Effect of continuous positive airway pressure on soluble CD40 ligand in patients with obstructive sleep apnea syndrome

Association of Tumor Necrosis Factor-Alpha, Interleukin-1β, Interleukin-8, and Interferon-γ with Obstructive Sleep Apnea in Both Children and Adults: A Meta-Analysis of 102 Articles

Background: Cytokines may have a significant impact on sleep regulation. In this meta-analysis, we present the serum/plasma levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-8, IL-1β, and interferon-gamma (IFN-γ) in both children and adults with obstructive sleep apnea (OSA) in comparison to controls. Methods: Four electronic databases were systematically searched (PubMed, Web of Science, Scopus, and Cochrane Library) through 19 October 2023, without any restrictions on language, date, age, and sex. We used Review Manager version 5.3 to perform meta-analysis and presented the data as standardized mean difference (SMD) and 95% confidence interval (CI) values to evaluate the relationships between the levels of cytokines and OSA. Results: A total of 102 articles (150 independent studies) were included in the meta-analysis. The pooled SMDs in adults were 1.42 (95%CI: 1.11, 1.73; p < 0.00001), 0.85 (95%CI: 0.40, 1.31; p = 0.0002), 0.69 (95%CI: 0.22, 1.16; p = 0.004), and 0.39 (95%CI: -0.37, 1.16; p = 0.31) for TNF-α, IL-8, IL-1β, and IFN-γ, respectively. The pooled SMDs in children were 0.84 (95%CI: 0.35, 1.33; p = 0.0008), 0.60 (95%CI: 0.46, 0.74; p < 0.00001), 0.25 (95%CI: -0.44, 0.93; p = 0.49), and 3.70 (95%CI: 0.75, 6.65; p = 0.01) for TNF-α, IL-8, IL-1β, and IFN-γ, respectively. Conclusions: The levels of proinflammatory cytokines of TNF-α, IL-8, and IL-1β in adults, and TNF-α, IL-8, and IFN-γ in children with OSA, are significantly higher than those in controls.

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

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

Integrative analysis of key candidate genes and signaling pathways in acute coronary syndrome related to obstructive sleep apnea by bioinformatics

Although obstructive sleep apnea (OSA) has been clinically reported to be associated with acute coronary syndrome (ACS), the pathogenesis between the two is unclear. Herein, we analyzed and screened out the prospective molecular marker. To explore the candidate genes, as well as signaling cascades involved in ACS related to OSA, we extracted the integrated differentially expressed genes (DEGs) from the intersection of genes from the Gene Expression Omnibus (GEO) cohorts and text mining, followed by enrichment of the matching cell signal cascade through DAVID analysis. Moreover, the MCODE of Cytoscape software was employed to uncover the protein-protein interaction (PPI) network and the matching hub gene. A total of 17 and 56 integrated human DEGs in unstable angina (UA) and myocardial infarction (MI) group associated with OSAs that met the criteria of |log2 fold change (FC)|≥ 1, adjusted P < 0.05, respectively, were uncovered. After PPI network construction, the top five hub genes associated with UA were extracted, including APP, MAPK3, MMP9, CD40 and CD40LG, whereas those associated with MI were PPARG, MAPK1, MMP9, AGT, and TGFB1. The establishment of the aforementioned candidate key genes, as well as the enriched signaling cascades, provides promising molecular marker for OSA-related ACS, which will to provide a certain predictive value for the occurrence of ACS in OSA patients in the future.

Association between tumor necrosis factor alpha and obstructive sleep apnea in adults: a meta-analysis update

BACKGROUND

Tumor necrosis factor-α (TNF-α) has been reported to play a part in the development of obstructive sleep apnea (OSA) and its complications. However, the relationship between TNF-α and OSA still remains inconclusive. We aimed to systematically review and synthesize studies published to date on association between the two in adults.

METHODS

We searched for English-language articles containing original human data from case-control study studies in adults≥18 years of age. The selection criteria were set according to the PICOS framework. Articles were independently reviewed by three investigators. Data regarding demographics, clinical characteristics, and TNF-α levels were obtained. A random-effects model was applied to evaluate the overall effect sizes by calculating standard mean difference (SMD) and its 95% confidence intervals (CIs).

RESULTS

Of 393 identified abstracts, 50 articles (3503 OSA patients and 3379 health controls) were ultimately included in this meta-analysis. The results indicated that the TNF-α level in patients with OSA was 1.77 (95%CI, 1.37 to 2.17, I² = 97.8%, P < 0.0001) times higher than in the control group. Subgroup analyses showed a positive correlation between the level of TNF-α and OSA severity. According to meta-regression, we noted that aging significantly predicted an increased effect size of TNF-α level in OSA patients (P < 0.007).

