Obstructive sleep apnea and cognitive impairment: addressing the blood-brain barrier

Microstructural Changes in the Cerebral White Matter After 12 Months of CPAP Treatment for Moderate to Severe Obstructive Sleep Apnoea: A TBSS Study

Introduction

Continuous positive airway pressure (CPAP) therapy improves clinical symptoms in patients with obstructive sleep apnea (OSA); however, the mechanism of this clinical improvement and how it may be associated with the restoration of white matter (WM) structures in the brain is unclear. Therefore, this study investigated the relationship between the structural recovery of brain WM and improvements in cognitive function and emotion after long-term (12 months) CPAP treatment in patients with OSA.

Methods

We collected data from 17 patients with OSA before and 12 months after CPAP treatment, including sleep monitoring, clinical assessment, and diffusion tensor imaging (DTI) magnetic resonance imaging.

Results

We observed a partial reversible recovery of brain WM (mean and radial diffusion coefficients) after treatment. This recovery involved the commissural fibers (cingulum, body of corpus callosum), projection fibers (retrolenticular part of the internal capsule, posterior thalamic radiation, posterior limb of the internal capsule, superior corona radiata, posterior corona radiata), association fibers (external capsule, superior longitudinal fasciculus, inferior longitudinal fasciculus), and other regions. In addition, the improvements in WM fibers in one part of the brain significantly were correlated with the Hamilton Anxiety Scale and Hamilton Depression Scale scores.

Discussion

Our results suggest that reversible recovery of reduced brain WM integrity due to OSA may require longer CPAP treatment. Moreover, changes in the integrity of the commissural fibers were associated with emotion regulation. These restored WM areas may explain the cognitive and mood improvements observed after OSA treatment.

Predicting the impact of CPAP on brain health: A study using the sleep EEG-derived brain age index

OBJECTIVE

This longitudinal study investigated potential positive impact of CPAP treatment on brain health in individuals with obstructive sleep Apnea (OSA). To allow this, we aimed to employ sleep electroencephalogram (EEG)-derived brain age index (BAI) to quantify CPAP's impact on brain health and identify individually varying CPAP effects on brain aging using machine learning approaches.

METHODS

We retrospectively analyzed CPAP-treated (n = 98) and untreated OSA patients (n = 88) with a minimum 12-month follow-up of polysomnography. BAI was calculated by subtracting chronological age from the predicted brain age. To investigate BAI changes before and after CPAP treatment, we compared annual ΔBAI between CPAP-treated and untreated OSA patients. To identify individually varying CPAP effectiveness and factors influencing CPAP effectiveness, machine learning approaches were employed to predict which patient displayed positive outcomes (negative annual ΔBAI) based on their baseline clinical features.

RESULTS

CPAP-treated group showed lower annual ΔBAI than untreated (-0.6 ± 2.7 vs. 0.3 ± 2.6 years, p < 0.05). This BAI reduction with CPAP was reproduced independently in the Apnea, Bariatric surgery, and CPAP study cohort. Patients with more severe OSA at baseline displayed more positive annual ΔBAI (=accelerated brain aging) when untreated and displayed more negative annual ΔBAI (=decelerated brain aging) when CPAP-treated. Machine learning models achieved high accuracy (up to 86%) in predicting CPAP outcomes.

INTERPRETATION

CPAP treatment can alleviate brain aging in OSA, especially in severe cases. Sleep EEG-derived BAI has potential to assess CPAP's impact on brain health. The study provides insights into CPAP's effects and underscores BAI-based predictive modeling's utility in OSA management.

Early Increase in Blood-Brain Barrier Permeability in a Murine Model Exposed to Fifteen Days of Intermittent Hypoxia

Obstructive sleep apnea (OSA) is characterized by intermittent repeated episodes of hypoxia-reoxygenation. OSA is associated with cerebrovascular consequences. An enhanced blood-brain barrier (BBB) permeability has been proposed as a marker of those disorders. We studied in mice the effects of 1 day and 15 days intermittent hypoxia (IH) exposure on BBB function. We focused on the dorsal part of the hippocampus and attempted to identify the molecular mechanisms by combining in vivo BBB permeability (Evans blue tests) and mRNA expression of several junction proteins (zona occludens (ZO-1,2,3), VE-cadherin, claudins (1,5,12), cingulin) and of aquaporins (1,4,9) on hippocampal brain tissues. After 15 days of IH exposure we observed an increase in BBB permeability, associated with increased mRNA expressions of claudins 1 and 12, aquaporins 1 and 9. IH seemed to increase early for claudin-1 mRNA expression as it doubled with 1 day of exposure and returned near to its base level after 15 days. Claudin-1 overexpression may represent an immediate response to IH exposure. Then, after 15 days of exposure, an increase in functional BBB permeability was associated with enhanced expression of aquaporin. These BBB alterations are possibly associated with a vasogenic oedema that may affect brain functions and accelerate neurodegenerative processes.

Association of CLDN molecules with sleep apnea hypopnea syndrome: new biomarker candidates

Introduction

Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder, and has become a serious threat to public health. Intermittent hypoxia caused by OSA results in a low-grade inflammatory response that leads to impaired mucosal barrier function. Claudin (CLDN) molecules are important for the permeability of the mucosal epithelium. This study aimed to explore whether CLDN molecules can be a potential biomarker of OSA.

Methods

A total of 37 healthy controls and 40 OSA patients underwent a physical assessment for OSA and filled out the STOP-Bang Questionnaire (SBQ) and Epworth Sleepiness Scale (ESS). Clinical specimens of plasma and urine were obtained to observe the difference between OSA patients and healthy controls and diagnostic accuracy of CLDN molecules for OSA.

Results

CLDN1, CLDN2, and CLDN3 molecules in plasma and urine decreased in OSA patients (both p < 0.05). The areas under the receiver operating characteristic curve (AUCs) of urinary CLDN1, plasma CLDN1, urinary CLDN2, plasma CLDN2, urinary CLDN3, and plasma CLDN3 were 0.887, 0.724, 0.779, 0.676, 0.828, and 0.665, respectively. The AUC of urinary CLDN1 + CLDN2 + CLDN3 was 0.906 (95% confidence interval (CI), 0.831-0.981). The AUC of plasma CLDN1 + CLDN2 + CLDN3 was 0.776 (95% CI, 0.645-0.878). The AUC of urinary CLDN3 + SBQ was 0.899 (95% CI, 0.832-0.967). The AUC of urinary CLDN3 + ESS was 0.896 (95% CI, 0.826-0.966). In addition, Urinary CLDN-3 was negative associated with the severity of OSA.

Conclusion

CLDN molecules are promising as useful biomarkers for OSA, which may be related to the impaired barrier function related to OSA.

TDP43/HDAC6/Prdx1 signaling pathway participated in the cognitive impairment of obstructive sleep apnea via regulating inflammation and oxidative stress

Neuroinflammation and oxidative stress induced by intermittent hypoxia (IH) are associated with cognitive dysfunction in patients with obstructive sleep apnea (OSA). Recently, TAR DNA-binding protein 43 (TDP-43), histone deacetylase 6 (HDAC6), and peroxiredoxin 1 (Prdx1) have been reported to be involved in cognitive impairment in many degenerative diseases; however, the underlying mechanisms remain unclear. In the present study, subjects underwent polysomnography to diagnose OSA. Cognitive function was evaluated using the Montreal Cognitive Assessment (MoCA) and peripheral blood samples were collected. HMC3 cells were treated with lipopolysaccharide (LPS) to mimic in vitro neuroinflammation. Western blotting was used to assess protein expression and ELISA to assess inflammation and oxidative stress levels. Participants were divided into three groups: healthy control (n = 20); mild to moderate OSA (n = 20); and severe OSA (n = 20). The MoCA scores in mild-moderate OSA and severe OSA were lower than those in healthy controls. Continuous positive airway pressure therapy was found to be effective for cognitive impairment in subjects with severe OSA (24.70 ± 1.81). Expression of TDP-43 and HDAC6 was increased in subjects with OSA, whereas Prdx1 expression was decreased. Alterations in these proteins were partially reversed after 12 weeks of CPAP treatment. Protein expression of TDP-43 and HDAC6 was negatively correlated with MoCA scores in patients with OSA, while Prdx1 expression exhibited the opposite trend. In LPS-treated HMC3 cells, TDP-43 and HDAC6 were upregulated, whereas Prdx1 expression was reduced. TDP-43 influenced the expression of Prdx1 by regulating HDAC6, and inflammation and oxidative stress varied with the expression of TDP-43. When a specific inhibitor of HDAC6 was used, LPS-induced inflammation and oxidative stress were alleviated by an elevated level of Prdx1. In summary, findings of the present study suggest that TDP-43 influenced Prdx1 by regulating HDAC6 expression and promoting neuroinflammation and oxidative stress. This process may be involved in the cognitive impairment experienced by patients with OSA and may provide potential therapeutic targets.

