Effect of Continuous Positive Airway Pressure on Cardiovascular Biomarkers: The Sleep Apnea Stress Randomized Controlled Trial

Role of Oxidative Stress in the Occurrence and Development of Cognitive Dysfunction in Patients with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) causes recurrent apnea and intermittent hypoxia at night, leading to several complications such as cognitive dysfunction. However, the molecular mechanisms underlying cognitive dysfunction in OSAS are unclear, and oxidative stress mediated by intermittent hypoxia is an important mechanism. In addition, the improvement of cognitive dysfunction in patients with OSAS varies by different treatment regimens; among them, continuous positive airway pressure therapy (CPAP) is mostly recognized for improving cognitive dysfunction. In this review, we discuss the potential mechanisms of oxidative stress in OSAS, the common factors of affecting oxidative stress and the Links between oxidative stress and inflammation in OSAS, focusing on the potential links between oxidative stress and cognitive dysfunction in OSAS and the potential therapies for neurocognitive dysfunction in patients with OSAS mediated by oxidative stress. Therefore, further analysis on the relationship between oxidative stress and cognitive dysfunction in patients with OSAS will help to clarify the etiology and discover new treatment options, which will be of great significance for early clinical intervention.

Causal relationship between levels of myeloperoxidase and obstructive sleep apnea: a bidirectional two-sample Mendelian randomization study

Background

Several observational studies have investigated the association between myeloperoxidase (MPO) and obstructive sleep apnea (OSA). However, the nature of this relationship remains uncertain due to potential selection and confounding biases. To resolve this, we conducted a bidirectional two-sample Mendelian randomization (MR) study to scrutinize the causal relationship between MPO and OSA.

Methods

Instrumental variables (IVs) for OSA were sourced from the publicly available FinnGen dataset, encompassing 38,998 OSA cases and 336,659 controls. Data on MPO were sourced from a study of 21,758 individuals conducted by the European Bioinformatics Institute (EBI). The primary MR analysis utilized the inverse-variance weighted (IVW) method, with MR-Egger intercept and leave-one-out methods assessing pleiotropy and Cochran's Q test determining heterogeneity.

Results

The IVW analysis indicated a causal relationship between heightened MPO levels and an increased incidence of OSA. Individuals with elevated MPO levels manifested a higher propensity to develop OSA, exhibiting an odds ratio (OR) of 1.075 and a 95% confidence interval (CI) of 1.011-1.143 (p = 0.021). Conversely, the reciprocal analysis unveiled no significant association between OSA and heightened MPO levels (p = 0.643). No directional pleiotropy was identified through the MR-Egger intercept test (p > 0.05).

Conclusion

Our study provides evidence of an association between elevated MPO levels and an increased incidence of OSA. However, OSA does not necessarily lead to elevated MPO levels. When patients present with high MPO levels, screening for OSA may be advisable, considering their clinical characteristics.

Investigating the Relationship between Obstructive Sleep Apnoea, Inflammation and Cardio-Metabolic Diseases

Obstructive sleep apnoea (OSA) is a prevalent underdiagnosed disorder whose incidence increases with age and weight. Uniquely characterised by frequent breathing interruptions during sleep-known as intermittent hypoxia (IH)-OSA disrupts the circadian rhythm. Patients with OSA have repeated episodes of hypoxia and reoxygenation, leading to systemic consequences. OSA consequences range from apparent symptoms like excessive daytime sleepiness, neurocognitive deterioration and decreased quality of life to pathological complications characterised by elevated biomarkers linked to endocrine-metabolic and cardiovascular changes. OSA is a well-recognized risk factor for cardiovascular and cerebrovascular diseases. Furthermore, OSA is linked to other conditions that worsen cardiovascular outcomes, such as obesity. The relationship between OSA and obesity is complex and reciprocal, involving interaction between biological and lifestyle factors. The pathogenesis of both OSA and obesity involve oxidative stress, inflammation and metabolic dysregulation. The current medical practice uses continuous positive airway pressure (CPAP) as the gold standard tool to manage OSA. It has been shown to improve symptoms and cardiac function, reduce cardiovascular risk and normalise biomarkers. Nonetheless, a full understanding of the factors involved in the deleterious effects of OSA and the best methods to eliminate their occurrence are still poorly understood. In this review, we present the factors and evidence linking OSA to increased risk of cardiovascular conditions.

Effect of different treatments for obstructive sleep apnoea on blood pressure

OBJECTIVE

Obstructive sleep apnoea (OSA) is a common cause of secondary hypertension. This network meta-analysis (NMA) assessed the effect of different OSA treatments on lowering blood pressure.

METHODS

PubMed, EMBASE, Web of Science, and Cochrane Library databases were searched for relevant randomized controlled trials. The search strategies included the concepts of OSA, blood pressure, hypertension, and blood pressure-reducing treatments without language or data restriction (from inception to 1 June 2021). The outcomes included office SBP, office DBP, daytime SBP (dSBP) and DBP (dDBP), and night-time SBP (nSBP) and DBP (nDBP). A Bayesian network meta-analysis was performed, and mean differences with 95% credibility intervals were calculated.

RESULTS

We reviewed 49 randomized controlled trials involving 4893 patients and the following interventions: continuous positive-airway pressure (CPAP), mandibular advancement devices, nocturnal supplemental oxygen, surgery, β-blocker, angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs), renal sympathetic denervation (RDN), mineralocorticoid receptor antagonists (MRAs), calcium channel blockers. MRAs were significantly associated with blood pressure reduction followed by ACEI/ARB. RDN could reduce office SBP, office DBP, 24-h SBP, 24-h DBP, dSBP, and dDBP. CPAP also demonstrated modest blood pressure lowering.

CONCLUSION

MRAs and ACEIs/ARBs can reduce blood pressure effectively in patients with OSA. RDN is a novel hypertension treatment that lowered blood pressure in such patients. CPAP was associated with mild but stable blood pressure reduction, and it might be helpful as an adjunctive therapy in OSA patients with hypertension.

