Treatment of sleep apnoea syndrome decreases cognitive decline in patients with Alzheimer's disease

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.

Pharmacological interventions to improve sleep in people with Alzheimer's disease: a meta-analysis of randomized controlled trials

INTRODUCTION

This systematic review and meta-analysis evaluates the evidence from randomized controlled trials (RCTs) involving pharmacological interventions for improving sleep in people with Alzheimer's disease (AD).

METHODS

A systematic literature search in eight databases from January 2000 to July 2023 focusing on RCTs that compared a pharmacological intervention with a placebo for enhancing sleep in people with AD. The authors registered the study protocol at Prospero, followed the PRISMA guidelines, and produced the pooled estimates using random-effect or IVhet models.

RESULTS

Eight different interventions and 29 different sleep outcomes were examined in 14 RCTs included in this review. Eszopiclone positively affected sleep efficiency, as did orexin antagonists. However, there was no difference when melatonin was used. The interventions demonstrated low discontinuation rates and a few adverse drug reactions.

CONCLUSION

Although melatonin was the most investigated intervention, the evidence for its efficacy is inconclusive. On the other hand, trazodone and orexin receptor antagonists showed promising results; however, more RCTs are needed for definite answers.

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.

Sleep disorders and Alzheimer's disease pathophysiology: The role of the Glymphatic System. A scoping review

BACKGROUND

Alzheimer's disease (AD) is highly intertwined with sleep disturbances throughout its whole natural history. Sleep consists of a major compound of the functionality of the glymphatic system, as the synchronized slow-wave activity during NREM facilitates cerebrospinal and interstitial long-distance mixing.

OBJECTIVE

The present study undertakes a scoping review of research on the involvement of the glymphatic system in AD-related sleep disturbances.

DESIGN

we searched Medline, Embase, PsychInfo and HEAL-link databases, without limitations on date and language, along with reference lists of relevant reviews and all included studies. We included in vivo, in vitro and post-mortem studies examining glymphatic implications of sleep disturbances in human populations with AD spectrum pathology. A thematic synthesis of evidence based on the extracted content was applied and presented in a narrative way.

RESULTS

In total, 70 original research articles were included and were grouped as following: a) Protein aggregation and toxicity, after sleep deprivation, along with its effects on sleep architecture, b) Glymphatic Sequalae in SDB, yielding potential glymphatic markers c) Circadian Dysregulation, d) Possible Interventions.

CONCLUSIONS

this review sought to provide insight into the role of sleep disturbances in AD pathogenesis, in the context of the glymphatic disruption.

A systematic review on adherence to continuous positive airway pressure (CPAP) treatment for obstructive sleep apnoea (OSA) in individuals with mild cognitive impairment and Alzheimer's disease dementia

Obstructive sleep apnoea (OSA) is highly prevalent in mild cognitive impairment (MCI) and Alzheimer's disease (AD). The gold standard treatment for OSA is continuous positive airway pressure (CPAP). Long-term, well-powered efficacy trials are required to understand whether CPAP could slow cognitive decline in individuals with MCI/AD, but its tolerability in this group remains uncertain. The present review investigates CPAP adherence among individuals with OSA and MCI/AD. Electronic searches were performed on 8 databases. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Six independent studies and four secondary analyses included 278 unique participants (mean age = 72.1 years). In five of the retained studies, around half of participants (45% N = 85 MCI, 56% N = 22 AD) were adherent to CPAP, where ≥4 h use per night was considered adherent. Three of the retained studies also reported average CPAP use to range between 3.2 and 6.3 h/night. CPAP adherence in individuals with MCI and AD is low, albeit similar to the general elderly population. Reporting adherence in future studies as both average duration as well as using a binary cut-off would improve our understanding of the optimum CPAP use in dementia clinical trials and care.

Continuous positive airway pressure compliance in patients with mild cognitive impairment

PURPOSE

Sleep apnoea (SA) is associated with accelerated cognitive decline in patients with mild cognitive impairment (MCI). Treatment of SA by continuous positive airway pressure (CPAP) may slow this decline if patients comply with the treatment. The aim of this study was to assess the rate of CPAP compliance in this population.

METHODS

In this single-centre retrospective study conducted in a tertiary care institution, patients with a diagnosis of MCI and SA initiating CPAP between January 2015 and August 2021 were included. Data from the initial sleep recording, the 3-month follow-up and compliance with at least 12 months of CPAP were analysed. Compliance was defined as an average CPAP use of at least 4 h per night.

RESULTS

55 patients were included (49% women, age 70.7 ± 8.9 years, body mass index 28.9 ± 6.5 kg/m2). Aetiology of MCI was vascular (45.5%), psychiatric (12.7%) and related to Alzheimer's disease (7.3%), with 47.3% of amnesic disorders and 45.5% of dysexecutive disorders. The MiniMentalState score was 26.7 ± 3.1. SA was mostly obstructive (81.8%) with a mean apnoea-hypopnoea index of 41.1 ± 16.4/h. At 3 months, 38 patients were compliant (69%) with a CPAP median use of 5.9 h per night and 83% of nights. Self-reported tolerance was better in compliant patients (75.7% vs 38.5% p = 0.017). Thirty-four patients remained compliant at 12 months (62%).

CONCLUSION

Our results suggest a high rate of CPAP compliance in patients suffering from MCI. Compliance was related to the device tolerance, emphasizing the need to closely monitor and improve this factor.

Sex and Sleep Disruption as Contributing Factors in Alzheimer's Disease

Alzheimer's disease (AD) affects more women than men, with women throughout the menopausal transition potentially being the most under researched and at-risk group. Sleep disruptions, which are an established risk factor for AD, increase in prevalence with normal aging and are exacerbated in women during menopause. Sex differences showing more disrupted sleep patterns and increased AD pathology in women and female animal models have been established in literature, with much emphasis placed on loss of circulating gonadal hormones with age. Interestingly, increases in gonadotropins such as follicle stimulating hormone are emerging to be a major contributor to AD pathogenesis and may also play a role in sleep disruption, perhaps in combination with other lesser studied hormones. Several sleep influencing regions of the brain appear to be affected early in AD progression and some may exhibit sexual dimorphisms that may contribute to increased sleep disruptions in women with age. Additionally, some of the most common sleep disorders, as well as multiple health conditions that impair sleep quality, are more prevalent and more severe in women. These conditions are often comorbid with AD and have bi-directional relationships that contribute synergistically to cognitive decline and neuropathology. The association during aging of increased sleep disruption and sleep disorders, dramatic hormonal changes during and after menopause, and increased AD pathology may be interacting and contributing factors that lead to the increased number of women living with AD.

