Increased levels of circulating ICAM-1, VCAM-1, and L-selectin in obstructive sleep apnea syndrome

Analysis of genetic expression in the soft palate of patients with obstructive sleep apnea

CONCLUSION

Genetic dysregulation may be associated with development of obstructive sleep apnea (OSA).

OBJECTIVES

Genetic expression was investigated in the soft palate of patients with OSA to evaluate the biomolecular characteristics of the tissue where airway obstruction actually occurs.

METHODS

Soft palate mucosa was obtained during uvulopalatal flap surgery. Three patients with apnea/hypopnea index (AHI) >30/h and three simple snoring patients with AHI < 5/h were enrolled. After total RNA was extracted and amplified, gene expression levels were determined by microarray analysis, and relative signal intensities for each gene were evaluated.

RESULTS

Of the 45,034 genes analyzed, 137 were up-regulated in OSA patients compared with simple snorers and 95 were down-regulated. Gene network analysis showed that genes related to RNA interference and transcription were most commonly involved in the functional pathophysiology of OSA. In particular, genes encoding proliferating cell nuclear antigen and proteasome 26S subunit ATPase 6 were functionally connected with other genes.

A controlled trial of CPAP therapy on metabolic control in individuals with impaired glucose tolerance and sleep apnea

STUDY OBJECTIVES

To address whether treatment of sleep apnea improves glucose tolerance.

DESIGN

Randomized, double-blind crossover study.

SETTING

Sleep clinic referrals.

PATIENTS

50 subjects with moderate to severe sleep apnea (AHI > 15) and impaired glucose tolerance.

INTERVENTIONS

Subjects were randomized to 8 weeks of CPAP or sham CPAP, followed by the alternate therapy after a one-month washout. After each treatment, subjects underwent 2-hour OGTT, polysomnography, actigraphy, and measurements of indices of glucose control.

MEASUREMENTS AND RESULTS

The primary outcome was normalization of the mean 2-h OGTT; a secondary outcome was improvement in the Insulin Sensitivity Index (ISI (0,120). Subjects were 42% men, mean age of 54 (10), BMI of 39 (8), and AHI of 44 (27). Baseline fasting glucose was 104 (12), and mean 2-h OGTT was 110 (57) mg/dL. Seven subjects normalized their mean 2-h OGTT after CPAP but not after sham CPAP, while 5 subjects normalized after sham CPAP but not after CPAP. Overall, there was no improvement in ISI (0,120) between CPAP and sham CPAP (3.6%; 95% CI: [-2.2%, 9.7%]; P = 0.22). However, in those subjects with baseline AHI ≥ 30 (n = 25), there was a 13.3% (95% CI: [5.2%, 22.1%]; P < 0.001) improvement in ISI (0,120) and a 28.7% (95%CI: [-46.5%, -10.9%], P = 0.002) reduction in the 2-h insulin level after CPAP compared to sham CPAP.

CONCLUSIONS

This study did not show that IGT normalizes after CPAP in subjects with moderate sleep apnea and obesity. However, insulin sensitivity improved in those with AHI ≥ 30, suggesting beneficial metabolic effects of CPAP in severe sleep apnea. Clinical trials information: ClinicalTrials.gov Identifier: NCT01385995.

Evaluation of the visual function in obstructive sleep apnea syndrome patients and normal-tension glaucoma by means of the multifocal visual evoked potentials

BACKGROUND

This study was designed to objectively evaluate visual function and the causal relationship between sleep apnea and optic nerve dysfunction in patients with obstructive sleep apnea syndrome (OSAS) with or without diagnosis of normal-tension glaucoma (NTG) using multifocal visual evoked potentials (mfVEP).

METHODS

This observational, cross-sectional study assessed 20 patients with recently diagnosed OSAS with or without NTG. Diagnosis of sleep apnea was based on overnight polysomnography (ApnoeScreen). All participants underwent a complete physical and ophthalmologic examination. MfVEP recordings obtained using VERIS software (Electro-Diagnostic Imaging, San Mateo, USA), SITA-standard 30-2 automated perimetry (Humphrey Visual Field Analyzer II) and optic coherence tomography (Topcon 3D OCT-1000) exams were performed to evaluate the changes.

RESULTS

Abnormal mfVEP amplitudes defects (interocular and monocular probability analysis) were found in 40% of the eyes in the non-glaucoma group and in 90% of eyes of the NTG patients. As well, delayed mfVEP latencies (interocular and monocular probability analysis) were seen in 30 and 60% of the eyes of the non-glaucoma and NTG groups, respectively. The average RNFL (retinal nerve fiber layer) thickness was significantly reduced in the NTG eyes compared to the control database and the non-glaucoma eyes. On the Humphrey Visual Field total deviation analysis, all the NTG eyes showed significant clusters of abnormal points but none was detected in the non-glaucoma group eyes. However, the mfVEP amplitude and latency did not show any significant correlation with the standard perimetry and OCT variables, because the mfVEP technique was able to detect far more early visual defects in these patients. Systolic blood pressure, sleep efficiency, arousal index, mean and minimum arterial oxygen saturation (SaO(2)), time SaO(2) < 90%, oxyhemoglobin desaturation index, number of central and mixed apneas and apnea-hipopneas index were shown to be significantly correlated with mfVEP amplitude and latency.

CONCLUSIONS

A significant incidence of subclinical optic nerve involvement, not detected with other structural and psychophysics diagnostic techniques was seen by means of the mfVEP. In this sense, the mfVEP may be a useful diagnostic tool in the clinic for early diagnosis and monitoring of optic nerve function abnormalities in patients with OSAS.

Effect of airway inflammation on short-latency reflex inhibition to inspiratory loading in human scalene muscles

The short-latency reflex inhibition of human inspiratory muscles produced by loading is prolonged in asthma and obstructive sleep apnoea, both diseases involving airway and systemic inflammation. Both diseases also involve repetitive inspiratory loading. Although airway mucosal afferents are not critical components of the normal reflex arc, during airway inflammation, prolongation of the reflex may be caused by altered mucosal afferent sensitivity, or altered central processing of their inputs. We hypothesised that acute viral airway inflammation would replicate the reflex abnormality. The reflex was tested in 9 subjects with a "common cold" during both the acute infection and when well. Surface electrodes recorded electromyographic (EMG) activity bilaterally from scalene muscles. Latencies of the inhibitory response (IR) did not differ significantly (IR peak 67 vs 70 ms (p=0.12), and IR offset 87 vs 90 ms (p=0.23), between the inflamed and well conditions, respectively). There was no difference in any measure of the size of the reflex inhibition.

