Impact of obstructive sleep apnoea and intermittent hypoxia on cardiovascular and cerebrovascular regulation

Monitoring of Home Respiratory Polygraphy During Mandibular Distraction Osteogenesis Succeeded by LeFort I Osteotomy in Adult Patients With Obstructive Sleep Apnea

BACKGROUND

Bilateral internal ramus distraction (BIRD) is now part of select protocols for treating obstructive sleep apnea (OSA). Introducing a home monitoring protocol offers a valuable alternative to overnight laboratory polysomnography (PSG).

PURPOSE

The purpose of this study was to evaluate and compare OSA parameters obtained via home respiratory polygraphy (HRP) and hospital PSG in a cohort of patients undergoing mandibular distraction for OSA management.

STUDY DESIGN, SETTING, SAMPLE

Hospital Universitario La Princesa (Madrid) researchers conducted a prospective cohort study with patients diagnosed with moderate (apnea-hypopnea index (AHI) = 15 to 30) to severe (AHI>30) OSA undergoing BIRD followed by LeFort maxillary osteotomy. Exclusion criteria were as follows: severe systemic diseases, central apneas, smoking, poor dental hygiene, or prior OSA interventions.

PREDICTOR VARIABLE

The predictor variable was PSG and HRP techniques.

MAIN OUTCOME VARIABLES

The main outcome variable comprises a collection of OSA parameters, including the AHI, oxygen desaturation index (ODI), and time spent below 90% oxygen saturation (T90). These data were measured both before and after distraction, as well as after 6 mm, 9 mm, and 12 mm of mandibular distraction.

COVARIATES

The covariates were age, sex, cardiovascular risk parameters, and the Epworth sleepiness scale.

ANALYSES

Pearson's correlation analyzed AHI, ODI, and T90 values from PSG and HRP. Wilcoxon Signed Rank-Sum Test compared 2 distraction stages, and the Friedman Test evaluated 3 stages (P < .05). Multiple regression analysis assessed if covariates were independent risk factors for postoperative persistent OSA.

RESULTS

The study included 32 patients (25% with moderate and 75% with severe OSA). Final AHI was 10.9 ± 8.9 (events/hour) with HRP, compared to 15.2 ± 13.4 with PSG (r = 0.7, P < .05). ODI was 9.0 ± 8.1 (des/h) with HRP and 8.7 ± 9.5 with PSG (r = 0.85, P < .05). T90 was 1.6 ± 2.2 with HRP and 1.3 ± 3.0 with PSG (r = 0.6, P < .05). Based on HRP data, AHI improved from D1 (34.0 ± 19.5) to D2 (20.8 ± 14.1) and D3 (12.5 ± 10.4) (P < .05). ODI decreased from D1 (26.1 ± 19.0) to D2 (16.0 ± 12.6) and D3 (9.4 ± 8.8) (P < .05). T90 reduced from D1 (8.2 ± 12.6) to D2 (4.1 ± 5.2) and D3 (1.9 ± 2.8) (P < .05). Multiple regression analysis of comorbidities produced nonsignificant results.

CONCLUSION AND RELEVANCE

Monitoring BIRD through HRP has demonstrated efficacy in yielding results that align with PSG.

Acute Intermittent Hypoxia With High-Intensity Gait Training in Chronic Stroke: A Phase II Randomized Crossover Trial

BACKGROUND

Studies in individuals with chronic stroke indicate high-intensity training (HIT) focused on walking improves locomotor function, which may be due to repeated activation of locomotor circuits and serotonin-dependent modulation of motor output. Separate studies in animals and individuals with spinal cord injury suggest acute intermittent hypoxia (AIH) can augment the effects of locomotor interventions through similar serotonin-dependent mechanisms, although no studies have coupled AIH with HIT in individuals poststroke. The goal of this study was to evaluate the safety and efficacy of AIH+HIT versus HIT alone in individuals with chronic stroke.

METHODS

This phase II double-blind randomized, crossover trial recruited individuals between 18 and 85 years old, >6 months poststroke, and self-selected speeds <1.0 m/s. Participants received up to 15 sessions of AIH for 30 minutes using 15 cycles of hypoxia (60-90 seconds; 8%-9% O2) and normoxia (30-60 seconds; 21% O2), followed by 1 hour of HIT targeting >75% heart rate reserve. The control condition received normoxia for 30 minutes before HIT. Following the first training phase, participants performed the second phase >1 month later. The primary outcomes were self-selected speed and fastest speed, a 6-minute walk test, and peak treadmill speed. A 3-way mixed-model ANOVA assessed the effects of time, training, and order of interventions.

RESULTS

Of 55 individuals screened, 35 were randomized to AIH+HIT or normoxia+HIT first, and 28 individuals completed both interventions, revealing greater gains in self-selected speeds (0.14 [0.08-0.18] versus 0.05 [0.01-0.10] m/s), fastest speed (0.16 [0.10-0.21] versus 0.06 [0.02-0.10] m/s), and peak treadmill speed (0.21 [0.14-0.29] versus 0.11 [0.06-0.16] m/s) following AIH+HIT versus normoxia+HIT (P<0.01) with no order effects. Greater gains in spatiotemporal symmetry were observed with AIH+HIT, with worse outcomes for those prescribed serotonin-mediated antidepressant medications.

CONCLUSIONS

AIH+HIT resulted in greater gains in locomotor function than normoxia+HIT. Subsequent phase III trials should further evaluate the efficacy of this intervention.

REGISTRATION

URL: https://clinicaltrials.gov/; Unique identifier: NCT04472442.

Older adults at greater risk for Alzheimer's disease show stronger associations between sleep apnea severity in REM sleep and verbal memory

BACKGROUND

Obstructive sleep apnea (OSA) increases risk for cognitive decline and Alzheimer's disease (AD). While the underlying mechanisms remain unclear, hypoxemia during OSA has been implicated in cognitive impairment. OSA during rapid eye movement (REM) sleep is usually more severe than in non-rapid eye movement (NREM) sleep, but the relative effect of oxyhemoglobin desaturation during REM versus NREM sleep on memory is not completely characterized. Here, we examined the impact of OSA, as well as the moderating effects of AD risk factors, on verbal memory in a sample of middle-aged and older adults with heightened AD risk.

METHODS

Eighty-one adults (mean age:61.7 ± 6.0 years, 62% females, 32% apolipoprotein E ε4 allele (APOE4) carriers, and 70% with parental history of AD) underwent clinical polysomnography including assessment of OSA. OSA features were derived in total, NREM, and REM sleep. REM-NREM ratios of OSA features were also calculated. Verbal memory was assessed with the Rey Auditory Verbal Learning Test (RAVLT). Multiple regression models evaluated the relationships between OSA features and RAVLT scores while adjusting for sex, age, time between assessments, education years, body mass index (BMI), and APOE4 status or parental history of AD. The significant main effects of OSA features on RAVLT performance and the moderating effects of AD risk factors (i.e., sex, age, APOE4 status, and parental history of AD) were examined.

RESULTS

Apnea-hypopnea index (AHI), respiratory disturbance index (RDI), and oxyhemoglobin desaturation index (ODI) during REM sleep were negatively associated with RAVLT total learning and long-delay recall. Further, greater REM-NREM ratios of AHI, RDI, and ODI (i.e., more events in REM than NREM) were related to worse total learning and recall. We found specifically that the negative association between REM ODI and total learning was driven by adults 60 + years old. In addition, the negative relationships between REM-NREM ODI ratio and total learning, and REM-NREM RDI ratio and long-delay recall were driven by APOE4 carriers.

CONCLUSION

Greater OSA severity, particularly during REM sleep, negatively affects verbal memory, especially for people with greater AD risk. These findings underscore the potential importance of proactive screening and treatment of REM OSA even if overall AHI appears low.

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).

Carotid body contribution to the physio-pathological consequences of intermittent hypoxia: role of nitro-oxidative stress and inflammation

Obstructive sleep apnoea (OSA), characterized by chronic intermittent hypoxia (CIH), is considered to be an independent risk for hypertension. The pathological cardiorespiratory consequences of OSA have been attributed to systemic oxidative stress, inflammation and sympathetic overflow induced by CIH, but an emerging body of evidence indicates that a nitro-oxidative and pro-inflammatory milieu within the carotid body (CB) is involved in the potentiation of CB chemosensory responses to hypoxia, which contribute to enhance the sympathetic activity. Accordingly, autonomic and cardiovascular alterations induced by CIH are critically dependent on an abnormally heightened CB chemosensory input to the nucleus of tractus solitarius (NTS), where second-order neurons project onto the rostral ventrolateral medulla (RVLM), activating pre-sympathetic neurons that control pre-ganglionic sympathetic neurons. CIH produces oxidative stress and neuroinflammation in the NTS and RVLM, which may contribute to the long-term irreversibility of the CIH-induced alterations. This brief review is mainly focused on the contribution of nitro-oxidative stress and pro-inflammatory molecules on the hyperactivation of the hypoxic chemoreflex pathway including the CB and the brainstem centres, and whether the persistence of autonomic and cardiorespiratory alterations may depend on the glial-related neuroinflammation induced by the enhanced CB chemosensory afferent input.