Positive airway pressure adherence among patients with obstructive sleep apnea and cognitive impairment: A narrative review

Adults with Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) have increased rates of Obstructive Sleep Apnea (OSA). Positive Airway Pressure (PAP) is the first-line treatment for OSA and may have potential benefits for slowing cognitive decline in these individuals. However, adherence is low in PAP users overall and those with cognitive impairment may have unique challenges. Furthermore, there has been little systematic study of the use of PAP or strategies to enhance PAP adherence among those with AD or MCI. The aim of this review is to examine existing observational, quasi-experimental and experimental studies of the effects of PAP on cognitive function. In addition, our goal was to gather evidence about the adherence rates, and support for PAP among adults with MCI and mild to moderate AD. Through searches of electronic databases (University of Utah Library, SAGE Publishing, PubMed, Wiley, EBSCO, Science Direct, ProQuest, and NCBI), we identified 11 articles that fit our study inclusion criteria. Synthesis of data was performed with a focus on cognitive outcomes of PAP interventions and adherence. Findings from the studies showed that multiple indices of memory improved with PAP use. Adherence in MCI and AD populations was largely comparable to adherence reported in general adult populations, but more research is needed to optimize systems for providing support for PAP users and caregivers. Results support PAP as a promising intervention in this population but more research is needed to make definitive conclusions about the relationship between PAP use and improved cognitive function. Furthermore, research is needed to determine if additional interventions are needed to support patients and caregivers.

Adherence to continuous positive airway pressure for the treatment of obstructive sleep apnea in neurodegenerative diseases: A systematic review

Obstructive sleep apnea (OSA) is prevalent in patients with neurodegenerative diseases and is associated with worse outcomes. Positive airway pressure therapy has the potential to benefit these patients but can be challenging in this population. Our primary aim was to describe positive pressure therapy adherence. Secondarily, we aimed at identifying identify predictors of adherence to treatment in adults with neurodegenerative diseases and OSA, and report the effect of PAP adherence on outcomes such as cognitive function, quality of life and patient/caregiver satisfaction. We performed a systematic review of the literature and identified seventeen studies, eight reporting on adults with obstructive sleep apnea and mild cognitive impairment (MCI) and/or Alzheimer's disease (AD), 6 with Parkinson's disease (PD), and 3 with multiple system atrophy (MSA). Meta-analyses were not performed due to lack of systematic and standardized reporting of the primary outcome. Study duration ranged from 6 weeks to an average of 3.3 years. PAP adherence definition was widely variable between studies. Attrition rates ranged from 12% to 75%. In MCI/AD, adherence rates ranged from 28% to 61% (study duration range: 3 weeks to 3.3 years). Younger age, race (white) and better CPAP confidence scores at 1 week were associated with more CPAP use while APOE4 positive and unmarried individuals were more likely to abandon CPAP. In most studies, adherent patients had improvement in excessive daytime sleepiness, depressive symptoms, sleep quality, ability to manage daily activities and certain aspects of cognition (composite score or global cognition, psychomotor speed, executive function), as well as less cognitive decline over time. Caregiver satisfaction was also better in PAP adherent patients in one study. In PD, 15-25% of individuals refused treatment with PAP upfront, and attrition ranged from 8 to 75%. Adherent patients used their device for an average of 3h27 to 5h12 per night (study duration range: 6 weeks to 12 months). Longer disease duration, worse motor symptoms or sleep quality and lower % of REM sleep were identified as predictors of lower PAP adherence in a preliminary study, while race (non-white) and sex (women) were linked to lower adherence in a large retrospective study. In the study reporting the highest attrition rate (75%), individuals had lower educational levels. PAP adherence improved daytime sleepiness, anxiety symptoms, sleep architecture and quality and global non-motor symptoms. However, in one short-term (3 weeks) study, there was no improvement in neuropsychological testing composite score. Three studies on MSA patients suffering from sleep-disordered breathing showed that most patients are accepting of PAP (69-72%) with an average nightly use of 4h42 to 6h18. Floppy epiglottis was more frequently seen in patients discontinuing PAP in one study. In one study, four adults with MSA and long-term PAP use reported better sleep and improved vigilance. Survival time was no different between treated and untreated individuals. In conclusion, PAP therapy is challenging in patients with OSA and NDD, as evidenced by the considerable attrition and low adherence rates reported in this systematic review. There is emerging evidence proposing OSA a treatable target to prevent clinical and functional deterioration in patients with neurodegenerative diseases and addressing potential barriers to PAP adherence is paramount to maximize adherence. Our systematic review outlines several of these potential barriers, underscoring the need for future studies to standardize the definition of and explore long-term adherence to PAP therapy and assess interventions that can optimize adherence in this patient population.

Sleepiness in neurological disorders

Sleepiness is a frequent and underrecognized symptom in neurological disorders, that impacts functional outcomes and quality of life. Multiple and potentially additive factors might contribute to sleepiness in neurological disorders, including sleep quality alterations, circadian rhythm disorders, drugs, and sleep disorders including sleep apnea or central disorders of hypersomnolence. Physician awareness of the possible symptoms of hypersomnolence, and associated causes is of crucial importance to allow proper identification and treatment of underlying causes. This review first provides a brief overview on clinical aspects of excessive daytime sleepiness, and diagnosis tools, then examines its frequency and mechanisms in various neurological disorders, including neurodegenerative disorders, multiple sclerosis, autoimmune encephalitis, epilepsy, and stroke.

Sleep electroencephalography biomarkers of cognition in obstructive sleep apnea

Obstructive sleep apnea has been associated with cognitive impairment and may be linked to disorders of cognitive function. These associations may be a result of intermittent hypoxaemia, sleep fragmentation and changes in sleep microstructure in obstructive sleep apnea. Current clinical metrics of obstructive sleep apnea, such as the apnea-hypopnea index, are poor predictors of cognitive outcomes in obstructive sleep apnea. Sleep microstructure features, which can be identified on sleep electroencephalography of traditional overnight polysomnography, are increasingly being characterized in obstructive sleep apnea and may better predict cognitive outcomes. Here, we summarize the literature on several major sleep electroencephalography features (slow-wave activity, sleep spindles, K-complexes, cyclic alternating patterns, rapid eye movement sleep quantitative electroencephalography, odds ratio product) identified in obstructive sleep apnea. We will review the associations between these sleep electroencephalography features and cognition in obstructive sleep apnea, and examine how treatment of obstructive sleep apnea affects these associations. Lastly, evolving technologies in sleep electroencephalography analyses will also be discussed (e.g. high-density electroencephalography, machine learning) as potential predictors of cognitive function in obstructive sleep apnea.

Cerebrospinal fluid lipidomic fingerprint of obstructive sleep apnoea in Alzheimer's disease

BACKGROUND

Obstructive sleep apnoea (OSA) has a high prevalence in patients with Alzheimer's disease (AD). Both conditions have been shown to be associated with lipid dysregulation. However, the relationship between OSA severity and alterations in lipid metabolism in the brains of patients with AD has yet to be fully elucidated. In this context, we examined the cerebrospinal fluid (CSF) lipidome of patients with suspected OSA to identify potential diagnostic biomarkers and to provide insights into the pathophysiological mechanisms underlying the effect of OSA on AD.

METHODS

The study included 91 consecutive AD patients who underwent overnight polysomnography (PSG) to diagnose severe OSA (apnoea-hypopnea index ≥ 30/h). The next morning, CSF samples were collected and analysed by liquid chromatography coupled to mass spectrometry in an LC-ESI-QTOF-MS/MS platform.

RESULTS

The CSF levels of 11 lipid species were significantly different between AD patients with (N = 38) and without (N = 58) severe OSA. Five lipids (including oxidized triglyceride OxTG(57:2) and four unknown lipids) were significantly correlated with specific PSG measures of OSA severity related to sleep fragmentation and hypoxemia. Our analyses revealed a 4-lipid signature (including oxidized ceramide OxCer(40:6) and three unknown lipids) that provided an accuracy of 0.80 (95% CI: 0.71-0.89) in the detection of severe OSA. These lipids increased the discriminative power of the STOP-Bang questionnaire in terms of the area under the curve (AUC) from 0.61 (0.50-0.74) to 0.85 (0.71-0.93).