REVIEW REGISTRATION

This systematic review and meta-analysis was registered in PROSPERO: CRD42021240891.

Arterial Stiffness Assessment Using the Arteriograph in Patients with Moderate-Severe OSA and Metabolic Syndrome-A Pilot Study

BACKGROUND

Both obstructive sleep apnea (OSA) and metabolic syndrome (MS) promote arterial stiffening. As a basis for this study, we presumed that arterial stiffness could be assessed using the Arteriograph (TensioMed, Budapest, Hungary) to detect early modifications induced by continuous positive airway therapy (CPAP) in reversing this detrimental vascular remodeling. Arterial stiffness is increasingly acknowledged as a major cardiovascular risk factor and a marker of subclinical hypertension-mediated organ damage. The aim of this pilot study was to evaluate the arterial stiffness changes in patients with moderate-severe OSA and MS after short-term CPAP use.

METHODS

We performed a prospective study that included patients with moderate-severe OSA and MS who had not undergone previous CPAP therapy. All subjects underwent clinical examination and arterial stiffness assessment using the oscillometric technique with Arteriograph (TensioMed, Budapest, Hungary) detection before and after 8-week CPAP therapy.

RESULTS

39 patients with moderate-severe OSA were included. Eight weeks of CPAP therapy significantly improved central systolic blood pressure (Δ = -11.4 mmHg, p = 0.009), aortic pulse wave velocity (aoPWV: Δ = -0.66 m/s, p = 0.03), and aortic augmentation index (aoAix: Δ = -8.25%, p = 0.01) only in patients who used the device for a minimum of 4 h/night (n = 20).

CONCLUSIONS

Arterial stiffness was improved only among CPAP adherent patients and could be detected using the Arteriograph (TensioMed, Budapest, Hungary), which involves a noninvasive procedure that is easy to implement for the clinical evaluation of arterial stiffness.

Association between obstructive sleep apnea and lipid metabolism during REM and NREM sleep

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is thought to be associated with dyslipidemia. However, differences concerning dyslipidemia during rapid eye movement (REM) and non-REM (NREM) sleep have yet to be determined. This study was designed to explore the association between lipid profiles and OSA during REM or NREM sleep.

METHODS

This is a clinical cohort. A total of 2,619 participants with at least 30 minutes of REM sleep were included. Sleep variables and fasting lipid profiles [total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), apolipoprotein (apo)A-I, apoB, apoE, and lipoprotein(a) (Lp(a))] were obtained from each participant. Apnea-hypopnea indices in REM and NREM sleep (AHI_REM and AHI_NREM, respectively) were recorded. Linear regression analysis was used to assess the associations of AHI_REM and AHI_NREM with lipid profiles.

RESULTS

When stratified by the AHI_REM severity of OSA, all demographics, clinical variables, and sleep parameters differed between the groups except for apoA-I. In fully-adjusted multivariate linear regression models, AHI_REM was independently associated with increasing levels of TG, HDL-C, and apoE (P = .04, P = .01 and P = .01, respectively). AHI_NREM was independently associated with increasing levels of TC, TG, LDL, and apoB, and lower level of HDL-C (all P < .05). In sensitivity analyses by only exploring associations in patients who had an AHI_NREM or AHI_REM < 5 events/h in separate regression models, AHI_REM was not associated with all-lipid profile in almost all adjusted models (all P > .05), whereas AHI_NREM was associated with elevated TC, LDL-C, and apoB (P = .03, P = .01 and P = .01, respectively).

CONCLUSIONS

AHI_NREM was independently associated with the greatest alterations in serum lipids, including TC, LDL-C, and apoB.

Cardiovascular Disorders Triggered by Obstructive Sleep Apnea-A Focus on Endothelium and Blood Components

Obstructive sleep apnea (OSA) is known to be an independent cardiovascular risk factor. Among arousal from sleep, increased thoracic pressure and enhanced sympathetic activation, intermittent hypoxia is now considered as one of the most important pathophysiological mechanisms contributing to the development of endothelial dysfunction. Nevertheless, not much is known about blood components, which justifies the current review. This review focuses on molecular mechanisms triggered by sleep apnea. The recurrent periods of hypoxemia followed by reoxygenation promote reactive oxygen species (ROS) overproduction and increase inflammatory response. In this review paper we also intend to summarize the effect of treatment with continuous positive airway pressure (CPAP) on changes in the profile of the endothelial function and its subsequent potential clinical advantage in lowering cardiovascular risk in other comorbidities such as diabetes, atherosclerosis, hypertension, atrial fibrillation. Moreover, this paper is aimed at explaining how the presence of OSA may affect platelet function and exert effects on rheological activity of erythrocytes, which could also be the key to explaining an increased risk of stroke.

High Plasma Cystine Levels Are Associated with Blood Pressure and Reversed by CPAP in Patients with Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) independent of obesity (OBS) imposes severe cardiovascular risk. To what extent plasma cystine concentration (CySS), a novel pro-oxidative vascular risk factor, is increased in OSA with or without OBS is presently unknown. We therefore studied CySS together with the redox state and precursor amino acids of glutathione (GSH) in peripheral blood mononuclear cells (PBMC) in untreated male patients with OSA (apnea-hypopnea-index (AHI) > 15 h^-1, n = 28) compared to healthy male controls (n = 25) stratifying for BMI ≥ or < 30 kg m^-2. Fifteen OSA patients were reassessed after 3-5-months CPAP. CySS correlated with cumulative time at an O₂-saturation <90% (Tu90%) (r = 0.34, p < 0.05) beside BMI (r = 0.58, p < 0.001) and was higher in subjects with "hypoxic stress" (59.4 ± 2.0 vs. 50.1 ± 2.7 µM, p < 0.01) defined as Tu90% ≥ 15.2 min (corresponding to AHI ≥ 15 h^-1). Moreover, CySS significantly correlated with systolic (r = 0.32, p < 0.05) and diastolic (r = 0.31, p < 0.05) blood pressure. CPAP significantly lowered CySS along with blood pressure at unchanged BMI. Unexpectedly, GSH antioxidant capacity in PBMC was increased with OSA and reversed with CPAP. Plasma CySS levels are increased with OSA-related hypoxic stress and associated with higher blood pressure. CPAP decreases both CySS and blood pressure. The role of CySS in OSA-related vascular endpoints and their prevention by CPAP warrants further studies.

