C-reactive protein evolution in obstructive sleep apnoea patients under CPAP therapy

Effects of oral appliance treatment on inflammatory biomarkers in obstructive sleep apnea: A randomised controlled trial

Obstructive sleep apnea (OSA) may lead to increased circulating concentrations of inflammatory biomarkers and treatment may change these. We aimed to assess the effect of oral appliance (OA) therapy on inflammatory biomarkers in a randomised controlled pilot trial. A total of 71 patients with OSA and systemic hypertension were randomly allocated to an active, mandible protruded (OAa) or a passive, mandible non‐protruded device (OAp) treatment. Serum concentrations of the inflammatory biomarkers white blood cells, high‐sensitivity C‐reactive protein, interleukin 6, interleukin 10, and tumour necrosis factor‐α were measured at baseline and after 3 months of OA treatment. The differences between treatment groups in biomarker concentration change during the treatment were presented as the Vargha and Delaney effect size and evaluated with the Wilcoxon–Mann–Whitney test. This effect size expresses the probability of a higher value in a random participant from one group compared with a random patient from the other group, and a value of 0.5 means stochastically equal groups. After 3 months of treatment, there was a significant reduction of the apnea–hypopnea index in the OAa group compared with the OAp group (effect size 0.258, 95% confidence interval 0.146–0.386, p < .001). There were no significant differences between the groups in any of the inflammatory markers’ concentration changes during the treatment period (effect sizes between 0.488 and 0.524; all p values ≥.737). Thus, OA treatment for 3 months did not affect circulating concentrations of some common inflammatory markers in patients with OSA and systemic hypertension.

Nocturnal Continuous Positive Airway Pressure (nCPAP) Decreases High-Sensitivity C-Reactive Protein (hs-CRP) in Obstructive Sleep Apnea-Hypopnea Syndrome

Background

Systemic and airway inflammation has recently been linked to obstructive sleep apnea-hypopnea syndrome (OSAHS) and is considered to be a probable risk factor for OSAHS-induced cardiovascular damage. High-sensitivity C-reactive protein (hs-CRP), as an inflammatory mediator, may be useful for the prediction of the risk of cardiovascular disease (CVD) and assessment of nocturnal continuous positive airway pressure (nCPAP) therapy effect in OSAHS patients.

Methods

A prospective, controlled, cross-sectional study was conducted on 64 consecutive adult subjects with suspected sleep-disordered breathing (SDB).

Results

OSAHS was confirmed in 43 patients (24 normotensive and 19 hypertensive patients) and ruled out in 21 normotensive subjects (controls). The median plasma level of hs-CRP did not differ significantly between OSAHS patients and controls. It showed an unmarked rise with the severity of OSAHS (p = 0.20) and was not correlated with AHI (p = 0.067; r = 0.28). After adjusting for cervical perimeter (CP), waist-to-hip ratio (WHR), and blood sugar level, hs-CRP level of 1 mg/dL or greater was significantly more often observed in OSAHS patients compared with controls (p = 0.032; OR = 5.60) and was also significantly associated with AHI (p = 0.021). A significant decrease in the median plasma hs-CRP level was observed in CPAP compliant patients (p = 0.006). Of those, only normotensive patients showed a significant decrease in plasma hs-CRP level. In hypertensive ones, however, the hs-CRP level dropped but not significantly. Using a linear regression model, the change in hs-CRP level (Δhs-CRP) following a 6-month-nCPAP therapy was found to positively correlate with the baseline hs-CRP level for both hypertensive (p = 0.02; r = 0.68), and even more normotensive OSAHS patients (p < 0.0001; r = 0.89).

Conclusion

nCPAP therapy may have a cardiovascular protective effect in OSAHS patients. hs-CRP level would be useful as a valuable predictor of success in OSAHS treatment monitoring.