CONCLUSIONS

Our results reveal a CSF lipidomic fingerprint that allows the identification of AD patients with severe OSA. Our findings suggest that an increase in central nervous system lipoxidation may be the principal mechanism underlying the association between OSA and AD.

Treatment of hypertension and obstructive sleep apnea counteracts cognitive decline in common neurocognitive disorders in diagnosis-related patterns

The aim of this study was to investigate the effect of arterial hypertension (AH) and of obstructive sleep apnea (OSA) on cognitive course in the neurocognitive disorder (NCD) cohort RIFADE which enrolled patients with NCD due to Alzheimer's disease (AD), vascular NCD (vNCD), and mixed NCD (AD + vNCD = mNCD). Multiple risk factors (RF), including AH and OSA, that contribute to the development of various kinds of dementia have been identified in previous studies. Studies that observed AH lacked investigation of long-term effects and did not isolate it from other RF. Studies involving OSA as a risk factor did not include participants with all stages of NCD. 126 subjects were screened for AH and OSA. Repeated cognitive measurements were performed with the DemTect as primary outcome and the clock drawing test as secondary outcome measure. 90 patients had AH (71.4%) and 40 patients had OSA (31.7%). RF-status had a significant effect on cognitive outcome in models with RF as single factors (AH p = 0.027, OSA p < 0.001), a 2-factor analysis with AH × OSA (AH as main factor p = 0.027) as well as a model including the 3 factors AH × OSA × diagnosis (p = 0.038). Similarly, a 3-factor model was significant for the clock-drawing test, whereas single factor-models remained insignificant. AH and OSA appear to be risk factors in common NCD and cognitive decline can be mitigated by treatment of these RF.

Synaptic loss and gliosis in the nucleus tractus solitarii with streptozotocin-induced Alzheimer's disease

Obstructive sleep apnea is highly prevalent in Alzheimer's disease (AD). However, brainstem centers controlling respiration have received little attention in AD research, and mechanisms behind respiratory dysfunction in AD are not understood. The nucleus tractus solitarii (nTS) is an important brainstem center for respiratory control and chemoreflex function. Alterations of nTS integrity, like those shown in AD patients, likely affect neuronal processing and adequate control of breathing. We used the streptozotocin-induced rat model of AD (STZ-AD) to analyze cellular changes in the nTS that corroborate previously documented respiratory dysfunction. We used 2 common dosages of STZ (2 and 3 mg/kg STZ) for model induction and evaluated the early impact on cell populations in the nTS. The hippocampus served as control region to identify site-specific effects of STZ. There was significant atrophy in the caudal nTS of the 3 mg/kg STZ-AD group only, an area known to integrate chemoafferent information. Also, the hippocampus had significant atrophy with the highest STZ dosage tested. Both STZ-AD groups showed respiratory dysfunction along with multiple indices for astroglial and microglial activation. These changes were primarily located in the caudal and intermediate nTS. While there was no change of astrocytes in the hippocampus, microglial activation was accompanied by a reduction in synaptic density. Together, our data demonstrate that STZ-AD induces site-specific effects on all major cell types, primarily in the caudal/intermediate nTS. Both STZ dosages used in this study produced a similar outcome and can be used for future studies examining the initial symptoms of STZ-AD.

Analysis of Sleep Quality in People With Dementia: A Preliminary Study

Background: Between 25% and 60% of subjects with dementia have shown sleep disturbances. Causes are diverse and seem to be related to factors such as aging, the presence of psychiatric diseases, or the consumption of drugs. This study aims to determine the influence of dementia on sleep quality and to analyze the factors that influence sleep quality in subjects ≥65 years. Methods: Thirty-one subjects were studied (15 living with dementia). PSQI was administered and statistical analysis compared the results among categories of other variables (age, gender, coffee consumption, drugs, BMI, psychiatric diseases). This study took place in Spain. Results: A prevalence of 46.7% of sleep disturbances was found in subjects with dementia. No significant differences were observed in the total score obtained in the PSQI between the dementia group (6.06 ± 3.78 points) and the group without dementia (7 ± 5.65 points). A significant inverse relationship was found between the sleep quality and the number of daily drugs and the presence of psychiatric diseases. Conclusion: Poor sleep quality affects people with dementia, however, we cannot affirm that dementia is the cause of it. Consumption of daily drugs and psychiatric diseases are factors that influence the sleep quality in subjects aged ≥65 years.

Alzheimer's disease biomarkers in patients with obstructive sleep apnea hypopnea syndrome and effects of surgery: A prospective cohort study

Background

Obstructive sleep apnea hypopnea syndrome (OSAHS) may cause Alzheimer's disease (AD), t-tau, p-tau, Aβ42, and Aβ40 are important elements in the process of AD, and changes in the levels of these biomarkers may affect the cognitive functioning of patients. Our objective was to investigate whether uvulopalatopharyngoplasty could reduce the plasma levels of AD biomarkers in OSAHS patients and the potential correlations of AD biomarkers with cognitive impairment and sleepiness, and explore the independent influencing factors of cognitive function.

Methods

Alzheimer's disease biomarkers were measured in the plasma of 35 patients with severe OSAHS requiring surgical treatment and 16 healthy controls without OSAHS. The cognitive function and sleepiness of OSAHS patients was also evaluated. The case group was given uvulopalatopharyngoplasty and followed at the postoperative sixth month, the follow-up cases were 27, and plasma AD biomarker levels, cognitive function, and sleepiness were re-evaluated. The preoperative and postoperative AD biomarker levels OSAHS patients were compared with each other and those of the control group. Linear stepwise regression and lasso regression were used to explore the relationships of AD biomarkers with cognitive impairment and sleepiness.

Results

Significantly higher Aβ40, t-tau, p-tau in plasma were observed preoperatively in OSAHS patients comparing to controls (29.24 ± 32.52 vs. 13.18 ± 10.78, p = 0.049; 11.88 ± 7.05 vs. 7.64 ± 4.17, p = 0.037; 26.31 ± 14.41 vs. 17.34 ± 9.12, p = 0.027). The sixth month of postoperation, the plasma AD biomarkers (Aβ42, Aβ40, t-tau, p-tau) in plasma levels decreased significantly (0.23 ± 0.17 vs. 0.20 ± 0.16, p = 0.0001; 29.24 ± 32.52 vs. 23.52 ± 24.46, p = 0.0046; 11.88 ± 7.05 vs. 8.88 ± 6.21, p = 0.0001;26.31 ± 14.41 vs. 20.43 ± 10.50, p = 0.0001). A comparison of MMSE and ESS scores from before to after surgery revealed obvious differences (27.14 ± 1.65 vs. 29.07 ± 1.78, p = 0.0001; 11.91 ± 4.84 vs. 5.89 ± 2.83, p = 0.0001). Changes in cognitive function and sleepiness scores from before to after uvulopalatopharyngoplasty were significantly correlated with AD biomarkers. Body mass index and t-tau were potential influencing factors cognitive function.

