Association of sleep apnea severity and obesity with insulin resistance, C-reactive protein, and leptin levels in male patients with obstructive sleep apnea

Analysis of Multimorbidity of Moderate to Severe Allergic Rhinitis in Children: A Real-World Study

INTRODUCTION

Allergic rhinitis (AR) in children is associated with various comorbidities, posing challenges for treatment and management. There have been few investigations of these multimorbidities in Chinese children with AR. Here, we investigated the prevalence of multimorbidities in children with moderate to severe AR and analyzed the influencing factors using real-world data.

METHODS

In total, 600 children who visited the outpatient clinic of our hospital and were diagnosed with moderate-severe AR were prospectively enrolled. All children underwent allergen detection and electronic nasopharyngoscopy. Parents or guardians completed a questionnaire that included age, sex, mode of delivery, feeding pattern, and familial history of allergy. The multimorbidities investigated included atopic dermatitis (AD), asthma, allergic conjunctivitis (AC), chronic rhinosinusitis (CRS), adenoid hypertrophy (AH), tonsil hypertrophy (TH), recurrent epistaxis, and recurrent respiratory tract infections (RRTIs).

RESULTS

The AR multimorbidities reported in children were as follows: recurrent epistaxis (46.5%), AC (46.3%), AD (40.7%), asthma (22.5%), RRIs (21.3%), CRS (20.5%), AH (19.7%), and TH (12.5%). In univariate logistic regression analysis, age (<6 years), birth mode, familial history of allergy, and single dust mite allergy were associated with AR multimorbidity (p < 0.05). Multivariate logistic regression revealed that a familial history of allergy was an independent risk factor for AC (odds ratio [OR] = 1.539, 95% confidence interval [CI]: 1.104-2.145) and AH (OR = 1.506, 95% CI: 1.000-2.267) (p < 0.05). Age (<6 years) was independently associated with the risk of AD (OR = 1.405, 95% CI: 1.003-1.969) and RRTIs (OR = 1.869, 95% CI: 1.250-2.793) (p < 0.05), cesarean section with AR and CRS risk (OR = 1.678, 95% CI: 1.100-2.561), and single dust mite allergy with asthma (OR = 1.590, 95% CI: 1.040-2.432) and CRS (OR = 1.600, 95% CI: 1.018-2.515) risk (p < 0.05). Further, non-dust mite allergy was independently associated with AR and CRS (OR = 2.056, 95% CI: 1.084-3.899).

CONCLUSION

AR was found to be accompanied by different comorbidities, including both allergic and non-allergic comorbidities, complicating disease treatment. These findings demonstrated that age (<6 years), familial history of allergy, types of allergens, and cesarean section were risk factors for different multimorbidities associated with AR.

Increased Levels of ANGPTL3 and CTRP9 in Patients With Obstructive Sleep Apnea and Their Relation to Insulin Resistance and Lipid Metabolism and Markers of Endothelial Dysfunction

OBJECTIVE

Obstructive sleep apnea (OSA) has a close relation with obesity and perturbation in adipokines and hepatokines, which are linked to OSA consequences such as insulin resistance, dyslipidemia, and endothelial dysfunction. This study aimed to assess the relation of C1q/TNF-related protein 9 (CTRP9) and angiopoietin-like protein 3 (ANGPTL3) with OSA and biochemical measurements.

METHODS

Serum levels of ANGPTL3, CTRP9, adiponectin, leptin, intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion protein 1 (VCAM-1) were determined in 74 OSA patients and 27 controls using enzyme-linked immunosorbent assay kits.

RESULTS

Levels of ANGPTL3, CTRP9, leptin, ICAM-1, and VCAM-1 were increased in the patients compared to the controls, whereas adiponectin levels decreased. ANGPTL3 had a positive correlation with total cholesterol, triglyceride, low-density lipoprotein cholesterol, ICAM-1, and VCAM-1 and was inversely correlated with leptin. CTRP9 showed a positive correlation with body mass index, insulin resistance, ICAM-1, and VCAM-1.

CONCLUSION

The results indicated the relation of ANGLTP3 and CTRP9 with OSA and its complications, which suggested a possible role for these factors in the consequences of OSA.

Obstructive Sleep Apnoea and Lipid Metabolism: The Summary of Evidence and Future Perspectives in the Pathophysiology of OSA-Associated Dyslipidaemia

Obstructive sleep apnoea (OSA) is associated with cardiovascular and metabolic comorbidities, including hypertension, dyslipidaemia, insulin resistance and atherosclerosis. Strong evidence suggests that OSA is associated with an altered lipid profile including elevated levels of triglyceride-rich lipoproteins and decreased levels of high-density lipoprotein (HDL). Intermittent hypoxia; sleep fragmentation; and consequential surges in the sympathetic activity, enhanced oxidative stress and systemic inflammation are the postulated mechanisms leading to metabolic alterations in OSA. Although the exact mechanisms of OSA-associated dyslipidaemia have not been fully elucidated, three main points have been found to be impaired: activated lipolysis in the adipose tissue, decreased lipid clearance from the circulation and accelerated de novo lipid synthesis. This is further complicated by the oxidisation of atherogenic lipoproteins, adipose tissue dysfunction, hormonal changes, and the reduced function of HDL particles in OSA. In this comprehensive review, we summarise and critically evaluate the current evidence about the possible mechanisms involved in OSA-associated dyslipidaemia.

Can Weight Loss Improve the Cardiovascular Outcomes of Patients with Obesity and Obstructive Sleep Apnea?

Cardiovascular events are the primary cause of mortality in patients with obstructive sleep apnea and obesity. The rising prevalence of obstructive sleep apnea in recent decades has been linked to increasing rates of obesity. Obstructive sleep apnea has also been linked with many different cardiovascular diseases including coronary artery disease, stroke, heart failure, hypertension, and atrial fibrillation. Obesity is an increasing health concern globally, in part because obesity complications such as hypertension, diabetes, and obstructive sleep apnea increase the risk of cardiovascular diseases. More than 10% weight loss may be required to prevent or reverse obesity complications. Treatment approaches to obesity include nutritional therapy, exercise therapy, pharmacotherapy, and surgical therapies. This review intends to identify the effects of weight loss on cardiovascular outcomes in patients with obesity and obstructive sleep apnea. Despite the strong association between cardiovascular diseases and obstructive sleep apnea, randomized trials have failed to demonstrate that treatment of obstructive sleep apnea reduces cardiovascular events, even in patients with established cardiovascular diseases. Weight loss in patients with obstructive sleep apnea improves HbA1c, systolic blood pressure, HDL cholesterol, and triglycerides, but thus far no changes in cardiovascular events have been shown. The combination of weight loss with continuous positive airway pressure (CPAP) appears more beneficial than either treatment in isolation. Large well-controlled trials in patients with obstructive sleep apnea to assess the effects of different weight reduction programs on cardiovascular disease are still needed.

Anorexigenic Effects of Intermittent Hypoxia on the Gut-Brain Axis in Sleep Apnea Syndrome

Sleep apnea syndrome (SAS) is a breathing disorder characterized by recurrent episodes of upper-airway collapse, resulting in intermittent hypoxia (IH) during sleep. Experimental studies with animals and cellular models have indicated that IH leads to attenuation of glucose-induced insulin secretion from pancreatic β cells and to enhancement of insulin resistance in peripheral tissues and cells, such as the liver (hepatocytes), adipose tissue (adipocytes), and skeletal muscles (myocytes), both of which could lead to obesity. Although obesity is widely recognized as a major factor in SAS, it is controversial whether the development of SAS could contribute directly to obesity, and the effect of IH on the expression of appetite regulatory genes remains elusive. Appetite is regulated appropriately by both the hypothalamus and the gut as a gut-brain axis driven by differential neural and hormonal signals. In this review, we summarized the recent epidemiological findings on the relationship between SAS and feeding behavior and focused on the anorexigenic effects of IH on the gut-brain axis by the IH-induced up-regulation of proopiomelanocortin and cocaine- and amphetamine-regulated transcript in neuronal cells and the IH-induced up-regulation of peptide YY, glucagon-like peptide-1 and neurotensin in enteroendocrine cells and their molecular mechanisms.

