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

The impact of obesity, age, and gender on plasmatic levels of selected glycoprotein biomarkers and miRNA-499 in OSA patients

BACKGROUND

The current obstructive sleep apnea (OSA) diagnostic uses polysomnography or limited polygraphy and requires specialized personnel and technical equipment. Glycoprotein biomarkers and microRNAs are being explored as a possible new method for screening. We aimed to evaluate whether certain biomarkers and microRNA, previously identified as related to OSA, could be influenced by factors such as gender, age, and obesity level in patients with OSA.

METHODS

In this retrospective analytical study, patients with moderate to severe OSA (n = 130) were compared with the control group. Serum levels of selected biomarkers and microRNA were taken from both groups. The group of OSA patients was then stratified by gender, obesity level, and age to see the possible influence of those variables on biomarker levels.

RESULTS

Levels of all studied biomarkers - C-reactive protein (CRP), high-sensitivity troponin I (hsTnI), pentraxin-3 (PTX-3), and microRNA-499 were significantly higher in patients with OSA compared to the control group. In the OSA group only hsTnI showed a statistically significant relationship with gender. Levels of CRP and hsTnI showed a significant dependence on the level of obesity. Dependency on age was proven for hsTnI. CRP, PTX-3, and microRNA-499 did not have any statistically significant relationship with age.

CONCLUSION

We found that serum levels of pentraxin-3 and microRNA-499 in patients with moderate to severe obstructive sleep apnoea are independent of gender, obesity, and age. CRP was affected by the level of obesity and hsTnI was influenced by all 3 variables. We consider these findings important for further research of OSA biomarkers.

Increased Levels of VCAM-1 in Patients with High Cardiovascular Risk and Obstructive Sleep Apnea Syndrome

(1) Background: Although obstructive sleep apnea (OSA) is associated with increased cardiovascular morbidity, the link between OSA and cardiovascular disease (CVD) is not completely elucidated. Thus, we aim to assess cardiovascular risk (CVR) using SCORE 2 and SCORE 2 for older persons (SCORE 2OP), and to evaluate the association between the endothelial biomarkers VCAM-1, ICAM-1, epicardial fat, and sleep study parameters in order to improve current clinical practices and better understand the short-and long-term CVRs in OSA patients. (2) Methods: 80 OSA patients and 37 healthy volunteers were enrolled in the study. SCORE2 and SCORE 2 OP regional risk charts (validated algorithms to predict the 10-year risk of first-onset CVD) were used for the analysis of CVR. Two-dimensional echocardiography was performed on all patients and epicardial fat thickness was measured. VCAM-1 and ICAM-1 serum levels were assessed in all patients. (3) Results: OSA patients were classified as being at high CVR, regardless of the type of score achieved. Increased EFT was observed in the OSA group. VCAM-1 was associated with a high CVR in OSA patients, but no significant correlation was observed between adhesion molecules and epicardial fat thickness. (4) Conclusions: OSA patients have a high CVR according to the SCORE 2 and SCORE 2OP risk scores. VCAM-1 may be associated with a high CVR in OSA patients. Extending conventional risk stratification scores by adding other potential biomarkers improves the risk stratification and guide treatment eligibility for CVD prevention in the OSA population.

Investigation of serum endocan and serglycin levels in obstructive sleep apnea

BACKGROUND

Apnea-related hypoxia, hypercapnia, and blood pressure fluctuations cause production of various proinflammatory cytokines and trigger a vicious cycle that results in vascular endothelial damage and systemic inflammation in obstructive sleep apnea (OSA). Endothelial function is frequently impaired in OSA even in the absence of significant cardiac or vascular disorders.

AIMS

This study aimed to investigate the serum endocan and serglycin levels in OSA patients.

METHODS

This prospective study included 78 consecutive patients who admitted to the sleep laboratory of a tertiary referral center with the complaints of daytime sleepiness, witnessed sleep apnea, and/or snoring and who underwent all-night polysomnography (PSG). After PSG, the patients were divided into four groups in relation with their apnea-hypopnea indexes. The groups were compared for endocan and serglycin levels and their correlations with OSA severity. The correlations with demographic data and PSG findings were also investigated.

RESULTS

The OSA and the control groups had significantly different endocan and serglycin levels ([Formula: see text], for both). On univariate logistic regression analysis, it was found that serglycin and endocan levels and BMI were predictors of OSA. Multiple logistic regression analysis showed that endocan and serglycin levels were independent predictors for OSA ([Formula: see text] and [Formula: see text], respectively).

CONCLUSIONS

We have demonstrated that elevated endocan and serglycin levels are predictors for OSA. Furthermore, we have showed for the first time in literature that serglycin is correlated with OSA and is an independent predictor for OSA.

Evaluation of Blood Intercellular Adhesion Molecule-1 (ICAM-1) Level in Obstructive Sleep Apnea: A Systematic Review and Meta-Analysis

Background and objective: Intercellular adhesion molecule-1 (ICAM-1) appears to be an active and important biomarker for decreasing the risk of cardiovascular issues among individuals with obstructive sleep apnea (OSA). Herein, a systematic review and meta-analysis was designed to probe whether plasma/serum ICAM-1levels are different in adults with OSA compared to adults with no OSA, as well as adults with severe OSA compared to adults with mild/moderate OSA. Materials and methods: A thorough and systematic literature search was performed in four databases (PubMed/Medline, Web of Science, Scopus, and Cochrane Library) until 17 July 2022, without any age and sample size restrictions to retrieve the relevant articles. The standardized mean difference (SMD) along with a 95% confidence interval (CI) of plasma/serum of ICAM-1 levels was reported. Analyses, including sensitivity analysis, subgroup analysis, trial sequential analysis, meta-regression, and a funnel plot analysis, were performed in the pooled analysis. Results: A total of 414 records were identified in the databases, and 17 articles including 22 studies were entered into the meta-analysis. The pooled SMD of serum/plasma ICAM-1 levels in adults with OSA compared to controls was 2.00 (95%CI: 1.41, 2.59; p < 0.00001). The pooled SMD of serum/plasma ICAM-1 levels in adults with severe compared to mild/moderate OSA was 3.62 (95%CI: 1.74, 5.51; p = 0.0002). Higher serum/plasma ICAM-1 levels were associated with a higher mean age of controls, higher scores for the apnea-hypopnea index, and with a lower mean age of adults with OSA and with smaller sample sizes. Conclusions: Th results of the present meta-analysis showed that serum/plasma ICAM-1 levels in adults with OSA was higher than serum/plasma ICAM-1 levels in controls. Similarly, serum/plasma ICAM-1 levels in adults with severe OSA were higher compared to serum/plasma ICAM-1 levels of adults with mild or moderate OSA. Therefore, ICAM-1 may be used as an additional diagnostic and therapeutic biomarker in adults with OSA.

