Correlates of serum C-reactive protein (CRP)--no association with sleep duration or sleep disordered breathing

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.

Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society on the Recommended Amount of Sleep for a Healthy Adult: Methodology and Discussion

The American Academy of Sleep Medicine and Sleep Research Society recently released a Consensus Statement regarding the recommended amount of sleep to promote optimal health in adults. This paper describes the methodology, background literature, voting process, and voting results for the consensus statement. In addition, we address important assumptions and challenges encountered during the consensus process. Finally, we outline future directions that will advance our understanding of sleep need and place sleep duration in the broader context of sleep health.

Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society on the Recommended Amount of Sleep for a Healthy Adult: Methodology and Discussion

The American Academy of Sleep Medicine and Sleep Research Society recently released a Consensus Statement regarding the recommended amount of sleep to promote optimal health in adults. This paper describes the methodology, background literature, voting process, and voting results for the consensus statement. In addition, we address important assumptions and challenges encountered during the consensus process. Finally, we outline future directions that will advance our understanding of sleep need and place sleep duration in the broader context of sleep health.

The interactive effects of nocturnal sleep and daytime naps in relation to serum C-reactive protein

BACKGROUND AND AIM

C-reactive protein (CRP) is a general marker of inflammation that has been differentially linked with sleep. Elevated CRP (ie, high inflammation) has been associated with either short/insufficient sleep duration or long sleep duration, both, or neither. Daytime napping has also been tied to increased and decreased inflammation. We attempted to unify these findings by examining the relationship between CRP and sleep duration in conjunction with napping in a healthy young adult cohort.

PARTICIPANTS

Participants were young adults (mean age = 29.05 years, n = 2147) from the National Longitudinal Study of Adolescent Health (Add Health) cohort, a nationally representative longitudinal sample.

METHODS/RESULTS

Analysis of covariance (ANCOVA) tests examined whether self-reported sleep duration (short, medium, or long) and nap frequency (none-few days/week; most days/week; every day) interacted in relation to CRP. Standard covariates (ie, age, gender, race/ethnicity, body mass index, physical activity, depression, snoring, systolic blood pressure, clinical symptoms, and household income) were used. There was a linear increase in CRP with increased napping [contrast estimate = 0.265, 95% confidence interval (CI) (0.045-0.485), P = 0.018]. There was also an interaction between sleep duration and napping frequency in relation to CRP (F4,2128 = 2.90, P = 0.021). Inflammation differed between nap groups within the long and short sleep groups.

CONCLUSIONS

Our results suggest that increased napping is an independent predictor of inflammation in young adults. These results also provide evidence for interactive effects of inflammation, nocturnal sleep, and daytime naps. Our findings confirm that excess sleep, insufficient sleep, frequent napping, and infrequent napping can all be linked with elevated CRP, but these relationships depend on both nocturnal and daytime sleep patterns. These analyses will guide future work to more specifically examine sleep-inflammation processes and directionality.

Obstructive sleep apnea is independently associated with inflammation and insulin resistance, but not with blood pressure, plasma catecholamines, and endothelial function in obese subjects

OBJECTIVES

Obstructive sleep apnea (OSA) is associated with an increased risk of cardiovascular disease (CVD). Several of the proposed mechanisms for the development of CVD in OSA are similar to those proposed for the increased risk of CVD in obesity, so that it is difficult to determine the influence of OSA on these pathogenic mechanisms in obese individuals. The aim of this study was to evaluate the relationship of OSA with endothelial function, oxidative stress, inflammatory biomarkers, metabolic profile, sympathetic nervous system activity, and blood pressure (BP) in obese individuals.

METHODS

This cross-sectional study included 53 obese adults (28 women). Sleep study was performed with WatchPAT 200 (Itamar Medical, Caesarea, Israel) and the diagnosis of OSA was made when apnea-hypopnea index (AHI) ≥5 events/h (n = 33). All participants underwent evaluation of: body adiposity, BP, plasma catecholamines, high sensitivity C-reactive protein (hs-CRP), adiponectin, malondialdehyde, glucose, insulin, lipid profile, and endothelial function (EndoPAT 2000).

RESULTS

In univariate analysis, participants with OSA compared with those without OSA exhibited higher values of neck circumference, glucose, noradrenaline, and systolic BP. After adjustment for confounders, including adiposity, only glucose and hs-CRP were significantly higher in OSA patients. In correlation analysis, after controlling for confounders, AHI was positively and significantly associated with neck circumference and hs-CRP, while minimum O2 saturation was associated negatively and significantly with neck circumference, insulin and homeostatic model assessment-insulin resistance (HOMA-IR).

CONCLUSIONS

The present study suggests that in obese individuals OSA is independently associated with inflammation and insulin resistance, but not with BP, plasma catecholamines and endothelial function.

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.

The impact of obstructive sleep apnea on high-sensitivity C-reactive protein in subjects with or without metabolic syndrome

BACKGROUND

It is unclear whether obstructive sleep apnea (OSA) is independently associated with increased levels of the acute-phase reactant C-reactive protein (CRP). The purpose of this study was to evaluate the relationship between OSA and high-sensitivity CRP (hs-CRP) levels according to the presence or absence of metabolic syndrome (MetS).

METHODS

This study recruited 245 male bus drivers from one transportation company in Taiwan. Each participant was evaluated by a polysomnography (PSG) test, blood lipids examination, and hs-CRP. Severity of OSA was categorized according to the apnea-hypopnea index (AHI).

RESULTS

Subjects were categorized into severe OSA group (n = 44; 17.9 %), moderate and mild OSA group (n = 117; 47.8 %), and non-OSA group (n = 84; 34.3 %). AHI had a significant association with hs-CRP (β = 0.125, p = 0.009) adjusting for age, smoking, drinking, and MetS status. Hs-CRP was elevated with severe OSA (β = 0.533, p = 0.005) even adjusting for BMI and MetS. Moreover, there was an independent effect for adjusted odds ratios (AORs) between the stratification of the severity for OSA and MetS.

CONCLUSION

Elevated hs-CRP level is associated with severe OSA, independent of known confounders. The effect of OSA in CRP is independent of MetS was identified.