CONCLUSION

This study identified a significant association between OSA and elevated TNF-α level in adults. Meanwhile, TNF-α levels were consistently correlated with severity of OSA, which indicated it might be a promising biomarker for the development of OSA. However, well-designed, large-scale, case-control cohorts are needed to better understand the relationship of TNF-α in the context of adult OSA.

Serum and Plasma Tumor Necrosis Factor Alpha Levels in Individuals with Obstructive Sleep Apnea Syndrome: A Meta-Analysis and Meta-Regression

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is associated with a variety of inflammatory factors. Specifically, proinflammatory cytokines appear to be associated with the pathogenesis of OSAS.

METHODS

For the present meta-analysis and meta-regression on serum and plasma tumor necrosis factor alpha (TNF-α) levels in individuals with and without OSAS, we performed a systematic search without any restrictions of the PubMed/Medline, Scopus, Cochrane Library, and Web of Science databases to find relevant articles published up to February 1, 2020.

RESULTS

Fifty-five (adults: 29 studies on serum and 17 studies on plasma; children: 4 studies on serum and 5 studies on plasma) were included and analyzed. Always compared to age-matched healthy controls, the pooled MDs were as follows: adults, serum: 10.22 pg/mL (95% CI = 8.86, 11.58; p < 0.00001); adults, plasma: 5.90 pg/mL (95% CI = 4.00, 7.80; p < 0.00001); children, serum: 0.21 pg/mL (95% CI = 0.05, 0.37; p = 0.01); children, plasma: 5.90 pg/mL (95% CI = 4.00, 7.80; p < 0.00001).

CONCLUSIONS

Compared to healthy and age-matched controls, adult individuals with OSAS had significantly higher serum/plasma TNF-α levels. For children with OSAS, significantly higher levels were observed for TNF-α in serum but not in plasma.

Increased platelet activation in sleep apnea subjects with intermittent hypoxemia

PURPOSE

Obstructive sleep apnea (OSA) is independently associated with increased risk for stroke and other cardiovascular diseases. Since activated platelets play an important role in cardiovascular disease, the objective of this study was to determine whether platelet reactivity was altered in OSA subjects with intermittent nocturnal hypoxemia.

METHODS

Thirty-one subjects, without hypertension or cardiovascular disease and not taking medication, participated in the study. Subjects were stratified based on OSA-related oxygen desaturation index (ODI) recorded during overnight polysomnography. Platelet reactivity to a broad panel of agonists (collagen, thrombin, protease-activated receptor1 hexapeptide, epinephrine, ADP) was measured by monitoring platelet aggregation and ATP secretion. Expression of platelet activation markers CD154 (CD40L) and CD62P (P-selectin) and platelet-monocyte aggregates (PMA) was quantified by flow cytometry.

RESULTS

Epinephrine-induced platelet aggregation was substantially decreased in OSA subjects with significant intermittent hypoxemia (ODI ≥ 15) compared with subjects with milder hypoxemia levels (ODI < 15) (area under curve, p = 0.01). In addition, OSA subjects with ODI ≥ 15 exhibited decreased thrombin-induced platelet aggregation (p = 0.02) and CD40L platelet surface expression (p = 0.05). Platelet responses to the other agonists, CD62P platelet surface expression, and PMA levels were not significantly different between groups. Reduction in platelet responses to epinephrine and thrombin, and decreased CD40L surface marker expression in significant hypoxemic OSA individuals, is consistent with their platelets being in an activated state.

CONCLUSIONS

Increased platelet activation was present in otherwise healthy subjects with intermittent nocturnal hypoxemia due to underlying OSA. This prothrombotic milieu in the vasculature is likely a key contributing factor toward development of thrombosis and cardiovascular disease.

TRIAL REGISTRATION

NCT00859950.

Tumor necrosis factor alpha is a promising circulating biomarker for the development of obstructive sleep apnea syndrome: a meta-analysis

Obstructive sleep apnea syndrome (OSAS) is a chronic inflammatory disorder. The relationship between tumor necrosis factor alpha (TNF-alpha) and OSAS has been widely evaluated, but the results thus far remain inconclusive. We thereby decided to quantify the changes of TNF-alpha between OSAS patients and controls by a meta-analysis. This study complies with the MOOSE guidelines. Two reviewers independently searched articles and abstracted relevant data. In total, 47 articles (59 studies) were analyzed, including 2857 OSAS patients and 2115 controls. Overall, OSAS patients had a significantly higher level of circulating TNF-alpha than controls (weighted mean difference [WMD]: 9.66 pg/mL, 95% confidence interval [CI]: 8.66 to 11.24, P<0.001), but with significant heterogeneity (I²: 99.7%). After adjusting for potential missing studies, the overall estimate was weakened but still significant (filled WMD: 2.63 pg/mL, 95% CI: 2.56 to 2.70, P<0.001). When studies were stratified by OSAS severity, the changes in circulating TNF-alpha between patients and controls increased gradually with the more severe grades of OSAS. In patients with mild, mild-to-moderate, moderate, moderate-to-severe and severe OSAS, circulating TNF-alpha was higher than respective controls by 0.99, 1.48. 7.79, 10.08 and 8.85 pg/mL, with significant heterogeneity (I²: 91.2%, 74.5%, 97.6%, 99.0% and 98.1%). In conclusion, our findings demonstrated that circulating TNF-alpha was significantly higher in OSAS patients than in controls, and this difference became more pronounced with the more severe grades of OSAS, indicating that TNF-alpha might be a promising circulating biomarker for the development of OSAS.