Evaluation of Blood Levels of C-Reactive Protein Marker in Obstructive Sleep Apnea: A Systematic Review, Meta-Analysis and Meta-Regression

(1) Introduction: High sensitivity C-reactive protein (hs-CRP) and CRP are inflammatory biomarkers associated with several inflammatory diseases. In both pediatric and adult individuals with Obstructive Sleep Apnea (OSA) higher hs-CRP and CRP were observed, compared to controls. With the present systematic review, meta-analysis and meta-regression we expand upon previous meta-analyses in four ways: (1) We included 109 studies (96 in adults and 13 in children); (2) we reported subgroup and meta-regression analyses in adults with OSA compared to controls on the serum and plasma levels of hs-CRP; (3) we reported subgroup and meta-regression analyses in adults with OSA compared to controls on the serum and plasma levels of CRP; (4) we reported serum and plasma levels of both hs-CRP and CRP in children with OSA, always compared to controls. (2) Materials and Methods: The PubMed/Medline, Scopus, Cochrane Library, and Web of Science databases were searched to retrieve articles published until 31 May 2020, with no restrictions. The data included basic information involving the first author, publication year, country of study, ethnicity of participants in each study, age, BMI, and AHI of both groups, and mean and standard deviation (SD) of plasma and serum levels of CRP and hs-CRP. (3) Results: A total of 1046 records were retrieved from the databases, and 109 studies were selected for the analysis (96 studies reporting the blood levels of hs-CRP/CRP in adults and 13 studies in children). For adults, 11 studies reported plasma hs-CRP, 44 serum hs-CRP, 9 plasma CRP, and 32 serum CRP levels. For children, 6 studies reported plasma hs-CRP, 4 serum hs-CRP, 1 plasma CRP, and 2 serum CRP levels. Compared to controls, the pooled MD of plasma hs-CRP levels in adults with OSA was 0.11 mg/dL (p < 0.00001). Compared to controls, the pooled MD of serum hs-CRP levels in adults with OSA was 0.09 mg/dL (p < 0.00001). Compared to controls, the pooled MD of plasma CRP levels in adults with OSA was 0.06 mg/dL (p = 0.72). Compared to controls, the pooled MD of serum CRP levels in adults with OSA was 0.36 mg/dL (p < 0.00001). Compared to controls, the pooled MD of plasma hs-CRP, serum hs-CRP, plasma hs-CRP, and serum hs-CRP in children with OSA was 1.17 mg/dL (p = 0.005), 0.18 mg/dL (p = 0.05), 0.08 mg/dL (p = 0.10), and 0.04 mg/dL (p = 0.33), respectively. The meta-regression showed that with a greater apnea-hypapnea index (AHI), serum hs-CRP levels were significantly higher. (4) Conclusions: The results of the present systematic review, meta-analysis and meta-regression showed that compared to healthy controls plasma and serum levels of hs-CRP and serum CRP level were higher in adults with OSA; for children, and compared to controls, just plasma hs-CRP levels in children with OSA were higher.

The Association Between Serum/Plasma Leptin Levels and Obstructive Sleep Apnea Syndrome: A Meta-Analysis and Meta-Regression

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is associated with various adipokines. Leptin, a common adipokine, has attracted considerable attention of many researchers in recent years. So far, there has been little agreement on whether blood leptin levels differ in patients with OSAS. Thus, this meta-analysis examined the relationship between serum/plasma leptin levels and the occurrence of OSAS.

METHOD

WanFang, Embase, CNKI, Medline, SinoMed, Web of Science, and PubMed were searched for articles before March 30, 2021, with no language limitations. STATA version 11.0 and R software version 3.6.1 were used to analyze the obtained data. The weighted mean difference and correlation coefficients were used as the main effect sizes with a random-effects model and a fixed-effects model, respectively. Trial sequential analysis was conducted using dedicated software.

RESULT

Screening of 34 publications identified 45 studies that met the inclusion criteria of this meta-analysis and meta-regression. Our results suggested that plasma/serum leptin levels were remarkably higher in individuals with OSAS than in healthy individuals. Subgroup analyses were performed based on OSAS severity, ethnicity, age, body mass index, assay type, and sample source. The serum and plasma leptin levels were increased in nearly all OSAS subgroups compared to those in the corresponding control groups. Meta-regression analysis indicated that age, BMI, severity, assay approaches, study design, PSG type and ethnicity did not have independent effect on leptin levels. Furthermore, a positive relationship between the serum/plasma leptin level and apnea-hypopnea index (AHI) was found in the meta-analysis. The results of the trial sequential analysis suggested that the enrolled studies surpassed the required information size, confirming that our study findings were reliable.

CONCLUSION

Our study results demonstrate that OSAS patients have higher leptin levels in serum/plasma compared to controls, and the serum/plasma leptin level is positively correlated with AHI, especially in adults.

Carotid Body and Metabolic Syndrome: Mechanisms and Potential Therapeutic Targets

The carotid body (CB) is responsible for the peripheral chemoreflex by sensing blood gases and pH. The CB also appears to act as a peripheral sensor of metabolites and hormones, regulating the metabolism. CB malfunction induces aberrant chemosensory responses that culminate in the tonic overactivation of the sympathetic nervous system. The sympatho-excitation evoked by CB may contribute to the pathogenesis of metabolic syndrome, inducing systemic hypertension, insulin resistance and sleep-disordered breathing. Several molecular pathways are involved in the modulation of CB activity, and their pharmacological manipulation may lead to overall benefits for cardiometabolic diseases. In this review, we will discuss the role of the CB in the regulation of metabolism and in the pathogenesis of the metabolic dysfunction induced by CB overactivity. We will also explore the potential pharmacological targets in the CB for the treatment of metabolic syndrome.

Impact of CPAP treatment on leptin and adiponectin in adults with coronary artery disease and nonsleepy obstructive sleep apnoea in the RICCADSA trial

BACKGROUND

Increased leptin and decreased adiponectin levels are reported in coronary artery disease (CAD) as well as in obstructive sleep apnoea (OSA). Less is known regarding the impact of continuous positive airway pressure (CPAP) on these biomarkers. We aimed to determine variables associated with leptin and adiponectin in adults with CAD and nonsleepy OSA, and evaluate the effect of CPAP adjusted for confounding factors.

METHODS

This was one of the secondary outcomes of the RICCADSA trial, conducted in Sweden between 2005 and 2013. From 244 revascularized CAD and OSA patients (apnoea-hypopnoea index >15/h) without excessive daytime sleepiness (Epworth Sleepiness Scale score <10), 196 with blood samples at baseline, after 3, and 12 months were included in the randomized controlled trial arm; of those, 98 were allocated to auto-titrating CPAP, and 98 to no-CPAP.