Desialylation of ATG5 by sialidase (NEU1) promotes macrophages autophagy and exacerbates inflammation under hypoxia

During the process of atherosclerosis (AS), hypoxia induces plaque macrophage inflammation, promoting lipid accumulation. Autophagy is a cell homeostasis process that increases tolerance to stressors like oxidative stress and hypoxia. However, the specific mechanism by which hypoxia initiates autophagy and the inflammation of macrophages remains to be elucidated. Here, we found that hypoxia-induced macrophage inflammation was mediated by autophagy. Then, the effect of hypoxia on autophagy was investigated in terms of post-translational modifications of proteins. The results showed that desialylation of the autophagy protein ATG5 under hypoxic conditions enhanced protein stability by affecting its charge effect and promoted the formation of the ATG5-ATG12-ATG16L complex, further increasing autophagosome formation. And NEU1, a key enzyme in sialic acid metabolism, was significantly up-regulated under hypoxic conditions and was identified as an interacting protein of ATG5, affecting the sialylation of ATG5. In addition, the knockdown or inhibition of NEU1 reversed hypoxia-induced autophagy and inflammatory responses. In conclusion, our data reveal a key mechanism of autophagy regulation under hypoxia involving ATG5 sialylation and NEU1, suggesting that NEU1 may be a potential target for the prevention and treatment of atherosclerosis.

Beyond the Lungs: O 2 Supplementation Improves Cerebral Oxygenation and Fatigue during Exercise in Interstitial Lung Disease

PURPOSE

Cerebral hypoxia may exacerbate the perception of fatigue. We previously demonstrated that exercise-related hypoxemia, a hallmark of fibrotic interstitial lung disease ( f -ILD), dose dependently impairs cerebral oxygenation in these patients. It is unknown whether normalizing cerebral oxygenation with O 2 supplementation would be associated with positive changes in a relevant patient-centered outcome during exercise in f -ILD, such as improved perceived fatigue.

METHODS

Fourteen patients (12 males, 72 ± 8 yr, 8 with idiopathic pulmonary fibrosis, lung diffusing capacity for carbon monoxide = 44% ± 13% predicted) performed a constant-load (60% peak work rate) cycle test to symptom limitation (Tlim) breathing medical air. Fourteen controls cycled up to Tlim of an age- and sex-matched patient. Patients repeated the test on supplemental O 2 (fraction of inspired O 2 = 0.41 ± 0.08) for the same duration. Near-infrared spectroscopy and the rating-of-fatigue (ROF) scale assessed prefrontal cortex oxygenation and perceived fatigue, respectively.

RESULTS

Patients showed severe exertional hypoxemia (Tlim O 2 saturation by pulse oximetry = 80% ± 8%); they had poorer cerebral oxygenation (e.g., oxy-deoxyhemoglobin difference [HbDiff] = -3.5 ± 4.7 [range = -17.6 to +1.9] vs +1.9 ± 1.7 μmol from rest) and greater fatigue (ROF = 6.2 ± 2.0 vs 2.6 ± 2.3) versus controls under air ( P < 0.001). Reversal of exertional hypoxemia with supplemental O 2 led to improved HbDiff (+1.7 ± 2.4 μmol from rest; no longer differing from controls) and lower ROF scores (3.7 ± 1.2, P < 0.001 vs air) in patients. There was a significant correlation between O 2 -induced changes in HbDiff and ROF scores throughout exercise in f -ILD ( rrepeated-measures correlation = -0.51, P < 0.001).

CONCLUSIONS

Supplemental O 2 improved cerebral oxygenation during exercise in f -ILD, which was moderately associated with lower ratings of perceived fatigue. Reversing cerebral hypoxia with O 2 supplementation may thus have positive effects on patients' disablement beyond those expected from lower ventilation and dyspnea in this patient population.

Association of obstructive sleep apnea with cardiometabolic diseases and cardiovascular mortality

BACKGROUND

Obstructive sleep apnea (OSA) is one of the leading respiratory disorders, increasing the risk of cardiometabolic diseases. In the study, we investigated the association between OSA and the risk of cardiometabolic diseases and all-cause and cardiovascular mortality in adults.

METHODS

Participants were enrolled in the National Health and Nutrition Examination Survey. The baseline covariates were compared between participants with and without OSA status. Multivariable logistic regression was performed to explore the association between OSA and cardiometabolic diseases, while Cox proportional regression was performed for all-cause and cardiovascular mortality.

RESULTS

OSA status was positively associated with higher risks of cardiometabolic diseases, including hypertension (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.14-1.45; p < 0.001), diabetes (OR 1.46, 95% CI 1.22-1.76; p < 0.001), and cardiovascular diseases (OR 1.29, 95% CI 1.08-1.54; p = 0.006) after adjusting for numerous covariates. However, no associations of OSA with all-cause or cardiovascular mortality were observed.

CONCLUSION

OSA was associated with a higher risk of hypertension, diabetes, and cardiovascular diseases, but had no significant association with all-cause or cardiovascular mortality in adults.

Efficacy of continuous positive airway pressure on NT-pro-BNP in obstructive sleep apnea patients: a meta-analysis

BACKGROUND

N-terminal probrain natriuretic peptide (NT-pro-BNP) and BNP are well-known markers for the diagnosis and prognostic of heart failure. Until now, it was not clear whether BNP levels are influenced by events occurring within Obstructive sleep apnea-hypopnea syndrome (OSAHS) with continuous positive airway pressure (CPAP).

METHODS

A thorough search in PubMed, EMBASE, Google Scholar, and Web of Science databases up to October 24, 2022, and a meta-analysis aimed to explore further accurate estimates of the effects of BNP on OSAHS after CPAP treatment to assess the strength of the evidence.

RESULTS

The forest plot outcome indicated that CPAP therapy did not change the BNP level in patients with OSAHS, with a weighted mean difference (WMD) of -0.47 (95% CI: -1.67 to 2.62; P = 0.53] based on the random effect model because of high significant heterogeneity (I² = 80%) among the studies. Subgroup analysis also explored the changes in BNP levels in patients with OSAHS. Begg's test (P = 0.835) and Egger's test (P = 0.245) suggested significant negative publication bias.

CONCLUSION

Our meta-analysis suggests that CPAP therapy does not change the BNP level in patients with OSAHS; therefore, it is not accurate to use BNP level as an index to evaluate heart function in patients with OSAHS, but more related research should be conducted.

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.

Relationship between severity of obstructive sleep apnea and benign prostatic hyperplasia

PURPOSE

The cause of benign prostatic hyperplasia (BPH) is controversial, local hypoxia and inflammation being the main two possibilities proposed. The aim of this study was to evaluate the relationship between obstructive sleep apnea (OSA) and BPH.

METHODS

The study cohort comprised men from January 2016 to December 2020 in our Sleep Center. These patients were classified into four groups (no, mild, moderate, severe OSA) by apnea-hypopnea indexes (AHI). Logistic regression was used to identify independent risk factors for BPH, after which participants were stratified into younger (age ≤ 40 years) and older groups (age > 40 years) for further analysis.

RESULTS

The study cohort comprised 467 patients including 135 younger subjects and 332 older subjects. The prevalence of BPH in the above listed AHI categories was 37.5%, 55.0%, 62.9%, and 52.3%, respectively (p = 0.075). Logistic regression analysis of all patients identified age as a risk factor for BPH (p < 0.001). Stratified analysis according to AHI category found a prevalence of BPH of 0.0%, 13.0%, 33.3%, and 43.9%, respectively, in younger group (p = 0.006), and 52.2%, 71.9%, 71.1%, and 56.3%, respectively, in older group (p = 0.038). Logistic regression analysis found age and AHI were independent risk factors for BPH in younger group (both p < 0.05), whereas only age was identified as a risk factor for BPH in older group (p < 0.001).

CONCLUSIONS

Age is an independent risk factor for BPH in men with OSA. AHI is also an independent risk factor for BPH in younger men, suggesting that OSA may affect development of BPH in younger men.