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).

Obstructive sleep apnea in Parkinson's disease: A prevalent, clinically relevant and treatable feature

Parkinson's disease (PD) is a chronic neurodegenerative disease characterized by motor and non-motor symptoms, including obstructive sleep apnea (OSA), a common comorbid sleep disorder. The prevalence of OSA in PD is high, and its impact on quality of life, accident risk, and limited treatment options underscores the need for vigilant monitoring and effective interventions. OSA is observed in 20-70% of PD patients, whereas the general population exhibits a lower prevalence ranging from 2 to 14%. These discrepancies in prevalence may be attributed to differences in demographic characteristics, sample sizes with selection bias, and variations in scoring systems for apnea and hypopnea events used across different studies. This review highlights the potential pathogenesis of comorbid OSA in PD and provides an overview of ongoing clinical trials investigating interventions for this condition. Several mechanisms have been implicated in the development of OSA in PD, including intermittent hypoxemia, sleep fragmentation, alterations in the glymphatic system homeostasis, upper airway obstruction, and inflammation. Given the adverse effects of PD comorbid OSA, early intervention measures are crucial. It is imperative to conduct longitudinal studies and clinical trials to elucidate the pathogenesis and develop novel and effective interventions for OSA in PD patients. These efforts aim to delay the progression of PD, enhance patients' quality of life, and alleviate the burden on society and families.

Cognitive Impairments, Neuroinflammation and Blood-Brain Barrier Permeability in Mice Exposed to Chronic Sleep Fragmentation during the Daylight Period

Obstructive sleep apnea (OSA) is a chronic condition characterized by intermittent hypoxia (IH) and sleep fragmentation (SF). In murine models, chronic SF can impair endothelial function and induce cognitive declines. These deficits are likely mediated, at least in part, by alterations in Blood-brain barrier (BBB) integrity. Male C57Bl/6J mice were randomly assigned to SF or sleep control (SC) conditions for 4 or 9 weeks and in a subset 2 or 6 weeks of normal sleep recovery. The presence of inflammation and microglia activation were evaluated. Explicit memory function was assessed with the novel object recognition (NOR) test, while BBB permeability was determined by systemic dextran-4kDA-FITC injection and Claudin 5 expression. SF exposures resulted in decreased NOR performance and in increased inflammatory markers and microglial activation, as well as enhanced BBB permeability. Explicit memory and BBB permeability were significantly associated. BBB permeability remained elevated after 2 weeks of sleep recovery (p < 0.01) and returned to baseline values only after 6 weeks. Chronic SF exposures mimicking the fragmentation of sleep that characterizes patients with OSA elicits evidence of inflammation in brain regions and explicit memory impairments in mice. Similarly, SF is also associated with increased BBB permeability, the magnitude of which is closely associated with cognitive functional losses. Despite the normalization of sleep patterns, BBB functional recovery is a protracted process that merits further investigation.

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.

Association between objective sleep measures and cognitive performance: a cross-sectional analysis in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) study

Sleep disturbances often co-exist, which challenges our understanding of their potential impact on cognition. We explored the cross-sectional associations of insomnia and objective measures of sleep with cognitive performance in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) study stratified by middle-aged and older adults. Participants aged ≥55 years underwent cognitive evaluations, polygraphy for 1 night, and actigraphy for 7 days. Insomnia was evaluated using the Clinical Interview Scheduled Revised. Obstructive sleep apnea (OSA) and short sleep duration (SSD) were defined by an apnea-hypopnea index (AHI) of ≥15 events/h and <6 h/ night, respectively. In 703 participants (mean [SD] age 62 [6] years, 44% men), cognition was evaluated using a 10-word list, verbal fluency, and trail-making tests. The frequencies of insomnia, SSD, and OSA were 11%, 24%, and 33%, respectively. In all, 4% had comorbid OSA and insomnia, and 11% had both OSA and SSD. Higher wake after sleep onset (β = -0.004, 95% confidence interval [CI] -0.008, -0.001) and the number of awakenings (β = -0.006, 95% CI -0.012, -0.001) were associated with worse verbal fluency performance. Compared to those without insomnia, older participants with insomnia had worse global performance (β = -0.354, 95% CI -0.671, -0.038). Insomnia was an effect modifier in the associations between AHI and executive function performance (p for the interaction between insomnia and AHI = 0.004) and between oxygen saturation <90% and memory performance (p for the interaction between insomnia and oxygen saturation = 0.02). Although some associations between sleep measures and cognition were significant, they should be considered with caution due to the large sample size and multiple testing performed in this study.

Sensitivity to remifentanil and its predictive factor in male patients with moderate to severe obstructive sleep apnea syndrome

OBJECTIVES

Obstructive sleep apnea syndrome (OSAS) is associated with increased risk of postoperative complications, which is possibly related to increased sensitivity to opioid. However, the effect of increased sensitivity to opioids in patients with OSAS remains controversial. This study aims to investigate whether male patients with moderate to severe OSAS have increased sensitivity to opioid remifentanil and its related predictive factors, so as to provide a reference for the rational use of opioids in patients with OSAS.

METHODS

This study was a prospective study. From December 28, 2021 to October 15, 2022, a total of 61 male patients aged 22 to 60 years old, American Society of Anesthesiologists (ASA) status I and II, who underwent nasopharyngeal surgery under general anesthesia, were selected. According to STOP-BANG questionnaire score and apnea-hypopnea index (AHI), the patients were divided into an OSAS group (n=39) and a control group (n=22). The pupil diameter (PD) of the patients was measured by hand-held monocular pupillometer, and the perception threshold (PT) and pain tolerance threshold (PTT) of the patients were measured by somatosensory evoked potential stimulator. The initial PD, PT, and PTT were measured in a quiet environment and recorded as PD0, PT0, and PTT0. Changes in PD, PT, PTT, respiration, and consciousness were recorded after remifentanil infusion. Age, body mass index (BMI), smoking, AHI, minimal oxygen saturation, and percentage of sleep time spent with oxygen saturation <90% (T90) were included as independent variables in multiple linear regression equations to analyze the possible predictors of increased opioid sensitivity in patients with moderate to severe OSAS.

RESULTS

There were no significant differences in PD0, PT0 and PTT0 between the OSAS group and the control group (all P>0.05). After remifentanil infusion, there was no significant difference in the rate of PT change between the 2 groups (P>0.05). The change rate of PTT and PD in the OSAS group was significantly higher than that in the control group (P<0.05 and P<0.001, respectively), PD in the OSAS group was significantly lower than that in the control group (P<0.001). During remifentanil infusion, there were no significant differences in the incidence of respiratory depression and the distribution of observer's assessment of alertness/sedation (OAA/S) scores between the 2 groups (both P>0.05), and there were no changes in mental status and airway support in the patients of the 2 groups. Multiple linear regression showed that T90 was positively correlated with miosis rate (β=0.597, 95% CI 0.269 to 0.924, P<0.05) and the rate of PTT change (β=0.458, 95% CI 0.116 to 0.800, P<0.05). However, minimal oxygen saturation, age, BMI, smoking, and AHI were not correlated with PD change rate and PTT change rate in the OSAS patients (all P>0.05).