RESULTS

No significant changes in leptin and adiponectin levels were observed during follow-up, whereas Body-Mass-Index and waist circumference increased in both CPAP and no-CPAP groups with no significant between-group differences. Alterations in plasma leptin were determined by changes in waist circumference (beta coefficient 2.47; 95% confidence interval 0.77-4.40), whereas none of the analyzed parameters was predictive for changes in adiponectin levels. No association was found with CPAP adherence.

CONCLUSIONS

CPAP had no significant effect on leptin and adiponectin in this cohort of nonsleepy OSA patients. An increase in waist circumference predicted an increase in plasma levels of leptin after 12 months, suggesting that lifestyle modifications should be given priority in adults with CAD and OSA regardless of CPAP treatment.

Leptin and adiponectin levels in obstructive sleep apnea phenotypes

Objective: To examine the serum levels of leptin and adiponectin in different obstructive sleep apnea (OSA) phenotypes. Methods: Obese patients who were admitted to our sleep laboratory were included. All patients underwent spirometry, daytime arterial blood gas analysis, polysomnography and transthoracic echocardiography. Serum levels of adiponectin and leptin were recorded. Results: Analysis included 146 OSA patients (81 females, 65 males, age: 49.8 ± 10.7 years, body mass index: 40.3 ± 4.9 kg/m², 47.9% severe OSA, 42.5% severe obesity). Females had higher leptin and adiponectin levels (p < 0.001; p < 0.001, respectively). Leptin levels were higher in patients with severe obesity (p < 0.001). Severe OSA patients had lower leptin and adiponectin levels (p = 0.023; p = 0.035, respectively). Conclusion: Adipokine levels were different especially in OSA patients with severe obesity, female gender and severe OSA.

Betatrophin association with serum triglyceride levels in obstructive sleep apnea patients

BACKGROUND

Obstructive sleep apnea (OSA) is a common sleep problem, in which patients are at increased risk for metabolic and cardiovascular problems, including metabolic syndrome, diabetes mellitus (DM), and dyslipidemia. Betatrophin is a novel protein that regulates fatty acid and triglyceride (TG) metabolism and is related to obesity and metabolic abnormalities, including metabolic syndrome, DM, and dyslipidemia. Although OSA and betatrophin share common abnormalities, their relationship has not been investigated.

AIM

The aim of this study is to investigate the relationships among betatrophin, OSA, and the serum lipid profile.

METHODS

Ninety consecutive patients with suspected OSA underwent polysomnography (PSG) to confirm OSA. Plasma betatrophin, leptin, adiponectin, and the full lipid profile were analyzed. The patients were categorized as OSA or control based on the apnea-hypopnea index (AHI).

RESULTS

About 61% of patients had OSA, and 39% had normal PSG. The levels of betatrophin, leptin, and adiponectin were higher in patients with OSA (256.59 ± 29.35, 374.20 ± 37.93, and 17.86 ± 2.63 μg/mL, respectively) compared to the controls (141.86 ± 26.20, 205.53 ± 14.75, and 7.52 ± 1.02 μg/mL, respectively). Betatrophin levels were correlated with the AHI, leptin (r = 0.413, P = 0.002, r = 0.782, P = 0.000). TG levels were significantly higher, and high-density lipoprotein cholesterol (HDL-C) levels were lower, in OSA patients compared to controls (244 ± 20.33 vs. 138 ± 14.89, and 37.21 ± 1.26 vs. 43.78 ± 1.62, respectively). The TG level was correlated with betatrophin (r = 0.353, P = 0.013). Multiple regression analysis showed that the AHI, leptin, and arousals were independent predictors of betatrophin level (B = 1.70 P = 0.046 95%, B = 0.56 P < 0.005, and B = 1, 2, P = 0.003, respectively).

CONCLUSIONS

Our results suggest a complex relationship between OSA, betatrophin, TG, and HDL, as well as other adipokines. Our results require further investigation to assess this complex association and re-evaluate previous related studies.

Role of Leptin in Obstructive Sleep Apnea

Leptin is a peptide hormone produced mainly in white adipose tissue. It is known to regulate energy homeostasis, inflammation, metabolism, and sympathetic nerve activity. Increasing evidence suggests it has a role in ventilatory function and upper airway obstruction. Leptin levels correlate positively with measurements of adiposity and can potentially provide important insights into the pathophysiology of diseases associated with obesity. Obesity is a strong risk factor for obstructive sleep apnea, a disease characterized by periodic upper airway occlusion during sleep. The neuromuscular activity that maintains upper airway patency during sleep and the anatomy of upper airway are key factors involved in its pathogenesis. Experimental studies using animal models of a low leptin state such as leptin deficiency have shown that leptin regulates sleep architecture, upper airway patency, ventilatory function, and hypercapnic ventilatory response. However, findings from human studies do not consistently support the data from the animal models. The effect of leptin on the pathophysiology of obstructive sleep apnea is being investigated, but the results of studies have been confounded by leptin's diurnal variation and the short-term effects of feeding, adiposity, age, and sex. Improved study design and methods of assessing functional leptin levels, specifically their central versus peripheral effects, will improve understanding of the role of leptin in sleep apnea.

Continuous Positive Airway Pressure Reduces Night-Time Blood Pressure and Heart Rate in Patients With Obstructive Sleep Apnea and Resistant Hypertension: The RHOOSAS Randomized Controlled Trial

Objective

Most patients with resistant hypertension (RH) have obstructive sleep apnea (OSA). We aimed to determine the impact of OSA and continuous positive airway pressure (CPAP) treatment on the leptin profile and blood pressure (BP) in patients with RH.

Methods

After an initial case-control study (RH with and without OSA), we performed a randomized, single blind study in OSA + RH patients receiving either sham CPAP (3 months) followed by active CPAP (6 months) or 6 months of active CPAP. The primary outcome was the comparison of leptin levels between groups of RH patients with or without OSA. Secondary outcomes were the comparison of metabolic parameters, biomarkers of sympathetic activity, and BP indices between the two groups of RH patients with or without OSA. The same outcomes were then evaluated and compared before and after sham and effective CPAP intervention.

Results

Sixty-two patients (60 ± 10 years; 77% men) with RH (24-h daytime systolic BP (SBP)/diastolic BP: 145 ± 13/85 ± 10 mmHg, 3.7 antihypertensive drugs) were included. The 37 RH patients exhibiting OSA (60%) were predominantly men (87 vs 64% for non-OSA patients), with a greater prevalence of metabolic syndrome and higher creatininemia. Their leptin concentrations were significantly lower than in non-OSA patients [9 (6; 15) vs 17 (6; 29) ng/mL] but increased after 6 months of CPAP. Three months of effective CPAP significantly decreased night-time SBP by 6.4 mmHg and heart rate (HR) by 6.0 bpm, compared to sham CPAP.

Conclusion

The association between OSA and RH corresponds to a specific, predominately male phenotype with a higher burden of metabolic syndrome and higher creatininemia but there was no significant difference between OSA and non-OSA patients regarding BP indices, and the number of antihypertensive drugs used. Active CPAP could be efficient at decreasing night-time BP and HR, but there was no difference between CPAP and sham CPAP groups for all metabolic and SNS markers (NCT00746902 RHOOSAS).

Neuropeptides and breathing in health and disease

Regulatory neuropeptides control and regulate breathing in physiological and pathophysiological conditions. While they have been identified in the neurons of major respiratory areas, they can be active not only at the central level, but also at the periphery via chemoreceptors, vagal afferents, or locally within lungs and airways. Some neuropeptides, such as leptin or substance P, are respiratory stimulants; others, such as neurotensin, produce variable effects on respiration depending on the site of application. Some neuropeptides have been implicated in pathological states, such as obstructive sleep apnea or asthma. This article provides a concise review of the possible role and functions of several selected neuropeptides in the process of breathing in health and disease and in lung pathologies.

