Serum inflammatory markers in obstructive sleep apnea: a meta-analysis

Association of Markers of Inflammation with Sleep and Physical Activity Among People Living with HIV or AIDS

This study examined associations of sleep and minutes spent in moderate-vigorous physical activity (MVPA) with C-reactive protein (CRP) and interleukin (IL)-6 among persons living with HIV. Cross-sectional analyses (n = 45) focused on associations of inflammatory outcomes (i.e., CRP and IL-6) with actigraph-derived sleep duration, latency, and efficiency; sleep onset; wake time; and wake-after-sleep-onset; as well as MVPA. Least square means for CRP and IL-6 by levels of sleep and MVPA were computed from general linear models. Individuals below the median of sleep duration, above the median for sleep onset, and below the median of MVPA minutes had higher CRP or IL-6 levels. Generally, individuals with both low MVPA and poor sleep characteristics had higher inflammation levels than those with more MVPA and worse sleep. Understanding the combined impact of multiple lifestyle/behavioral factors on inflammation could inform intervention strategies to reduce inflammation and therefore, chronic disease risk.

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.

The correlation of serum growth differentiation factor-15 level in patients with obstructive sleep apnea

PURPOSE

Growth differentiation factor-(GDF-) is a prognostic biomarker in cardiovascular disorders (CVD). GDF-15 level was not studied in patients with obstructive sleep apnea syndrome (OSAS) before. In this study, we investigated serum GDF-15 levels in OSAS patients and compared them with healthy controls.

MATERIAL AND METHODS

Polysomnographically, confirmed forty consecutive OSAS patients (20 men and 20 women) and forty consecutive healthy controls (23 men and 17 women) were enrolled in the study. The samples in each group had similar demographic characteristics and body mass index (BMI) values.

RESULTS

In the study, no significant correlation was found about GDF-15 levels of OSAS group and healthy controls. However, there was a significant statistical correlation between age and GDF-15 level. In correlation analysis, there was not any significant correlation between age and BMI.

CONCLUSION

Although various developing biomarkers have been studied in cardiovascular disorders, GDF-15 levels have attracted a widespread interest as predictors of cardiovascular risk. GDF-15 level has not been evaluated previously in patients with OSAS. A significant statistical correlation was found between age and GDF-15 level. To reveal close relation between OSAS and GDF-15, further studies are needed with combination of GDF-15 and other biomarkers in OSAS.

Increased methylation of interleukin 6 gene is associated with obesity in Korean women

Obesity is the fifth leading risk for death globally, and a significant challenge to global health. It is a common, complex, non-malignant disease and develops due to interactions between the genes and the environment. DNA methylation can act as a downstream effector of environmental signals; analysis of this process therefore holds substantial promise for identifying mechanisms through which genetic and environmental factors jointly contribute to disease risk. To assess the effects of excessive weight and obesity on gene-specific methylation levels of promoter regions, we determined the methylation status of four genes involved in inflammation and oxidative stress [interleukin 6 (IL6), tumor necrosis factor α (TNFα), mitochondrial transcription factor A (TFAM), and glucose transport 4 (GLUT4)] in blood cell-derived DNA from healthy women volunteers with a range of body mass indices (BMIs) by methylation-specific PCR. Interestingly, the samples from obese individuals (BMI ≥ 30 kg/m(2)) showed significantly increased hypermethylation for IL6 gene compared to normal weight (BMI < 23 kg/m(2)) and overweight samples (23 kg/m(2) ≤ BMI < 30 kg/m(2)) (P = 0.034 and P = 0.026). However, there was no statistically significant difference in promoter methylation of the other 3 genes between each group. These findings suggest that aberrant DNA methylation of IL6 gene promoter may play an important role in the etiology and pathogenesis of obesity and IL6 methylation could be used as molecular biomarker for obesity risk assessment. Further studies are required to elucidate the potential mechanisms underlying this relationship.