Dysfunctional nucleus tractus solitarius: its crucial role in promoting neuropathogenetic cascade of Alzheimer's dementia--a novel hypothesis

The pathophysiological mechanism(s) underlying Alzheimer's disease (AD) still remain unclear, and no disease-modifying or prophylactic therapies are currently available. Unraveling the fundamental neuropathogenesis of AD is an important challenge. Several studies on AD have suggested lesions in a number of CNS areas including the basal forebrain, hippocampus, entorhinal cortex, amygdale/insula, and the locus coeruleus. However, plausible unifying studies on the upstream factors that involve these heterogeneous regions and herald the onset of AD pathogenesis are not available. The current article presents a novel nucleus tractus solitarius (NTS) vector hypothesis that underpins several disparate biological mechanisms and neural circuits, and identifies relevant hallmarks of major presumptive causative factor(s) linked to the NTS, in older/aging individuals. Aging, obesity, infection, sleep apnea, smoking, neuropsychological states, and hypothermia-all activate inflammatory cytokines and oxidative stress. The synergistic impact of systemic proinflammatory mediators activates microglia and promotes neuroinflammation. Acutely, the innate immune response is protective defending against pathogens/toxins; however, when chronic, it causes neuroinflammation and neuronal dysfunction, particularly in brainstem and neocortex. The NTS in the brainstem is an essential multiple signaling hub, and an extremely important central integration site of baroreceptor, chemoreceptor, and a multitude of sensory afferents from gustatory, gastrointestinal, cardiac, pulmonary, and upper airway systems. Owing to persistent neuroinflammation, the dysfunctional NTS exerts deleterious impact on nucleus ambiguus, dorsal motor nucleus of vagus, hypoglossal, parabrachial, locus coeruleus and many key nuclei in the brainstem, and the hippocampus, entorhinal cortex, prefrontal cortex, amygdala, insula, and basal forebrain in the neocortex. The neuronal and synaptic dysfunction emanating from the inflamed NTS may affect its interconnected pathways impacting almost the entire CNS--which is already primed by neuroinflammation, thus promoting cognitive and neuropsychiatric symptoms. The upstream factors discussed here may underpin the neuropathopgenesis of AD. AD pathology is multifactorial; the current perspective underscores the value of attenuating disparate upstream factors--in conjunction with anticholinesterase, anti-inflammatory, immunosuppressive, and anti-oxidant pharmacotherapy. Amelioration of the NTS pathology may be of central importance in countering the neuropathological cascade of AD. The NTS, therefore, may be a potential target of novel therapeutic strategies.

Circulating levels of vascular endothelial markers in obstructive sleep apnoea syndrome. Effects of nasal continuous positive airway pressure

INTRODUCTION

Obstructive sleep apnoea syndrome (OSAS) is an important risk factor in cardiovascular disorders. Although the exact mechanism remains to be elucidated, the endothelial dysfunction process seems to be implicated.

MATERIAL AND METHODS

In order to test this hypothesis, blood circulating levels of endothelial markers were measured at baseline and 1 year after treatment with continuous positive airway pressure (CPAP). We studied 37 males using polysomnography: 20 subjects with OSAS and a 17-subject control group. An OSAS-validated sleep questionnaire covering the most important cardiovascular risk factors was applied to all subjects. Furthermore, patients received a complete general physical examination and biochemistry test with lipid profile. The specific markers measured were intercellular cell adhesion molecule-1 (ICAM-1), E-selectin, endothelin-1, von Willebrand factor (vWF) and plasminogen activator inhibitor-1 (PAI-1).

RESULTS

Obstructive sleep apnoea syndrome patients presented higher circulating levels of ICAM-1, endothelin-1 and PAI-1 than the control group. On the other hand, no differences were found in E-selectin and vWF. After 1 year of CPAP treatment, there was a significant decrease in circulating levels of ICAM-1 and PAI-1. On the other hand, no differences were found in endothelin-1, E-selectin and vWF.

CONCLUSIONS

Obstructive sleep apnoea syndrome is associated with elevated levels of ICAM-1 and PAI-1 and these levels normalize after treatment with CPAP.

Evaluation of the relationship between background factors and sleep-disordered breathing in patients with proliferative diabetic retinopathy

PURPOSE

To clarify the relationship between sleep-disordered breathing (SDB) and background factors in patients with proliferative diabetic retinopathy (PDR).

PARTICIPANTS AND METHODS

One hundred fifty-one consecutive PDR patients were included in this study. These patients' SDB parameters, including the mean and lowest SpO(2), sleeping 4% oxygen desaturation index (ODI), and cumulative percentage of time spent at SpO(2) < 90% (CT90%), were measured. Simple linear regression analyses were conducted to investigate whether the SDB parameters correlated with systemic factors for PDR, including age, duration of diabetes, HbA1c value, incidence of hypertension, estimated glomerular filtration rate (eGFR), body mass index (BMI), and insulin therapy. Logistic regression analysis was also conducted to investigate whether the SDB evaluation items were factors independently associated with the incidence of hypertension.

RESULTS

Hypertension and BMI were statistically correlated with all of the parameters. The eGFR was statistically correlated with 4% ODI and insulin therapy with the lowest SpO(2). Logistic regression analysis revealed 4% ODI and eGFR as factors independently contributing to the incidence of hypertension.

CONCLUSION

The results of our study confirmed the relationship between SDB and background factors reported to be risk factors for diabetic retinopathy progression in patients with PDR.

Vascular changes, cardiovascular disease and obstructive sleep apnea

Vascular changes related to obstructive sleep apnea (OSA) can lead to chronic cardiovascular consequences such as hypertension. The cardiovascular consequences are owing to nocturnal perturbations related to intrathoracic pressure changes, intermittent hypoxia, sympathetic neural activation, endothelial dysfunction, oxidative stress and systemic inflammation. Intermittent hypoxia due to sleep-related events in OSA activates the renin-angiotensin system and increases the levels of endothelin-1. Intermittent hypoxia also results in oxidative stress, as evidenced by elevated levels of xanthine oxidoreductase, lipid peroxidation and the presence of reactive oxygen species. There is also evidence for a decrease in antioxidant capacity. Patients with OSA may have endothelial dysfunction that resolves with continuous positive airway pressure. OSA is a state of inflammation as evidenced by elevated levels of C-reactive protein, IL-6, NF-κB, TNF-α, ICAM-1, VCAM-1 and E-selectin. This may suggest that OSA is a predisposing factor for atherogenesis. This article will discuss the role of nocturnal perturbations consequent to OSA resulting in endothelial dysfunction, oxidative stress, and inflammation and how they may subsequently play a causative role in cardiovascular disorders.

Obstructive sleep apnea and cardiovascular disease

OPINION STATEMENT

Obstructive sleep apnea is a highly prevalent disease that often goes undetected for many years before diagnosis. Although most patients seek treatment to improve symptoms of daytime sleepiness, a growing body of literature suggests that treatment may also modulate cardiovascular risk. This article summarizes the current literature regarding the associations between sleep-disordered breathing and adverse cardiovascular outcomes and reviews the lesser body of data demonstrating the cardiovascular benefits of therapy.

