Sleep breathing disorders and cognitive function in the elderly: an 8-year follow-up study. the proof-synapse cohort

Altered fornix integrity is associated with sleep apnea-related hypoxemia in mild cognitive impairment

INTRODUCTION

The limbic system is critical for memory function and degenerates early in the Alzheimer's disease continuum. Whether obstructive sleep apnea (OSA) is associated with alterations in the limbic white matter tracts remains understudied.

METHODS

Polysomnography, neurocognitive assessment, and brain magnetic resonance imaging (MRI) were performed in 126 individuals aged 55-86 years, including 70 cognitively unimpaired participants and 56 participants with mild cognitive impairment (MCI). OSA measures of interest were the apnea-hypopnea index and composite variables of sleep fragmentation and hypoxemia. Microstructural properties of the cingulum, fornix, and uncinate fasciculus were estimated using free water-corrected diffusion tensor imaging.

RESULTS

Higher levels of OSA-related hypoxemia were associated with higher left fornix diffusivities only in participants with MCI. Microstructure of the other white matter tracts was not associated with OSA measures. Higher left fornix diffusivities correlated with poorer episodic verbal memory.

DISCUSSION

OSA may contribute to fornix damage and memory dysfunction in MCI.

HIGHLIGHTS

Sleep apnea-related hypoxemia was associated with altered fornix integrity in MCI. Altered fornix integrity correlated with poorer memory function. Sleep apnea may contribute to fornix damage and memory dysfunction in MCI.

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.

Associations of baseline obstructive sleep apnea and sleep macroarchitecture with cognitive function after 8 years in middle-aged and older men from a community-based cohort study

Previous prospective studies examining associations of obstructive sleep apnea and sleep macroarchitecture with future cognitive function recruited older participants, many demonstrating baseline cognitive impairment. This study examined obstructive sleep apnea and sleep macroarchitecture predictors of visual attention, processing speed, and executive function after 8 years among younger community-dwelling men. Florey Adelaide Male Ageing Study participants (n = 477) underwent home-based polysomnography, with 157 completing Trail-Making Tests A and B and the Mini-Mental State Examination. Associations of obstructive sleep apnea (apnea-hypopnea index, oxygen desaturation index, and hypoxic burden index) and sleep macroarchitecture (sleep stage percentages and total sleep time) parameters with future cognitive function were examined using regression models adjusted for baseline demographic, biomedical, and behavioural factors, and cognitive task performance. The mean (standard deviation) age of the men at baseline was 58.9 (8.9) years, with severe obstructive sleep apnea (apnea-hypopnea index ≥30 events/h) in 9.6%. The median (interquartile range) follow-up was 8.3 (7.9-8.6) years. A minority of men (14.6%) were cognitively impaired at baseline (Mini-Mental State Examination score <28/30). A higher percentage of light sleep was associated with better Trail-Making Test A performance (B = -0.04, 95% confidence interval [CI] -0.06, -0.01; p = 0.003), whereas higher mean oxygen saturation was associated with worse performance (B = 0.11, 95% CI 0.02, 0.19; p = 0.012). While obstructive sleep apnea and sleep macroarchitecture might predict cognitive decline, future studies should consider arousal events and non-routine hypoxaemia measures, which may show associations with cognitive decline.

Obstructive sleep apnea and cognitive functioning in the older general population: The moderating effect of age, sex, ApoE4, and obesity

Research on the relationship between obstructive sleep apnea and cognitive functioning has yielded conflicting results, particularly in the older population, and moderators of this association have rarely been studied. Here we investigated the cross-sectional association between obstructive sleep apnea and cognitive functioning as well as the moderating effect of age, sex, apolipoprotein E4, and obesity on this association among community-dwelling older people. We analysed data from 496 participants (71.4 ± 4.4 years; 45.6% men) of the HypnoLaus study who underwent polysomnography and a battery of neuropsychological tests. The sample was categorised as no-to-mild obstructive sleep apnea (apnea-hypopnea index 0-14.9/h; reference), moderate obstructive sleep apnea (apnea-hypopnea index 15.0-29.9/h), or severe obstructive sleep apnea (apnea-hypopnea index ≥30/h). Regression and moderation analyses were performed with adjustment for confounders. Apolipoprotein E4 and obesity moderated the association between severe obstructive sleep apnea and processing speed, whereas no moderating effects were found for age and sex. In apolipoprotein E4 carriers only, severe obstructive sleep apnea was associated with lower performance in Stroop condition 1 (B = 3.13, p = 0.024). In obese participants only, severe obstructive sleep apnea was associated with lower performance in Stroop condition 1 (B = 3.02, p = 0.025) and Stroop condition 2 (B = 3.30, p = 0.034). Severe obstructive sleep apnea was also associated with lower executive function in the whole sample according to Stroop condition 3 (B = 3.44, p = 0.020) and Stroop interference score (B = 0.24, p = 0.006). Our findings support associations of severe obstructive sleep apnea (but not moderate obstructive sleep apnea) with lower performance in processing speed and executive function in the older general population. Apolipoprotein E4 and obesity appear to be vulnerability factors that strengthen the association between severe obstructive sleep apnea and lower performance in processing speed.

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.

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).

History of obstructive sleep apnea associated with incident cognitive impairment in white but not black individuals in a US national cohort study

BACKGROUND

We sought to determine if risk for obstructive sleep apnea (OSA), a history of OSA, and/or treatment of OSA has a different association with incident cognitive impairment or cognitive decline in Black individuals and White individuals.

METHODS

To determine whether the risk for OSA, a history of OSA, and/or treatment of OSA has a different association with incident cognitive impairment or cognitive decline in Black individuals and White individuals; data from the REasons for Geographic and Racial Differences in Stroke (REGARDS) was used. Participants that completed the sleep questionnaire module, had baseline cognitive assessment, and at least one cognitive assessment during follow-up were included. Risk of OSA was determined based on Berlin Sleep Questionnaire. History of sleep apnea was determined based on structured interview questions. Optimally treated OSA was defined as treated sleep apnea as at least 4 h of continuous positive airway pressure use per night for ≥5 nights per week.

RESULTS

In 19,017 participants stratified by race, White participants with history of OSA were 1.62 times more likely to have incident cognitive impairment compared to White participants without history of OSA after adjusting for demographic characteristics, history, and lifestyle factors (OR = 1.62, 95% CI = 1.05-2.50, p-value = 0.03). This relationship was not seen in Black participants (OR = 0.92, 95% CI = 0.60-1.43, p-value = 0.72).

DISCUSSION

A previous diagnosis of OSA is associated with incident cognitive impairment in White Americans but not Black Americans. Further investigations are required to determine the mechanism for this difference.

Global Prevalence of Obstructive Sleep Apnea in the Elderly and Related Factors: A Systematic Review and Meta-Analysis Study

PURPOSE

The aims of current meta-analysis was to combine data and statistics on the global prevalence of OSA and related factors in older adults.

DESIGN

A systematic review and meta-analysis.

METHODS

To find related studies, various databases were searched including Embase, PubMed, Scopus, Web of Science (WoS), MagIran, and SID (two local databases) using appropriate keywords, MeSH and controlled vocabulary, with no time limitation up to June, 2021. Heterogeneity of studies was evaluated using I2, and Egger's regression intercept was used to detect publication bias.