Adipocytokines in obstructive sleep apnea: A systematic review and meta-analysis

BACKGROUND AND AIM

Adipocytokines play an important role in obstructive sleep apnea (OSA) by mediating inflammatory responses. Previous studies have reported that OSA is related to a change in the serum levels of adipocytokines; however, the results are still controversial. This meta-analysis aimed to assess the relationship between OSA and circulating level of adipocytokines in adults and children.

METHODS

A comprehensive search was conducted in databases of Medline/PubMed and Scopus for pertinent articles published since their inception to July 2022. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were used to assess the strength of the relationship between the concentrations of adipocytokines with OSA.

RESULTS

In the overall analysis, contrary to IL-10, which showed a significant reduction, IL-1β, IL-4, IL-8, IL-17, and IFN- gamma showed higher levels in OSA patients in comparison with control groups (p <0.05). For adults, IL-1β, IL-8, IL-17, IL-18, vaspin, visfatin, and chemerin were linked to a greater serum levels in patients with OSA, while, IL-5 and IL-10 were detected significantly lower in adults with OSA in comparison with healthy adults (p <0.05). In children with OSA, the serum levels of IL-4, IL-8, IL-12, IL-17, IL-23, and IFN-gamma were significantly higher than healthy children (p <0.05).

CONCLUSION

The levels of inflammatory markers were found to be higher in OSA patients compared with control individuals, suggesting that adipocytokines may contribute to the pathology of OSA.

Efficacy of continuous positive airway pressure on TNF-α in obstructive sleep apnea patients: A meta-analysis

BACKGROUND

Tumor necrosis factor-α (TNF-α) is an important mediator of the immune response. At present, the improvement of TNF-α after continuous positive airway pressure (CPAP) treatment of obstructive sleep apnea-hypopnea syndrome (OSAHS) is still controversial.

METHODS

We conducted a systematic review of the present evidence based on a meta-analysis to elucidate the effects of TNF-α on OSAHS after CPAP treatment.

RESULTS

To measure TNF-α, ten studies used enzyme-linked immunosorbent assay (ELISA), and one used radioimmunoassay. The forest plot outcome indicated that CPAP therapy would lower the TNF-α levels in OSAHS patients, with a weighted mean difference (WMD) of 1.08 (95% CI: 0.62-1.55; P < 0.001) based on the REM since there is highly significant heterogeneity (I2 = 90%) among the studies. Therefore, we used the subgroup and sensitivity analyses to investigate the source of heterogeneity. The findings of the sensitivity analysis revealed that the pooled WMD ranged from 0.91 (95% CI: 0.52-1.31; P < 0.001) to 1.18 (95% CI: 0.74-1.63; P < 0.001). The findings were not influenced by any single study. Notably, there was homogeneity in the Asia subgroup and publication year: 2019, implying that these subgroups could be the source of heterogeneity.

CONCLUSION

Our meta-analysis recommends that CPAP therapy will decrease the TNF-α level in OSAHS patients, but more related research should be conducted.

A Wearable Functional Near-Infrared Spectroscopy (fNIRS) System for Obstructive Sleep Apnea Assessment

Obstructive sleep apnea (OSA), one of the most common sleep-related breathing disorders, contributes as a potentially life-threatening disease. In this paper, a wearable functional near-infrared spectroscopy (fNIRS) system for OSA monitoring is proposed. As a non-invasive system that can monitor oxygenation and cerebral hemodynamics, the proposed system is dedicated to mapping the pathogenic characteristics of OSA to dynamic changes in blood oxygen concentration and to constructing an automatic approach for assessing OSA. An algorithm including feature extraction, feature selection, and classification is proposed to signals. Permutation entropy(PE), for quantitative measuring the complexity of time series, is firstly involved to characterize the features of the physiological signals. Subsequently, the principal component analysis (PCA) for feature dimensionality reduction and support vector machine (SVM) algorithm for OSA classification are applied. The proposed method has been validated on a dataset that collected by the wearable system. It includes 40 subjects and composes of normal, and various severity cessation of breathing (e.g., mild, moderate, and severe). Experimental results exhibit that the proposed system can effectively distinguish OSA and non-OSA subjects, with an accuracy of 91.89%. The proposed system is expected to pave the novel perspective for OSA assessment in terms of cerebral hemodynamics.

2022 Brazilian Thoracic Association recommendations for long-term home oxygen therapy

Some chronic respiratory diseases can cause hypoxemia and, in such cases, long-term home oxygen therapy (LTOT) is indicated as a treatment option primarily to improve patient quality of life and life expectancy. Home oxygen has been used for more than 70 years, and support for LTOT is based on two studies from the 1980s that demonstrated that oxygen use improves survival in patients with COPD. There is evidence that LTOT has other beneficial effects such as improved cognitive function, improved exercise capacity, and reduced hospitalizations. LTOT is indicated in other respiratory diseases that cause hypoxemia, on the basis of the same criteria as those used for COPD. There has been an increase in the use of LTOT, probably because of increased life expectancy and a higher prevalence of chronic respiratory diseases, as well as greater availability of LTOT in the health care system. The first Brazilian Thoracic Association consensus statement on LTOT was published in 2000. Twenty-two years la-ter, we present this updated version. This document is a nonsystematic review of the literature, conducted by pulmonologists who evaluated scientific evidence and international guidelines on LTOT in the various diseases that cause hypoxemia and in specific situations (i.e., exercise, sleep, and air travel). These recommendations, produced with a view to clinical practice, contain several charts with information on indications for LTOT, oxygen sources, accessories, strategies for improved efficiency and effectiveness, and recommendations for the safe use of LTOT, as well as a LTOT prescribing model.

The impact of cerebral vasomotor reactivity on cerebrovascular diseases and cognitive impairment

The regulation of cerebral blood flow (CBF) is a complex and tightly controlled function ensuring delivery of oxygen and nutrients and removal of metabolic wastes from brain tissue. Cerebral vasoreactivity (CVR) refers to the ability of the nervous system to regulate CBF according to metabolic demands or changes in the microenvironment. This can be assessed through a variety of nuclear medicine and imaging techniques and protocols. Several studies have investigated the association of CVR with physiological and pathological conditions, with particular reference to the relationship with cognitive impairment and cerebrovascular disorders (CVD). A better understanding of the interaction between CVR and cognitive dysfunction in chronic and particularly acute CVD could help improving treatment and rehabilitation strategies in these patients. In this paper, we reviewed current knowledge on CVR alterations in the context of acute and chronic CVD and cognitive dysfunction. Alterations in CVR and hemodynamics have been described in patients with both neurodegenerative and vascular cognitive impairment, and the severity of these alterations seems to correlate with CVR derailment. Furthermore, an increased risk of cognitive impairment progression has been associated with alterations in CVR parameters and hemodynamics. Few studies have investigated these associations in acute cerebrovascular disorders and the results are inconsistent; thus, further research on this topic is encouraged.

Neurocognitive Consequences in Children with Sleep Disordered Breathing: Who Is at Risk?

Sleep-disordered breathing (SDB) is a prevalent disease in children characterized by snoring and narrowing of the upper airway leading to gas exchange abnormalities during sleep as well as sleep fragmentation. SDB has been consistently associated with problematic behaviors and adverse neurocognitive consequences in children but causality and determinants of susceptibility remain incompletely defined. Since the 1990s several studies have enlightened these associations and consistently reported poorer academic performance, lower scores on neurocognitive tests, and behavioral abnormalities in children suffering from SDB. However, not all children with SDB develop such consequences, and severity of SDB based on standard diagnostic indices has often failed to discriminate among those children with or without neurocognitive risk. Accordingly, a search for discovery of markers and clinically useful tools that can detect those children at risk for developing cognitive and behavioral deficits has been ongoing. Here, we review the advances in this field and the search for possible detection approaches and unique phenotypes of children with SDB who are at greater risk of developing neurocognitive consequences.

Effects of Intermittent Hypoxia-Hyperoxia Exposure Prior to Aerobic Cycling Exercise on Physical and Cognitive Performance in Geriatric Patients—A Randomized Controlled Trial

Background: It was recently shown that intermittent hypoxic-hyperoxic exposure (IHHE) applied prior to a multimodal training program promoted additional improvements in cognitive and physical performance in geriatric patients compared to physical training only. However, there is a gap in the literature to which extent the addition of IHHE can enhance the effects of an aerobic training. Therefore, the aim of this study was to investigate the efficacy of IHHE applied prior to aerobic cycling exercise on cognitive and physical performance in geriatric patients.