Sex-Specific Differential Responses of Circulating Biomarkers in Obstructive Sleep Apnea Treatment. A Post Hoc Analysis of a Randomized Controlled Trial

Rationale: Knowledge of sex-specific changes of cardiovascular biomarkers in response to continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea (OSA) is limited.Objectives: We hypothesized a differential sex-specific cardiovascular biomarker response with CPAP therapy for OSA.Methods: Participants with moderate-severe OSA (apnea-hypopnea index, 15 events/h) were randomized to CPAP versus sham and completed polysomnography and collection of biomarkers of inflammation (myeloperoxidase, fibrinogen, paraoxonase, interleukin [IL]-6, IL-6 soluble receptor, aryl esterase, oxidized low-density lipoprotein, lipoprotein A, plasminogen activator inhibitor 1, and F₂-isoprostane urine/creatinine ratio) and vascular measures at baseline and 8 weeks of therapy with either CPAP (n = 72) or sham treatment (n = 70). Post hoc secondary analyses of sex-study arm interaction relative to change in inflammatory biomarkers were evaluated via linear regression with adjustment for baseline biomarker value, age, race, body mass, index, waist circumference, and CPAP adherence. Interactions were further evaluated via sex-stratified analyses.Results: The study sample comprised a total of 149 participants aged 50.8 ± 11.7 years; 55% were male, and 55% were white. Participants had a median apnea-hypopnea index of 26.3 events per hour (interquartile range, 13-37). There were substantial interactions between study arm and sex for myeloperoxidase, paraoxonase, and fibrinogen (P = 0.03, P = 0.03, and P = 0.08, respectively). No significant interactions were found for the vascular measures. Estimates were similar but with decreased power in sex-stratified analyses, with decreased biomarkers in women and increased biomarkers in men.Conclusions: Differential sex-specific responses to CPAP therapy for OSA were observed for circulating inflammatory biomarkers, which persisted after adjustment for confounders. These findings set the stage for validation studies and, if confirmed, biochemical pathway elucidation to inform sex-specific personalized treatment approaches.Clinical trial registered with www.clinicaltrials.gov (NCT00607893).

Oxidative Stress and Inflammation Biomarker Expression in Obstructive Sleep Apnea Patients

Obstructive Sleep Apnea Syndrome (OSAS) is a respiratory sleep disorder characterised by repeated episodes of partial or complete obstruction of the upper airway during the night. This obstruction usually occurs with a reduction (hypopnea) or complete cessation (apnea) of the airflow in the upper airways with the persistence of thoracic-diaphragmatic respiratory movements. During the hypopnea/apnea events, poor alveolar ventilation reduces the oxygen saturation in the arterial blood (SaO₂) and a gradual increase in the partial arterial pressure of carbon dioxide (PaCO₂). The direct consequence of the intermittent hypoxia is an oxidative imbalance, with reactive oxygen species production and the inflammatory cascade’s activation with pro and anti-inflammatory cytokines growth. Tumour necrosis factors, inflammatory cytokines (IL2, IL4, IL6), lipid peroxidation, and cell-free DNA have been found to increase in OSAS patients. However, even though different risk-related markers have been described and analysed in the literature, it has not yet been clarified whether specified inflammatory bio-markers better correlates with OSAS diagnosis and its clinical evolution/comorbidities. We perform a scientific literature review to discuss inflammatory and oxidative stress biomarkers currently tested in OSAS patients and their correlation with the disease’s severity and treatment.

Obstructive sleep apnoea treatment and blood pressure: which phenotypes predict a response? A systematic review and meta-analysis

The treatment for obstructive sleep apnoea (OSA) with continuous positive airway pressure (CPAP) or mandibular advancement devices (MADs) is associated with blood pressure (BP) reduction; however, the overall effect is modest. The aim of this systematic review and meta-analysis of randomised controlled trials (RCTs) comparing the effect of such treatments on BP was to identify subgroups of patients who respond best to treatment.The article search was performed in three different databases with specific search terms and selection criteria. From 2289 articles, we included 68 RCTs that compared CPAP or MADs with either passive or active treatment. When all the studies were pooled together, CPAP and MADs were associated with a mean BP reduction of -2.09 (95% CI -2.78- -1.40) mmHg for systolic BP and -1.92 (95% CI -2.40- -1.43) mmHg for diastolic BP and -1.27 (95% CI -2.34- -0.20) mmHg for systolic BP and -1.11 (95% CI -1.82- -0.41) mmHg for diastolic BP, respectively. The subgroups of patients who showed a greater response were those aged <60 years (systolic BP -2.93 mmHg), with uncontrolled BP at baseline (systolic BP -4.14 mmHg) and with severe oxygen desaturations (minimum arterial oxygen saturation measured by pulse oximetry <77%) at baseline (24-h systolic BP -7.57 mmHg).Although this meta-analysis shows that the expected reduction of BP by CPAP/MADs is modest, it identifies specific characteristics that may predict a pronounced benefit from CPAP in terms of BP control. These findings should be interpreted with caution; however, they are particularly important in identifying potential phenotypes associated with BP reduction in patients treated for OSA.

