Association between obstructive sleep apnea severity and endothelial dysfunction in an increased background of cardiovascular burden

Implication of a novel measure of obstructive sleep apnea severity for cardiovascular morbidity

OBJECTIVE

To evaluate the association between cardiovascular morbidity and obstructive sleep apnea (OSA) severity quantified using the sleep breathing impairment index (SBII), a novel measure that captures both respiratory events and event-associated hypoxia.

PATIENTS AND METHODS

This retrospective follow-up study included 737 participants with OSA who were diagnosed based on an apnea-hypopnea index of >5/h in polysomnography from January 1, 2012 to December 31, 2015. Data on baseline clinical characteristics and polysomnography parameters were collected. SBII was determined as the sum of products of respiratory events and event-related desaturation areas, and was categorized based on its quintiles. The outcomes were any hospital admission for cardiovascular diseases, including coronary heart disease, stroke, peripheral vascular disease, or heart failure after the diagnosis of OSA. Logistic regression models were constructed to estimate the potential association between SBII and cardiovascular morbidity after adjusting for confounders.

RESULTS

A total of 60 cardiovascular events were recorded. Compared with the first quintile of SBII, the odds ratio (95% confidence interval [CI]) of cardiovascular morbidity for the second, third, and fourth quintiles were 4.01 (95% CI, 1.22-13.24), 3.91 (95% CI, 1.05-14.53), and 7.57 (95% CI, 1.70-33.68) after adjusting for covariables, including anthropometric variables, medical conditions, and sleep parameters.

CONCLUSION

In patients with OSA, higher SBII was associated with an increased cardiovascular risk. These findings suggest that a more comprehensive measure, such as SBII incorporating the respiratory event and related hypoxia during sleep, may better capture the disease burden and reflect the OSA-associated adverse outcomes.

Influence of Apnea Hypopnea Index and the Degree of Airflow Limitation on Endothelial Function in Patients Undergoing Diagnostic Coronary Angiography

Background: Obstructive sleep apnea is associated with an increased prevalence of cardiovascular disease. The mechanism of these associations is not completely understood. We aimed to investigate the association of the apnea hypopnea index and the degree of airflow limitation with endothelial dysfunction. Methods: This was a single-center prospective study of patients admitted for diagnostic coronary angiography (CAG). Endothelial function was assessed by the non-invasive EndoPAT system by reactive hyperemia index (RHI) and divided into two groups: endothelial dysfunction and normal endothelial function. Sleep apnea signs were detected by WatchPAT measuring the respiratory disturbance index (pRDI), the apnea and hypopnea index (pAHI), and the oxygen desaturation index (ODI). Patients underwent spirometry and body plethysmography. Based on CAG, the severity of coronary artery disease was assessed as follows: no significant coronary artery disease, single-, two- and three-vessel disease. Results: A total of 113 patients were included in the study. Breathing disorders measured by WatchPAT and spirometry were more severe in patients with endothelial dysfunction: pRDI (27.3 vs. 14.8, p = 0.001), pAHI (24.6 vs. 10.3, p < 0.001), ODI (13.7 vs. 5.2, p = 0.002), forced expiratory volume in one second (FEV1) (81.2 vs. 89, p = 0.05). In a multivariate regression analysis, pAHI and FEV1 were independent predictors of endothelial dysfunction assessed by RHI. There was no correlation between the severity of coronary artery disease and endothelial dysfunction. Conclusions: Obstructive sleep apnea signs and greater airflow limitation were associated with endothelial dysfunction regardless of the severity of the coronary artery disease.