Is there an effect of obstructive sleep apnea syndrome on oxidative stress and inflammatory parameters in patients with craniofacial anomalies?

The aim of this study was to test the hypothesis that obstructive sleep apnea syndrome (OSAS) exhibits oxidative stress and inflammation in patients who have a congenital, craniofacial anomaly.This prospective, cross-sectional cohort study included ambulant sleep study data to asses OSAS in patients with syndromic craniosynostosis and Treacher Collins syndrome. Laboratory analyses were performed including malondialdehyde, tumor necrosis factor α (TNF-α), interleukin 6, and high-sensitivity C-reactive protein.Forty-eight patients were included; 11 were adults; 37 were children. The patients' body mass indexes were normal, with a median (SD) of 0.7 (-1.82 to 2.48) in children and 20.5 (15.2-29.4) in adults. Obstructive sleep apnea syndrome was diagnosed in 23 of 48 patients. It was mild (median obstructive apnea-hypopnea index [oAHI], 2.3; oxygenation-desaturation index [ODI], 0.9) in 16 patients and moderate/severe in 7 patients (median oAHI, 10.8; ODI, 5.0). Neither oxidative stress nor inflammation had a correlation with the oAHI and ODI. Only TNF-α was found significantly higher in both the OSAS and non-OSAS groups compared with the reference values (median, 15.1 pg/mL and 12.3 pg/mL versus 4.05 [0.0-8.1 pg/mL], P < 0.001 and P < 0.001, respectively).Based on our findings we conclude that (mainly mild) OSAS, oxidative stress, as well as high-sensitivity C-reactive protein and interleukin 6 levels are not abnormal in the day time in a population of nonobese patients with a craniofacial anomaly. The increased level of TNF-α cannot be explained by OSAS. Future research should focus on mapping chronobiologic changes for further interpretation of the results.

Effects of moderate-to-severe obstructive sleep apnea on the clinical manifestations of plaque vulnerability and the progression of coronary atherosclerosis in patients with acute coronary syndrome

AIMS

It is unclear whether obstructive sleep apnea (OSA) increases the recurrence of acute coronary syndrome (ACS) in patients with acute myocardial infarction (MI). We hypothesized that moderate-to-severe OSA increased the number of adverse cardiovascular events in patients who underwent primary percutaneous coronary intervention (PCI).

METHODS AND RESULTS

This study included 272 patients with acute MI. Polysomnography at first admission determined that 124 patients suffered from moderate-to-severe OSA. The main study outcome measures were cardiac death, recurrence of ACS, and re-admission for heart failure. Major adverse cardiac events (MACEs) were defined as composite end points of individual clinical outcomes. Follow-up coronary angiograms were obtained in 222 patients. PCI-related measures were target vessel revascularization and newly necessitated PCI for progressive lesions. The moderate-to-severe OSA patients had increased ACS recurrence and MACEs compared with patients with mild OSA or without sleep apnea (16% vs. 7%, p = 0.014; 22% vs. 11%, p = 0.014, respectively). PCI for progressive lesions was also higher in the moderate-to-severe OSA patients (28% vs. 15%, p = 0.015). Cox regression analysis showed that moderate-to-severe OSA was an independent predictor of ACS recurrence (hazard ratio = 2.30, p = 0.040). In addition, moderate-to-severe OSA was an independent predictor of PCI for progressive lesions, with a hazard ratio of 2.38 (p = 0.015).

CONCLUSIONS

Moderate-to-severe OSA increased the risk of ACS and the incidence of PCI for progressive lesions. Increased plaque vulnerability might be related to these clinical manifestations.