Methods: In a randomized, two-armed, controlled, and single-blinded trial, 25 geriatric patients (77–94 years) were assigned to two groups: intervention group (IG) and sham control group (CG). Both groups completed 6 weeks of aerobic training using a motorized cycle ergometer, three times a week for 20 min per day. The IG was additionally exposed to intermittent hypoxic and hyperoxic periods for 30 min prior to exercise. The CG followed the similar procedure breathing sham hypoxia and hyperoxia (i.e., normoxia). Within 1 week before and after the interventions, cognitive performance was assessed with the Dementia-Detection Test (DemTect) and the Clock Drawing Test (CDT), while physical performance was measured using the Timed “Up and Go” Test (TUG) and the Short-Physical-Performance-Battery (SPPB).

Results: No interaction effect was found with respect to the DemTect (η_p² = 0.02). An interaction effect with medium effect size (η_p² = 0.08) was found for CDT performance with a higher change over time for IG (d = 0.57) compared to CG (d = 0.05). The ANCOVA with baseline-adjustment indicated between-group differences with a large and medium effect size at post-test for the TUG (η_p² = 0.29) and SPPB (η_p² = 0.06) performance, respectively, in favour of the IG. Within-group post-hoc analysis showed that the TUG performance was worsened in the CG (d = 0.65) and remained unchanged in the IG (d = 0.19). Furthermore, SPPB performance was increased (d = 0.58) in IG, but no relevant change over time was found for CG (d = 0.00).

Conclusion: The current study suggests that an additional IHHE prior to aerobic cycling exercise seems to be more effective to increase global cognitive functions as well as physical performance and to preserve functional mobility in geriatric patients in comparison to aerobic exercise alone after a 6-week intervention period.

Effects of Intermittent Hypoxia in Training Regimes and in Obstructive Sleep Apnea on Aging Biomarkers and Age-Related Diseases: A Systematic Review

Several studies have assessed the effects of intermittent hypoxia-normoxia training (IHNT), intermittent hypoxia-hyperoxia training (IHHT), and obstructive sleep apnea (OSA) on aging and age-related diseases in humans; however, the results remain contradictory. Therefore, this review aims to systematically summarize the available studies on the effects of IHNT, IHHT, and OSA on aging and age-related diseases. Relevant studies were searched from PubMed, Google Scholar, Cochrane Library databases, and through manual searching from reference lists of eligible studies. A total of 38 eligible studies were included in this systematic review. IHHT and IHNT provide positive effects on several age-related parameters including quality of life, cognitive and physical functions, plasma level of glucose and cholesterol/LDL, systolic blood pressure, red blood cells, and inflammation. Moreover, moderate intermittent hypoxia induces telomerase reverse transcriptase (TERT) activity and telomere stabilization, delays induction of senescence-associated markers expression and senescence-associated β-galactosidase, upregulates pluripotent marker (Oct4), activates a metabolic shift, and raises resistance to pro-apoptotic stimuli. On the contrary, intermittent hypoxia in OSA causes hypertension, metabolic syndrome, vascular function impairment, quality of life and cognitive scores reduction, advanced brain aging, increase in insulin resistance, plasma hydrogen peroxide, GSH, IL-6, hsCRP, leptin, and leukocyte telomere shortening. Thus, it can be speculated that the main factor that determines the direction of the intermittent hypoxia action is the intensity and duration of exposure. There is no direct study to prove that IHNT/IHHT actually increases life expectancy in humans. Therefore, further study is needed to investigate the actual effect of IHNT/IHHT on aging in humans.

Systematic Review Registration

www.crd.york.ac.uk/prospero, identifier CRD42022298499.

Neurobehavioral morbidity of pediatric mild sleep-disordered breathing and obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea is associated with neurobehavioral dysfunction, but the relationship between disease severity as measured by the apnea-hypopnea index and neurobehavioral morbidity is unclear. The objective of our study is to compare the neurobehavioral morbidity of mild sleep-disordered breathing versus obstructive sleep apnea.

METHODS

Children 3-12 years old recruited for mild sleep-disordered breathing (snoring with obstructive apnea-hypopnea index < 3) into the Pediatric Adenotonsillectomy Trial for Snoring were compared to children 5-9 years old recruited for obstructive sleep apnea (obstructive apnea-hypopnea 2-30) into the Childhood Adenotonsillectomy Trial. Baseline demographic, polysomnographic, and neurobehavioral outcomes were compared using univariable and multivariable analysis.

RESULTS

The sample included 453 participants with obstructive sleep apnea (median obstructive apnea-hypopnea index 5.7) and 459 participants with mild sleep-disordered breathing (median obstructive apnea-hypopnea index 0.5). By polysomnography, participants with obstructive sleep apnea had poorer sleep efficiency and more arousals. Children with mild sleep-disordered breathing had more abnormal executive function scores (adjusted odds ratio 1.96, 95% CI 1.30-2.94) compared to children with obstructive sleep apnea. There were also elevated Conners scores for inattention (adjusted odds ratio 3.16, CI 1.98-5.02) and hyperactivity (adjusted odds ratio 2.82, CI 1.83-4.34) in children recruited for mild sleep-disordered breathing.

CONCLUSIONS

Abnormal executive function, inattention, and hyperactivity were more common in symptomatic children recruited into a trial for mild sleep-disordered breathing compared to children recruited into a trial for obstructive sleep apnea. Young, snoring children with only minimally elevated apnea-hypopnea levels may still be at risk for deficits in executive function and attention.

TRIAL REGISTRATION

Pediatric Adenotonsillectomy for Snoring (PATS), NCT02562040; Childhood Adenotonsillectomy Trial (CHAT), NCT00560859.

The role of hypoxia-inducible factors in cardiovascular diseases

Cardiovascular diseases are the leading cause of death worldwide. During the development of cardiovascular diseases, hypoxia plays a crucial role. Hypoxia-inducible factors (HIFs) are the key transcription factors for adaptive hypoxic responses, which orchestrate the transcription of numerous genes involved in angiogenesis, erythropoiesis, glycolytic metabolism, inflammation, and so on. Recent studies have dissected the precise role of cell-specific HIFs in the pathogenesis of hypertension, atherosclerosis, aortic aneurysms, pulmonary arterial hypertension, and heart failure using tissue-specific HIF-knockout or -overexpressing animal models. More importantly, several compounds developed as HIF inhibitors or activators have been in clinical trials for the treatment of renal cancer or anemia; however, little is known on the therapeutic potential of these inhibitors for cardiovascular diseases. The purpose of this review is to summarize the recent advances on HIFs in the pathogenesis and pathophysiology of cardiovascular diseases and to provide evidence of potential clinical therapeutic targets.

LncRNA XR_596701 protects H9c2 cells against intermittent hypoxia-induced injury through regulation of the miR-344b-5p/FAIM3 axis

Long noncoding RNAs (lncRNAs) participate in various biological processes and cardiovascular diseases. Recently, a novel lncRNA XR_596701 was found to be differentially expressed in obstructive sleep apnea (OSA)-induced myocardial tissue compared to normal myocardial tissues. However, the pathological effect and regulatory mechanism of XR_596701 in intermittent hypoxia (IH)-mediated cardiomyocytes damage have not been studied. The subcellular localization of XR_596701 was determined by fluorescence in situ hybridization (FISH). Gene expressions of XR_596701 and miR-344b-5p were detected by quantitative real-time polymerase chain reaction (qRT-PCR) in IH-induced H9c2 cells. Cell proliferation was measured by 5-ethynyl-2′-deoxyuridine (EdU) staining assay. Cell apoptosis was detected by Hoechst 33342/PI staining and immunofluorescence (IF). Apoptotic protein of H9c2 cells was measured by western blot. The direct interaction between XR_596701 and miR-344b-5p as well as miR-344b-5p and Fas apoptotic inhibitory molecule 3 (FAIM3) were examined using dual-luciferase reporter assay. The significance of XR_596701 and miR-344b-5p on cell proliferation and apoptosis was evaluated by using gain-of-function and loss-of-function approaches. XR_596701 was upregulated, while miR-344b-5p downregulated in IH-induced H9c2 cells. Functionally, suppression of XR_596701 and overexpression of miR-344b-5p inhibited cell proliferation and promoted cell apoptosis in H9c2 cells. The roles of XR_596701 were achieved by sponging miR-344b-5p. And the function of miR-344b-5p was reversed by targeting FAIM3. Additionally, FAIM3 mediated IH-induced H9c2 cells damage by XR_596701. XR_596701 was serve as a novel lncRNA that indicated protective roles on proliferation and apoptosis of IH-induced H9c2 cells through the miR-344b-5p/FAIM3 axis.