Conclusion

Obstructive sleep apnea hypopnea syndrome can increase plasma AD biomarkers levels. Uvulopalatopharyngoplasty can improve patients' cognition and sleepiness, and the mechanism may be related to changes in plasma AD biomarkers. Higher AHI and higher t-tau level were identified as independent risk factors for cognitive decline.

Investigating changes in cognition associated with the use of CPAP in cognitive impairment and dementia: A retrospective study

STUDY OBJECTIVES

To characterize the impact of CPAP use on cognition in a clinical cohort with obstructive sleep apnea (OSA) and cognitive impairment due to neurodegenerative or vascular etiologies after controlling for baseline sleepiness.

METHODS

We retrospectively analyzed data from 171 patients with cognitive impairment and an OSA diagnosis confirmed with in-laboratory polysomnography or home sleep apnea testing (mean age 69.8 ± 10.6; 66% male) who were eligible to use CPAP. Baseline and follow-up Epworth Sleepiness Score (ESS), Montreal Cognitive Assessment (MoCA), and Mini-Mental Status Examination (MMSE) were obtained from clinical and research visits conducted before and after CPAP initiation. Good CPAP adherence was defined as CPAP use ≥4 h/night, for 7 days/week at follow-up. Associations between CPAP adherence and follow-up cognitive scores were analyzed using multivariable linear mixed-effects models.

RESULTS

After adjusting for age, sex, body mass index, baseline ESS, duration of CPAP therapy, relevant comorbidities and the random effect of research study cohort, good CPAP adherence (compared to poor CPAP adherence or no use of CPAP) for a duration of 2-12 months was associated with a 2.3-point (1.2-3.3 95% CI) higher follow-up MoCA score (p < 0.001) and a 1.2-point (0.3-2.3 95% CI) higher follow-up MMSE score (p = 0.01).

CONCLUSIONS

In patients with OSA and cognitive impairment due to a neurodegenerative or vascular etiology, use of CPAP is associated with improved cognitive outcomes. The findings of this study may aid in motivating patients to use CPAP and support future randomized controlled trials in this area.

Blood-based lipidomic signature of severe obstructive sleep apnoea in Alzheimer's disease

Background

Obstructive sleep apnoea (OSA) is the most frequent form of sleep-disordered breathing in patients with Alzheimer’s disease (AD). Available evidence demonstrates that both conditions are independently associated with alterations in lipid metabolism. However, it is unknown whether the expression of lipids is different between AD patients with and without severe OSA. In this context, we examined the plasma lipidome of patients with suspected OSA, aiming to identify potential diagnostic biomarkers and to provide insights into the pathophysiological mechanisms underlying the disease.

Methods

The study included 103 consecutive patients from the memory unit of our institution with a diagnosis of AD. The individuals were subjected to overnight polysomnography (PSG) to diagnose severe OSA (apnoea-hypopnea index ≥30/h), and blood was collected the following morning. Untargeted plasma lipidomic profiling was performed using liquid chromatography coupled with mass spectrometry.

Results

We identified a subset of 44 lipids (mainly phospholipids and glycerolipids) that were expressed differently between patients with AD and severe and nonsevere OSA. Among the lipids in this profile, 30 were significantly correlated with specific PSG measures of OSA severity related to sleep fragmentation and hypoxemia. Machine learning analyses revealed a 4-lipid signature (phosphatidylcholine PC(35:4), cis-8,11,14,17-eicosatetraenoic acid and two oxidized triglycerides (OxTG(58:5) and OxTG(62:12)) that provided an accuracy (95% CI) of 0.78 (0.69–0.86) in the detection of OSA. These same lipids improved the predictive power of the STOP-Bang questionnaire in terms of the area under the curve (AUC) from 0.61 (0.50–0.74) to 0.80 (0.70–0.90).

Conclusion

Our results show a plasma lipidomic fingerprint that allows the identification of patients with AD and severe OSA, allowing the personalized management of these individuals. The findings suggest that oxidative stress and inflammation are potential prominent mechanisms underlying the association between OSA and AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-022-01102-8.

The mobile sleep medicine model in neurologic practice: Rationale and application

Background

Undiagnosed obstructive sleep apnea (OSA) is prevalent in neurological practice and significantly contributes to morbidity and mortality. OSA is prevalent in US adults and causes poor quality sleep and significant neurocognitive, cardiovascular, and cerebrovascular impairments. Timely treatment of OSA reduces cardio-cerebrovascular risks and improves quality of life. However, most of the US population has limited systematic access to sleep medicine care despite its clinical significance.

Focus

We discuss the importance of systematic screening, testing, and best-practice management of OSA and hypoventilation/hypoxemia syndromes (HHS) in patients with stroke, neurocognitive impairment, and neuromuscular conditions. This review aims to introduce and describe a novel integrated Mobile Sleep Medicine (iMSM) care model and provide the rationale for using an iMSM in general neurological practice to assist with systematic screening, testing and best-practice management of OSA, HHS, and potentially other sleep conditions.

Key points

The iMSM is an innovative, patient-centered, clinical outcome-based program that uses a Mobile Sleep Medicine Unit—a “sleep lab on wheels”—designed to improve access to OSA management and sleep care at all levels of health care system. The protocol for the iMSM care model includes three levels of operations to provide effective and efficient OSA screening, timely testing/treatment plans, and coordination of further sleep medicine care follow-up. The iMSM care model prioritizes effective, efficient, and patient-centered sleep medicine care; therefore, all parties and segments of care that receive and provide clinical sleep medicine services may benefit from adopting this innovative approach.

Sleep Disturbances in Neurological Disease: A Target for Intervention

Sleep is a biological function required for neurological and general health, but a significant and under-recognized proportion of the population has disturbed sleep. Here, we briefly overview the biology of sleep, sleep requirements over the lifespan, and common sleep disorders. We then turn our attention to five neurological diseases that significantly contribute to global disease burden and neurology practice makeup: epilepsy, headache, ischemic stroke, Parkinson's disease, and Alzheimer's disease. For each disease, we review evidence that sleep disturbances contribute to disease risk and severity and discuss existing data that addressing sleep disturbances may have disease-modifying effects. We provide recommendations derived from the literature and existing clinical guidelines to facilitate the evaluation and management of sleep disturbances within the context of each neurological disease. Finally, we synthesize identified needs and commonalities into future directions for the field and practical sleep-related recommendations for physicians caring for patients at risk for or currently suffering from neurological disease.

Rationale and study protocol for We-PAP: a randomized pilot/feasibility trial of a couples-based intervention to promote PAP adherence and sleep health compared to an educational control

BACKGROUND

Obstructive sleep apnea (OSA) is a serious health condition that affects approximately 30-50% of older adults and contributes to risk for cardiometabolic disorders and dementia. Despite the well-documented role of partners in treatment seeking and adherence to positive airway pressure (PAP), treatments for OSA have nearly exclusively focused on the patient and current treatments for OSA do not address co-existing sleep problems such as insomnia that are prevalent in both patients with OSA and their partners. Therefore, the goal of this study is to develop and test a novel couples-based sleep health intervention to promote adherence to PAP and improve sleep health of the couple.