Soluble ligand CD40 and uric acid as markers of atheromatosis in patients with obstructive sleep apnea

The aim of the study was to evaluate the risk of atheromatosis in patients with obstructive sleep apnea (OSA), as based on the concentration of the pro-atherogenic soluble CD40L ligand (sCD40L) in relation to the level of uric acid. The serum levels of sCD40L and uric acid were measured in 79 OSA patients (mean apnea/hypopnea index - AHI 34.4 ± 20.9) and in 40 healthy controls. We found that sCD40L was higher in the OSA patients with hyperuricemia than that in the patients with uric acid in the normal range (sCD40L: 9.0 ng/ml vs. 8.0 ng/ml, respectively, p < 0.05). There was a positive association of sCD40L with AHI (p = 0.01) and a negative one with the mean minimal nocturnal SaO₂(p < 0.05). Uric acid correlated negatively with the mean and minimal SaO₂and positively with the oxygen desaturation index (p < 0.05). OSA patients with hyperuricemia also had a higher prevalence of hypertension and ischemic heart disease. We conclude that OSA patients with increased uric acid concentration have increased risk of atheromatosis, as indicated by a higher level of soluble pro-atherogenic ligand CD40, and a higher prevalence of cardiovascular adverse events.

Obstructive sleep apnea and endothelial progenitor cells

BACKGROUND

Obstructive sleep apnea (OSA) occurs in 4% of middle-aged men and 2% of middle-aged women in the general population, and the prevalence is even higher in specific patient groups. OSA is an independent risk factor for a variety of cardiovascular diseases. Endothelial injury could be the pivotal determinant in the development of cardiovascular pathology in OSA. Endothelial damage ultimately represents a dynamic balance between the magnitude of injury and the capacity for repair. Bone marrow-derived endothelial progenitor cells (EPCs) within adult peripheral blood present a possible means of vascular maintenance that could home to sites of injury and restore endothelial integrity and normal function.

METHODS

We summarized pathogenetic mechanisms of OSA and searched for available studies on numbers and functions of EPCs in patients with OSA to explore the potential links between the numbers and functions of EPCs and OSA. In particular, we tried to elucidate the molecular mechanisms of the effects of OSA on EPCs.

CONCLUSION

Intermittent hypoxia cycles and sleep fragmentation are major pathophysiologic characters of OSA. Intermittent hypoxia acts as a trigger of oxidative stress, systemic inflammation, and sympathetic activation. Sleep fragmentation is associated with a burst of sympathetic activation and systemic inflammation. In most studies, a reduction in circulating EPCs has emerged. The possible mechanisms underlying the decrease in the number or function of EPCs include prolonged inflammation response, oxidative stress, increased sympathetic activation, physiological adaptive responses of tissue to hypoxia, reduced EPC mobilization, EPC apoptosis, and functional impairment in untreated OSA. Continuous positive airway pressure (CPAP) therapy for OSA affects the mobilization, apoptosis, and function of EPCs through preventing intermittent hypoxia episodes, improving sleep quality, and reducing systemic inflammation, oxidative stress levels, and sympathetic overactivation. To improve CPAP adherence, the medical staff should pay attention to making the titration trial a comfortable first CPAP experience for the patients; for example, using the most appropriate ventilators or proper humidification. It is also important to give the patients education and support about CPAP use in the follow-up, especially in the early stage of the treatment.

Serum inflammatory markers in obstructive sleep apnea: a meta-analysis

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) has been linked to and is associated with increased cardiovascular and cerebrovascular morbidity. Ongoing inflammatory responses play an important role in this association. Multiple small size studies addressing the profile of the inflammatory markers in OSA are available therefore we performed a meta-analysis.

METHODS

Systematic review of medical literature was conducted using PubMed, Cochrane, and EMBASE databases from 1968 to 2011 by utilizing the key words obstructive sleep apnea, C-Reactive protein, tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), interleukin 8 (IL-8), intercellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM) and Selectins. Inclusion criteria were: full text English articles; studies with adult population; reported values for at least one of the markers of interest; with at least two separate groups (subjects with OSA and control group); OSA was defined as AHI of ≥ 5/h.

RESULTS

Five hundred and twelve studies were reviewed for inclusion with 51 studies pooled for analysis (30 studies for CRP, 19 studies for TNF-α, 8 studies for ICAM, 18 studies for IL-6, six studies for VCAM and 5 studies for Selectins). The levels of inflammatory markers were higher in patients with OSA compared to control group. Standardized pooled Mean differences were calculated to be 1.77 for CRP, 1.03 for TNF-α, 2.16 for IL-6, 4.22 for IL-8, 2.93 for ICAM, 1.45 for Selectins and 2.08 for VCAM.

CONCLUSIONS

In this meta-analysis, the levels of systemic inflammatory markers were found to be higher in OSA patients compared to control subjects.

Effects of continuous positive airway pressure therapy on systemic inflammation in obstructive sleep apnea: a meta-analysis

OBJECTIVES

Our meta-analysis was performed to estimate the effect of continuous positive airway pressure (CPAP) therapy on systemic inflammation in patients with obstructive sleep apnea (OSA).

METHODS

A comprehensive literature search of PubMed and EMBASE was performed for literature published up to January 2013. Standardized mean difference (SMD) was calculated to estimate the treatment effects of pre- and post-CPAP therapy.