Effect of continuous positive airway pressure on inflammatory, antioxidant, and depression biomarkers in women with obstructive sleep apnea: a randomized controlled trial

STUDY OBJECTIVES

The effect of continuous positive airway pressure (CPAP) on mediators of cardiovascular disease and depression in women with obstructive sleep apnea (OSA) is unknown. We aimed to assess the effect of CPAP therapy on a variety of biomarkers of inflammation, antioxidant activity, and depression in women with OSA.

METHODS

We conducted a multicenter, randomized controlled trial in 247 women diagnosed with moderate-to-severe OSA (apnea-hypopnea index [AHI] ≥ 15). Women were randomized to CPAP (n = 120) or conservative treatment (n = 127) for 12 weeks. Changes in tumor necrosis factor α (TNFα), interleukin 6 (IL-6), C-reactive protein (CRP), intercellular adhesion molecule 1 (ICAM-1), catalase (CAT), superoxide dismutase (SOD), and brain-derived neurotrophic factor (BDNF) were assessed. Additional analyses were conducted in subgroups of clinical interest.

RESULTS

Women had a median (25th-75th percentiles) age of 58 (51-65) years, body mass index 33.5 (29.0-38.3) kg/m2, and AHI 33.3 (22.8-49.3). No differences were found between groups in the baseline levels of the biomarkers. After 12 weeks of follow-up, there were no changes between groups in any of the biomarkers assessed. These results did not change when the analyses were restricted to sleepy women or to those with severe OSA. In women with CPAP use at least 5 hours per night, only TNFα levels decreased compared to the control group (-0.29 ± 1.1 vs -0.06 ± 0.53, intergroup difference -0.23 [95% CI = -0.03 to -0.50]; p = 0.043).

CONCLUSIONS

Twelve weeks of CPAP therapy does not improve biomarkers of inflammation, antioxidant activity, or depression compared to conservative treatment in women with moderate-to-severe OSA.

TRIAL REGISTRATION

NCT02047071.

The role of sham continuous positive airway pressure as a placebo in controlled trials: Best Apnea Interventions for Research Trial

STUDY OBJECTIVES

The main objective of this study was to evaluate the role of sham continuous positive airway pressure (CPAP) compared to conservative medical therapy (CMT) as a control arm in the Best Apnea Interventions for Research (BestAIR) study by assessing differences in subjectively and objectively measured outcomes, adverse events, adherence, and retention rates.

METHODS

BestAIR is a clinical trial aimed to identify important design features for future randomized controlled trials of CPAP. Participants with obstructive sleep apnea were randomized to one of four groups; two control arms (CMT, sham-CPAP) and two active CPAP arms (with and without behavioral interventions). Blood pressure and health-related quality of life outcomes were assessed at baseline, 6 and 12 months. Study outcomes, retention, and adverse event rates were compared between the two control arms. Sham-CPAP adherence and self-efficacy were also compared to active-CPAP adherence (without behavioral intervention).

RESULTS

Our sample included 86 individuals in the control arms and 42 participants in the active-CPAP arm. There were no differences in longitudinal profiles in blood pressure, health-related quality of life outcomes, dropout rates, or adverse events in sham-CPAP group compared to CMT-only group (all ps > 0.05); standardized differences were generally small and with inconsistent directionality across measurements. When compared to active-CPAP, sham-CPAP was associated with 93 fewer minutes/night of usage over 12 months (p = 0.007) and lower outcome expectations (p < 0.05).

CONCLUSION

We observed no evidence of differences in objectively or subjectively measured outcomes with the use of sham-CPAP compared to CMT group. The lower adherence on sham-CPAP and poorer self-efficacy compared to active-CPAP may suggest differences in perceived benefit.

REGISTRATION

NCT01261390 Best Apnea Interventions for Research (BestAIR) www.clinicaltrials.gov.

The impact of continuous positive airway pressure therapy on circulating levels of malondialdehyde: a systematic review and meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder which associated with increased oxidative stress and cardiovascular diseases. Malondialdehyde (MDA) is a reliable marker of lipid peroxidation and is elevated in patients with OSA. Studies reported inconsistent findings on the effect of continuous positive airway pressure (CPAP) therapy on MDA levels. As the study power maybe a reason for the inconsistent findings, we aimed to use meta-analysis to assess effect of CPAP therapy on MDA in patients with OSA.

METHOD

Electronic search was performed to find out studies on the effect of CAPA on MDA levels in OSA patients. Search carried out in databases of PubMed, EMBASE, Scopus, Cochrane library and web of science.

RESULTS

Search resulted in 161 records of which 83 remained after removing duplicated records. Further, 51 articles were removed by title and abstract and 22 records evaluated by full text. Finally 13 articles were included in the intended meta-analysis. Pooled analysis demonstrated that CPAP therapy reduced MDA levels significantly [SMD (-1.51) (95% CI, -2.06 to -0.97) p < 0.05]. Subgroup analyses showed that CPAP therapy was effective in categories of age (≤50 and > 50 years), BMI (≤30 and > 30 kg/m²) and therapy duration (≤12 week and >12 week).

CONCLUSION

the results of the present study demonstrated considerable effect of CPAP therapy on MDA as independent risk factor for cardiovascular diseases and robust marker of lipid peroxidation.