The relationship between inflammation and neurocognitive dysfunction in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS), a state of sleep disorder, is characterized by repetitive apnea, chronic hypoxia, oxygen desaturation, and hypercapnia. Previous studies have revealed that intermittent hypoxia (IH) conditions in OSAS patients elicited neuron injury (especially in the hippocampus and cortex), leading to cognitive dysfunction, a significant and extraordinary complication of OSAS patients. The repeated courses of airway collapse and obstruction in OSAS patients resulted in apnea and arousal during sleep, leading to IH and excessive daytime sleepiness (EDS) and subsequently contributing to the development of inflammation. IH-mediated inflammation could further trigger various types of cognitive dysfunction. Many researchers have found that, besides continuous positive airway pressure (CPAP) treatment and surgery, anti-inflammatory substances might alleviate IH-induced neurocognitive dysfunction. Clarifying the role of inflammation in IH-mediated cognitive impairment is crucial for potentially valuable therapies and future research in the related domain. The objective of this article was to critically review the relationship between inflammation and cognitive deficits in OSAS.

CPAP Does Not Reduce Inflammatory Biomarkers in Patients With Coronary Artery Disease and Nonsleepy Obstructive Sleep Apnea: A Randomized Controlled Trial

Objectives

Obstructive sleep apnea (OSA) and enhanced vascular inflammation coexist in patients with coronary artery disease (CAD). Continuous positive airway pressure (CPAP) is first-line treatment for OSA with daytime sleepiness. This analysis of data from the RICCADSA (Randomized Intervention with CPAP in Coronary Artery Disease and Sleep Apnea) trial investigated the effects of CPAP on inflammatory markers in patients with CAD and nonsleepy OSA.

Methods

This single-center, randomized, controlled, open-label trial enrolled consecutive revascularized patients with nonsleepy OSA (apnea-hypopnea index >15/h; Epworth Sleepiness Scale score <10). Levels of high-sensitivity C-reactive protein (hs-CRP), interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) were measured in blood samples taken at baseline (median 94 days after revascularization) and after 1 year of follow-up in patients randomized to CPAP or no-CPAP.

Results

A total of 220 patients with analyzable blood samples at baseline and 1 year were included. Baseline IL-6 levels were significantly lower in the CPAP versus no-CPAP group (median 3.1 pmol/L [interquartile range 1.3-5.7] vs. 4.2 pmol/L [2.0-8.9], respectively; p = .005). At 1-year follow-up, median IL-6 levels were significantly reduced in both groups (to 2.2 pmol/L [1.2-3.9] in the CPAP group and to 2.2 [1.2-4.7] in no-CPAP group; both p < .001 vs. baseline). IL-8, hs-CRP, and TNF-α did not change significantly from baseline. There was no association between CPAP adherence and changes in inflammatory marker levels.

Conclusions

In patients with stable CAD and nonsleepy OSA, inflammatory biomarkers did not change significantly over time except for IL-6 levels, which reduced to the same extent in the CPAP and no-CPAP groups.

Clinical Trial Registration

ClinicalTrials.gov, ID: NCT00519597; researchweb.org, VGSKAS-4731.

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

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

Effect of CPAP therapy on C-reactive protein and cognitive impairment in patients with obstructive sleep apnea hypopnea syndrome

PURPOSE

Obstructive sleep apnea hypopnea syndrome (OSAHS) is associated with neurocognitive impairment. We examined the role of the systemic inflammatory response, measured by high-sensitivity C-reactive protein (hsCRP) assay, and the effect of CPAP treatment on hsCRP and cognitive impairment in patients with OSAHS.

METHODS

Eligible subjects (n = 178) were categorized into two groups: absent or mild OSAHS, and moderate to severe OSAHS. First, the Montreal Cognitive Assessment (MoCA) and serum hsCRP concentration were measured. Then, the moderate to severe OSAHS group was further divided into a conservative treatment subgroup (n = 68) and a CPAP subgroup (n = 68). After 6 months of treatment, MoCA scores and hsCRP concentrations were re-measured in the moderate to severe group.

