

Sleep as the Foundation of Brain Health

Sleep is a vital function, taking about one-third of a human lifetime, and is essential for achieving and maintaining brain health. From homeostatic neurophysiology to emotional and procedural memory processing to clearance of brain waste, sleep and circadian alignment remain paramount. Yet modern lifestyles and clinical practice often dismiss sleep, resulting in profound long-term repercussions. This chapter examines the roles of sleep and circadian rhythms in memory consolidation, synaptic plasticity, and clearance of metabolic waste, highlighting recent advances in neuroscience research. We explore how insufficient and disordered sleep-a public health concern-can impair cognition, escalate neurodegenerative risks, and compromise neurovascular integrity, thereby impacting brain health. These findings underscore the need for comprehensive screening for disturbed sleep and targeted interventions in clinical practice. Emerging interventions and AI-driven technologies may allow early detection and personalized and individualized treatments and improve outcomes. Overall, this chapter reaffirms that healthy sleep is indispensable at any level of neurological disease prevention-on par with the role of diet and exercise in cardiovascular health-and represents the foundation of brain health.

Individual Sleep Problems Are Associated With an Accelerated Decline in Multiple Cognitive Functions in Older Adults

Poor sleep is a known risk factor of cognitive disorders, but the role of individual sleep problems in age-related cognitive changes remains unclear. This study used two complementary statistical models to estimate nonlinear trajectories of decline in four domains of cognitive functioning in the age period between 55 and 100 years depending on the severity of problems with falling asleep, night awakenings, and early morning awakenings, and short/long sleep duration. The sample included 5132 older adults (M = 67 years, 48% male) from the Longitudinal Aging Study Amsterdam (LASA), assessed 4-10 times every 2-3 years. Sleep problems were self-reported, and cognitive functioning was measured with the 15-Word test (reflecting episodic memory as immediate and delayed recall), Coding task (information processing speed) and Mini-mental State Examination/MMSE (global cognition). Data were analysed using quadratic and piecewise changepoint mixed models. The piecewise models provided more precise and interpretable findings. Decline in information processing speed accelerated significantly earlier in participants with short sleep duration (regression coefficient (B) = -2.3[95% confidence interval (CI): -3.86; -0.81]; p < 0.01) and faster with more severe early morning awakenings (B = -0.07 [-0.1; -0.03]; p < 0.01). Decline in immediate recall accelerated earlier in those with short sleep (B = -2.8 [-4.44; -1.14]; p < 0.01) and severe problems with falling asleep (B = -1.22 [-2.06; -0.39]; p = 0.01). Decline in delayed recall was faster with long sleep (B = -0.06 [-0.08;-0.03]; p < 0.01). Decline in global cognition accelerated faster in those with short/long sleep duration (B = -0.07 [-0.13; -0.01]/-0.10 [-0.18; -0.03]; p < 0.01) and severe night awakenings (B = -0.04 [-0.07;-0.02]; p < 0.01). To conclude, this study showed that some sleep problems can differentially predict earlier acceleration of deterioration in specific cognitive functions in older adults.

Sleep disorders in rheumatoid arthritis: Incidence, risk factors and association with dementia

BACKGROUND/OBJECTIVE

We aimed to examine the incidence of sleep disorders (SD) in individuals with rheumatoid arthritis (RA) vs. non-RA comparators, evaluate risk factors for SD, and assess the association between incident SD and dementia in RA.

METHODS

This retrospective cohort study included residents aged ≥50 years within an 8-county region of Minnesota who first met the 1987 ACR criteria for RA in 1980-2014. Individuals with RA were matched 1:1 with non-RA individuals on age, sex, and calendar year of RA incidence. Data on SD, cardiovascular disease (CVD) risk factors, CVD and other comorbidities were collected from the medical records.

RESULTS

Nine hundred thirteen individuals with RA and 913 non-RA comparators were included (mean age: 65 years, 65 % female in both cohorts). During the median follow-up of 10.4 years in RA and 11.0 years in non-RA cohort, SD developed in 234 and 206 individuals, respectively. RA patients experienced an increased risk for any incident SD (HR 1.34; 95 % CI:1.11-1.61) and insomnia (HR 1.34; 95 % CI:1.03-1.73). Obesity, dyslipidemia, presence of CVD, depression, anxiety, and more recent calendar year of RA incidence were associated with increased risk of any SD in RA. There were no significant association between SD overall and by subtype with dementia in RA.

CONCLUSION

Individuals with RA (vs non-RA) experienced a significantly increased risk for any SD, particularly insomnia. CVD and CVD risk factors, as well as depression and anxiety increased the risk for incident SD in RA. There was no significant association between SD and dementia in RA.

Sleep Alterations and Cognitive Decline

Sleep disturbances and cognitive decline are intricately connected, and both are prevalent in aging populations and individuals with neurodegenerative disorders such as Alzheimer's disease (AD) and other dementias. Sleep is vital for cognitive functions including memory consolidation, executive function, and attention. Disruption in these processes is associated with cognitive decline, although causal evidence is mixed. This review delves into the bidirectional relationship between alterations in sleep and cognitive impairment, exploring key mechanisms such as amyloid-β accumulation, tau pathology, synaptic homeostasis, neurotransmitter dysregulation, oxidative stress, and vascular contributions. Evidence from both experimental research and population-based studies underscores the necessity of early interventions targeting sleep to mitigate risks of neurodegenerative diseases. A deeper understanding of the interplay between sleep and cognitive health may pave the way for innovative strategies to prevent or reduce cognitive decline through improved sleep management.

The Role of the Glymphatic System in Perioperative Neurocognitive Disorders

BACKGROUND

The glymphatic system plays a crucial role in clearing metabolic waste from the central nervous system and is most active during sleep. Patients with obstructive sleep apnea (OSA) have a dysfunctional glymphatic system that correlates with disease severity. In addition, these patients have worse outcomes after surgery. The status of the glymphatic system during the perioperative period is unclear and can be examined with magnetic resonance imaging (MRI)-based diffusion tensor imaging (DTI). This study assessed perioperative glymphatic system changes in OSA surgical patients and possible relationships with perioperative neurocognitive disorders.

METHODS

DTI data from 13 OSA patients having laparoscopic abdominal surgery with general anesthesia were acquired and analyzed using a 3.0-T MRI scanner. Diffusivity maps in the x -axis (D xx ), y -axis (D yy ), z -axis (D zz ), x - y axis (D xy ), y - z axis (D yz ), and x - z axis (D xz ) were calculated. Diffusion values for the projection and association fibers were extracted, and DTI analysis along the perivascular space (ALPS) was performed. The patients' cognition was assessed using the Montreal Cognitive Assessment tool. Evaluations were carried out within 5 days before surgery and within the first 48 hours after surgery.

RESULTS

The ALPS index decreased after surgery, and this correlated with a decrease in general cognition scores and specific memory domains, including visuospatial and delayed recall.

CONCLUSIONS

The glymphatic system in OSA patients is worsened after surgery and this may contribute to an increased risk for long-term postoperative cognitive disorders. This study suggest that the glymphatic system might play a role in the pathophysiology of perioperative neurocognitive disorders and be a potential therapeutic target.

Age at diagnosis of obstructive sleep apnea and subsequent risk of dementia

BACKGROUND

Epidemiological evidence regarding the association between Obstructive sleep apnea (OSA) onset age and risk of incident dementia remains unexplored. The study sought to examine whether younger onset age of OSA is associated with a higher risk of incident dementia.

METHODS

This cohort study, based on the UK Biobank's prospective population data, excluded 445,023 participants due to baseline dementia diagnoses, incomplete covariate information, or pre-OSA onset dementia over a 12.6-year median follow-up. The research applied Cox regression and propensity score matching to explore the relationship between sleep apnea onset age and later development of all-cause dementia, Alzheimer's, and vascular dementia.

RESULTS

In a controlled study contrasting those without obstructive sleep apnea (OSA), those suffering from OSA showed markedly higher risks for developing all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VD), with hazard ratios (HR) of 4.243 (95% CI: 3.678-4.897), 5.668 (95% CI: 4.380-7.336), and 6.064 (95% CI: 4.008-9.175) respectively. Following adjustment with propensity score matching, OSA patients younger than 52 presented the highest risk of all-cause dementia, with an adjusted HR of 2.256 (95% CI: 1.901-3.747). This trend was consistent for early-onset AD and VD in the same age group.

CONCLUSION

Younger age at OSA onset was associated with increased risk of dementia. Individuals with an onset age of OSA before 52 years of age may represent a particularly vulnerable population for dementia irrespective of subtypes and need careful monitoring and timely intervention to attenuate subsequent risk of incident dementia.