Sleep Apnea and Hypertension

Obstructive sleep apnea is a frequent finding in clinical practice especially with the obesity epidemic and the growing awareness of sleep-disordered breathing as a potential and treatable risk factor for cardiovascular diseases. It frequently coexists undiagnosed activating pathophysiological mechanisms known to participate in development and progression of cardiovascular diseases and resistance to therapeutical strategies. The sympathetic activation and the baroreflex and chemoreflex impairment appear to be the main pathophysiological factors that activating several mechanisms elicit cardiac and vascular damage. Data from cross-sectional population-based studies, prospective studies and meta-analysis have clearly shown the implication of OSA in the development of the hypertensive state and the benefits obtained by continuous positive airway pressure on daytime blood pressure and cardiovascular risk.

Circulating levels of cell adhesion molecules and risk of cardiovascular events in obstructive sleep apnea

Background

Obstructive sleep apnea (OSA) patients are at increased risk of cardiovascular disease (CVD). Cell adhesion molecules (CAM) are increased in OSA and CAM are also implicated in the development of CVD.

Research question

Do CAM (ICAM-1, VCAM-1 and E-selectin) have prognostic value in identifying risk of cardiovascular events in OSA?

Study design and methods

Patients with suspected OSA referred for a polysomnogram provided a fasting blood sample. Plasma levels of ICAM-1, VCAM-1 and E-selectin were determined by multiplex Luminex Assay (Milliporesigma ON, Canada). Cardiovascular events were determined by deterministic linkage to provincial health databases.

Results

418 patients were included in the analysis. Mostly male (68.2%), mean age of 50.7 yrs, median AHI 16.5 events/hour, and mean BMI of 31.7 kg/m². 36 cardiovascular events occurred in 8-yrs of follow up. Higher levels of ICAM-1 were associated with developing CVD (HR = 3.65 95% CI 1.40–9.53, 2^nd and 3rd tertiles vs. 1^st tertile), including in patients with OSA (HR = 3.1 95% CI 1.16–8.25). E-selectin was significantly associated with cardiovascular events in patients with moderate to severe OSA (HR = 3.31 95% CI 0.94–11.72, 2^nd and 3^rd tertiles vs. 1^st tertile) but not in patients without moderate to severe OSA (HR = 0.67 95% CI 0.19–2.38), p-value for interaction = 0.07.

Interpretation

In a suspected OSA cohort, patients with higher levels of ICAM-1 (>816 ng/ml) were significantly more likely to experience a cardiovascular event within 8 years after PSG. In moderate to severe OSA patients, a higher E-selectin (>36.4 ng/ml) was significantly associated with cardiovascular events.

Increased levels of VCAM-1 is associated with higher occurrence of coronary artery disease in adults with moderate to severe obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) leads to important vascular abnormalities, including the endothelial dysfunction and the production of endothelial cell adhesion molecules. The adhesion molecules play an important role in the process of endothelial dysfunction in the pathogenesis of atherosclerosis. We assess the relationship between the levels of adhesion molecules and the presence of coronary artery disease (CAD) in Chinese adults with moderate to severe OSA.

METHODS

The cross-sectional study included a total of 189 Chinese adults: 90 patients with moderate to severe OSA (apnea-hypopnea index≥15 events/h) alone, 40 patients with moderate to severe OSA and CAD, and 59 controls without OSA or with mild OSA and without CAD. We used high-throughput Multiplex Immunobead Assay technology to simultaneously test plasma levels of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1). The associations between the levels of circulating adhesion molecules and CAD in moderate to severe OSA patients were evaluated by multivariate logistic regression analysis.

RESULTS

The circulating VCAM-1 levels were significantly elevated in patients suffering from moderate to severe OSA combined CAD compared with patients having moderate to severe OSA alone [853.28 (564.26) vs. 416.61 (301.69) ng/mL, P < 0.001]. Furthermore, circulating VCAM-1 levels were independently associated with CAD (odds ration = 2.113, 95%CI 1.400-2.766, P < 0.001) and showed higher discriminatory accuracy in assessing the presence of CAD (AUC: 0.899, 95%CI 0.849-0.950, P < 0.001) in moderate to severe OSA patients. However, no significant association was found between circulating ICAM-1 levels and CAD in moderate to severe OSA patients.

CONCLUSIONS

The circulating VCAM-1 levels were significantly correlated with the presence of CAD in Chinese adults with moderate to severe OSA. The circulating VCAM-1 may function as a novel biomarker for monitoring the development and progression of CAD in patients with moderate to severe OSA.

Endothelial Dysfunction Driven by Hypoxia-The Influence of Oxygen Deficiency on NO Bioavailability

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. The initial stage of CVDs is characterized by endothelial dysfunction, defined as the limited bioavailability of nitric oxide (NO). Thus, any factors that interfere with the synthesis or metabolism of NO in endothelial cells are involved in CVD pathogenesis. It is well established that hypoxia is both the triggering factor as well as the accompanying factor in cardiovascular disease, and diminished tissue oxygen levels have been reported to influence endothelial NO bioavailability. In endothelial cells, NO is produced by endothelial nitric oxide synthase (eNOS) from L-Arg, with tetrahydrobiopterin (BH₄) as an essential cofactor. Here, we discuss the mechanisms by which hypoxia affects NO bioavailability, including regulation of eNOS expression and activity. What is particularly important is the fact that hypoxia contributes to the depletion of cofactor BH₄ and deficiency of substrate L-Arg, and thus elicits eNOS uncoupling-a state in which the enzyme produces superoxide instead of NO. eNOS uncoupling and the resulting oxidative stress is the major driver of endothelial dysfunction and atherogenesis. Moreover, hypoxia induces impairment in mitochondrial respiration and endothelial cell activation; thus, oxidative stress and inflammation, along with the hypoxic response, contribute to the development of endothelial dysfunction.

Inspiratory muscle responses to sudden airway occlusion in chronic obstructive pulmonary disease

Brief airway occlusion produces a potent reflex inhibition of inspiratory muscles that is thought to protect against aspiration. Its duration is prolonged in asthma and obstructive sleep apnea. We assessed this inhibitory reflex (IR) in chronic obstructive pulmonary disease (COPD). Reflex responses to brief (250 ms) inspiratory occlusions were measured in 18 participants with moderate to severe COPD (age 73 ± 11 yr) and 17 healthy age-matched controls (age 72 ± 6 yr). We compared the incidence and properties of the IR between groups. Median eupneic preocclusion electromyographic activity was higher in the COPD group than controls (9.4 μV vs. 5.2 μV, P = 0.001). Incidence of the short-latency IR was higher in the COPD group compared with controls (15 participants vs. 7 participants, P = 0.010). IR duration for scalenes was similar for the COPD and control groups [73 ± 37 ms (means ± SD) and 90 ± 50 ms, respectively] as was the magnitude of inhibition. IRs in the diaphragm were not detected in the controls but were present in 9 participants of the COPD group (P = 0.001). The higher incidence of the IR in the COPD group than in the age-matched controls may reflect the increased inspiratory neural drive in the COPD group. This higher drive counteracts changes in chest wall and lung mechanics. However, when present, the reflex was similar in size and duration in the two groups. The relation between the IR in COPD and swallowing function could be assessed.NEW & NOTEWORTHY A potent short-latency reflex inhibition of inspiratory muscles produced by airway occlusion was tested in people with COPD and age-matched controls. The reflex was more prevalent in COPD, presumably due to an increased neural drive to breathe. When present, the reflex was similar in duration in the two groups, longer than historical data for younger control groups. The work reveals novel differences in reflex control of inspiratory muscles due to aging as well as COPD.