Effects of 10 days of modest intermittent hypoxia on circulating measures of inflammation in healthy humans

PURPOSE

Obstructive sleep apnea (OSA) is a common disease which is associated with elevated inflammatory markers and adhesion molecules, possibly due to nightly intermittent hypoxia (IH). The purpose of this study was to test the hypothesis that IH would increase systemic inflammatory markers in healthy human males.

METHODS

Healthy, young male subjects (n = 9; 24 ± 2 years) were exposed to a single daily isocapnic hypoxia exposure (oxyhemoglobin saturation = 80%, 1 h/day) for 10 consecutive days. Serum granulocyte macrophage colony-stimulating factor, interferon-γ, interleukin-1β, interleukin-6, interleukin-8, leptin, monocyte chemotactic protein-1, vascular endothelial growth factor, intracellular adhesion molecule-1, and vascular cell adhesion molecule-1 were measured before and following the 10 days of IH using Luminex.

RESULTS

Nine subjects completed the study (24 ± 2 years; 24 ± 2 kg/m(2)). The mean oxyhemoglobin saturation was 80.8 ± 1.6% during the hypoxia exposures. There was no significant change in any of the markers of inflammation (paired t test, P > 0.2 all cytokines).

CONCLUSIONS

These findings suggest that (1) a more substantial or a different pattern of hypoxemia might be necessary to activate systemic inflammation, (2) the system may need to be primed before hypoxic exposure, or (3) increases in inflammatory markers in patients with OSA may be more related to other factors such as obesity or nocturnal arousal.

A proteomics platform combining depletion, multi-lectin affinity chromatography (M-LAC), and isoelectric focusing to study the breast cancer proteome

The discovery of breast cancer associated plasma/serum biomarkers is important for early diagnosis, disease mechanism elucidation, and determination of treatment strategy for the disease. In this study of serum samples, a multidimensional fractionation platform combined with mass spectrometric analysis were used to achieve the identification of medium to lower abundance proteins, as well as to simultaneously detect glycan and abundance changes. Immuno-affinity depletion and multi-lectin chromatography (M-LAC) were integrated into an automated HPLC platform to remove high abundance protein and fractionate glycoproteins. The collected glycoproteomes were then subjected to isoelectric focusing (IEF) separation by a digital ProteomeChip (dPC), followed by in-gel digestion and LC-MS analysis using an Orbitrap mass spectrometer. As a result, the total number of identified proteins increased significantly when the IEF fractionation step was included as part of the platform. Relevant proteins with biological and disease significance were observed and the dynamic range of the serum proteome measurement was extended. In addition, potential glycan changes were indicated by comparing proteins in control and cancer samples in terms of their affinity to the multi-lectin column (M-LAC) and the pI profiles in IEF separation. In conclusion, a proteomics platform including high abundance protein depletion, lectin affinity fractionation, IEF separation, and LC-MS analysis has been applied to discover breast cancer-associated proteins. The following candidates, thrombospondin-1 and 5, alpha-1B-glycoprotein, serum amyloid P-component, and tenascin-X, were selected as promising examples of the use of this platform. They show potential abundance and glycan changes and will be further investigated in future studies.

Endothelial mechanisms of endothelial dysfunction in patients with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) occurs in 2% of middle-aged women and 4% of middle-aged men in the general population and the prevalence is much higher in specific patient groups. Intermittent hypoxia (IH, oxygen desaturation and re-oxygenation) cycle, a major pathophysiologic character of OSA, and the physiological responses this evokes are thought to be responsible for its association with increased cardiovascular morbidity and mortality. Endothelial dysfunction, resulting from IH and as a key early event in atherosclerosis, was demonstrated repeatedly in patients with OSA and in animal models of IH, providing an important mechanistic link between the acute cyclical IH during sleep and the increased prevalence of chronic vascular diseases.

CONCLUSIONS

From this work, we conclude that IH from OSA may result in endothelial dysfunction, as a potential promoter of atherosclerosis, through nitric oxide unavailability, oxidative stress and inflammation, cell apoptosis, the crosstalk between endothelial cells and circulating inflammatory cells, microparticles, and damage repairing process. Though effective continuous positive airway pressure (CPAP) may specifically improve endothelial function, more controlled larger interventional trials that will include multiple centers and randomized allocation of CPAP therapy are needed to see if such changes are reversible before cause and effect can be implied finally, while further studies on cellular and animal level are also needed to elucidate molecular biologic/pathologic pathways.

Relationship between sleep-disordered breathing and iris and/or angle neovascularization in proliferative diabetic retinopathy cases

PURPOSE

To investigate whether sleep-disordered breathing is a risk factor for iris and/or angle neovascularization in patients with proliferative diabetic retinopathy (PDR).

DESIGN

Cross-sectional comparative case series.

SUBJECTS AND METHODS

One hundred fifty-one consecutive patients with PDR who underwent surgery in our hospital were divided based on the presence of iris and/or angle neovascularization (NV group, 37 patients) or absence of NV (non-NV group, 114 patients). Pulse oximetry was conducted during the night and the mean SpO(2), 4% oxygen desaturation index (4% ODI times/hour), the lowest SpO(2)% during sleep (lowest SpO(2)), and the cumulative percentage of time at SpO(2) <90% in analysis times (CT90%) were calculated. When the 4% ODI exceeded 5 times/hour, sleep-disordered breathing was diagnosed. The results were compared between the 2 groups. Preoperative systemic parameters also were analyzed by logistic regression to clarify risk factors for the NV group.

RESULTS

A mean total of 50% (62% of the NV group and 46% of the non-NV group) was diagnosed with sleep-disordered breathing. The mean SpO(2) and lowest SpO(2) did not differ significantly between the 2 groups; the 4% ODI (12.3 vs 6.6) and CT90% (3.8 vs 1.7) were significantly higher in the NV group (P=.02, for both comparisons). Logistic regression analysis identified insulin therapy (odds ratio [OR], 3.01; 95% confidence interval [CI], 1.26∼7.20; P=.01); and 4% ODI (OR, 1.09; CI, 1.01∼1.16; P=.02) as risk factors for the NV group.

CONCLUSIONS

In patients with PDR, nocturnal intermittent hypoxia/reoxygenation resulting from sleep-disordered breathing may be a risk factor for iris and/or angle neovascularization.

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 and inflammation: relationship to cardiovascular co-morbidity

Obstructive sleep apnoea syndrome (OSAS) is a highly prevalent disease and associated with cardiovascular morbidity and mortality. The pathogenesis of cardiovascular complications in OSAS is incompletely understood but a multifactorial etiology is likely. There is emerging evidence that inflammatory processes leading to endothelial dysfunction play a pivotal role. Various studies have demonstrated elevated inflammatory markers in OSAS patients in comparison to matched control subjects with a significant fall after effective treatment with continuous positive airway pressure. Cell culture and animal studies have significantly enhanced our understanding of the mechanisms of inflammation in OSAS. Intermittent hypoxia, the hallmark feature of OSAS, leads to a preferential activation of inflammatory pathways with the downstream consequence of expression of pro-inflammatory cytokines, chemokines and adhesion molecules that may contribute to endothelial dysfunction. Further studies are required to determine the precise role of inflammation in the cardiovascular pathogenesis of OSAS, particularly its interaction with oxidative stress, obesity and metabolic dysfunction.