Increased inflammatory activity in nonobese patients with coronary artery disease and obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is common in patients with coronary artery disease (CAD). Enhanced vascular inflammation is implicated as a pathophysiologic mechanism but obesity is confounding. We aimed to address the association of OSA with inflammatory biomarkers in a nonobese cohort of revascularized patients with CAD and preserved left ventricular ejection fraction.

DESIGN

Cross-sectional analysis of baseline investigations of a randomized controlled trial.

SETTING

Clinic-based.

PARTICIPANTS

There were 303 nonobese patients with CAD, of whom 213 with OSA (apnea-hypopnea index [AHI] ≥15 events/h) and 90 without OSA (AHI < 5 events/h). Obese patients with CAD and OSA (N = 105) were chosen as an additional control group.

INTERVENTIONS

None.

MEASUREMENTS

Circulating levels of high-sensitivity C-reactive protein (hs-CRP), interleukin (IL)-6, IL-8, and tumor necrosis factor-α were assessed in relation to OSA diagnosis based on AHI ≥ 15 events/h as well as oxygen desaturation index (ODI) ≥ 5 events/h.

RESULTS

Nonobese patients with OSA had significantly higher levels of hs-CRP and IL-6 than those without OSA. The values did not differ significantly between obese and nonobese patients with OSA. In bivariate regression analysis, AHI ≥ 15 events/h was associated with all four biomarkers but not so in the multivariate model after adjustment for confounders. ODI ≥ 5 events/h was associated with hs-CRP (odds ratio [OR] 1.49, 95% confidence interval [CI] 1.13-1.99) and IL-6 (OR 1.30; 95% CI 1.05-1.60) in multivariate analysis.

CONCLUSIONS

OSA with ODI ≥ 5 was independently associated with increased inflammatory activity in this nonobese CAD cohort. The intermittent hypoxemia, rather than the number of apneas and hypopneas, appears to be primarily associated with enhanced inflammation.

Persistent insomnia is associated with mortality risk

BACKGROUND

Insomnia has been associated with mortality risk, but whether this association is different in subjects with persistent vs intermittent insomnia is unclear. Additionally, the role of systemic inflammation in such an association is unknown.

METHODS

We used data from a community-based cohort to determine whether persistent or intermittent insomnia, defined based on persistence of symptoms over a 6-year period, was associated with death during the following 20 years of follow-up. We also determined whether changes in serum C-reactive protein (CRP) levels measured over 2 decades between study initiation and insomnia determination were different for the persistent, intermittent, and never insomnia groups. The results were adjusted for confounders such as age, sex, body mass index, smoking, physical activity, alcohol, and sedatives.

RESULTS

Of the 1409 adult participants, 249 (18%) had intermittent and 128 (9%) had persistent insomnia. During a 20-year follow-up period, 318 participants died (118 due to cardiopulmonary disease). In adjusted Cox proportional-hazards models, participants with persistent insomnia (adjusted hazards ratio [HR] 1.58; 95% confidence interval [CI], 1.02-2.45) but not intermittent insomnia (HR 1.22; 95% CI, 0.86-1.74) were more likely to die than participants without insomnia. Serum CRP levels were higher and increased at a steeper rate in subjects with persistent insomnia as compared with intermittent (P = .04) or never (P = .004) insomnia. Although CRP levels were themselves associated with increased mortality (adjusted HR 1.36; 95% CI, 1.01-1.82; P = .04), adjustment for CRP levels did not notably change the association between persistent insomnia and mortality.

CONCLUSIONS

In a population-based cohort, persistent, and not intermittent, insomnia was associated with increased risk for all-cause and cardiopulmonary mortality and was associated with a steeper increase in inflammation.

Evaluation of the association of sleep apnea-related systemic inflammation with CRP, ESR, and neutrophil-to-lymphocyte ratio

Background

Obstructive sleep apnea syndrome (OSAS) is characterized by cyclic episodes of hypoxemia and reoxygenation. It has been suggested that OSAS is associated with chronic inflammation within the microvasculature. This low-grade inflammation may play a role in the pathophysiology of OSAS-related comorbidities. Evaluation of the inflammatory markers may predict the degree of the systemic inflammation and this may be a prognostic factor for future adverse events such as cardiovascular risks. Proinflammatory cytokines have been extensively studied in sleep-disordered breathing. Neutrophil-to-lymphocyte ratio is a recently described indicator of systemic inflammation, but it has not been studied in OSAS patients. In this study we aimed to evaluate the easily measurable parameters of systemic inflammation in these patients. We conducted this study to examine the association among OSAS and C- reactive protein, erythrocyte sedimentation rate, and neutrophil-to-lymphocyte ratio.

Material/Methods

OSAS patients who underwent overnight polysomnography were studied retrospectively. They were divided into 4 groups: control, mild, moderate, and severe OSAS patients. Blood test results and inflammatory markers were compared between the groups. One-way ANOVA and Kruskall-Wallis H test were used for statistical analysis.

Results

A total of 147 patients were included in the study. No differences in evaluated inflammatory markers were observed among the 4 groups.

Conclusions

Evaluation of the OSAS-related systemic inflammation is not likely to be possible by CRP, ESR, or neutrophil-to-lymphocyte ratio measurements. These markers do not seem to be associated with the degree of the upper airway obstruction.

Association between sleep duration and mortality is mediated by markers of inflammation and health in older adults: the Health, Aging and Body Composition Study

STUDY OBJECTIVES

Inflammation may represent a common physiological pathway linking both short and long sleep duration to mortality. We evaluated inflammatory markers as mediators of the relationship between sleep duration and mortality in community-dwelling older adults.

DESIGN

Prospective cohort with longitudinal follow-up for mortality outcomes.

SETTING

Pittsburgh, Pennsylvania, and Memphis, Tennessee.

PARTICIPANTS

Participants in the Health, Aging and Body Composition (Health ABC) Study (mean age 73.6 ± 2.9 years at baseline) were sampled and recruited from Medicare listings.