CONCLUSIONS

Male patients with moderate to severe OSAS have increased sensitivity to remifentanil, the duration of nocturnal desaturation may be its predictive factor. Male patients with moderate to severe OSAS with a longer duration of nocturnal hypoxia are more sensitive to remifentanil, and the use of opioids in these patients should be more cautious in clinical.

Loss of Blood-Brain Barrier Integrity in an In Vitro Model Subjected to Intermittent Hypoxia: Is Reversion Possible with a HIF-1α Pathway Inhibitor?

Several sleep-related breathing disorders provoke repeated hypoxia stresses, which potentially lead to neurological diseases, such as cognitive impairment. Nevertheless, consequences of repeated intermittent hypoxia on the blood-brain barrier (BBB) are less recognized. This study compared two methods of intermittent hypoxia induction on the cerebral endothelium of the BBB: one using hydralazine and the other using a hypoxia chamber. These cycles were performed on an endothelial cell and astrocyte coculture model. Na-Fl permeability, tight junction protein, and ABC transporters (P-gp and MRP-1) content were evaluated with or without HIF-1 inhibitors YC-1. Our results demonstrated that hydralazine as well as intermittent physical hypoxia progressively altered BBB integrity, as shown by an increase in Na-Fl permeability. This alteration was accompanied by a decrease in concentration of tight junction proteins ZO-1 and claudin-5. In turn, microvascular endothelial cells up-regulated the expression of P-gp and MRP-1. An alteration was also found under hydralazine after the third cycle. On the other hand, the third intermittent hypoxia exposure showed a preservation of BBB characteristics. Furthermore, inhibition of HIF-1α with YC-1 prevented BBB dysfunction after hydralazine treatment. In the case of physical intermittent hypoxia, we observed an incomplete reversion suggesting that other biological mechanisms may be involved in BBB dysfunction. In conclusion, intermittent hypoxia led to an alteration of the BBB model with an adaptation observed after the third cycle.

The Putative Role of Neuroinflammation in the Interaction between Traumatic Brain Injuries, Sleep, Pain and Other Neuropsychiatric Outcomes: A State-of-the-Art Review

Sleep disturbances are widely prevalent following a traumatic brain injury (TBI) and have the potential to contribute to numerous post-traumatic physiological, psychological, and cognitive difficulties developing chronically, including chronic pain. An important pathophysiological mechanism involved in the recovery of TBI is neuroinflammation, which leads to many downstream consequences. While neuroinflammation is a process that can be both beneficial and detrimental to individuals' recovery after sustaining a TBI, recent evidence suggests that neuroinflammation may worsen outcomes in traumatically injured patients, as well as exacerbate the deleterious consequences of sleep disturbances. Additionally, a bidirectional relationship between neuroinflammation and sleep has been described, where neuroinflammation plays a role in sleep regulation and, in turn, poor sleep promotes neuroinflammation. Given the complexity of this interplay, this review aims to clarify the role of neuroinflammation in the relationship between sleep and TBI, with an emphasis on long-term outcomes such as pain, mood disorders, cognitive dysfunctions, and elevated risk of Alzheimer's disease and dementia. In addition, some management strategies and novel treatment targeting sleep and neuroinflammation will be discussed in order to establish an effective approach to mitigate long-term outcomes after TBI.

Complement activation mainly mediates the association of heart rate variability and cognitive impairment in adults with obstructive sleep apnea without dementia

STUDY OBJECTIVES

The relationship between autonomic nervous system dysfunction measured by heart rate variability (HRV) and cognitive impairment in obstructive sleep apnea (OSA) patients is complex and still not well understood. We aimed to analyze the role of complement activation, Alzheimer's disease (AD) biomarkers, and white matter hyperintensity (WMH) in modulating the association of HRV with cognitive performance.

METHODS

There were 199 subjects without dementia, including 42 healthy controls, 80 OSA patients with mild cognitive impairment (MCI), and 77 OSA patients without cognitive impairment. All participants who completed polysomnography, cognition, WMH volume, and 5-min HRV analysis were recorded during wakefulness and sleep periods. Neuron-derived exosome and astrocyte-derived exosome proteins were measured by ELISA kits.

RESULTS

The OSA with MCI group were associated with a lower mean of standard deviations of R-R intervals for 5-min intervals (SDANN index) during wakefulness, standard deviation of the R-R interval (SDNN) during sleep stage and percentage of adjacent R-R intervals differing by more than 50 ms (PNN50) in each stage compared with OSA without MCI. The influence of HRV on cognition was partially mediated by complement activation (C5b-9 mediated a maximum of 51.21%), AD biomarkers, and WMH.

CONCLUSIONS

Lower SDANN index and PNN50 during wakefulness and SDNN and PNN50 during sleep periods were found in OSA patients with MCI, suggesting potential vulnerability to autonomic and parasympathetic dysfunction. Complement activation, AD biomarkers, and WMH might partially mediate and interact with the influence of HRV on cognitive impairment in OSA patients.

CLINICAL TRIAL REGISTRATION

ChiCTR1900021544.

Elevated complement component 8 gamma levels in astrocyte-derived exosomes are associated with cognitive impairment in obstructive sleep apnea patients without dementia

The complement system plays a crucial role in cognitive impairment in obstructive sleep apnea (OSA). The present study aimed to investigate the connections between complement component 8 gamma (C8G) levels in astrocyte-derived exosomes (ADEs) and cognitive impairment in OSA patients without dementia. This cross-sectional cohort study recruited 274 participants without dementia, including 124 OSA patients with mild cognitive impairment (MCI), 100 OSA patients without MCI, and 50 healthy control subjects. Enrolled participants underwent polysomnography (PSG) evaluation, neuropsychological scale assessment, magnetic resonance imaging scanning, and collection of peripheral blood samples for quantification of complement proteins in ADEs. The findings showed higher C8G concentrations in ADEs from OSA patients with MCI than in the controls and OSA without MCI group. Logistic regression analysis suggested that C8G levels in ADEs were independently associated with MCI in OSA patients. Multivariable linear regression analysis demonstrated that C8G levels in ADEs were significantly correlated with global cognitive scores and all cognitive subdomain scores after adjusting for demographic factors (age, sex, education), vascular risk factors (Body mass index, history of hypertension, diabetes, dyslipidemia), depressive symptoms measures, and apnea-hypopnea index (AHI) values. The levels of C8G were linearly positively related to the white matter hyperintensity (WMH) volumes in Pearson's correlation analysis. Our research confirmed that C8G levels are significantly associated with cognitive impairment in OSA patients, which paves the way for novel therapeutic targets for neurocognitive dysfunction progression in OSA patients in the future.

Intricate role of sleep deprivation in modulating depression: focusing on BDNF, VEGF, serotonin, cortisol, and TNF-α

In this review article, we aimed to discuss intricate roles of SD in modulating depression in preclinical and clinical studies. Decades of research have shown the inconsistent effects of SD on depression, focusing on SD duration. However, inconsistent role of SD seems to be more complicated, and SD duration cannot be the only one factor. Regarding this issue, we chose some important factors involved in the effects of SD on cognitive functions and mood including brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), serotonin, cortisol, and tumor necrosis factor-alpha (TNF-α). It was concluded that SD has a wide-range of inconsistent effects on BDNF, VEGF, serotonin, and cortisol levels. It was noted that BDNF diurnal rhythm is significantly involved in the modulatory role of SD in depression. Furthermore, the important role of VEGF in blood-brain barrier permeability which is involved in modulating depression was discussed. It was also noted that there is a negative correlation between cortisol and BDNF that modulates depression. Eventually, it was concluded that TNF-α regulates sleep/wake cycle and is involved in the vulnerability to cognitive and behavioral impairments following SD. TNF-α also increases the permeability of the blood-brain barrier which is accompanied by depressive behavior. In sum, it was suggested that future studies should focus on these mechanisms/factors to better investigate the reasons behind intricate roles of SD in modulating depression.