The effects of exercise training on vascular function among overweight adults with obstructive sleep apnea

Obstructive sleep apnea (OSA) is associated with increased cardiovascular morbidity due, in part, to impaired vascular function. Exercise confers cardioprotection by improving vascular health. Yet, whether OSA severity affects the vascular improvements conferred with exercise training is not known. Overweight (body mass index (BMI) >27 kg/m²) adults were evaluated for OSA and enrolled in a six-week exercise intervention. Baseline assessments of brachial artery flow-mediated dilation (BAFMD), central augmentation index (AIx) and pulse wave velocity (PWV) were repeated post training. Fifty-one participants (25 men; 26 women) completed the study. Despite improved aerobic capacity (p=0.0005) and total fat mass (p=0.0005), no change in vascular function was observed. Participants were divided into two severity groups according to their baseline total apnea-hypopnea index (AHI) as either 5 to 14.9 events•hr^-1 (n= 21; Age=48 ± 7 yrs; BMI=33.7 ± 4.6kg•m^-2) or 15 ≥events•hr^-1 (n=30; Age=56 ± 13 yrs; BMI = 34.3 ± 4.2 kg•m^-2). No effect of OSA group was observed for BAFMD (p=0.82), AIx (p=0.37) or PWV (p=0.44), suggesting that OSA severity does not influence the effect of exercise on vascular function. The vascular effects of extended exercise programs of greater intensity in overweight OSA patients should be examined.

Polysomnographic Phenotypes of Obstructive Sleep Apnea and Incident Type 2 Diabetes: Results from the DREAM Study

Rationale: Obstructive sleep apnea (OSA) is associated with cardiovascular disease and incident type 2 diabetes (T2DM). Seven OSA phenotypes, labeled on the basis of their most distinguishing polysomnographic features, have been shown to be differentially associated with incident cardiovascular disease. However, little is known about the relevance of polysomnographic phenotypes for the risk of T2DM. Objectives: To assess whether polysomnographic phenotypes are associated with incident T2DM and to compare the predictive value of baseline polysomnographic phenotypes with the Apnea-Hypopnea Index (AHI) for T2DM. Methods: The study included 840 individuals without baseline diabetes from a multisite observational U.S. veteran cohort who underwent OSA evaluation between 2000 and 2004, with follow-up through 2012. The primary outcome was incident T2DM, defined as no diagnosis at baseline and a new physician diagnosis confirmed by fasting blood glucose >126 mg/dL during follow-up. Relationships between the seven polysomnographic phenotypes (1. mild, 2. periodic limb movements of sleep [PLMS], 3. non-rapid eye movement and poor sleep, 4. rapid eye movement and hypoxia, 5. hypopnea and hypoxia, 6. arousal and poor sleep, and 7. combined severe) and incident T2DM were investigated using Cox proportional hazards regression and competing risk regression models with and without adjustment for baseline covariates. Likelihood ratio tests were conducted to compare the predictive value of the phenotypes with the AHI. Results: During a median follow-up period of 61 months, 122 (14.5%) patients developed incident T2DM. After adjustment for baseline sociodemographics, fasting blood glucose, body mass index, comorbidities, and behavioral risk factors, hazard ratios among persons with "hypopnea and hypoxia" and "PLMS" phenotypes as compared with persons with "mild" phenotype were 3.18 (95% confidence interval [CI], 1.53-6.61] and 2.26 (95% CI, 1.06-4.83) for incident T2DM, respectively. Mild OSA (5 ⩽ AHI < 15) (vs. no OSA) was directly associated with incident T2DM in both unadjusted and multivariable-adjusted regression models. The addition of polysomnographic phenotypes, but not AHI, to known T2DM risk factors greatly improved the predictive value of the computed prediction model. Conclusions: Polysomnographic phenotypes "hypopnea and hypoxia" and "PLMS" independently predict risk of T2DM among a predominantly male veteran population. Polysomnographic phenotypes improved T2DM risk prediction comared with the use of AHI.

Nailfold capillaroscopic changes of sleep apnea patients

BACKGROUND

Obstructive Sleep Apnea Syndrome (OSAS) have frequent association with comorbidities and this makes it an independent risk factor for cardiovascular disease. Not only endothelial dysfunction, but also arterial stiffening, increased inflammatory mediators, oxidative stress after hypoxemia that develops due to OSAS, cause vascular pathologies in all diameters of vessels. Nail bed capillaroscopy is a simple, noninvasive, useful method to examine microcirculation and evaluate nail bed capillary abnormalities in diseases that cause vascular damage. The aim of this study is to examine microvascular changes in the nail bed of OSAS patients by capillaroscopy.