FINDINGS

39 studies with a total sample size of 33,353 people were included. The pooled prevalence of OSA in older adults was 35.9% (95% confidence interval: 28.7%-43.8%; I2 = 98.81%). Considering the high heterogeneity of included studies, subgroup analysis was conducted and yielded the most prevalent in Asia continent with 37.0% (95% CI: 22.4%-54.5%; I2 = 97.32%). However, heterogeneity was remained at high level. In the majority of studies, OSA was significantly and positively related to obesity, increased BMI, age, cardiovascular diseases, diabetes, and daytime sleepiness.

CONCLUSIONS

Results of this study showed that global prevalence of OSA in older adults is high and is significantly related to obesity, increased BMI, age, cardiovascular diseases, diabetes, and daytime sleepiness. These findings can be used by experts working on the diagnosis and management of OSA in the geriatric population. These findings can be used by experts on the diagnosis and treatment of OSA in the older adults. Due to high heterogeneity, findings should be interpreted with great caution.

Obstructive sleep apnea and dementia: A role to play?

A growing number of studies, in animal models and humans, have highlighted the link between sleep and Alzheimer's disease (AD) pathophysiology. Among sleep disorders, obstructive sleep apnea (OSA) appears to be a potentially interesting comorbidity, as it is highly prevalent in the middle-aged and elderly population, often associated with some cognitive impairment, associated with an increased risk of developing cognitive decline and dementia including AD, and indeed treatable. The association between OSA and cognition varies according to the studies, but OSA is more frequent in older people with AD than those who are cognitively normal. People with OSA suffer from daytime sleepiness, impaired cognitive function and an increased risk of developing mild cognitive impairment, dementia and AD than those without OSA. Finally, the literature suggests a link between OSA and AD biomarkers. Whether screening and treating OSA could have positive impact on the levels of AD biomarkers and slow or even prevent incident dementia remain to be investigated. It therefore seems essential to understand the role of OSA in the pathophysiology of AD, as there is still no effective treatment to slow or halt its progression. At present, treating the risk factors that can promote the development and/or worsening of AD represents a promising strategy for delaying or even thwarting the onset of symptoms.

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.

Breathing cessation events that compose the apnea-hypopnea index are distinctively associated with the adverse outcomes in Alzheimer's disease

BACKGROUND

Previous studies challenge the impact of obstructive sleep apnea (OSA) once patients are diagnosed with Alzheimer's disease (AD). Nevertheless, OSA recognizably disrupts sleep, and relevant associations between sleep, AD pathological markers, and cognition have been demonstrated. We aimed to further explore this, evaluating the associations between each breathing cessation event that compose the apnea-hypopnea index (AHI) and the sleep structure to finally investigate whether this was related to increased levels of AD markers and higher cognitive decline.

METHODS

Observational, prospective study, including consecutive patients diagnosed with mild-moderate AD. The participants were submitted to overnight polysomnography followed by a cerebrospinal fluid collection for AD pathological markers levels determination. Neuropsychological assessment was performed at baseline and after 12 months of follow-up.

RESULTS

The cohort was composed of 116 patients (55.2% females) with a median [p25;p75] age of 76.0 [72.0;80.0] years and an AHI of 25.9 [15.1;48.5], which was mainly defined by the presence of hypopneas and obstructive apneas. These were distinctively associated with the sleep structure, with obstructive apneas being related to arousals and sleep lightening and hypopneas being related to an increased number of arousals only. Despite having a lower frequency, mixed and central apneas also presented associations with the sleep structure, particularly increasing the time spent in the lighter sleep stages. In relation to AD pathological markers, obstructive and mixed apneas were related to an augment in neurofilament light levels while hypopneas were associated with a higher phosphorylated-tau/amyloid-beta protein ratio. Hypopneas were the most important event for an increased cognitive decline at the 12-month follow-up.

CONCLUSIONS

Our findings highlight the importance of a patient-centered approach, with a comprehensive and detailed analysis of the AHI to effectively predict the different outcomes and tailor the appropriate therapeutic strategies.

Associations of Baseline Sleep Microarchitecture with Cognitive Function After 8 Years in Middle-Aged and Older Men from a Community-Based Cohort Study

Purpose

Prospective studies examining associations between baseline sleep microarchitecture and future cognitive function recruited from small samples with predominantly short follow-up. This study examined sleep microarchitecture predictors of cognitive function (visual attention, processing speed, and executive function) after 8 years in community-dwelling men.

Patients and Methods

Florey Adelaide Male Ageing Study participants (n=477) underwent home-based polysomnography (2010-2011), with 157 completing baseline (2007-2010) and follow-up (2018-2019) cognitive assessments (trail-making tests A [TMT-A] and B [TMT-B] and the standardized mini-mental state examination [SMMSE]). Whole-night F4-M1 sleep EEG recordings were processed following artifact exclusion, and quantitative EEG characteristics were obtained using validated algorithms. Associations between baseline sleep microarchitecture and future cognitive function (visual attention, processing speed, and executive function) were examined using linear regression models adjusted for baseline obstructive sleep apnoea, other risk factors, and cognition.

Results

The final sample included men aged (mean [SD]) 58.9 (8.9) years at baseline, overweight (BMI 28.5 [4.2] kg/m²), and well educated (75.2% ≥Bachelor, Certificate, or Trade), with majorly normal baseline cognition. Median (IQR) follow-up was 8.3 (7.9, 8.6) years. In adjusted analyses, NREM and REM sleep EEG spectral power was not associated with TMT-A, TMT-B, or SMMSE performance (all p>0.05). A significant association of higher N3 sleep fast spindle density with worse TMT-B performance (B=1.06, 95% CI [0.13, 2.00], p=0.026) did not persist following adjustment for baseline TMT-B performance.

Conclusion

In this sample of community-dwelling men, sleep microarchitecture was not independently associated with visual attention, processing speed, or executive function after 8 years.

Daytime Hypercapnia Impairs Working Memory in Young and Middle-Aged Patients with Obstructive Sleep Apnea Hypopnea Syndrome

Purpose

Obstructive sleep apnea hypopnea syndrome (OSAHS) can lead to cognitive impairment, though few studies have so far examined hypercapnia as its causal mechanism, due to the invasive nature of conventional arterial CO2 measurement. The study aims to investigate the effects of daytime hypercapnia on working memory in young and middle-aged patients with OSAHS.

Patients and Methods

This prospective study screened 218 patients and eventually recruited 131 patients (aged 25-60 years) with polysomnography (PSG)-diagnosed OSAHS. Using a cut-off of 45mmHg daytime transcutaneous partial pressure of carbon dioxide (PtcCO2), 86 patients were assigned into the normocapnic group and 45 patients into the hypercapnic group. Working memory was evaluated using the Digit Span Backward Test (DSB) and the Cambridge Neuropsychological Test Automated Battery.

Results

Compared with the normocapnic group, the hypercapnic group performed worse in verbal, visual, and spatial working memory tasks. PtcCO2≥45mmHg was an independent predictor for lower DSB scores (OR=4.057), lower accuracy in the immediate Pattern Recognition Memory (OR=2.600), delayed Pattern Recognition Memory (OR=2.766) and Spatial Recognition Memory (OR=2.722) tasks, lower Spatial Span scores (OR=4.795), and more between errors in the Spatial Working Memory task (OR=2.734 and 2.558, respectively). Notably, PSG indicators of hypoxia and sleep fragmentation did not predict task performance.