Paroxysmal slow wave events are associated with cognitive impairment in patients with obstructive sleep apnea

BACKGROUND

Increasing evidence has supported a link between obstructive sleep apnea (OSA) and cognition, and blood-brain barrier (BBB) dysfunction which can be reflected by paroxysmal slow wave events (PSWEs) may be a potential mechanism. The purpose of our study was to investigate the correlation between the PSWEs and cognitive impairment in patients with OSA, with a focus on the possible mechanism.

METHODS

In total, 339 subjects with subjective snoring complaints from the Sleep Medicine Center underwent magnetic resonance imaging and whole-night polysomnography. OSA was defined as apnea-hypopnea index (AHI) ≥ 5 events/h. MCI was defined as the MoCA < 26 and met the criteria: (1) subjective cognitive impairment; (2) objective impairment in one or more cognitive domains; (3) slightly impaired complex instrumental daily abilities, but independent daily living abilities; and (4) no dementia. The PSWEs calculated by self-developed Python scripts were defined for EEG recordings as a median power frequency of < 6 Hz for more than five consecutive seconds. Serum cyclophilin A (CyPA) and matrix metalloproteinase-9 (MMP-9) levels and amyloid-β 42 levels in neuron-derived exosomes were determined. The participants who received continuous positive airway pressure (CPAP) were followed up and their PSWEs were recalculated after 1 year of treatment.

RESULTS

A total of 339 participants were divided into the OSA+MCI group (n = 157), OSA-MCI group (n = 118), and controls (normal cognitive state without OSA) (n = 64). The total PSWEs and the occurrence per minute of PSWEs at stage REM in the OSA+MCI group were higher than those in the OSA-MCI and control groups. The duration ratio of PSWEs at stage REM in the OSA+MCI group significantly increased. The total PSWEs and PSWEs at the F4-M1, O1-M2, and O2-M1 channels in stage REM were independently associated with cognitive impairment in OSA patients. There were positive correlations between the PSWEs and serum CyPA and MMP-9 levels in patients with OSA. The mediation analysis showed that the relationship between mean SaO₂ and percentage of sleep time spent with oxygen saturation <90% with MoCA scores was mediated by the total PSWEs (proportion of mediation 77.89% and 82.89%). The PSWEs were negatively correlated with global cognitive performance and cognitive subdomains. After 1 year of CPAP treatment, the total PSWEs, PSWEs in stage REM, and serum CyPA and MMP-9 levels decreased significantly, and MoCA scores were improved compared with baseline.

CONCLUSIONS

The PSWEs were implicated in cognitive impairment in patients with OSA, and the mechanisms of cognitive impairment due to hypoxia in OSA patients could be BBB dysfunction. The PSWEs can be used as a marker of cognitive impairment in patients with OSA.

TRIAL REGISTRATION

This trial is registered on the Chinese Clinical Trial Registry, number ChiCTR1900021544. The trial was registered on February 27, 2019.

Novel neuroelectrophysiological age index associated with imaging features of brain aging and sleep disorders

Sleep architecture and microstructures alter with aging and sleep disorder-led accelerated aging. We proposed a sleep EEG based brain age prediction model using convolutional neural networks. We then associated the estimated brain age index with brain structural aging features, sleep disorders and various sleep parameters. Our model also showed a higher BAI (predicted brain age minus chronological age) is associated with cortical thinning in various functional areas. We found a higher BAI for sleep disorder groups compared to healthy sleepers, as well as significant differences in the spectral pattern of EEG among different sleep disorders (lower power in slow and ϑ waves for sleep apnea vs. higher power in β and σ for insomnia), suggesting sleep disorder-dependent pathomechanisms of aging. Our results demonstrate that the new EEG-BAI can be a biomarker reflecting brain health in normal and various sleep disorder subjects, and may be used to assess treatment efficacy.

Medial temporal lobe and obstructive sleep apnea: Effect of sex, age, cognitive status and free-water

Medial temporal structures, namely the hippocampus, the entorhinal cortex and the parahippocampal gyrus, are particularly vulnerable to Alzheimer's disease and hypoxemia. Here, we tested the associations between obstructive sleep apnea (OSA) severity and medial temporal lobe volumes in 114 participants aged 55-86 years (35 % women). We also investigated the impact of sex, age, cognitive status, and free-water fraction correction on these associations. Increased OSA severity was associated with larger hippocampal and entorhinal cortex volumes in women, but not in men. Greater OSA severity also correlated with increased hippocampal volumes in participants with amnestic mild cognitive impairment, but not in cognitively unimpaired participants, regardless of sex. Using free-water corrected volumes eliminated all significant associations with OSA severity. Therefore, the increase in medial temporal subregion volumes may possibly be due to edema. Whether these structural manifestations further progress to neuronal death in non-treated OSA patients should be investigated.

Assessment of Alzheimer’s disease-related biomarkers in patients with obstructive sleep apnea: A systematic review and meta-analysis

Increasing evidence links Alzheimer’s disease (AD) to various sleep disorders, including obstructive sleep apnea (OSA). The core AD cerebrospinal fluid (CSF) biomarkers, including amyloid-β 42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau), can reflect key elements of AD pathophysiology before the emergence of symptoms. Besides, the amyloid-β (Aβ) and tau burden can also be tested by positron emission tomography (PET) scans. Electronic databases (PubMed, Embase, Web of Science, and The Cochrane Library) were searched until August 2022 to assess the AD-related biomarkers measured by PET scans and CSF in OSA patients. The overall analysis showed significant differences in Aβ42 levels (SMD = −0.93, 95% CI:−1.57 to −0.29, P < 0.001) and total tau (t-tau) levels (SMD = 0.24, 95% CI: 0.01–0.48, P = 0.308) of CSF, and Aβ burden (SMD = 0.37, 95% CI = 0.13–0.61, P = 0.69) tested by PET scans between the OSA and controls. Furthermore, CSF Aβ42 levels showed significant differences in patients with moderate/severe OSA compared with healthy control, and levels of CSF Aβ42 showed differences in OSA patients with normal cognition as well. Besides, age and BMI have influences on heterogeneity. Our meta-analysis indicated abnormal AD-related biomarkers (CSF and PET scans) in patients with OSA, supporting the current hypothesis that OSA, especially moderate/severe OSA, may start the AD neuropathological process.

Association of a History of Sleep Disorder With Risk of Mild Cognitive Impairment and Alzheimer's Disease Dementia

OBJECTIVE

We explored whether a history of sleep disorder affected a current diagnosis of cognitive impairment and clinical conversion in a non-demented elderly population.

METHODS

Comprehensive clinical data collected as part of the Alzheimer's Disease Neuroimaging Initiative (ADNI) was analyzed. A history of sleep disorder was recorded in the recent ADNI medical database. Standard clinical and neuropsychological tests were performed both at baseline and follow-up visit. Multiple logistic regression analysis was performed after adjusting for age, sex, education, apolipoprotein E ε4 status, vascular risk score, body mass index, Geriatric Depression Scale score, and use of sleeping pills.

RESULTS

A total of 391 cognitively normal individuals, 303 with early mild cognitive impairment (MCI) and 364 with late MCI were included. Sleep disorder history was significantly associated with an increased risk of MCI but not with clinical conversion. A history of insomnia or obstructive sleep apnea (OSA) significantly increased the risk of MCI, but only an OSA history predicted progression to Alzheimer's disease (AD) dementia.

CONCLUSION

Our findings suggest that a sleep disorder history usefully aids early detection of cognitive impairment and emphasize that such sleep disorder, particularly OSA, is important as potential target for AD prevention.