Copeptin, pro-atrial natriuretic peptide and pro-adrenomedullin as markers of hypoxic stress in patients with obstructive sleep apnea-a prospective intervention study

Study Objectives

Obstructive sleep apnea (OSA) might lead to oxidative stress, inflammation and elevated circulating copeptin, proANP and proADM levels. We aimed to evaluate whether the levels of these prohormones are higher in patients with OSA and whether they might change under continuous positive airway pressure (CPAP) therapy, serving as potential proxies for the diagnosis and therapy-response in OSA.

Methods

A total of 310 patients with suspicion of OSA were recruited. Screening for OSA was performed using overnight pulse oximetry followed by polygraphy and a venous puncture in the morning. All patients diagnosed with OSA underwent CPAP adaptation. A venous puncture was conducted in the night before CPAP and in the following morning. At 1 and 6 months of treatment, polygraphy was performed, followed by a venous puncture in the morning. In the acquired blood, copeptin, proANP and proADM levels were measured.

Results

We analyzed 232 patients with OSA and 30 patients without OSA. Our results indicated that only copeptin levels differed significantly among patients with and without OSA at baseline. In OSA patients, the levels of proADM significantly changed after 1 and 6 months on CPAP therapy, when compared to baseline (p < 0.001 and p = 0.020). Additionally, proANP levels significantly decreased after 12 h on CPAP therapy, as compared to baseline levels (p < 0.001).

Conclusions

Copeptin is significantly associated with the presence of OSA. ProANP levels might serve as a potential proxy for the acute response to non-invasive ventilation (12 h), while proADM reflects the long-term response (1 and 6 months).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01704-0.

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

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

Short-term exposure to intermittent hypoxia leads to changes in gene expression seen in chronic pulmonary disease

Obstructive sleep apnea (OSA) results from episodes of airway collapse and intermittent hypoxia (IH) and is associated with a host of health complications. Although the lung is the first organ to sense changes in oxygen levels, little is known about the consequences of IH to the lung hypoxia-inducible factor-responsive pathways. We hypothesized that exposure to IH would lead to cell-specific up- and downregulation of diverse expression pathways. We identified changes in circadian and immune pathways in lungs from mice exposed to IH. Among all cell types, endothelial cells showed the most prominent transcriptional changes. Upregulated genes in myofibroblast cells were enriched for genes associated with pulmonary hypertension and included targets of several drugs currently used to treat chronic pulmonary diseases. A better understanding of the pathophysiologic mechanisms underlying diseases associated with OSA could improve our therapeutic approaches, directing therapies to the most relevant cells and molecular pathways.

The role of hyaluronic acid and hyaluronidase-1 in obstructive sleep apnoea

Biological functions of hyaluronic acid (HA) depend on its molecular size. High-molecular weight HA (HMW-HA) is an important component of the endothelial wall and has anti-inflammatory and antioxidant properties. Under inflammation or hypoxia, HMW-HA is degraded by hyaluronidases, such as HYAL-1 resulting in pro-inflammatory low-molecular weight fragments. Obstructive sleep apnoea (OSA) is characterised by intermittent hypoxia and systemic inflammation. Our aim was to evaluate circulating HMW-HA and HYAL-1 in OSA. We recruited 68 patients with OSA and 40 control volunteers. After full-night sleep study blood samples were taken for HMW-HA and HYAL-1 measurements. HYAL-1 levels were significantly higher in patients with OSA compared to controls (0.59/0.31-0.88/ng/mL vs. 0.31/0.31-0.58/ng/mL; p = 0.005) after adjustment for gender, age, BMI and smoking. There was a trend for reduced HMW-HA concentrations in OSA (31.63/18.11-59.25/ng/mL vs. 46.83/25.41-89.95/ng/mL; p = 0.068). Significant correlation was detected between circulating HMW-HA and apnoea-hypopnoea-index (r = - 0.195, p = 0.043), HYAL-1 and apnoea-hypopnoea-index (r = 0.30, p < 0.01) as well as oxygen desaturation index (r = 0.26, p < 0.01). Our results suggest that chronic hypoxia is associated with increased plasma HYAL-1 concentration and accelerated HMW-HA degradation. Altered hyaluronan metabolism may be involved in the inflammatory cascade potentially leading to endothelial dysfunction in OSA.

Obstructive Sleep Apnea Severity, Body Mass Index, and Circulating Levels of Cellular Adhesion Molecules

PURPOSE

To investigate the relationship between obstructive sleep apnea (OSA) severity, body mass index (BMI), and circulating levels of inflammatory adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin).

METHODS

A cross-sectional clinical cohort study on all consecutive adults referred to the University of British Columbia (UBC) Sleep Laboratory for a polysomnogram (PSG) for suspected OSA provided a morning blood sample. Samples were analyzed with multiplex immune assay (MilliporeSigma, CA) to assess the levels of adhesion molecules.

RESULTS

488 patients were studied; the majority were male (68%) with a mean age of 50 yrs, mean AHI of 23 events/hour, and mean BMI of 32 kg/m². In multivariable linear regression models, all three adhesion molecules were significantly associated with BMI (E-selectin p < 0.0001; ICAM-1 p = 0.0007; VCAM-1 p = 0.0003). However, only E-selectin was independently associated with AHI (p = 0.02); there was no significant interaction between AHI and BMI for E-selectin (p = 0.33).

CONCLUSIONS

Although all three adhesion molecules were associated with BMI, only E-selectin was independently associated with OSA severity. Future studies are needed to determine the clinical significance of the relationship between E-selectin and OSA.

The impact of OSA and CPAP treatment on cell adhesion molecules' night-morning variation

PURPOSE

Obstructive sleep apnea (OSA) has been related to vascular inflammation and production of endothelial cell adhesion molecules (CAMs). We aimed to determine night-morning variation of CAMs in patients with OSA compared to controls and the effect of one-night continuous positive airway pressure (CPAP) treatment on them.

METHODS

Nonsmoking men went through a full-attended polysomnography (PSG) study. Participants with moderate to severe OSA went through another PSG study while being treated with CPAP. Participants who did not have OSA composed the control group. Serum levels of intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and E-selectin were measured before and after sleep on both nights.