Obstructive sleep apnea and dyslipidemia: from animal models to clinical evidence

Lipid metabolism deregulation constitutes the pathogenic basis for the development of atherosclerosis and justifies a high incidence of cardiovascular-related morbidity and mortality. Some data suggest that dyslipidemia may be associated with sleep-disordered breathing, mainly obstructive sleep apnea (OSA), due to alterations in fundamental biochemical processes, such as intermittent hypoxia (IH). The aim of this systematic review was to identify and critically evaluate the current evidence supporting the existence of a possible relationship between OSA and alterations in lipid metabolism. Much evidence shows that, during the fasting state, OSA and IH increase lipid delivery from the adipose tissue to the liver through an up-regulation of the sterol regulatory element-binding protein-1 and stearoyl-CoA desaturase-1, increasing the synthesis of cholesterol esters and triglycerides. In the postprandial state, lipoprotein clearance is delayed due to lower lipoprotein lipase activity, probably secondary to IH-up-regulation of angiopoietin-like protein 4 and decreased activity of the peroxisome proliferator-activated receptor alpha. Moreover, oxidative stress can generate dysfunctional oxidized lipids and reduce the capacity of high-density lipoproteins (HDL) to prevent low-density lipoprotein (LDL) oxidation. In the clinical field, several observational studies and a meta-regression analysis support the existence of a link between OSA and dyslipidemia. Although there is evidence of improved lipid profile after apnea-hypopnea suppression with continuous positive airway pressure (CPAP), the majority of the data come from observational studies. In contrast, randomized controlled trials evaluating the effects of CPAP on lipid metabolism present inconclusive results and two meta-analyses provide contradictory evidence.

Effects of suboptimal adherence of CPAP therapy on symptoms of obstructive sleep apnoea: a randomised, double-blind, controlled trial

Introduction

Continuous positive airway pressure (CPAP) is currently the treatment of choice for sleepiness in patients with obstructive sleep apnoea (OSA); however, adherence is often thought to be suboptimal. We investigated the effects of suboptimal CPAP usage on objective and subjective sleepiness parameters in patients with OSA.

Material and methods

In this 2-week, parallel, double-blind, randomised controlled trial we enrolled moderate-to-severe OSA patients with excessive pre-treatment daytime sleepiness (Epworth sleepiness scale (ESS) score >10 points) who had suboptimal CPAP adherence over ≥12 months (mean nightly usage time 3–4 h). Patients were allocated through minimisation to either subtherapeutic CPAP (“sham CPAP”) or continuation of CPAP (“therapeutic CPAP”). A Bayesian analysis with historical priors calculated the posterior probability of superiority.

Results

Between May, 2016 and November, 2018, 57 patients (aged 60±8 years, 79% male, 93% Caucasian) were allocated in total, and 52 who completed the study (50% in each arm) were included in the final analysis. The unadjusted ESS score increase was 2.4 points (95% CI 0.6–4.2, p=0.01) in the sham-CPAP group when compared to continuing therapeutic CPAP. The probability of superiority of therapeutic CPAP over sham CPAP was 90.4% for ESS, 90.1% for systolic blood pressure and 80.3% for diastolic blood pressure.

Conclusions

Patients with moderate-to-severe OSA and daytime sleepiness are still getting a substantial benefit from suboptimal CPAP adherence, albeit not as much as they might get if they adhered more. Whether a similar statement can be made for even lower adherence levels remains to be established in future trials.

Alpha Lipoic Acid Improves Endothelial Function and Oxidative Stress in Mice Exposed to Chronic Intermittent Hypoxia

Objective

Obstructive sleep apnea (OSA) is characterized by recurrent airway collapse that causes chronic intermittent hypoxia (CIH). OSA is associated with systemic inflammation and oxidative stress resulting in endothelial dysfunction and cardiovascular disease (CVD). Alpha lipoic acid (ALA) is a potent antioxidant with anti-inflammatory properties. We hypothesized that dietary ALA can improve endothelial function of mice exposed to CIH.

Methods

Mice were exposed to either CIH or intermittent air (IA) and treated with dietary ALA (0.2% w/w) or a regular chow diet for 8 weeks. Endothelial function, endothelial nitric oxide (eNOS) uncoupling, systemic oxidative stress, systemic inflammation, aortic expression of inflammatory cytokines, and antioxidant enzymes were measured after 8 weeks.

Results

Mice exposed to CIH exhibited endothelial dysfunction accompanied by systemic oxidative stress and inflammation as well as increased aortic expression of inflammatory cytokines. Furthermore, CIH led to eNOS uncoupling. Treatment with dietary ALA reversed endothelial dysfunction in mice exposed to CIH, lowered systemic oxidative stress and inflammation, prevented the increases of inflammatory cytokine gene expression, increased the expression of antioxidant enzymes, and preserved eNOS in a coupled state.

Conclusion

ALA attenuates endothelial dysfunction by preventing oxidative stress and inflammation and restoring nitric oxide bioavailability in mice exposed to CIH. Our data suggests the potential beneficial use of ALA as adjunctive therapy in OSA.

Severe Obstructive Sleep Apnea With Imaged Carotid Plaque Is Significantly Associated With Systemic Inflammation

PURPOSE

Persons with obstructive sleep apnea (OSA) are at heightened risk of myocardial infarction (MI) and stroke caused by adiposity and intermittent hypoxia, which provoke proinflammatory cytokines to induce systemic and vascular inflammation, resulting in endothelial dysfunction and development of atherosclerotic plaque. This study compared levels of systemic inflammation, as indexed by the neutrophil-to-lymphocyte ratio (NLR), between groups of patients with severe OSA with and without carotid artery calcified plaque (CACP⁺ and CACP^-, respectively) on their panoramic image (PI).

MATERIALS AND METHODS

This study had a retrospective cross-sectional study design. Medical records and PIs of men with severe OSA treated by the dental service (January 1, 2017 to December 31, 2017) were reviewed. The predictor variable was the presence or absence of CACP on PIs and the outcome variable was NLR. The t test was used to analyze differences in mean NLRs between groups. Atherogenic risk factors (age, body mass index, hypertension, and diabetes) were assessed for independence by descriptive and logistic regression analyses. Significance set at .05 for all tests.

RESULTS

The study group (n = 39) of patients with CACP⁺ (mean age, 63 ± 7.4 yr) showed a mean NLR of 3.09 ± 1.42. The control group (n = 46) of patients with CACP^- (mean age, 62 ± 6.8 yr) showed a mean NLR of 2.10 ± 0.58. The difference between groups was significant (P < .001). Logistic regression for NLR and CACP failed to show meaningful correlations with covariates.