Functional and vascular neuroimaging in maritime pilots with long-term sleep disruption

The mechanism underlying the possible causal association between long-term sleep disruption and Alzheimer's disease remains unclear Musiek et al. 2015. A hypothesised pathway through increased brain amyloid load was not confirmed in previous work in our cohort of maritime pilots with long-term work-related sleep disruption Thomas et al. Alzheimer's Res Ther 2020;12:101. Here, using functional MRI, T2-FLAIR, and arterial spin labeling MRI scans, we explored alternative neuroimaging biomarkers related to both sleep disruption and AD: resting-state network co-activation and between-network connectivity of the default mode network (DMN), salience network (SAL) and frontoparietal network (FPN), vascular damage and cerebral blood flow (CBF). We acquired data of 16 maritime pilots (56 ± 2.3 years old) with work-related long-term sleep disruption (23 ± 4.8 working years) and 16 healthy controls (59 ± 3.3 years old), with normal sleep patterns (Pittsburgh Sleep Quality Index ≤ 5). Maritime pilots did not show altered co-activation in either the DMN, FPN, or SAL and no differences in between-network connectivity. We did not detect increased markers of vascular damage in maritime pilots, and additionally, maritime pilots did not show altered CBF-patterns compared to healthy controls. In summary, maritime pilots with long-term sleep disruption did not show neuroimaging markers indicative of preclinical AD compared to healthy controls. These findings do not resemble those of short-term sleep deprivation studies. This could be due to resiliency to sleep disruption or selection bias, as participants have already been exposed to and were able to deal with sleep disruption for multiple years, or to compensatory mechanisms Mentink et al. PLoS ONE. 2021;15(12):e0237622. This suggests the relationship between sleep disruption and AD is not as strong as previously implied in studies on short-term sleep deprivation, which would be beneficial for all shift workers suffering from work-related sleep disruptions.

Obstructive sleep apnea and cerebral small vessel disease in community-based older people: an aspirin in reducing events in the elderly imaging substudy

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) may increase the risk of dementia. A potential pathway for this risk is through cerebral small vessel disease (CSVD). In the context of an existing randomized trial of aspirin for primary prevention, we aimed to investigate OSA's impact on CSVD imaging measures and explore whether aspirin effects these measures over 3 years that differ in the presence or absence of OSA.

METHODS

A substudy of the aspirin in reducing events in the elderly (ASPREE) randomized placebo-controlled trial of low-dose aspirin. Community-dwelling participants aged 70 years and above, without cognitive impairment, cardiovascular disease, or known OSA completed an unattended limited-channel sleep study that calculated the oxygen desaturation index and apnea-hypopnea index. At baseline and 3 years later, volumes of white matter hyperintensities (WMH) and silent brain infarctions (SBI) were measured on 1.5 Tesla brain magnetic resonance imaging, and retinal vessel calibers were calculated from retinal vascular imaging.

RESULTS

Mild and moderate/severe OSA was detected in 48.9% and 29.9%, respectively, of the 311 participants, who had a mean age of 73.7 years (SD 3.4 years), 38.6% female. OSA of any severity was not associated with WMH volumes, SBI, nor retinal vessel calibers at baseline, nor with change in these measures in the 277 participants with repeated measures acquired after 3 years. OSA of any severity did not interact with aspirin on change in these measures over 3 years.

CONCLUSIONS

In healthy older adults undiagnosed OSA was not associated with retinal vascular calibers and neuroimaging measures of CSVD.

CLINICAL TRIAL INFORMATION

ASPREE trial has registration with the International Standard Randomized Controlled Trial Number (ISRCTN) www.isrctn.com, ISRCTN83772183 and with www.clinicaltrials.gov, NCT01038583. SNORE-ASA has registration with the Australian New Zealand Clinical Trials Registry (ANZCTR) at www.anzctr.org.au, ACTRN12612000891820.

The effect of sleep disturbances on the incidence of dementia for varying lag times

BACKGROUND

Few studies have addressed the association of sleep disturbances with incident dementia with long lag times. We add to this literature by investigating how lag times varying from 2.2 to 23.8 years affect the relationship between sleep disturbance and incident dementia in a Dutch cohort study on aging.

METHODS

Using eight waves of data from the Longitudinal Aging Study Amsterdam, we investigated the association of hours of sleep, difficulty falling asleep, interrupted sleep, and waking up early with incident dementia. For dementia an algorithm was used based on repeated measurements of cognitive tests and other data sources that provide strong indications of dementia. Sleep disturbances were assessed with a self-report questionnaire.

RESULTS

Of 2,218 participants, 237 (11%) developed dementia in the period 1992/3 to 2015/6. Participants ≥70 years more often reported sleep disturbances compared to those <70. Only for a short lag time (3 years), sleeping ≥9 h was associated with incident dementia. Sleeping ≤6 h, interrupted sleep and waking up early were associated with incident dementia, particularly for lag times ≥15 years.

DISCUSSION

We found that the association of sleep disturbances with incident dementia becomes stronger with longer lag times (particularly ≥15 years). Studies with lag times <15 years may suffer from reverse causation due to the changes in sleep patterns caused by the prodromal phase of neurodegenerative disease. The association of sleeping ≥9 h and the incidence of dementia in analyses with a short lag time seem to be the result of reverse causation.

Snoring and risk of dementia: a prospective cohort and Mendelian randomization study

STUDY OBJECTIVES

The association between snoring, a very common condition that increases with age, and dementia risk is controversial. We aimed to investigate the observational and causal relationship between snoring and dementia, and to elucidate the role of body mass index (BMI).

METHODS

Using data from 451 250 participants who were dementia-free at baseline, we examined the association between self-reported snoring and incident dementia using Cox proportional-hazards models. Causal relationship between snoring and Alzheimer's disease (AD) was examined using bidirectional two-sample Mendelian randomization (MR) analysis.

RESULTS

During a median follow-up of 13.6 years, 8325 individuals developed dementia. Snoring was associated with a lower risk of all-cause dementia (hazard ratio [HR] 0.93; 95% confidence interval [CI] 0.89 to 0.98) and AD (HR 0.91; 95% CI 0.84 to 0.97). The association was slightly attenuated after adjusting for BMI, and was stronger in older individuals, APOE ε4 allele carriers, and during shorter follow-up periods. MR analyses suggested no causal effect of snoring on AD; however, genetic liability to AD was associated with a lower risk of snoring. Multivariable MR indicated that the effect of AD on snoring was primarily driven by BMI.

CONCLUSIONS

The phenotypic association between snoring and lower dementia risk likely stems from reverse causation, with genetic predisposition to AD associated with reduced snoring. This may be driven by weight loss in prodromal AD. Increased attention should be paid to reduced snoring and weight loss in older adults as potential early indicators of dementia risk.

Plasma metabolomic signature of healthy lifestyle, structural brain reserve and risk of dementia

Although the association between healthy lifestyle and dementia risk has been documented, the relationship between a metabolic signature indicative of healthy lifestyle and dementia risk and the mediating role of structural brain impairment remain unknown. We retrieved 136 628 dementia-free participants from UK Biobank. Elastic net regression was used to obtain a metabolic signature that represented lifestyle behaviours. Cox proportional hazard models were fitted to explore the associations of lifestyle-associated metabolic signature with incident dementia. Causal associations between identified metabolites and dementia were investigated using Mendelian randomization. Mediation analysis was also conducted to uncover the potential mechanisms involving 19 imaging-derived phenotypes (brain volume, grey matter volume, white matter volume and regional grey matter volumes). During a follow-up of 12.55 years, 1783 incident cases of all-cause dementia were identified, including 725 cases of Alzheimer's dementia and 418 cases of vascular dementia. We identified 83 metabolites that could represent healthy lifestyle behaviours using elastic net regression. The metabolic signature was associated with a lower dementia risk, and for each standard deviation increment in metabolic signature, the hazard ratio was 0.89 [95% confidence interval (CI): 0.85, 0.93] for all-cause dementia, 0.95 (95% CI: 0.88, 1.03) for Alzheimer's dementia and 0.84 (95% CI: 0.77, 0.91) for vascular dementia. Mendelian randomization revealed potential causal associations between the identified metabolites and risk of dementia. In addition, the specific structural brain reserve, including the hippocampus, grey matter in the hippocampus, parahippocampal gyrus and middle temporal gyrus, were detected to mediate the effects of metabolic signature on dementia risk (mediated proportion ranging from 6.21% to 11.98%). The metabolic signature associated with a healthy lifestyle is inversely associated with dementia risk, and greater structural brain reserve plays an important role in mediating this relationship. These findings have significant implications for understanding the intricate connections between lifestyle, metabolism and brain health.

Sleep apnoea, cognition and aspirin's effects in healthy older people: an ASPREE substudy

Importance

Obstructive sleep apnoea (OSA) may increase the risk of dementia; however, studies have reported variable findings. We investigated if undiagnosed OSA in healthy older adults is associated with cognitive decline, and whether low-dose aspirin could attenuate this.

Methods

This was conducted as a substudy of the ASPirin in Reducing Events in the Elderly study. Participants were aged 70 years and above, free of dementia, cardiovascular disease and known OSA. A limited channel home sleep study calculated the oxygen desaturation index. Participants were randomised to daily aspirin 100 mg or placebo. Outcomes were the association of OSA, and the interaction of aspirin with OSA, with change in the Modified Mini-Mental State examination (3MS), a test of global cognition, over 3 years. Secondary outcomes were changes in domain-specific cognitive tests. Analyses were adjusted for relevant demographic, lifestyle and cardiometabolic factors.

Results

Mild OSA, detected in 630 (49.0%) participants, and moderate/severe OSA, detected in 405 (31.5%) participants, were associated with lower 3MS scores over 3 years (mild OSA: β -0.58, 95% CI -1.15 to -0.00, p=0.049; moderate/severe OSA: β -0.69, 95% CI -1.32 to -0.05, p=0.035), compared to the 250 (19.5%) participants without OSA. No associations of OSA with decline in domain-specific cognitive tests were observed. Interaction terms were not significant for the effects of aspirin with OSA on change in any cognitive test score.