RESULTS

Compared with the absent or mild OSAHS group, hsCRP concentration was higher (1.00 ± 1.28 mg/L versus 2.71 ± 1.8, p < 0.001) and MoCA scores were significantly lower (27.4 ± 1.4 versus 26.3 ± 2.0, p < 0.001) in the moderate to severe group. After adjustment for age, education, body mass index, and neck circumference, hsCRP and MoCA scores correlated with parameters of overnight hypoxia. hsCRP and the proportion of time spent with blood oxygen saturation < 90 % (T90) predicted MoCA score. hsCRP and MoCA score improved, and the subdomains of the MoCA were partially improved, in the CPAP treatment subgroup. In conservatively managed patients, hsCRP concentration increased, and there was no improvement in neurocognitive dysfunction, with the memory subdomain significantly worse.

CONCLUSIONS

hsCRP may play a role in neurocognitive dysfunction in OSAHS. Long-term CPAP treatment could normalize the serum hsCRP concentration and partially reverse cognitive dysfunction in OSAHS.

Sleep Related Breathing Disorders and Inflammation - The Missing Link? A Cohort Study Evaluating the Interaction of Inflammation and Sleep Related Breathing Disorders and Effects of Treatment

Introduction

Sleep related breathing disorders (SRBD) are associated with both obesity and systemic inflammation. While the relationship between obesity and SRBD is established, the causality between inflammation and SRBD remains unclear. In this study we investigated the relation between SRBD and C-reactive protein (CRP) as a parameter of inflammation and the influence of SRBD treatment on CRP with additional regard to changes in metabolic and cardiovascular parameters.

Methods

Polysomnography (PSG) and laboratory data of patients diagnosed with SRBD over a period of 5 years were prospectively collected in a database and retrospectively analysed regarding the association of SRBD (according to apnoea-hypopnoea- index (AHI), duration of events and extent of desaturation) to CRP, blood pressure, cholesterol, fasting plasma glucose, HbA1c, quality of life measured via a visual analogue scale (VAS 0–100%), and the effects of SRBD therapy on these parameters.

Results

716 patients were included in the study, 171 with mild SRBD (AHI ≥5 to <15/h), 209 with moderate SRBD (AHI 15 to <30/h), 336 with severe SRBD (AHI ≥30/h). Results according to severity of SRBD. Severe SRBD was significantly associated with elevated levels of CRP (3.7 [1.8–7.0] mg/l, vs. moderate (p = 0.001), and mild SRBD (p<0.001), and higher prevalence of hypertension as compared to moderate and mild SRBD (p<0.001, respectively). Results in highly successful treatment. If SRBD treatment was highly successful (AHI <5/h), CRP and quality of life improved significantly (p = 0.001 and p = 0.002), as did blood pressure (p<0.001 for systolic and diastolic values), although BMI increased (p<0.001). Results in partially successful treatment. If success was defined as reduction of AHI of ≥50%, CRP also decreased (p<0.001), as did blood pressure (p<0.001). Again, BMI increased (p<0.001).

Conclusion

This is the first study to show an association of SRBD and CRP independently of BMI in a large cohort. The SRBD therapy-induced CRP decrease was not associated with BMI changes or metabolic changes but rather with the magnitude of AHI improvement.

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

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

IGF-1: a potential biomarker for efficacy of sleep improvement with automatic airway pressure therapy for obstructive sleep apnea?

BACKGROUND

Positive airway pressure (PAP) reverses obstructive sleep apnea (OSA)-related hypoxia and restores slow wave sleep (SWS). Insulin-like growth factor 1 (IGF-1) is a neuropeptide that facilitates the repair of neurons from hypoxia and improves sleep regulation. IGF-1 concentrations are lower in OSA, and likely increase following PAP treatment; however, this relationship has not yet been determined in a younger cohort of OSA patients.