Conclusion

Hypercapnia may be plays an important role in working memory impairment in patients with OSAHS, perhaps more so than hypoxia and sleep fragmentation. Routine CO2 monitoring in these patients could prove of utility in clinical practices.

Distinct cognitive changes in male patients with obstructive sleep apnoea without co-morbidities

Introduction

Obstructive sleep apnoea (OSA) is a multisystem, debilitating, chronic disorder of breathing during sleep, resulting in a relatively consistent pattern of cognitive deficits. More recently, it has been argued that those cognitive deficits, especially in middle-aged patients, may be driven by cardiovascular and metabolic comorbidities, rather than by distinct OSA-processes, such as are for example ensuing nocturnal intermittent hypoxaemia, oxidative stress, neuroinflammation, and sleep fragmentation.

Methods

Thus, we undertook to define cognitive performance in a group of 27 middle-aged male patients with untreated OSA, who had no concomitant comorbidities, compared with seven matched controls (AHI mean ± S.D.: 1.9 ± 1.4 events/h; mean age 34.0 ± 9.3 years; mean BMI 23.8 ± 2.3 kg/m2). Of the 27 patients, 16 had mild OSA (AHI mean ± S.D.:11.7 ± 4.0 events/h; mean age 42.6 ± 8.2 years; mean BMI 26.7 ± 4.1 kg/m2), and 11 severe OSA (AHI 41.8 ± 20.7 events/h; age: 46.9 ± 10.9 years, BMI: 28.0 ± 3.2 kg/m2).

Results

In our patient cohort, we demonstrate poorer executive-functioning, visuospatial memory, and deficits in vigilance sustained attention, psychomotor and impulse control. Remarkably, we also report, for the first time, effects on social cognition in this group of male, middle-aged OSA patients.

Conclusion

Our findings suggest that distinct, OSA-driven processes may be sufficient for cognitive changes to occur as early as in middle age, in otherwise healthy individuals.

Gender-specific association between obstructive sleep apnea and cognitive impairment among adults

OBJECTIVES

This study aims to explore the gender-specific association between obstructive sleep apnea (OSA) and cognitive impairment.

METHODS

Participants from UK biobank who have completed at least one of the five baseline cognitive tests (visuospatial memory, prospective memory, fluid intelligence, short numeric memory and reaction time) were included, which were initially divided into two groups based on gender and were further categorized into three subgroups: (1) OSA, (2) self-reported snoring but without OSA, and (3) healthy controls (without OSA or snoring). Multivariable regression analysis was performed to examine the associations among snoring, OSA and performance of each of the five cognitive domains.

RESULTS

A total of 267,889 participants (47% male, mean age: 57 years old) were included in our study. In the multivariable regression analysis, female participants in the OSA group had a higher risk of having poor prospective memory (OR: 1.24, 95% CI: 1.02～1.50, p = 0.03). Meanwhile, among female participants, OSA were inversely associated with the performances of fluid intelligence (β: 0.29, 95% CI: 0.46～-0.13, p &lt; 0.001) and short-numeric memory (β: 0.14, 95% CI: 0.35～0.08, p = 0.02). Besides, age-related subgroup analyses showed that these associations were largely reserved in younger (＜65 years old) female participants rather than older (≥65 years old) female participants. In contrast, among male participants, no significant association was observed between OSA and impairment of the five cognitive domains.

CONCLUSIONS

OSA was significantly associated with cognitive impairment at certain dimensions in female participants rather than in male participants, indicating that more special attention and timely interventions should be given to younger female OSA patients to prevent further cognitive impairment.

The Link between Obstructive Sleep Apnea and Neurocognitive Impairment: An Official American Thoracic Society Workshop Report

There is emerging evidence that obstructive sleep apnea (OSA) is a risk factor for preclinical Alzheimer's disease (AD). An American Thoracic Society workshop was convened that included clinicians, basic scientists, and epidemiologists with expertise in OSA, cognition, and dementia, with the overall objectives of summarizing the state of knowledge in the field, identifying important research gaps, and identifying potential directions for future research. Although currently available cognitive screening tests may allow for identification of cognitive impairment in patients with OSA, they should be interpreted with caution. Neuroimaging in OSA can provide surrogate measures of disease chronicity, but it has methodological limitations. Most data on the impact of OSA treatment on cognition are for continuous positive airway pressure (CPAP), with limited data for other treatments. The cognitive domains improving with CPAP show considerable heterogeneity across studies. OSA can negatively influence risk, manifestations, and possibly progression of AD and other forms of dementia. Sleep-dependent memory tasks need greater incorporation into OSA testing, with better delineation of sleep fragmentation versus intermittent hypoxia effects. Plasma biomarkers may prove to be sensitive, feasible, and scalable biomarkers for use in clinical trials. There is strong biological plausibility, but insufficient data, to prove bidirectional causality of the associations between OSA and aging pathology. Engaging, recruiting, and retaining diverse populations in health care and research may help to decrease racial and ethnic disparities in OSA and AD. Key recommendations from the workshop include research aimed at underlying mechanisms; longer-term longitudinal studies with objective assessment of OSA, sensitive cognitive markers, and sleep-dependent cognitive tasks; and pragmatic study designs for interventional studies that control for other factors that may impact cognitive outcomes and use novel biomarkers.

Effect of Sleep Disturbance on Cognitive Function in Elderly Individuals: A Prospective Cohort Study

Many epidemiologic and clinical studies have shown significant links between the degree of sleep disturbance and severity of impairment of selective cognitive functions, including the risk of neurodegenerative diseases. However, the sleep parameters that affect cognitive function in old age are unclear. Therefore, we investigated the association between sleep parameters and cognitive function in older patients. Patients aged above 65 years who complained of sleep-disordered breathing were enrolled consecutively. The Mini-Mental-State Examination tool was used to evaluate cognitive function. Eighty patients (normal cognitive function, n = 32 and cognitive impairment, n = 42) were included in this study. Multiple linear regression and binary logistic regression analyses were performed to explain the relationship between sleep parameters and cognitive function. We found that the body mass index (BMI) was significantly lower in the cognitive impairment group than in the normal cognitive function group. Additionally, the cognitive impairment group showed significantly decreased sleep efficiency and an increased apnea index compared with normal subjects. Moreover, lower BMI, reduced sleep efficiency, and high frequency of apnea events during sleep were associated with an increased risk of cognitive impairment.

Sleep and Cognition: A Narrative Review Focused on Older Adults

Little is known regarding sleep's association with the traditional developmental course of late-life cognitive functioning. As the number of older adults increases worldwide, an enhanced understanding of age-related changes in sleep and cognition is necessary to slow decline and promote optimal aging. This review synthesizes the extant literature on sleep and cognitive function in healthy older adults, older adults with insomnia, and older adults with sleep apnea, incorporating information on the potential promising effects of treating poor sleep on cognitive outcomes in older adults. Unifying theories of the sleep-cognition association, possible mechanisms of action, and important unanswered questions are identified.