RESULTS

A total of 35 studies involving 1985 OSA patients were included in the meta-analysis. Each study investigated one or more inflammatory markers: 24 studies on C-reactive protein (CRP), 16 studies on IL-6, 3 studies on IL-8, and 12 studies on tumor necrosis factor α (TNF-α). The results showed that the SMD (95% confidence interval [CI]) for CRP, IL-6, IL-8, and TNF-α were 0.452 (95% CI, 0.252-0.651), 0.299 (95% CI, 0.001-0.596), 0.645 (95% CI, 0.362-0.929), and 0.478 (95% CI, 0.219-0.736) in pre- and post-CPAP therapy, respectively. The subgroup analyses seemed to support better benefits with therapy duration of ≥3 months and more adequate compliance (≥4 h/night).

CONCLUSIONS

CPAP therapy could partially suppress systemic inflammation in OSA patients, and substantial differences were present among the various inflammatory markers.

Serum proteomic changes in adults with obstructive sleep apnoea

To examine whether differentially expressed proteins are present in the serum of patients with obstructive sleep apnoea (OSA), iTRAQ techniques (isobaric tags for relative and absolute quantification) were employed in a prospective study. Individuals were assigned to either a non-OSA control group (apnoea-hypopnoea index, AHI <5) or an OSA group (AHI ≥5). Blood samples were collected, aliquoted and frozen at -80 °C. Protein digestion and tagging with iTRAQ4plex® and mass spectrometry analysis was then performed (MALDI TOF/TOF). Ten male subjects were included in the control group (age = 45 ± 9.7 years) and 30 male patients in the OSA group (age = 45 ± 10.7 years), the latter being then subdivided into three severity groups. A total of 103 proteins were identified with differential levels between patients with OSA and controls. Of these, 11 proteins were underexpressed and 19 were overexpressed in patients with OSA. C4BPA and thrombospondin were underexpressed in all three OSA severity groups. Among the overexpressed proteins, 13 were overexpressed in the mild OSA group, seven in the moderate group and five in the severe group. Analysis of interactions between the identified proteins revealed that protein alterations in OSA are primarily associated with derangements in lipid and vascular metabolic pathways. This study provides initial evidence that differential protein expression occurs in adults with OSA, and that such proteins change according to disease severity, and appear to primarily involve lipid and vascular metabolic pathways.

Obstructive sleep apnoea as a risk factor for atherosclerosis - implication for preventive and personalised treatment

Atherosclerosis with its manifestations and associated diseases is a main cause of morbidity and mortality in industrial countries. The pathomechanisms underlying atherosclerosis are complex and comprise exogenous factors as well as genetic predisposition. Beyond the well-defined risk factors for the development of atherosclerosis, obstructive sleep apnoea (OSA) merits more and more attention. A growing body of evidence has associated OSA with vascular pathologies. Although the exact mechanisms involved are not known, the occurrence of intermittent hypoxia typical for OSA may lead to oxidative stress, inflammation, metabolic and neural changes which in turn are responsible for vessel dysfunction underlying atherosclerosis. It has been demonstrated that therapy with continuous positive airway pressure (CPAP) plays a vasoprotective role. This review summarises data resulting from epidemiological and clinical studies with emphasis on the possible mechanisms linking OSA with atherosclerosis, predictive biomarkers helping identify OSA patients at high cardiovascular risk and personalised treatment approaches.

Obstructive sleep apnea syndrome: natural history, diagnosis, and emerging treatment options

Sleep apnea is an entity characterized by repetitive upper airway obstruction resulting in nocturnal hypoxia and sleep fragmentation. It is estimated that 2%-4% of the middle-aged population has sleep apnea with a predilection in men relative to women. Risk factors of sleep apnea include obesity, gender, age, menopause, familial factors, craniofacial abnormalities, and alcohol. Sleep apnea has been increasingly recognized as a major health burden associated with hypertension and increased risk of cardiovascular disease and death. Increased airway collapsibility and derangement in ventilatory control responses are the major pathological features of this disorder. Polysomnography (PSG) is the gold-standard method for diagnosis of sleep apnea and assessment of sleep apnea severity; however, portable sleep monitoring has a diagnostic role in the setting of high pretest probability sleep apnea in the absence of significant comorbidity. Positive pressure therapy is the mainstay therapy of sleep apnea. Other treatment modalities, such as upper airway surgery or oral appliances, may be used for the treatment of sleep apnea in select cases. In this review, we focus on describing the sleep apnea definition, risk factor profile, underlying pathophysiologic mechanisms, associated adverse consequences, diagnostic modalities, and treatment strategies.

Patients with severe obstructive sleep apnea syndrome and elevated high-sensitivity C-reactive protein need priority treatment

OBJECTIVE

To evaluate the clinical factors predicting the significantly elevated high-sensitivity C-reactive protein (hs-CRP) concentrations, defined herein as hs-CRP > or = 3 mg/L, in adult males with untreated obstructive sleep apnea syndrome (OSAS).