Non-invasive study of airways inflammation in sleep apnea patients

The current view foresees that airway inflammation and oxidative stress are both important in the pathophysiology of obstructive sleep apnea syndrome (OSAS). Notwithstanding the fact that these events play a key role in OSAS, their monitoring is not included in the current management of this disease. The direct sampling of airways is made possible today thanks to what can be defined as quite invasive techniques, such as bronchoscopy with broncho-lavage and biopsy. Recently there has been increasing interest in the non-invasive methods that allow the study of airways via the induced sputum (IS), the exhaled breath volatile mediators and the exhaled breath condensate (EBC). The non-invasiveness of these techniques makes them suitable for the evaluation and serial monitoring of OSAS patients. The aim of this review is to spread current knowledge on the non-invasive airway markers and on their potential clinical applications in OSAS.

Pharyngeal lavage lymphocytosis in patients with obstructive sleep apnea: a preliminary observation

Background

Upper airway inflammation has been previously demonstrated in obstructive sleep apnea (OSA). However, investigation has been hampered by the necessity of invasive tissue biopsies.

Objective

To evaluate the pharyngeal lavage (PHAL) as a new tool to analyze mucosal inflammation in the pharynx of patients with sleep-related disordered breathing.

Patients and Methods

36 patients with a diagnosis of OSA, 14 patients with heavy snorer syndrome (HS) or body position dependent OSA (bd-OSA), and 14 healthy volunteers underwent PHAL. Inflammatory cell counts were compared.

Results

Neutrophils were the predominant cells in PHAL in all groups (94.3%±0.7%, 98.5%±0.6%, 94.3%±0.7%, and 96.2%±1.4%). OSA patients had significantly increased numbers of lymphocytes (3.2%±0.4%) compared to bd-OSA/HS and controls group (0.5%±0.1% and 0.6%±0.2%, respectively; P<0.05). Patients with moderate to severe OSA had significantly higher numbers of lymphocytes compared to patients with mild OSA (P<0.05).

Conclusions

Data from this study suggest that PHAL is a feasible tool to investigate upper airway inflammation in OSA. In addition, PHAL demonstrates lymphocytic inflammation of the pharynx in OSA patients. Future studies are warranted to evaluate whether PHAL can be used to monitor disease and whether lymphocytic inflammation is affected by OSA treatment.

Pathogenic mechanisms in varicose vein disease: the role of hypoxia and inflammation

AIMS

Although the aetiology of varicose veins remains unknown, recent studies have focused on endothelial cell integrity and function. Among the regulatory factors of vessel tone, synthesises, pro- and anti-inflammatory, adhesion molecules and the transcription factor hypoxia inducible factor-1 alpha (HIF-1alpha), which are responsible for recruiting leukocytes, are very important.

METHODS

Investigation in this study focused on the expression of ICAM-1, E-selectin and HIF-1alpha on endothelial cells using immunostaining and RT-PCR in varicose vein specimens compared with controls.

RESULTS

Findings of this study showed alterations of the intima, such as focal intimal discontinuity and denudation of endothelium in varicose veins. Based on data derived from immunostaining and RT-PCR, no major differences were identified between ICAM-1 and E-selectin expression in varicose vein specimens compared with controls. In contrast, immunostaining results identified HIF-1alpha expression in five (5/20) varicose vein specimens, whereas no control saphenous vein specimens expressed HIF-1alpha.

CONCLUSIONS

These findings could explain other evidence of hypoxia in varicose veins. Finally, results already obtained in this investigation suggest that the process of pathogenesis of varicose veins is not restricted to the role of adhesion molecules.

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.

Cardiovascular consequences of sleep apnea

Cardiovascular disease has been the leading cause of death since 1900. Strategies for cardiovascular disease and prevention have helped to reduce the burden of disease, but it remains an important public health challenge. Therefore, understanding the underlying pathophysiology and developing novel therapeutic approaches for cardiovascular disease is of crucial importance. Recognizing the link between sleep and cardiovascular disease may represent one such novel approach. Obstructive sleep apnea (OSA), a common form of sleep-disordered breathing, has a high and rising prevalence in the general adult population, attributable in part to the emerging epidemic of obesity and enhanced awareness. OSA has been independently linked to specific cardiovascular outcomes such as hypertension, stroke, myocardial ischemia, arrhythmias, fatal and nonfatal cardiovascular events, and all-cause mortality. Treatment of OSA may represent a novel target to reduce cardiovascular health outcomes.

Snoring and the risk of obstructive sleep apnea in patients with pulmonary embolism

BACKGROUND

Obstructive sleep apnea (OSA) is associated with prothrombotic effects that could lead to venous thromboembolic disease. We performed a prospective cross-sectional study to determine the prevalence of snoring and risk of OSA in patients with acute pulmonary embolism (PE).

METHODS

We evaluated 270 consecutive patients who underwent a computed tomographic angiogram for suspected PE. Patients without PE served as a control group. Demographic and clinical characteristics were analyzed. The Berlin Questionnaire was used to determine the presence of snoring and the risk of OSA. A subset of patients also underwent formal nocturnal polysomnography.

RESULTS

PE was present in 71 (26%) of the 270 patients who underwent a computed tomographic angiogram. When compared with patients without PE, patients with PE had a significantly higher prevalence of snoring (75% vs 50%, odds ratio = 2.91, 95% confidence interval: 1.60, 5.33, P = 0.001) and an increased risk of having OSA, as defined by the Berlin Questionnaire (65% vs 36%, odds ratio = 3.25, confidence interval: 1.84, 5.72, P < 0.001). Results from the multivariate analysis showed that PE was independently associated with risk of OSA (OR = 2.78, P = 0.001).

CONCLUSIONS

We found a higher prevalence of snoring and high risk of OSA in patients diagnosed with acute PE, in comparison with patients in whom PE was suspected but ruled out. This association might be independent of other risks factors common to both OSA and PE. Therefore, OSA may represent a risk factor for the development of PE.

Increased circulating endothelial microparticles and carotid atherosclerosis in obstructive sleep apnea

Background and Purpose

Endothelial impairment is a linking mechanism between obstructive sleep apnea (OSA) and cardiovascular diseases. Profiles of endothelial microparticles (EMPs) and endothelial progenitor cells (EPCs) reflect the degree of endothelial impairment. The aims of this study were to measure the levels of EMPs and progenitor cells in OSA, determine the correlations between these factors and OSA severity and the degree of atherosclerosis, and document any changes in these factors after therapy.