METHODS

We are conducting a two-arm, parallel group, single blind, randomized controlled pilot/feasibility trial to compare our novel couples-based sleep health intervention (We-PAP) to an information control group (IC). We-PAP is based on a transdiagnostic model and uses a dyadic approach including increasing effective partner support, communication skills, and couple-level goal-setting. We-PAP involves 3 sessions and delivered via telehealth in weekly sessions. The IC includes standardized patient educational materials. Both groups receive the usual follow-up with their medical team. The study involves assessments at pre-treatment, post-intervention (approximately 1 month after starting PAP and completing We-PAP sessions or IC) and 3 months after starting PAP. Our main outcomes are feasibility and acceptability ratings. Secondary outcomes include comparing We-PAP to IC for PAP adherence, sleep quality (self-report and objective) and cognitive measures.

DISCUSSION

We-PAP is the first couples-based transdiagnostic sleep health intervention for patients with OSA and their partners. Results of this study will be used to inform the design of a subsequent fully powered clinical trial. If successful, this intervention could significantly advance current clinical practice in the treatment of OSA and sleep health more comprehensively in older adults. Moreover, this intervention may be useful for improving sleep in other aging populations with multiple sleep and other health problems, including patients with chronic illnesses or those at risk for Alzheimer's disease and their caregivers.

TRIAL REGISTRATION

NCT04759157 . Date of registration: February 8, 2021. URL of trial registry record.

Positive Airway Pressure and Cognitive Disorders in Adults With Obstructive Sleep Apnea: A Systematic Review of the Literature

BACKGROUND AND OBJECTIVES

Alzheimer disease (AD) and other forms of dementia represent a rising global public health crisis. Because effective treatments to prevent, cure, or slow progression of dementia are unavailable, identification of treatable risk factors that increase dementia risk such as obstructive sleep apnea (OSA) could offer promising means to modify dementia occurrence or severity. Here, we systematically reviewed the impact of positive airway pressure (PAP) therapy on the incidence of cognitive disorders and cognitive decline among middle-aged and older adults with OSA.

METHODS

We performed a systematic search of MEDLINE, EMBASE, Scopus, and CINAHL before May 2021 to identify articles that focused on associations between PAP therapy use and cognitive disorders. We included studies that examined the effects of PAP treatment on (1) the incidence of cognitive disorders among individuals ≥40 years of age diagnosed with OSA and (2) the progression of cognitive decline among people with preexisting cognitive disorders and OSA.

RESULTS

We identified 11 studies (3 clinical trials and 8 observational studies). In these studies, 96% participants had OSA (n = 60,840) and 9% had baseline cognitive impairment (mild cognitive impairment [MCI] or AD) (n=5,826). Of all study participants, 43,970 obtained PAP therapy, and 16,400 were untreated or in a placebo group. Nine out of 11 studies reported a protective effect of PAP therapy on MCI and AD incidence, e.g., delayed age at MCI onset, reduced MCI or AD incidence, slower cognitive decline, or progression to AD.

DISCUSSION

These findings suggest a role for OSA as a modifiable risk factor for cognitive decline. Identification of modifiable risk factors is imperative for alleviating the impact of cognitive disorders on aging adults and their family members. Future research should build on this review and focus on PAP interventions as a potential means to alleviate the incidence of cognitive disorders and cognitive decline, particularly among ethnoracial groups who have been underrepresented and underinvestigated in the extant literature.

Adverse driving behaviors are associated with sleep apnea severity and age in cognitively normal older adults at risk for Alzheimer's disease

Alzheimer's disease (AD) pathology accumulates for decades before the onset of cognitive decline. Cognitively normal individuals with biomarker evidence of AD brain pathology (i.e. biomarker + or preclinical AD) can be differentiated from individuals without AD brain pathology based on naturalistic driving data, such as hard acceleration or braking and speeding, measured using in-vehicle dataloggers. Older adults are at increased risk of injury and death from motor vehicle crashes and driving cessation is also linked to negative health outcomes. Identifying potentially modifiable risk factors that increase driving risk may prolong safe driving in old age. Sleep apnea is associated with adverse driving behaviors across the age span. In this study, we hypothesized that high-risk driving behaviors would be associated with increased sleep apnea severity and AD pathology. We found that higher sleep apnea severity measured by a home sleep apnea test was associated with a higher incidence of adverse driving behaviors even after controlling for multiple confounders (β = 0.24 ± 0.09, p < 0.01). This association was independent of AD biomarker positivity (i.e. increased t-tau/Aβ 42 ratio). Increasing age was associated with a higher likelihood of high-risk driving behaviors in individuals with AD brain pathology (β = 0.12 ± 0.04, p < 0.01), but a lower likelihood in individuals without AD brain pathology (β = -0.06 ± 0.03, p < 0.05). These findings suggest that adverse driving behaviors linked to a higher rate of traffic crashes in older adults are associated with sleep apnea severity and AD pathology even in cognitively unimpaired individuals. Further studies are needed to determine if treatment of sleep apnea decreases high-risk driving behaviors and therefore motor vehicle crashes.

Identification of Hub Genes in Patients with Alzheimer Disease and Obstructive Sleep Apnea Syndrome Using Integrated Bioinformatics Analysis

Background

Obstructive sleep apnea syndrome (OSA) is associated with an increased risk of Alzheimer’s disease (AD). This study aimed to identify the key common genes in AD and OSA and explore molecular mechanism value in AD.

Methods

Expression profiles GSE5281 and GSE135917 were acquired from Gene Expression Omnibus (GEO) database, respectively. Weighted gene co-expression network analysis (WGCNA) and R 4.0.2 software were used for identifying differentially expressed genes (DEGs) related to AD and OSA. Function enrichment analyses using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and the protein–protein interaction network (PPI) using the STRING database were subsequently performed on the shared DEGs. Finally, the hub genes were screened from the PPI network using the MCC algorithm of CytoHubba plugin.

Results

Seven modules and four modules were the most significant with AD and OSA by WGCNA, respectively. A total of 33 common genes were screened in AD and OSA by VENN. Functional enrichment analysis indicated that DEGs were mainly involved in cellular response to oxidative stress, neuroinflammation. Among these DEGs, the top 10 hub genes (high scores in cytoHubba) were selected in the PPI network, including AREG, SPP1, CXCL2, ITGAX, DUSP1, COL1A1, SCD, ACTA2, CCND2, ATF3.

Conclusion

This study presented ten target genes on the basis of common genes to AD and OSA. These candidate genes may provide a novel perspective to explore the underlying mechanism that OSA leads to an increased risk of AD at the transcriptome level.

Snoring Remediation with Oral Appliance Therapy Potentially Reverses Cognitive Impairment: An Intervention Controlled Pilot Study

Respiration rate (RR) dynamics entrains brain neural networks. RR differences between mild cognitive impairment (MCI) and Alzheimer’s disease (AD) in response to oral appliance therapy (OAT) are unknown. This pilot study investigated if RR during stable sleep shows a relationship to pathological severity in subjects with MCI and AD who snore and if RR is influenced following stabilization of the upper airway using OAT. The study cohort was as follows: cognitively normal (CN; n = 14), MCI (n = 14) and AD (n = 9); and a sub-population receiving intervention, CN (n = 5), MCI (n = 7), AD (n = 6) subjects. The intervention used was an oral appliance plus a mouth shield (Tx). RR maximum (max) rate (breaths/minute) and RR fluctuation during 2116 stable sleep periods were measured. The Montreal cognitive assessment (MoCA) was administered before and after 4 weeks with Tx. Baseline data showed significantly higher RR fluctuation in CN vs. AD (p < 0.001) but not between CN vs. MCI (p = 0.668). Linear mixed model analysis indicated Tx effect (p = 0.008) for RR max. Tx after 4 weeks lowered the RR-max in MCI (p = 0.022) and AD (p < 0.001). Compared with AD RR max, CN (p < 0.001) and MCI (p < 0.001) were higher with Tx after 4 weeks. Some MCI and AD subjects improved executive and memory function after 4 weeks of Tx.