METHODS

This was a prospective, observational pilot study of 58 young men, who were diagnosed with OSA and provided PAP as an intervention. Adherence to PAP treatment over 3 months was objectively measured, as well as changes in the apnea-hypopnea index (AHI). Serum concentrations of IGF-1and C-reactive protein (CRP) were measured and correlated with PAP adherence.

RESULTS

IGF-1 concentrations at baseline were similar between PAP adherent 55.5 ± 34.4 ng/ml and PAP nonadherent participants 61.2 ± 27.1 ng/ml (p = 0.4), with the overall mean IGF-1 concentration of 59.0 ± 29.9 ng/ml. At follow-up, adherent participants had concentrations of IGF-1 that were significantly higher 128 ± 59.5 ng/ml compared to nonadherent participants 86.0 ± 47.4 ng/ml (p < 0.01). Increases in IGF-1 concentrations were significantly associated with reductions in AHI (Spearman's rho = -0.409, p = 0.015). Conversely, CRP concentrations did not differ between baseline and follow-up measurements in either group.

CONCLUSIONS

Adherence to PAP treatment leads to significant increases in IGF-1 concentrations in young men with OSA. While an objective measure of adherence exists, PAP usage does not allow for measure of sleep improvement. IGF-1 may serve as a potential biomarker for the efficacy of PAP therapy on improved sleep.

Intensive versus standard follow-up to improve continuous positive airway pressure compliance

We aimed to compare the effect of intensive versus standard interventions on continuous positive airway pressure (CPAP) adherence 2 years after CPAP initiation, as well as on sleepiness, quality of life, depression, hospitalisation and death rate due to cardiovascular disease (CVD). 3100 patients with newly diagnosed sleep apnoea were randomised into the standard group, with usual follow-up care, or the intensive group, with additional visits, telephone calls and education. Subjective daytime sleepiness (Epworth Sleepiness Scale; ESS), quality of life (36-item Short Form Health Survey; SF-36) and the patient's level of depression (Beck Depression Inventory; BDI) were recorded before and 2 years after CPAP initiation, together with CVD hospitalisations and death rate. 2 years after CPAP initiation, the intensive group used CPAP significantly more than the standard group (6.9 versus 5.2 h per night; p<0.001). ESS, SF-36 and BDI scores were also significantly better in the intensive group. Furthermore, the standard group had significantly more deaths and hospitalisations due to CVD. CPAP usage can be improved by both intensive and standard patient support. However, the patients who received intensive CPAP support had significantly better ESS, BDI and SF-36 scores, and lower cardiovascular morbidity and mortality, suggesting that an intensive programme could be worthwhile.

The effect of obstructive sleep apnea syndrome and snoring severity to intima-media thickening of carotid artery

INTRODUCTION

Intima-media thickening (IMT), which is the early finding of carotid artery atherosclerosis, has been shown to be associated with obstructive sleep apnea syndrome (OSAS). In our study, we aimed to assess prospectively the effect of severity of OSAS and snoring on carotid artery IMT.

METHODS

A total of 102 patients who were admitted to sleep laboratory between May 2011 and May 2012 were included in the study. All patients were examined by polysomnography. Common carotid arteries (CCA) and internal carotid arteries (ICA) were evaluated for IMT by carotid Doppler ultrasonography.

RESULTS

The mean age was 45.9 ± 11.1, with 40 (39.2 %) women and 62 (60.8 %) men. Of 88 OSAS patients who had an apnea-hypopnea index (AHI) of >5, 33 (37.5 %) had mild, 20 (22.7 %) had moderate, and 35 (39.8 %) had severe disease. Fourteen patients who had AHI <5 were designated as the habitual snoring group. IMT was detected in 17 (16.7 %) of all patients. In patients with severe OSAS, CCA walls were thicker (p = 0.040) and IMT ratios were higher (p = 0.019) compared to mild/moderate OSAS patients. In patients with IMT, age, AHI, oxygen desaturation index (ODI), and snoring index were higher compared to patients without IMT (p < 0.05).