The serum leptin level in non-obese patients with obstructive sleep apnea

OBJECTIVE

This study aimed to determine the association between the severity of obstructive sleep apnea (OSA) and the serum leptin level in non-obese OSA patients.

METHODS

This prospective case-control study included non-obese OSA patients that presented with sleep-related disturbances and underwent polysomnography (PSG) between April 2015 and June 2016. The serum leptin level was measured and its relationship to PSG parameters was investigated.

RESULTS

The study included 73 OSA patients (20 female and 53 male) with a mean age of 41.1±11.5 years and mean body-mass index (BMI) of 26.4±2.7kgm^-2. The serum leptin level in 44 patients with moderate/severe OSA (AHI ≥15) was 3.4±2.6ngmL^-1, versus 4.5±3.8ngmL^-1 in 29 patients with snoring/mild OSA (AHI <15) (P=0.20). There were not any correlations between any of the PSG parameters and the serum leptin level, but there was a significant correlation between the leptin level and BMI (r=0.345, P<0.01).

CONCLUSION

The serum leptin level does not differ significantly between non-obese OSA patients with moderate/severe and snoring/mild OSA. Obesity is the primary factor associated with the serum leptin level.

Is C-reactive protein a marker of obstructive sleep apnea?: A meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA) is a common disease, distinguished by recurrent episodes of upper airway obstruction during sleep, with an inflammatory component. C-reactive protein (CRP) and high-sensitivity C-reactive protein (hs-CRP) are markers of systemic inflammation and may serve as biomarkers of OSA.

METHODS

Scientific studies published from January 1, 2006, to January 1, 2016 were obtained via searches of PubMed, Embase, SCI, and China National Knowledge Internet (CNKI) using relevant terms. Studies concerning serum CRP level/ hs-CRP in OSA patients were reviewed by 2 independent reviewers. Studies were included if they conform with our specific criteria of inclusion. Eligible studies were subjected to quality review, data extraction, and meta-analysis by using RevMan (version 5.2) and STATA (version 12.0).

RESULTS

There were 15 studies that met inclusion criteria that included a total of 1297 subjects. Meta-analysis revealed that serum CRP levels in the OSA group were 1.98 mmol/L higher than those in control group (95% confidence interval: 1.39-2.58, P < .01). Similarly, serum hs-CRP levels in the OSA group were 1.57 mmol/L higher than that in the control group (95% confidence interval: 0.96-2.18, P < .01). Subgroup analysis showed greater differences between OSA patients and controls in the setting of obesity (body mass index)> = 30. The total weighted mean difference (WMD) between OSA and controls within the subgroup of subjects who had a CRP was 2.10; for hs-CRP, the WMD was 2.49. Comparing OSA patients of mean apnea hypopnea index> = 15 and controls, the total WMD for the CRP subgroup was 2.19; for the hs-CRP subgroup, the WMD was 1.70.

CONCLUSION

In our meta-analysis, serum CRP/hs-CRP levels were discovered to be higher in OSA patients compared with control subjects. Those with higher body mass index and apnea hyponea index demonstrated larger differences in CRP/hs-CRP levels. These data are consistent with an inflammatory component of OSA pathophysiology and support the role of CRP/hs-CRP as a biomarker in this disease.

Relation between serum leptin levels, lipid profiles and neurocognitive deficits in Chinese OSAHS patients

OBJECTIVE

The aim of this study was to compare serum leptin, apolipoprotein A1 (ApoA1), apolipoprotein J (ApoJ) and apolipoprotein H (ApoH) levels in males with obstructive sleep apnea and hypopnea syndrome (OSAHS) to those in healthy control subjects and to examine the possible relation between neurocognitive performance and these factors/serum markers in the subjects.

METHODS

In this observational, cross-sectional study, a full-night polysomnography and sensitive neuropsychological assessment were performed on 50 newly diagnosed Chinese male patients and 30 healthy subjects. Fasting blood samples were used to measure leptin and ApoA1, ApoH and ApoJ levels using ELISA.

RESULTS

Compared with normal control subjects, OSAHS patients have significantly lower levels of ApoA1 and higher levels of leptin, ApoH and ApoJ. After adjustment for age, years of education, body mass index (BMI) and apnea-hypopnea index, leptin and ApoA1 were associated with global cognitive function, and leptin level was positively correlated with inhibition reaction time. ApoJ was negatively correlated with visual reproduction and logical memory performance. Multiple regression analysis shows that from age, BMI, education year, biomarker levels and the parameters of PSG, only the variables of leptin and education year added to the prediction of the Montreal cognitive assessment score in a statistically significant way.

CONCLUSIONS

Abnormal expression of leptin and apolipoproteins and poor performance on neuropsychological tests were observed in patients with OSAHS. There is also an association between serum leptin, ApoA1, and ApoJ levels and cognitive performance in the patients.

Effects of continuous positive airway pressure on energy intake in obstructive sleep apnea: A pilot sham-controlled study

Obesity is among the leading risk factors for obstructive sleep apnea (OSA). A reciprocal relationship between obesity and OSA has been proposed, which may be due to excessive food intake. We conducted a pilot study to test the effects of continuous positive airway pressure (CPAP) on energy intake (EI) in OSA patients using a sham-controlled crossover design. In-laboratory total daily EI was assessed after 2mo of active and sham CPAP. Four men were enrolled (age±SEM: 51.8±2.1y; body mass index: 31.5±1.5kg/m²). All received active treatment first. Meals (breakfast, lunch, dinner, snack) were served in excess portions at fixed times and additional palatable snacks were freely available throughout the day. Total EI was lower after active (3744±511kcal/d) vs. sham (4030±456kcal/d) CPAP but this difference was not significant (p=0.51) due to variability in the free snack intake. When only fixed eating occasions were considered, daily EI was significantly lower in the active (3105±513kcal/d) vs. sham (3559±420kcal/d) condition (p=0.006). This small pilot and feasibility study is the first to utilize a sham-controlled design to investigate the effects of CPAP treatment on objective measures of EI. Findings suggest that CPAP may cause a reduction in fixed meal intake. In demonstrating feasibility of study methodology, our study also suggests a larger randomized sham-controlled trial be conducted to fully characterize the effects of CPAP treatment on EI and energy balance overall.

Effects of continuous positive airway pressure on energy balance regulation: a systematic review

Obesity is both a cause and a possible consequence of obstructive sleep apnoea (OSA), as OSA seems to affect parameters involved in energy balance regulation, including food intake, hormonal regulation of hunger/satiety, energy metabolism and physical activity. It is known that weight loss improves OSA, yet it remains unclear why continuous positive airway pressure (CPAP) often results in weight gain.The goal of this systematic review is to explore if and how CPAP affects the behaviour and/or metabolism involved in regulating energy balance.CPAP appears to correct for a hormonal profile characterised by abnormally high leptin and ghrelin levels in OSA, by reducing the circulating levels of each. This is expected to reduce excess food intake. However, reliable measures of food intake are lacking, and not yet sufficient to make conclusions. Although studies are limited and inconsistent, CPAP may alter energy metabolism, with reports of reductions in resting metabolic rate or sleeping metabolic rate. CPAP appears to not have an appreciable effect on altering physical activity levels. More work is needed to characterise how CPAP affects energy balance regulation.It is clear that promoting CPAP in conjunction with other weight loss approaches should be used to encourage optimal outcomes in OSA patients.