Cognition effectiveness of continuous positive airway pressure treatment in obstructive sleep apnea syndrome patients with cognitive impairment: a meta-analysis

Obstructive sleep apnea (OSA) is a common respiratory disorder characterized by recurrent pharyngeal collapses during sleep leading to intermittent hypoxia and sleep disruption. Cognitive challenges and high risks of cognitive impairment, including Alzheimer's disease (AD), are closely associated with OSA. Currently, continuous positive airway pressure (CPAP) is widely used in the treatment of OSA. However, whether CPAP benefits cognitive functions in patients with OSA remains elusive. Here, we identified published studies through a systematic review of PubMed, Cochrane Library, Embase, Wanfang Data, CBM, and CNKI from January 1, 1970, to July 1, 2020. 288 patients from 7 articles (one was excluded in the meta-analysis for it was a follow-up study) were included in the present study. It revealed that cognitive functions of OSA patients with mild cognitive impairment (MCI) or AD were mildly but significantly improved after CPAP treatment (SMD 0.49, 95% CI 0.11-0.86), especially long-term CPAP treatment (SMD 0.56, 95% CI 0.10-1.02, p = 0.02), as measured by Mini-Mental State Examination (MMSE) (SMD 0.49, 95%CI 0.11-0.86). However, no significant cognition benefits were detected by the Montreal Cognitive Assessment (SMD 0.43, 95% CI 0.85-1.72). In terms of heterogeneity, cognitive improvements by CPAP were detectable on OSA patients either at a younger age or over longer periods of CPAP treatment. Therefore, our findings highlight the partial efficiency of CPAP treatment in cognition improvement of OSA patients with MCI or AD.

Aberrant waste disposal in neurodegeneration: why improved sleep could be the solution

Sleep takes up a large percentage of our lives and the full functions of this state are still not understood. However, over the last 10 years a new and important function has emerged as a mediator of brain clearance. Removal of toxic metabolites and proteins from the brain parenchyma generated during waking activity and high levels of synaptic processing is critical to normal brain function and only enabled during deep sleep. Understanding of this process is revealing how impaired sleep contributes an important and likely causative role in the accumulation and aggregation of aberrant proteins such as β-amyloid and phosphorylated tau, as well as inflammation and neuronal damage. We are also beginning to understand how brain slow-wave activity interacts with vascular function allowing the flow of CSF and interstitial fluid to drain into the body's lymphatic system. New methodology is enabling visualization of this process in both animals and humans and is revealing how these processes break down during ageing and disease. With this understanding we can begin to envisage novel therapeutic approaches to the treatment of neurodegeneration, and how reversing sleep impairment in the correct manner may provide a way to slow these processes and improve brain function.

Use of positive airway pressure in mild cognitive impairment to delay progression to dementia

STUDY OBJECTIVES

The aim was to assess the relationship between continuous positive airway pressure (CPAP) therapy and cognitive function in patients with mild cognitive impairment (MCI) and obstructive sleep apnea (OSA).

METHODS

This was a retrospective chart review of patients with MCI and OSA. CPAP therapy compliance was defined as average use of CPAP therapy for at least 4 hours per night. Kaplan-Meier estimates, log-rank tests, and Cox proportional hazards regression were done to compare the compliance groups in terms of progression to dementia, defined as a Clinical Dementia Rating of 1 or greater. Linear mixed models were used to assess the relationships between CPAP therapy compliance and neurological cognitive function outcomes over time.

RESULTS

Ninety-six patients were included with mean age at MCI diagnosis of 70.4 years, mean apnea-hypopnea index of 25.9 events/h, and mean duration of neurology follow-up of 2.8 years. Forty-two were CPAP compliant, 30 were noncompliant, and 24 had no CPAP use. No overall difference between the groups was detected for progression to dementia (P = .928, log-rank test). Patients with amnestic MCI had better CPAP use (P = .016) and shorter progression time to dementia (P = .042), but this difference was not significant after adjusting for age, education, and race (P = .32).

CONCLUSIONS

CPAP use in patients with MCI and OSA was not associated with delay in progression to dementia or cognitive decline.

The Importance of Diagnosing and the Clinical Potential of Treating Obstructive Sleep Apnea to Delay Mild Cognitive Impairment and Alzheimer's Disease: A Special Focus on Cognitive Performance

Obstructive sleep apnea (OSA) is a highly frequent sleep disorder in the middle-aged and older population, and it has been associated with an increased risk of developing cognitive decline and dementia, including mild cognitive impairment (MCI) and Alzheimer's disease (AD). In more recent years, a growing number of studies have focused on: 1) the presence of OSA in patients with MCI or AD, 2) the link between OSA and markers of AD pathology, and 3) the role of OSA in accelerating cognitive deterioration in patients with MCI or AD. Moreover, some studies have also assessed the effects of continuous positive airway pressure (CPAP) treatment on the cognitive trajectory in MCI and AD patients with comorbid OSA. This narrative review summarizes the findings of studies that analyzed OSA as a risk factor for developing MCI and/or AD in the middle-aged and older populations with a special focus on cognition. In addition, it describes the results regarding the effects of CPAP treatment in hampering the progressive cognitive decline in AD and delaying the conversion to AD in MCI patients. Considering the importance of identifying and treating OSA in patients with MCI or AD in order to prevent or reduce the progression of cognitive decline, further larger and adequately powered studies are needed both to support these findings and to set programs for the early recognition of OSA in patients with cognitive impairment.

Sleep in Older Adults and Its Possible Relations With COVID-19

Since the beginning of the COVID-19 pandemic, older adults have been found to be a highly vulnerable group, with a higher prevalence of severe cases and negative outcomes. Research has focused on the reasons why older adults are at greater risk; Sleep-related factors have been suggested as one possible explanation for this. An individual's sleep pattern undergoes significant changes over the course of their life. In older adults a specific sleep profile can be observed, one characterized by advanced sleep timing, a morningness preference, longer sleep-onset latency, shorter overall sleep duration, increased sleep fragmentation, reduced slow-wave sleep and, increased wake time after sleep onset. Additionally, an increased prevalence of sleep disorders can be observed, such as obstructive sleep apnea and insomnia. Previous research has already linked sleep disorders (especially sleep apnea) with COVID-19, but few studies have focused specifically on the older population. We believe that the intrinsic sleep patterns of older adults, and the prevalence of sleep disorders in this population, may be important factors that could explain why they are at a greater risk of negative COVID-19 outcomes. In this review, we discuss the relationship between sleep and COVID-19 among older adults, focusing on three different aspects: (1) Sleep-related issues that might increase the likelihood of getting infected by SARS-COV-2; (2) Sleep disturbances that might increase the predisposition to worse COVID-19 prognosis and outcomes; and (3) COVID-19-related aspects affecting community-dwelling older adults, such as social isolation, quarantine, and home confinement, among others, that might impact sleep.