RESULTS

Of 30 men, 20 had moderate to severe OSA while 10 did not. Night and morning ICAM-1 levels of patients with OSA were significantly higher than controls (p = 0.002 and p < 0.0001 respectively), while both night and morning VCAM-1 and E-selectin levels were not. Morning ICAM-1 levels of controls were significantly lower than night levels (p = 0.031), while morning ICAM-1, VCAM-1, and E-selectin levels of patients with OSA and morning VCAM-1 and E-selectin levels of controls were not. After CPAP treatment, the morning ICAM-1 levels, but not VCAM-1 levels, of patients with OSA were significantly lower than night levels (p = 0.006) and E-selectin levels showed a tendency for reduction (p = 0.06).

CONCLUSIONS

OSA is associated with elevated night and morning ICAM-1 levels in adult men with OSA. Even one night of CPAP treatment restores the normal night-morning variation of ICAM-1 levels and may have an effect on E-selectin levels, as well.

Association between Upper-airway Surgery and Ameliorative Risk Markers of Endothelial Function in Obstructive Sleep Apnea

The objective of our study was to evaluate the effects of upper-airway surgery on improvement of endothelial function-related markers in patients with obstructive sleep apnea (OSA). Subjects with moderate to severe OSA who underwent upper-airway surgery, with a follow-up duration of at least 6 months, were included. Pre- and postoperative polysomnographic variables and endothelial function-related markers were compared. Subgroup and correlation analyses were conducted to find possible indicators for better endothelial function-related markers after upper-airway surgery. In total, 44 patients with OSA were included. The mean follow-up duration was 1.72 ± 0.92 years. Serum VEGFA [-20.29 (CI: -35.27, -5.31), p < 0.05], Ang2 [-0.06 (CI: -0.16, 0.03), p < 0.05], E-selectin [-7.21 (CI: -11.01, -3.41), p < 0.001], VWF [-58.83 (CI: -103.93, -13.73), p < 0.05], VWFCP [-33.52 (CI: -66.34, -0.70), p < 0.05], and TM [-0.06 (CI: -0.09, -0.03), p < 0.05] were significantly lower after upper-airway surgery. However, other risk markers of endothelial function, such as Ang1, ICAM1, VEGFR1, and VCAM, did not change significantly. Correlations between improved endothelial function-related markers and ameliorated oxyhemoglobin saturation and glucolipid metabolism were established. Upper-airway surgery might be associated with an improvement in endothelial function in patients with OSA. These changes may be associated with improved oxygen saturation after upper-airway surgery.

The impact of obstructive sleep apnea and PAP therapy on all-cause and cardiovascular mortality based on age and gender - a literature review

BACKGROUND

Obstructive sleep apnea (OSA) is a common sleep disorder which negatively impacts different body systems, especially the cardiovascular system. The correlation between sleep related breathing disorders and cardiovascular diseases has been well studied. However, the impact of OSA on cardiovascular related mortality and the role of positive airway pressure therapy in decreasing mortality is unclear. We reviewed studies investigating the impact of OSA on all-cause and cardiovascular related mortality in both genders, and in different age groups.

METHODS

A literature search (PubMed) using two phrases "obstructive sleep apnea and co-morbidities in males and females" and "obstructive sleep apnea and co-morbidities by age" yielded a total of 214 articles. Nineteen articles met the inclusion criteria.

RESULTS

The studies reviewed showed conflicting results. Some showed that OSA increases all cause and cardiovascular related mortality predominantly in the middle-aged group (40-65) followed by a plateau or a reduction in mortality. Other studies showed a positive linear correlation between OSA and mortality up to the age of 80. The same controversy was noted for gender; some studies did not observe an increase in mortality in females with OSA, while others observed a trend for an increase in mortality in females.

CONCLUSION

There is a debate in the literature regarding the impact of OSA on all-cause and cardiovascular mortality in both genders and in different age groups. However, the variation in results might be related to different study designs and significant epidemiological prevalence of OSA in males and females.

Metabolic Consequences of Obstructive Sleep Apnea Especially Pertaining to Diabetes Mellitus and Insulin Sensitivity

Obstructive sleep apnea (OSA) and diabetes has been known to be closely related to each other and both diseases impact highly on the public health. There are many evidence of reports that OSA is associated with diabetes with a bidirectional correlation. A possible causal mechanism of OSA to diabetes is intermittent hypoxemia and diabetes to OSA is microvascular complication. However, OSA and diabetes have a high prevalence rate in public and shares the common overlap characteristic and risk factors such as age, obesity, and metabolic syndrome that make it difficult to establish the exact pathophysiologic mechanism between them. In addition, studies demonstrating that treatment of OSA may help prevent diabetes or improve glycemic control have not shown convincing result but have become a great field of interest research. This review outlines the bidirectional correlation between OSA and diabetes and explore the pathophysiologic mechanisms by approaching their basic etiologies.

Evaluating the clinical value of the hypoxia burden index in patients with obstructive sleep apnea

PURPOSE

We aimed to develop a novel index, the hypoxia burden index (HBI), that reflects the degree and duration of oxygen desaturation, and to determine whether this index is better than the apnea hypopnea-index (AHI) for evaluating obstructive sleep apnea (OSA) and cardiovascular diseases morbidities.

METHODS

We retrospectively analyzed 459 adult subjects who underwent overnight polysomnography (PSG) in this study. The HBI was calculated by dividing the total desaturation area of SpO₂ below 90% by the TST measured in seconds. Correlations between the HBI and PSG parameters and the cardiovascular diseases (CVDs) of inpatients were explored.

RESULTS

For the 459 participants, the HBI was highly correlated with the AHI (r = 0.690), lowest oxygen saturation (SpO₂min) (r = -0.733), and proportion of cumulative sleep time with SpO₂ below 90% in total sleep time (TST) (CT90%) (r = 0.801). The HBI was mildly correlated with Epworth sleepiness scale score, morning systolic blood pressure, diastolic blood pressure, and mean arterial pressure. Among the significantly different parameters in the CVD and non-CVD groups in 202 inpatients (age, sex, the longest time of apnea, AHI, and HBI), only age, sex, and HBI [OR 1.006 (1.001-1.011), p = 0.021] were independently correlated with CVDs.

CONCLUSIONS

The HBI considers both hypoxia duration and severity during sleep. It may have potential value in predicting the clinical outcomes of OSA based on its correlation with ESS scores and morning blood pressure as well as its independent association with the prevalence of CVDs, whereas the AHI is not significantly associated with CVD prevalence.