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

Sixty-five consecutive male patients with newly diagnosed OSAS were enrolled to receive complete medical history review, physical examination, in-laboratory overnight polysomnography, and hs-CRP test. The patients had no current or history of cardiovascular disease. The patients had a mean age of 38.2 +/- 9.9 years, body mass index (BMI) of 27.4 +/- 3.5 kg/m(2), and Epworth Sleepiness Scale (ESS) of 11.3 +/- 4.6. The serum levels of hs-CRP were assessed using peripheral venous blood samples.

RESULTS

Twenty-three percent of the overall patients had significantly elevated serum levels of hs-CRP. The increase of hs-CRP correlated fairly with BMI, apnea-hypopnea index (AHI), tonsil size, and ESS (r = 0.450, 0.398, 0.393, and 0.300, respectively; all P < or = 0.05) after adjustment for conventional coronary heart disease risk factors. However, only the AHI could predict for significantly elevated hs-CRP after stepwise multiple linear regression (R(2) = 0.251, P < 0.001).

CONCLUSION

Patients in this study with hs-CRP > or = 3 mg/L were more prevalent in the severe OSAS group. This observation suggests that the severe OSAS patients need to have their cardiovascular statuses evaluated by use of an hs-CRP screening test.

Repeated inspiratory occlusions in anesthetized rats acutely increase blood coagulability as assessed by thromboelastography

Many of the components contributing to coagulability are enhanced by repeated episodes of hypoxia, as occurs in obstructive sleep apnea, but no one has yet measured the global hemostatic properties of blood in an animal model of this disease. Using thromboelastography, a hemostatic assay, we measured hemostasis in six pentobarbital-anesthetized rats before and after 3h of repeated inspiratory occlusions lasting 30s applied every 2 min and compared the results to those in six identically prepared rats before and after 3h of resting breathing. Rats subjected to occlusions displayed faster onset of clotting (p<0.031) and more rapid coagulation (p<0.031). Thus, repeated inspiratory occlusions acutely cause hypercoagulability in rats. Thromboelastography, a simple test of hemostasis, may help evaluate the factors responsible for this increase and, in patients with obstructive sleep apnea, the risk of future cardiovascular disease.

Obstructive sleep apnea and cardiovascular disease: a perspective and future directions

Data from animal and human studies provide a biological plausibility to the notion that obstructive sleep apnea activates pathways that lead to insulin resistance, atherosclerosis and hypertension. Sleep apnea thus activates the same pathways as does obesity. That obstructive sleep apnea is a risk factor for cardiovascular disease is supported by epidemiological association studies. Longitudinal cohort studies also provide evidence that patients with untreated severe sleep apnea have an increased rate of cardiovascular events. But these studies, while highly suggestive, do not provide the evidence needed to convince the skeptic. This would only be obtained by randomized treatment trials with hard cardiovascular endpoints such as cardiac events and deaths. While such studies are in the planning stages, they will be challenging. There are issues about randomizing individuals with severe sleep apnea and excessive sleepiness into no therapy, since they are at known increased risk for car crashes. Thus, lack of therapy puts others on the road at risk as well as the subject with sleep apnea. There is, moreover, the concern that treating obstructive sleep apnea in very obese individuals will have little impact, since any effect of therapy for OSA will be overwhelmed by the effects of obesity itself. Data from randomized treatment trials for cardiovascular endpoints will likely not be available for many years. In the interim, physicians need to consider how to treat such patients. It is proposed that given that CPAP treatment for obstructive sleep apnea is highly effective and essentially totally safe, and that the evidence is suggestive that sleep apnea is a risk factor for cardiovascular disease, then we propose all patients with severe sleep apnea should be treated to reduce cardiovascular risk.

The roles of TNF-alpha and the soluble TNF receptor I on sleep architecture in OSA

Objective

Patients with obstructive sleep apnea (OSA) have been described to have increased levels of inflammatory cytokines (particularly TNF-α) and have severely disturbed sleep architecture. Serum inflammatory markers, even in normal individuals, have been associated with abnormal sleep architecture. Not much is known about the role the TNF receptor plays in the inflammation of OSA nor if it is associated with changes in sleep architecture or arousals during the night. We hypothesized that the TNF receptor might play an important role in the inflammation as well as sleep architecture changes in patients with OSA.

Design

Thirty-six patients with diagnosed (AHI > 15) but untreated OSA were enrolled in this study. Baseline polysomnograms as well as TNF-α and soluble TNF receptor I (sTNF-RI) serum levels were obtained on all patients. We evaluated the association between serum levels of TNF-α and sTNF-RI with various polysomongraphic characteristics, including sleep stages and EEG arousals.