A New Berlin Questionnaire Simplified by Machine Learning Techniques in a Population of Italian Healthcare Workers to Highlight the Suspicion of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) syndrome is a condition characterized by the presence of repeated complete or partial collapse of the upper airways during sleep associated with episodes of intermittent hypoxia, leading to fragmentation of sleep, sympathetic nervous system activation, and oxidative stress. To date, one of the major aims of research is to find out a simplified non-invasive screening system for this still underdiagnosed disease. The Berlin questionnaire (BQ) is the most widely used questionnaire for OSA and is a beneficial screening tool devised to select subjects with a high likelihood of having OSA. We administered the original ten-question Berlin questionnaire, enriched with a set of questions purposely prepared by our team and completing the socio-demographic, clinical, and anamnestic picture, to a sample of Italian professional nurses in order to investigate the possible impact of OSA disease on healthcare systems. According to the Berlin questionnaire, respondents were categorized as high-risk and low-risk of having OSA. For both risk groups, baseline characteristics, work information, clinical factors, and symptoms were assessed. Anthropometric data, work information, health status, and symptoms were significantly different between OSA high-risk and low-risk groups. Through supervised feature selection and Machine Learning, we also reduced the original BQ to a very limited set of items which seem capable of reproducing the outcome of the full BQ: this reduced group of questions may be useful to determine the risk of sleep apnea in screening cases where questionnaire compilation time must be kept as short as possible.

Sleep apnoea in the elderly: a great challenge for the future

Due in part to overall improvements in health, the population of elderly individuals is increasing rapidly. Similarly, obstructive sleep apnoea (OSA) is both gaining increased recognition and also increasing due to the worldwide obesity epidemic. The overlap of OSA and aging is large, but there is strong plausibility for causation in both directions: OSA is associated with pathological processes that may accelerate aging and aging related processes; aging may cause physical and neurological changes that predispose to obstructive (and central) apnoea. In addition, the common symptoms (e.g. excessive daytime somnolence, defects in memory and cognition), possible physiological consequences of OSA (e.g. accelerated cardiovascular and cerebrovascular atherosclerosis), and changes in metabolic and inflammatory markers overlap with the symptoms and associated conditions seen in aging. There is also the possibility of synergy in the effects of these symptoms and conditions on quality of life, as well as a need to separate treatable consequences of OSA from age-related complaints. Taken together, the above make it essential to review the interaction of OSA and aging, both proven and suspected. The present review examines some aspects of what is known and points to the need for further investigation of the relationships, given the large number of potentially affected subjects.

Obstructive Sleep Apnea, Hypercoagulability, and the Blood-Brain Barrier

Obstructive sleep apnea (OSA) is characterized by repeated episodes of intermittent hypoxia (IH) and is recognized as an independent risk factor for vascular diseases that are mediated by a multitude of mechanistic pathophysiological cascades including procoagulant factors. The pro-coagulant state contributes to the development of blood clots and to the increase in the permeability of the blood-brain barrier (BBB). Such alteration of BBB may alter brain function and increase the risk of neurodegenerative diseases. We aim to provide a narrative review of the relationship between the hypercoagulable state, observed in OSA and characterized by increased coagulation factor activity, as well as platelet activation, and the underlying neural dysfunction, as related to disruption of the BBB. We aim to provide a critical overview of the existing evidence about the effect of OSA on the coagulation balance (characterized by increased coagulation factor activity and platelet activation) as on the BBB. Then, we will present the emerging data on the effect of BBB disruption on the risk of underlying neural dysfunction. Finally, we will discuss the potential of OSA therapy on the coagulation balance and the improvement of BBB.

Feasibility of unattended home sleep apnea testing in a cognitively impaired clinic population

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) increases the risk of developing dementia. Home sleep apnea testing (HSAT) is a convenient and validated method to screen for OSA among cognitively well individuals; however, it is unknown if it is a clinically feasible and practical approach in clinic patients with cognitive impairment. We evaluated if HSAT was a feasible and practical approach to screen for OSA in clinic patients with cognitive impairment.

METHODS

Patients with cognitive impairment due to neurodegenerative and/or vascular etiologies completed OSA screening using HSAT. HSAT was considered a feasible technique if ≥ 80% of those who attempted HSAT obtained analyzable data (ie, ≥ 4 hours of flow, effort, and oxygen evaluation), and a practical technique if ≥ 50% of all patients approached for study inclusion obtained analyzable data.

RESULTS

Of the 119 patients who were approached for participation, 83 were enrolled and offered HSAT; 5 did not complete HSAT screening, and the remaining 78 patients attempted HSAT; mean age (± standard deviation) of 72.86 (± 9.89) years and 46% were male. In those that attempted HSAT, 85.9% (67/78) obtained analyzable data and 56.3% (67/119) of eligible patients approached for study inclusion obtained analyzable data.

CONCLUSIONS

HSAT is a feasible and practical technique in a clinic population with cognitive impairment. As OSA is a modifiable risk factor for patients with dementia, HSAT has the potential to lead to expedited treatment for OSA, which may potentially improve health-related outcomes such as cognition.

Obstructive Sleep Apnea and Cognitive Decline: A Review of Potential Vulnerability and Protective Factors

Around 40% of dementia risk is attributable to modifiable risk factors such as physical inactivity, hypertension, diabetes and obesity. Recently, sleep disorders, including obstructive sleep apnea (OSA), have also been considered among these factors. However, despite several epidemiological studies investigating the link between OSA and cognitive decline, there is still no consensus on whether OSA increases the risk of dementia or not. Part of the heterogeneity observed in previous studies might be related to some individual characteristics that modulate the association between OSA and cognitive decline. In this narrative review, we present these individual characteristics, namely, age, sex, menopause, obesity, diabetes mellitus, hypertension, cardiovascular diseases, smoking, excessive alcohol consumption, depression, air pollution, Apolipoprotein E ε4 allele, physical activity, and cognitive reserve. To date, large cohort studies of OSA and cognitive decline tended to statistically control for the effects of these variables, but whether they interact with OSA to predict cognitive decline remains to be elucidated. Being able to better predict who is at risk of cognitive decline when they have OSA would improve clinical management and treatment decisions, particularly when patients present relatively mild OSA.

Cell-Selective Altered Cargo Properties of Extracellular Vesicles Following In Vitro Exposures to Intermittent Hypoxia

Intermittent hypoxia (IH), a hallmark of obstructive sleep apnea (OSA), is associated with cardiovascular and metabolic dysfunction. However, the mechanisms underlying these morbidities remain poorly delineated. Extracellular vesicles (EVs) mediate intercellular communications, play pivotal roles in a multitude of physiological and pathological processes, and could mediate IH-induced cellular effects. Here, the effects of IH on human primary cells and the release of EVs were examined. Microvascular endothelial cells (HMVEC-d), THP1 monocytes, THP1 macrophages M0, THP1 macrophages M1, THP1 macrophages M2, pre-adipocytes, and differentiated adipocytes (HAd) were exposed to either room air (RA) or IH for 24 h. Secreted EVs were isolated and characterized using transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. The effects of each of the cell-derived EVs on endothelial cell (EC) monolayer barrier integrity, on naïve THP1 macrophage polarity, and on adipocyte insulin sensitivity were also evaluated. IH did not alter EVs cell quantal release, but IH-EVs derived from HMVEC-d (p < 0.01), THP1 M0 (p < 0.01) and HAd (p < 0.05) significantly disrupted HMVEC-d monolayer integrity, particularly after H₂O₂ pre-conditioning. IH-EVs from HMVEC-d and THP1 M0 elicited M2-polarity changes did not alter insulin sensitivity responses. IH induces cell-selective changes in EVs cargo, which primarily seem to target the emergence of endothelial dysfunction. Thus, changes in EVs cargo from selected cell sources in vivo may play causal roles in some of the adverse outcomes associated with OSA.