METHODS

59 OSAS patients and 60 healthy cases (totally 119) were included. One single attended polysomnography was applied with Embla N7000 series (RemLogic Eastmed, Natus); and apnea-hypopnea index (AHI), oxygen de-saturation index >4% (ODI4%), minimum oxygen saturation (SaO2 Min.), total duration of oxygen desaturation, comorbidities, body mass index (BMI), smoking habit, sleep questionnaire applications were analyzed. Nailfold capillaroscopy was performed using a digital dermoscope (Molemax II, X30) and all images were evaluated for capillary density, capillary loop enlargement, capillary tortuosity, branching vessels, micro hemorrhages, avascular areas and splinter hemorrhages.

RESULTS

The prevalence rates of all capillaroscopy findings were significantly higher in the patient group (p < 0.05). There was an inverse and moderate relationship between AHI and mean saturation (p < 0.05). A statistically significant correlation was detected between the presence of hypertension (HT) and the severity of capillary tortuosity (CT) (p = 0.002), avascular area (AA) (p = 0.004), and periungual cyanosis (PUC) (p = 0.042); also between smoking habit and intensity of capillary dilatation, enlargement dilatation-enlarged giant capillaries (CELON) (p = 0.004), CT (p = 0.018) findings. Capillary distribution (CD), CELON, CT and AA findings were significantly higher in the group with low mean saturation (p < 0.05). DM was found to be significantly higher in individuals with high Epworth Sleep Scale (ESS) (p = 0.035).

CONCLUSION

In this study; 1) the nail bed capillaroscopy was used to examine vascular damage in OSAS, and 2) irregularities detected in the distal nail bed specific to a disease have been mentioned for the first time. It has been shown that endothelial damage is particularly related to the severity of hypoxia. HT and smoking history causes endothelial damage independent of the severity of the disease and hypoxia. Also, ESS may be more determinant in the screening of sleep disorders in diabetic patients.

Ghrelin suppresses migration of macrophages via inhibition of ROCK2 under chronic intermittent hypoxia

Objectives

Migration of macrophages and atherosclerosis result in various diseases, including coronary heart disease. This study aimed to clarify the roles that ghrelin and Rho-associated coiled-coil-containing protein kinase 2 (ROCK2) play in migration of macrophages under chronic intermittent hypoxia (CIH).

Methods

A rat model of CIH was constructed and changes in ghrelin and ROCK2 protein expression were measured by western blot assay. The migratory ability of macrophages was determined by the transwell assay. Hematoxylin and eosin staining was applied to detect the changes in intima-media thickness.

Results

We found that CIH enhanced migration of macrophages, and this effect was attenuated by exogenous ghrelin. Additionally, the facilitative effect of CIH on migration of macrophages was strengthened or decreased by upregulation or downregulation of ROCK2, respectively. This phenomenon indicated that ROCK2 was involved in CIH-induced migration in macrophages. Furthermore, western blot and transwell assays showed that ghrelin inhibited CIH-induced migration via ROCK2 suppression in macrophages.

Conclusions

In summary, the present study shows that ghrelin inhibits CIH-induced migration via ROCK2 suppression in macrophages. Our research may help lead to identifying a new molecular mechanism for targeted therapy of atherosclerosis and its associated coronary artery diseases under intermittent hypoxia.

How Are Sleep Characteristics Related to Cardiovascular Health? Results From the Population-Based HypnoLaus study