MEASUREMENTS AND RESULTS

Baseline measures of subjective sleep duration, markers of inflammation (serum interleukin-6, tumor necrosis factor-α, and C-reactive protein) and health status were evaluated as predictors of all-cause mortality (average follow-up = 8.2 ± 2.3 years). Sleep duration was related to mortality, and age-, sex-, and race-adjusted hazard ratios (HR) were highest for those with the shortest (< 6 h HR: 1.30, CI: 1.05-1.61) and longest (> 8 h HR: 1.49, CI: 1.15-1.93) sleep durations. Adjustment for inflammatory markers and health status attenuated the HR for short (< 6 h) sleepers (HR = 1.06, 95% CI = 0.83-1.34). Age-, sex-, and race-adjusted HRs for the > 8-h sleeper group were less strongly attenuated by adjustment for inflammatory markers than by other health factors associated with poor sleep with adjusted HR = 1.23, 95% CI = 0.93-1.63. Inflammatory markers remained significantly associated with mortality.

CONCLUSION

Inflammatory markers, lifestyle, and health status explained mortality risk associated with short sleep, while the mortality risk associated with long sleep was explained predominantly by lifestyle and health status.

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.

Sleep duration, insomnia, and markers of systemic inflammation: results from the Netherlands Study of Depression and Anxiety (NESDA)

Systemic inflammation has emerged as a potential pathway linking depressive and anxiety disorders with disease risk. Short and long sleep duration, as well as insomnia, are common among psychiatric populations and have previously been related to increased inflammation. The aim of the present study was to investigate associations between sleep duration and insomnia with biomarkers of inflammation and to explore whether these associations varied by psychiatric diagnostic status. To this end, self-reported measures of sleep duration, insomnia symptoms, and markers of inflammation, including C-reactive protein (CRP), interleukin-(IL)-6, and tumor necrosis factor (TNF)-α, were obtained in 2553 adults (aged 18-65 years) diagnosed with current/recent or remitted depressive and/or anxiety disorders and healthy controls enrolled in the Netherlands Study of Depression and Anxiety (NESDA). Regression analyses revealed associations between sleep duration and levels of CRP and IL-6 with higher levels observed in long sleepers. These associations remained statistically significant after controlling for age, gender, education, body mass index, smoking, alcohol consumption, medical comorbidities, medication use, psychotropic medication use, and psychiatric diagnostic status. There were no clear associations between insomnia symptoms and levels of inflammation. Relationships between sleep duration and inflammation did not vary as a function of psychiatric diagnostic status. These findings suggest that elevated levels of systemic inflammation may represent a mechanism linking long sleep duration and disease risk among those with and without depressive and anxiety disorders.

Daytime napping, sleep duration and serum C reactive protein: a population-based cohort study

OBJECTIVES

To explore whether daytime napping and sleep duration are linked to serum C reactive protein (CRP), a pro-inflammatory marker, in an older aged British population.

DESIGN

Cross-sectional study.

SETTING

European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk study.

PARTICIPANTS

A total of 5018 men and women aged 48-92 years reported their sleep habits and had serum CRP levels measured.

OUTCOME AND MEASURES

CRP was measured (mg/L) during 2006-2011 in fresh blood samples using high-sensitivity methods. Participants reported napping habits during 2002-2004, and reported sleep quantity during 2006-2007. Multivariable linear regression models were used to examine the association between napping and log-transformed CRP, and geometric mean CRP levels were calculated.

RESULTS

After adjustment for age and sex, those who reported napping had 10% higher CRP levels compared with those not napping. The association was attenuated but remained borderline significant (β=0.05 (95% CI 0.00 to 0.10)) after further adjustment for social class, education, marital status, body mass index, physical activity, smoking, alcohol intake, self-reported health, pre-existing diseases, systolic blood pressure, hypnotic drug use, depression and in women-only hormone replacement therapy use. The geometric means (95% CI) of CRP levels were 2.38 (2.29 to 2.47) mg/L and 2.26 (2.21 to 2.32) mg/L for those who reported napping and no napping, respectively. A U-shaped association was observed between time spent in bed at night and CRP levels, and nighttime sleep duration was not associated with serum CRP levels. The association between napping and CRP was stronger for older participants, and among extremes of time spent in bed at night.

CONCLUSIONS

Daytime napping was associated with increased CRP levels in an older aged British population. Further studies are needed to determine whether daytime napping is a cause for systemic inflammation, or if it is a symptom or consequence of underlying health problems.

Altered in vitro endothelial repair and monocyte migration in obstructive sleep apnea: implication of VEGF and CRP

STUDY OBJECTIVES

Although obstructive sleep apnea (OSA) causes cardiovascular morbidities through atherosclerosis induced by inflammation and endothelial dysfunction, OSA patients exhibit elevated plasma vascular endothelial growth factor (VEGF), which may represent an adaptive response to intermittent hypoxia. The aims of this study were to investigate whether in vitro endothelial wound healing and monocyte migration are affected by patient serum, and to determine the implication of circulating factors (VEGF and C-reactive protein).

PATIENTS

Serum was collected from healthy controls (HC), "healthy" OSA, and metabolic syndrome (MS) patients with or without OSA.

MEASUREMENTS AND RESULTS

Along with the presence of OSA and/or MS, both VEGF and hsCRP were significantly elevated in patient serum. Their specific role was tested with blocking antibodies on primary endothelial cells for wound healing assay and on human monocytes for migration assay. Endothelial wound healing was reduced with OSA compared to HC serum, and even more significantly using MS+OSA patient serum. Altered wound healing with OSA serum was unmasked when blocking VEGF and restored when blocking CRP. Monocyte migration was activated with OSA serum, and further enhanced by MS+OSA patient serum. Blocking CRP in serum inhibited this migration.

CONCLUSIONS

Serum from OSA patient alters in vitro endothelial cell repair function and activates monocyte migration; this is further aggravated with the presence of metabolic syndrome. These effects are partly driven by VEGF and CRP, suggesting an unfavorable balance between the pro healing (VEGF) and pro injury (CRP) factors that may promote vascular injury in OSA with and without metabolic syndrome.

Sleep duration during the school week is associated with C-reactive protein risk groups in healthy adolescents

BACKGROUND

The prevalence of short sleep duration in adolescence and the relevance of early risk factors to cardiovascular disease in adulthood suggest that adolescence is an opportune time to evaluate links between sleep duration and cardiovascular disease risk. We examined associations among actigraphy-assessed sleep duration and sleep debt with elevated C-reactive protein (CRP), a known risk factor for cardiovascular disease.