Biomarkers of carcinogenesis and tumour growth in patients with cutaneous melanoma and obstructive sleep apnoea

The goal of this study was to assess the relationship between the severity of obstructive sleep apnoea (OSA) and the levels of carcinogenesis- and tumour growth-related biomarkers in patients with cutaneous melanoma.This multicentre observational study included patients who were newly diagnosed with melanoma. The patients were classified as non-OSA (apnoea-hypopnoea index (AHI) 0-5 events·h^-1), mild OSA (AHI 5-15 events·h^-1) and moderate-severe OSA (AHI >15 events·h^-1). ELISAs were performed to analyse the serum levels of hypoxia- and tumour adhesion-related biomarkers (vascular endothelial growth factor (VEGF), interleukin (IL)-8, intracellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM)-1) and markers of tumour aggressiveness (S100 calcium-binding protein B (S100B) and melanoma inhibitory activity (MIA)). A logistic model adjusted for age, sex and body mass index was fitted to each biomarker, and the AHI served as the dependent variable.360 patients were included (52.2% male, median (interquartile range) age 55.5 (43.8-68.0) years and AHI 8.55 (2.8-19.5) events·h^-1). The levels of VEGF, IL-8, ICAM-1, S100B and MIA were not related to the severity of OSA. The levels of VCAM-1 were higher in patients with OSA than those without OSA (mild OSA: odds ratio (OR) 2.07, p=0.021; moderate-severe OSA: OR 2.35, p=0.013).In patients with cutaneous melanoma, OSA was associated with elevated circulating levels of VCAM-1 that could indicate the contribution of OSA in tumorigenesis via integrin-based adhesion.

Serum heparanase levels are associated with endothelial dysfunction in patients with obstructive sleep apnea

BACKGROUND AND AIM

Obstructive sleep apnea syndrome (OSAS) is well-known to be associated with high risk for cardiovascular (CV) diseases. Heparanase has been recently shown to be related to increased inflammation and vulnerability of the atherosclerotic plaques. Herein we aimed to investigate the relationships between OSAS, heparanase and endothelial dysfunction.

MATERIALS AND METHODS

A total of 120 patients with varying severity of OSAS and 31 controls without OSAS were enrolled. Flow-mediated dilatation (FMD) was measured as an indicator of endothelial dysfunction. Serum heparanase levels were measured with ELISA.

RESULTS

Serum heparanase levels increased in a stepwise fashion from controls to patients with more severe OSAS. When FMD was compared with controls and various degrees of severity of OSAS, a stepwise decrease in FMD was observed. Serum heparanase levels were found to be significantly associated with apnea hypopnea index (AHI) (r = .57, P < .001) and FMD (r= -.37, P < .001) in patients with OSAS. Serum heparanase levels were significantly associated with hemoglobin-A1c and body mass index in patients with OSAS. Serum heparanase and uric acid levels were independent predictors of FMD in linear regression analysis (R²  = .506, P < .001; P < .001 and P = .001 respectively).

CONCLUSIONS

Serum heparanase levels were significantly increased in patients with OSAS and associated with the severity of OSAS (AHI) and endothelial dysfunction (FMD). Increased heparanase activity in OSAS may be related to increased cardiovascular risk in patients with OSAS.

Serum of obstructive sleep apnea patients impairs human coronary endothelial cell migration

INTRODUCTION

Endothelial cell migration and proliferation play an important role in the growth and development of new blood vessels and endothelium healing. This process occurs in response to injury, inflammation and immune reactions. Dysfunction of the endothelium may play a significant role in development and progression of cardiovascular disease related to sleep-disordered breathing. The aim of our study was to evaluate the chemo-attractant activity of serum from obstructive sleep apnea (OSA) and normal subjects on coronary artery endothelial cell migration.

MATERIAL AND METHODS

We studied 12 severe OSA patients, free of other co-morbidities and on no treatment, along with 12 age-, body mass index, and gender matched healthy controls. Blood was collected at three time points: at 21:00 before sleep, at 6:00 after waking from sleep, and at 11:00 (after 5 h of normal daytime activity). Serum chemo-attractant activity for human coronary endothelial cells was assessed using a colorimetric cell migration assay kit.

RESULTS

In healthy subjects, serum chemo-attractant activity peaked in the morning after waking from sleep (p = 0.02). This early morning increase was blunted in severe OSA subjects, in whom chemo-attractant activity was weaker than in normal controls (p = 0.02), and did not change significantly at the different time-points (p < 0.001 vs. controls).

CONCLUSIONS

Chemo-attractant activity of the serum from OSA patients is lower compared to serum from healthy subjects, especially in the morning. Altered chemo-attractant serum activity may conceivably contribute to the impairment of endothelial function in obstructive sleep apnea patients.

Zinc Is Indispensable in Exercise-Induced Cardioprotection against Intermittent Hypoxia-Induced Left Ventricular Function Impairment in Rats

In obstructive sleep apnea (OSA), recurrent obstruction of the upper airway leads to intermittent hypoxia (IH) during sleep, which can result in impairment of cardiac function. Although exercise can have beneficial effects against IH-induced cardiac dysfunction, the mechanism remains unclear. This study aimed to investigate the interactions of zinc and exercise on IH-triggered left ventricular dysfunction in a rat model that mimics IH in OSA patients. Nine-week-old male Sprague-Dawley rats were randomly assigned to either a control group (CON) or to a group receiving 10 weeks of exercise training (EXE). During weeks 9 and 10, half the rats in each group were subjected to IH for 8 h per day for 14 days (IHCON, IHEXE), whereas the remainder continued to breathe room air. Rats within each of the CON, IHCON, EXE, and IHEXE groups were further randomly assigned to receive intraperitoneal injections of either zinc chloride, the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), or injection vehicle only. IH induced a lower left ventricular fractional shortening, reduced ejection fraction, higher myocardial levels of inflammatory factors, increased levels oxidative stress, and lower levels of antioxidative capacity, all of which were abolished by zinc treatment. IHEXE rats exhibited higher levels of cardiac function and antioxidant capacity and lower levels of inflammatory factors and oxidative stress than IHCON rats; however, IHEXE rats receiving TPEN did not exhibit these better outcomes. In conclusion, zinc is required for protecting against IH-induced LV functional impairment and likely plays a critical role in exercise-induced cardioprotection by exerting a dual antioxidant and anti-inflammatory effect.

Serum from obstructive sleep apnea patients induces inflammatory responses in coronary artery endothelial cells

BACKGROUND AND AIMS

Obstructive sleep apnea (OSA) is characterized by intermittent airway obstruction and systemic hypoxia during sleep, which can contribute to an increase in reactive oxygen species, vascular remodeling, vasoconstriction and ultimately cardiovascular disease. Continuous positive airway pressure (CPAP) is a clinical therapy that maintains airway patency and mitigates several symptoms of OSA. However, it is currently unknown whether CPAP therapy also reduces the overall inflammatory potential in the circulation; to address this in an unbiased manner, we applied a novel endothelial biosensor approach, the serum cumulative inflammatory potential (SCIP) assay.