Background Although sleep characteristics have been linked to cardiovascular disease and cardiovascular risk factors, the association between sleep characteristics measured by polysomnography and cardiovascular health ( CVH ) remains unknown. Methods and Results In a population-based sample (n=1826), sleep characteristics were assessed by both sleep questionnaires and polysomnography. Global, behavioral, and biological CVH were defined according to the American Heart Association. Multinomial logistic regressions were performed to estimate relative risk ratios and 95% CI . Strong dose-response associations were found between all oxygen saturation-related variables (oxygen desaturation index, mean oxygen saturation, and percentage of total sleep time spent under 90% oxygen saturation) and obstructive sleep apnea (severity categories and apnea/hypopnea index) and global, behavioral, and biological CVH . Mean oxygen saturation had the strongest positive association (relative risk ratios 1.31 [ CI 1.22-1.41]; 1.78 [ CI 1.55-2.04] for intermediate relative to ideal CVH ), and oxygen desaturation index had the strongest negative association (relative risk ratios 0.71 [ CI 0.65-0.78]; 0.45 [ CI 0.34-0.58] for intermediate relative to ideal CVH ) with global CVH , and these associations were also the most robust in sensitivity analyses. The impacts of sleep architecture and sleep fragmentation were less consistent. Conclusions Mean oxygen saturation, oxygen desaturation index, and apnea/hypopnea index were associated with CVH . Conversely, most variables related to sleep architecture and sleep fragmentation were not consistently related to CVH . Sleep-disordered breathing and the associated oxygen (de)saturation were associated with CVH more strongly than with sleep fragmentation.

Accumulated nocturnal hypoxemia predict arterial endothelial function in patients with sleep-disordered breathing with or without chronic heart failure

ABTSRACT

Sleep-disordered breathing (SDB) is often accompanied with the chronic heart failure (CHF). Hypoxemia due to pulmonary congestion from CHF and concurrent SDB might synergistically impair endothelial function and worsen the prognosis. However, the main factors affecting deterioration of endothelial function are unknown and whether the influence of hypoxemia differs in SDB patients with and without CHF remains unclear. Fifty-three patients (CHF group, n = 23; non-CHF group, n = 30) underwent polysomnography to evaluate their SDB and flow-mediated vasodilation (FMD) measurements to assess arterial endothelial function. We examined the relationships between FMD and SDB-related parameters, including our original index of accumulated hypoxemia by SDB throughout one-night sleep: the time desaturation summation index (TDS), calculated as follows: (100% - averaged arterial oxygen saturation during sleep) × total sleep time. The mean age in the CHF and non-CHF groups was 59.0 ± 13.5 and 57.7 ± 11.4 years, respectively. Although the FMD in the 2 groups were not significantly different, well-known adverse factors for FMD such as serum lipid profiles, blood pressure levels, and conventional indices of SDB were worse in the non-CHF group. Only the TDS was not significantly different between 2 groups and associated with FMD as shown by the univariate analysis (CHF: p < 0.05, non-CHF: p < 0.01) and multivariate analysis (CHF: p < 0.05, non-CHF: p < 0.01). Accumulated hypoxemia (TDS) rather than the frequency of hypoxemia might more influence on the endothelial function irrespective of the cardiac state. Removal of accumulation of nocturnal hypoxemia might be a target for treatment equally in the patients with and without CHF.

Sleep disordered breathing in Marfan syndrome: Value of standard screening questionnaires

Background

A high prevalence of sleep disordered breathing (SDB) has been reported in persons with Marfan syndrome (MFS), a single gene disorder of connective tissue resulting in premature death from aortic rupture. The burden of SDB and accompanying hemodynamic stress could warrant broad screening in this population. Our goal was to assess the utility of traditional SDB screening tools in our sample of persons with MFS.

Methods

Participants were recruited during an annual Marfan Foundation meeting and Marfan status confirmed using the Ghent criteria. Screening questionnaires were administered and SDB assessed by home sleep testing. We assessed accuracy of screening tools using receiver‐operating characteristic curve analyses.

Results

The prevalence of moderate‐severe SDB was 32% in our sample of 31 MFS participants. The Stop‐Bang questionnaire had the highest positive predictive value (PPV) of 60% and the highest negative predictive value (NPV) of 100% using the high‐ and moderate‐risk cut‐offs, respectively, and the Berlin questionnaire had a PPV of 50% and an NPV of 92.3% at the high‐risk cut‐off. When those with mild SDB were included, the Stop‐Bang and the Sleep Apnea Clinical Score (SACS) questionnaires demonstrated useful screening accuracies with PPVs of 94.7% and 92.9%, and NPVs of 63.6% and 47.1%, respectively, at the moderate‐risk cut‐offs.