Methods

Subjects with (n=82) and without (n=22) OSA were recruited prospectively. We measured the number of colony-forming units (CFU) in cell culture as the endothelial progenitor cell index, and the number of EMPs using flow cytometry with CD31 [platelet endothelial cell adhesion molecule (PECAM)], CD42 (platelet glycoprotein), annexin V, and CD62E (E-selectin) antibodies at baseline and after 4-6 weeks of continuous positive airway pressure (CPAP) therapy. Carotid intima-media thickness (IMT) was regarded as a marker of atherosclerosis.

Results

The levels of PECAM⁺CD42^- (p<0.001), PECAM⁺annexin V⁺ (p<0.001), and E-selectin⁺ microparticles (p=0.001) were higher in OSA subjects than in non-OSA subjects. The number of CFU did not differ between the two groups. OSA severity independently predicted the levels of PECAM⁺CD42^- (p=0.02) and PECAM⁺annexin V⁺ (p=0.004). Carotid IMT was correlated with OSA severity (p<0.001), PECAM⁺CD42^- (p=0.03), and PECAM⁺annexin V⁺ (p=0.01). Neither OSA severity nor carotid IMT was correlated with either the number of CFU or E-selectin⁺. CPAP therapy decreased the occurrence of E-selectin⁺ (p<0.001) in 21 of the OSA subjects, but had no effect on the other microparticles of the number of CFU.

Conclusions

OSA led to the overproduction of EMPs, which moderately correlated with OSA severity and the degree of atherosclerosis, and partly responded to therapy. The endothelial impairment might contribute to future cardiovascular events.

Endothelial dysfunction and circulating microparticles from patients with obstructive sleep apnea

Endothelial dysfunction is involved in vascular complications of obstructive sleep apnea (OSA). In this study, circulating microparticles (MPs) from patients with OSA-induced nocturnal desaturations were characterized and their effects on endothelial function were evaluated. Two age-matched groups of patients undergoing polysomnography for OSA were compared: 35 desaturators with a 3% oxyhemoglobin desaturation index (ODI) > or = 10 events per hour of sleep and 27 nondesaturators with ODI <10 events per hour. MPs were characterized by flow cytometry and then either used to treat in vitro human endothelial cells or to study endothelial function in mice. Circulating MPs did not differ between groups, but MPs from granulocytes and activated leukocytes (CD62L(+)) were found at higher levels in desaturators. In vitro, MPs from desaturators reduced endothelial nitric oxide (NO) production by enhancing phosphorylation of endothelial NO synthase at the site of inhibition and expression of caveolin-1. CD62L(+) MPs positively correlated with ODI. Endothelial NO production negatively correlated with both CD62L(+) MPs and ODI. MPs from desaturators increased expression of endothelial adhesion molecules including E-selectin, ICAM-1 and ITGA5, and cyclooxygenase 2. Moreover, injection of MPs from desaturators into mice impaired endothelium-dependent relaxation in aorta and flow-induced dilation in small mesenteric arteries. This study demonstrates an association between endothelial dysfunction and increased circulating levels of CD62L(+) MPs. This may initiate atherogenic processes in patients with OSA and severe nighttime hypoxia.

Nocturnal intermittent serious hypoxia and reoxygenation in proliferative diabetic retinopathy cases

PURPOSE

To clarify the relationship between evaluation items of sleep-disordered breathing and diabetic retinopathy in detail.

DESIGN

Cross-sectional comparative study.

METHODS

Sixty-eight consecutive nonproliferative diabetic retinopathy and 151 proliferative diabetic retinopathy (PDR) cases who had undergone surgeries in our department were included in this study. Pulse oximetry was conducted overnight and mean oxygen saturation by pulse oximeter (SpO(2); %), the sleeping 4% oxygen desaturation index (4% ODI times/hour), lowest SpO(2) (%), and the cumulative percent time spent at SpO(2) < 90% (CT 90%) were calculated. The results were evaluated and compared between the 2 groups. In addition, these results and preoperative patient background factors were analyzed using logistic regression analysis to clarify risk factor of PDR.

RESULTS

4% ODI and CT 90% in the PDR group were significantly higher than in the nonproliferative diabetic retinopathy group (4% ODI, 7.8 vs. 4.9; P = .007; CT 90%, 2.2 vs 0.8; P = .0006). Lowest SpO(2) was significantly lower in the PDR group than in the nonproliferative diabetic retinopathy groups (82.4 vs 87.0; P = .0006). Logistic regression analysis identified being younger, having a lower value for the lowest SpO(2), and a high hemoglobin A1c value to be risk factors for PDR (age: odds ratio, 0.90; 95% confidence interval, -0.86 to -0.94; P < .0001; lowest SpO(2): odds ratio, 0.93; 95% confidence interval, 0.88 to 0.99; P = .02; hemoglobin A1c: odds ratio, 1.00 to 1.69; P = .047).

CONCLUSIONS

This study indicated that PDR cases had episodes of nocturnal intermittent hypoxia and reoxygenation as a result of sleep-disordered breathing and that low-value lowest SpO(2) were the risk factors for PDR development.

Systemic and airway inflammation in sleep apnea and obesity: the role of ICAM-1 and IL-8

The recurrent hypoxic stress that characterizes obstructive sleep apnea (OSA) seems to play a role in the increased adherence of neutrophils to endothelial cells as well as in the resulting migration of the former to the inflamed area. Intercellular adhesion molecule 1 (ICAM-1) and interleukin (IL)-8 are markers widely used in OSA studies to investigate inflammation. The aim of this study was to measure ICAM-1 and IL-8 levels in the breath condensate and in the plasma and inflammatory cells in the induced sputum of 12 obese OSA (OO) patients, 10 nonobese OSA (NOO) patients, 10 obese non-OSA (ONO) subjects, and 8 healthy subjects (HS) using a specific enzyme immunoassay (EIA) kit. A significant increase in both plasma and exhaled IL-8 and ICAM concentrations and percentage neutrophils was observed in the induced sputum of obese OSA patients, non-obese OSA patients, and obese non-OSA subjects compared with healthy subjects. However, although these inflammatory markers were found to follow an upward trend in obese OSA patients no difference was observed in both either non-obese OSA patients and obese non-OSA subjects. Finally, a significant positive correlation was found to occur among IL-8, ICAM-1, and sputum neutrophils, as well as across the apnea-hypopnoea index (AHI), TST 90%, body mass index (BMI), and neck circumference. The data obtained confirm the occurrence of an ICAM- and IL-8-mediated neutrophilic airway inflammation in both OSA and obese patients. The degree of inflammation, which seems to worsen in cases of comorbidity (OSA and obesity), is likely to be responsible for the increased risk of developing cardiovascular events observed in these subjects, and therefore, it deserves to be elucidated even more.