Obstructive Sleep Apnea Is Associated with Elevated High Sensitivity C-Reactive Protein Levels Independent of Obesity: Korean Genome and Epidemiology Study

Obstructive sleep apnea syndrome (OSA) has been recognized as a common health problem, and increasing obesity rates have led to further remarkable increases in the prevalence of OSA, along with more prominent cardiovascular morbidities. Though previous studies have reported an independent relationship between elevated high sensitivity C-reactive protein (hsCRP) levels and OSA, the issue remains controversial owing to inadequate consideration of obesity and various confounding factors. So far, few population based studies of association between OSA and hsCRP levels have been published. Therefore, the purpose of the present study was to investigate whether OSA is associated with increased hsCRP levels independent of obesity in a large population-based study. A total of 1,835 subjects (968 men and 867 women) were selected from a larger cohort of the ongoing Korean Genome and Epidemiology Study (KoGES). Overnight polysomnography was performed on each participant. All participants underwent anthropometric measurements and biochemical analyses, including analysis of lipid profiles and hsCRP levels. Based on anthropometric data, body mass index (BMI) and waist hip ratio (WHR) were calculated and fat mass (FM) were measured by means of multi-frequency bioelectrical impedance analysis (BIA). Mild OSA and moderate to severe OSA were defined by an AHI >5 and ≥15, respectively. The population was sub-divided into 3 groups based on the tertile cut-points for the distribution of hsCRP levels. The percentage of participants in the highest tertile of hsCRP increased dose-dependently according to the severity of OSA. After adjustment for potential confounders and obesity-related variables (BMI, WHR, and body fat) in a multiple logistic model, participants with moderate to severe OSA had 1.73-, 2.01-, and 1.61-fold greater risks of being in the highest tertile of hsCRP levels than participants with non-OSA, respectively. Interaction between obesity (BMI ≥25kg/m²) and the presence of moderate-to-severe OSA was significant on the middle tertile levels of hsCRP (OR = 2.4), but not on the highest tertile, compared to the lowest tertile. OSA is independently associated with elevated hsCRP levels and may reflect an increased risk for cardiovascular morbidity. However, we found that OSA and obesity interactively contribute to individuals with general levels of hsCRP (<1.01 mg/dl). The short-term and long-term effects of elevated hsCRP levels on cardiovascular risk in the context of OSA remain to be defined in future studies.

Obstructive sleep apnea and energy balance regulation: A systematic review

Obesity and obstructive sleep apnea (OSA) have a reciprocal relationship. Sleep disruptions characteristic of OSA may promote behavioral, metabolic, and/or hormonal changes favoring weight gain and/or difficulty losing weight. The regulation of energy balance (EB), i.e., the relationship between energy intake (EI) and energy expenditure (EE), is complex and multi-factorial, involving food intake, hormonal regulation of hunger/satiety/appetite, and EE via metabolism and physical activity (PA). The current systematic review describes the literature on how OSA affects EB-related parameters. OSA is associated with a hormonal profile characterized by abnormally high leptin and ghrelin levels, which may encourage excess EI. Data on actual measures of food intake are lacking, and not sufficient to make conclusions. Resting metabolic rate appears elevated in OSA vs.

CONTROLS

Findings on PA are inconsistent, but may indicate a negative relationship with OSA severity that is modulated by daytime sleepiness and body weight. A speculative explanation for the positive EB in OSA is that the increased EE via metabolism induces an overcompensation in the drive for hunger/food intake, which is larger in magnitude than the rise in EI required to re-establish EB. Understanding how OSA affects EB-related parameters can help improve weight loss efforts in these patients.

Impact of Obstructive Sleep Apnea Syndrome on Endothelial Function, Arterial Stiffening, and Serum Inflammatory Markers: An Updated Meta-analysis and Metaregression of 18 Studies

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) has been indicated to contribute to the development of cardiovascular disease; however, the underlying mechanism remains unclear. This study aimed to test the hypothesis that OSAS may be associated with cardiovascular disease by elevating serum levels of inflammatory markers and causing arterial stiffening and endothelial dysfunction.

METHODS AND RESULTS

Related scientific reports published from January 1, 2006, to June 30, 2015, were searched in the following electronic literature databases: PubMed, Excerpta Medica Database, ISI Web of Science, Directory of Open Access Journals, and the Cochrane Library. The association of OSAS with serum levels of inflammatory markers, endothelial dysfunction, and arterial stiffening were investigated. Overall, 18 eligible articles containing 736 patients with OSAS and 424 healthy persons were included in this meta-analysis. Flow-mediated dilation in patients with moderate-severe OSAS was significantly lower than that in controls (standardized mean difference -1.02, 95% CI -1.31 to -0.73, P<0.0001). Carotid-femoral pulse wave velocity (standardized mean difference 0.45, 95% CI 0.21-0.69, P<0.0001), augmentation index (standardized mean difference 0.57, 95% CI 0.25-0.90, P<0.0001), and serum levels of high-sensitivity C-reactive protein and C-reactive protein (standardized mean difference 0.58, 95% CI 0.42-0.73, P<0.0001) were significantly higher in patients with OSAS than in controls.

CONCLUSION

OSAS, particularly moderate-severe OSAS, appeared to reduce endothelial function, increase arterial stiffness, and cause chronic inflammation, leading to the development of cardiovascular disease.

Obstructive sleep apnea syndrome and cardiovascular disease: The influence of C-reactive protein

Obstructive sleep apnea syndrome (OSAS) is a common medical condition, associated with atherosclerosis and cardiovascular disease (CVD). The underlying pathophysiologic mechanisms of this association have not been completely understood and may be multifactorial in origin. A number of studies suggest that inflammatory processes have emerged critical in the pathogenesis of CVD in OSAS. A range of circulating inflammatory molecules has been identified and measured, with a view to assess inflammation and predict vascular damage risk, such as plasma cytokines, adhesion molecules, and C-reactive protein (CRP). CRP is a relevant marker worthy of further study, because not only is elevated in patients with OSAS, but also is rapidly becoming a risk factor for cardiac disease. Furthermore, in selected OSAS patients, aggressive treatment of the disorder may lead to retarding or even improvement of CVD progression. However, still there is a debate on the true correlation between CRP and OSAS, as well as the clinical effect of any reduction after OSAS treatment. Further research is required to define those OSAS patients who will have a considerable reduction with treatment, as well as to understand the significance of the interaction between cardiovascular risk factor and CRP reduction in patients with OSAS.

Meta-analyses of the Association of Sleep Apnea with Insulin Resistance, and the Effects of CPAP on HOMA-IR, Adiponectin, and Visceral Adipose Fat

OBJECTIVE

We sought to conduct an updated meta-analysis of randomized controlled trials (RCTs) on the effect of continuous positive airway pressure (CPAP) on insulin resistance, as measured by homeostasis model assessment of insulin resistance (HOMA-IR), visceral abdominal fat (VAF), and adiponectin. Additionally, we performed a separate meta-analysis and meta-regression of studies on the association of insulin resistance and obstructive sleep apnea (OSA).

METHODS

All included studies were searched from PubMed (from conception to March 15, 2014). Data were pooled across all included RCTs as the mean difference in HOMA-IR and VAF, and as the standardized mean difference in the case of adiponectin analysis. From the included case-control studies, data on the difference of HOMA-IR between cases and controls were pooled across all studies, as the standardized mean difference (SMD).