METHODS

We studied healthy controls (n = 7), OSA subjects receiving no treatment, (OSA controls) (n = 7) and OSA subjects receiving CPAP for 3 months (n = 8). Serum was obtained from OSA subjects before and after CPAP or no treatment. A battery of quantitative and functional assays was performed to assess the serum inflammatory potential, in terms of endothelial responses. For the SCIP assay, human coronary artery endothelial cells (hCAECs) were incubated with 5% serum in media from individual subjects for 4 h. qPCR was performed to assess endothelial inflammatory transcript (ICAM-1, VCAM-1, IL-8, P-selectin, CCL5, and CXCL12) responses to serum. Additionally, transendothelial resistance was measured in serum-incubated hCAECs following leukocyte challenge.

RESULTS

hCAECs exhibited significant increases in VCAM-1, ICAM-1, IL-8 and P-selectin mRNA when incubated with serum from OSA patients compared to serum from healthy control subjects. Furthermore, compared to no treatment, serum from CPAP-treated individuals was less potent at inducing inflammatory gene expression in the SCIP assay. Similarly, in a leukocyte adhesion assay, naïve cells treated with serum from patients who received CPAP exhibited improved endothelial barrier function than cells treated with OSA control serum.

CONCLUSIONS

OSA results in greater serum inflammatory potential, thereby driving endothelial activation and dysfunction.

Hippocampal mitogen-activated protein kinase activation is associated with intermittent hypoxia in a rat model of obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS), characterized by intermittent hypoxia/re-oxygenation, may impair the cerebral system. Although mitogen-activated protein kinase (MAPK) signaling was observed to have a key role in hypoxia-induced brain injury, the intracellular events and their underlying mechanisms for intermittent hypoxia/re-oxygenation-associated damage to hippocamal MAPKs, including extracellular signal-regulated kinase (ERK)1/2, P38MAPK and c-Jun N-terminal kinase (JNK) remain to be elucidated and require further investigation. A total of five rats in each sub-group were exposed to intermittent hypoxia or continued hypoxia for 2, 4, 6 or 8 weeks. Histological, immunohistochemical and biological analyses were performed to assess nerve cell injury in the hippocampus. Surviving CA1 pyramidal cells were identified by hematoxylin and eosin staining. The levels of phosphorylated ERK1/2, P38MAPK and JNK were detected by western blotting. B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) in neural cells were examined by immunohistochemistry. The malondialdehyde (MDA) contents and superoxide dismutase (SOD) activities were measured by thiobarbituric acid and xanthine oxidation methods, respectively. Under continued hypoxia, the levels of phospho-ERK1/2 peaked at the fourth week and then declined, whereas phospho-P38MAPK and JNK were detected only in the late stages. By contrast, under intermittent hypoxia, ERK1/2, P38MAPK and JNK were activated at all time-points assessed (2, 4, 6 and 8 weeks). The levels of phospho-ERK1/2, P38MAPK and JNK were all higher in the intermittent hypoxia groups than those in the corresponding continued hypoxia groups. Bcl-2 was mainly increased and reached the highest level at six weeks in the continued hypoxia group. Of note, Bcl-2 rapidly increased to the peak level at four weeks, followed by a decrease to the lowest level at the eighth week in the intermittent hypoxia group. Bax was generally increased at the late stages under continued hypoxia, but increased at all time-points under the intermittent hypoxia conditions. The two types of hypoxia induced an increase in the MDA content, but a decrease in SOD activity. Marked changes in these two parameters coupled with markedly reduced surviving cells in the hippocampus in a time-dependent manner were observed in the intermittent hypoxia group in comparison with the continued hypoxia group. OSAS-induced intermittent hypoxia markedly activated the MAPK signaling pathways, which were triggered by oxidative stress, leading to abnormal expression of downstream Bcl-2 and Bax, and a severe loss of neural cells in the hippocampus.

Inflammation induced by increased frequency of intermittent hypoxia is attenuated by tempol administration

The levels of serum inflammatory cytokines and the activation of nuclear factor kappa B (NF-κB) and hypoxia inducible factor-1α (HIF-1α) in heart tissues in response to different frequencies of intermittent hypoxia (IH) and the antioxidant tempol were evaluated. Wistar rats (64 males, 200-220 g) were randomly divided into 6 experimental groups and 2 control groups. Four groups were exposed to IH 10, 20, 30, or 40 times/h. The other 2 experimental groups were challenged with IH (30 times/h) plus tempol, either beginning on day 0 (IH30T0) or on day 29 (IH30T29). After 6 weeks of challenge, serum levels of tumor necrosis factor (TNF)-α, intracellular adhesion molecule (ICAM)-1, and interleukin-10 were measured, and western blot analysis was used to detect NF-κB p65 and HIF-1α in myocardial tissues. Serum levels of TNF-α and ICAM-1 and myocardial expression of NF-κB p65 and HIF-1α were all significantly higher in IH rats than in controls (P<0.001). Increased IH frequency resulted in more significant changes. Administration of tempol in IH rats significantly reduced levels of TNF-α, ICAM-1, NF-κB and HIF-1α compared with the non-tempol-treated group (F=16.936, P<0.001). IH induced an inflammatory response in a frequency-dependent manner. Additionally, HIF-1α and NF-κB were increased following IH administration. Importantly, tempol treatment attenuated this effect.

Insulin resistance, glucose intolerance and diabetes mellitus in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is a highly prevalent disorder, which conveys an increased risk of cardiovascular disease and death. Type 2 diabetes mellitus (T2DM), glucose intolerance and insulin resistance (IR) are common in subjects with OSA, but a shared intimate relationship with obesity makes discerning an independent link challenging. Nonetheless, mechanistic studies suggest that OSA could contribute to impaired glucose metabolism via the effects of sleep fragmentation, sympathetic excitation and intermittent hypoxia (IH) on pancreatic B-cell function, insulin sensitivity, and systemic inflammation. In particular, emerging data suggest that IH may have an important detrimental effect on adipose tissue function and inflammation. Similarly, data from population-and clinic-level studies suggest that OSA is independently related with the prevalence and incidence of T2DM and IR, and may also lead to worse glycaemic control in diabetics. However, the ability of continuous positive airway pressure (CPAP) therapy to make a meaningful impact on T2DM or IR remains uncertain. In this review we explore the available evidence linking OSA with IR, glucose intolerance and T2DM, and discuss potential pathobiological mechanisms by which sleep disordered breathing can affect metabolic health.