Hypertension in obstructive sleep apnea: risk and therapy

Obstructive sleep apnea (OSA) is a common form of sleep-disordered breathing that occurs due to recurrent collapse of the upper airway with inspiration. Large epidemiologic studies have established that OSA is a risk factor for developing hypertension. The pathophysiologic mechanism of this relationship is due to the distinctive pattern of intermittent hypoxia seen in OSA. This pattern increases sympathetic tone, oxidative stress, inflammation and endothelial dysfunction. These processes can all lead to persistent elevation of blood pressure beyond the obstructive events. OSA should be considered as part of the workup of patients with hypertension. Treatment of OSA with continuous positive airway pressure has an effect on hypertension control and risk reduction of cardiovascular diseases. This review discusses the pathophysiology and causal relationship between OSA and hypertension, along with the cardiovascular effects of treatment of OSA.

Increase in serum haptoglobin and apolipoprotein M in patients with obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is a common syndrome, which is associated with a number of medical problems that impact morbidity and mortality. Although the precise mechanisms that underlie these associations are not fully understood, previous studies have suggested that patients with OSA show elevations of several biomarkers that are associated with cardiovascular risk. This study was undertaken to identify serum proteins associated with OSA by using a proteomics technique and to examine changes in identified protein levels after continuous positive airway pressure treatment. The study participants consisted of 40 male patients (aged 40-49 years) with severe OSA and 34 male control subjects matched for age and body mass index. All subjects underwent polysomnography. Using a proteomics approach, we identified nine proteins that were differentially expressed in patients with severe OSA and controls. Three of these nine proteins, haptoglobin, paraoxonase-1 and apolipoprotein M, were quantified by using enzyme-linked immunosorbent assays, kinetic assays and by using Western blotting. Multiple regression analysis showed that haptoglobin and apolipoprotein M levels are independently related to apnoea-hypopnoea index (P < 0.01). A further study is required to determine the nature of associations between these identified proteins and OSA in a large population.

Obstructive sleep apnea and cardiovascular disease

Obstructive sleep apnea (OSA) is a common yet an under-diagnosed sleep related breathing disorder affecting predominantly middle-aged men. OSA is associated with many adverse health outcomes, including cardiovascular disease. Common OSA associated/induced cardiovascular disorders include coronary artery disease, heart failure, hypertension, cardiac arrhythmias and stroke, which further increase morbidity and mortality in the OSA population. Endothelial dysfunction, coagulopathy, impaired sympathetic drive, oxidative and inflammatory stress are the pathophysiological pathways suggested for the development of cardiovascular disease in OSA. The evidence would suggest that OSA should be considered as a cardiovascular risk factor, and is a treatable condition. Multiple studies using Continuous Positive Airway Pressure (CPAP) have shown improvements in the clinical state as well as retardation of disease progression. Therefore, patients with cardiovascular disease should be proactively screened for OSA and vice versa.

Relationship between diabetic retinopathy and sleep-disordered breathing

PURPOSE

To clarify the relationships of sleep-disordered breathing (SDB) to nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR).

DESIGN

Cross sectional case-control study.

METHODS

Forty-eight consecutive NPDR and 118 PDR cases that had undergone surgery in our hospital were included in this study. Pulse oximetry was conducted during the night and the sleeping 4% oxygen desaturation index (ODI) (number of oxygen desaturation events/hour exceeding 4%) and mean SpO(2)% were calculated. If 4% ODI > 5 times/hour, SDB was diagnosed. The results were evaluated and compared between the 2 groups. In addition, these results and preoperative patient background factors were analyzed using multiple regression analysis to identify correlations with the diagnosis of PDR.

RESULTS

Twenty-nine percent of the NPDR and 48% of the PDR patients were diagnosed as having SDB. The incidence of SDB and the 4% ODI/hour value were significantly higher in the PDR than in the NPDR group (P = .003 and .03, respectively). Multiple regression analysis showed younger age and a higher 4% ODI value to be factors independently contributing to a diagnosis of PDR (age, standard regression coefficient = -0.34; t value = -4.44; P < .0001; 4% ODI, standard regression coefficient = 0.20; t value = 2.15; P = .03, correlation coefficient (R) = 0.43).

CONCLUSION

Our results suggest that, in diabetic retinopathy patients with nocturnal desaturation, reoxygenation caused by SDB may relate to the development of PDR.

Obstructive sleep apnea, immuno-inflammation, and atherosclerosis

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder leading to cardiovascular and metabolic complications. OSA is also a multicomponent disorder, with intermittent hypoxia (IH) as the main trigger for the associated cardiovascular and metabolic alterations. Indeed, recurrent pharyngeal collapses during sleep lead to repetitive sequences of hypoxia-reoxygenation. This IH induces several consequences such as hemodynamic, hormonometabolic, oxidative, and immuno-inflammatory alterations that may interact and aggravate each other, resulting in artery changes, from adaptive to degenerative atherosclerotic remodeling. Atherosclerosis has been found in OSA patients free of other cardiovascular risk factors and is related to the severity of nocturnal hypoxia. Early stages of artery alteration, including functional and structural changes, have been evidenced in both OSA patients and rodents experimentally exposed to IH. Impaired vasoreactivity with endothelial dysfunction and/or increased vasoconstrictive responses due to sympathetic, endothelin, and renin-angiotensin systems have been reported and also contribute to vascular remodeling and inflammation. Oxidative stress, inflammation, and vascular remodeling can be directly triggered by IH, further aggravated by the OSA-associated hormonometabolic alterations, such as insulin resistance, dyslipidemia, and adipokine imbalance. As shown in OSA patients and in the animal model, genetic susceptibility, comorbidities (obesity), and life habits (high fat diet) may aggravate atherosclerosis development or progression. The intimate molecular mechanisms are still largely unknown, and their understanding may contribute to delineate new targets for prevention strategies and/or development of new treatment of OSA-related atherosclerosis, especially in patients at risk for cardiovascular disease.

Mechanisms of endothelial dysfunction in obstructive sleep apnea

Endothelial activation and inflammation are important mediators of accelerated atherogenesis and consequent increased cardiovascular morbidity in obstructive sleep apnea (OSA). Repetitive episodes of hypoxia/reoxygenation associated with transient cessation of breathing during sleep in OSA resemble ischemia/reperfusion injury and may be the main culprit underlying endothelial dysfunction in OSA. Additional factors such as repetitive arousals resulting in sleep fragmentation and deprivation and individual genetic suseptibility to vascular manifestations of OSA contribute to impaired endothelial function in OSA. The present review focuses on possible mechanisms that underlie endothelial activation and inflammation in OSA.

Association of chronic obstructive pulmonary disease and obstructive sleep apnea consequences

Obstructive sleep apnea syndrome (OSAS) and chronic obstructive pulmonary disease (COPD) are two diseases that often coexist within an individual. This coexistence is known as overlap syndrome and is the result of chance rather than a pathophysiological link. Although there are claims of a very high incidence of OSAS in COPD patients, recent studies report that it is similar to the general population. Overlap patients present sleep-disordered breathing associated to upper and lower airway obstruction and a reduction in respiratory drive. These patients present unique characteristics, which set them apart from either COPD or OSAS patients. COPD and OSAS are independent risk factors for cardiovascular events and their coexistence in overlap syndrome probably increases this risk. The mechanisms underlying cardiovascular risk are still unclear, but may involve systemic inflammation, endothelial dysfunction, and tonic elevation of sympathetic neural activity. The treatment of choice for overlap syndrome in stable patients is CPAP with supplemental oxygen for correction of upper airway obstructive episodes and hypoxemia during sleep.