RESULTS

There was a significant difference in HOMA-IR (-0.43 [95% CIs: -0.75 to -0.11], p = 0.008) between CPAP treated and non CPAP treated participants. However, there was no significant difference in VAF or adiponectin; (-47.93 [95% CI: -112.58 to 16.72], p = 0.14) and (-0.06 [95% CI: -0.28 to 0.15], p = 0.56), respectively. Meta-analysis of 16 case-control studies showed a pooled SMD in HOMA-IR of 0.51 (95% CI: 0.28 to 0.75), p ≤ 0.001, between cases and controls.

CONCLUSIONS

The results of our meta-analyses show that CPAP has a favorable effect on insulin resistance. This effect is not associated with any significant changes in total adiponectin levels or amount of VAF. Our findings also confirm a significant association between OSA and insulin resistance.

OSAS-related inflammatory mechanisms of liver injury in nonalcoholic fatty liver disease

Obstructive sleep apnoea syndrome (OSAS) is a common sleep disorder, affecting over 4% of the general population, and is associated with metabolic syndrome and cardiovascular disease, independent of obesity and traditional risk factors. OSAS has been recently connected to nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disease in the world, which can be found in 30% of the general adult population. Several studies suggest that the chronic intermittent hypoxia (CIH) of OSAS patients may per se trigger liver injury, inflammation, and fibrogenesis, promoting NAFLD development and the progression from steatosis to steatohepatitis, cirrhosis, and hepatocellular carcinoma. In NAFLD patients, liver disease may be caused by hypoxia both indirectly by promoting inflammation and insulin resistance and directly by enhancing proinflammatory cytokine production and metabolic dysregulation in liver cells. In this review, we focus on molecular mechanisms linking OSAS to NAFLD, including hypoxia inducible factor (HIF), nuclear factor kappa B (NF-κB), YKL-40, unfolded protein response, and hypoxic adipose tissue inflammation, which all could provide novel potential therapeutic approaches for the management of NAFLD patients with OSAS.

Sleep apnea is independently associated with peripheral arterial disease in the Hispanic Community Health Study/Study of Latinos

OBJECTIVE

Sleep apnea (SA) has been linked with various forms of cardiovascular disease, but little is known about its association with peripheral artery disease (PAD) measured using the ankle-brachial index. This relationship was evaluated in the Hispanic Community Health Study/Study of Latinos.

APPROACH AND RESULTS

We studied 8367 Hispanic Community Health Study/Study of Latinos participants who were 45 to 74 years of age. Sleep symptoms were examined with the self-reported Sleep Health Questionnaire. SA was assessed using an in-home sleep study. Systolic blood pressure was measured in all extremities to compute the ankle-brachial index. PAD was defined as ankle-brachial index <0.90 in either leg. Multivariable logistic regression was used to investigate the association between moderate-to-severe SA, defined as apnea-hypopnea index ≥15, and the presence of PAD. Analyses were adjusted for covariates. The prevalence of PAD was 4.7% (n=390). The mean apnea-hypopnea index was significantly higher among adults with PAD compared with those without (11.1 versus 8.6 events/h; P=0.046). After adjusting for covariates, moderate-to-severe SA was associated with a 70% increase in the odds of PAD (odds ratio, 1.7; 95% confidence interval, 1.1-2.5; P=0.0152). This association was not modified by sex (P=0.8739). However, there was evidence that the association between moderate-to-severe SA and PAD varied by Hispanic/Latino background (P<0.01). Specifically, the odds were stronger in Mexican (adjusted odds ratio, 2.9; 95% confidence interval, 1.3-6.2) and in Puerto Rican Americans (adjusted odds ratio, 2.0; 95% confidence interval, 0.97-4.2) than in other backgrounds.

CONCLUSIONS

Moderate-to-severe SA is associated with higher odds of PAD in Hispanic/Latino adults.

Obstructive sleep apnoea, insulin resistance and adipocytokines

Obstructive sleep apnoea (OSA) is associated with multiple cardiometabolic abnormalities. Obesity is considered a major risk factor for the development of OSA, and it is also an established risk factor for insulin resistance and other cardiometabolic disorders. The enigma remains whether OSA has any causal role in the adverse metabolic profile, independent of or beyond that due to obesity. Sleep apnoeas and hypopnoeas result directly in intermittent hypoxaemia and cerebral arousals, both of which may evoke a cascade of downstream biologic responses in various body tissues and cells. Adipose tissue is a major source of adipocytokines many of which play important roles in the regulation of various metabolic functions. It is hypothesized that OSA may, through its unique pathophysiology, affect metabolic function through modulation of production or action of adipocytokines. This review focuses on insulin resistance, glucose metabolism and relevant adipocytokines in the context of OSA.

Effect of continuous positive airway pressure on leptin levels in patients with obstructive sleep apnea: a meta-analysis

OBJECTIVES

Continuous positive airway pressure (CPAP) is an effective treatment for obstructive sleep apnea hypopnea syndrome (OSAHS), but previous studies assessing the effect of CPAP on leptin in patients with OSAHS yielded conflicting results. In this study, we conducted a meta-analysis to determine whether CPAP therapy could reduce serum leptin levels.

DATA SOURCES

Databases of PubMed, Elsevier, and SCI were thoroughly searched by 2 independent reviewers.

METHODS

RevMan (version 5.2) was used for data synthesis. Weighted mean difference (WMD) before and after CPAP therapy was calculated to estimate the effects of CPAP therapy.

RESULTS

A total of 11 studies involving 413 participants were included. Meta-analysis showed that the total WMD for leptin levels was 1.44 units (95% confidence interval: 1.11-1.77, P < .01) before and after CPAP therapy. Subgroup analysis exhibited that leptin was decreased within 3 days after the therapy, and it was further reduced within 1 to 3 months and beyond.

CONCLUSIONS

The results of our meta-analysis showed that CPAP could significantly reduce leptin levels in OSAHS patients without concomitant weight loss.

Low FEV1, smoking history, and obesity are factors associated with oxygen saturation decrease in an adult population cohort

Background

Worsening of pulmonary diseases is associated with a decrease in oxygen saturation (SpO₂). Such a decrease in SpO₂ and associated factors has not been previously evaluated in a general adult population.

Aim

We sought to describe SpO₂ in a sample of adults, at baseline and after 6.3 years, to determine whether factors predicting low SpO₂ in a cross-sectional study were also associated with a decrease in SpO₂ in this cohort.

Methods

As part of the Tromsø Study, 2,822 participants were examined with pulse oximetry in Tromsø 5 (2001/2002) and Tromsø 6 (2007/2008). Low SpO₂ by pulse oximetry was defined as an SpO₂ ≤95%, and SpO₂ decrease was defined as a ≥2% decrease from baseline to below 96%.

Results

A total of 139 (4.9%) subjects had a decrease in SpO₂. Forced expiratory volume in 1 second (FEV₁) <50% of the predicted value and current smoking with a history of ≥10 pack-years were the baseline characteristics most strongly associated with an SpO₂ decrease in multivariable logistic regression (odds ratio 3.55 [95% confidence interval (CI) 1.60–7.89] and 2.48 [95% CI 1.48–4.15], respectively). Male sex, age, former smoking with a history of ≥10 pack-years, body mass index ≥30 kg/m², and C-reactive protein ≥5 mg/L were also significantly associated with an SpO₂ decrease. A significant decrease in FEV₁ and a new diagnosis of asthma or chronic obstructive pulmonary disease during the observation period most strongly predicted a fall in SpO₂. A lower SpO₂ decrease was observed in those who quit smoking and those who lost weight, but these tendencies were not statistically significant.

Conclusion

A decrease in SpO₂ was most strongly associated with severe airflow limitation and a history of smoking. Smoking cessation and reducing obesity seem to be important measures to target for avoiding SpO₂ decreases in the general population.