Sleep-Disordered Breathing is frequently associated with idiopathic normal pressure hydrocephalus but not other types of hydrocephalus

STUDY OBJECTIVES

Previous studies have shown sleep-disordered breathing (SDB) to be highly prevalent in patients with idiopathic normal pressure hydrocephalus (iNPH). The current study aimed to estimate and compare the prevalence of SDB in patients with different types of hydrocephalus and test if SDB was associated with changed CO2.

METHODS

We investigated the prevalence of SDB in a prospective cohort of 48 hydrocephalus patients with nocturnal polysomnography (PSG). Twenty-three of the patients also had simultaneous CO2 measurements.

RESULTS

The prevalence of SDB was high in patients with iNPH, with moderate-to-severe SDB in 21/22 (96%) of the patients and an apnea-hypopnea index (AHI) of 43.5 (95% CI 33.8-52.2). Patients with pediatric-onset hydrocephalus had moderate-to-severe SDB in 7/16 (44%), with an AHI of 16.1 (95% CI 8.16-23.8). Except for one patient, all patients with adult-onset obstructive hydrocephalus (9/10) had normal respiration or mild SDB with an AHI of 8.4 (95% CI 5.5-10.5). None of the 23 patients measured with CO2 had elevated CO2 associated with SDB and had normal CO2 during sleep, with 40.8 ± 5.5 mmHg, 42.7 ± 4.1 mmHg, 34.5-45.8 mmHg for patients with iNPH, pediatric-onset, and adult-onset, respectively.

CONCLUSION

We found a high prevalence of SDB in patients with iNPH, confirming previous findings. We extended this with the finding that the prevalence of SDB in patients with other types of hydrocephalus is not significantly different from that in the general population. Additionally, we did not find elevations of CO2 associated with SDB or CO2 retention during sleep.

CO2-induced intracranial hypertension and high-amplitude B-waves in a patient with Chiari 1 malformation and sleep apnea syndrome that resolved following CPAP therapy

Headaches and cognitive impairment in the elderly population have been described as symptoms related to obstructive sleep apnea (OSA). Although papilledema has been observed in some of these patients, suggesting intracranial hypertension (ICH), there are only a few studies in which intracranial pressure (ICP) has been continuously measured in patients with OSA without neurological disease. We present a patient diagnosed with Chiari Type 1 malformation and OSA, who present normal ICP recording during the day and nocturnal ICH associated with high amplitude B-waves and hypercapnia during obstructive apneas, which disappeared following continuous positive airway pressure (CPAP) therapy. The normalization of the cerebral and respiratory parameters with CPAP therapy is important for performing the correct treatment in these patients.

Impact of intermittent hypoxia on human vascular responses during sleep

Exposure to intermittent hypoxia (IH) ≥15 times per hour is believed to be the primary mechanism for the increased risk of cerebrovascular and cardiovascular disease in patients with moderate to severe sleep apnea. Human experimental models of IH used to investigate this link have been predominantly employed during wakefulness, which limits extrapolation of findings to sleep apnea where IH occurs during sleep. Moreover, how IH impacts vascular regulation during sleep has not been measured quantitatively. Therefore, the objective of this study was to assess the impact sleep accompanied by IH on vascular responses to hypoxia and hypercapnia during sleep. Ten males performed two randomly scheduled 6-h overnight sleep studies. One sleep study was performed in room air (normoxia) and the other sleep study was performed during isocapnic IH (60 s hypoxia-60 s normoxia). On each night, cerebrovascular (peak blood velocity through the middle cerebral artery (V¯_P); transcranial Doppler ultrasound) and cardiovascular (blood pressure, heart rate) responses to hypoxia and hypercapnia were measured before sleep onset (PM-Awake), within the first 2 h of sleep (PM-Asleep), in the 5th (out of 6) hours of sleep (AM-Asleep) and after being awoken in the morning (AM-Awake). Sleep accompanied by IH had no impact on the V¯_P and blood pressure responses to hypoxia and hypercapnic at any timepoint (p ≥ 0.103 for all responses). However, the AM-Awake heart rate response to hypoxia was greater following sleep in IH compared to sleep in normoxia. Independent of the sleep environment, the V¯_P response to hypoxia and hypercapnia were reduced during sleep. In conclusion, cerebral blood flow responses are reduced during sleep compared to wakefulness, but 6 h of sleep accompanied by IH does not alter cerebrovascular and cardiovascular response to hypoxia and hypercapnia during wakefulness or sleep in healthy young humans. However, it is likely that longer exposure to IH during sleep (i.e., days-to-weeks) is required to better elucidate IH's impact on vascular regulation in humans.

Neuropeptide Y: An Update on the Mechanism Underlying Chronic Intermittent Hypoxia-Induced Endothelial Dysfunction

Endothelial dysfunction (ED) is a core pathophysiological process. The abnormal response of vascular endothelial (VE) cells to risk factors can lead to systemic consequences. ED caused by intermittent hypoxia (IH) has also been recognized. Neuropeptide Y (NPY) is an important peripheral neurotransmitter that binds to different receptors on endothelial cells, thereby causing ED. Additionally, hypoxia can induce the release of peripheral NPY; however, the involvement of NPY and its receptor in IH-induced ED has not been determined. This review explains the definition of chronic IH and VE function, including the relationship between ED and chronic IH-related vascular diseases. The results showed that that the effect of IH on VE injury is mediated by the VE-barrier structure and endothelial cell dysfunction. These findings offer new ideas for the prevention and treatment of obstructive sleep apnea syndrome and its complications.

Impact of nocturnal oxygen and CPAP on the ventilatory response to hypoxia in OSA patients free of overt cardiovascular disease

A primary characteristic of obstructive sleep apnea (OSA) is chronic exposure to intermittent hypoxia (IH) due to repeated upper airway obstruction. Chronic IH exposure is believed to increase OSA severity over time by enhancing the acute ventilatory response to hypoxia (AHVR), thus promoting ventilatory overshoot when apnea ends and perpetuation of apnea during sleep. Continuous positive airway pressure (CPAP), the gold-standard treatment of OSA, reduces the AHVR, believed to result from correction of IH. However, CPAP also corrects ancillary features of OSA such as intermittent hypercapnia, negative intrathoracic pressure and surges in sympathetic activity, which may also contribute to the reduction in AHVR. Therefore, the objective of this study was to investigate the impact of nocturnal oxygen therapy (to remove IH only) and CPAP (to correct IH and ancillary features of OSA) on AHVR in newly diagnosed OSA patients. Fifty-two OSA patients and twenty-two controls were recruited. The AHVR was assessed using a 5 min iscopanic-hypoxic challenge before, and after, treatment of OSA by nocturnal oxygen therapy and CPAP. Following baseline measurements, OSA patients were randomly assigned to nocturnal oxygen therapy (Oxygen, n = 26) or no treatment (Air; n = 26). The AHVR was re-assessed following two weeks of oxygen therapy or no treatment, after which all patients were treated with CPAP. The AHVR was quantified following ~4 weeks of adherent CPAP therapy (n = 40). Both nocturnal oxygen and CPAP treatments improved hypoxemia (p < 0.05), and, as expected, nocturnal oxygen therapy did not completely abolish respiratory events (i.e., apneas/hypopneas). Averaged across all OSA patients, nocturnal oxygen therapy did not change AHVR from baseline to post-oxygen therapy. Similarly, the AHVR was not altered pre- and post-CPAP (p > 0.05). However, there was a significant decrease in AHVR with both nocturnal oxygen therapy and CPAP in patients in the highest OSA severity quartile (p < 0.05). Nocturnal oxygen therapy and CPAP both reduce the AHVR in patients with the most severe OSA. Therefore, IH appears to be the primary mechanism producing ventilatory instability in patients with severe OSA via enhancement of the AHVR.

Hypoxia and brain aging: Neurodegeneration or neuroprotection?

The absolute reliance of the mammalian brain on oxygen to generate ATP renders it acutely vulnerable to hypoxia, whether at high altitude or in clinical settings of anemia or pulmonary disease. Hypoxia is pivotal to the pathogeneses of myriad neurological disorders, including Alzheimer's, Parkinson's and other age-related neurodegenerative diseases. Conversely, reduced environmental oxygen, e.g. sojourns or residing at high altitudes, may impart favorable effects on aging and mortality. Moreover, controlled hypoxia exposure may represent a treatment strategy for age-related neurological disorders. This review discusses evidence of hypoxia's beneficial vs. detrimental impacts on the aging brain and the molecular mechanisms that mediate these divergent effects. It draws upon an extensive literature search on the effects of hypoxia/altitude on brain aging, and detailed analysis of all identified studies directly comparing brain responses to hypoxia in young vs. aged humans or rodents. Special attention is directed toward the risks vs. benefits of hypoxia exposure to the elderly, and potential therapeutic applications of hypoxia for neurodegenerative diseases. Finally, important questions for future research are discussed.