Widespread aberrant functional connectivity throughout the whole brain in obstructive sleep apnea

Objective

Obstructive sleep apnea (OSA) is a sleep-related breathing disorder with high prevalence and is associated with cognitive impairment. Previous neuroimaging studies have reported abnormal brain functional connectivity (FC) in patients with OSA that might contribute to their neurocognitive impairments. However, it is unclear whether patients with OSA have a characteristic pattern of FC changes that can serve as a neuroimaging biomarker for identifying OSA.

Methods

A total of 21 patients with OSA and 21 healthy controls (HCs) were included in this study and scanned using resting-state functional magnetic resonance imaging (fMRI). The automated anatomical labeling (AAL) atlas was used to divide the cerebrum into 90 regions, and FC between each pair of regions was calculated. Univariate analyses were then performed to detect abnormal FCs in patients with OSA compared with controls, and multivariate pattern analyses (MVPAs) were applied to classify between patients with OSA and controls.

Results

The univariate comparisons did not detect any significantly altered FC. However, the MVPA showed a successful classification between patients with OSA and controls with an accuracy of 83.33% (p = 0.0001). Furthermore, the selected FCs were associated with nearly all brain regions and widely distributed in the whole brain, both within and between, many resting-state functional networks. Among these selected FCs, 3 were significantly correlated with the apnea-hypopnea index (AHI) and 2 were significantly correlated with the percentage of time with the saturation of oxygen (SaO₂) below 90% of the total sleep time (%TST < 90%).

Conclusion

There existed widespread abnormal FCs in the whole brain in patients with OSA. This aberrant FC pattern has the potential to serve as a neurological biomarker of OSA, highlighting its importance for understanding the complex neural mechanism underlying OSA and its cognitive impairment.

Effects of intermittent hypoxia with thrombin in an in vitro model of human brain endothelial cells and their impact on PAR-1/PAR-3 cleavage

Patients with obstructive sleep apnea/hypopnea (OSA) are at high risk of cerebrovascular diseases leading to cognitive impairment. The oxidative stress generated by intermittent hypoxia (IH) could lead to an increase in blood-brain barrier (BBB) permeability, an essential interface for the protection of the brain. Moreover, in patients with OSA, blood coagulation could be increased leading to cardiovascular complications. Thrombin is a factor found increased in these populations that exerts various cellular effects through activation of protease activated receptors (PARs). Thus, we have evaluated in an in vitro BBB model the association of IH with thrombin at two concentrations. We measured the apparent BBB permeability, expression of tight junctions, ROS production, HIF-1α expression, and cleavage of PAR-1/PAR-3. Pre-treatment with dabigatran was performed. IH and higher thrombin concentrations altered BBB permeability: high levels of HIF-1α expression, ROS and PAR-1 activation compared to PAR-3 in such conditions. Conversely, lower concentration of thrombin associated with IH appear to have a protective effect on BBB with a significant cleavage of PAR-3. Dabigatran reversed the deleterious effect of thrombin at high concentrations but also suppressed the beneficial effect of low dose thrombin. Therefore, thrombin and PARs represent novel attractive targets to prevent BBB opening in OSA.

Circulating ADAMTS13 Levels Are Associated with an Increased Occurrence of Obstructive Sleep Apnea

Background and Aims. Obstructive sleep apnea (OSA) is strongly associated with obesity, metabolic diseases, coronary artery disease (CAD), stroke, hypertension, and other disorders. This study assessed the relationship between circulating a disintegrin and metalloprotease with a thrombospondin type 1 motif, member 13 (ADAMTS13) levels and the presence of OSA. Materials and Methods. This cross-sectional study included a total of 223 patients. We used a powerful high-throughput multiplexed immunobead-based assay to detect circulating levels of ADAMTS13. The associations between circulating ADAMTS13 levels and OSA were evaluated by multivariate logistic regression analysis. Results. Circulating ADAMTS13 levels were significantly elevated in patients with OSA compared with controls (0.8 vs. 2.7 μg/mL, respectively, $P<0.001$ ). After adjusting for confounding factors, circulating ADAMTS13 levels were significantly independently associated with the presence of OSA ( $\text{odds}\text{ratio}=9.96$ , 95% confidence interval (CI) =4.11–24.13, $P<0.001$ ). Furthermore, circulating ADAMTS13 levels showed discriminatory accuracy in assessing the presence of OSA (area under the curve: 0.87, 95% CI 0.81–0.93, $P<0.001$ ). Conclusion. Circulating ADAMTS13 levels were significantly correlated with the presence of OSA. ADAMTS13 may therefore function as a novel biomarker for monitoring the development and progression of OSA.

Multiple Sclerosis and related disorders

Multiple Sclerosis (MS) is a common neuroinflammatory disorder which is associated with disabling clinical consequences. The MS disease process may involve neural centers implicated in the control of breathing, leading to ventilatory disturbances during both wakefulness and sleep. In this chapter, a brief overview of MS disease mechanisms and clinical sequelae including sleep disorders is provided. The chapter then focuses on obstructive sleep apnea-hypopnea (OSAH) which is the most prevalent respiratory control abnormality encountered in ambulatory MS patients. The diagnosis, prevalence, and clinical consequences as well as data on effects of OSAH treatment in MS patients are discussed, including the impact on the disabling symptom of fatigue and other clinical sequelae. We also review pathophysiologic mechanisms contributing to OSAH in MS, and in turn mechanisms by which OSAH may impact on the MS disease process, resulting in a bidirectional relationship between these two conditions. We then discuss central sleep apnea, other respiratory control disturbances, and the pathogenesis and management of respiratory muscle weakness and chronic hypoventilation in MS. We also provide a brief overview of Neuromyelitis Optica Spectrum Disorders and review current data on respiratory control disturbances and sleep-disordered breathing in that condition.

Abnormal Spontaneous Brain Activity and Cognitive Impairment in Obstructive Sleep Apnea

PURPOSE

This study aimed to explore the alterations in spontaneous brain activity in obstructive sleep apnea (OSA) using percent amplitude of fluctuation (PerAF) and investigate the relationship between abnormal spontaneous brain activity and cognitive impairment in OSA.

PATIENTS AND METHODS

Overall, 52 patients with moderate to severe OSA and 61 healthy controls (HCs) were eventually enrolled in this study. All participants underwent resting-state functional magnetic resonance (rs-fMRI) and T1-weighted imaging. The PerAF was calculated and compared between patients with OSA and HCs, with voxel level P < 0.001 and cluster level P < 0.05 corrected with Gaussian Random Field was be considered statistically different. A partial correlation analysis was used to assess the relationship between altered PerAF and clinical assessments in patients with OSA.

RESULTS

Compared to HCs, patients with OSA had significantly lower PerAF values in the right rectal gyrus and left superior frontal gyrus, but higher PerAF values in the right cerebellum posterior lobe and left middle frontal gyrus. The PerAF values of some specific regions in patients with OSA correlated with sleep efficiency and Montreal Cognitive Assessment scores. Additionally, support vector machine analysis showed that PerAF values in all differential brain regions could differentiate patients with OSA from HCs with good accuracy.

CONCLUSION

Specific brain areas in OSA patients may exhibit aberrant neuronal activity, and these anomalies may be linked to decreased cognitive performance. This discovery offers fresh perspectives on these patients' neurocognition.

Cognitive impairment caused by hypoxia: from clinical evidences to molecular mechanisms

Hypoxia is a state of reduced oxygen supply and excessive oxygen consumption. According to the duration of hypoxic period, it can be classified as acute and chronic hypoxia. Both acute and chronic hypoxia could induce abundant neurological deficits. Although there have been significant advances in the pathophysiological injuries, few studies have focused on the cognitive dysfunction. In this review, we focused on the clinical evidences and molecular mechanisms of cognitive impairment under acute and chronic hypoxia. Hypoxia can impair several cognitive domains such as attention, learning and memory, procession speed and executive function, which are similar in acute and chronic hypoxia. The severity of cognitive deficit correlates with the duration and degree of hypoxia. Recovery can be achieved after acute hypoxia, while sequelae or even dementia can be observed after chronic hypoxia, perhaps due to the different molecular mechanisms. Cardiopulmonary compensatory response, glycolysis, oxidative stress, calcium overload, adenosine, mitochondrial disruption, inflammation and excitotoxicity contribute to the molecular mechanisms of cognitive deficit after acute hypoxia. During the chronic stage of hypoxia, different adaptive responses, impaired neurovascular coupling, apoptosis, transcription factors-mediated inflammation, as well as Aβ accumulation and tau phosphorylation account for the neurocognitive deficit. Moreover, brain structural changes with hippocampus and cortex atrophy, ventricle enlargement, senile plaque and neurofibrillary tangle deposition can be observed under chronic hypoxia rather than acute hypoxia.