Longitudinal changes in regional cerebral blood flow in late middle-aged and older adults with treated and untreated obstructive sleep apnea

Obstructive sleep apnea (OSA) is associated with abnormal cerebral perfusion at wakefulness, but whether these anomalies evolve over time is unknown. Here, we examined longitudinal changes in regional cerebral blood flow (rCBF) distribution in late middle‐aged and older adults with treated or untreated OSA. Twelve controls (64.8 ± 8.0 years) and 23 participants with newly diagnosed OSA (67.8 ± 6.2 years) were evaluated with polysomnography and cerebral ^99mTc‐HMPAO single‐photon emission computed tomography during wakeful rest. OSA participants were referred to a sleep apnea clinic and 13 of them decided to start continuous positive airway pressure (CPAP). Participants were tested again after 18 months. Voxel‐based analysis and extracted relative rCBF values were used to assess longitudinal changes. Untreated OSA participants showed decreased relative rCBF in the left hippocampus and the right parahippocampal gyrus over time, while treated participants showed trends for increased relative rCBF in the left hippocampus and the right parahippocampal gyrus. No changes were found over time in controls. Untreated OSA is associated with worsening relative rCBF in specific brain areas over time, while treated OSA shows the opposite. Considering that OSA possibly accelerates cognitive decline in older adults, CPAP treatment could help reduce risk for cognitive impairment.

The emerging role of the sigma-1 receptor in autophagy: hand-in-hand targets for the treatment of Alzheimer's

INTRODUCTION

Autophagy is a cellular catabolic mechanism that helps clear damaged cellular components and is essential for normal cellular and tissue function. The sigma-1 receptor (σ-1R) is a chaperone protein involved in signal transduction, neurite outgrowth, and plasticity, improving memory, and neuroprotection. Recent evidence shows that σ-1R can promote autophagy. Autophagy activation by the σ-1Rs along with other neuroprotective effects makes it an interesting target for the treatment of Alzheimer's disease. AF710B, T-817 MA, and ANAVEX2-73 are some of the σ-1R agonists which have shown promising results and have entered clinical trials. These molecules have also been found to induce autophagy and show cytoprotective effects in cellular models.

AREAS COVERED

This review provides insight into the current understanding of σ-1R functions related to autophagy and their role in alleviating AD.

EXPERT OPINION

We propose a mechanism through which the activation of σ-1R and autophagy could alter amyloid precursor protein processing to inhibit amyloid-β production by reconstituting cholesterol and gangliosides in the lipid raft to offer neuroprotection against AD. Future AD treatment could involve the combined targeting of the σ-1R and autophagy activation. We suggest that future studies investigate the link between autophagy the σ-1R and AD.

Alzheimer's disease neuropathology in the hippocampus and brainstem of people with obstructive sleep apnea

Obstructive sleep apnea (OSA) involves intermittent cessations of breathing during sleep. People with OSA can experience memory deficits and have reduced hippocampal volume; these features are also characteristic of Alzheimer's disease (AD), where they are accompanied by neurofibrillary tangles (NFTs) and amyloid beta (Aβ) plaques in the hippocampus and brainstem. We have recently shown reduced hippocampal volume to be related to OSA severity, and although OSA may be a risk factor for AD, the hippocampus and brainstems of clinically verified OSA cases have not yet been examined for NFTs and Aβ plaques. The present study used quantitative immunohistochemistry to investigate postmortem hippocampi of 34 people with OSA (18 females, 16 males; mean age 67 years) and brainstems of 24 people with OSA for the presence of NFTs and Aβ plaques. OSA severity was a significant predictor of Aβ plaque burden in the hippocampus after controlling for age, sex, body mass index (BMI), and continuous positive airway pressure (CPAP) use. OSA severity also predicted NFT burden in the hippocampus, but not after controlling for age. Although 71% of brainstems contained NFTs and 21% contained Aβ plaques, their burdens were not correlated with OSA severity. These results indicate that OSA accounts for some of the "cognitively normal" individuals who have been found to have substantial Aβ burdens, and are currently considered to be at a prodromal stage of AD.

Sleep-Based Interventions in Alzheimer's Disease: Promising Approaches from Prevention to Treatment along the Disease Trajectory

The multifactorial nature of Alzheimer’s disease (AD) has led scientific researchers to focus on the modifiable and treatable risk factors of AD. Sleep fits into this context, given the bidirectional relationship with AD confirmed by several studies over the last years. Sleep disorders appear at an early stage of AD and continue throughout the entire course of the pathology. Specifically, sleep abnormalities, such as more fragmented sleep, increase in time of awakenings, worsening of sleep quality and primary sleep disorders raise with the severity and progression of AD. Intervening on sleep, therefore, means acting both with prevention strategies in the pre-clinical phase and with treatments during the course of the disease. This review explores sleep disturbances in the different stages of AD, starting from the pre-clinical stage. Particular attention is given to the empirical evidence investigating obstructive sleep apnea (OSA) disorder and the mechanisms overlapping and sharing with AD. Next, we discuss sleep-based intervention strategies in the healthy elderly population, mild cognitive impairment (MCI) and AD patients. We mention interventions related to behavioral strategies, combination therapies, and bright light therapy, leaving extensive space for new and raising evidence on continuous positive air pressure (CPAP) treatment effectiveness. Finally, we clarify the role of NREM sleep across the AD trajectory and consider the most recent studies based on the promising results of NREM sleep enhancement, which use innovative experimental designs and techniques.

Obstructive Sleep Apnea and Dementia-Common Gene Associations through Network-Based Identification of Common Driver Genes

Background: Obstructive Sleep Apnea (OSA) occurs in 7% of the adult population. The relationship between neurodegenerative diseases such as dementia and sleep disorders have long attracted clinical attention; however, no comprehensive data exists elucidating common gene expression between the two diseases. The objective of this study was to (1) demonstrate the practicability and feasibility of utilizing a systems biology approach called network-based identification of common driver genes (NICD) to identify common genomic features between two associated diseases and (2) utilize this approach to identify genes associated with both OSA and dementia. Methods: This study utilized 2 public databases (PCNet, DisGeNET) and a permutation assay in order to identify common genes between two co-morbid but mutually exclusive diseases. These genes were then linked to their mechanistic pathways through Enrichr, producing a list of genes that were common between the two different diseases. Results: 42 common genes were identified between OSA and dementia which were primarily linked to the G-coupled protein receptor (GPCR) and olfactory pathways. No single nucleotide polymorphisms (SNPs) were identified. Conclusions: This study demonstrates the viability of using publicly available databases and permutation assays along with canonical pathway linkage to identify common gene drivers as potential mechanistic targets for comorbid diseases.

Top of the morning: best time to teach adults who are cognitively impaired about home sleep apnea testing

Grigg-Damberger MM, Foldvary-Schaefer N. Top of the morning: best time to teach adults who are cognitively impaired about home sleep apnea testing. J Clin Sleep Med. 2021;17(3):365–366.

Obstructive sleep apnea syndrome and Alzheimer's disease pathology: may continuous positive airway pressure treatment delay cognitive deterioration?

PURPOSE

The main aim of the present study was to identify the long-term effects of continuous positive airway pressure (CPAP) treatment in patients co-affected by obstructive sleep apnea syndrome (OSAS) and mild cognitive impairment (MCI) or dementia due to Alzheimer's disease (ADD).