The effect of chronic intermittent hypoxia in cardiovascular gene expression is modulated by age in a mice model of sleep apnea

STUDY OBJECTIVES

Chronic intermittent hypoxia (CIH) is a major determinant in obstructive sleep apnea cardiovascular morbidity and this effect is influenced by age. The objective of the present study was to assess the differential molecular mechanisms at gene-level expression involved in the cardiovascular remodeling induced by CIH according to chronological age.

METHODS

Two- and 18-month-old mice (N = 8 each) were subjected to CIH or normoxia for 8 weeks. Total messenger RNA (mRNA) was extracted from left ventricle myocardium and aortic arch, and gene expression of 46 intermediaries of aging, oxidative stress, and inflammation was measured by quantitative real-time polymerase chain reaction.

RESULTS

Cardiac gene expression of Nrf2 (2.05-fold increase, p < 0.001), Sod2 (1.9-fold increase, p = 0.035), Igf1r (1.4-fold increase, p = 0.028), Mtor (1.8-fold increase, p = 0.06), Foxo3 (1.5-fold increase, p = 0.020), Sirt4, Sirt6, and Sirt7 (1.3-fold increase, p = 0.012; 1.1-fold change, p = 0.031; 1.3-fold change, p = 0.029) was increased after CIH in young mice, but not in old mice. In aortic tissue, endothelial isoform of nitric oxide synthase was reduced in young mice (p < 0.001), Nrf2 was reduced in 80% (p < 0.001) in young mice and 45% (p = 0.07) in old mice, as its downstream antioxidant target Sod2 (82% reduced, p < 0.001). IL33.

CONCLUSIONS

CIH effect in gene expression is organ-dependent, and is modulated by age. CIH increased transcriptional expression of genes involved in cardioprotection and cell survival in young, but not in old mice. In aortic tissue, CIH reduced gene expression related to an antioxidant response in both young and old mice, suggesting vascular oxidative stress and a proaging process.

Relevance of obstructive sleep apnea and smoking: Obstructive sleep apnea and smoking

BACKGROUND

The data concerning the association of smoking and obstructive sleep apnea (OSA) are limited. The effects of cigarette smoking on OSA still remain obscure.

OBJECTIVES

To reveal the impact of smoking on obstructive sleep apnea.

METHODS

About 384 patients with the diagnosis of OSA through full night polysomnographic (PSG) examination were included to the study. The demographic data (age, sex and BMI), complaints and medical history, status of smoking as non-smokers and smokers, smoking frequency (cigarettes/day), polysomnograhic data comprising apnea hypopnea index (AHI), non-REM sleep AHI (NREM AHI), REM sleep AHI (REM AHI), minimum oxygen saturation (min SaO2) were recorded for all the subjects. Non-smokers and smokers were compared in terms of severity of OSA.

RESULTS

The study population consisted of 384 subjects, 253 males and 131 females. Smoking frequency was not found correlated with OSA severity. Among smokers, males had higher severe OSA rate (P = 0.002, P < 0.05). In subjects with BMI < 30, severe OSA rate was higher in smokers (34.44% versus 21%) (P = 0.027, P < 0.05).

CONCLUSIONS

Our study detected higher rate of severe OSA in male smokers and smokers with BMI < 30. PSG data did not yield statistically significant difference in non-smokers and smokers. OSA severity was not found correlated with smoking frequency. Along with the study results, the impact of smoking on OSA is still controversial. Prospective studies with larger sample size may be contributive to further evaluation of the association of OSA with smoking.

Association Between Intermittent Hypoxia and Left Ventricular Remodeling in Patients With Obstructive Sleep Apnea-Hypopnea Syndrome

The present study was undertaken to examine the association between intermittent hypoxia and left ventricular (LV) remodeling and explore which parameter of intermittent hypoxia is most relevant to LV remodeling in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). Two hundred eighty six patients underwent polysomnographic examination were enrolled. Based on apnea-hypoxia index (AHI), patients were divided into no, mild, moderate and severe OSAHS groups. Between-group differences in LV remodeling and the association between parameters of intermittent hypoxia and LV remodeling was evaluated. Patients with severe OSAHS were more likely to have hypertension, and higher values of LV mass (LVM) and LVM index (LVMI). In univariate regression analysis, male, body mass index (BMI), systolic and diastolic blood pressure (BP), statins, antihypertensive drugs, creatinine, and parameters of intermittent hypoxia (AHI, obstructive apnea index [OAI], lowest oxygen saturation [LSpO₂], oxygen desaturation index [ODI], time spent below oxygen saturation of 90% [TS90%], and mean nocturnal oxygen saturation [MSpO₂]) were associated with LVMI. After multivariate regression analyses, only male gender, BMI, systolic BP, creatinine, and ODI remained significantly associated with LVMI. Compared to those without LV hypertrophy (LVH), patients with LVH had higher ODI. Compared to patients with normal LV, concentric remodeling and eccentric LVH, those with concentric LVH had higher ODI. In conclusion, intermittent hypoxia was significantly associated with left ventricular remodeling; and among various parameters of intermittent hypoxia, ODI was the most relevant to LV remodeling.

Circulating exosomes and gut microbiome induced insulin resistance in mice exposed to intermittent hypoxia: Effects of physical activity

Background

Gut microbiota (GM) contribute to obesity and insulin resistance (IR). Obstructive sleep apnea (OSA), characterized by intermittent hypoxia (IH), promotes IR and alters GM. Since circulating exosomes are implicated in IR, we examined the effects of IH and physical activity (PA) in mice on GM, colonic epithelium permeability, systemic IR, and plasma exosome cargo, and exosome effects on visceral white adipose tissues (vWAT) IR.

Methods

C57BL/6 mice were exposed to IH or room air (RA) for 6 weeks with and without PA (n = 12/group), and GM and systemic IR changes were assessed, as well as the effects of plasma exosomes on naïve adipocyte insulin sensitivity. Fecal microbiota transfers (FMT) were performed in naïve mice (n = 5/group), followed by fecal 16S rRNA sequencing, and systemic IR and exosome-induced effects on adipocyte insulin sensitivity were evaluated.

Findings

Principal coordinate analysis (PCoA) ordinates revealed B-diversity among IH and FMT recipients that accounted for 64% principal component 1 (PC1) and 12.5% (PC2) of total variance. Dominant microbiota families and genera in IH-exposed and FMT-treated were preserved, and IH-exposed GM and IH-FMT induced increased gut permeability. Plasma exosomes from IH-exposed and IH-FMT mice decreased pAKT/AKT responses to exogenous insulin in adipocytes vs. IH+PA or RA FMT-treated mice (p = 0.001).

Interpretation

IH exposures mimicking OSA induce changes in GM, increase gut permeability, and alter plasma exosome cargo, the latter inducing adipocyte dysfunction (increased IR). Furthermore, these alterations improved with PA. Thus, IH leads to perturbations of a singular GM-circulating exosome pathway that disrupts adipocyte homeostasis resulting in metabolic dysfunction, as reflected by IR.

Funding

This study was supported by grants from the National Institutes of Health grants HL130984 and HL140548 and University of Missouri Tier 2 grant. The study has not received any funding or grants from pharmaceutical or other industrial corporations.

Impact of mandibular advancement device therapy on cerebrovascular reactivity in patients with carotid atherosclerosis combined with OSAHS

PURPOSE

Obstructive sleep apnea-hypopnea syndrome (OSAHS) may affect cerebrovascular reactivity (CVR), representing cerebrovascular endothelial function, through complex cerebral functional changes. This study aimed to evaluate the change of CVR after 1-month and 6-month mandibular advancement device (MAD) treatment of patients with carotid atherosclerosis (CAS) combined with OSAHS.

METHODS

Patients with carotid atherosclerosis combined with OSAHS who voluntarily accepted Silensor-IL MAD therapy were prospectively enrolled. All patients underwent polysomnographic (PSG) examinations and CVR evaluation by breath-holding test using transcranial Doppler ultrasound at baseline (T0), 1 month (T1), and 6 months (T2) of MAD treatment.