Conclusion

A survey of SDB in a sample of persons with MFS reveals not only a high burden of SDB but also that conventional screening instruments have utility if adapted appropriately. Future studies should validate the utility of these screening tools given concerns that SDB may contribute to progression of aortic pathology in MFS.

Association between nondipping pattern and EndoPAT signal in patients with mild obstructive sleep apnea

OBJECTIVE

To compare vascular endothelial function between dipping (D) and nondipping (ND) patterns in patients with and without mild obstructive sleep apnea (OSA) using EndoPAT, a test of reactive hyperemia used to assess peripheral vascular endothelial function.

METHODS

The sample consisted of individuals of both genders between 18 and 65 years of age with a body mass index (BMI) of ≤35 kg/m² and apnea/hypopnea index (AHI) of ≤15. The nondipping pattern was considered present when the dip of nocturnal blood pressure (NBP) was <10%. All of the sample underwent clinical and physical evaluation, full polysomnography, 24-hour ambulatory blood pressure monitoring, and EndoPAT evaluation. A generalized linear model was used for statistical analysis.

RESULTS

The sample comprised 120 individuals, 35 in the control group and 85 in the mild OSA group. Four groups were formed: Control-ND, Control-D, Mild OSA-ND, and Mild OSA-D according to nocturnal ABPM patterns. The frequency of nondipping was (34.1%) in the Mild OSA group and (17.1%) in the Control group (p = 0.07). The Mild OSA-ND group had a higher augmentation index (AIx) than the Mild OSA-D group. Regression analysis showed that male gender, higher age, and nondipping status were associated with these results, whereas oxygen desaturation index (ODI) and AHI did not. With respect to the reactive hyperemia index (RHI), the Mild OSA-D group had lower values compared to the Control-ND group, but an association with OSA was not confirmed in the regression model.

CONCLUSION

Nondipping status was associated with a worse augmentation index in both groups independently of AHI or oxygen desaturation index. Male gender, higher age, and nondipping status were associated with augmentation index. ClinicalTrials.gov Identifier: NCT01461486.

Association of obstructive sleep apnea with microvascular endothelial dysfunction and subclinical coronary artery disease in a community-based population

Studies have reported an association between obstructive sleep apnea (OSA) and cardiovascular disease (CVD) morbidity and mortality. Proposed mechanisms include endothelial dysfunction and atherosclerosis. We aimed to investigate the associations of OSA with endothelial dysfunction and subclinical atherosclerotic coronary artery disease (CAD), and assess the impact of race on these associations. We used data from the Heart Strategies Concentrating on Risk Evaluation (Heart SCORE) study, a community-based prospective cohort with approximately equal representation of black and white participants. OSA severity was measured in 765 individuals using the apnea-hypopnea index (AHI). Endothelial dysfunction was measured using the Endo-PAT device, expressed as Framingham reactive hyperemia index (F_RHI). Coronary artery calcium (CAC), a marker of subclinical CAD, was quantified by electron beam computed tomography. There were 498 (65%) female participants, 282 (37%) black individuals, and 204 (26%) participants with moderate/severe OSA (AHI ≥15). In univariate models, moderate/severe OSA was associated with lower F_RHI and higher CAC, as well as several traditional CVD risk factors including older age, male sex, hypertension, diabetes, higher body mass index, and lower high-density lipoprotein cholesterol levels. In a multivariable model, individuals with moderate/severe OSA had 10% lower F_RHI and 35% higher CAC, which did not reach statistical significance ( p=0.08 for both comparisons). There was no significant interaction of race on the association of OSA with F_RHI or CAC ( p-value >0.1 for all comparisons). In a community-based cohort comprised of black and white participants, moderate/severe OSA was modestly associated with endothelial dysfunction and subclinical atherosclerotic CAD. These associations did not vary by race.

Quantitative Retinal Vascular Changes in Obstructive Sleep Apnea

PURPOSE

To examine the relationship between both static and dynamic retinal vascular caliber and the severity of obstructive sleep apnea (OSA).