METHODS

Participants were 244 (56% Black, 48% male) healthy high school students, each of whom wore wrist actigraphs for one week and provided a fasting blood draw. CRP was examined as both a continuous and categorical outcome, with CRP >3 mg/L identifying a High Risk Group.

RESULTS

Sleep duration and sleep debt were significantly associated with CRP High Risk Group in covariate-adjusted analyses. Shorter sleep duration on school nights was associated with a greater likelihood of being in the High Risk CRP Group. Likelihood of being in the High Risk CRP Group was doubled in students who obtained an average of two or more hours of "catch up" sleep on weekend nights.

CONCLUSIONS

Reduced weekday sleep duration and sleep debt were both associated with CRP Risk Group in adolescence. That these relationships may be observed prior to the onset of clinical disease suggests that adolescence may provide an opportune period for disease prevention.

Why sleep is important for health: a psychoneuroimmunology perspective

Sleep has a critical role in promoting health. Research over the past decade has documented that sleep disturbance has a powerful influence on the risk of infectious disease, the occurrence and progression of several major medical illnesses including cardiovascular disease and cancer, and the incidence of depression. Increasingly, the field has focused on identifying the biological mechanisms underlying these effects. This review highlights the impact of sleep on adaptive and innate immunity, with consideration of the dynamics of sleep disturbance, sleep restriction, and insomnia on (a) antiviral immune responses with consequences for vaccine responses and infectious disease risk and (b) proinflammatory immune responses with implications for cardiovascular disease, cancer, and depression. This review also discusses the neuroendocrine and autonomic neural underpinnings linking sleep disturbance and immunity and the reciprocal links between sleep and inflammatory biology. Finally, interventions are discussed as effective strategies to improve sleep, and potential opportunities are identified to promote sleep health for therapeutic control of chronic infectious, inflammatory, and neuropsychiatric diseases.

Epigenetics modifications and Subclinical Atherosclerosis in Obstructive Sleep Apnea: The EPIOSA study

Background

Obstructive sleep apnea (OSA) is associated with increased risk for cardiovascular morbidity and mortality. Epidemiological and animal models studies generate hypotheses for innovative strategies in OSA management by interfering intermediates mechanisms associated with cardiovascular complications. We have thus initiated the Epigenetics modification in Obstructive Sleep Apnea (EPIOSA) study (ClinicalTrials.gov identifier: NCT02131610).

Methods/design

EPIOSA is a prospective cohort study aiming to recruit 350 participants of caucasian ethnicity and free of other chronic or inflammatory diseases: 300 patients with prevalent OSA and 50 non-OSA subjects. All of them will be follow-up for at least 5 years. Recruitment and study visits are performed in single University-based sleep clinic using standard operating procedures. At baseline and at each one year follow-up examination, patients are subjected to a core phenotyping protocol. This includes a standardized questionnaire and physical examination to determine incident comorbidities and health resources utilization, with a primary focus on cardiovascular events. Confirmatory outcomes information is requested from patient records and the regional Department of Health Services. Every year, OSA status will be assessed by full sleep study and blood samples will be obtained for immediate standard biochemistry, hematology, inflammatory cytokines and cytometry analysis. For biobanking, aliquots of serum, plasma, urine, mRNA and DNA are also obtained. Bilateral carotid echography will be performed to assess subclinical atherosclerosis and atherosclerosis progression. OSA patients are treated according with national guidelines.

Discussion

EPIOSA will enable the prospective evaluation of inflammatory and epigenetics mechanism involved in cardiovascular complication of treated and non-treated patients with OSA compared with non OSA subjects.

Association between sleep quality and C-reactive protein: results from national health and nutrition examination survey, 2005-2008

Objective

Our objective was to explore the association between poor sleep quality and hs_CRP in an adult U.S. population.

Methods

This study focused on 9,317 participants in the National Health and Nutrition Examination Survey (NHANES) from 2005–2008 who were aged 20–85 years, completed a sleep disorder questionnaire, and had available information on serum hs_CRP. Sleep quality was classified into three categories (good, moderate, poor) based on the responses of participants to the NHANES sleep disorder questionnaire. High CRP was defined as hs-CRP >1 md/dL. Linear regression model was applied to investigate the association between poor sleep quality and log-transformed hs_CRP. And logistic regression model was fitted to evaluate the association between sleep quality and the risk of high CRP.

Results

Females were more likely to report poor sleep quality than males (26% vs. 19%, p<0.0001). Each sleep disorder was significantly associated with increased hs_CRP and correlative to other sleep disorders. In fully-adjusted linear regression model, poor sleep quality was significantly associated with elevated hs_CRP (log transformed) among the overall sample and in females only (β = 0.10, se = 0.03, p<0.01 and β = 0.13, se = 0.04, p<0.01, respectively). In fully-adjusted logistics regression model, poor sleep quality was linked with risk of high CRP(OR: 1.42, 95%CI: 1.15–1.76 in overall sample and OR: 1.59, 95%CI: 1.18–2.14 in females, respectively).

Conclusion

We found that poor sleep quality was independently associated with elevated hs_CRP in females but not in males in a U.S. adult population.

Cardiometabolic risk in adolescents: associations with physical activity, fitness, and sleep

BACKGROUND

Physical activity and fitness are independently associated with cardiometabolic dysfunction, and short sleep duration is an emerging marker of obesity. Few have examined interrelations among these factors in a comprehensive risk model.

PURPOSE

Investigate the influence of behavioral and lifestyle risk factors on the metabolic syndrome and inflammation.

METHODS

A sample of 367 15-17-year-olds (73 % boys) from ethnic minority groups (45.8 % Hispanic, 30.8 % Black), most with elevated blood pressure (72 %), underwent aerobic fitness testing, blood sampling, and completed behavioral questionnaires.

RESULTS

Structural model results are consistent with the notion that short sleep duration, poor sleep quality and fatigue, and decreased physical activity are associated with increased risk of metabolic syndrome and inflammation possibly via effects on reduced cardiorespiratory fitness.