RESULTS

Of 46 patients (mean age 54.4 ± 12.4 years, mean body mass index [BMI] 27.5 ± 4.5 kg/m²), 41 patients (responsive group) responded to the 1-month and 6-month treatment of MAD, an effective treatment rate of 89%. The remaining 5 patients (non-responsive group) were younger (47.4 ± 13.5 years) and had a higher BMI (35.8 ± 1.8 kg/m²). The responsive group had an improvement of apnea-hypopnea index (AHI) (events/h) from 33.0 ± 25.0 (T0) to 12.4 ± 10.4 (T1) and 8.7 ± 8.8 (T2), P < 0.001; minimum arterial oxygen saturation (minSpO₂) (%) increased from 79.8 ± 9.1 (T0) to 81.8 ± 9.4 (T1) and 85.2 ± 5.4 (T2), P < 0.01; longest apnea (LA) (s) decreased from 46.5 ± 23.1 (T0) to 33.3 ± 22.7 (T1) and 29.4 ± 18.5 (T2), P < 0.001; T90 (%) decreased from 10.3 ± 14.9 (T0) to 6.1 ± 11.8 (T1) and 3.3 ± 7.5 (T2), P < 0.05. Sleep architecture of these patients also improved significantly. The responsive group had a significant increase in left, right, and mean breath-holding index (BHI): left BHI(/s) from 0.52 ± 0.42 (T0) to 0.94 ± 0.56 (T1) and 1.04 ± 0.64 (T2), P < 0.01; right BHI(/s) from 0.60 ± 0.38 (T0) to 1.01 ± 0.58 (T1) and 1.11 ± 0.60 (T2), P < 0.01; mean BHI(/s) from 0.56 ± 0.38 (T0) to 0.97 ± 0.55 (T1) and 1.07 ± 0.59 (T2), P < 0.01), suggesting improved CVR.

CONCLUSION

Effective MAD therapy is beneficial for restoring cerebrovascular endothelial function in patients with CAS and OSAHS in a short period (1 month and 6 months).

TRIAL REGISTRATION

Clinical trial registration number: NCT03665818. September 11, 2018.

Recognizable Clinical Subtypes of Obstructive Sleep Apnea After Ischemic Stroke: A Cluster Analysis

BACKGROUND AND PURPOSE

Obstructive sleep apnea (OSA) increases risk of stroke recurrence and mortality in ischemic stroke patients. However, equivocal treatment effects warrant further categorization of post-stroke OSA for risk stratification and individualized treatment planning.

METHODS

The study recruited 232 ischemic stroke patients with moderate-to-severe OSA admitted for inpatient rehabilitation consecutively. Latent class analysis was performed based on sex, age, smoking, daytime sleepiness, depression, obesity, sedative use, atrial fibrillation, diabetes, dyslipidemia, hypertension, recurrent stroke and dysphagia. The augmentation index, a marker of arterial stiffness, was measured by applanation tonometry.

RESULTS

A three-cluster model provided the best fit. Cluster 1 (n=84, 36.2%) was older in age, predominantly female, with the highest hypopnea index and prevalence of atrial fibrillation. Moreover, patients in Cluster 1 had significantly higher augmentation index than those in Cluster 2. Cluster 2 patients (N=80, 34.5%) were of older age, predominantly male, with the highest prevalence of depression, the lowest prevalence of hypertension and had the most normal body mass index (BMI). Additionally, Cluster 2 had less nocturnal hypoxia as compared to Cluster 3. Cluster 3 (n=68, 29.3%) was the youngest in age, predominantly male, with the highest BMI, cumulative risk score, and prevalence of dyslipidemia of the three clusters.

CONCLUSION

Post-stroke OSA can be categorized into three clinical phenotypes. Patients in Clusters 1 and 3 both had elevated cardiovascular risk and treatment can be based on their distinct characteristics. Patients in Cluster 2 had relatively lower risk of cardiovascular events and the benefits of OSA treatment requires further study.

A Review of Cerebral Hemodynamics During Sleep Using Near-Infrared Spectroscopy

Investigating cerebral hemodynamic changes during regular sleep cycles and sleep disorders is fundamental to understanding the nature of physiological and pathological mechanisms in the regulation of cerebral oxygenation during sleep. Although sleep neuroimaging methods have been studied and have been well-reviewed, they have limitations in terms of technique and experimental design. Neurologists are convinced that Near-infrared spectroscopy (NIRS) provides essential information and can be used to assist the assessment of cerebral hemodynamics, and numerous studies regarding sleep have been carried out based on NIRS. Thus, a brief historical overview of the sleep studies using NIRS will be helpful for the biomedical students, academicians, and engineers to better understand NIRS from various perspectives. In this study, the existing literature on sleep studies is reviewed, and an overview of the NIRS applications is synthesized and provided. The paper first reviews the application scenarios, as well as the patterns of fluctuation of NIRS, which includes the investigation in regular sleep and sleep-disordered breathing. Various factors such as different sleep stages, populations, and degrees of severity were considered. Furthermore, the experimental design and signal processing, as well as the regulation mechanisms involved in regular and pathological sleep, are investigated and discussed. The strengths and weaknesses of the existing NIRS applications are addressed and presented, which can direct further NIRS analysis and utilization.

Risk of obstructive sleep apnea in patients with schizophrenia: a nationwide population-based cohort study

PURPOSE

Patients with schizophrenia (SCZ) have a higher prevalence of known risk factors for obstructive sleep apnea (OSA). This study aims to determine if SCZ patients are at increased risk of incident OSA.

METHODS

A total of 5092 newly diagnosed SCZ patients and 5092 non-SCZ controls matched by gender, age, and index year were included between 2000 and 2012 and followed to 2013. Participants newly diagnosed with OSA were defined as incidents. Cox regression analysis was used to calculate the hazard ratio (HR) with 95% confidence intervals (CI) of the OSA incidence rate between the two groups studied.

RESULTS

SCZ patients were at increased risk of OSA compared to non-SCZ controls after adjusting for gender, age, comorbidities, and duration of antipsychotic use (2.12 versus 1.01 per 1000 person-years, HR: 1.97, 95% CI: 1.36-2.85). Also, this study confirmed the existence of some known risk factors for OSA, including male gender (HR 1.65, 95% CI 1.14-2.37), obesity (HR 2.62, 95% CI 1.19-5.80), hypertension (HR 1.61, 95% CI 1.06-2.47), hyperlipidemia (HR 1.55, 95% CI 1.04-2.38), diabetes (HR 1.53, 95% CI 1.01-2.38), and antipsychotic use (duration < 1 year (HR 1.57, 95% CI 1.13-2.37), 1-3 years (HR 1.62, 95% CI 1.06-2.82), and 3-5 years (HR 1.45, 95% CI 1.06-2.44)).

CONCLUSION

This study shows SCZ patients are at increased risk of OSA, and there is still an association with higher risk of OSA after controlling for known risk factors, indicating that it is necessary to develop targeted interventions in SCZ patients to reduce the negative impact of OSA on health.

Effects of SARS-CoV-2 and its functional receptor ACE2 on the cardiovascular system

The clinical manifestations of COVID-19 are mainly respiratory symptoms, but some patients present with cardiovascular system disease such as palpitations and shortness of breath as the first or secondary symptoms. In this paper, we describe the characteristics of SARS-CoV‑2 and its functional receptor angiotensin-converting enzyme 2 (ACE2). Furthermore, we explore the impact of virus-induced myocardial damage, decreased ACE2 activity, immune imbalance, hypoxemia, and heart damage caused by antiviral drugs.

Polysomnographic phenotyping of obstructive sleep apnea and its implications in mortality in Korea

Conventionally, apnea–hypopnea index (AHI) is used to define and categorize the severity of obstructive sleep apnea. However, routine polysomnography (PSG) includes multiple parameters for assessing the severity of obstructive sleep apnea. The goal of this study is to identify and categorize obstructive sleep apnea phenotypes using unsupervised learning methods from routine PSG data. We identified four clusters from 4,603 patients by using 29 PSG variable and arranged according to their mean AHI. Cluster 1, spontaneous arousal (mean AHI = 8.52/h); cluster 2, poor sleep and periodic limb movements (mean AHI = 12.16/h); cluster 3, hypopnea (mean AHI = 38.60/h); and cluster 4, hypoxia (mean AHI = 69.66/h). Conventional obstructive sleep apnea classification based on apnea–hypopnea index severity showed no significant difference in cardiovascular or cerebrovascular mortality (Log rank P = 0.331), while 4 clusters showed an overall significant difference (Log rank P = 0.009). The risk of cardiovascular or cerebrovascular mortality was significantly increased in cluster 2 (hazard ratio = 6.460, 95% confidence interval 1.734–24.073) and cluster 4 (hazard ratio = 4.844, 95% confidence interval 1.300–18.047) compared to cluster 1, which demonstrated the lowest mortality. After adjustment for age, sex, body mass index, and underlying medical condition, only cluster 4 showed significantly increased risk of mortality compared to cluster 1 (hazard ratio = 7.580, 95% confidence interval 2.104–34.620). Phenotyping based on numerous PSG parameters gives additional information on patients’ risk evaluation. Physicians should be aware of PSG features for further understanding the pathophysiology and personalized treatment.