Excessive daytime sleepiness is associated with changes in salivary inflammatory genes transcripts

Excessive daytime sleepiness (EDS) is a ubiquitous problem that affects public health and safety. A test that can reliably identify individuals that suffer from EDS is needed. In contrast to other methods, salivary biomarkers are an objective, inexpensive, and noninvasive method to identify individuals with inadequate sleep. Although we have previously shown that inflammatory genes are elevated in saliva samples taken from sleep deprived individuals, it is unclear if inflammatory genes will be elevated in clinical populations with EDS. In this study, salivary samples from individuals with sleep apnea were evaluated using the Taqman low density inflammation array. Transcript levels for 3 genes, including prostaglandin-endoperoxide synthase 2 (PTGS2), were elevated in patients with sleep apnea. Interestingly, PTGS2 was also elevated in patients with EDS but who did not have sleep apnea. These data demonstrate the feasibility of using salivary transcript levels to identify individuals that self-report excessive daytime sleepiness.

Biomarkers to improve diagnosis and monitoring of obstructive sleep apnea syndrome: current status and future perspectives

Obstructive sleep apnea syndrome (OSAS) is characterized by recurrent episodes of upper airway collapse associated with oxygen desaturation and sleep disruption. It is proposed that these periodic changes lead to molecular variations that can be detected by assessing serum biomarkers. Studies have identified inflammatory, oxidative, and metabolic perturbations attributable to sleep-disordered breathing. Given that OSAS is associated with increased cardiovascular and cerebrovascular morbidity, the ideal biomarker should enable timely recognition with the possibility of intervention. There is accumulating data on the utility of serum biomarkers for the evaluation of disease severity, prognosis, and response to treatment. However, current knowledge is limited by data collection techniques, disease complexity, and potential confounding factors. The current paper reviews the literature on the use of serum biomarkers in OSAS. It is concluded that the ideal serum biomarker still needs to be discovered, while caution is needed in the interpretation of hitherto available results.

Coronary endothelial function in patients with obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) has been associated with increased risk for cardiovascular events, possibly mediated by endothelial dysfunction. The current study evaluates the association between invasive coronary endothelial dysfunction and OSA in patients with nonobstructive coronary atherosclerosis.

METHODS

All patients who had undergone both polysomnography and an invasive coronary vasomotor study at the Mayo Clinic, Rochester, Minnesota, from January 1997 to August 2011 were identified (n=143). OSA was defined as an apnea-hypopnea index of 5 or higher. Three endpoints of coronary endothelial function - percentage change in coronary artery diameter at the mid and distal left anterior descending artery to intracoronary acetylcholine and percentage change in coronary blood flow to intracoronary acetylcholine - were assessed. Differences between patients with OSA (n=102) and those without OSA (n=41) were evaluated using multivariate analysis of variance. Follow-up mortality data were collected and Kaplan-Meier curves were plotted to evaluate differences in mortality between patients with and without OSA.

RESULTS

Patients with OSA were more likely to have hypertension compared with patients without OSA. OSA was not significantly associated with coronary endothelial dysfunction on univariate analysis (P=0.23) and after adjustment for hypertension (P=0.19). Similarly, there was no significant difference in coronary endothelial function in patients who had oxygen desaturation of less than 90% during polysomnography (P=0.42). There was a trend toward higher mortality in patients with OSA compared with those without OSA, but this did not reach statistical significance (5 vs. 0% at 10 years, P=0.25).

CONCLUSION

The current study suggests that OSA is not an independent risk factor for coronary endothelial dysfunction in patients with early coronary atherosclerosis. Adverse coronary outcomes in patients with OSA may be independent of coronary endothelial dysfunction.

Adhesion molecule increases in sleep apnea: beneficial effect of positive airway pressure and moderation by obesity

BACKGROUND

Elevated levels of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) may contribute to cardiovascular disease and are associated with obstructive sleep apnea (OSA) and obesity. The relationship between OSA and obesity in determining ICAM-1 and VCAM-1 levels, and the effect of treatment, is unclear.

OBJECTIVE

Our aim was to study whether positive airway pressure (PAP) usage resulted in changes in ICAM-1 and VCAM-1 after 2 years within 309 OSA patients from the Icelandic Sleep Apnea Cohort, and determine how obesity affected such changes.

SUBJECTS/METHODS

The mean body mass index (BMI) was 32.4±5.1 kg m(-2); subjects had moderate-to-severe OSA (apnea-hypopnea index=45.0±20.2) and 79% were male. There were 177 full PAP users (⩾4 h per night and ⩾20 of last 28 nights), 44 partial (<4 h per night or <20 nights) and 88 nonusers.

RESULTS

ICAM-1 (P<0.001) and VCAM-1 (P=0.012) change was significantly different among the PAP groups. The largest ICAM-1 differences were among the most obese subjects (P<0.001). At follow-up, nonusers had increased ICAM-1 compared with decreased levels in full users. All groups had increased VCAM-1, but nonusers had a significantly larger increase than full users.

CONCLUSIONS

Within moderate-to-severe OSA patients, PAP usage prevents increases in adhesion molecules observed in nonusers after 2 years. For ICAM-1, the largest effect is in the most obese subjects. As OSA and obesity commonly coexist, the usage of PAP to limit increases in adhesion molecules may decrease the rate of progression of OSA-related cardiovascular disease.

Renal vasodilating capacity and endothelial function are impaired in patients with obstructive sleep apnea syndrome and no traditional cardiovascular risk factors

OBJECTIVE

Patients with obstructive sleep apnea syndrome exhibit accelerated vascular aging and renal damage. Aim of the study was to investigate whether vascular dysfunction is a feature of obstructive sleep apnea syndrome per se or instead related to the presence of traditional cardiovascular risk factors.

METHODS

Forty patients with moderate-severe obstructive sleep apnea syndrome (20 with, 20 without traditional risk factors) and 20 matched healthy controls were enrolled. Renal vasodilating capacity, endothelium-dependent vasodilation in the brachial artery, carotid-femoral pulse wave velocity and carotid stiffness were measured. Oxidative stress, endothelial biomarkers and leukocyte adhesion molecule levels were also evaluated.

RESULTS

Apneic patients without traditional cardiovascular risk factors presented reduced endothelium-dependent vasodilation (3.7±2.1 versus 6.1±3.0%, P<0.05), increased serum E-selectin (49.8±11.5 versus 38.9±17.9 ng/ml, P<0.05), and impaired renal vasodilating capacity (6.0±4.3 versus 10.4±6.1%, P<0.05), as compared to healthy controls. Endothelial NO synthase expression was reduced (0.0133 versus 0.0221×10 copies/μg RNA, P<0.05), whereas oxidative stress parameters and leukocyte adhesion molecules were similar to controls. Patients with obstructive sleep apnea syndrome and traditional risk factors also exhibit increased aortic and carotid stiffness, increased renal resistive index and intima-media thickness, and reduced expression of the endothelial progenitor cell marker CD34: however, these parameters were similar to those of healthy controls in patients with isolated obstructive sleep apnea syndrome.

CONCLUSION

Obstructive sleep apnea syndrome is characterized by endothelial dysfunction and activation and impaired renal vasodilating capacity even in the absence of traditional cardiovascular risk factors, possibly due to reduced endothelial NO synthase expression.