CONCLUSION

Older men with severe OSA and carotid atheromas on PIs show substantially greater systemic inflammation measured by NLRs. The combination of severe OSA, atheroma formation, and markedly increased NLR suggests a higher risk of MI and stroke and greater need for cardiovascular and cerebrovascular evaluation.

Association of continuous positive airway pressure with F2-isoprostanes in adults with obstructive sleep apnea: a meta-analysis

PURPOSE

Obstructive sleep apnea (OSA) is associated with increased F2-isoprostanes, a reliable standard biomarker of oxidative stress. Treatment with continuous positive airway pressure (CPAP) is effective for all degrees of OSA. However, it remains unknown whether treatment with CPAP will decrease F2-isoprostanes. A meta-analysis was conducted to determine the effect of CPAP treatment on F2-isoprostanes among patients with OSA.

METHODS

The PubMed, Embase, Web of Science, and Cochrane library were searched before September, 2018. Eight articles assessing indices of F2-isoprostanes from various body fluids were identified. Pooled standardized mean difference (SMD) and weighted mean difference (WMD) were appropriately calculated through fixed or random effects models after assessing between-study heterogeneity.

RESULTS

A total of 4 studies with 108 patients were pooled for exhaled breath condensate (EBC) F2-isoprostanes; 3 studies with 93 patients were pooled for serum or plasma F2-isoprostanes; and 3 studies with 102 patients were pooled for urinary F2-isoprostanes. A significant decrease of EBC F2-isoprostanes was observed after CPAP treatment (WMD = 2.652, 95% CI = 0.168 to 5.136, z = 2.09, p = 0.036), as well as serum or plasma F2-isoprostanes and urinary F2-isoprostanes (SMD = 1.072, 95% CI = 0.276 to 1.868, z = 2.64, p = 0.008 and WMD = 85.907, 95% CI = 50.443 to 121.372, z = 4.75, p = 0.000, respectively).

CONCLUSIONS

This meta-analysis suggested that CPAP therapy was associated with a significant decrease in F2-isoprostanes in patients with OSA.

Mechanisms of cardiovascular disease in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is recognized as a major public health burden conveying a significant risk of cardiovascular diseases (CVD) and mortality. Continuous positive airway pressure (CPAP) is the treatment of choice for the majority of patients with OSA but the benefit of CPAP on CVD is uncertain. Thus, a greater understanding of the mechanisms by which OSA leads to CVD might identify novel therapeutic approaches. Intermittent hypoxia (IH), a hallmark feature of OSA, plays a key role in the pathogenesis and experimental studies using animal and cell culture studies suggest that IH mediates CVD through activation of multiple mechanistic pathways such as sympathetic excitation, inflammation, oxidative stress or metabolic dysregulation. Recurrent arousals, intrathoracic pressure swings and concomitant obesity likely play important additive roles in this process. In this review, the available evidence of the pathophysiological mechanisms of CVD in OSA is explored with a specific emphasis on IH, recurrent arousals and intrathoracic pressure swings as the main pathophysiological triggers.

Management of Obstructive Sleep Apnea in Pregnancy

The spectrum of sleep-disordered breathing (SDB) ranges from mild snoring to obstructive sleep apnea, the most severe form of SDB. Current recommendations are to treat these women with continuous positive airway pressure despite limited data. SDB in early and mid-pregnancy is associated with preeclampsia and gestational diabetes. Pregnant women with a diagnosis of obstructive sleep apnea at delivery were at significantly increased risk of having cardiomyopathy, congestive heart failure, pulmonary embolism, and in-hospital death. These effects were exacerbated in the presence of obesity. Postpartum, these women are at risk for respiratory suppression and should be monitored.

A review of the associations between obstructive sleep apnea and hypertensive disorders of pregnancy and possible mechanisms of disease

Obesity is prevalent among pregnant women in the United States; 15-20% of obese pregnant women have obstructive sleep apnea. The prevalence of obstructive sleep apnea increases along with body mass index, age and in the presence of other co-morbidities. Untreated obstructive sleep apnea in women is associated with a range of cardiovascular, pulmonary and metabolic co-morbidities; recent studies suggest that women with obstructive sleep apnea in pregnancy may be at significantly greater risk of entering pregnancy with chronic hypertension and/or of developing hypertensive disorders of pregnancy: gestational hypertension; preeclampsia; or eclampsia. This has serious public health implications; hypertensive disorders of pregnancy are a major cause of maternal and neonatal morbidity and mortality and are associated with a greater lifetime risk for cardiovascular disease. The mechanisms that associated obstructive sleep apnea with hypertensive disorders of pregnancy have not been defined, but several pathways are scientifically plausible. In this review, we will present a comprehensive literature review of the following: the associations between obstructive sleep apnea and hypertensive disorders of pregnancy; the proposed mechanisms that may connect obstructive sleep apnea and hypertensive disorders of pregnancy; and the effectiveness of treatment at mitigating these adverse outcomes.

Obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is increasing in prevalence due to rising obesity. While OSA is a disorder primarily of the upper airway during sleep, its pathophysiological impact on other body systems is increasingly recognised. There has been interest in the prevalence of OSA in different ophthalmic conditions and possible causation has been postulated. As OSA is common, it can be expected that people with co-existent OSA will be found in any ophthalmic disease population studied. To determine with confidence the significance of finding patients with OSA in a particular cohort requires a well matched control group, ideally matched for age, obesity, gender and co-morbidities. Only if one can say with certainty that the prevalence of OSA is higher in a group with a particular co-existent ophthalmic disease can we begin to speculate about possible mechanisms for the overlap in these conditions. Possible mechanisms for how OSA might affect the eye are discussed in this review. The current literature is reviewed with respect to diabetic retinopathy, glaucoma, floppy eyelid syndrome, non-arteritic ischaemic optic neuropathy, keratoconus and AMD. Associations with OSA have been found, but robust prospective studies using multi-channel sleep studies to diagnose OSA are lacking. Gaps remain in the evidence and in our knowledge. It is hoped that this review will highlight the need for ophthalmologists to consider OSA in their patients. It also makes recommendations for future research, especially to consider whether therapies for OSA can also be effective for ophthalmic disorders.