CONCLUSIONS

The combination of negative lifestyle and behavioral factors of physical inactivity, sleep loss, and poor fitness has serious implications for cardiovascular health complications in at-risk youth.

Impact of OSA on biological markers in morbid obesity and metabolic syndrome

BACKGROUND AND OBJECTIVE

There is compelling evidence that obstructive sleep apnoea (OSA) can affect metabolic syndrome (MetS) and cardiovascular risk, but the intermediate mechanisms through which it occurs have not been well defined. We explored the impact of OSA in morbidly obese patients with MetS on adipokines, pro-inflammatory markers, endothelial dysfunction, and atherosclerosis markers.

METHODS

We included 52 morbidly obese patients in an observational study matched for age, gender and central obesity in 3 groups (OSA-MetS, Non-OSA-MetS, and Non OSA-non-MetS). Anthropometrical, blood pressure, and fasting blood measurements were obtained the morning after an overnight polysomnography. VEGF, soluble CD40 ligand (sCD40L), TNF-α, IL-6, leptin, adiponectin, and chemerin were determined in serum by ELISA. OSA was defined as apnea/ hypopnea index ≥ 15 and MetS by NCEP-ATP III.

RESULTS

Cases and control subjects did not differ in age, BMI, waist circumference, and gender (43 ± 10 years, 46 ± 5 kg/m(2), 128 ± 10 cm, 71% females). The cases had severe OSA with 47 (32-66) events/h, time spent < 90% SpO2 7% (5%-31%). All groups presented similar serum cytokines, adipokines, VEGF, and sCD40L levels.

CONCLUSIONS

In a morbidly obese population with established MetS, the presence of OSA did not determine any differences in the studied mediators when matched by central obesity. Morbidly obese NonOSA-NonMetS had a similar inflammatory, adipokine VEGF, and sCD40L profile as those with established MetS, with or without OSA. Obesity itself could overwhelm the effect of sleep apnea and MetS in the studied biomarkers.

CITATION

Salord N; Gasa M; Mayos M; Fortuna-Gutierrez AM; Montserrat JM; Sánchez-de-la-Torre M; Barceló A; Barbé F; Vilarrasa N; Monasterio C. Impact of OSA on biological markers in morbid obesity and metabolic syndrome.

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

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) has been linked to and is associated with increased cardiovascular and cerebrovascular morbidity. Ongoing inflammatory responses play an important role in this association. Multiple small size studies addressing the profile of the inflammatory markers in OSA are available therefore we performed a meta-analysis.

METHODS

Systematic review of medical literature was conducted using PubMed, Cochrane, and EMBASE databases from 1968 to 2011 by utilizing the key words obstructive sleep apnea, C-Reactive protein, tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), interleukin 8 (IL-8), intercellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM) and Selectins. Inclusion criteria were: full text English articles; studies with adult population; reported values for at least one of the markers of interest; with at least two separate groups (subjects with OSA and control group); OSA was defined as AHI of ≥ 5/h.

RESULTS

Five hundred and twelve studies were reviewed for inclusion with 51 studies pooled for analysis (30 studies for CRP, 19 studies for TNF-α, 8 studies for ICAM, 18 studies for IL-6, six studies for VCAM and 5 studies for Selectins). The levels of inflammatory markers were higher in patients with OSA compared to control group. Standardized pooled Mean differences were calculated to be 1.77 for CRP, 1.03 for TNF-α, 2.16 for IL-6, 4.22 for IL-8, 2.93 for ICAM, 1.45 for Selectins and 2.08 for VCAM.

CONCLUSIONS

In this meta-analysis, the levels of systemic inflammatory markers were found to be higher in OSA patients compared to control subjects.

Associations between change in sleep duration and inflammation: findings on C-reactive protein and interleukin 6 in the Whitehall II Study

Cross-sectional evidence suggests associations between sleep duration and levels of the inflammatory markers, C-reactive protein and interleukin-6. This longitudinal study uses data from the London-based Whitehall II study to examine whether changes in sleep duration are associated with average levels of inflammation from 2 measures 5 years apart. Sleep duration (≤5, 6, 7, 8, ≥9 hours on an average week night) was assessed in 5,003 middle-aged women and men in 1991/1994 and 1997/1999. Fasting levels of C-reactive protein and interleukin-6 were measured in 1997/1999 and 2002/2004. Cross-sectional analyses indicated that shorter sleep is associated with higher levels of inflammatory markers. Longitudinal analyses showed that each hour per night decrease in sleep duration between 1991/1994 and 1997/1999 was associated with higher levels of C-reactive protein (8.1%) and interleukin-6 (4.5%) averaged across measures in 1997/1999 and 2002/2004. Adjustment for longstanding illness and major cardiometabolic risk factors indicated that disease processes may partially underlie these associations. An increase in sleep duration was not associated with average levels of inflammatory markers. These results suggest that both short sleep and reductions in sleep are associated with average levels of inflammation over a 5-year period.

So depression is an inflammatory disease, but where does the inflammation come from?

BACKGROUND

We now know that depression is associated with a chronic, low-grade inflammatory response and activation of cell-mediated immunity, as well as activation of the compensatory anti-inflammatory reflex system. It is similarly accompanied by increased oxidative and nitrosative stress (O&NS), which contribute to neuroprogression in the disorder. The obvious question this poses is 'what is the source of this chronic low-grade inflammation?'

DISCUSSION

This review explores the role of inflammation and oxidative and nitrosative stress as possible mediators of known environmental risk factors in depression, and discusses potential implications of these findings. A range of factors appear to increase the risk for the development of depression, and seem to be associated with systemic inflammation; these include psychosocial stressors, poor diet, physical inactivity, obesity, smoking, altered gut permeability, atopy, dental cares, sleep and vitamin D deficiency.

SUMMARY

The identification of known sources of inflammation provides support for inflammation as a mediating pathway to both risk and neuroprogression in depression. Critically, most of these factors are plastic, and potentially amenable to therapeutic and preventative interventions. Most, but not all, of the above mentioned sources of inflammation may play a role in other psychiatric disorders, such as bipolar disorder, schizophrenia, autism and post-traumatic stress disorder.