METHODS

This retrospective multicentre study included patients affected by MCI or ADD, diagnosed according to the core clinical and biomarkers criteria, and presenting comorbid OSAS. Only patients performing at least a 1-year visit during their follow-up to monitor cognitive deterioration and adherence with CPAP treatment were included. Both Mini-Mental State Examination (MMSE) and clinical dementia rating scale (CDR) were conducted during the baseline and the follow-up visits.

RESULTS

Twenty-four patients were included in the study and were distributed according to the diagnosis in MCI (n = 8) or ADD (n = 16). There were no significant differences in the variables analysed at baseline between the CPAP non-adherent and CPAP adherent patients. In the whole group, a significant decrease was found in MMSE scores, and a significant increase was found in CDR scores between baseline and follow-up. No longitudinal changes in ESS scores were statistically significant from baseline to follow-up. A significant difference was found for the mean score change of the CDR since CPAP non-adherent patients showed a higher mean change of CDR compared to CPAP adherent patients. No significant differences were found for the mean change of MMSE.

CONCLUSION

These findings highlight the clinical potential of treating OSAS with CPAP to delay cognitive deterioration in patients with MCI or ADD.

Sleep disorders and late-onset epilepsy of unknown origin: Understanding new trajectories to brain amyloidopathy

The intertwining between epilepsy, sleep disorders and beta amyloid pathology has been progressively highlighted, as early identification and stratification of patients at high risk of cognitive decline is the need of the hour. Modification of the sleep-wake activity, such as sleep impairment or excessive daytime sleepiness, can critically affect cerebral beta amyloid levels. Both mice models and human studies have demonstrated a substantial increase in the burden of beta amyloid pathology after sleep-deprivation, with potential negative effects partially restored by sleep recovery. The accumulation of beta amyloid has been shown to be an early event in the course of Alzheimer's disease dementia. Beta amyloid accumulation has been linked to epileptic seizures epileptic seizures, with beta amyloid being itself pro-epileptogenic in mice models already at oligomeric stage, well before plaque deposition. Further supporting a potential relationship between beta amyloid and epilepsy: i) seizures happen in 1 out of oofut 10 patients with Alzheimer's disease in the prodromal stage, ii) epileptic activity accelerates cognitive decline in Alzheimer's disease, iii) people with late-onset epilepsy present a critically high risk of developing dementia. In this Review we highlight the role of beta amyloid as a potential shared mechanisms between sleep disorders, late-onset epilepsy, and cognitive decline.

Association Between Obstructive Sleep Apnea, Its Treatment, and Alzheimer's Disease: Systematic Mini-Review

Obstructive sleep apnea (OSA) and Alzheimer's disease (AD) are common in the elderly population. Obstructive sleep apnea that may cause significant changes in the cerebrospinal fluid β-amyloid and T-tau and/or P-tau protein levels is often identified as a risk factor for development of AD. Although the underlying mechanisms of AD are still not fully understood, a hypothesis associating OSA with AD has been already proposed. In this systematic mini-review, we first discuss the recent findings supporting the association of OSA with an increased risk of AD and then provide evidence suggesting the positive effect of OSA treatment on a reduced risk of AD.

The Treatment of Sleep Dysfunction in Neurodegenerative Disorders

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

Sleep disorders in Alzheimer's disease: the predictive roles and potential mechanisms

Sleep disorders are common in patients with Alzheimer's disease, and can even occur in patients with amnestic mild cognitive impairment, which appears before Alzheimer's disease. Sleep disorders further impair cognitive function and accelerate the accumulation of amyloid-β and tau in patients with Alzheimer's disease. At present, sleep disorders are considered as a risk factor for, and may be a predictor of, Alzheimer's disease development. Given that sleep disorders are encountered in other types of dementia and psychiatric conditions, sleep-related biomarkers to predict Alzheimer's disease need to have high specificity and sensitivity. Here, we summarize the major Alzheimer's disease-specific sleep changes, including abnormal non-rapid eye movement sleep, sleep fragmentation, and sleep-disordered breathing, and describe their ability to predict the onset of Alzheimer's disease at its earliest stages. Understanding the mechanisms underlying these sleep changes is also crucial if we are to clarify the role of sleep in Alzheimer's disease. This paper therefore explores some potential mechanisms that may contribute to sleep disorders, including dysregulation of the orexinergic, glutamatergic, and γ-aminobutyric acid systems and the circadian rhythm, together with amyloid-β accumulation. This review could provide a theoretical basis for the development of drugs to treat Alzheimer's disease based on sleep disorders in future work.

Molecular Mechanisms and Genetics of Oxidative Stress in Alzheimer's Disease

Alzheimer’s disease is the most common neurodegenerative disorder that can cause dementia in elderly over 60 years of age. One of the disease hallmarks is oxidative stress which interconnects with other processes such as amyloid-β deposition, tau hyperphosphorylation, and tangle formation. This review discusses current thoughts on molecular mechanisms that may relate oxidative stress to Alzheimer’s disease and identifies genetic factors observed from in vitro, in vivo, and clinical studies that may be associated with Alzheimer’s disease-related oxidative stress.

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

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

Sleep-disordered breathing and the risk of Alzheimer's disease

Sleep-disordered breathing is highly prevalent in the elderly population. Obstructive sleep apnea (OSA) represents the most common sleep disorder among the adult and elderly population. Recently, OSA diagnosis has been associated with an increased risk of developing cognitive decline and dementia, including vascular dementia and Alzheimer's disease (AD). Subsequently, there have been studies on AD biomarkers investigating cerebrospinal fluid, blood, neuroimaging, and nuclear medicine biomarkers in patients with OSA. Furthermore, studies have attempted to assess the possible effects of continuous positive airway pressure (CPAP) treatment on the cognitive trajectory and AD biomarkers in patients with OSA. This review summarizes the findings of studies on each AD biomarker (cognitive, biofluid, neuroimaging, and nuclear medicine imaging) in patients with OSA, also accounting for the related effects of CPAP treatment. In addition, the hypothetical model connecting OSA to AD in a bi-directional interplay is analyzed. Finally, the sex-based differences in prevalence and clinical symptoms of OSA between men and women have been investigated in relation to AD risk. Further studies investigating AD biomarkers changes in patients with OSA and the effect of CPAP treatment should be auspicated in future for identifying strategies to prevent the development of AD.

Obstructive sleep apnoea and cognitive decline in mild-to-moderate Alzheimer's disease

We evaluated the influence of untreated obstructive sleep apnoea (OSA) on the magnitude of cognitive decline and on several cognitive subdomains in patients with mild-to-moderate Alzheimer's disease.

In this single-centre study, 144 patients were recruited prospectively from a cognitive impairment unit and underwent overnight polysomnography.

The mean±sd change in the Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-cog) score at 12 months was 3.19±5.61 in the non-OSA group and 0.08±5.62 in the OSA group, with an intergroup difference of −3.36 (95% CI 0.19–0.16; p=0.002). We did not observe a significant difference in any cognitive subdomains at 12 months. Regarding Mini-Mental State Examination scores at 36 months, the mean change was 1.69 (95% CI −1.26–4.64; p=0.445). No significant differences were found among different OSA severity groups.

We observed that ADAS-cog scores were better in the OSA group than in the non-OSA group by a statistically but not clinically significant margin. We did not find differences in the different cognitive subdomains after 1 year or in global cognition after 3 years of follow-up.