Conclusions

OSA was associated with a small decline in global cognition over 3 years in this healthy older cohort. This decline was not attenuated by aspirin.

Exosomes from IH- Induced bEnd3 Cells Promote OSA Cognitive Impairment via miR-20a-5p/MFN2 Mediated Pyroptosis of HT22 Cells

Background

OSA can cause cognitive impairment (CI). The aim of this study was to investigate whether miR-20a-5p in exosomes derived from bEnd3 cells with IH mediates intercellular crosstalk and induces CI through hippocampal neuronal cell pyroptosis.

Materials and Methods

BEnd3-derived exosomes were isolated from the normal oxygen control group (NC-EXOS) and IH group (IH-EXOS). In vitro, exosomes were cocultured with HT22 cells. Meanwhile, in vivo, exosomes were injected into mice via the caudal vein. The spatial memory ability of mice was tested by MWM method to evaluate the effect of exosomes on the cognitive function of mice. Adults diagnosed with OSA underwent the MoCA and ESS tests to assess cognitive function and daytime sleepiness. Spearman's rank correlation analysis was used to evaluate the correlation between miR-20a-5p and candidate proteins and clinical parameters. Transfection using small interfering RNAs, miRNA mimics, and plasmids to evaluate the role of miR-20a-5p and its target genes. Dual luciferase reporter gene assay was used to confirm the binding of miR-20a-5p to its target gene.

Results

IH could cause pyroptosis and inflammation in bEnd3 cells, and promote the expression of miR-20a-5p. Isolated IH-EXOS induced increased pyroptosis and activation of inflammatory response in vitro and in vivo, accompanied by increased expression of miR-20a-5p. In addition, IH-EXOS led to decreased learning and memory ability in mice. Interestingly, AHI was higher and MoCA scores were lower in severe OSA compared to healthy comparisons. In addition, miR-20a-5p and GSDMD were positively correlated with AHI but negatively correlated with MoCA in severe OSA. IH-induced exosomes were rich in miR-20a-5p, and these exosomes were found to deliver miR-20a-5p to HT22 cells, playing a key role in the induction of OSA-CI by directly targeting MFN2.

Conclusion

Exosome miR-20a-5p from IH-stimulated bEnd3 cells can promote OSA-CI by increasing HT22 cells pyroptosis through its target MFN2.

The Effect of Sleep Duration and Excessive Daytime Sleepiness on All-Cause Dementia: A Longitudinal Analysis from the Hunter Community Study

OBJECTIVES

It has been proposed that abnormal sleep duration and excessive daytime sleepiness might be risk factors for dementia. This study assessed the interaction between sleep duration and excessive daytime sleepiness, and the effect of sleep duration in the presence or absence of excessive daytime sleepiness on dementia risk in community-dwelling older adults.

DESIGN

A longitudinal study.

SETTING AND PARTICIPANTS

Data from 2187 community-dwelling participants with mean age 70 years from the Hunter Community Study were included in this study.

METHODS

Participants were classified as participants with long sleep duration (slept >8 hours per night), recommended sleep duration (7-8 hours) as per the National Sleep Foundation, or short sleep duration (slept <7 hours per night). The Berlin Questionnaire was used to identify excessive daytime sleepiness. Dementia was defined as per International Classification of Diseases, 10th Revision codes. To calculate all-cause dementia risk, the Fine-Gray sub-distribution hazard model was computed with death as a competing risk.

RESULTS

Over a mean follow-up of 6 years, 64 participants developed dementia and 154 deaths were identified. The average onset of dementia was 5.4 years. Long sleep duration was associated with increased dementia risk only in the presence of excessive daytime sleepiness (adjusted hazard ratio, 2.86; 95% confidence interval 1.03-7.91). A statistically significant interaction was found between excessive daytime sleepiness and sleep duration for all-cause dementia.

CONCLUSIONS AND IMPLICATIONS

Long sleep duration with excessive daytime sleepiness was associated with increased risk of all-cause dementia. This suggests the importance of promoting awareness of healthy sleep and the possible role of nurturing good quantity and quality sleep in reducing the risk of dementia.

The effects of sleep duration on the risk of dementia incidence in short and long follow-up studies: A systematic review and meta-analysis

Sleep duration's association with future dementia could be a cause or consequence, or both. We searched electronic databases on 14th April 2023 for primary peer-reviewed, longitudinal studies examining the relationship between sleep duration and dementia with any follow-up duration. We meta-analysed studies examining brief (≤6 h/night) and extended sleep duration (≥9 h/night) separately and divided the studies into those with follow-up periods of less or more than 10 years. The quality of evidence was assessed using the Newcastle-Ottawa scale. 31 studies fulfilled the inclusion criteria. For brief sleep duration, a meta-analysis of short follow-up studies (≤10 years) found a 46 % increased risk of future dementia (relative risk [RR] - 1·46; 95 % Confidence Intervals [CIs] 1·48-1·77; I2 = 88·92 %, 6 studies). Studies with long follow-ups (>10 years) did not show a significantly increased risk (RR - 1·12; 0·95-1·29; I2 = 65·91 %; 5 studies). For extended sleep duration, a meta-analysis of short and long follow-up studies reported an increased risk of dementia (respectively RR - 2·20; 1·11-3·3; I2 = 94·17 %; 4 studies and RR - 1·74; 1·30-2·18; I2 = 86·56 %; 4 studies). Our findings suggest that brief sleep duration might be a prodromal symptom but not a risk factor of dementia. Extended sleep duration may be a risk factor. However, our results had high heterogeneity limiting external validity and generalisability.

Examining mental health and autonomic function as putative mediators of the relationship between sleep and trajectories of cognitive function: findings from the Irish longitudinal study on ageing (TILDA)

OBJECTIVES

This study investigates the mediating roles of autonomic function and mental health in the association between sleep and cognitive decline in adults aged 50 and above.

METHOD

A total of 2,697 participants with observations on sleep and mediators at baseline and repeated measures of cognitive function (MMSE) were included. Clusters of individuals with similar cognitive trajectories (high-stable, mid-stable and low-declining) were identified. Multinomial logistic regressions were used to estimate the likelihood of membership to each trajectory group based on sleep duration and disturbance. Finally, mediation analysis tested potential mediating effects of autonomic function and mental health underpinning the sleep-cognition relationship.

RESULTS

Short (p = .028), long (p =.019), and disturbed sleep (p =.008) increased the likelihood of a low-declining cognitive trajectory. Mental health measures fully attenuated relationships between cognitive decline and short or disturbed sleep but not long sleep. No autonomic function mediation was observed.

CONCLUSION

Older adults with short or disturbed sleep are at risk of cognitive decline due to poor mental health. Individuals with long sleep are also at risk, however, the acting pathways remain to be identified. These outcomes have clinical implications, potentially identifying intervention strategies targeting mental health and sleep as prophylactic measures against dementia.

Dementia: Common Syndromes and Modifiable Risk and Protective Factors

Dementia is an umbrella term for multiple conditions that lead to progressive cognitive decline and impaired activities of daily living. Neuropsychological evaluation is essential for characterizing the distinct cognitive and behavioral profile that can aid in the diagnostic process and treatment planning for dementia. Modifiable risk factors for dementia such as nutrition, physical activity, sleep, cognitive and social engagement, and stress provide important avenues for prevention. Neurologists and other health care providers can help patients reduce their risk for dementia by providing them with education about modifiable factors and connecting them to resources to empower them to engage in brain-healthy behavior.

Causal Associations of Sleep Apnea With Alzheimer Disease and Cardiovascular Disease: A Bidirectional Mendelian Randomization Analysis

BACKGROUND

Sleep apnea (SA) has been linked to an increased risk of dementia in numerous observational studies; whether this is driven by neurodegenerative, vascular, or other mechanisms is not clear. We sought to examine the bidirectional causal relationships between SA, Alzheimer disease (AD), coronary artery disease (CAD), and ischemic stroke using Mendelian randomization.

METHODS AND RESULTS

Using summary statistics from 4 recent, large genome-wide association studies of SA (n=523 366), AD (n=94 437), CAD (n=1 165 690), and stroke (n=1 308 460), we conducted bidirectional 2-sample Mendelian randomization analyses. Our primary analytic method was fixed-effects inverse variance-weighted (IVW) Mendelian randomization; diagnostics tests and sensitivity analyses were conducted to verify the robustness of the results. We identified a significant causal effect of SA on the risk of CAD (odds ratio [ORIVW]=1.35 per log-odds increase in SA liability [95% CI=1.25-1.47]) and stroke (ORIVW=1.13 [95% CI=1.01-1.25]). These associations were somewhat attenuated after excluding single-nucleotide polymorphisms associated with body mass index (ORIVW=1.26 [95% CI=1.15-1.39] for CAD risk; ORIVW=1.08 [95% CI=0.96-1.22] for stroke risk). SA was not causally associated with a higher risk of AD (ORIVW=1.14 [95% CI=0.91-1.43]). We did not find causal effects of AD, CAD, or stroke on risk of SA.