Results

sTNF-RI levels were significantly correlated with snore arousals (r value 0.449, p value 0.009), spontaneous movement arousals (r value 0.378, p value 0.025), and periodic limb movement arousals (r value 0.460, p value 0.008). No statistically significant correlations were observed with TNF-α to any polysomnographic variables. To control for statistical significance with multiple comparisons, a MANOVA was performed with TNF-α and sTNF-RI as dependent variables and sleep architecture measures and arousals as independent variables. The model for sTNF-RI was statistically significant (F value 2.604, p value 0.03), whereas the model for TNF-α was not, suggesting sleep quality significantly affects sTNF-RI. Hierarchal linear regression analysis demonstrated that sTNF-RI was independently associated with spontaneous movement arousal index scores after controlling for age, body mass index, and sleep apnea severity.

Conclusions

These findings suggest that sTNF-RI is associated with arousals during sleep, but not with other measures in patients with OSA.

Sleep apnea: a proinflammatory disorder that coaggregates with obesity

Both obesity and sleep apnea are prevalent health conditions that frequently coaggregate. Obesity-associated inflammation may influence asthma control; the relation of sleep apnea to asthma or allergic rhinitis may be bidirectional. Both obesity and sleep apnea are associated with augmented levels of inflammation and oxidative stress, and it is biologically plausible that the proinflammatory effects of one disorder influence the expression of the other disorder. This article elucidates mechanistic associations among obesity, sleep apnea, and systemic inflammation; highlights interrelationships between these factors with cardiopulmonary disease; and identifies specific areas for future research directions.

Nocturnal reduction in circulating adiponectin concentrations related to hypoxic stress in severe obstructive sleep apnea-hypopnea syndrome

Previous reports demonstrated that adiponectin has antiatherosclerotic properties. Obstructive sleep apnea-hypopnea syndrome (OSAHS) is reported to exacerbate atherosclerotic diseases. We investigated nocturnal alternation of serum adiponectin levels before sleep and after wake-up in OSAHS patients and the effect of sustained hypoxia on adiponectin in vivo and in vitro. We measured serum adiponectin concentrations in 75 OSAHS patients and 18 control subjects before sleep and after wake-up and examined the effect of one-night nasal continuous positive airway pressure (nCPAP) on adiponectin in 24 severe OSAHS patients. We investigated the effects of hypoxia on adiponectin in mice and cultured adipocytes with a sustained hypoxia model. Circulating adiponectin levels before sleep and after wake-up were lower in severe OSAHS patients than in control subjects [before sleep: 5.9 +/- 2.9 vs. 8.8 +/- 5.6 microg/ml (P < 0.05); after wake-up: 5.2 +/- 2.6 vs. 8.5 +/- 5.5 microg/ml (P < 0.01), respectively; means +/- SD]. Serum adiponectin levels diminished significantly during sleep in severe OSAHS patients (P < 0.0001), but one-night nCPAP improved the drop in serum adiponectin levels [-18.4 +/- 13.4% vs. -10.4 +/- 12.4% (P < 0.05)]. In C57BL/6J mice and 3T3-L1 adipocytes, hypoxic exposure decreased adiponectin concentrations by inhibiting adiponectin regulatory mechanisms at secretion and transcriptional levels. The present study demonstrates nocturnal reduction in circulating adiponectin levels in severe OSAHS. Our experimental studies showed that hypoxic stress induced adiponectin dysregulation at transcriptional and posttranscriptional levels. Hypoxic stress is, at least partly, responsible for the reduction of serum adiponectin in severe OSAHS. Nocturnal reduction in adiponectin in severe OSAHS may be an important risk for cardiovascular events or other OSAHS-related diseases during sleep.

Oxidative stress in obstructive sleep apnea: putative pathways to the cardiovascular complications

Obstructive sleep apnea (OSA) is a major public health problem because of its high prevalence in morbidity and mortality. A growing body of evidence suggests that OSA is an important risk factor for cardiovascular diseases. Although the mechanism for the initiation and aggravation of cardiovascular disease has not been fully elucidated, one theorized mechanism is intermittent hypoxia, which is produced by each sleep-disordered breathing event. This repeated hypoxia and reoxygenation cycle is similar to hypoxia-reperfusion injury, which initiates oxidative stress. Recent studies have suggested that OSA is associated with increased levels of oxidative stress or antioxidant deficiencies or both. Oxidative stress is involved in the activation of redox-sensitive transcription factors, which regulate downstream products such as inflammatory cytokines, chemokines, and adhesion molecules. This pathway may be able to explain the pathogenesis of atherosclerosis, a common pathologic factor underlying all types of cardiovascular disease. In addition, endothelial dysfunction derived from oxidative stress can contribute to cardiovascular diseases. This review summarizes current available evidence for and against the occurrence of oxidative stress in OSA and discusses the putative pathways initiating cardiovascular consequences associated with OSA.