Gender differences in the prospective associations of self-reported sleep quality with biomarkers of systemic inflammation and coagulation: findings from the Heart and Soul Study

Systemic inflammation is proposed as a putative mechanism underlying the link between poor sleep and cardiovascular disease. The aim of present study was to investigate the cross-sectional and prospective associations of self-reported sleep quality with biomarkers of inflammation and coagulation implicated in coronary heart disease (CHD) and to explore whether these associations differed between men and women. To this end, measures of sleep quality and markers of inflammation, including circulating levels of interleukin-6 (IL-6), high-sensitivity C-reactive protein (CRP), and fibrinogen were assessed at baseline in 980 participants with established CHD and 626 at 5-year follow-up. In the sample as a whole, subjective sleep quality was unrelated to inflammatory markers in cross-sectional and prospective analyses. However, in gender stratified analyses, adjusting for age, ethnicity, education, body mass index, and regular snoring, poorer subjective sleep quality at baseline was prospectively associated with 5-year increases in IL-6 (b = 0.14, SE = 0.05, p = 0.003), CRP (b = 0.21, SE = 0.09, p = 0.02), and fibrinogen (b = 18.02, SE = 7.62, p = 0.02) in women but not men. These associations remained independent of lifestyle/psychosocial factors, medical comorbidities, medication use, and cardiac function. Women who reported baseline sleep disturbances characterized by a tendency to wake up too early in the morning also showed significant 5-year increases in circulating IL-6 that withstood covariate adjustment. Further research is necessary to elucidate the pathways that underlie gender-specific associations between subjective sleep quality and markers of inflammation and coagulation as this may help clarify gender disparities in CHD.

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.

Association between short total sleep time and hypertension: the Skara Sleep Cohort

OBJECTIVES

Apnea hypopnea index (AHI) is used to study the association between obstructive sleep apnea (OSA) and hypertension, but the independent contributions of total sleep time (TST) and apnea/hypopnea event count to hypertension have not been previously investigated. We studied the relationship between polysomnographically assessed TST and hypertension in a sex-balanced community-dwelling cohort of hypertensive patients and normotensive controls (Skara Sleep Cohort).

METHODS

Participants (n = 344, men 173, age 61.2 ± 6.5 years, BMI 28.6 ± 4.8 kg/m, mean ± SD) underwent ambulatory home polysomnography. Hypertension was defined according to contemporary Swedish national guidelines. A multivariate logistic regression model was used to predict hypertension status from TST and apnea/hypopnea count (total events/night) adjusting for sex, age and BMI.

RESULTS

OSA was highly prevalent in this population (AHI 26 ± 4 events/h). Hypertensive patients had shorter TST than normotensive patients (353 ± 81 vs. 389 ± 65 min, P < 0.001), whereas total apnea/hypopnea count did not differ (167 ± 138 vs. 146 ± 148 events/night, P = 0.2). Multivariate logistic regression analysis revealed that short TST was associated with hypertension status [odds ratio 2.0; 95% confidence interval (95% CI) 1.2-3.3; P = 0.0015]. The significant association between apnea/hypopnea count and hypertension status was nonlinear (odds ratio 2.6; 95% CI 1.2-5.8; P = 0.04). The type of antihypertensive treatment was not found to significantly influence TST.

CONCLUSION

Short sleep time assessed by polysomnography was associated with hypertension in this community-dwelling population. Short sleep and presence of sleep apnea appear to independently link to hypertension.

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.

Epidemiological and Pathogenic Relationship between Sleep Apnea and Ischemic Heart Disease

Obstructive sleep apnea is recognized as having high prevalence and causing remarkable cardiovascular risk. Coronary artery disease has been associated with obstructive sleep apnea in many reports. The pathophysiology of coronary artery disease in obstructive sleep apnea patients probably includes the activation of multiple mechanisms, as the sympathetic activity, endothelial dysfunction, atherosclerosis, and systemic hypertension. Moreover, chronic intermittent hypoxia and oxidative stress have an important role in the pathogenesis of coronary disease and are also fundamental to the development of atherosclerosis and other comorbidities present in coronary artery diseases such as lipid metabolic disorders. Interestingly, the prognosis of patients with coronary artery disease has been associated with obstructive sleep apnea and the severity of sleep disordered breathing may have a direct relationship with the morbidity and mortality of patients with coronary diseases. Nevertheless, treatment with CPAP may have important effects, and recent reports have described the benefits of obstructive sleep apnea treatment on the recurrence of acute heart ischaemic events in patients with coronary artery disease.

Sleep duration and all-cause mortality: a critical review of measurement and associations

PURPOSE

Variation in sleep duration has been linked with mortality risk. The purpose of this review is to provide an updated evaluation of the literature on sleep duration and mortality, including a critical examination of sleep duration measurement and an examination of correlates of self-reported sleep duration.

METHODS

We conducted a systematic search of studies reporting associations between sleep duration and all-cause mortality and extracted the sleep duration measure and the measure(s) of association.

RESULTS

We identified 42 prospective studies of sleep duration and mortality drawing on 35 distinct study populations worldwide. Unlike previous reviews, we find that the published literature does not support a consistent finding of an association between self-reported sleep duration and mortality. Most studies have employed survey measures of sleep duration, which are not highly correlated with estimates based on physiologic measures.

CONCLUSIONS

Despite a large body of literature, it is premature to conclude, as previous reviews have, that a robust, U-shaped association between sleep duration and mortality risk exists across populations. Careful attention must be paid to measurement, response bias, confounding, and reverse causation in the interpretation of associations between sleep duration and mortality.

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.

Extreme sleep durations and increased C-reactive protein: effects of sex and ethnoracial group

STUDY OBJECTIVES

We hypothesize that extremes of sleep duration are associated with elevated C-reactive protein (CRP), a pro-inflammatory marker for cardiovascular disease risk.

DESIGN

Cross-sectional.

SETTING

Population-based research.

PARTICIPANTS

Nationally representative sample of 2007-2008 National Health and Nutrition Examination Survey participants (n = 5,587 adults).