Obstructive sleep apnoea and diabetes: an update

PURPOSE OF REVIEW

The relationship between obstructive sleep apnoea (OSA) and dysglycaemia is well established. However, uncertainty remains as to the extent that obesity mediates this relationship. The impact of OSA treatment on glucose metabolism and the consequences of having OSA in patients with diabetes is unclear. This review aims to summarize the latest evidence regarding the links between OSA and dysglycaemia.

RECENT FINDINGS

OSA is associated with insulin resistance in lean individuals and predicts insulin resistance worsening longitudinally. Continuous positive airway pressure (CPAP) lowers insulin resistance in CPAP-compliant patients. OSA is associated with impaired β-cell function. In patients with type 2 diabetes (T2D), the association between OSA and glycosylated haemoglobin (HbA1c) is related to nocturnal hypoxaemia. Apnoea hypopnoea index (AHI) during rapid eye movement (REM) (not non-REM) sleep is associated with HbA1c. In-laboratory, supervised CPAP improves glycaemia. OSA is associated with and predicts the progression of some diabetic vascular complications. Intensive lifestyle intervention in patients with T2D improves OSA independent of weight loss.

SUMMARY

OSA is associated with insulin resistance and β-cell dysfunction independent of obesity. OSA is associated with HbA1c and vascular complications in patients with T2D. CPAP might improve insulin resistance and glycaemic measures. Lifestyle intervention has a significant impact on AHI in patients with T2D.

Obstructive Sleep Apnoea and Type 2 Diabetes

With the growing prevalence of obesity, the burden of type 2 diabetes is increasing. Obstructive sleep apnoea (OSA) is a very common medical condition that is associated with increased risk of cardiovascular disease and mortality. Obesity is a common risk factor for OSA and type 2 diabetes and hence it is not surprising that OSA and type 2 diabetes are interlinked. OSA has been shown to be an independent risk factor for the development of incident pre-diabetes/type 2 diabetes. OSA is also associated with worse glycaemic control and vascular disease in patients with type 2 diabetes. However, evidence for the benefits of OSA treatment in patients with type 2 diabetes is still lacking. The aim of this article is to provide an overview of OSA, the relationships between OSA and dysglycaemia and the impact of OSA in patients with type 2 diabetes, highlighting recent advances in the field.

Obstructive sleep apnea and other sleep-related syndromes

Obstructive sleep apnea syndrome (OSAS) is a common disorder characterized by repetitive episodes of breathing cessation due to complete or partial collapse of the upper airway therefore affecting ventilation. It is quite common, with a prevalence of about 2-4%, has a strong genetic component, and creates a proinflammatory state with elevated TNFα and other cytokines. If untreated, OSA can lead to significant neurological problems that include stroke, cognitive decline, depression, headaches, peripheral neuropathy, and nonarteritic ischemic optic neuropathy (NAION). Treatment reverses some of these neurological problems. Treatment includes continuous positive airway pressure and its variants, oral appliances, weight loss, upper airway surgery, and rarely maxillofacial procedures. Other sleep breathing disorders such as hypoventilation, central sleep apnea, complex sleep apnea, and Cheyne-Stokes respiration are less common and are sometimes associated with neuromuscular disorders causing diaphragmatic paralysis, but can also be seen in opiate exposure and severe obesity.

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.

Leptin: a biomarker for sleep disorders?

Leptin, a pleiotropic protein hormone produced mainly by fat cells, regulates metabolic activity and many other physiological functions. The intrinsic circadian rhythm of blood leptin is modulated by gender, development, feeding, fasting, sleep, obesity, and endocrine disorders. Hyperleptinemia is implicated in leptin resistance. To determine the specificity and sensitivity of leptin concentrations in sleep disorders, we summarize here the alterations of leptin in four conditions in animal and human studies: short duration of sleep, sleep fragmentation, obstructive sleep apnea (OSA), and after use of continuous positive airway pressure (CPAP) to treat OSA. The presence and causes of contradictory findings are discussed. Though sustained insufficient sleep lowers fasting blood leptin and therefore probably contributes to increased appetite, obesity and OSA independently result in hyperleptinemia. Successful treatment of OSA by CPAP is predicted to decrease hyperleptinemia, making leptin an ancillary biomarker for treatment efficacy. Current controversies also call for translational studies to determine how sleep disorders regulate leptin homeostasis and how the information can be used to improve sleep treatment.

Obstructive sleep apnea syndrome is associated with metabolic syndrome and inflammation

Obstructive sleep apnea (OSA) is an independent risk factor for cardiovascular morbidity and mortality. However, the underlying mechanism is unclear. In this cross-sectional study, we investigated the influence of OSA on metabolic syndrome (MetS) and inflammation, which were considered as cardiovascular risks. A total of 144 consecutive male patients who underwent standard polysomnography were enrolled. Fasting blood samples were obtained from all patients for glucose, high-sensitivity C-reactive protein (hs-CRP) and lipids measurement. A metabolic score was established as the total number of the positive diagnostic criteria of metabolic syndrome for each patient. Systolic blood pressure, diastolic blood pressure, fasting glucose, hs-CRP and metabolic score significantly increased with the aggravation of OSA severity. Metabolic score increased from 1.74 ± 1.20 to 2.89 ± 0.99 with OSA severity (p = 0.000). hs-CRP increased from 0.68 (0.43-1.10) to 1.44 (0.62-4.02) mg/L with OSA severity (p = 0.002). After adjustment for confounders, apnea-hypopnea index and body mass index (BMI) were the major contributing factors for metabolic score (β = 0.257, p = 0.003 and β = 0.344, p = 0.000, respectively), lowest O2 saturation and BMI were the independent predictors of hs-CRP (β = -0.255, p = 0.003 and β = 0.295, p = 0.001, respectively). OSA is independently associated with sum of metabolic components and hs-CRP.

Pathophysiologic mechanisms of cardiovascular disease in obstructive sleep apnea syndrome

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. Patients with OSAS experience repetitive episodes of hypoxia and reoxygenation during transient cessation of breathing that provoke systemic effects. Furthermore, there may be increased levels of biomarkers linked to endocrine-metabolic and cardiovascular alterations. Epidemiological studies have identified OSAS as an independent comorbid factor in cardiovascular and cerebrovascular diseases, and physiopathological links may exist with onset and progression of heart failure. In addition, OSAS is associated with other disorders and comorbidities which worsen cardiovascular consequences, such as obesity, diabetes, and metabolic syndrome. Metabolic syndrome is an emerging public health problem that represents a constellation of cardiovascular risk factors. Both OSAS and metabolic syndrome may exert negative synergistic effects on the cardiovascular system through multiple mechanisms (e.g., hypoxemia, sleep disruption, activation of the sympathetic nervous system, and inflammatory activation). It has been found that CPAP therapy for OSAS provides an objective improvement in symptoms and cardiac function, decreases cardiovascular risk, improves insulin sensitivity, and normalises biomarkers. OSAS contributes to the pathogenesis of cardiovascular disease independently and by interaction with comorbidities. The present review focuses on indirect and direct evidence regarding mechanisms implicated in cardiovascular disease among OSAS patients.

Glucose tolerance and weight loss in obese women with obstructive sleep apnea

Background

The association of obstructive sleep apnea (OSA) with glucose intolerance and the beneficial effect of lifestyle intervention have been poorly investigated in women particularly before menopausal status. The study explored 1) whether OSA is associated with impaired glucose homeostasis in obese non diabetic premenopausal and menopausal women and 2) the effects of a 3- month lifestyle intervention on glucose homeostasis in OSA women.