Socioeconomic disparities in obstructive sleep apnea: a systematic review of empirical research

BACKGROUND

Considering socioeconomic status (SES) in the diagnosis of obstructive sleep apnea (OSA) will enhance our understanding of socioeconomic disparities in clinical practice of sleep medicine. This systematic review analyzes the relations between SES and OSA measures.

METHODOLOGY

Eleven articles were identified through the Pubmed database. The National Institute of Health's Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies was used to rate the quality of these studies.

RESULTS

This systematic review revealed that associations between socioeconomic status and OSA measures are similar for both adults, children, and adolescents. Our findings showed that: (1) A lower SES is associated with an increased risk of OSA, both in adults and children/adolescents as well as for men and women. (2) Several studies assessed sleep outcomes with a single question, an approach that is unable to capture the multi-dimensionality and day-to-day variability of sleep in general or OSA in particular, (3) Low SES has detrimental effects on sleep health. (4) Sleep questionnaires are more commonly used than objective measure to assess OSA.

CONCLUSIONS

Interaction between SES and OSA must be better understood to improve current clinical guidelines. Living conditions influence the trajectory of OSA with unknown speed and for an, undetermined period, pointing to the need for more studies on this topic. Future work should identify the effect of SES on the development and progression of OSA, determine the effect of behavioral intervention and local public health programs to reduce social inequalities associated with OSA.

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.

A contemporary review of obstructive sleep apnea

PURPOSE OF REVIEW

This review provides a contemporary review of sleep apnea with emphasis on definitions, epidemiology, and consequences.

RECENT FINDINGS

Amyloid β-42 is one of the main peptides forming amyloid plaques in the brains of Alzheimer patients. Poorer sleep quality and shorter sleep duration have been associated with a higher amyloid burden. Decreased sleep time in the elderly is a precipitating factor in amyloid retention. Studies have shown that the dysregulation of the homeostatic balance of the major inhibitory and excitatory amino acid neurotransmitter systems of gamma-aminobutyric acid (GABA) and glutamate play a role in sleep disordered breathing (SDB).

SUMMARY

Untreated sleep disordered breathing (obstructive sleep apnea and/or central sleep apnea) are an important cause of medical mortality and morbidity. OSA is characterized by recurrent episodes of partial or complete collapse of the upper airway during sleep followed by hypoxia and sympathetic activation. Apneic events are terminated by arousal, followed by increases in pulse and blood pressure, and re-oxygenation and the release of inflammatory factors. Individuals with OSA have an increased risk of developing atrial fibrillation. Hypoxemia and poor sleep quality because of OSA increase the risk of cognitive decline in the elderly.

Risk factors of excessive daytime sleepiness in a prospective population-based cohort

Although excessive daytime sleepiness is commonly evaluated in clinical and research settings using the Epworth Sleepiness Scale, few studies have assessed the factors associated with its incidence in the general population. We prospectively investigated the predictors of incident and persistent excessive daytime sleepiness in 2,751 subjects (46.1% men, mean age 56.0 ± 9.8 years) from the CoLaus-PsyCoLaus population-based cohort (Lausanne, Switzerland) over 5 years. Participants completed the Epworth Sleepiness Scale and the Pittsburgh Sleep Quality Index, and underwent a full clinical evaluation at baseline and 5 years afterwards. Ambulatory polysomnography was performed at baseline in a sub-sample of 1,404 subjects. Among the 2,438 subjects without excessive daytime sleepiness (Epworth Sleepiness Scale ≤ 10) at baseline, the 5-year incidence of excessive daytime sleepiness was 5.1% (n = 124). Multivariate logistic regression revealed that male sex, depressive symptoms, reported poor sleep quality and moderate to severe obstructive sleep apnea were independent predictors of incident excessive daytime sleepiness, while older age, moderate coffee consumption, periodic leg movement during sleep and hypertension were independent protective factors. Stratified analysis according to sex and age showed some distinctive associations. Among the 313 patients with excessive daytime sleepiness at baseline, 137 (43.8%) had persistent excessive daytime sleepiness 5 years later. Our findings provide new insights into the predictors of incident excessive daytime sleepiness, but interventional studies are needed to understand the impact of treating these risk factors on the incidence of excessive daytime sleepiness.

Witnessed apneas are associated with elevated tau-PET levels in cognitively unimpaired elderly

OBJECTIVE

To assess whether informant-reported apneas during sleep (witnessed apneas) in cognitively unimpaired (CU) elderly persons are associated with higher levels of brain tau.

METHODS

From the population-based Mayo Clinic Study of Aging, we identified 292 CU elderly ≥65 years of age with both AV-1451 tau-PET and Pittsburgh compound B (PiB)-PET scans and whose bed partners and close relatives had completed a questionnaire that assessed whether participants had witnessed apneas during sleep. For this cross-sectional analysis, we selected the entorhinal and inferior temporal cortices as our regions of interest (ROIs) because they are highly susceptible to tau accumulation. PET signal was scaled to the cerebellum crus to calculate standardized uptake value ratio (SUVR). We fit linear models to assess the association between regional tau and witnessed apneas while controlling for age, sex, years of education, body mass index, hypertension, hyperlipidemia, diabetes, reduced sleep, excessive daytime sleepiness, and global PiB.

RESULTS

Forty-three participants (14.7%) were found to have witnessed apneas during sleep. The report of witnessed apneas was associated with higher tau-PET SUVR elevation in our ROIs: 0.049 SUVR (95% confidence interval [CI] 0.010-0.087, p = 0.015) in the entorhinal cortex and 0.037 SUVR (95% CI 0.006-0.067, p = 0.019) in the inferior temporal cortex after controlling for confounders.

CONCLUSION

We identified a significant association between witnessed apneas in CU elderly and elevated tau-PET signal in tau-susceptible brain regions. These results suggest a plausible mechanism that could contribute to cognitive impairment and the development of Alzheimer disease. Longitudinal observations are necessary to determine direction of causality.

Sleep Apnea Syndrome in an Elderly Population Admitted to a Geriatric Unit: Prevalence and Effect on Cognitive Function

Background

Sleep apnea leads to cognitive impairment in older patients, but its association with neurodegeneration remains controversial, and most studies do not distinguish between the more common obstructive form (OSAS) and the rarer central form (CSAS).

Objective

The purpose of this study was to assess the prevalence of the different forms of sleep apnea in a cohort of cognitively impaired elderly patients (>70 years) and to investigate their associations with cognitive deficit, weighted against known risk factors for neurodegeneration.

Methods

Overnight polygraphy was performed for 76 consecutive patients admitted to our geriatric unit. Their cognitive function was assessed using the Mini Mental-State Exam (MMSE), Mattis Dementia Rating Scale (MDRS) and Stroop test. Multivariable analyses were performed to determine associations between cognitive function and independent variables describing demographics, sleep apnea measures, and cardiovascular risk factors.

Results

The cohort comprised 58 women and 18 men aged a mean of 84 years (range, 73-96). Sleep apnea syndrome (SAS) was diagnosed in 48 patients (63%), of which 31 (41%) with OSAS and 17 (22%) with CSAS. Multivariable regression analysis revealed that MDRS was lower in patients with OSAS (β = -10.03, p = 0.018), that Stroop Colors and Words delays increased with AHI (β = 0.17, p = 0.030 and β = 0.31, p = 0.047) and that that Stroop Interference delay was higher in patients with CSAS (β = 24.45, p = 0.002).