Use of continuous positive airway pressure for sleep apnea in the treatment of hypertension

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) and hypertension are highly prevalent and treatable conditions that often coexist and both contribute to an increased cardiovascular risk. The ability of continuous positive airway pressure (CPAP) to improve blood pressure in hypertensive patients with OSA is debated. This review highlights findings from recent studies that have investigated the impact of CPAP on blood pressure in patients with OSA.

RECENT FINDINGS

Comparing the results of various studies is complicated by important methodological differences among them. In hypertensive patients with OSA, treatment with CPAP improves blood pressure to a smaller degree than that derived from antihypertensive medication. Patients with more severe OSA and with greater adherence to CPAP are likely to gain the most benefit from the therapy.

SUMMARY

CPAP should be used in combination with antihypertensive medications in hypertensive patients with OSA. CPAP has the additional benefits of restoring nocturnal dipping and improving arterial stiffness, thus potentially influencing cardiovascular morbidity in these high-risk patients.

Effects of adenotonsillectomy on plasma inflammatory biomarkers in obese children with obstructive sleep apnea: A community-based study

Background

Obesity and obstructive sleep apnea syndrome (OSA) are highly prevalent and frequently overlapping conditions in children that lead to systemic inflammation, the latter being implicated in the various end-organ morbidities associated with these conditions.

Aim

To examine the effects of adenotonsillectomy (T&A) on plasma levels of inflammatory markers in obese children with polysomnographically diagnosed OSA who were prospectively recruited from the community.

Methods

Obese children prospectively diagnosed with OSA, underwent T&A and a second overnight polysomnogram (PSG) after surgery. Plasma fasting morning samples obtained after each of the 2 PSG were assayed for multiple inflammatory and metabolic markers including interleukin-6 (IL-6), IL-18, plasminogen activator inhibitor-1 (PAI-1), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase- (MMP-9), adiponectin, apelin C, leptin and osteocrin.

Results

Out of 122 potential candidates, 100 obese children with OSA completed the study with only 1/3 exhibiting normalization of their PSG after T&A (i.e., AHI≤1/hrTST). However, overall significant decreases in MCP-1, PAI-1, MMP-9, IL-18 and IL-6, and increases in adropin and osteocrin plasma concentrations occurred after T&A. Several of the T&A responsive biomarkers exhibited excellent sensitivity and moderate specificity to predict residual OSA (i.e., AHI≥/hrTST).

Conclusions

A defined subset of systemic inflammatory and metabolic biomarkers is reversibly altered in the context of OSA among community-based obese children, further reinforcing the concept on the interactive pro-inflammatory effects of sleep disorders such as OSA and obesity contributing to downstream end-organ morbidities.

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.

Effects of nondipping pattern on systemic inflammation in obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is a highly prevalent chronic systemic disease in the general population with high morbidity and mortality. Nondipping pattern-failure to drop blood pressure levels in nighttime-is also seen in OSAS patients. We aim to investigate dipping and nondipping patterns of OSAS patients and to compare inflammatory markers.

MATERIALS AND METHODS

Patients with the confirmed diagnosis of OSAS with polysomnography underwent ambulatory blood pressure monitoring. During monitoring, patients with decreased nighttime mean systolic blood pressures 10 % or more were defined as dippers, and the patients without this amount of decrease were defined as nondippers. Peripheral venous blood samples were collected for the analysis of IL-2, IL-6, IL-8, IL-10, IL-12, and TNF-α. Results were compared with convenient statistical tests.

RESULTS

According to monitoring results, 34 of 62 OSAS patients were dipper and 28 of 62 patients were nondipper. Demographic characteristics, OSAS severity, and Apnea Hypopnea Index were similar in both groups. When inflammatory markers were compared between two groups, IL-2 levels were found to be significantly different (p = 0.014).

CONCLUSION

In conclusion, nondipping pattern appears to be associated with increased serum IL-2 levels indicating the increased inflammatory response independently from OSAS severity, and this pattern should be evaluated carefully for possible cardiovascular complications.