CONCLUSION

Carotid artery IMT, which is an early finding of atherosclerosis, was found to be highly correlated with OSAS and snoring severity.

Obstructive sleep apnea and endothelial progenitor cells

BACKGROUND

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

METHODS

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

CONCLUSION

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

Obstructive sleep apnea syndrome is associated with metabolic syndrome and inflammation

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

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pathophysiologic mechanisms of cardiovascular disease in obstructive sleep apnea syndrome

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

Effect of CPAP treatment on endothelial function and plasma CRP levels in patients with sleep apnea

BACKGROUND

Continuous positive airway pressure (CPAP) is the most effective method for treating obstructive sleep apnea syndrome (OSAS) and alleviating symptoms. Improved sleep quality with effective CPAP therapy might also contribute to attenuated systemic inflammation and improved endothelial function, with subsequent reduction of cardiovascular risk. The aim of this study was to assess the effect of 3-month CPAP therapy on brachial artery flow-mediated dilation (FMD) and plasma C-reactive protein (CRP) levels in patients with OSAS.

MATERIAL/METHODS

Our study group consisted of 38 male patients with no prior history of cardiovascular disease. Twenty patients with an Apnea-Hypopnea Index (AHI) ≥15 were assigned to receive CPAP treatment and 18 subjects with an AHI<5 were included in the control group. Six patients failed to comply with the CPAP treatment. Measurement of FMD and blood analysis was performed at baseline and 3 months after CPAP therapy.

RESULTS

Baseline FMD values were negatively correlated with age, BMI, AHI, DSI,% of time <90% Sa02, and CRP (p<0.05). Plasma CRP values were positively correlated with BMI, AHI, DSI and% of time <90% Sa02 (p<0.05). In the group of patients who complied with the CPAP treatment, there was a significant increase in the FMD values (9.18 ± 0.55 vs. 6.27 ± 0.50) and a decrease in the levels of CRP (0.67 ± 0.15 vs. 0.84 ± 0.18) (p<0.05).

CONCLUSIONS

Appropriate CPAP therapy improved both CRP and FMD values, suggesting its potentially beneficial role in reducing cardiovascular risk in OSAS patients.

Treatment for sleep apnea by continuous positive airway pressure improves levels of inflammatory markers - a meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA) is associated with coronary artery disease (CAD). Intermittent hypoxia associated with OSA increases sympathetic activity and may cause systemic inflammation, which may contribute to CAD in patients with OSA. Treatment with continuous positive airway pressure (CPAP) has been shown to change levels of inflammatory markers. We analyzed data from published studies by a systematic meta-analysis.

OBJECTIVE

To asses if treatment for sleep apnea by CPAP will affect levels of inflammatory markers.

DATA RESOURCES

PubMed, Embase and Cochrane library.

METHODS

Study eligibility criteria full text English studies of adult, human subjects, addressing values of at least one of the inflammatory markers before and after CPAP treatment. We used the definition of OSA as an apnea-hypopnea index (AHI) of ≥ 5/h, reported values in mean and standard deviation or median with range.

PARTICIPANTS

Adult, human.

INTERVENTIONS

CPAP treatment for OSA.

STUDY APPRAISAL AND SYNTHESIS METHOD

A total of 3835 studies were reviewed for inclusion, while 23 studies pooled for analysis. A total of 14 studies with 771 patients were pooled for C-reactive protein (CRP); 9 studies with 209 patients were pooled for tumor necrosis factor-alpha (TNF-α); and 8 studies with 165 patients were pooled for interleukin-6 (IL-6).

ENDPOINT DEFINITIONS

THE FOLLOWING INFLAMMATORY MARKERS WERE CHOSEN: CRP, TNF-α, and IL-6.