CONCLUSIONS

These results suggest that SA increased the risk of CAD, and the identified causal association with stroke risk may be confounded by body mass index. Moreover, no causal effect of SA on AD risk was found. Future studies are warranted to investigate cardiovascular pathways between sleep disorders, including SA, and dementia.

Multidimensional Sleep Profiles via Machine learning and Risk of Dementia and Cardiovascular Disease

Importance

Sleep health comprises several dimensions such as duration and fragmentation of sleep, circadian activity, and daytime behavior. Yet, most research has focused on individual sleep characteristics. Studies are needed to identify sleep profiles incorporating multiple dimensions and to assess how different profiles may be linked to adverse health outcomes.

Objective

To identify actigraphy-based 24-hour sleep/circadian profiles in older men and to investigate whether these profiles are associated with the incidence of dementia and cardiovascular disease (CVD) events over 12 years.

Design

Data came from a prospective sleep study with participants recruited between 20032005 and followed until 2015-2016.

Setting

Multicenter population-based cohort study.

Participants

Among the 3,135 men enrolled, we excluded 331 men with missing or invalid actigraphy data and 137 with significant cognitive impairment at baseline, leading to a sample of 2,667 participants.

Exposures

Leveraging 20 actigraphy-derived sleep and circadian activity rhythm variables, we determined sleep/circadian profiles using an unsupervised machine learning technique based on multiple coalesced generalized hyperbolic mixture modeling.

Main Outcomes and Measures

Incidence of dementia and CVD events.

Results

We identified three distinct sleep/circadian profiles: active healthy sleepers (AHS; n=1,707 (64.0%); characterized by normal sleep duration, higher sleep quality, stronger circadian rhythmicity, and higher activity during wake periods), fragmented poor sleepers (FPS; n=376 (14.1%); lower sleep quality, higher sleep fragmentation, shorter sleep duration, and weaker circadian rhythmicity), and long and frequent nappers (LFN; n=584 (21.9%); longer and more frequent naps, higher sleep quality, normal sleep duration, and more fragmented circadian rhythmicity). Over the 12-year follow-up, compared to AHS, FPS had increased risks of dementia and CVD events (Hazard Ratio (HR)=1.35, 95% confidence interval (CI)=1.02-1.78 and HR=1.32, 95% CI=1.08-1.60, respectively) after multivariable adjustment, whereas LFN showed a marginal association with increased CVD events risk (HR=1.16, 95% CI=0.98-1.37) but not with dementia (HR=1.09, 95%CI=0.86-1.38).

Conclusion and Relevance

We identified three distinct multidimensional profiles of sleep health. Compared to healthy sleepers, older men with overall poor sleep and circadian activity rhythms exhibited worse incident cognitive and cardiovascular health. These results highlight potential targets for sleep interventions and the need for more comprehensive screening of poor sleepers for adverse outcomes.

Causal relationship between sleep disorders and the risk of Alzheimer's disease: A Mendelian randomization study

BACKGROUND AND OBJECTIVE

Epidemiological studies have shown that sleep disorders are risk factors for Alzheimer's disease (AD), but the causal relationship between sleep disorders and AD risk is unknown. We aim to assess the potential genetic causal association between sleep characteristics and AD, which may contribute to early identification and prediction of risk factors for AD.

METHODS

Seven sleep-related traits and the outcome phenotype AD were selected from published genome-wide association studies (GWASs). These sleep-related characteristics and instrumental variables (IVs) for AD were extracted. Two-sample and multivariate Mendelian randomization (MR) analyses were performed to assess the causal relationships between sleep characteristics and AD. The inverse variance weighted (IVW), weighted median (WME), weighted mode (WM), MR-Egger regression (MR-Egger) and simple mode (SM) models were used to evaluate causality. The existence of pleiotropy was detected and corrected by MR-Egger regression, MR pleiotropy residuals and outliers.

RESULTS

A two-sample MR study revealed a positive causal association between sleep duration and the onset of AD (OR = 1.002, 95 % CI: 1.000-1.004), and the risk of AD increased with increasing sleep duration. The MR-Egger regression method and MR-PRESSO were used to identify and correct pleiotropy, indicating that there was no horizontal pleiotropy. Heterogeneity was evaluated by Cochran's Q, which indicated no heterogeneity. In a multivariate MR study with seven sleep characteristics corrected for each other, we found that sleep duration remained causally associated with AD (OR = 1.004, 95 % CI: 1.000-1.007). Moreover, we found that after mutual correction, daytime napping had a causal relationship with the onset of AD, and daytime napping may reduce the risk of AD (OR = 0.995, 95 % CI: 0.991-1.000).

CONCLUSION

This study is helpful for the early identification and prediction of risk factors for AD, long sleep durations are a risk factor for AD, and daytime napping can reduce the risk of AD.

Associations of psychosocial factors and cardiovascular health measured by Life's Essential 8: The Atherosclerosis Risk in Communities (ARIC) study

AIMS

Few studies investigate whether psychosocial factors (social isolation, social support, trait anger, and depressive symptoms) are associated with cardiovascular health, and none with the American Heart Association's new definition of cardiovascular health, Life's Essential 8 (LE8). Therefore, we assessed the cross-sectional associations of psychosocial factors with Life's Essential 8 and individual components of Life's Essential 8.

METHODS

We included 11,311 Atherosclerosis Risk in Communities cohort participants (58% females; 23% Black; mean age 57 (standard deviation: 6) years) who attended Visit 2 (1990-1992) in this secondary data analysis using cross-sectional data from the ARIC cohort study. Life's Essential 8 components included diet, physical activity, nicotine exposure, sleep quality, body mass index, blood lipids, blood glucose, and blood pressure. Life's Essential 8 was scored per the American Heart Association definition (0-100 range); higher scores indicate better cardiovascular health. Associations of categories (high, moderate, and low) of each psychosocial factor with continuous Life's Essential 8 score and individual Life's Essential 8 components were assessed using multivariable linear regressions.

RESULTS

11% of participants had high Life's Essential 8 scores (80-100), while 67% and 22% had moderate (50-79) and low Life's Essential 8 scores (0-49) respectively. Poor scores on psychosocial factor assessments were associated with lower Life's Essential 8 scores, with the largest magnitude of association for categories of depressive symptoms (low β = Ref.; moderate β = -3.1, (95% confidence interval: -3.7, -2.5; high β = -8.2 (95% confidence interval: -8.8, -7.5)). Most psychosocial factors were associated with Life's Essential 8 scores for diet, physical activity, nicotine, and sleep, but psychosocial factors were not associated with body mass index, blood lipids, blood glucose, or blood pressure.

CONCLUSION

Less favorable measures of psychosocial health were associated with lower Life's Essential 8 scores compared better measures of psychosocial health among middle-aged males and females.

Sleep characteristics and risk of Alzheimer's disease: a systematic review and meta-analysis of longitudinal studies

BACKGROUND

Alzheimer's disease (AD) is on the rise in our aging society, making it crucial to identify additional risk factors to mitigate its increasing incidence. This systematic review and meta-analysis aimed to provide updated evidence regarding the association between sleep and AD.

METHODS

We conducted a comprehensive search of MEDLINE, EMBASE, and Web of Science databases from inception to July 2023 to identify longitudinal studies. Adjusted relative risks were pooled for each sleep characteristic, and a dose-response analysis was performed specifically for sleep duration.

RESULTS

A total of 15,278 records were initially retrieved, and after screening, 35 records were ultimately included in the final analysis. The results showed that insomnia (RR, 1.43; 95%CI, 1.17-1.74), sleep-disordered breathing (RR, 1.22; 95%CI, 1.07-1.39), as well as other sleep problems, including sleep fragmentation and sleep-related movement disorders, were associated with a higher risk of developing AD, while daytime napping or excessive daytime sleepiness (RR, 1.18; 95%CI, 1.00-1.40) only exhibited a trend toward a higher risk of AD development. Furthermore, our analysis revealed a significant association between self-reported sleep problems (RR, 1.34; 95%CI, 1.26-1.42) and the incidence of AD, whereas this association was not observed with sleep problems detected by objective measurements (RR, 1.14; 95%CI, 0.99-1.31). Moreover, both quite short sleep duration (< 4 h) and long duration (> 8 h) were identified as potential risk factors for AD.

CONCLUSIONS

Our study found the association between various types of sleep problems and an increased risk of AD development. However, these findings should be further validated through additional objective device-based assessments. Additional investigation is required to establish a definitive causal connection between sleep problems and AD.

Shorter sleep duration and lesser sleep efficiency are associated with poorer memory functions among non-demented, middle-aged, and older rural Indians

Introduction

Sleep is known to be involved in cognitive processes, such as memory encoding and consolidation, and poor sleep is a potential risk factor for dementia. This study aims to investigate the effect of sleep quality on memory functions among middle-aged and older adults from a rural Indian population.

Methods

Participants were non-demented, rural Indians (≥45 years) from an ongoing, prospective, aging cohort study, namely Srinivaspura Aging, NeuroSenescence, and COGnition (SANSCOG) study. Cross-sectional (baseline) data on seven sleep dimensions was obtained using the Pittsburgh Sleep Quality Index (PSQI). Memory functions were assessed using immediate recall, delayed recall, name-face association, and semantic association from a culturally validated, computerized, neurocognitive test battery. Linear regression models, unadjusted and adjusted for cognitive status, age, sex, and depression were used to analyze the association between each sleep dimension and the memory tests.