Conclusion

Sleep apnea is thus highly prevalent in elderly patients with cognitive impairment. OSAS was associated with lower general cognitive function, while CSAS was only associated with increased Stroop Interference delays. Elderly patients with cognitive deficit could benefit from sleep apnea screening and treatment.

Topological Regularization of Networks in Adult Patients with Moderate-to-Severe Obstructive Sleep Apnea-Hypopnea Syndrome: A Structural MRI Study

OBJECTIVE

Patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) exhibit neurocognitive impairments; however, the neuroimaging mechanism of neurocognitive impairments remains unclear. The aim of this study was to understand the neuroimaging mechanism in adult patients with moderate-to-severe OSAHS, from the perspective of the connectome.

PATIENTS AND METHODS

Thirty-one untreated patients with moderate-to-severe OSAHS (mean age: 41.23±8.22) were compared with 26 good sleepers (GS) (mean age: 39.50±7.92) matched according to age, gender, handedness, and education level. All subjects underwent thin-slice T1WI scanning of the skull using a 3.0T MRI. Then, a large-scale structural covariance network was constructed based on the gray matter volume extracted from the structural MRI. Graph theory was then used to determine the topological changes in the structural covariance network of OSAHS patients.

RESULTS

Although small-world networks were retained,the structural covariance network exhibited topological irregularities in regular architecture as evidenced by an increase in the clustering coefficient (p=0.009), transfer coefficient (p=0.029) and local efficiency (p=0.031), and a local increase in the shortest path length (p<0.05) compared with the GS group. Locally, OSAHS patients showed a decrease in nodal betweenness and degree in the left inferior parietal gyrus, left angular gyrus and right anterior cingulate cortex compared with the GS group (p<0.05, uncorrected). In addition, the resistance of structural covariance networks in OSAHS patients to random fault is significantly lower than that of the GS group (p=0.044).

CONCLUSION

Structural covariance networks are abnormal in terms of multiple network parameters, which provide network-level insight into the neuroimaging mechanism of cognitive impairments in adult OSAHS patients.

Obstructive sleep apnea, cognition and Alzheimer's disease: A systematic review integrating three decades of multidisciplinary research

Increasing evidence links cognitive-decline and Alzheimer's disease (AD) to various sleep disorders, including obstructive sleep apnea (OSA). With increasing age, there are substantial differences in OSA's prevalence, associated comorbidities and phenotypic presentation. An important question for sleep and AD researchers is whether OSA's heterogeneity results in varying cognitive-outcomes in older-adults compared to middle-aged adults. In this review, we systematically integrated research examining OSA and cognition, mild cognitive-impairment (MCI) and AD/AD biomarkers; including the effects of continuous positive airway pressure (CPAP) treatment, particularly focusing on characterizing the heterogeneity of OSA and its cognitive-outcomes. Broadly, in middle-aged adults, OSA is often associated with mild impairment in attention, memory and executive function. In older-adults, OSA is not associated with any particular pattern of cognitive-impairment at cross-section; however, OSA is associated with the development of MCI or AD with symptomatic patients who have a higher likelihood of associated disturbed sleep/cognitive-impairment driving these findings. CPAP treatment may be effective in improving cognition in OSA patients with AD. Recent trends demonstrate links between OSA and AD-biomarkers of neurodegeneration across all age-groups. These distinct patterns provide the foundation for envisioning better characterization of OSA and the need for more sensitive/novel sleep-dependent cognitive assessments to assess OSA-related cognitive-impairment.

Cognitive impairment in heart failure is associated with altered Wnt signaling in the hippocampus

Age represents the highest risk factor for death due to cardiovascular disease. Heart failure (HF) is the most common cardiovascular disease in elder population and it is associated with cognitive impairment (CI), diminishing learning and memory process affecting life quality and mortality in these patients. In HF, CI has been associated with inadequate O₂ supply to the brain; however, an important subset of HF patients displays CI with almost no alteration in cerebral blood flow. Importantly, nothing is known about the pathophysiological mechanisms underpinning CI in HF with no change in brain tissue perfusion. Here, we aimed to study memory performance and learning function in a rodent model of HF that shows no change in blood flow going to the brain. We found that HF rats presented learning impairments and memory loss. In addition, HF rats displayed a decreased level of Wnt/β-catenin signaling downstream elements in the hippocampus, one pathway implicated largely in aging diseases. Taken together, our results suggest that in HF rats CI is associated with dysfunction of the Wnt/β-catenin signaling pathway. The mechanisms involved in the alterations of Wnt/β-catenin signaling in HF and its contribution to the development/maintenance of CI deserves future investigations.

Task Difficulty Modulates the Disrupting Effects of Oral Respiration on Visual Search Performance

Previous research has suggested that oral respiration may disturb cognitive function and health. The present study investigated whether oral respiration negatively affects visual attentional processing during a visual search task. Participants performed a visual search task in the following three breathing conditions: wearing a nasal plug, wearing surgical tape over their mouths, or no modification (oral vs. nasal vs. control). The participants searched for a target stimulus within different set sizes of distractors in three search conditions (orientation vs colour vs conjunction). Experiment 1 did not show any effect due to respiration. Experiment 2 rigorously manipulated the search efficiency and found that participants required more time to find a poorly discriminable target during oral breathing compared with other breathing styles, which was due to the heightened intercept under this condition. Because the intercept is an index of pre-search sensory processing or motor response in visual search, such cognitive processing was likely disrupted by oral respiration. These results suggest that oral respiration and attentional processing during inefficient visual search share a common cognitive resource.

Role of Obstructive Sleep Apnea in Cognitive Impairment

Obstructive sleep apnea (OSA) is a prevalent sleep related breathing disorder characterized by repetitive collapse of the upper airways leading to intermittent hypoxia and sleep disruption. Clinically relevant neurocognitive, metabolic and cardiovascular disease often occurs in OSA. Systemic hypertension, coronary artery disease, type 2 diabetes mellitus, cerebral vascular infarctions and atrial fibrillation are among the most often cited conditions with causal connections to OSA. Emerging science suggest that untreated and undertreated OSA increases the risk of developing cognitive impairment, including vascular dementia and neurodegenerative disorders, like Alzheimer’s disease. As with OSA, cardiovascular disease and type 2 diabetes mellitus, the incidence of dementia increases with age. Given our rapidly aging population, dementia prevalence will significantly increase. The aim of this treatise is to review current literature linking OSA to dementia and explore putative mechanisms by which OSA might facilitate the development and progression of dementia.

Sleep-disordered breathing and Alzheimer's disease: A nationwide cohort study

Sleep-disordered breathing (SDB) is common and can lead to significant cognitive decline, such as Alzheimer's disease (AD). Therefore, the present study was conducted to investigate whether SDB is associated with AD onset. This study used the nationwide health check-up cohort data between 2002 and 2015. The study population comprised individuals who were diagnosed with SDB and those without SDB who were matched by using propensity score. The matched cohort was followed up until the onset of AD, death, or end of 2015. A multivariate Cox proportional hazard model was used in the analysis. There were 727 (16.7%) patients in the SDB group between 2002 and 2005 and 3635 subjects (83.3%) in the propensity score-matched non-SDB group. After adjusting for the possible confounding variables, patients with SDB were almost 1.58 times more likely to develop AD than those without SDB (hazard ratio [HR] = 1.575, 95% confidence interval [CI] = 1.013-2.448). The present study showed that SDB was associated with an onset of AD. The findings of this study highlight the importance of the interventions to raise awareness of SDB and the need for the government's support to reduce the barrier in accessing appropriate SDB treatment.