DESIGN

Prospective cross-sectional study.

METHODS

Adult patients undergoing diagnostic polysomnography studies at a private Australian university teaching hospital were recruited. OSA severity was defined by the apnea-hypopnea index (AHI): severe >30, moderate >15-30, mild 5-15, and controls <5. Of 115 patients recruited (73 male; mean age 58 ± 13 years), there were 41 severe, 35 moderate, and 25 mild OSA patients and 14 controls. Static retinal vascular caliber was measured as the average diameter of retinal arterioles (CRAE) and venules (CRVE), and summarized as the arteriovenous ratio (AVR). Dynamic retinal vascular caliber was evaluated as the average pulsation amplitude of retinal arterioles (SRAP) and venules (SRVP). Comparisons across groups were performed using multivariate linear regression analysis. All results were adjusted for age, body mass index, and mean arterial pressure.

RESULTS

Increasing AHI was significantly associated with decreasing AVR (P = .008) and CRAE (P = .016). A significant relationship was demonstrated between increasing AHI and attenuated retinal vascular pulsation amplitude (arterioles P = .028; venules P < .0001).

CONCLUSIONS

Increasing OSA severity is independently associated with retinal arteriolar narrowing and attenuated vascular pulsation amplitude. The retinal vasculature is easily imaged, and may be a surrogate biomarker of cerebral and systemic vascular risk in patients with OSA requiring further comprehensive investigation.

Meta-Analysis of the Effect of Obstructive Sleep Apnea on Cardiovascular Events After Percutaneous Coronary Intervention

Increasing evidence proved that obstructive sleep apnea (OSA) is associated with a variety of diseases, especially cardiovascular diseases. This study systematically reviewed the existing publications to assess the influence of OSA on cardiovascular survival among patients who underwent percutaneous coronary intervention. Eleven eligible publications, including 3,008 participants, were finally evaluated. Eight studies conducted adjustment of risk ratio for potential cardiovascular risk factors, 5 studies defined OSA groups as AHI (apnea hypopnea index) ≥15/hour, whereas the remaining eligible studies used AHI ≥5/hour, AHI ≥10/hour, or AHI ≥30/hour as the criteria. According to the result from 5 studies that use AHI ≥15/hour as OSA group, the existence of OSA could, to some extent, increase the risk of cardiovascular events (risk ratio 1.59, 95% confidence interval 1.22 to 2.06). Meanwhile, hazard ratio was also observed in separate co-morbidities, such as cardiac death, all-cause mortality, stroke, target lesion revascularization, non-fatal myocardial infarction, hospitalization for heart failure, and recurrence of acute coronary syndrome, regardless if the estimates are varied among studies. In conclusion, OSA can independently increase the risk of cardiovascular events, even after adjustment for confounders. Sleep health should be given utmost importance due to its extensive influence on cardiovascular disorders.

Impact of Mandibular Advancement Therapy on Endothelial Function in Severe Obstructive Sleep Apnea

RATIONALE

Endothelial dysfunction, a major predictor of late cardiovascular events, is linked to the severity of obstructive sleep apnea (OSA).

OBJECTIVES

To determine whether treatment with mandibular advancement device, the main alternative to continuous positive airway pressure, improves endothelial function in patients with severe OSA.

METHODS

In this trial, we randomized patients with severe OSA and no overt cardiovascular disease to receive 2 months of treatment with either effective mandibular advancement device or a sham device. The primary outcome, change in reactive hyperemia index, a validated measurement of endothelial function, was assessed on an intention-to-treat basis. An embedded microsensor objectively measured treatment compliance.