Effects of continuous positive airway pressure on cardiovascular biomarkers in patients with obstructive sleep apnea: a meta-analysis of randomized controlled trials

PURPOSE

Obstructive sleep apnea (OSA) is associated with increased levels of systemic inflammatory markers, increased arterial stiffness, and endothelial dysfunction, which may lead to increased cardiovascular risk. We aimed to quantify the effects of continuous positive airway pressure (CPAP) on cardiovascular biomarkers and to establish predictors of response to CPAP.

METHODS

We searched PubMed and the Cochrane Library from inception to May 31, 2017. Randomized controlled trials (RCTs) assessing the efficacy of CPAP on high-sensitivity C-reactive protein (hs-CRP), interleukin 6 (IL-6), tumor necrosis factor- alpha (TNF-α), augmentation index (AIx), pulse wave velocity (PWV), and flow-mediated dilatation (FMD) in patients with OSA were selected by consensus.

RESULTS

We included 15 RCTs comprising 1090 patients in the meta-analysis. The pooled standard mean difference (SMD) of effect of CPAP on hs-CRP was - 0.64 (95% confidence interval (CI) - 1.19 to - 0.09; P = 0.02). CPAP was associated with a reduction in AIx of 1.53% (95% CI, 0.80 to 2.26%; P < 0.001) and a significant increase in FMD of 3.96% (95% CI 1.34 to 6.59%; P = 0.003). Subgroup analyses found CPAP was likely to be more effective in improving FMD levels in severe OSA patients or patients with effective CPAP use ≥ 4 h/night.

CONCLUSIONS

Among patients with OSA, CPAP improves inflammatory marker hs-CRP, arterial stiffness marker AIx, and endothelial function marker FMD. These biomarkers may provide information related to response to treatment. Future studies will need to clarify the efficacy of these biomarkers in assessing cardiovascular risk reduction among OSA treated with CPAP.

CPAP Adherence Predictors in a Randomized Trial of Moderate-to-Severe OSA Enriched With Women and Minorities

BACKGROUND

Suboptimal CPAP adherence in OSA clinical trials involving predominantly white men limits interpretability and generalizability. We examined predictors of CPAP adherence in a clinical trial enriched with minorities.

METHODS

The Sleep Apnea Stress Study-a randomized, double-blind, sham-controlled trial of patients with moderate-to-severe OSA-included participants with complete 8-week adherence data (n = 138). Overnight 14-channel polysomnography, anthropometry, socioeconomic status, mood questionnaires, and week 1 CPAP adherence were analyzed via adjusted linear models relative to CPAP adherence (average minutes per night usage).

RESULTS

Overall, age was 51 ± 12 years, 55% of the patients were male, 55% were white, BMI was 36.7 ± 7.7 kg/m², and median apnea-hypopnea index was 20 (interquartile range, 13-37). In univariate analyses adherence increased with randomization to active CPAP (81 min; 95% CI, 30-132), increasing age (35 min/decade; 95% CI, 13-57), white race (78 min, 95% CI, 26-129), and per hour of week 1 adherence (41 min, 95% CI, 32-51). Active CPAP (48 min, 95% CI, 6-91), increasing age (27 min/decade, 95% CI, 10-44), and higher 1-week adherence (36 min/h, 95% CI, 27-46) were significantly associated with improved adherence in multivariable analyses. Subgroup analyses showed stronger associations of adherence with treatment arm in whites and increasing age in minorities. Increasing age and white race were more strongly associated with adherence in women.

CONCLUSIONS

In this trial with near-even sex distribution and high ethnic minority representation, we identified CPAP assignment, increasing age, and early adherence to be associated with improved adherence in addition to sex-specific and race-specific adherence differences. These results can inform targeted clinical trial adherence optimization strategies.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00607893; URL: www.clinicaltrials.gov.

CPAP Does Not Reduce Inflammatory Biomarkers in Patients With Coronary Artery Disease and Nonsleepy Obstructive Sleep Apnea: A Randomized Controlled Trial

Objectives

Obstructive sleep apnea (OSA) and enhanced vascular inflammation coexist in patients with coronary artery disease (CAD). Continuous positive airway pressure (CPAP) is first-line treatment for OSA with daytime sleepiness. This analysis of data from the RICCADSA (Randomized Intervention with CPAP in Coronary Artery Disease and Sleep Apnea) trial investigated the effects of CPAP on inflammatory markers in patients with CAD and nonsleepy OSA.

Methods

This single-center, randomized, controlled, open-label trial enrolled consecutive revascularized patients with nonsleepy OSA (apnea-hypopnea index >15/h; Epworth Sleepiness Scale score <10). Levels of high-sensitivity C-reactive protein (hs-CRP), interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) were measured in blood samples taken at baseline (median 94 days after revascularization) and after 1 year of follow-up in patients randomized to CPAP or no-CPAP.

Results

A total of 220 patients with analyzable blood samples at baseline and 1 year were included. Baseline IL-6 levels were significantly lower in the CPAP versus no-CPAP group (median 3.1 pmol/L [interquartile range 1.3-5.7] vs. 4.2 pmol/L [2.0-8.9], respectively; p = .005). At 1-year follow-up, median IL-6 levels were significantly reduced in both groups (to 2.2 pmol/L [1.2-3.9] in the CPAP group and to 2.2 [1.2-4.7] in no-CPAP group; both p < .001 vs. baseline). IL-8, hs-CRP, and TNF-α did not change significantly from baseline. There was no association between CPAP adherence and changes in inflammatory marker levels.