Results

A total of 1195 participants, with a mean age of 57.10 years, were included. Out of the seven sleep dimensions of the PSQI, only two dimensions, namely sleep duration and sleep efficiency, were significantly associated with memory functions. In the fully adjusted model, shorter sleep duration was significantly associated with poorer performance in delayed recall, and lesser sleep efficiency was significantly associated with poorer delayed recall and semantic association performance.

Conclusions

Specific sleep characteristics appear to influence memory functions in aging Indians well before the onset of dementia. In the backdrop of the non-availability of a definitive treatment for dementia, promptly identifying and addressing these problems could be an effective, community-level strategy for preventing dementia.

Association between sleep apnoea and risk of cognitive impairment and Alzheimer's disease: a meta-analysis of cohort-based studies

PURPOSE

To provide updated evidence on the association of obstructive sleep apnoea (OSA)/sleep-disordered breathing (SDB) with risk of all-cause cognitive impairment/dementia and Alzheimer's disease (AD).

METHODS

A systematic literature search was done in PubMed, EMBASE and Scopus databases for cohort studies (retrospective or prospective) that documented the association of SDB/OSA with the risk of cognitive impairment or all-cause dementia or AD. Only studies that were published in the year 2000 and onwards were included. The random-effects model was used for all the analyses and effect sizes were reported as hazards ratio (HR) with 95% confidence intervals.

RESULTS

Of 15 studies were included in the meta-analysis, SDB/OSA was diagnosed with at-home polysomnography in six studies, while five studies relied on self-report or questionnaires. In the remaining studies, International Classification of Diseases (ICD) codes determined the diagnosis of SDB. The overall pooled analysis showed that patients with SDB/OSA had higher risk of cognitive impairment and/or all-cause dementia (HR 1.52, 95% CI: 1.32, 1.74), when compared to patients without SDB/OSA. However, when studies with diagnosis of SDB based on polysomnography were pooled together, the strength of association for all-cause cognitive impairment was weaker (HR 1.32, 95% CI: 1.00, 1.74).

CONCLUSION

Findings suggest a possible association of SDB/OSA with risk of all-cause cognitive impairment and/or dementia. However, careful interpretation is warranted as the majority of the studies did not rely on objective assessment based on polysomnography.

Clinical Outcomes and Tau Pathology in Retired Football Players: Associations With Diagnosed and Witnessed Sleep Apnea

Background and Objectives

Obstructive sleep apnea (SA) is common in older men and a contributor to negative cognitive, psychiatric, and brain health outcomes. Little is known about SA in those who played contact sports and are at increased risk of neurodegenerative disease(s) and other neuropathologies associated with repetitive head impacts (RHI). In this study, we investigated the frequency of diagnosed and witnessed SA and its contribution to clinical symptoms and tau pathology using PET imaging among male former college and former professional American football players.

Methods

The sample included 120 former National Football League (NFL) players, 60 former college players, and 60 asymptomatic men without exposure to RHI (i.e., controls). Diagnosed SA was self-reported, and all participants completed the Mayo Sleep Questionnaire (MSQ, informant version), the Epworth Sleepiness Scale (ESS), neuropsychological testing, and tau (flortaucipir) PET imaging. Associations between sleep indices (diagnosed SA, MSQ items, and the ESS) and derived neuropsychological factor scores, self-reported depression (Beck Depression Inventory-II [BDI-II]), informant-reported neurobehavioral dysregulation (Behavior Rating Inventory of Executive Function-Adult Version [BRIEF-A] Behavioral Regulation Index [BRI]), and tau PET uptake, were tested.

Results

Approximately 36.7% of NFL players had diagnosed SA compared with 30% of the former college football players and 16.7% of the controls. Former NFL players and college football players also had higher ESS scores compared with the controls. Years of football play was not associated with any of the sleep metrics. Among the former NFL players, diagnosed SA was associated with worse Executive Function and Psychomotor Speed factor scores, greater BDI-II scores, and higher flortaucipir PET standard uptake value ratios, independent of age, race, body mass index, and APOE ε4 gene carrier status. Higher ESS scores correlated with higher BDI-II and BRIEF-A BRI scores. Continuous positive airway pressure use mitigated all of the abovementioned associations. Among the former college football players, witnessed apnea and higher ESS scores were associated with higher BRIEF-A BRI and BDI-II scores, respectively. No other associations were observed in this subgroup.

Discussion

Former elite American football players are at risk of SA. Our findings suggest that SA might contribute to cognitive, neuropsychiatric, and tau outcomes in this population. Like all neurodegenerative diseases, this study emphasizes the multifactorial contributions to negative brain health outcomes and the importance of sleep for optimal brain health.

Sleep duration, its change, and risk of dementia among Japanese: The Japan Public Health Center-based Prospective Study

OBJECTIVE

Previous findings on the association between sleep duration, changes in sleep duration, and long-term dementia risk were mixed. Thus, we aimed to investigate the association between midlife sleep duration, its change, and dementia.

METHODS

We recruited 41,731 Japanese (40-71 years) and documented their habitual sleep duration at baseline (1990-1994) and a 5-year follow-up survey. Changes in sleep duration were calculated as differences between baseline and 5-year measurements. We identified dementia using the Long-Term Care Insurance system (2007-2016). Hazard ratios (HRs) and 95% confidence intervals (CIs) of dementia were calculated using the area-stratified Cox model.

RESULTS

During 360,389 person-years, 4621 participants exhibited dementia. The multivariable HRs of dementia compared with 7 h of sleep were 1.13 (95% CI: 0.98-1.30) for 3-5 h, 0.93 (0.85-1.02) for 6 h, 1.06 (0.99-1.14) for 8 h, 1.13 (1.01-1.27) for 9 h, and 1.40 (1.21-1.63) for 10-12 h with a J-shaped fashion (p for linear < 0.001 and quadratic < 0.001). For its change, the HRs compared with no change were 1.02 (0.90-1.16) for decreased ≥2 h, 0.95 (0.88-1.03) for decreased 1 h, 1.00 (0.91-1.09) for increased 1 h, and 1.37 (1.20-1.58) for increased ≥2 h. The positive association for decreased sleep duration was observed in individuals with an initial sleep duration of ≤7 h, but not in those with ≥8 h (p for interaction = 0.007).

CONCLUSIONS

Long and increased sleep duration was associated with a higher risk of dementia.

Impact of Sleep Disorders and Disturbed Sleep on Brain Health: A Scientific Statement From the American Heart Association

Accumulating evidence supports a link between sleep disorders, disturbed sleep, and adverse brain health, ranging from stroke to subclinical cerebrovascular disease to cognitive outcomes, including the development of Alzheimer disease and Alzheimer disease-related dementias. Sleep disorders such as sleep-disordered breathing (eg, obstructive sleep apnea), and other sleep disturbances, as well, some of which are also considered sleep disorders (eg, insomnia, sleep fragmentation, circadian rhythm disorders, and extreme sleep duration), have been associated with adverse brain health. Understanding the causal role of sleep disorders and disturbances in the development of adverse brain health is complicated by the common development of sleep disorders among individuals with neurodegenerative disease. In addition to the role of sleep disorders in stroke and cerebrovascular injury, mechanistic hypotheses linking sleep with brain health and biomarker data (blood-based, cerebrospinal fluid-based, and imaging) suggest direct links to Alzheimer disease-specific pathology. These potential mechanisms and the increasing understanding of the "glymphatic system," and the recognition of the importance of sleep in poststroke recovery, as well, support a biological basis for the indirect (through the worsening of vascular disease) and direct (through specific effects on neuropathology) connections between sleep disorders and brain health. Given promising evidence for the benefits of treatment and prevention, sleep disorders and disturbances represent potential targets for early treatment that may improve brain health more broadly. In this scientific statement, we discuss the evidence supporting an association between sleep disorders and disturbances and poor brain health ranging from stroke to dementia and opportunities for prevention and early treatment.

Associations of sleep duration and daytime sleepiness with plasma amyloid beta and cognitive performance in cognitively unimpaired, middle-aged and older African Americans

STUDY OBJECTIVES

Given the established racial disparities in both sleep health and dementia risk for African American populations, we assess cross-sectional and longitudinal associations of self-report sleep duration (SRSD) and daytime sleepiness with plasma amyloid beta (Aβ) and cognition in an African American (AA) cohort.

METHODS

In a cognitively unimpaired sample drawn from the African Americans Fighting Alzheimer's in Midlife (AA-FAiM) study, data on SRSD, Epworth Sleepiness Scale, demographics, and cognitive performance were analyzed. Aβ40, Aβ42, and the Aβ42/40 ratio were quantified from plasma samples. Cross-sectional analyses explored associations between baseline predictors and outcome measures. Linear mixed-effect regression models estimated associations of SRSD and daytime sleepiness with plasma Aβ and cognitive performance levels and change over time.

RESULTS

One hundred and forty-seven participants comprised the cross-sectional sample. Baseline age was 63.2 ± 8.51 years. 69.6% self-identified as female. SRSD was 6.4 ± 1.1 hours and 22.4% reported excessive daytime sleepiness. The longitudinal dataset included 57 participants. In fully adjusted models, neither SRSD nor daytime sleepiness is associated with cross-sectional or longitudinal Aβ. Associations with level and trajectory of cognitive test performance varied by measure of sleep health.