Obstructive sleep apnoea, insulin resistance and adipocytokines

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

The role of continuous positive airway pressure in blood pressure control for patients with obstructive sleep apnea and hypertension: a meta-analysis of randomized controlled trials

The aim of this study was to review the effect of continuous positive airway pressure (CPAP) on blood pressure (BP) in patients with obstructive sleep apnea (OSA) and hypertension. Biomedical databases were searched for randomized controlled trials (RCTs) comparing CPAP with control among these patients. Seven RCTs reporting 24-hour ambulatory BP were identified for meta-analysis. CPAP was associated with significant reductions in 24-hour ambulatory systolic blood pressure (SBP) (-2.32 mm Hg; 95% confidence interval [CI], -3.65 to -1.00) and diastolic blood pressure (DBP) (-1.98 mm Hg; 95% CI, -2.82 to -1.14). CPAP led to more significant improvement in nocturnal SBP than that in diurnal SBP. Subgroup analysis showed that patients with resistant hypertension or receiving antihypertensive drugs benefited most from CPAP. Meta-regression indicated that CPAP compliance, age, and baseline SBP were positively correlated with decrease in 24-hour DBP, but not reduction in 24-hour SBP.

Obstructive sleep apnea risk and psychological health among non-Hispanic blacks in the Metabolic Syndrome Outcome (MetSO) cohort study

INTRODUCTION

This study assessed associations of depression and anxiety with risk of obstructive sleep apnea (OSA) among non-Hispanic blacks in the Metabolic Syndrome Outcome (MetSO) study.

METHOD

A total of 1,035 patients participated. ARES™ score ≥6 defined high OSA risk. Moderate depression was defined by a CES-D score ≥16. Moderate anxiety was measured by a BAI score ≥16.

RESULTS

The mean age was 62 ± 14 years; 70% were female. A total of 93% were diagnosed with hypertension; 61%, diabetes; and 72%, dyslipidemia; 90% were overweight/obese; 33% had a history of heart disease; and 10% had a stroke. Logistic regression analysis, adjusting for age and gender, showed that patients with depression had nearly two-fold increased odds of being at risk for OSA (OR 1.75, 95% CI 1.02-2.98, p < 0.05). Patients with anxiety had three-fold increased odds of being at risk for OSA (OR 3.30, 95% CI 2.11-5.15, p < 0.01). After adjusting for marital status and income, patients with anxiety had a 6% increase in OSA risk (OR 1.06, 95% CI 1.04-1.09, p < 0.05), but depression was no longer significant.

CONCLUSION

Our results suggest that non-Hispanic blacks with metabolic syndrome who experience anxiety and/or depression should be screened for OSA.

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.

Simulating obstructive sleep apnea patients' oxygenation characteristics into a mouse model of cyclical intermittent hypoxia

Mouse models of cyclical intermittent hypoxia (CIH) are used to study the consequences of both hypoxia and oxidative stress in obstructive sleep apnea (OSA). Whether or not a mouse model of CIH that simulates OSA patients' oxygenation characteristics would translate into improved patient care remains unanswered. First we identified oxygenation characteristics using the desaturation and resaturation time in 47 OSA subjects from the Molecular Signatures of Obstructive Sleep Apnea Cohort (MSOSA). We observe that a cycle of intermittent hypoxia is not sinusoidal; specifically, desaturation time increases in an almost linear relationship to the degree of hypoxia (nadir), whereas resaturation time is somewhat constant (∼15 s), irrespective of the nadir. Second, we modified the Hycon mouse model of CIH to accommodate a 15-s resaturation time. Using this modified CIH model, we explored whether a short resaturation schedule (15 s), which includes the characteristics of OSA patients, had a different effect on levels of oxidative stress (i.e., urinary 8,12-iso-iPF2α-VI levels) compared with sham and a long resaturation schedule (90 s), a schedule that is not uncommon in rodent models of CIH. Results suggest that shorter resaturation time may result in a higher level of 8,12-iso-iPF2α-VI compared with long resaturation or sham conditions. Therefore, simulating the rodent model of CIH to reflect this and other OSA patients' oxygenation characteristics may be worthy of consideration to better understand the effects of hypoxia, oxidative stress, and their interactions.