Increased serum levels of cyclophilin a and matrix metalloproteinase-9 are associated with cognitive impairment in patients with obstructive sleep apnea

OBJECTIVES

To investigate the relationship between serum cyclophilin A (CyPA) and matrix metalloproteinase-9 (MMP-9) levels and mild cognitive impairment (MCI) in patients with obstructive sleep apnea (OSA).

METHODS

Study subjects underwent whole-night in-laboratory polysomnography (PSG), and all participants were scored using a neuropsychological scale and peripheral blood samples were collected the next morning. The presence and severity of OSA were assessed with the apnea hypopnea index (AHI), and OSA was defined as AHI ≥5 events/hour. MCI was defined as the MoCA ≤25, and met the revised Mayo Clinic criteria. Serum CyPA and MMP-9 levels were measured with enzyme-linked immunosorbent assays (ELISAs). A univariate analysis and a logistic model were used to assess risk factors for MCI in patients with OSA. A correlation analysis was performed to estimate whether a linear relationship existed between serum CyPA and MMP-9 levels and the severity of cerebral small vessel disease (CSVD) and white matter hyperintensities (WMHs). A linear regression analysis was used to clarify the relationship between serum CyPA and MMP-9 levels and the degree of cognitive impairment in patients with OSA.

RESULTS

The 186 patients who met the criteria for inclusion and exclusion comprised 71 patients with OSA presenting with MCI (OSA + MCI), 73 patients with OSA without MCI (OSA-MCI), and 42 controls. Patients with OSA + MCI presented higher serum CyPA and MMP-9 levels than patients in the OSA-MCI (11.56 ± 4.52 ng/ml vs 9.95 ± 3.63 ng/ml, p = 0.020; 597.71 ± 204.41 ng/ml vs 523.05 ± 205.47 ng/ml, p = 0.030) and control groups (11.56 ± 4.52 ng/ml vs 8.80 ± 3.71 ng/m, p = 0.001; 597.71 ± 204.41 ng/ml vs 490.39 ± 155.07 ng/ml, p = 0.002). The logistic regression analysis revealed that both CyPA (OR: 1.111, 95% CIs: 1.012-1.219, p = 0.027) and MMP-9 levels (OR: 1.003, 95% CIs: 1.000-1.004, p = 0.011) contributed significantly to MCI in patients with OSA. In the OSA + MCI group, positive correlations were observed between serum CyPA and MMP-9 levels with Scheltens scores (r = 0.437, p = 0.000; r = 0.613, p = 0.000, respectively) and total CSVD burden scores (r = 0.318, p = 0.003; r = 0.487, p = 0.000, respectively). Serum CyPA and MMP-9 levels were linearly negatively correlated with mean oxygen saturation during sleep (mean SaO2) (r = -0.595, p = 0.000; r = -0.570, p = 0.000). There was linear correlation between mean SaO2 and MoCA scores by Pearson's correlation coefficient (r = 0.403, p = 0.000). The linear regression analysis revealed negative correlations between serum CyPA and MMP-9 levels and the Montreal Cognitive Assessment (MoCA) scores (r = -0.528, p = 0.000; r = -0.459, p = 0.000, respectively), and serum CyPA levels were negatively correlated with score of cognitive subdomainss, including visuo-executive function, attention and delayed recall. However, serum MMP-9 levels were negatively correlated with score of cognitive subdomains, including visuo-executive function and delayed recall.

CONCLUSIONS

Increased serum levels of CyPA and MMP-9 are associated with MCI in OSA patients and directly related to the severity of CSVD and WMHs. The results suggest that damage to the blood-brain barrier (BBB) may be involved in the early stages of cognitive impairment in patients with OSA.

Intermittent hypoxia mimicking obstructive sleep apnea aggravates early brain injury following ICH via neuroinflammation and apoptosis

Spontaneous intracerebral hemorrhage (ICH) is a subtype of stroke associated with high mortality and morbidity due to the lack of effective therapy. Obstructive sleep apnea (OSA) has been reported to aggravate early brain injury (EBI) and worsen the overall outcome of patients with ICH. However, the precise role of OSA-mediated neuroinflammation and apoptosis following ICH has not been confirmed. The present study aimed to investigate the neuronal damage induced by OSA and the potential molecular mechanisms by which ICH-induced EBI regulates neural apoptosis in a C57BL/6 mouse ICH model. Mortality, neurological score, brain water content and neuronal death were evaluated by Evans blue extravasation, TUNEL staining, ELISA, analysis of reactive oxygen species/lipid peroxidation and western blotting. The results showed that OSA induction decreased survival rate, neurological score and neuron survival and upregulated the protein expression levels of Caspase-3, Bax, cytokines IL-1β, IL-6 and TNF-α and NF-κB, which indicated that OSA-mediated induction of apoptosis and neuroinflammation aggravated neuronal death following ICH. The molecular mechanism was partly dependent on the activating transcription factor/CHOP pathway. Taken together, the results demonstrated that OSA worsens neurological outcomes in mice and increases neuronal death by enhancing neural apoptosis and neuroinflammation.

Obstructive sleep apnoea in women with idiopathic intracranial hypertension: a sub-study of the idiopathic intracranial hypertension weight randomised controlled trial (IIH: WT)

Objective

Obesity is a risk factor for idiopathic intracranial hypertension (IIH) and obstructive sleep apnoea (OSA). We aimed to determine the prevalence of OSA in IIH and evaluate the diagnostic performance of OSA screening tools in IIH. Additionally, we evaluated the relationship between weight loss, OSA and IIH over 12 months.

Methods

A sub-study of a multi-centre, randomised controlled parallel group trial comparing the impact of bariatric surgery vs. community weight management intervention (CWI) on IIH-related outcomes over 12 months (IIH:WT). OSA was assessed using home-based polygraphy (ApneaLink Air, ResMed) at baseline and 12 months. OSA was defined as an apnoea–hypopnoea index (AHI) ≥ 15 or ≥ 5 with excessive daytime sleepiness (Epworth Sleepiness Scale ≥11 ).

Results

Of the 66 women in the IIH: WT trial, 46 were included in the OSA sub-study. OSA prevalence was 47% (n = 19). The STOP-BANG had the highest sensitivity (84%) compared to the Epworth Sleepiness Scale (69%) and Berlin (68%) to detect OSA. Bariatric surgery resulted in greater reductions in AHI vs. CWI (median [95%CI] AHI reduction of  – 2.8 [ – 11.9, 0.7], p = 0.017). Over 12 months there was a positive association between changes in papilloedema and AHI (r = 0.543, p = 0.045), despite adjustment for changes in the body mass index (R² = 0.522, p = 0.017).

Conclusion

OSA is common in IIH and the STOP-BANG questionnaire was the most sensitive screening tool. Bariatric surgery improved OSA in patients with IIH. The improvement in AHI was associated with improvement in papilloedema independent of weight loss. Whether OSA treatment has beneficial impact on papilloedema warrants further evaluation.

Trial registration number

IIH: WT is registered as ISRCTN40152829 and on ClinicalTrials.gov as NCT02124486 (28/04/2014).

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10700-9.