Obstructive sleep apnea and atherosclerosis

Obstructive sleep apnea (OSA) is associated with significant cardiovascular morbidity and excess in mortality. Atherosclerosis has been shown to occur in OSA patients free of any other significant risk factors. In particular, intima media thickness, an early marker of atherosclerosis, may be increased at the carotid level in OSA. Thus, early atherosclerosis could be one of the intermediary mechanisms supporting the link between OSA and cardiovascular morbidity. The current concept is that the development of atherosclerotic lesions results from a dynamic interplay between the native cells of the vasculature and different proinflammatory leukocytes issued from the general circulation. Immunoinflammatory cells dominate early atherosclerotic processes, with the secretion of several proinflammatory molecules aggravating lesion progression. There is now substantial evidence that intermittent hypoxia in rodents, as a partial model of sleep apnea, triggers atherogenesis. Blood pressure alterations and hemodynamic strains on the vascular wall, impairment in vascular reactivity, lipid metabolism dysregulation, and activation of proinflammatory transcription factors at the vascular wall level are among the key factors promoting atherosclerosis. Specifically, increases in leukocyte rolling and adhesion molecule expression at the endothelial cell level have been shown to occur in the first 2 weeks after intermittent hypoxia exposure initiation. Early changes at the vascular wall level have been shown in OSA patients and its reversibility under continuous positive airway pressure has also been suggested. Several biological markers potentially linked with early atherosclerosis development are under study in OSA patients. Further studies are needed to identify at-risk subjects prone to develop vascular changes because OSA treatment may either be initiated earlier or combined with specific drug treatments.

Obstructive sleep apnea and inflammation

The pathogenesis of cardiovascular complications in obstructive sleep apnea syndrome (OSAS) is not fully understood but is likely multifactorial in origin. Inflammatory processes play an important role in the pathogenesis of atherosclerosis, and circulating levels of several markers of inflammation have been associated with future cardiovascular risk. These include cell adhesion molecules such as intercellular adhesion molecule-1 and selectins, cytokines such as tumour necrosis factor alpha and interleukin 6, chemokines such as interleukin 8, and C-reactive protein. There is also increasing evidence that inflammatory processes play an important role in the cardiovascular pathophysiology of OSAS and many of the inflammatory markers associated with cardiovascular risk have been reported as elevated in patients with OSAS. Furthermore, animal and cell culture studies have demonstrated preferential activation of inflammatory pathways by intermittent hypoxia, which is an integral feature of OSAS. The precise role of inflammation in the development of cardiovascular disease in OSAS requires further study, particularly the relationship with oxidative stress, metabolic dysfunction, and obesity.

Endothelial function in obstructive sleep apnea

Untreated obstructive sleep apnea (OSA) is an independent risk factor for hypertension, myocardial infarction, and stroke. The repetitive hypoxia/reoxygenation and sleep fragmentation associated with OSA impair endothelial function. Endothelial dysfunction, in turn, may mediate increased risk for cardiovascular diseases. Specifically, in OSA, endothelial nitric oxide availability and repair capacity are reduced, whereas oxidative stress and inflammation are enhanced. Treatment of OSA improves endothelial vasomotor tone and reduces inflammation. We review the evidence and possible mechanisms of endothelial dysfunction as well as the effect of treatment on endothelial function in OSA.

Metabolic consequences of sleep-disordered breathing

There is increasing evidence of a causal relationship between sleep-disordered breathing and metabolic dysfunction. Metabolic syndrome (MetS), a cluster of risk factors that promote atherosclerotic cardiovascular disease, comprises central obesity, insulin resistance, glucose intolerance, dyslipidemia, and hypertension, manifestations of altered total body energy regulation. Excess caloric intake is indisputably the key driver of MetS, but other environmental and genetic factors likely play a role; in particular, obstructive sleep apnea (OSA), characterized by intermittent hypoxia (IH), may induce or exacerbate various aspects of MetS. Clinical studies show that OSA can affect glucose metabolism, cholesterol, inflammatory markers, and nonalcoholic fatty liver disease. Animal models of OSA enable scientists to circumvent confounders such as obesity in clinical studies. In the most widely used model, which involves exposing rodents to IH during their sleep phase, the IH alters circadian glucose homeostasis, impairs muscle carbohydrate uptake, induces hyperlipidemia, and upregulates cholesterol synthesis enzymes. Complicating factors such as obesity or a high-fat diet lead to progressive insulin resistance and liver inflammation, respectively. Mechanisms for these effects are not yet fully understood, but are likely related to energy-conserving adaptations to hypoxia, which is a strong catabolic stressor. Finally, IH may contribute to the morbidity of MetS by inducing inflammation and oxidative stress. Identification of OSA as a potential causative factor in MetS would have immense clinical impact and could improve the management and understanding of both disorders.

Predictors of habitual snoring and obstructive sleep apnea risk in patients with asthma

BACKGROUND

A high prevalence of obstructive sleep apnea (OSA) symptoms was reported in patients with asthma. Our goal was to evaluate factors associated with habitual snoring and OSA risk in these patients.

METHODS

Patients with asthma were surveyed at specialty clinics with the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ) and questions about the frequency of asthma symptoms (National Asthma Education and Prevention Program guidelines), followed by medical record review. SA-SDQ scores >or= 36 for men and >or= 32 for women defined high OSA risk. Logistic regression was used to model associations with habitual snoring and high OSA risk.

RESULTS

Among 244 patients, 37% snored habitually and 40% demonstrated high OSA risk. Independent predictors of habitual snoring included gastroesophageal reflux disease (GERD) [odds ratio (OR), 2.19; 95% confidence interval (CI), 1.19 to 4.02] and use of an inhaled corticosteroid (ICS) [OR, 2.66; 95% CI, 1.05 to 6.72]. High OSA risk was predicted by asthma severity step (OR, 1.59; 95% CI, 1.23 to 2.06), GERD (OR, 2.70; 95% CI, 1.51 to 4.83), and ICS use (OR, 4.05; 95% CI, 1.56 to 10.53). Linear, dose-dependent relationships of ICS with habitual snoring and high OSA risk were seen (p = 0.004 and p = 0.0006, respectively). Women demonstrated a 2.11 times greater odds for high OSA risk (95% CI, 1.10 to 4.09) when controlling for the above covariates.

CONCLUSIONS

Symptoms of OSA in patients with asthma are predicted by asthma severity, coexistent GERD, and use of an ICS in a dose-dependent fashion. The well-recognized male gender predominance for OSA symptoms is not apparent in these patients. Further exploration of these relationships may help to explain the increased prevalence of OSA in asthma and provide new insights into the reported female predominance of asthma morbidity.