Activity-adjusted 24-hour ambulatory blood pressure and cardiac remodeling in children with sleep disordered breathing

Questions remain as to whether pediatric sleep disordered breathing increases the risk for elevated blood pressure and blood pressure-dependent cardiac remodeling. We tested the hypothesis that activity-adjusted morning blood pressure surge, blood pressure load, and diurnal and nocturnal blood pressure are significantly higher in children with sleep disordered breathing than in healthy controls and that these blood pressure parameters relate to left ventricular remodeling. 24-hour ambulatory blood pressure parameters were compared between groups. The associations between blood pressure and left ventricular relative wall thickness and mass were measured. 140 children met the inclusion criteria. In children with apnea hypopnea index <5 per hour, a significant difference from controls was the morning blood surge. Significant increases in blood pressure surge, blood pressure load, and in 24-hour ambulatory blood pressure were evident in those whom the apnea hypopnea index exceeded 5 per hour. Sleep disordered breathing and body mass index had similar effect on blood pressure parameters except for nocturnal diastolic blood pressure, where sleep disordered breathing had a significantly greater effect than body mass index. Diurnal and nocturnal systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure predicted the changes in left ventricular relative wall thickness. Therefore, sleep disordered breathing in children who are otherwise healthy is independently associated with an increase in morning blood pressure surge, blood pressure load, and 24-hour ambulatory blood pressure. The association between left ventricular remodeling and 24-hour blood pressure highlights the role of sleep disordered breathing in increasing cardiovascular morbidity.

Obstructive Sleep Apnea and Endothelial Function in School-Aged Nonobese Children

Background— Obstructive sleep apnea (OSA) in children is associated with cardiovascular morbidity such as systemic and pulmonary hypertension. However, it remains unclear whether endothelial dysfunction occurs in pediatric OSA and whether it is reversible on effective treatment of OSA.

Methods and Results— Consecutive nonobese children (aged 6 to 11 years) who were diagnosed with OSA after overnight polysomnography and control children matched on the basis of age, gender, ethnicity, and body mass index underwent blood draw the next morning for soluble CD40 ligand, asymmetric dimethylarginine (ADMA), and nitrotyrosine levels, as well as 2 iterations of 60-second cuff-occlusion tests for assessment of endothelial function. These tests were repeated 4 to 6 months after adenotonsillectomy. OSA children showed blunted reperfusion kinetics after release of occlusion, which completely normalized in 20 of 26 patients after adenotonsillectomy. All 6 children in whom no improvements occurred had a strong family history of cardiovascular disease (versus 2 of the remaining 20 patients; P <0.04). Plasma nitrotyrosine and ADMA levels were similar in OSA and control children; however, soluble CD40 ligand levels were higher in OSA children and were reduced after treatment, particularly in those with normalized hyperemic responses.

Conclusions— Postocclusive hyperemia is consistently blunted in children with OSA, and such altered endothelial function is reversible 4 to 6 months after treatment, particularly if a family history of cardiovascular disease is not present. Although no evidence for either nitric oxide–dependent oxidative/nitrosative stress or for the increased presence of the circulating nitric oxide synthase inhibitor ADMA was found in children with OSA, soluble CD40 ligand levels were increased in OSA and reflected the changes in endothelial function after treatment.

Silent Brain Infarction and Platelet Activation in Obstructive Sleep Apnea

RATIONALE

Silent brain infarction (SBI) and increased levels of soluble CD40 ligand (sCD40L) and soluble P-selectin (sP-selectin) are associated with an increased risk of cerebrovascular disease.

OBJECTIVES

The aim of this study was to evaluate whether SBI and serum levels of sCD40L and sP-selectin are increased in patients with obstructive sleep apnea (OSA).

METHODS

SBI was studied by brain magnetic resonance images in 50 male patients with OSA and 15 obese male control subjects who were free of comorbidities. In addition, the effects of 3 months of treatment with nasal continuous positive airway pressure (nCPAP) on serum parameters were studied in 24 patients with moderate to severe OSA.

MEASUREMENTS AND MAIN RESULTS

The percentage of SBI in patients with moderate to severe OSA (25.0%) was higher than that of obese control subjects (6.7%) or patients with mild OSA (7.7%). Serum levels of sCD40L and sP-selectin were significantly higher in patients with moderate to severe OSA than in obese control subjects (p < 0.05) or patients with mild OSA (p < 0.05). In addition, nCPAP significantly decreased serum levels of sCD40L (p < 0.03) and sP-selectin (p < 0.01) in patients with moderate to severe OSA.

CONCLUSIONS

These results suggest that serum levels of sCD40L and sP-selectin are elevated and SBI is more common in patients with moderate to severe OSA, leading to elevated cerebrovascular morbidity. Moreover, nCPAP may be useful for decreasing risk in patients with moderate to severe OSA.