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Associations between CRP and self-reported total sleep time (TST) were examined. Explanatory models considered contributions of sex, age, race/ethnicity, body mass index (BMI), and BMI squared (BMI2). Models also explored the role of insomnia symptoms, sleep apnea, active medical illness, and antidiabetic/antihypertensive treatment. Differential patterns among race/ethnicity groups were examined using interactions and stratified analyses. Nonlinear relationships between CRP and TST were assessed using polynomial and multinomial regression models (< 5, 5, 6, 7, 8, 9, and > 9 h). Linear and squared terms were significant in all models in the complete sample, with notable differences by sex and ethnoracial group. Overall, in models adjusted for sociodemographics and BMI, different patterns were observed for non-Hispanic white (elevated CRP for < 5 h and > 9 h), black/African-American (elevated CRP for < 5 h and 8 h), Hispanic/Latino (elevated CRP for > 9 h), and Asian/ Other (higher in 9 and > 9 h and lower in 5 h and 6 h) groups. Ethnoracial groups also demonstrated patterning by sex.

CONCLUSION

In a representative sample of American adults, elevated CRP was associated with extreme sleep durations. Sex, race/ethnicity, sleep disorders, and medical comorbidity influenced these associations. Differences in CRP along these dimensions should be considered in future research on sleep related disparities influencing cardiometabolic disease risk.

Sleep apnea modifies the long-term impact of surgically induced weight loss on cardiac function and inflammation

OBJECTIVE

Obesity is frequently associated with obstructive sleep apnea (OSA). Both conditions are proinflammatory and proposed to deteriorate cardiac function. We used a nested cohort study design to evaluate the long-term impact of bariatric surgery on OSA and how weight loss and OSA relate to inflammation and cardiac performance.

DESIGN AND METHODS

At 10-year follow-up in the Swedish Obese Subjects (SOS) study, we identified 19 obese subjects (BMI 31.2 ± 5.3 kg m(-2) ), who following bariatric surgery at SOS-baseline had displayed sustained weight losses (surgery group), and 20 obese controls (BMI 42.0 ± 6.2 kg m(-2) ), who during the same time-period had maintained stable weight (control group). All study participants underwent overnight polysomnography examination, echocardiography and analysis of inflammatory markers.

RESULTS

The surgery group displayed a lower apnea hypopnea index (AHI) (19.9 ± 21.5 vs. 37.8 ± 27.7 n/h, P = 0.013), lower inflammatory activity (hsCRP 2.3 ± 3.0 vs. 7.2 ± 5.0 mg L(-1) , P < 0.001), reduced left ventricular mass (165 ± 22 vs. 207 ± 22 g, P < 0.001) and superior left ventricular diastolic function (E/A ratio 1.24 ± 1.10 vs. 1.05 ± 0.20, P = 0.006) as compared with weight stable obese controls. In multiple regression analyses including all subjects (n = 39) and controlling for BMI, the AHI remained independently associated with hsCRP (β = 0.09, P < 0.001), TNF-α (β = 0.03, P = 0.031), IL-6 (β = 0.01, P = 0.007), IL 10 (β = -0.06; P = 0.018), left ventricular mass (β = 0.64, P < 0.001), left atrial area (β = 0.08, P = 0.002), pulmonary artery pressure (β = 0.08, P = 0.011) and E/Ea ratio (β = 0.04, P = 0.021).

CONCLUSIONS

Patients with sustained weight loss after bariatric surgery display less severe sleep apnea, reduced inflammatory activity, and enhanced cardiac function. Persisting sleep apnea appears to limit the beneficial effect of weight loss on inflammation and cardiac performance.

Profile of circulating cytokines: impact of OSA, obesity and acute cardiovascular events

Obstructive sleep apnea (OSA) is inducing oxidative stress and consequently promotes systemic inflammation and cardiovascular morbidity. The respective impact of obesity, sleep apnea and acute cardiovascular events on the profile of inflammatory cytokines has not been extensively evaluated. We examined the profile of circulating cytokines in a case-control study comparing nonobese or obese patients with or without sleep apnea and with or without an acute cardiovascular event. Patients were assessed by sleep studies and inflammatory (hs-CRP, Leptin, RANTES, MCP1, IL6, IL8, TNF-α) and anti-inflammatory (adiponectin, IL1-Ra) cytokines profile. A cardiovascular phenotyping was performed including carotid intima-media thickness, pulse wave velocity and 24h blood pressure monitoring. In comparison with patients without sleep apnea or without comorbidities, patients with the combination of an acute cardiovascular event and pre-existing sleep apnea showed a higher burden of systemic inflammation with significant increase in serum levels of hs-CRP, IL1-Ra, IL-8, IL-6, TNF-α, Rantes and sICAM. Rantes and sICAM serum levels were independently associated with AHI after an acute cardiovascular event. Serum levels of different inflammatory markers were significantly increased in patients with the combination of sleep apnea and an acute cardiovascular event. Since these biomarkers could be associated with worsened cardiovascular outcome, diagnosing and treating associated sleep apnea is potentially important in patients after an acute cardiovascular event.

Hypertension and obstructive sleep apnea

Obstructive sleep apnea (OSA) is increasingly being recognized as a major health burden with strong focus on the associated cardiovascular risk. Studies from the last two decades have provided strong evidence for a causal role of OSA in the development of systemic hypertension. The acute physiological changes that occur during apnea promote nocturnal hypertension and may lead to the development of sustained daytime hypertension via the pathways of sympathetic activation, inflammation, oxidative stress, and endothelial dysfunction. This review will focus on the acute hemodynamic disturbances and associated intermittent hypoxia that characterize OSA and the potential pathophysiological mechanisms responsible for the development of hypertension in OSA. In addition the epidemiology of OSA and hypertension, as well as the role of treatment of OSA, in improving blood pressure control will be examined.