Obstructive sleep apnea syndrome, vascular pathology, endothelial function and endothelial cells and circulating microparticles

Accelerated atherosclerosis and increased cardiovascular risk are frequently reported in patients with obstructive sleep apnea (OSA) syndrome. In this article the authors attempt a review of the current understanding of the relationship between vascular risk and OSA syndrome based on large cohort studies that related the disease to several cardiovascular risk factors and vascular pathologies. We also discuss the pathophysiological mechanisms that may be involved in this relationship, starting with endothelial dysfunction and its mediators. These include an increased oxidative stress and inflammation as well as several disorders of coagulation and lipid metabolism. Moreover, circulating microparticles from activated leukocytes (CD62L_MPs) are higher in patients with OSA and there is a positive correlation between circulating levels of CD62L_MPs and nocturnal hypoxemia severity. Finally, circulating level of endothelial microparticles and circulating endothelial cells seem to be increased in patients with OSA. Also, endothelial progenitor cells are reduced and plasma levels of the vascular endothelial growth factor are increased.

Cardiac asthma: new insights into an old disease

Cardiac asthma has been defined as wheezing, coughing and orthopnea due to congestive heart failure. The clinical distinction between bronchial asthma and cardiac asthma can be straight forward, except in patients with chronic lung disease coexisting with left heart disease. Pulmonary edema and pulmonary vascular congestion have been thought to be the primary causes of cardiac asthma but most patients have a poor response to diuretics. There appears to be limited effectiveness of classical asthma medications like bronchodilators or corticosteroids in treating cardiac asthma. Evidence suggests that circulating inflammatory factors and tissue growth factors also lead to airway obstruction suggesting the possibility of developing novel therapies.

Vascular inflammation and sleep disordered breathing in a community-based cohort

STUDY OBJECTIVES

Sleep disordered breathing is associated with cardiovascular disease. The pathophysiologic mechanisms remain unclear, but enhanced vascular inflammation is implicated. We sought to evaluate the association of sleep disordered breathing with biomarkers of inflammation.

DESIGN

Cross-sectional, observational.

SETTING

Community-based.

PARTICIPANTS

There were 900 participants from the Framingham Heart Study site of the Sleep Heart Health Study (52% females, mean age 60 y, 23% ethnic minorities).

INTERVENTIONS

None.

MEASUREMENTS

We assessed circulating levels of nine inflammatory biomarkers in relation to polysomnographically-derived apnea-hypopnea index and hypoxemia index (% sleep time with oxyhemoglobin saturation < 90%). Multivariable models were adjusted for demographics, smoking, cardiovascular diseases, diabetes, and other potential confounders, without and with adjustment for body mass index.

RESULTS

With multivariable adjustment not including body mass index, the apnea-hypopnea index was associated with C-reactive protein, inter-leukin-6, fibrinogen, intercellular adhesion molecule-1, and P-selectin levels and hypoxemia index was associated with C-reactive protein, interleukin-6, and fibrinogen levels. After adjustment for body mass index, only the association of interleukin-6 with sleep disordered breathing remained significant: the adjusted mean serum interleukin-6 level was 2.93, 3.14, 3.34, and 4.62 pg/mL, respectively, in participants with apnea-hypopnea index < 5, 5-14.9, 15-29.9, and ≥ 30 events/h (P = 0.01 for trend) and 2.97, 3.01, 3.35, and 4.85 pg/mL, respectively, in participants with hypoxemia index < 0.5, 0.5-4.9, 5-9.9, and ≥ 10% of sleep time (P = 0.02 for trend).

CONCLUSIONS

In a community-based sample, sleep disordered breathing is associated with higher levels of interleukin-6, a marker of myocardial infarction risk and mortality. Adiposity may mediate the increased levels of C-reactive protein, fibrinogen, intercellular adhesion molecule-1, and P-selectin observed in sleep disordered breathing.

Circulating adhesion molecules in obstructive sleep apnea and cardiovascular disease

Over 20 years of evidence indicates a strong association between obstructive sleep apnea (OSA) and cardiovascular disease. Although inflammatory processes have been heavily implicated as an important link between the two, the mechanism for this has not been conclusively established. Atherosclerosis may be one of the mechanisms linking OSA to cardiovascular morbidity. This review addresses the role of circulating adhesion molecules in patients with OSA, and how these may be part of the link between cardiovascular disease and OSA. There is evidence for the role of adhesion molecules in cardiovascular disease risk. Some studies, albeit with small sample sizes, also show higher levels of adhesion molecules in patients with OSA compared to controls. There are also studies that show that levels of adhesion molecules diminish with continuous positive airway pressure therapy. Limitations of these studies include small sample sizes, cross-sectional sampling, and inconsistent control for confounding variables known to influence adhesion molecule levels. There are potential novel therapies to reduce circulating adhesion molecules in patients with OSA to diminish cardiovascular disease. Understanding the role of cell adhesion molecules generated in OSA will help elucidate one mechanistic link to cardiovascular disease in patients with OSA.

Plasma selectins in patients with obstructive sleep apnea

Obstructive sleep apnea (OSA) is an independent risk factor in the pathogenesis of -cardiovascular diseases. The aim of the study was to analyze three specific adhesion molecules involved in the development of an atherosclerotic plaque: E-selectin (endothelium), L-selectin (leukocyte surface), and P-selectin (from platelet), circulating in plasma in patients at different OSA severity. Eighty non-smoking male Caucasians aged 30-64 were enrolled into the study after clinical, biochemical, and polysomnographic examinations. The patients were divided into four groups based on the results of apnea/hypopnea index (AHI): OSA-0 with AHI 0-4.9 (n = 20), OSA-1 with AHI 5-15 (n = 21), OSA-2 with AHI 16-30 (n = 18), OSA-3 with AHI ≥ 31 (n = 21). Complete blood count, oral glucose tolerance test, fasting lipid profile, C-reactive protein and insulin, and plasma concentrations of soluble E-selectin, P-selectin and L-selectin were measured. We found a progressive increase in the concentrations of all three selectins with the severity of OSA. In conclusion, the level of plasma adhesion molecules may be indicative of OSA severity and may contribute to cardiovascular sequelae.

Obstructive sleep apnea and stroke

Obstructive sleep apnea (OSA) is a common disorder that has been associated with many cardiovascular disease processes, including hypertension and arrhythmias. OSA has also been identified as an independent risk factor for stroke and all-cause mortality. OSA is highly prevalent in patients with transient ischemic attacks and stroke. Routinely screening patients with transient ischemic attacks or stroke for sleep apnea is becoming more common. In stroke patients with OSA, treatment with continuous positive airway pressure may prevent subsequent cardiovascular events and improve neurologic outcomes. This review explores the pathophysiology of the association between OSA and stroke, and the clinical implications of identification and treatment of OSA in patients with stroke.