CONCLUSIONS

SRSD was below National Sleep Foundation recommendations and daytime sleepiness was prevalent in this cohort. In the absence of observed associations with plasma Aβ, poorer self-reported sleep health broadly predicted poorer cognitive function but not accelerated decline. Future research is necessary to understand and address modifiable sleep mechanisms as they relate to cognitive aging in AA at disproportionate risk for dementia.

CLINICAL TRIAL INFORMATION

Not applicable.

Gender-and age-specific associations of sleep duration and quality with cognitive impairment in community-dwelling older adults in Anhui Province, China

Objective

To examine associations of sleep duration and quality with cognitive impairment in older adults and the moderating role of gender and age in these associations.

Methods

This community-based cross-sectional study included 4,837 participants aged 60 years and above. Cognitive function was assessed using the Chinese version of the Mini-Mental State Examination (MMSE), and the participants were grouped based on the presence of cognitive impairment. The duration and quality of sleep were assessed using the Pittsburgh Sleep Quality Index (PSQI). Multivariate logistic regression models were used to analyze associations of sleep duration and quality with cognitive impairment. The role of age and gender in these associations have also been explored.

Results

The age (mean ± SD) of the participants was 71.13 ± 5.50 years. Of all older adults, 1,811 (37.44%) were detected as cognitive impairment, and 1755 (36.8%) had poor sleep quality. Among those with cognitive impairment, 51.09% were female. The proportion of the participants with cognitive impairment is significantly higher in those with symptoms of depression (49.73%, 273/549) (χ2 = 41.275, p < 0.001) than in those without depressive symptoms. After adjustment for multiple confounding factors and the crucial covariate (depressive symptoms), the odds ratios (OR) (95% confidence interval [CI]) of cognitive impairment (with 7-7.9 h regarded as the reference group) for individuals with a sleep duration of <6, 6-6.9, 8-8.9, and ≥ 9 h were 1.280 (1.053-1.557), 1.425 (1.175-1.728), 1.294 (1.068-1.566), and 1.360 (1.109-1.668), respectively. Subgroup analysis showed a V-shaped association between night sleep duration and cognitive impairment in males (p ≤ 0.05), and the association was stronger for individuals aged 60-80 years. With regard to sleep quality, the fully adjusted OR (95%CI) of cognitive impairment were 1.263 (1.108-1.440). According to scores of subscales in the PSQI, daytime dysfunction was associated with an increased risk of cognitive impairment (OR: 1.128, 95%CI: 1.055-1.207). Subgroup analysis also revealed a statistically significant correlation between poor sleep quality (including daytime dysfunction) and cognitive impairment in different gender and age groups, with the association being stronger in females (OR: 1.287, 95%CI: 1.080-1.534) and those aged 81-97 years (OR: 2.128, 95%CI: 1.152-3.934). For cognitive impairment, the group aged 81-97 years with daytime dysfunction was associated with a higher odds ratio than other age groups.

Conclusion

The present study showed that inadequate or excessive sleep was associated with cognitive impairment, especially in males, who exhibited a V-shaped association. Cognitive impairment was also associated with poor sleep quality as well as daytime dysfunction, with females and individuals aged 81-97 years exhibiting the strongest association.

Sleep Biomarkers for Predicting Cognitive Decline and Alzheimer's Disease: A Systematic Review of Longitudinal Studies

BACKGROUND

Sleep disturbances are considered a hallmark of dementia, and strong evidence supports the association between alterations in sleep parameters and cognitive decline in patients with mild cognitive impairment and Alzheimer's disease (AD).

OBJECTIVE

This systematic review aims to summarize the existing evidence on the longitudinal association between sleep parameters and cognitive decline, with the goal of identifying potential sleep biomarkers of AD-related neurodegeneration.

METHODS

Literature search was conducted in PubMed, Web of Science, and Scopus databases from inception to 28 March 2023. Longitudinal studies investigating the association between baseline objectively-measured sleep parameters and cognitive decline were assessed for eligibility.

RESULTS

Seventeen studies were included in the qualitative synthesis. Sleep fragmentation, reduced sleep efficiency, reduced REM sleep, increased light sleep, and sleep-disordered breathing were identified as predictors of cognitive decline. Sleep duration exhibited a U-shaped relation with subsequent neurodegeneration. Additionally, several sleep microstructural parameters were associated with cognitive decline, although inconsistencies were observed across studies.

CONCLUSIONS

These findings suggest that sleep alterations hold promise as early biomarker of cognitive decline, but the current evidence is limited due to substantial methodological heterogeneity among studies. Further research is necessary to identify the most reliable sleep parameters for predicting cognitive impairment and AD, and to investigate interventions targeting sleep that can assist clinicians in the early recognition and treatment of cognitive decline. Standardized procedures for longitudinal studies evaluating sleep and cognition should be developed and the use of continuous sleep monitoring techniques, such as actigraphy or EEG headband, might be encouraged.

The Relation of Sleep Characteristics and Cognitive Impairment in Community-Dwelling Middle-Aged and Older Adults: Ardakan Cohort Study on Aging (ACSA)

Introduction

The rise in the elderly population has brought attention to mild cognitive impairment (MCI). Sleep disorders also affect many older adults, indicating an important area of research for disturbed sleep and faster brain aging. This population-based study aimed to investigate the association of several sleep indicators with cognitive performance.

Methods

This cross-sectional study focused on adults over 50 in the Ardakan Cohort Study on Aging (ACSA). MCI was evaluated using the Mini-Mental State Examination (MMSE) and the Abbreviated Mental Test score (AMTS) in literate and illiterate individuals. Sleep characteristics were collected using the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale, and Berlin questionnaire. The logistic regression models were used to analyze the data.

Results

Overall, 3,380 literate and 1,558 illiterate individuals were included. In both groups, participants with MCI had a significantly higher PSQI global score (p < 0.05). Also, among the literate individuals, a significantly higher risk of having sleep-disordered breathing and poor sleep quality was observed in participants with MCI (p < 0.05). In illiterate individuals, higher sleep latency than 15 min increased odds of MCI (p < 0.05). However, after adjusting for all variables, only literate individuals with a sleep duration of more than 8 h had 66 percent increased odds of having MCI (p = 0.033).

Conclusion

Sleep duration might be associated with cognitive function in the older Iranian population. Our findings underscore the importance of considering sleep patterns in relation to cognitive health.

Age- and sex-specific associations between obstructive sleep apnea risk and cognitive decline in middle-aged and older adults: A 3-year longitudinal analysis of the Canadian longitudinal study on aging

BACKGROUND

Whether obstructive sleep apnea (OSA) increases the risk of cognitive decline and how sex and age influence this association is not clear. Here, we characterized the sex- and age-specific associations between OSA risk and 3-year cognitive change in middle-aged and older adults.

METHODS

We included 24,819 participants aged 45-85 (52% women) from the Canadian Longitudinal Study on Aging. OSA risk was measured at baseline using the STOP combined to body mass index (STOP-B). Neuropsychological tests assessed memory, executive functioning, and psychomotor speed at baseline and at 3-year follow-up. We conducted age- and sex-specific linear mixed models to estimate the predictive role of baseline STOP-B score on 3-year cognitive change.

RESULTS

Men at high-risk for OSA aged 45-59 years showed a steeper decline in psychomotor speed (+13.2 [95% CI: -1.6, 27.9]) compared to men at low-risk. Men at high-risk for OSA aged 60-69 showed a steeper decline in mental flexibility (-1.2 [-1.9, -0.5]) and processing speed (+0.6 [0.3, 0.9]) than those at low-risk. Women at high-risk for OSA aged 45-59 showed a steeper decline in processing speed (+0.1 [-0.2, 0.4]) than women at low-risk, while women at high-risk ≥70 years had a steeper decline in memory (-0.2 [-0.6, 0.1]) and processing speed (+1.0 [0.4, 1.5]).

CONCLUSIONS

Associations between OSA risk and cognitive decline over 3 years depend on age and sex. Being at high-risk for OSA is associated with a generalized cognitive decline in attention and processing speed, while a memory decline is specific to older women (≥70 years).

Objective Sleep Duration and All-Cause Mortality Among People With Obstructive Sleep Apnea

Importance

The association between sleep duration and all-cause mortality remains unclear among people with obstructive sleep apnea (OSA).

Objective

To explore whether there is an association between sleep duration and all-cause mortality among people with OSA.

Design, Setting, and Participants

This cohort study investigated participants with OSA from the Sleep Heart Health Study (SHHS) in which participants were enrolled between 1995 and 1998 with questionnaires and polysomnography (PSG) assessment and followed up for a median of 11.8 years. SHHS was a multicenter community-based study; 2574 participants with OSA defined by apnea-hypopnea index (AHI) greater than or equal to 15 from SHHS were found; all of them had all-cause mortality data and were included in the study. Data were analyzed from November 2022 to October 2023.

Exposures

Participants were divided into 4 groups with objective sleep duration of (1) at least 7 hours, (2) 6 to less than 7 hours, (3) 5 to less than 6 hours, and (4) less than 5 hours, which was determined by total sleep time on PSG at baseline.

Main Outcomes and Measures

All-cause mortality was defined as deaths from any cause and its risk was compared among 4 OSA groups using Cox regression models.