MEASUREMENTS AND MAIN RESULTS

A total of 150 patients (86% males; mean [SD] age, 54 [10] yr; median [interquartile range] apnea-hypopnea index, 41 [35-53]; mean [SD] Epworth sleepiness scale, 9.3 [4.2]) were randomized to effective mandibular advancement device (n = 75) or sham device (n = 75). On intention-to-treat analysis, effective mandibular advancement device therapy was not associated with improvement of endothelial function compared with the sham device. Office and ambulatory blood pressure outcomes did not differ between the two groups. Effective mandibular advancement device therapy was associated with significant improvements in apnea-hypopnea index (P < 0.001); microarousal index (P = 0.008); and symptoms of snoring, fatigue, and sleepiness (P < 0.001). Mean (SD) objective compliance was 6.6 (1.4) h/night with the effective mandibular advancement device versus 5.6 (2.3) h/night with the sham device (P = 0.006).

CONCLUSIONS

In moderately sleepy patients with severe OSA, mandibular advancement therapy reduced OSA severity and related symptoms but had no effect on endothelial function and blood pressure despite high treatment compliance. Clinical trial registered with www.clinicaltrials.gov (NCT 01426607).

Association between obstructive sleep apnea severity and endothelial dysfunction in patients with type 2 diabetes

Background

Obstructive sleep apnea (OSA) and type 2 diabetes (T2D) are associated with endothelial dysfunction a main predictor of late cardiovascular (CV) events. Despite the high prevalence of OSA in patients with T2D, the impact of OSA severity on endothelial function has not been clearly elucidated. The aim of this cross-sectional study was to determine whether increasing OSA severity is associated with poorer endothelial function in patients with T2D.

Methods

140 patients with T2D and no overt CV disease underwent polysomnography, peripheral arterial tonometry, clinic blood pressure (BP) measurement, biological assessment for CV risk factors, daytime sleepiness and health related quality of life (HRQL) questionnaires. The following commonly used cut-offs for apnea-hypopnea index (AHI) were used to define 3 categories of disease severity: AHI < 15 (no OSA or mild OSA), 15 ≤ AHI < 30 (moderate OSA), and AHI ≥ 30 (severe OSA). The primary outcome was the reactive hyperemia index (RHI), a validated assessment of endothelial function.

Results

21.4% of patients had moderate OSA and 47.6% had severe OSA. Increasing OSA severity and nocturnal hypoxemia were not associated with a significant decrease in RHI. Endothelial dysfunction (RHI < 1.67) was found in 47.1, 44.4 and 39.2% of patients with no OSA or mild OSA, moderate OSA and severe OSA, respectively (p = 0.76). After adjustment for confounders including body mass index, increasing OSA severity was associated with higher systolic BP (p = 0.03), lower circulating levels of adiponectin (p = 0.0009), higher levels of sP-selectin (p = 0.03), lower scores in 3 domains of HRQL including energy/vitality (p = 0.02), role functioning (p = 0.01), and social functioning (p = 0.04).

Conclusions

Moderate to severe OSA is very common but has no impact on digital micro-vascular endothelial function in patients with T2D.

Association of diabetic vascular complications with poor sleep complaints

BACKGROUND

Literatures reported that poor sleep complaints were associated with a great deal of health outcomes. However, there are few studies on the association of poor sleep complaints with diabetic vascular complications.

METHODS

Aiming on the association, a cross-sectional survey was conducted among 1220 diabetic patients in this study. Poor sleep complaints were composed of difficulty falling asleep, early final awakening, short sleep and long sleep. The diabetic vascular complications involved in the study were diagnosed according to the Standards of Medical Care in Diabetes (ADA 2016).

RESULTS

Our findings indicated that short sleep remained independently associated with diabetic kidney disease (DKD) (OR > 1, P < 0.05) after the adjustments; long sleep independently associated with diabetic retinopathy (DR) (OR > 1, P < 0.05); early final awakening and short sleep independently associated with cardiovascular disease (OR > 1, P < 0.05); short sleep independently associated with peripheral arterial disease (OR > 1, P < 0.05); there was no association between poor sleep complaints and neuropathy (P > 0.05).

CONCLUSIONS

The study suggests that the poor sleep complaints were distinguishably associated with diabetic vascular complications. Clinicians should take poor sleep complaints into account in diabetes treatment.