[Beneficial effect of continuous positive airway pressure therapy in obstructive sleep apnea syndrome]

Continuous positive airway pressure therapy is an evidence based therapy of obstructive sleep apnea syndrome. The effective treatment of obstructive sleep apnea can decrease sympaticotonia and, consequently, blood pressure. Furthermore, it can improve inflammatory and metabolic parameters resulting in a decreased cardiovascular risk. This article summarizes the positive effects of continuous positive airway pressure therapy on cardiovascular risk factors in obstructive sleep apnea syndrome.

Chronic sleep fragmentation induces endothelial dysfunction and structural vascular changes in mice

STUDY OBJECTIVES

Sleep fragmentation (SF) is a common occurrence and constitutes a major characteristic of obstructive sleep apnea (OSA). SF has been implicated in multiple OSA-related morbidities, but it is unclear whether SF underlies any of the cardiovascular morbidities of OSA. We hypothesized that long-term SF exposures may lead to endothelial dysfunction and altered vessel wall structure.

METHODS AND RESULTS

Adult male C57BL/6J mice were fed normal chow and exposed to daylight SF or control sleep (CTL) for 20 weeks. Telemetric blood pressure and endothelial function were assessed weekly using a modified laser-Doppler hyperemic test. Atherosclerotic plaques, elastic fiber disruption, lumen area, wall thickness, foam cells, and macrophage recruitment, as well as expression of senescence-associated markers were examined in excised aortas. Increased latencies to reach baseline perfusion levels during the post-occlusive period emerged in SF mice with increased systemic BP values starting at 8 weeks of SF and persisting thereafter. No obvious atherosclerotic plaques emerged, but marked elastic fiber disruption and fiber disorganization were apparent in SF-exposed mice, along with increases in the number of foam cells and macrophages in the aorta wall. Senescence markers showed reduced TERT and cyclin A and increased p16INK4a expression, with higher IL-6 plasma levels in SF-exposed mice.

CONCLUSIONS

Long-term sleep fragmentation induces vascular endothelial dysfunction and mild blood pressure increases. Sleep fragmentation also leads to morphologic vessel changes characterized by elastic fiber disruption and disorganization, increased recruitment of inflammatory cells, and altered expression of senescence markers, thereby supporting a role for sleep fragmentation in the cardiovascular morbidity of OSA.

Targeting Sleep Disordered Breathing to Prevent Heart Failure: What is the Evidence?

The inter-relationships of sleep disordered breathing (SDB) and heart failure (HF) are becoming increasingly well-characterized. The pathways linking the two entities are likely bi-directional and key underlying pathophysiological mechanisms at play include autonomic nervous system fluctuations, intermittent hypoxia, intrathoracic cardiac mechanical influences, rostral fluid shifts and up-regulation of systemic inflammation and oxidative stress. Given the increased morbidity and mortality which accompanies heart failure, the recognition and treatment of factors such as sleep disordered breathing is paramount in order to mitigate these untoward downstream health consequences. Recently, the management of HF requires combining several treatments including pharmacotherapy, electrophysiologic therapy, and cardiac surgery to target the various complex facets of HF. Despite the development of HF treatments, HF remains to pose a great challenge to the general cardiologist. Herein we review several interventional studies highlighting the effects of treating SDB on HF morbidity and mortality with a notable predominance of literature focusing on HF reduced ejection fraction (HF-REF) as well as emerging data describing SDB treatment effects in HF preserved EF (HF-PEF). These data are compelling yet with intrinsic limitations which underscore the need for appropriately powered clinical trials employing rigorous clinical trials methodology to examine the effect of SDB treatment on HF progression and associated adverse outcomes.