Results

A total of 2574 participants with OSA were included (1628 [63.2%] men and 946 [36.8%] women; mean [SD] age, 65.4 [10.7] years; 211 [8.2%] Black, 2230 [86.6%] White, 133 [5.2%] other race). Overall, 688 all-cause deaths were observed in participants. Compared with the group sleeping at least 7 hours, the groups sleeping 6 to less than 7 hours (hazard ratio [HR], 1.53 [95% CI, 1.13-2.07]), 5 to less than 6 hours (HR, 1.40 [95% CI, 1.03-1.90]), and less than 5 hours (HR, 1.64 [95% CI, 1.20-2.24]) had significantly higher risks of all-cause mortality independent of AHI. Sensitivity analyses were performed among participants with available data of positive airway pressure treatment during follow-up and the finding was mostly consistent, albeit the HR for the group of 5 to less than 6 hours was not statistically significant.

Conclusions and Relevance

In this cohort study of 2574 participants with OSA, those with shorter objective sleep duration had higher risk of all-cause mortality independent of AHI compared with those sleeping at least 7 hours. Further studies would be needed to investigate health benefits of extending sleep length among people with OSA with short sleep duration.

Shedding light on neurofilament involvement in cognitive decline in obstructive sleep apnea and its possible role as a biomarker

Obstructive sleep apnea is one of the most common sleep disorders with a high estimated global prevalence and a large number of associated comorbidities in general as well as specific neuropsychiatric complications such as cognitive impairment. The complex pathogenesis and effects of the disorder including chronic intermittent hypoxia and sleep fragmentation may lead to enhanced neuronal damage, thereby contributing to neuropsychiatric pathologies. Obstructive sleep apnea has been described as an independent risk factor for several neurodegenerative diseases, including Alzheimer's disease and all-cause dementia. The influence of obstructive sleep apnea on cognitive deficits is still a topic of recent debate, and several mechanisms, including neurodegeneration and depression-related cognitive dysfunction, underlying this correlation are taken into consideration. The differentiation between both pathomechanisms of cognitive impairment in obstructive sleep apnea is a complex clinical issue, requiring the use of multiple and costly diagnostic methods. The studies conducted on neuroprotection biomarkers, such as brain-derived neurotrophic factors and neurofilaments, are recently gaining ground in the topic of cognition assessment in obstructive sleep apnea patients. Neurofilaments as neuron-specific cytoskeletal proteins could be useful non-invasive indicators of brain conditions and neurodegeneration, which already are observed in many neurological diseases leading to cognitive deficits. Additionally, neurofilaments play an important role as a biomarker in other sleep disorders such as insomnia. Thus, this review summarizes the current knowledge on the involvement of neurofilaments in cognitive decline and neurodegeneration in obstructive sleep apnea patients as well as discusses its possible role as a biomarker of these changes.

Causal Associations of Sleep Apnea with Alzheimer's Disease and Cardiovascular Disease: a Bidirectional Mendelian Randomization Analysis

Background

Sleep apnea (SA) has been linked to an increased risk of dementia in numerous observational studies; whether this is driven by neurodegenerative, vascular or other mechanisms is not clear. We sought to examine the bidirectional causal relationships between SA, Alzheimer's disease (AD), coronary artery disease (CAD), and ischemic stroke using Mendelian randomization (MR).

Methods

Using summary statistics from four recent, large genome-wide association studies of SA (n=523,366), AD (n=64,437), CAD (n=1,165,690), and stroke (n=1,308,460), we conducted bidirectional two-sample MR analyses. Our primary analytic method was fixed-effects inverse variance weighted MR; diagnostics tests and sensitivity analyses were conducted to verify the robustness of the results.

Results

We identified a significant causal effect of SA on the risk of CAD (odds ratio (OR IVW ) =1.35 per log-odds increase in SA liability, 95% confidence interval (CI) =1.25-1.47) and stroke (OR IVW =1.13, 95% CI =1.01-1.25). These associations were somewhat attenuated after excluding single-nucleotide polymorphisms associated with body mass index (BMI) (OR IVW =1.26, 95% CI =1.15-1.39 for CAD risk; OR IVW =1.08, 95% CI =0.96-1.22 for stroke risk). SA was not causally associated with a higher risk of AD (OR IVW =1.14, 95% CI =0.91-1.43). We did not find causal effects of AD, CAD, or stroke on risk of SA.

Conclusions

These results suggest that SA increased the risk of CAD, and the identified causal association with stroke risk may be confounded by BMI. Moreover, no causal effect of SA on AD risk was found. Future studies are warranted to investigate cardiovascular pathways between sleep disorders, including SA, and dementia.

Mechanisms of Activation of Brain's Drainage during Sleep: The Nightlife of Astrocytes

The study of functions, mechanisms of generation, and pathways of movement of cerebral fluids has a long history, but the last decade has been especially productive. The proposed glymphatic hypothesis, which suggests a mechanism of the brain waste removal system (BWRS), caused an active discussion on both the criticism of some of the perspectives and our intensive study of new experimental facts. It was especially found that the intensity of the metabolite clearance changes significantly during the transition between sleep and wakefulness. Interestingly, at the cellular level, a number of aspects of this problem have been focused on, such as astrocytes-glial cells, which, over the past two decades, have been recognized as equal partners of neurons and perform many important functions. In particular, an important role was assigned to astrocytes within the framework of the glymphatic hypothesis. In this review, we return to the "astrocytocentric" view of the BWRS function and the explanation of its activation during sleep from the viewpoint of new findings over the last decade. Our main conclusion is that the BWRS's action may be analyzed both at the systemic (whole-brain) and at the local (cellular) level. The local level means here that the neuro-glial-vascular unit can also be regarded as the smallest functional unit of sleep, and therefore, the smallest functional unit of the BWRS.

Brain morphology and functional connectivity alterations in patients with severe obstructive sleep apnea

BACKGROUND

It has been demonstrated that widespread structural and functional brain alterations influence the development of cognitive impairment in patients with obstructive sleep apnea (OSA). However, the literature has limited evidence regarding the neuropathophysiological mechanisms behind these impairments. This research aimed to investigate brain morphologic and functional connectivity (FC) abnormalities related to neurocognitive function in OSA.

METHODS

Fifty treatment-naïve males, newly diagnosed patients with severe OSA, and 50 well-matched healthy controls (HCs) were enrolled prospectively. All subjects underwent an MRI scan, cognitive psychological and sleep scale assessment. The differences of brain morphological and seed-based FC between the two groups were compared. The correlation analysis and receiver operating characteristic curve were performed for further analysis.

RESULTS

Compared with HCs, the right brainstem, left dorsal-lateral superior frontal gyrus (SFGdor), and superior temporal gyrus (STG) exhibited atrophy in the OSA group. In addition, FC between the left SFGdor and the right postcentral gyrus (PoCG) was increased, which was positively correlated with disease duration (r = 0.312, FDR-corrected P = 0.027). The Jacobian values of the brainstem were negatively correlated with MoCA and recall scores (r = -0.449, FDR-corrected P = 0.0025; r = -0.416, FDR-corrected P = 0.005). Furthermore, the Jacobian values of the left SFGdor demonstrated a relatively high diagnostic performance (sensitivity: 86%, specificity: 56%, AUC: 0.740, 95% CI: 0.643-0.836, P < 0.0001).

CONCLUSIONS

Structural atrophy in brainstem and frontotemporal lobe and altered FC may be the neurobiological hallmark of brain impairment in OSA. Notably, brainstem atrophy has been associated with cognitive impairment, which may provide new insights into understanding the neuropathophysiological mechanisms of cognitive impairment in OSA patients.

Total sleep duration and daytime napping in relation to dementia detection risk: Results from the Million Women Study

INTRODUCTION

There is inconsistent evidence on the associations of sleep duration and daytime napping with dementia risk.

METHODS

In the Million Women Study, a total of 830,716 women (mean age, 60 years) were asked about sleep duration (<7, 7-8, >8 hours) and daytime napping (rarely/never, sometimes, usually) in median year 2001, and were followed for the first hospital record with any mention of dementia. Cox regression estimated dementia detection risk ratios (RRs) during 17-year follow-up in 5-year intervals.

RESULTS

With 34,576 dementia cases, there was strong attenuation over follow-up in the RRs related to long sleep duration (>8 vs 7-8 hours) and usually napping (vs rarely/never). Short sleep duration was modestly, positively associated with dementia in the long term (RR = 1.08, 95% confidence interval [CI] 1.04-1.12).

DISCUSSION

There was little evidence to suggest that long sleep duration and regular napping are associated with long-term dementia risk. Short sleep duration was modestly associated with dementia risk, but residual confounding cannot be excluded.

HIGHLIGHTS

Long sleep duration was not associated with long-term dementia risk. Daytime napping was not associated with long-term dementia risk. There is some evidence for a small higher risk of dementia related to short sleep.

Association of cardiometabolic multimorbidity and adherence to a healthy lifestyle with incident dementia: a large prospective cohort study

BACKGROUND

The co-occurrence of cardiometabolic diseases (CMDs) is increasingly prevalent and has been associated with an additive risk of dementia in older adults, but the extent to which this risk can be offset by a healthy lifestyle is unknown. We aimed to examine the associations of cardiometabolic multimorbidity and lifestyle with incident dementia and related brain structural changes.