The effect of aging on drug-induced sleep endoscopy findings

OBJECTIVES/HYPOTHESIS

To evaluate the correlation of aging and upper airway collapse characteristics observed by drug-induced sleep endoscopy (DISE), and report the observed differences on obstructive sleep apnea (OSA) subjects, older and younger than 60 years.

STUDY DESIGN

Case series.

METHODS

This study analyzed the data of 200 OSA patients who underwent DISE between January 1, 2013 and June 30, 2017. The variables sex, body mass index (BMI), Epworth Sleepiness Scale score, tonsil size, modified Mallampati (MM) classification, apnea-hypopnea index (AHI), oxygen desaturation index (ODI), lowest oxygen saturation, and VOTE (velum, oropharynx, tongue base, epiglottis) classification were compared between two groups: <60 and ≥60 years old.

RESULTS

Older age had significant correlation with higher AHI, ODI, lower O₂ nadir, multisite obstruction, combined upper (palatopharyngeal) + lower (hypopharyngeal) level obstructions, and complete anterior-posterior (AP) velum collapse pattern. Lateral oropharyngeal wall collapse was significantly lower in the older group. Findings remained statistically significant when adjusted for sex, BMI, tonsil size, and MM.

CONCLUSIONS

Aging was an independent factor that directly correlated with increased AHI and hypoxemia, multisites, combined levels of obstruction, and complete AP velum collapse pattern. Being older than 60 years had higher of complete AP velum collapse and lower incidence of lateral oropharyngeal wall collapse, regardless of OSA severity and tonsil size.

LEVEL OF EVIDENCE

4 Laryngoscope, 2644-2650, 2018.

Greater Cognitive Deficits with Sleep-disordered Breathing among Individuals with Genetic Susceptibility to Alzheimer Disease. The Multi-Ethnic Study of Atherosclerosis

RATIONALE

There are conflicting findings regarding the link between sleep apnea and cognitive dysfunction.

OBJECTIVES

Investigate associations between indicators of sleep-disordered breathing (SDB) and cognitive function in the Multi-Ethnic Study of Atherosclerosis and assess effect modification by the apolipoprotein ε-4 (APOE-ε4) allele.

METHODS

A diverse population (N = 1,752) underwent type 2 in-home polysomnography, which included measurement of percentage sleep time less than 90% oxyhemoglobin saturation (%Sat < 90%) and apnea-hypopnea index (AHI). Epworth Sleepiness Scale score (ESS) and sleep apnea syndrome (SAS; AHI ≥ 5 and ESS > 10) were also analyzed. Cognitive outcomes included the Cognitive Abilities Screening Instrument; Digit Symbol Coding (DSC) test; and Digit Span Tests (DST) Forward and Backward.

RESULTS

Participants were 45.4% men, aged 68.1 years (SD, 9.1 yr) with a median AHI of 9.0 and mean ESS of 6.0. Approximately 9.7% had SAS, and 26.8% had at least one copy of the APOE-ε4 allele. In adjusted analyses, a 1-SD increase in %Sat < 90% and ESS score were associated with a poorer attention and memory assessed by the DST Forward score (β = -0.12 [SE, 0.06] and β = -0.13 [SE, 0.06], respectively; P ≤ 0.05). SAS and higher ESS scores were also associated with poorer attention and processing speed as measured by the DSC (β = -0.69 [SE, 0.35] and β = -1.42 [SE, 0.35], respectively; P < 0.05). The presence of APOE-ε4 allele modified the associations of %Sat < 90% with DST forward and of ESS with DSC (P_interaction ≤ 0.05).

CONCLUSIONS

Overnight hypoxemia and sleepiness were associated with cognition. The average effect estimates were small, similar to effect estimates for several other individual dementia risk factors. Associations were strongest in APOE-ε4 risk allele carriers. Our results (1) suggest that SDB be considered among a group of modifiable dementia risk factors, and (2) highlight the potential vulnerability of APOE-ε4 risk allele carriers with SDB.

Sleep-disordered breathing, brain volume, and cognition in older individuals with heart failure

BACKGROUND AND PURPOSE

Sleep-disordered breathing is common in individuals with heart failure and may contribute to changes in the brain and decreased cognition. However, limited research has explored how the apnea-hypopnea index contributes to brain structure and cognition in this population. The aims of this study were to explore how the apnea-hypopnea index is associated with brain volume and cognition in heart failure patients.

METHODS

Data of 28 heart failure patients (mean age = 67.93; SD = 5.78) were analyzed for this cross-sectional observational study. We evaluated the apnea-hypopnea index using a portable multichannel sleep-monitoring device. All participants were scanned using 3.0 Tesla magnetic resonance imaging and neuropsychological tests. Brain volume was evaluated using a voxel-based morphometry method with T1-weighted images. We used multiple regressions to analyze how the apnea-hypopnea index is associated with brain volume and cognition.

RESULTS

We found an inverse association between apnea-hypopnea index scores and white matter volume (β = -0.002, p = 0.026), but not in gray matter volume (β = -0.001, p = 0.237). Higher apnea-hypopnea index was associated with reduced regional gray and white matter volume (p < 0.001, uncorrected). Cognitive scores were not associated with the apnea-hypopnea index (p-values were >0.05).

CONCLUSION

Findings from this study provide exploratory evidence that higher apnea-hypopnea index may be associated with greater brain volume reduction in heart failure patients. Future studies are needed to establish the relationship between sleep-disordered breathing, brain volume, and cognition in heart failure samples.

Obstructive Sleep Apnea Severity Affects Amyloid Burden in Cognitively Normal Elderly. A Longitudinal Study

RATIONALE

Recent evidence suggests that obstructive sleep apnea (OSA) may be a risk factor for developing mild cognitive impairment and Alzheimer's disease. However, how sleep apnea affects longitudinal risk for Alzheimer's disease is less well understood.

OBJECTIVES

To test the hypothesis that there is an association between severity of OSA and longitudinal increase in amyloid burden in cognitively normal elderly.

METHODS

Data were derived from a 2-year prospective longitudinal study that sampled community-dwelling healthy cognitively normal elderly. Subjects were healthy volunteers between the ages of 55 and 90, were nondepressed, and had a consensus clinical diagnosis of cognitively normal. Cerebrospinal fluid amyloid β was measured using ELISA. Subjects received Pittsburgh compound B positron emission tomography scans following standardized procedures. Monitoring of OSA was completed using a home sleep recording device.

MEASUREMENTS AND MAIN RESULTS

We found that severity of OSA indices (AHIall [F1,88 = 4.26; P < 0.05] and AHI4% [F1,87 = 4.36; P < 0.05]) were associated with annual rate of change of cerebrospinal fluid amyloid β42 using linear regression after adjusting for age, sex, body mass index, and apolipoprotein E4 status. AHIall and AHI4% were not associated with increases in ADPiB-mask (Alzheimer's disease vulnerable regions of interest Pittsburg compound B positron emission tomography mask) most likely because of the small sample size, although there was a trend for AHIall (F1,28 = 2.96, P = 0.09; and F1,28 = 2.32, not significant, respectively).