Obstructive Sleep Apnea: Cognitive Outcomes

There is a strong association between obstructive sleep apnea (OSA) and cognitive dysfunction. Executive function, attention, verbal/visual long-term memory, visuospatial/constructional ability, and information processing are more likely to be affected, whereas language, psychomotor function, and short-term memory are less likely to be affected. Increased accumulation of Aß₂-amyloid in the brain, episodic hypoxemia, oxidative stress, vascular inflammation, and systemic comorbidities may contribute to the pathogenesis. Patients with OSA should have cognitive screening or formal testing, and patients with cognitive decline should have testing for OSA. Treatment with continuous positive airway pressure may improve cognitive symptoms in the patient with OSA.

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.

Brain Mechanisms of COVID-19-Sleep Disorders

2020 and 2021 have been unprecedented years due to the rapid spread of the modified severe acute respiratory syndrome coronavirus around the world. The coronavirus disease 2019 (COVID-19) causes atypical infiltrated pneumonia with many neurological symptoms, and major sleep changes. The exposure of people to stress, such as social confinement and changes in daily routines, is accompanied by various sleep disturbances, known as 'coronasomnia' phenomenon. Sleep disorders induce neuroinflammation, which promotes the blood-brain barrier (BBB) disruption and entry of antigens and inflammatory factors into the brain. Here, we review findings and trends in sleep research in 2020-2021, demonstrating how COVID-19 and sleep disorders can induce BBB leakage via neuroinflammation, which might contribute to the 'coronasomnia' phenomenon. The new studies suggest that the control of sleep hygiene and quality should be incorporated into the rehabilitation of COVID-19 patients. We also discuss perspective strategies for the prevention of COVID-19-related BBB disorders. We demonstrate that sleep might be a novel biomarker of BBB leakage, and the analysis of sleep EEG patterns can be a breakthrough non-invasive technology for diagnosis of the COVID-19-caused BBB disruption.

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.

Microglia in neurodegenerative diseases

A major feature of neurodegeneration is disruption of central nervous system homeostasis, during which microglia play diverse roles. In the central nervous system, microglia serve as the first line of immune defense and function in synapse pruning, injury repair, homeostasis maintenance, and regulation of brain development through scavenging and phagocytosis. Under pathological conditions or various stimulations, microglia proliferate, aggregate, and undergo a variety of changes in cell morphology, immunophenotype, and function. This review presents the features of microglia, especially their diversity and ability to change dynamically, and reinterprets their role as sensors for multiple stimulations and as effectors for brain aging and neurodegeneration. This review also summarizes some therapeutic approaches for neurodegenerative diseases that target microglia.

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.

Cognitive profiles in obstructive sleep apnea: a cluster analysis in sleep clinic and community samples

STUDY OBJECTIVES

Although cognitive dysfunction is a recognized consequence of untreated obstructive sleep apnea (OSA), the deficit pattern is heterogeneous. Understanding this heterogeneity may identify those at risk of cognitive deficits and guide intervention strategies. To facilitate understanding, we examined whether distinct profiles of neuropsychological performance were present in OSA and, if so, how they are related to other OSA features.

METHODS

We studied sleep clinic (n = 121) and community (n = 398) samples with moderate-severe OSA (apnea-hypopnea index ≥ 15 events/h). Attention and memory were assessed using the Cognitive Drug Research system. Sleep was assessed using polysomnography in the clinic sample and dual channel (flow, oximetry) portable monitoring in the community sample. Latent profile analysis was used to determine structure of cognitive clusters. Discriminant function analysis was used to examine associations between nocturnal and diurnal features of OSA and profile membership.

RESULTS

Both samples were best characterized by a 3-profile solution: (1) strong thinkers (performed well across most domains and showed greater cognitive reserve); (2) inattentive fast thinkers (strong processing speed but poor ability to maintain attention); and (3) accurate slow thinkers (strengths in maintaining attention but poor processing speed). Profile membership was associated with mean overnight oxygen saturation and cognitive reserve in the clinic sample and the presence of cardiovascular disease and/or diabetes in the community sample.

CONCLUSIONS

These findings help explain the diversity of outcomes in previous studies of cognitive dysfunction in OSA by demonstrating that individual differences in cognitive reserve, nocturnal oxygen saturation, and comorbidities affect how cognition is impacted by OSA.

Potential Biochemical Mechanisms of Brain Injury in Diabetes Mellitus

The goal of this review was to summarize current biochemical mechanisms of and risk factors for diabetic brain injury. We mainly summarized mechanisms published in the past three years and focused on diabetes induced cognitive impairment, diabetes-linked Alzheimer’s disease, and diabetic stroke. We think there is a need to conduct further studies with increased sample sizes and prolonged period of follow-ups to clarify the effect of DM on brain dysfunction. Additionally, we also think that enhancing experimental reproducibility using animal models in conjunction with application of advanced devices should be considered when new experiments are designed. It is expected that further investigation of the underlying mechanisms of diabetic cognitive impairment will provide novel insights into therapeutic approaches for ameliorating diabetes-associated injury in the brain.

Sera of elderly obstructive sleep apnea patients alter blood-brain barrier integrity in vitro: a pilot study

Obstructive sleep apnea syndrome (OSAS) is characterized by repeated episodes of hypoxia during the night. The severity of the disorder can be evaluated using an apnea–hypopnea index (AHI). The physiological consequences are mainly cardiovascular and neuronal dysfunctions. One hypothesis to explain such associated neurological disorders is disruption of the blood–brain barrier (BBB), which protects the brain from endovascular cytotoxic compounds. We selected two subgroups of volunteers from the PROOF cohort study (France), a group of patients suffering newly diagnosed severe OSAS (AHI > 30/h) and a group showing no sleep apnea (AHI < 5/h). We exposed a human in vitro BBB model of endothelial cells (HBEC-5i) with sera of patients with and without OSAS. After exposure, we measured the apparent BBB permeability as well as tight junction and ABC transporter expression using whole cell ELISA. We showed that after incubation with sera from OSAS patients, there was a loss of integrity in the human in vitro BBB model; this was reflected by an increase in permeability (43%; p < 0.001) and correlated with a 50% and 40% decrease in tight junction protein expression of ZO-1 and claudin-5, respectively. At the same time, we observed an upregulation in Pgp protein expression (52%) and functionality, and a downregulation in BCRP expression (52%). Our results demonstrated that severe BBB disorder after exposure to sera from OSAS patients was reflected by an opening of the BBB.

Obstructive Sleep Apnea in Neurodegenerative Disorders: Current Evidence in Support of Benefit from Sleep Apnea Treatment

Obstructive sleep apnea (OSA) is a prevalent disorder characterized by recurrent upper airway obstruction during sleep resulting in intermittent hypoxemia and sleep fragmentation. Research has recently increasingly focused on the impact of OSA on the brain's structure and function, in particular as this relates to neurodegenerative diseases. This article reviews the links between OSA and neurodegenerative disease, focusing on Parkinson's disease, including proposed pathogenic mechanisms and current knowledge on the effects of treatment.

Plasma Extracellular Vesicles in Children with OSA Disrupt Blood-Brain Barrier Integrity and Endothelial Cell Wound Healing in Vitro

Pediatric obstructive sleep apnea (P-OSA) is associated with neurocognitive deficits and endothelial dysfunction, suggesting the possibility that disruption of the blood-brain barrier (BBB) may underlie these morbidities. Extracellular vesicles (EVs), which include exosomes, are small particles involved in cell-cell communications via different mechanisms and could play a role in OSA-associated end-organ injury. To examine the roles of EVs in BBB dysfunction, we recruited three groups of children: (a) absence of OSA or cognitive deficits (CL, n = 6), (b) OSA but no evidence of cognitive deficits (OSA-NC(-), n = 12), and (c) OSA with evidence of neurocognitive deficits (OSA-NC(+), n = 12). All children were age-, gender-, ethnicity-, and BMI-z-score-matched, and those with OSA were also apnea-hypopnea index (AHI)-matched. Plasma EVs were characterized, quantified, and applied on multiple endothelial cell types (HCAEC, HIAEC, human HMVEC-D, HMVEC-C, HMVEC-L, and hCMEC/D3) while measuring monolayer barrier integrity and wound-healing responses. EVs from OSA children induced significant declines in hCMEC/D3 transendothelial impedance compared to CL (p < 0.001), and such changes were greater in NC(+) compared to NC(-) (p < 0.01). The effects of EVs from each group on wound healing for HCAEC, HIAEC, HMVED-d, and hCMEC/D3 cells were similar, but exhibited significant differences across the three groups, with evidence of disrupted wound healing in P-OSA. However, wound healing in HMVEC-C was only affected by NC(+) (p < 0.01 vs. NC(-) or controls (CO). Furthermore, no significant differences emerged in HMVEC-L cell wound healing across all three groups. We conclude that circulating plasma EVs in P-OSA disrupt the integrity of the BBB and exert adverse effects on endothelial wound healing, particularly among OSA-NC(+) children, while also exhibiting endothelial cell type selectivity. Thus, circulating EVs cargo may play important roles in the emergence of end-organ morbidity in pediatric OSA.