The Impact of Obstructive Sleep Apnea and Tobacco Smoking on Endothelial Function

BACKGROUND

Endothelial dysfunction has been recognized to occur in the context of obstructive sleep apnea (OSA) or tobacco smoking. However, the deleterious effect on vascular function with concurrence of both conditions is largely unknown.

OBJECTIVE

To investigate whether the concurrence of OSA and smoking poses an additive detriment to endothelial dysfunction.

METHODS

Chinese men without a history of chronic medical illness were invited to complete a questionnaire including smoking pack-year exposure, polysomnography and peripheral arterial tonometry (PAT) for endothelial function. Serum 8-isoprostane, advanced oxidation protein products (AOPP) and monocyte chemo-attractant protein-1 (MCP-1) were measured.

RESULTS

114 men were successfully enrolled. PAT ratio, adjusted for age and body mass index, correlated inversely with overall severity of OSA: apnea-hypopnea index (AHI), r = -0.160 (p = 0.092); oxygen desaturation index, r = -0.214 (p = 0.024); duration of oxygen saturation <90%, r = -0.219 (p = 0.020); and minimum oxygen saturation, r = 0.250 (p = 0.008). The PAT ratio decreased with increasing pack-year group (p = 0.018). It was lower with concurrent smoking history and moderate-severe OSA (AHI ≥15/h) compared to having one or neither factor (p = 0.011). Serum levels of 8-isoprostane and AOPP were positively related to severity of OSA, while MCP-1 correlated with smoking quantity. Multiple linear regression analyses showed that severity of intermittent hypoxia, MCP-1 and pack-year exposure were independent predictors of PAT ratio.

CONCLUSION

While OSA, in particular intermittent hypoxemia, and tobacco smoking were independent risk factors, the concurrence of moderate-severe OSA and smoking was associated with the most severe impairment in endothelial function.

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.

Established vascular effects of continuous positive airway pressure therapy in patients with obstructive sleep apnoea-an update

The aim of this review was to summarize the current data from randomised controlled trials (RCTs) on vascular effects of continuous positive airway pressure (CPAP) therapy in patients with obstructive sleep apnoea (OSA). There is good evidence from RCTs that CPAP lowers blood pressure (BP) to a clinically significant amount. The effect seems to be dependent on the hours of nightly CPAP usage. Data from RCTs have also proven a beneficial effect of CPAP on measures of vascular function such as endothelial function and arterial stiffness. However, there is still a lack of evidence from RCTs proving that CPAP reduces vascular events and mortality.

Association of Fragmented QRS with Subclinical Left Ventricular Dysfunction in Patients with Obstructive Sleep Apnea

OBJECTIVE

We aimed to investigate whether fragmented QRS (fQRS) is associated with subclinical left ventricular (LV) dysfunction in patients with obstructive sleep apnea (OSA).

SUBJECTS AND METHODS

A total of 141 patients with OSA who had normal LV ejection fraction (LVEF) were included in the study. The fQRS was defined as the presence of an additional R wave, notching of R or S wave or the presence of fragmentation in 2 contiguous electrocardiography (ECG) leads. Subclinical LV dysfunction was defined as the presence of a tissue Doppler-derived Tei index of ≥ 0.5 in the absence of impaired LVEF (<50%) as assessed by transthoracic echocardiography.

RESULTS

Of the 141 patients, 71 (50.4%) had subclinical LV dysfunction. Overall, the prevalence of the fQRS was 61% (86/141). Patients with fQRS had significantly higher Tei indices than those without fQRS [median 0.66, interquartile range (IQR) 0.39 vs. median 0.40, IQR 0.15, p < 0.001]. The presence of fQRS on ECG predicted subclinical LV dysfunction in univariate logistic regression analysis [odds ratio (OR) 6.69, 95% confidence interval (CI) 3.10-14.43]. The association remained significant after adjusting for all potential confounders (OR 4.59, 95% CI 1.94-10.87).

CONCLUSION

fQRS on ECG was an independent predictor of subclinical LV dysfunction in patients with OSA. This simple tool might help to identify OSA patients who could be at risk for developing overt cardiac dysfunction.

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.