Design and Methods

We consecutively recruited 98 obese women (39 premenopausal) from those referred for a weight loss intervention. Ambulatory nocturnal polysomnography, body composition, oral glucose tolerance test, insulin sensitivity and β cell function were assessed before and after intervention.

Results

41% of premenopausal and 64% of menopausal women had OSA which was associated with worse glucose homeostasis before menopausal status. Mean and minimal nocturnal oxygen saturation (SaO₂) was associated with neck/height ratio (NHR), independently of total and central obesity. Mean and minimal nocturnal SaO₂ and NHR were correlated with insulin sensitivity and fasting glucose. In multivariate analyses, nocturnal mean SaO₂ was negatively and independently correlated with fasting glucose (p<0.0001) and NHR with insulin sensitivity (p<0.0001). In OSA women, the intervention induced a 5% weight reduction and a significant increase in minimal nocturnal SaO₂, insulin sensitivity and β cell function. Changes in fasting glucose and insulin sensitivity were associated with those in minimal nocturnal SaO₂ (p<0.05) and not with weight loss.

Conclusions

In obese women, glucose homeostasis worsens due to nocturnal hypoxia and increased neck circumference through mechanisms partially independent of obesity. OSA is more clearly associated with glucose intolerance in premenopausal than in menopausal women. In OSA women, the improvement of nocturnal hypoxia induced by lifestyle modifications is associated with that of glucose homeostasis.

Correlation between endothelial dysfunction, Rho-associated protein kinase activity, C-reactive protein and obstructive sleep apnoea syndrome in male patients

OBJECTIVE

This study investigated the association between obstructive sleep apnoea syndrome (OSAS) and flow-mediated dilatation (FMD), Rho-associated protein kinase (ROCK) activity, and C-reactive protein (CRP) concentrations in male patients.

METHODS

Consecutive patients with symptoms suggestive of OSAS were recruited and divided into non-OSAS (n = 18) and OSAS (n = 32) groups. FMD was measured in the brachial artery; blood samples were taken to measure ROCK activity and CRP concentrations.

RESULTS

ROCK activity and CRP concentrations were significantly higher, and FMD was significantly lower, in the OSAS group than in the non-OSAS group. There was a correlation between ROCK activity and FMD. In stepwise multiple regression analyses, the proportion of sleep time spent with an oxygen saturation < 90% was a significant determinant of ROCK activity, while body mass index was the only significant determinant of CRP concentration. The oxygen desaturation index was a significant determinant of FMD.

CONCLUSIONS

OSAS increased ROCK activity and was a major determinant of endothelial dysfunction.

The role of obesity, different fat compartments and sleep apnea severity in circulating leptin levels: the Icelandic Sleep Apnea Cohort study

Objectives

To assess whether sleep apnea severity has an independent relationship with leptin levels in blood after adjusting for different measures of obesity and whether the relationship between OSA severity and leptin levels differs depending on obesity level.

Methods

Cross-sectional study of 452 untreated obstructive sleep apnea (OSA) patients (377 males and 75 females), in the Icelandic Sleep Apnea Cohort (ISAC), age 54.3±10.6 (mean±SD), BMI 32.7±5.3 kg/m² and apnea-hypopnea index (AHI) 40.2 ± 16.1 events/hour. A sleep study and magnetic resonance imaging of abdominal visceral and subcutaneous fat volume were performed as well as fasting serum morning leptin levels measured.

Results

Leptin levels were more highly correlated with body mass index (BMI), total abdominal and subcutaneous fat volume than visceral fat volume per se. No relationship was found between sleep apnea severity and leptin levels, assessed within three BMI groups (BMI<30, BMI 30–35 and BMI>35 kg/m²). In a multiple linear regression model, adjusted for gender, BMI explained 38.7% of the variance in leptin levels, gender explained 21.2% but OSA severity did not have a significant role and no interaction was found between OSA severity and BMI on leptin levels. However, hypertension had a significant effect on the interaction between OSA severity and obesity (p=0.04). In post-hoc analysis for nonhypertensive OSA subjects (n=249), the association between leptin levels and OSA severity explained a minor but significant variance (3.2%) in leptin levels. This relationship was greatest for nonobese nonhypertensive subjects (significant interaction with obesity level). No relationship of OSA severity and leptin levels was found for hypertensive subjects (n=199).

Conclusion

Obesity and gender are the dominant determinants of leptin levels. OSA severity is not related to leptin levels except to a minor degree in nonhypertensive nonobese OSA subjects.

Coagulability in obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is a common disorder that affects both quality of life and cardiovascular health. The causal link between OSA and cardiovascular morbidity⁄mortality remains elusive. One possible explanation is that repeated episodes of nocturnal hypoxia lead to a hypercoagulable state that predisposes patients to thrombotic events. There is evidence supporting a wide array of hematological changes that affect hemostasis (eg, increased hematocrit, blood viscosity, platelet activation, clotting factors and decreased fibrinolytic activity).

OBJECTIVE

To provide a comprehensive review of the current evidence associating OSA with increased coagulability, and to highlight areas for future research.

METHODS

Keyword searches in Ovid Medline were used to identify relevant articles; all references in the articles were searched for relevant titles. The Web of Science was used to identify articles citing the relevant articles found using the Ovid Medline search. All original peer-reviewed articles, meta-analyses and systematic reviews regarding the pertinent topics between 1990 and present were selected for review.

RESULTS

Hematocrit, blood viscosity, certain clotting factors, tissue factor, platelet activity and whole blood coagulability are increased in patients with OSA, while fibrinolysis is impaired.

CONCLUSION

There is considerable evidence that OSA is associated with a procoagulant state. Several factors are involved in the procoagulant state associated with OSA. There is a need for adequately powered clinical studies involving well-matched control groups to address potential confounding variables, and to accurately delineate the individual factors involved in the procoagulant state associated with OSA and their response to treatment.

Effect of continuous positive airway pressure on C-reactive protein levels in sleep apnea: a meta-analysis

OBJECTIVE

Evaluate the effects of continuous positive airway pressure (CPAP) on C-reactive protein (CRP) levels, reported either as a primary or secondary end point among patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) based on a meta-analysis of published studies.

DATA SOURCES

English-language searches of PubMed, Ovid, and the Cochrane databases were completed. Reference sections of identified studies were also examined for additional relevant articles to review.

REVIEW METHODS

Studies of adult patients with OSAHS who reported pre- and post-CPAP treatment CRP were reviewed and analyzed. Two independent reviewers extracted data from 10 peer-reviewed studies, which were combined using a random effects meta-analysis model.

RESULTS

The CPAP treatment was found to lead to a significant reduction in CRP levels (17.8%, P = .002). This corresponds to an effect size of -0.485 (-0.731, -0.240). Sensitivity analysis was done to determine the impact of study design. Both case-control studies and case-series studies yielded a significant effect. Sensitivity analysis also yielded a significant effect for studies with average body mass index <30, studies where CPAP was employed over automatic positive airway pressure, and studies treating patients ≤ 3 months. Analysis of publication bias, however, revealed a likelihood of "missing" studies.

CONCLUSION

Although there is a significant lack of high-quality studies addressing this question, this analysis suggests that treatment with CPAP leads to a statistically significant reduction in CRP levels. However, the mean pre- and posttreatment CRP levels observed are considered "high risk" for cardiovascular morbidity. The clinical significance of this finding as it relates to cardiovascular risk reduction and the relationship between CRP and OSAHS requires further study.