CONCLUSIONS

In a sample of cognitively normal elderly, OSA was associated with markers of increased amyloid burden over the 2-year follow-up. Sleep fragmentation and/or intermittent hypoxia from OSA are likely candidate mechanisms. If confirmed, clinical interventions for OSA may be useful in preventing amyloid build-up in cognitively normal elderly.

Sleep and Cognition in Older Adults

Increased age is associated with normative declines in both sleep and cognitive functioning. Although there are some inconsistencies in the literature, negative sleep changes are associated with worse cognitive functioning. This negative relationship holds true across normal-sleeping older adults, older adults with insomnia, older adults with sleep disordered breathing, cognitively healthy older adults, and older adults with dementia. There are mixed results regarding potential benefits of sleep treatments on cognitive functions; however, this line of research deserves added attention because the potential mechanisms of action are likely distinct from other interventions to improve cognition.

Apnea in Older Adults

Sleep-disordered breathing (SDB) is a highly prevalent chronic disease in older adults. A growing body of evidence demonstrates that SDB in older adults is linked to many adverse cardiovascular, neurocognitive, and metabolic sequelae. However, several unanswered questions remain regarding the diagnosis, consequences, and treatment of SDB in older adults. This review presents the current evidence pertaining to the management of SDB in older adults and identifies crucial gaps in knowledge that need further investigation.

The Study of Neurocognitive Outcomes, Radiological and Retinal Effects of Aspirin in Sleep Apnoea- rationale and methodology of the SNORE-ASA study

PURPOSE

Sleep disordered breathing (SDB) is highly prevalent in older adults. Increasing evidence links SDB to the risk of dementia, mediated via a number of pathways, some of which may be attenuated by low-dose aspirin. This study will evaluate, in a healthy older cohort, the prospective relationship between SDB and cognitive function, changes in retinal and cerebral microvasculature, and determine whether low-dose aspirin ameliorates the effects of SDB on these outcomes over 3years.

DESIGN

SNORE-ASA is a sub-study of the ASPirin in Reducing Events in the Elderly (ASPREE) randomised, multi-centre, placebo-controlled trial evaluating the effect of daily 100mg aspirin on disability-free and dementia-free survival in the healthy older adult aged 70 and over. At baseline, 1400 ASPREE participants successfully underwent a home sleep study with a home sleep study screening device for SDB; and 296 underwent both 1.5 Tesla brain magnetic resonance imaging (MRI) and retinal vascular imaging (RVI). Cognitive testing, brain MRI and RVI is being repeated after 3years.

PRIMARY OUTCOME MEASURES

Change in the modified mini-mental state examination score. Secondary outcome measures are changes in other cognitive tests, and changes in abnormal parameters on RVI and volume of white matter hyper-intensities on brain MRI.

CONCLUSION

Identifying preventive therapies for delaying the onset of dementia is of paramount importance. The results of this study will help clarify the impact of the SDB on risk of cognitive decline and cerebral small vessel disease, and whether low-dose aspirin can ameliorate cognitive decline in the setting of SDB.

SNORE-ASA TRIAL REGISTRATION

ACTRN12612000891820: The Principal ASPREE study is registered with the International Standardized Randomized Controlled Trials Register, ASPirin in Reducing Events in the Elderly, Number: ISRCTN83772183 and clinicaltrials.gov Number NCT01038583.

Association of Sleep-Disordered Breathing With Cognitive Function and Risk of Cognitive Impairment: A Systematic Review and Meta-analysis

Importance

Growing evidence suggests an association between sleep-disordered breathing (SDB) and cognitive decline in elderly persons. However, results from population-based studies have been conflicting, possibly owing to different methods to assess SDB or cognitive domains, making it difficult to draw conclusions on this association.

Objective

To provide a quantitative synthesis of population-based studies on the relationship between SDB and risk of cognitive impairment.

Data Sources

PubMed, EMBASE, and PsychINFO were systematically searched to identify peer-reviewed articles published in English before January 2017 that reported on the association between SDB and cognitive function.

Study Selection

We included cross-sectional and prospective studies with at least 200 participants with a mean participant age of 40 years or older.

Data Extraction and Synthesis

Data were extracted independently by 2 investigators. We extracted and pooled adjusted risk ratios from prospective studies and standard mean differences from cross-sectional studies, using random-effect models. This meta-analysis followed the PRISMA guidelines and also adhered to the MOOSE guidelines.

Main Outcomes and Measures

Cognitive outcomes were based on standard tests or diagnosis of cognitive impairment. Sleep-disordered breathing was ascertained by apnea-hypopnea index or clinical diagnosis.

Results

We included 14 studies, 6 of which were prospective, covering a total of 4 288 419 men and women. Pooled analysis of the 6 prospective studies indicated that those with SDB were 26% (risk ratio, 1.26; 95% CI, 1.05-1.50) more likely to develop cognitive impairment, with no evidence of publication bias but significant heterogeneity between studies. After removing 1 study that introduced significant heterogeneity, the pooled risk ratio was 1.35 (95% CI, 1.11-1.65). Pooled analysis of the 7 cross-sectional studies suggested that those with SDB had slightly worse executive function (standard mean difference, -0.05; 95% CI, -0.09 to 0.00), with no evidence of heterogeneity or publication bias. Sleep-disordered breathing was not associated with global cognition or memory.

Conclusions and Relevance

Sleep-disordered breathing is associated with an increased risk of cognitive impairment and a small worsening in executive function. Further studies are required to determine the mechanisms linking these common conditions and whether treatment of SDB might reduce risk of cognitive impairment.

An innovative intermittent hypoxia model for cell cultures allowing fast Po2 oscillations with minimal gas consumption

Performing hypoxia-reoxygenation cycles in cell culture with a cycle duration accurately reflecting what occurs in obstructive sleep apnea (OSA) patients is a difficult but crucial technical challenge. Our goal was to develop a novel device to expose multiple cell culture dishes to intermittent hypoxia (IH) cycles relevant to OSA with limited gas consumption. With gas flows as low as 200 ml/min, our combination of plate holders with gas-permeable cultureware generates rapid normoxia-hypoxia cycles. Cycles alternating 1 min at 20% O2 followed by 1 min at 2% O2 resulted in Po2 values ranging from 124 to 44 mmHg. Extending hypoxic and normoxic phases to 10 min allowed Po2 variations from 120 to 25 mmHg. The volume of culture medium or the presence of cells only modestly affected the Po2 variations. In contrast, the nadir of the hypoxia phase increased when measured at different heights above the membrane. We validated the physiological relevance of this model by showing that hypoxia inducible factor-1α expression was significantly increased by IH exposure in human aortic endothelial cells, murine breast carcinoma (4T1) cells as well as in a blood-brain barrier model (2.5-, 1.5-, and 6-fold increases, respectively). In conclusion, we have established a new device to perform rapid intermittent hypoxia cycles in cell cultures, with minimal gas consumption and the possibility to expose several culture dishes simultaneously. This device will allow functional studies of the consequences of IH and deciphering of the molecular biology of IH at the cellular level using oxygen cycles that are clinically relevant to OSA.