Obstructive sleep apnea syndrome is a systemic disease. Current evidence

Obstructive sleep apnea syndrome (OSAS) is a highly prevalent sleep disorder, characterized by repeated disruptions of breathing during sleep. This disease has many potential consequences including excessive daytime sleepiness, neurocognitive deterioration, endocrinologic and metabolic effects, and decreased quality of life. Metabolic syndrome is another highly prevalence emerging public health problem that represents a constellation of cardiovascular risk factors. Each single component of the cluster increases the cardiovascular risk, but the combination of factors is much more significant. It has been suggested that the presence of OSAS may increase the risk of developing some metabolic syndrome features. Moreover, OSAS patients are at an increased risk for vascular events, which represent the greatest morbidity and mortality of all associated complications. Although the etiology of OSAS is uncertain, intense local and systemic inflammation is present. A variety of phenomena are implicated in this disease such as modifications in the autonomic nervous system, hypoxemia-reoxygenation cycles, inflammation, and coagulation-fibrinolysis imbalance. OSAS patients also present increased levels of certain biomarkers linked to endocrine-metabolic and cardiovascular alterations among other systemic consequences. All of this indicates that, more than a local abnormality, OSAS should be considered a systemic disease.

Biology of peripheral blood cells in obstructive sleep apnea--the tip of the iceberg

Obstructive sleep apnea (OSA), a highly prevalent breathing disorder in sleep, characterized by intermittent and recurrent pauses in respiration, has emerged as an independent risk factor for cardiovascular morbidity and mortality. Accumulated evidence implicates Leukocyte-endothelial cell activation and adhesion as critical components that induce inflammation and injury to the vasculature resulting in the development of cardiovascular complications. Similar cellular interactions were described in conditions of ischemia/reperfusion, and various components of the metabolic syndrome as hypercholesterolemia and hypertension. The hallmark of sleep apnea--the multiple cycles of hypoxia/reoxygenation--promote oxidative stress and inflammation. These facilitate increased interactions of blood cells with endothelial cells, resulting in endothelial cell injury and dysfunction. Such events can promote atherosclerosis and the development of cardiovascular morbidities in OSA. However, inter-individual differences in response to intermittent hypoxia and activation of anti-inflammatory cytokine profiles in T lymphocytes can serve as protective mechanisms.

Aortic pressure augmentation as a marker of cardiovascular risk in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is associated with increases in cardiovascular morbidity and mortality. Vascular changes in individuals with OSAS have not been fully elucidated, however. The possible impact of OSAS on the extent of aortic pressure augmentation (AG), an indicator of cardiovascular risk, was investigated. Forty-five consecutive male patients aged 35 to 78 years (56.0+/-9.6 years) who were referred to the sleep clinic of Nagoya University Hospital for screening and treatment of OSAS and 71 age-matched healthy men were enrolled in the study. AG was derived from the pressure waveform measured at the radial artery by applanation tonometry. The number of apnea and hypopnea episodes per hour (apnea-hypopnea index [AHI]) was determined by standard polysomnography. AG was significantly greater in OSAS patients than in controls (9.0+/-4.1 vs. 6.4+/-3.4 mmHg, p<0.001), and it was significantly reduced in 19 OSAS patients treated with continuous positive airway pressure. AG was also significantly correlated with the AHI (r=0.562, p<0.001) and age (r=0.356, p=0.016) but not with the serum concentrations of low and high density lipoprotein-cholesterol, triglyceride, or glycosylated hemoglobin. Stepwise multiple regression analysis revealed that the AHI was the most significant contributing factor to the increased AG in OSAS patients (beta=0.109, r=0.530, p<0.001). OSAS may thus have an adverse effect on vascular function that can be ameliorated by appropriate treatment.

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.

Nocturnal change of circulating intercellular adhesion molecule 1 levels in children with snoring

Hypoxia promotes adherence of leukocytes to endothelial cells by inducing expression of adhesion molecules like intercellular adhesion molecule 1 (ICAM-1). Increased serum levels of circulating ICAM-1 (cICAM-1) have been reported in adults with sleep apnea and associated hypoxemia. This investigation assessed the hypothesis that the overnight change of cICAM-1 levels in children with snoring is correlated with the severity of obstructive sleep-disordered breathing. Evening and morning serum levels of cICAM-1 were measured in children with snoring referred for polysomnography. Twenty-five children with an apnea-hypopnea index greater than or equal to 5 episodes/h (5.5 +/- 1.8 years), 30 subjects with an index less than 5 and greater than 1 (6.3 +/- 2 years), and 19 children with an index less than or equal to 1 (7.1 +/- 3 years) were recruited. Overnight change in cICAM-1 (log-transformed ratio of morning-to-evening levels) was similar in subjects with an apnea-hypopnea index greater than or equal to 5 episodes/h compared to those with an index less than 5 and greater than 1 or to children with an index less than or equal to 1 (-0.001 +/- 0.08 vs -0.03 +/- 0.09 vs -0.06 +/- 0.1; p > 0.05). When multiple regression analysis was applied, apnea-hypopnea index, respiratory arousal index, and oxygen saturation of hemoglobin nadir were not significant predictors of overnight change in cICAM-1 levels. Thus, in children with snoring, overnight change in cICAM-1 levels is not related to severity of obstructive sleep-disordered breathing.

Effect of nasal continuous positive airway pressure treatment on plasma adrenomedullin levels in patients with obstructive sleep apnea syndrome: roles of nocturnal hypoxia and oxidant stress

Obstructive sleep apnea syndrome (OSAS) is recognized as one of the risk factors of hypertension and cardiovascular disorders. In the current study, we hypothesized that the hypoxic stress and oxidative stress caused by obstructive sleep apnea would increase circulating adrenomedullin (ADM) levels in untreated OSAS patients as compared to an age and body mass index (BMI)-matched control group and an age-matched, but normal-BMI control group. We further hypothesized that nasal continuous positive airway pressure (nCPAP) treatment may decrease OSAS-induced hypoxic stress, oxidative stress and ADM levels. To examine these hypotheses, we measured circulating ADM and reactive oxygen species (ROS) from leukocytes before and after nCPAP therapy in OSAS patients. The circulating levels of ADM and amount of ROS in untreated OSAS patients were significantly greater than those in the controls. No differences in ADM levels were found between the increased-BMI controls and normal-BMI controls. We observed that nCPAP treatment decreased sleep apneas, nocturnal oxyhemoglobin desaturation, the circulating ADM, and ROS production by leukocytes in OSAS patients. The ADM levels were associated with the magnitude of oxyhemoglobin desaturation rather than the number of sleep apneas. These observations suggest that nCPAP therapy could reduce OSAS-induced nocturnal hypoxemia, generation of ROS, and ADM in patients with OSAS.