Inflammatory markers and obstructive sleep apnea in obese children: the NANOS study

Introduction. Obesity and obstructive sleep apnea syndrome (OSA) are common coexisting conditions associated with a chronic low-grade inflammatory state underlying some of the cognitive, metabolic, and cardiovascular morbidities. Aim. To examine the levels of inflammatory markers in obese community-dwelling children with OSA, as compared to no-OSA, and their association with clinical and polysomnographic (PSG) variables. Methods. In this cross-sectional, prospective multicenter study, healthy obese Spanish children (ages 4–15 years) were randomly selected and underwent nocturnal PSG followed by a morning fasting blood draw. Plasma samples were assayed for multiple inflammatory markers. Results. 204 children were enrolled in the study; 75 had OSA, defined by an obstructive respiratory disturbance index (RDI) of 3 events/hour total sleep time (TST). BMI, gender, and age were similar in OSA and no-OSA children. Monocyte chemoattractant protein-1 (MCP-1) and plasminogen activator inhibitor-1 (PAI-1) levels were significantly higher in OSA children, with interleukin-6 concentrations being higher in moderate-severe OSA (i.e., AHI > 5/hrTST; P < 0.01), while MCP-1 levels were associated with more prolonged nocturnal hypercapnia (P < 0.001). Conclusion. IL-6, MCP-1, and PAI-1 are altered in the context of OSA among community-based obese children further reinforcing the proinflammatory effects of sleep disorders such as OSA. This trial is registered with ClinicalTrials.gov NCT01322763.

Obstructive sleep apnea-hypopnea syndrome (OSAHS) and glaucomatous optic neuropathy

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is becoming widely accepted as a risk factor for glaucoma. We discuss the proposed mechanism involved in the pathogenesis of glaucoma in OSAHS, and review the published data on the association between these two conditions, as well as papers regarding functional and structural tests related with glaucomatous damage. There is increasing evidence that the prevalence of glaucoma is higher in OSAHS patients, especially in those with severe disease with apnea-hypopnea index (AHI) >30, and also that sleep disorders may be more frequent in patients with glaucoma, especially in those with normal tension glaucoma (NTG). Several ophthalmic signs and symptoms have been associated with this condition. Raised intraocular pressure (IOP), possibly related to increased body mass index, thinning of retinal nerve fiber layer (RNFL), and alteration of visual field (VF) indices has been demonstrated in many studies, in patients with no history of glaucoma or evidence of glaucomatous changes in the ophthalmic examination. A correlation of AHI with RNFL and VF indices has been described in some studies. Finally, corneal thinning, suspicious glaucomatous disc changes and anomalies in electrophysiological tests such as multifocal visual evoked potential have been described in patients with OSAHS, even in patients with normal findings in the optic nerve and VF, suggesting subclinical optic nerve involvement not detectable in conventional ophthalmic examinations. The pathogenesis of optic nerve involvement has been related to vascular and mechanical factors. Vascular factors include recurrent hypoxia with increased vascular resistance, autonomic deregulation, oxidative stress and inflammation linked to hypoxia and subsequent reperfusion, decreased cerebral perfusion pressure and direct hypoxic damage to the optic nerve. Proposed mechanical factors include increased IOP at night related to supine position and obesity, raised intracranial pressure and elastic fiber depletion in the lamina cribosa and/or trabeculum. In conclusion, ophthalmic evaluation should be recommended in patients with severe OSAHS, and the presence of sleep disorders should be investigated in patients with glaucoma, especially in NTG patients and in those with progressive damage despite controlled IOP, as treatment with continuous positive airway pressure may contribute to stabilizing the progression of glaucomatous damage.

Effect of obstructive sleep apnea hypopnea syndrome on lipid profile: a meta-regression analysis

BACKGROUND

Obstructive sleep apnea (OSA) is associated with obesity, metabolic syndrome, and dyslipidemia, which may be related to decrease androgen levels found in OSA patients. Dyslipidemia may contribute to atherosclerosis leading to increasing risk of heart disease.