RESULTS

C-reactive protein: Study level means ranged from 0.18 to 0.85 mg/dl before CPAP treatment and 0.10 to 0.72 mg/dl after CPAP treatment. Mean differences, at a study level, ranged from -0.05 to 0.50. The pooled mean difference was 0.14 [95% confidence interval 0.08 to 0.20, p < 0.00001]. There was heterogeneity in this endpoint (df = 13, p < 0.00001, I(2) = 95%). Tumor necrosis factor-α: Study level means ranged from 1.40 to 50.24 pg/ml before CPAP treatment and 1.80 to 28.63 pg/ml after CPAP treatment. Mean differences, at a study level, ranged from -1.23 to 21.61. The pooled mean difference was 1.14 [95% confidence interval 0.12 to 2.15, p = 0.03]. There was heterogeneity in this endpoint (df = 8, p < 0.00001, I2 = 89%). Interleukin-6: Study level means ranged from 1.2 to 131.66 pg/ml before CPAP treatment and 0.45 to 66.04 pg/ml after CPAP treatment. Mean differences, at a study level, ranged from -0.40 to 65.62. The pooled mean difference was 1.01 [95% confidence interval -0.00 to 2.03, p = 0.05]. There was heterogeneity in this endpoint (df = 7, p < 0.00001, I(2) = 95%).

LIMITATIONS

Only published data. Studies pooled were mainly small, non-randomized trials.

CONCLUSION

Sleep apnea treatment with CPAP improves levels of inflammatory markers.

The interaction of obstructive sleep apnea and obesity on the inflammatory markers C-reactive protein and interleukin-6: the Icelandic Sleep Apnea Cohort

STUDY OBJECTIVES

To assess the relative roles and interaction of obstructive sleep apnea (OSA) severity and obesity on interleukin-6 (IL-6) and C-reactive protein (CRP) levels.

DESIGN

Cross-sectional cohort.

SETTING

The Icelandic Sleep Apnea Cohort.

PARTICIPANTS

454 untreated OSA patients (380 males and 74 females), mean ± standard deviation age 54.4 ± 10.6 yr.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Participants underwent a sleep study, abdominal magnetic resonance imaging to measure total abdominal and visceral fat volume, and had fasting morning IL-6 and CRP levels measured in serum. A significantly higher correlation was found for BMI than visceral fat volume with CRP and IL-6 levels. Oxygen desaturation index, hypoxia time, and minimum oxygen saturation (SaO₂) significantly correlated with IL-6 and CRP levels, but apnea-hypopnea index did not. When stratified by body mass index (BMI) category, OSA severity was associated with IL-6 levels in obese participants only (BMI > 30 kg/m²). A multiple linear regression model with interaction terms showed an independent association of OSA severity with IL-6 levels and an interaction between OSA severity and BMI, i.e., degree of obesity altered the relationship between OSA and IL-6 levels. An independent association of OSA severity with CRP levels was found for minimum SaO₂ only. A similar interaction of OSA severity and BMI on CRP levels was found for males and postmenopausal women.

CONCLUSIONS

OSA severity is an independent predictor of levels of IL-6 and CRP but interacts with obesity such that this association is found only in obese patients.

Impact of continuous positive airway pressure on C-reactive protein in patients with obstructive sleep apnea: a meta-analysis

PURPOSE

C-reactive protein (CRP) is associated with the development of obstructive sleep apnea (OSA) and cardiovascular diseases. Continuous positive airway pressure (CPAP) is an effective treatment for OSA, but the impact of CPAP therapy on CRP levels in patients with OSA remains unclear. To obtain this information, we performed a meta-analysis to determine whether effective CPAP therapy could reduce serum CRP levels.

METHODS

A comprehensive literature search was performed to identify studies that examined the impact of CPAP on serum CRP levels in OSA patients who were treated with CPAP for at least 4 weeks. Standardized mean difference (SMD) was used to analyze the summary estimates for CPAP therapy.