GCH1 (rs841) polymorphism in the nitric oxide-forming pathway has protective effects on obstructive sleep apnea

Several studies have recently investigated the contribution of genetic factors in obstructive sleep apnea (OSA). Patients with OSA suffer from a reduction in nitric oxide (NO) serum level. This study investigated rs841, A930G p22phox, and rs1799983 polymorphisms in three critical genes involved in NO formation. A total of 94 patients with OSA and 100 healthy controls were enrolled into the study. Results showed there was no association between rs841, A930G p22phox and rs1799983 polymorphism and the risk of OSA (P = 0.51, P = 0.4 and P = 0.33, respectively). Moreover, rs841 GA genotype had a reverse relationship with the severity of OSA (P = 0.005). On the other hand, rs841 GA and A930G p22phox AA genotypes had a protective effect on daytime sleepiness in OSA patients (P = 0.01and P = 0.02, respectively). Additionally, the combination of rs841 and A930G p22phox (AG/AG and AG/AA) genotypes was significantly associated with a reduction in daytime sleepiness in OSA patients (P = 0.03 and P = 0.03, respectively). According to the results of our study, GA genotype of rs841 and GA/AA genotypes of A930G p22phox polymorphisms significantly reduced the severity of the problem and daytime sleepiness in OSA patients.

Compensatory Neural Recruitment for Error-Related Cerebral Activity in Patients with Moderate-To-Severe Obstructive Sleep Apnea

(1) Background: Although it is known that obstructive sleep apnea (OSA) impairs action-monitoring function, there is only limited information regarding the associated cerebral substrate underlying this phenomenon. (2) Methods: The modified Flanker task, error-related event-related potentials (ERPs), namely, error-related negativity (ERN) and error positivity (Pe), and functional magnetic resonance imaging (fMRI) were used to evaluate neural activities and the functional connectivity underlying action-monitoring dysfunction in patients with different severities of OSA. (3) Results: A total of 14 control (Cont) subjects, 17 patients with moderate OSA (mOSA), and 10 patients with severe OSA (sOSA) were enrolled. A significant decline in posterror correction rate was observed in the modified Flanker task when patients with mOSA were compared with Cont subjects. Comparison between patients with mOSA and sOSA did not reveal any significant difference. In the analysis of ERPs, ERN and Pe exhibited declined amplitudes in patients with mOSA compared with Cont subjects, which were found to increase in patients with sOSA. Results of fMRI revealed a decreased correlation in multiple anterior cingulate cortex functional-connected areas in patients with mOSA compared with Cont subjects. However, these areas appeared to be reconnected in patients with sOSA. (4) Conclusions: The behavioral, neurophysiological, and functional image findings obtained in this study suggest that mOSA leads to action-monitoring dysfunction; however, compensatory neural recruitment might have contributed to the maintenance of the action-monitoring function in patients with sOSA.

Predictors of delirium after cardiac surgery in patients with sleep disordered breathing

Introduction

Delirium ranks among the most common complications after cardiac surgery. Although various risk factors have been identified, the association between sleep disordered breathing (SDB) and delirium has barely been examined so far. Here, our objectives were to determine the incidence of post-operative delirium and to identify the risk factors for delirium in patients with and without SDB.

Methods

This subanalysis of the ongoing prospective observational study CONSIDER-AF (ClinicalTrials.govidentifierNCT02877745) examined risk factors for delirium in 141 patients undergoing cardiac surgery. The presence and type of SDB were assessed with a portable SDB monitor the night before surgery. Delirium was prospectively assessed with the validated Confusion Assessment Method for the Intensive Care Unit on the day of extubation and for a maximum of 3 days.

Results

Delirium was diagnosed in 23% of patients: in 16% of patients without SDB, in 13% with obstructive sleep apnoea and in 49% with central sleep apnoea. Multivariable logistic regression analysis showed that delirium was independently associated with age ≥70 years (OR 5.63, 95% CI 1.79–17.68; p=0.003), central sleep apnoea (OR 4.99, 95% CI 1.41–17.69; p=0.013) and heart failure (OR 3.3, 95% CI 1.06–10.35; p=0.039). Length of hospital stay and time spent in the intensive care unit/intermediate care setting were significantly longer for patients with delirium.

Conclusions

Among the established risk factors for delirium, central sleep apnoea was independently associated with delirium. Our findings contribute to identifying patients at high risk of developing post-operative delirium who may benefit from intensified delirium prevention strategies.

Olfactory Event-Related Potentials and Exhaled Organic Volatile Compounds: The Slow Link Between Olfactory Perception and Breath Metabolic Response. A Pilot Study on Phenylethyl Alcohol and Vaseline Oil

Olfactory processing starts with the breath and elicits neuronal, metabolic and cortical responses. This process can be investigated centrally via the Olfactory Event-Related Potentials (OERPs) and peripherally via exhaled Volatile Organic Compounds (VOCs). Despite this, the relationship between OERPs (i.e., N1 and Late Positive Component LPC) and exhaled VOCs has not been investigated enough. The aim of this research is to study OERPs and VOCs connection to two different stimuli: phenylethyl alcohol (PEA) and Vaseline Oil (VO). Fifteen healthy subjects performed a perceptual olfactory task with PEA as a smell target stimulus and VO as a neutral stimulus. The results suggest that OERPs and VOCs distributions follow the same amplitude trend and that PEA is highly arousing in both psychophysiological measures. PEA shows ampler and faster N1, a component related to the sensorial aspect of the stimulus. The N1 topographic localization is different between PEA and VO: PEA stimulus evokes greater N1 in the left centroparietal site. LPC, a component elicited by the perceptual characteristic of the stimulus, shows faster latency in the Frontal lobe and decreased amplitude in the Central and Parietal lobe elicited by the PEA smell. Moreover, the delayed time between the onset of N1-LPC and the onset of VOCs seems to be about 3 s. This delay could be identified as the internal metabolic time in which the odorous stimulus, once perceived at the cortical level, is metabolized and subsequently exhaled. Furthermore, the VO stimulus does not allocate the attentive, perceptive and metabolic resource as with PEA.

Cognitive Functioning in Patients with Pediatric-Onset Multiple Sclerosis, an Updated Review and Future Focus

Pediatric-onset multiple sclerosis (POMS) is relatively rare, but as technology and neuroimaging advance, an increasing number of cases are identified, and our understanding of how multiple sclerosis (MS) impacts the developing brain improves. There are consistent findings in the literature highlighting the impact of MS and other demyelinating diseases on cognitive functioning and cognitive development. We also have a better understanding of how POMS impacts psychosocial functioning and functional outcomes in daily living. This paper hopes to review findings associated with cognitive and psychosocial functioning in patients with POMS, as well as explore more recent advances in the field and how they relate to cognitive and psychosocial outcomes. We also discuss the ongoing need for future studies with a focus on better understanding deficits and disease correlates, but also preventative measures and potential rehabilitation.