Conclusions

In patients with stable CAD and nonsleepy OSA, inflammatory biomarkers did not change significantly over time except for IL-6 levels, which reduced to the same extent in the CPAP and no-CPAP groups.

Clinical Trial Registration

ClinicalTrials.gov, ID: NCT00519597; researchweb.org, VGSKAS-4731.

Oxidative and carbonyl stress in pregnant women with obstructive sleep apnea

PURPOSE

Pregnant women are particularly susceptible to sleep-disordered breathing. Obstructive sleep apnea (OSA) in pregnancy is associated with poor pregnancy and fetal outcomes. Oxidative stress caused by intermittent hypoxemia and reoxygenation may impact pregnancy health. We hypothesize that pregnant women with OSA have a pronounced oxidative stress profile.

METHODS

A case-control study was performed to study oxidative stress markers in the serum of pregnant women with or without OSA. Patients with OSA were identified between 2003 and 2009. Contemporaneous controls were pregnant subjects without apnea, gasping, or snoring around the time of delivery. Serum markers of oxidative and carbonyl stress were measured by spectrophotometric/fluorometric methods. Multiple linear regression analysis was used with a model including age, body mass index at delivery, history of diabetes, and gestational age.

RESULTS

Serum samples from 23 OSA cases and 41 controls were identified. Advanced oxidation protein products, a marker for oxidative stress, and advanced glycation end products (AGEs), a marker for carbonyl stress, were significantly lower in women with OSA than in controls (p value <0.0001). Total antioxidant capacity was higher in women with OSA in comparison to controls (p value <0.0001). The difference in AGEs remained significant even after adjusting for confounders.

CONCLUSION

Contrary to our hypothesis, the results of this study suggest that pregnant women with OSA have higher antioxidant capacity and lower oxidative and carbonyl stress markers compared to controls, suggesting a possible protective effect of intermittent hypoxia. Whether OSA in pregnancy impacts oxidative stress differently than OSA in the general population remains to be confirmed.

Determinants of sleepiness in obstructive sleep apnea

STUDY OBJECTIVES

Significant interindividual variability in sleepiness is observed in clinical populations with obstructive sleep apnea (OSA). This phenomenon is only partially explained by the apnea-hypopnea index (AHI). Understanding factors that lead to sleepiness is critical to effective management of patients with OSA. We examined demographic and other factors associated with sleepiness in OSA.

METHODS

Prospective study of 283 patients with newly diagnosed OSA by polysomnography (AHI ≥ 5 per hour). Subjective sleepiness (Epworth Sleep Scale [ESS] ≥ 11) and objective sleepiness (psychomotor vigilance task [PVT] mean lapse ≥ 2) were assessed.

RESULTS

Participants were classified into four groups (1: sleepy by ESS and PVT, 2: sleepy by PVT only, 3: sleepy by ESS only, and 4: nonsleepy reference group) and compared by generalized logit model. Shorter daily sleep duration by actigraphy and less morningness were associated with higher risk of sleepiness (Odds ratio [OR] = 0.52, 95% confidence interval [CI] 0.33-0.82 and OR = 0.89, CI 0.80-0.98, respectively). African-American race was associated with sleepiness (group 1, OR = 8.8, CI 2.8-27.3; group 2, OR = 16.6, CI 3.3-83.6; and group 3, OR = 3.3, CI 1.0-10.1). IL-6 level was higher in groups 1 and 3 (OR = 1.9, CI 1.0-3.4 and OR 2.0, CI 1.1-3.7, respectively).

CONCLUSIONS

African-American race, short sleep duration, chronotype, and increased proinflammatory cytokine IL-6 level were associated with sleepiness in OSA. These findings will inform future investigations determining mechanisms of sleepiness in OSA.

Intermittent hypoxia, cardiovascular disease and obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is a common disorder and is associated with cardiovascular disease. Continuous positive airway pressure (CPAP), whilst reducing blood pressure, has not been shown to reduce cardiovascular events when used as a treatment solely for this purpose in patients with previous cardiovascular disease. Developing a better understanding of the mechanisms underlying cardiovascular disease in OSA is important to develop new treatments. Potential causative mechanisms for cardiovascular disease in OSA include arousal induced sympathetic activation, large intrathoracic pressure swings leading to shear stress on the heart and great vessels, and intermittent hypoxia (IH). This review discusses the role of IH, as a major physiological consequence of OSA, in the development of cardiovascular disease.

Verifying the Relative Efficacy between Continuous Positive Airway Pressure Therapy and Its Alternatives for Obstructive Sleep Apnea: A Network Meta-analysis

Obstructive sleep apnea (OSA) is a common breathing disorder, and continuous positive airway pressure (CPAP) therapy together with its alternatives has been developed to treat this disease. This network meta-analysis (NMA) was aimed to compare the efficacy of treatments for OSA. Cochrane Library, MEDLINE, and Embase were searched for eligible studies. A conventional and NMA was carried out to compare all therapies. Sleeping characteristics, including Apnea–Hypopnea Index (AHI), Epworth Sleepiness Scale (ESS), arterial oxygen saturation, and arousal index (AI), and changes of blood pressure were selected as outcomes. A total of 84 studies were finally included after rigorous screenings. For the primary outcomes of AHI and ESS, the value of auto-adjusting positive airway pressure (APAP), CPAP, and oral appliance (OA) all showed statistically reduction compared with inactive control (IC). Similar observation was obtained in AI, with treatments of the three active interventions. A lower effect of IC in SaO₂ was exhibited when compared with APAP, CPAP, and OA. Similar statistically significant results were presented in 24 h systolic blood pressure and 24 h DBP when comparing with CPAP. Our NMA identified CPAP as the most efficacious treatment for OSA patients after the evaluation of sleeping characteristics and blood pressures. In addition, more clinical trials are needed for further investigation due to the existence of inconsistency observed in this study.