RESULTS

Fourteen self-control design studies involving 1199 patients with OSA met the inclusion criteria. Meta-analysis indicated that the overall SMD for the CRP levels was 0.64 units (95 % confidence interval (CI) 0.40 to 0.88) before and after CPAP therapy; test for overall effect z = 5.27 (P = 0.000). Subgroup analysis showed that evolution of CRP decreased non-significantly in less than 3 months (SMD, 0.26, 95 % CI -0.08 to 0.60, P = 0.138), significantly decreased after 3 months (SMD, 0.68, 95 % CI 0.34 to 1.02, P = 0.000), and further declined after 6 months (SMD, 0.74, 95 % CI 0.43 to 1.05, P = 0.000).

CONCLUSIONS

The systemic inflammation, as measured by CRP, was present and significantly reduced by effective CPAP therapy in patients with OSA. The use of CRP levels may be clinically recognized as a valuable predictor for OSA treatment monitoring.

Sleep apnea determines soluble TNF-α receptor 2 response to massive weight loss

BACKGROUND

The effects of surgical weight loss (WL) on inflammatory biomarkers associated with sleep apnea remain unknown. We sought to determine if any biomarkers can predict amelioration of sleep apnea achieved by bariatric surgery. We hypothesized that surgical WL would substantially reduce severity of sleep apnea and levels of proinflammatory cytokines.

METHODS

Twenty-three morbidly obese adults underwent anthropometric measurements, polysomnography, and serum biomarker profiling prior to and 1 year following bariatric surgery. We examined the effect of WL and amelioration of sleep apnea on metabolic and inflammatory markers.

RESULTS

Surgical WL resulted in significant decreases in BMI (16.7 ± 5.97 kg/m(2)/median 365 days), apnea-hypopnea index (AHI), CRP, IL-6, sTNFαR1, sTNFαR2, and leptin levels, while ghrelin, adiponectin, and soluble leptin receptor concentrations increased significantly. Utilizing an AHI cutoff of 15 events/h, we found significantly elevated levels of baseline sTNFαR2 and greater post-WL sTNFαR2 decreases in subjects with baseline AHI ≥15 events/h compared to those with AHI <15 events/h despite no significant differences in baseline BMI, age, and ΔBMI. In a multivariable linear regression model adjusting for sex, age, impaired glucose metabolism, ΔBMI, and follow-up period, the post-WL decreases in AHI were an independent predictor of the decreases in sTNFαR2 and altogether accounted for 46% of the variance of ΔsTNFαR2 (P = 0.011) in the entire cohort.

CONCLUSIONS

Of all the biomarkers, the decrease in sTNFαR2 was independently determined by the amelioration of sleep apnea achieved by bariatric surgery. The results suggest that sTNFαR2 may be a specific sleep apnea biomarker across a wide range of body weight.

CRP evolution pattern in CPAP-treated obstructive sleep apnea patients. Does gender play a role?

BACKGROUND-AIM

C-reactive protein (CRP) is directly implicated in atherogenesis and associated cardiovascular morbidity in patients with obstructive sleep apnea (OSA). Effective continuous positive airway pressure (CPAP) treatment has been shown to gradually decrease CRP levels and thus consequently improve disease-related cardiovascular morbidity. However, the influence of gender on the CRP evolution pattern has never been assessed before. The aim of our study was to investigate possible gender differences in CRP evolution in OSA patients 3 and 6 months after the start of effective CPAP treatment.

METHODS

The study population consisted of 436 patients (252 males/184 females) with newly diagnosed moderate to severe OSA and good CPAP compliance assessed by a thorough follow up. High-sensitivity C-reactive protein (hs-CRP) was assessed before CPAP initiation and at the third and sixth month of the follow-up period.