METHODS

Systematic review was conducted using PubMed and Cochrane library by utilizing different combinations of key words; sleep apnea, obstructive sleep apnea, serum lipids, dyslipidemia, cholesterol, total cholesterol, low density lipoprotein (LDL), high density lipoprotein (HDL), and triglyceride (TG). Inclusion criteria were: English articles, and studies with adult population in 2 groups of patients (patients with OSA and without OSA). A total 96 studies were reviewed for inclusion, with 25 studies pooled for analysis.

RESULTS

Sixty-four studies were pooled for analysis; since some studies have more than one dataset, there were 107 datasets with 18,116 patients pooled for meta-analysis. All studies measured serum lipids. Total cholesterol pooled standardized difference in means was 0.267 (p = 0.001). LDL cholesterol pooled standardized difference in means was 0.296 (p = 0.001). HDL cholesterol pooled standardized difference in means was -0.433 (p = 0.001). Triglyceride pooled standardized difference in means was 0.603 (p = 0.001). Meta-regression for age, BMI, and AHI showed that age has significant effect for TC, LDL, and HDL. BMI had significant effect for LDL and HDL, while AHI had significant effect for LDL and TG.

CONCLUSION

Patients with OSA appear to have increased dyslipidemia (high total cholesterol, LDL, TG, and low HDL).

[What pathomechanisms can lead to stroke in obstructive sleep apnea?]

One of the less well-documented, potentially modifiable stroke risk factor is the obstructive sleep apnea. Obstructive sleep apnea increases cardiovascular morbidity and mortality, including stroke risk. The article summarizes the pathophysiological factors in sleep apnea syndrome which can increase stroke risk.

Myeloid-related protein-8/14 and C-reactive protein in individuals evaluated for obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) and obesity are often present concomitantly. Their potential contribution to inflammation remains an ongoing debate. The objectives of this study were to investigate whether variables of sleep-disordered breathing are associated with levels of myeloid-related protein-8/14 (MRP-8/14) or C-reactive protein (CRP), and to characterize how adiposity interacts with these associations in individuals evaluated for possible OSA.

METHODS

Consecutive individuals referred to Lovisenberg Diakonale Hospital's sleep laboratory between 1st October 2009 and 1st March 2010 were included. We characterized the biomarker distribution sampled the morning after sleep and related these to clinical characteristics and variables recorded during polygraphy or polysomnography.

RESULTS

Of the total study population of 222 individuals, 161 (72.5%) were diagnosed with OSA (apnea-hypopnea index (AHI) > or = 5/h). In baseline models (multiple median regression adjusted for age and sex), AHI was independently associated with MRP-8/14 (P=0.025) and CRP (P<0.001). The associations were attenuated after the addition of body mass index (BMI), but remained statistically significant for CRP (P=0.025). However, in final models adjusted for additional factors (systolic blood pressure, cholesterol:high-density lipoprotein ratio, glycosylated haemoglobin, smoking, and cardiovascular disease), only average oxygen saturation for MRP-8/14 (P=0.028) and oxygen desaturation index (ODI) for CRP (P=0.037) remained independent predictors of inflammation, whereas AHI lost its predictive value (MRP-8/14; P=0.30 and CRP; P=0.092). The association between several variables of sleep-disordered breathing and inflammation were stronger in individuals with a higher BMI (P for interaction <0.05 for AHI, nadir oxygen saturation, and time <90% oxygen saturation).

CONCLUSIONS

No definitive indication of independent immunological activity resulting from apneas and hypopneas was found in final models adjusted for other factors associated with inflammation, whereas average oxygen saturation for MRP-8/14 and ODI for CRP remained statistically significant predictors. Interactions were observed between BMI and several variables of sleep-disordered breathing on MRP-8/14 and CRP levels.