METHODS

This prospective study extracted health and lifestyle data from 171 538 UK Biobank participants aged 60 years or older without dementia at baseline between 2006 and 2010 and followed up until July 2021, as well as brain structural data in a nested imaging subsample of 11 972 participants. Cardiometabolic multimorbidity was defined as the presence of two or more CMDs among type 2 diabetes, coronary heart disease, stroke, and hypertension. Lifestyle patterns were determined based on 7 modifiable lifestyle factors including smoking, alcohol consumption, physical activity, diet, sleep duration, sedentary behavior, and social contact.

RESULTS

Over a median follow-up of 12.3 years, 4479 (2.6%) participants developed dementia. The presence of CMDs was dose-dependently associated with an increased risk of dementia. Compared with participants with no CMDs and a favourable lifestyle, those with ≥ 3 CMDs and an unfavourable lifestyle had a five times greater risk of developing dementia (HR 5.33, 95% CI 4.26-6.66). A significant interaction was found between CMD status and lifestyle (Pinteraction=0.001). The absolute difference in incidence rates of dementia per 1000 person years comparing favourable versus unfavourable lifestyle was - 0.65 (95% CI - 1.02 to - 0.27) among participants with no CMDs and - 5.64 (- 8.11 to - 3.17) among participants with ≥ 3 CMDs, corresponding to a HR of 0.71 (0.58-0.88) and 0.42 (0.28-0.63), respectively. In the imaging subsample, a favourable lifestyle was associated with larger total brain, grey matter, and hippocampus volumes across CMD status.

CONCLUSION

Our findings suggest that adherence to a healthy lifestyle might substantially attenuate dementia risk and adverse brain structural changes associated with cardiometabolic multimorbidity.

Dietary amino acid intake and sleep duration are additively involved in future cognitive decline in Japanese adults aged 60 years or over: a community-based longitudinal study

BACKGROUND

Sleep duration and amino acid intake are independently associated with cognitive decline. This study aimed to determine the longitudinal association between sleep duration and cognitive impairment incidence and to examine the involvement of diet, particularly amino acid intake, in these associations in community dwellers.

METHODS

In this longitudinal study in a community-based setting, we analyzed data from 623 adults aged 60-83 years without cognitive impairment at baseline. Sleep duration was assessed using a self-report questionnaire. Amino acid intake was assessed using 3-day dietary records. Cognitive impairment was defined as a Mini-Mental State Examination score ≤ 27. Participants were classified into short-, moderate-, and long-sleep groups according to baseline sleep duration (≤ 6, 7-8, and > 8 h, respectively). Using moderate sleep as a reference, odds ratios (ORs) and 95% confidence intervals (CIs) of short- and long-sleep for cognitive-impairment incidence were estimated using the generalized estimating equation. Participants were classified according to sex-stratified quartiles (Q) of 19 amino acid intake: Q1 and Q2-Q4 were low- and middle to high-intake groups, respectively. Using middle- to high-intake as a reference, ORs and 95% CIs of low intake for cognitive impairment incidence were estimated using the generalized estimating equation in each sleep-duration group. Follow-up period, sex, age, body mass index, depressive symptoms, education, smoking status, employment status, sleep aids use, physical activity, medical history, and Mini-Mental State Examination score at baseline were covariates.

RESULTS

Mean follow-up period was 6.9 ± 2.1 years. Adjusted ORs (95% CIs) for cognitive impairment in short- and long-sleep groups were 0.81 (0.49-1.35, P = 0.423) and 1.41 (1.05-1.87, P = 0.020), respectively. Particularly in long sleepers (i.e., > 8 h), cognitive impairment was significantly associated with low cystine, proline, and serine intake [adjusted ORs (95% CIs) for cognitive impairment were 2.17 (1.15-4.11, P = 0.017), 1.86 (1.07-3.23, P = 0.027), and 2.21 (1.14-4.29, P = 0.019), respectively].

CONCLUSIONS

Community-dwelling adults aged ≥ 60 years who sleep longer are more likely to have cognitive decline, and attention should be paid to the low cystine, proline, and serine intake.

Associations of sleep characteristics in late midlife with late-life hearing loss in the Atherosclerosis Risk in Communities-Sleep Heart Health Study (ARIC-SHHS)

OBJECTIVES

This study investigated associations of late midlife sleep characteristics with late-life hearing, which adds to the existing cross-sectional evidence and is novel in examining polysomnographic sleep measures and central auditory processing.

METHODS

A subset of Atherosclerosis Risk in Communities Study participants underwent sleep assessment in the Sleep Heart Health Study in 1996-1998 and hearing assessment in 2016-2017. Peripheral hearing thresholds (0.5-4kHz) assessed by pure-tone audiometry were averaged to calculate speech-frequency pure-tone average in better-hearing ear (higher pure-tone average=worse hearing). Central auditory processing was measured by the Quick Speech-in-Noise Test (lower score=worse performance). Sleep was measured using polysomnography (time spent in stage 1, stage 2, stage 3/4, rapid eye movement sleep; sleep-disordered breathing [apnea-hypopnea index ≥5]) and self-report (habitual sleep duration; excessive daytime sleepiness [Epworth Sleepiness Scale 10]). Linear regression models adjusted for demographic and lifestyle factors with additional adjustment for cardiovascular factors.

RESULTS

Among 719 Atherosclerosis Risk in Communities-Sleep Heart Health Study participants (61 ± 5years, 54% female, 100% White), worse speech-frequency pure-tone average was found with sleep-disordered breathing (2.51dB, 95% confidence interval: 0.27, 4.75) and excessive daytime sleepiness (3.35 dB, 95% confidence interval: 0.81, 5.90). Every additional hour of sleep when sleeping >8 hours was associated with worse Quick Speech-in-Noise score (1.61 points, 95% confidence interval: 0.03, 3.19). Every 10-minute increase in rapid eye movement sleep was associated with 0.14-point better Quick Speech-in-Noise score (95% confidence interval: 0.02, 0.25).

CONCLUSIONS

Sleep abnormalities might be risk factors for late-life hearing loss. Future longitudinal studies are needed to confirm these novel findings and clarify the mechanisms.

Self-reported sleep in relation to risk of dementia a quarter of a century later at age 90+: The 90+ Study

OBJECTIVE

To examine sex-specific associations of sleep duration and napping self-reported at mean age of 69 years (range: 53-81) with risk of incident dementia 24 years later at age 90 +.

METHOD

Analytic sample included individuals from a population-based study who reported sleep and napping once in the 1980s and 24 years later (range: 16-38) joined The 90+ Study and were evaluated in-person. Those without dementia at baseline of The 90+ Study were prospectively followed. Hazard ratios [HR] and 95% confidence intervals [CI] of dementia risk were estimated by Cox regression.

RESULTS

Of 574 participants 71% were women, mean age at start of dementia follow-up with The 90+ Study was 93 years (range: 90-102). After 3.3 years (range: 0.4-13.8) of follow-up 47% developed dementia. Higher risk of dementia at age 90+ was seen in women with <6 hours of self-reported sleep per night (adjusted HR = 2.00; 95% CI = 1.15-3.50; p = .01) compared with 8 hours. Lower risk of dementia at 90+ was seen in men with short-to-moderate (<60 minutes) self-reported naps compared with no naps (HR = 0.33; 95% CI = 0.18-0.63; p < .01).

CONCLUSIONS

Sleep and nap 24 years earlier are important risk factors for dementia after age 90.

Alterations of Limbic Structure Volumes in Patients with Obstructive Sleep Apnea

OBJECTIVES

We investigated the change in limbic structure volumes and intrinsic limbic network in patients with obstructive sleep apnea (OSA) compared to healthy controls.

METHODS

We enrolled 26 patients with OSA and 30 healthy controls. They underwent three-dimensional T1-weighted magnetic resonance imaging (MRI) on a 3 T MRI scanner. The limbic structures were analyzed volumetrically using the FreeSurfer program. We examined the intrinsic limbic network using the Brain Analysis with Graph Theory program and compared the groups' limbic structure volumes and intrinsic limbic network.

RESULTS

There were significant differences in specific limbic structure volumes between the groups. The volumes in the right amygdala, right hippocampus, right hypothalamus, right nucleus accumbens, left amygdala, left basal forebrain, left hippocampus, left hypothalamus, and left nucleus accumbens in patients with OSA were lower than those in healthy controls (right amygdala, 0.102 vs. 0.113%, p = 0.004; right hippocampus, 0.253 vs. 0.281%, p = 0.002; right hypothalamus, 0.028 vs. 0.032%, p = 0.002; right nucleus accumbens, 0.021 vs. 0.024%, p = 0.019; left amygdala, 0.089 vs. 0.098%, p = 0.007; left basal forebrain, 0.020 vs. 0.022%, p = 0.027; left hippocampus, 0.245 vs. 0.265%, p = 0.021; left hypothalamus, 0.028 vs. 0.031%, p = 0.016; left nucleus accumbens, 0.023 vs. 0.027%, p = 0.002). However, there were no significant differences in network measures between the groups.

CONCLUSION

We demonstrate that the volumes of several limbic structures in patients with OSA are significantly lower than those in healthy controls. However, there are no alterations to the intrinsic limbic network. These findings suggest that OSA is one of the risk factors for cognitive impairments.