RESULTS

C-reactive protein values showed a statistically significant decrease at the third and sixth month of CPAP therapy [initial values 0.79 ± 0.65 mg/dL versus 0.70 ± 0.52 mg/dL (p < 0.05) after 3 months and 0.30 ± 0.33 mg/dL (p < 0.001) after 6 months of CPAP therapy]. When patients were divided into males and females, the above evolution pattern was changed. At the third month time point, the CRP values showed a statistically significant decrease only in males (from 0.74 ± 0.53 mg/dL to 0.61 ± 0.5 mg/dL, p < 0.01) while females showed only minimal and insignificant changes (from 0.87 ± 0.79 mg/dL to 0.83 ± 0.51 mg/dL, p > 0.05). After 6 months' treatment, CRP decreased significantly in both genders (males from 0.74 ± 0.53 mg/dL to 0.28 ± 0.32 mg/dL, p < 0.001 and females from 0.87 ± 0.79 mg/dL to 0.34 ± 0.36 mg/dL, p < 0.001).

CONCLUSION

Our results suggest a delay in the normalization of CRP levels in females despite effective CPAP treatment. A time period of at least 6 months appeared to be required in women in order to reduce CRP levels and consequent cardiovascular risk. In contrast, CPAP's protective role in males is achieved at an earlier time point. Gender-related hormonal and genetic factors may influence the above CRP evolution pattern.

Rosuvastatin, inflammation, C-reactive protein, JUPITER, and primary prevention of cardiovascular disease--a perspective

The major public health concern worldwide is coronary heart disease, with dyslipidemia as a major risk factor. Statin drugs are recommended by several guidelines for both primary and secondary prevention. Rosuvastatin has been widely accepted because of its efficacy, potency, and superior safety profile. Inflammation is involved in all phases of atherosclerosis, with the process beginning in early youth and advancing relentlessly for decades throughout life. C-reactive protein (CRP) is a well-studied, nonspecific marker of inflammation which may reflect general health risk. Considerable evidence suggests CRP is an independent predictor of future cardiovascular events, but direct involvement in atherosclerosis remains controversial. Rosuvastatin is a synthetic, hydrophilic statin with unique stereochemistry. A large proportion of patients achieve evidence-based lipid targets while using the drug, and it slows progression and induces regression of atherosclerotic coronary lesions. Rosuvastatin lowers CRP levels significantly. The Justification for Use of statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) trial was designed after the observation that when both low density lipoprotein and CRP were reduced, patients fared better than when only LDL was lowered. Advocates and critics alike acknowledge that the benefits of rosuvastatin in JUPITER were real. After a review, the US Food and Drug Administration extended the indications for rosuvastatin to include asymptomatic JUPITER-eligible individuals with one additional risk factor. The American Heart Association and Centers of Disease Control and Prevention had previously recognized the use of CRP in persons with "intermediate risk" as defined by global risk scores. The Canadian Cardiovascular Society guidelines went further and recommended use of statins in persons with low LDL and high CRP levels at intermediate risk. The JUPITER study focused attention on ostensibly healthy individuals with "normal" lipid profiles and high CRP values who benefited from statin therapy. The backdrop to JUPITER during this period was an increasing awareness of a rising cardiovascular risk burden and imperfect methods of risk evaluation, so that a significant number of individuals were being denied beneficial therapies. Other concerns have been a high level of residual risk in those who are treated, poor patient adherence, a need to follow guidelines more closely, a dual global epidemic of obesity and diabetes, and a progressively deteriorating level of physical activity in the population. Calls for new and more effective means of reducing risk for coronary heart disease are intensifying. In view of compelling evidence supporting earlier and aggressive therapy in people with high risk burdens, JUPITER simply offers another choice for stratification and earlier risk reduction in primary prevention patients. When indicated, and in individuals unwilling or unable to change their diet and lifestyles sufficiently, the benefits of statins greatly exceed the risks. Two side effects of interest are myotoxicity and an increase in the incidence of diabetes.