Reinventing polysomnography in the age of precision medicine

For almost 50 years, sleep laboratories around the world have been collecting massive amounts of polysomnographic (PSG) physiological data to diagnose sleep disorders, the majority of which are not utilized in the clinical setting. Only a small fraction of the information available within these signals is utilized to generate indices. For example, the apnea-hypopnea index (AHI) remains the primary tool for diagnostic and therapeutic decision-making for obstructive sleep apnea (OSA) despite repeated studies showing it to be inadequate in predicting clinical consequences. Today, there are many novel approaches to PSG signals, making it possible to extract more complex metrics and analyses that are potentially more clinically relevant for individual patients. However, the pathway to implement novel PSG metrics/analyses into routine clinical practice is unclear. Our goal with this review is to highlight some of the novel PSG metrics/analyses that are becoming available. We suggest that stronger academic-industry relationships would facilitate the development of state-of-the-art clinical research to establish the value of novel PSG metrics/analyses in clinical sleep medicine. Collectively, as a sleep community, it is time to reinvent how we utilize the polysomnography to move us towards Precision Sleep Medicine.

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.

Evaluation of the changes in the hearing system over the years among patients with OSAS using a CPAP device

OBJECTIVE

To evaluate whether patients using a continuous positive airway pressure (CPAP) device for obstructive sleep apnea syndrome (OSAS) have improvement or deterioration in their auditory systems.

METHODS

Charts of OSAS patients who were followed up at the ENT clinic were retrospectively reviewed starting from 2018. The hearing tests performed at least 2 years before and after CPAP use in patients were compared with themselves and with the test results of patients with no CPAP use.

RESULTS

No improvement in the hearing system on the patients using a CPAP device was detected. Deterioration in hearing was detected in 13.63% and 9.09% of the patients with and without CPAP use, respectively. No statistically significant difference was found between the two groups.

CONCLUSION

The use of a CPAP device does not affect hearing positively or negatively.

Cardiovascular morbidities of obstructive sleep apnea and the role of circulating extracellular vesicles

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway collapse during sleep resulting in impaired blood gas exchange, namely intermittent hypoxia (IH) and hypercapnia, fragmented sleep (SF), increased oxidative stress and systemic inflammation. Among a myriad of potential associated morbidities, OSA has been particularly implicated as mechanistically contributing to the prevalence and severity of cardiovascular diseases (CVD). However, the benefits of continuous positive airway pressure (CPAP), which is generally employed in OSA treatment, to either prevent or improve CVD outcomes remain unconvincing, suggesting that the pathophysiological mechanisms underlying the incremental CVD risk associated with OSA are not clearly understood. One of the challenges in development of non-invasive diagnostic assays is the ability to identify clinically and mechanistically relevant biomarkers. Circulating extracellular vesicles (EVs) and their cargos reflect underlying changes in cellular homeostasis and can provide insights into how cells and systems cope with physiological perturbations by virtue of the identity and abundance of miRNAs, mRNAs, proteins, and lipids that are packaged in the EVs under normal as well as diseased states, such as OSA. EVs can not only provide unique insights into coordinated cellular responses at the organ or systemic level, but can also serve as reporters of the effects of OSA in CVD, either by their properties enabling regeneration and repair of injured vascular cells or by damaging them. Here, we highlight recent progress in the pathological CVD consequences of OSA, and explore the putative roles of EVs in OSA-associated CVD, along with emerging diagnostic and therapeutic opportunities.

The reviews of this paper are available via the supplemental material section.

Protective Effects of Obstructive Sleep Apnea on Outcomes After Subarachnoid Hemorrhage: A Nationwide Analysis

BACKGROUND

Obstructive sleep apnea (OSA) is typically associated with an increased risk of cardiovascular and cerebrovascular disease. Recent studies, however, have suggested that hypercapnia and chronic intermittent hypoxia may potentially provide protection against ischemic events like stroke.

OBJECTIVE

To evaluate the impact of OSA with presentation, hospital course, and treatment outcomes of patients with subarachnoid hemorrhage (SAH).

METHODS

Data for patients with SAH between the years 2011 and 2015 were extracted from the Nationwide Inpatient Sample (NIS) and stratified based on diagnosis codes for OSA. Univariate analysis was used to assess the prevalence of comorbidities in OSA patients diagnosed with SAH and several covariates, including patient demographics, aneurysmal treatment, in-hospital morality rate, length of stay, and costs. Multivariate logistic regression models analyzed the relationship between several comorbidities, including OSA, tobacco use, and hypertension, and poor outcomes after SAH.

RESULTS

Data from 49 265 SAH patients were used in this study, of which 2408 (4.9%) also had a concomitant OSA diagnosis. Patients with OSA compared to all other SAH patients had a significantly lower in-hospital mortality rate, as well as statistically significant lower odds of vasospasm, stroke, and poor outcomes. Additionally, hypercholesterolemia, obesity, and tobacco use disorder were also associated with more favorable outcomes.

CONCLUSION

SAH patients with OSA are significantly less likely to have a poor outcome when compared to non-OSA patients, despite having an increased risk of several comorbidities.

Impact of Sleep-Disordered Breathing on Functional Outcomes in Ischemic Stroke: A Cardiopulmonary Coupling Analysis

BACKGROUND AND PURPOSE

Cardiopulmonary coupling (CPC) analysis is an easily assessable method to evaluate sleep-disordered breathing (SDB); however, its prognostic impact in patients with acute ischemic stroke needs to be investigated. We performed a CPC analysis using Holter monitoring at the early stage of noncardioembolic ischemic stroke to investigate the prognostic effect of SDB on functional impairment at the 3-month follow-up.

METHODS

A total 615 patients with acute noncardioembolic ischemic stroke who underwent Holter monitoring within 30 days of stroke onset were enrolled from a multicenter, prospective, all-comer cohort. CPC analysis was conducted, and SDB was defined by the presence of narrow-band coupling during sleep time. We investigated the association between SDB and functional impairment at 3 months as measured by the modified Rankin Scale.

RESULT

Narrow-band coupling was present in 191 (31.1%) of 615 patients (mean age 64.5±12.6 years). The narrow-band group showed a significantly higher rate of severe functional impairment (modified Rankin Scale score >2; 45.5% versus 12.9%, P<0.001) and persistent disability (Δmodified Rankin Scale score ≤0; 53.9% versus 39.8%, P<0.001) at the 3-month follow-up. In multivariate analysis, narrow-band coupling was an independent predictor of higher risk of severe and persistent functional impairment at 3 months (odds ratio, 3.98 [95% CI, 2.34-6.78]; P<0.001; and odds ratio, 1.81 [95% CI, 1.23-2.66]; P<0.001, respectively). The results remained consistent after propensity-score matched analysis with 157 patient pairs (C-statistic=0.770).

CONCLUSIONS

SDB assessed by CPC analysis at the early stage of ischemic stroke could predict severe and prolonged functional impairment at 3 months. CPC analysis using Holter monitoring can help predicting functional impairment in acute ischemic stroke.

Obstructive sleep apnea and Parkinson's disease: characteristics and associated factors

ABSTRACT Obstructive sleep apnea (OSA) occurs in up to 66% of Parkinson's disease (PD) patients, higher than in the general population. Although it is more prevalent, the relationship between OSA and PD remains controversial, with some studies confirming and others denying the relationship of OSA with some risk factors and symptoms in patients with PD. Objective: To determine the factors associated with OSA in PD patients com DP. Methods: A cross-sectional study was performed with 88 consecutive patients with PD from the outpatient clinic. Participants underwent clinical interviews with neurologists and a psychiatrist, assessment using standardized scales (Epworth Sleepiness Scale, Parkinson's Disease Questionnaire, Pittsburgh Sleep Quality Index and, for individuals with a diagnosis of restless legs syndrome/Willis-Ekbom disease, the International Restless Legs Syndrome Rating Scale), and video-polysomnography. Results: Individuals with PD and OSA were older and had less insomnia than those with PD without OSA. Regarding the polysomnographic variables, we observed a lower percentage of stage N3 sleep, a higher arousal index, and a higher oxygen desaturation index in those individuals with OSA, relative to those without OSA. In the multivariate analysis, only the percentage of stage N3 sleep and the oxygen desaturation index were significantly different. Besides this, most of the PD patients with OSA had a correlation with sleeping in the supine position (58% of OSA individuals). Conclusion: The PD patients showed a high prevalence of OSA, with the supine position exerting a significant influence on the OSA in these patients, and some factors that are associated with OSA in the general population did not seem to have a greater impact on PD patients.