Sleep duration, cardiovascular disease, and proinflammatory biomarkers

Habitual sleep duration has been associated with cardiometabolic disease, via several mechanistic pathways, but few have been thoroughly explored. One hypothesis is that short and/or long sleep duration is associated with a proinflammatory state, which could increase risk for cardiovascular and metabolic diseases. This hypothesis has been largely explored in the context of experimental sleep deprivation studies which have attempted to demonstrate changes in proinflammatory markers following acute sleep loss in the laboratory. Despite the controlled environment available in these studies, samples tend to lack generalization to the population at large and acute sleep deprivation may not be a perfect analog for short sleep. To address these limitations, population based studies have explored associations between proinflammatory markers and habitual sleep duration. This review summarizes what is known from experimental and cross-sectional studies about the association between sleep duration, cardiovascular disease, and proinflammatory biomarkers. First, the association between sleep duration with both morbidity and mortality, with a focus on cardiovascular disease, is reviewed. Then, a brief review of the potential role of proinflammatory markers in cardiovascular disease is presented. The majority of this review details specific findings related to specific molecules, including tumor necrosis factor-α, interleukins-1, -6, and -17, C-reactive protein, coagulation molecules, cellular adhesion molecules, and visfatin. Finally, a discussion of the limitations of current studies and future directions is provided.

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.

Obesity, obstructive sleep apnoea and metabolic syndrome

OSA is increasingly recognized as a major health problem in developed countries. Obesity is the most common risk factor in OSA and hence, the prevalence of OSA is undoubtedly rising given the epidemic of obesity. Recent data also suggest that OSA is highly associated with the metabolic syndrome, and it is postulated that OSA contributes to cardiometabolic dysfunction, and subsequently vasculopathy. Current evidence regarding the magnitude of impact on ultimate cardiovascular morbidity or mortality attributable to OSA-induced metabolic dysregulation is scarce. Given the known pathophysiological triggers of intermittent hypoxia and sleep fragmentation in OSA, the potential mechanisms of OSA-obesity-metabolic syndrome interaction involve sympathetic activation, oxidative stress, inflammation and neurohumoral changes. There is accumulating evidence from human and animal/cell models of intermittent hypoxia to map out these mechanistic pathways. In spite of support for an independent role of OSA in the contribution towards metabolic dysfunction, a healthy diet and appropriate lifestyle modifications towards better control of metabolic function are equally important as CPAP treatment in the holistic management of OSA.

Association of inflammatory markers with cardiovascular risk and sleepiness

There is emerging evidence suggesting that disturbances in sleep and sleep disorders play a role in the morbidity of chronic conditions including obesity and hypertension as well as in the development of type-2 diabetes. This brief review examines the role of inflammation in the development of atherosclerosis. Furthermore, it outlines the utility of inflammatory markers and, in particular, adhesion molecules as biomarkers for cardiovascular risk and the factors that affect their level in the circulation. It then discusses the relationship between sleep and markers of inflammation and the role of sleep in immune function.

Elevated serum C-reactive protein and markers of sleep disordered breathing

Background. Previous studies indicated sleep-disordered breathing (SDB) is associated with cardiovascular disease (CVD). Systemic inflammation is recognized as a risk factor for CVD. Studies examining SDB and inflammation are limited. Methods. We studied sleep duration, snoring, snorting, and daytime sleepiness, and an additive SDB score. The main outcome was a C-reactive protein (CRP) of >1 mg/dL. Results. Snoring, snorting, daytime sleepiness, and sleeping >7 or <7 hours, and the additive score were significantly associated with high CRP. The additive score was not associated in men but moderately associated in women in a multivariable model adjusting for age, gender, race/ethnicity, education, smoking, hypertension, alcohol intake, physical activity, body mass index, depression, diabetes, hypertension, and total cholesterol (P-interaction  = 0.42). For race/ethnicity, the association was strongest in Mexican Americans/others, modest in Non-Hispanic whites, and absent in Non-Hispanic blacks (P-interaction  = 0.07). Conclusions. The association between SDB and high CRP was present mainly in women and Mexican Americans, implying SDB has a residual, independent association with inflammation after controlling for lifestyle and metabolic risk factors like BMI, physical activity, depression, diabetes, and cholesterol.

Associations of sleep disturbance and duration with metabolic risk factors in obese persons with type 2 diabetes: data from the Sleep AHEAD Study

PURPOSE

Some studies have found an association between sleep disturbances and metabolic risk, but none has examined this association in individuals with type 2 diabetes. The objective of this study was to determine the relationship between sleep disturbances and metabolic risk factors in obese patients with type 2 diabetes.

PATIENTS AND METHODS

This study was a cross-sectional examination of the relationship between sleep parameters (apnea/hypopnea index [AHI], time spent in various sleep stages) and metabolic risk markers (fasting glucose, hemoglobin A1c, lipids) using baseline data of the Sleep AHEAD cohort. Subjects (n = 305) were participants in Sleep AHEAD (Action for Health in Diabetes), a four-center ancillary study of the Look AHEAD study, a 16-center clinical trial of overweight and obese participants with type 2 diabetes, designed to assess the long-term effects of an intensive lifestyle intervention on cardiovascular events. All participants underwent one night of in-home polysomnography and provided a fasting blood sample. Regression analyses estimated the relationship between sleep variables and metabolic risk factors. Models were adjusted for study center, age, sex, race/ethnicity, waist circumference, smoking, alcohol intake, diabetes duration, and relevant medications.

RESULTS

Of 60 associations tested, only one was significant: fasting glucose was associated with sleep efficiency (estimate -0.53 ± [standard error] 0.26, P = 0.041). No associations were found between any of the sleep variables and lipid profile or hemoglobin A1c.

CONCLUSIONS

The present data show only weak associations between select sleep variables and metabolic risk factors and do not provide strong support for a role of sleep on metabolic abnormalities in obese patients with type 2 diabetes.

Snoring, inflammatory markers, adipokines and metabolic syndrome in apparently healthy Chinese

OBJECTIVE

Chronic low-grade inflammation and adipokines dysregulation are linked to mechanisms underscoring the pathogenesis of obesity-related metabolic disorders. Little is known about roles of these cytokines on the association between snoring and metabolic syndrome (MetS). We aimed to investigate whether a cluster of cytokines are related to snoring frequency and its association with MetS in apparently healthy Chinese.

METHODS

Current analyses used a population-based sample including 1059 Shanghai residents aged 35-54 years. Self-reported snoring frequency was classified as never, occasionally and regularly. Fasting plasma glucose, lipid profile, insulin, C-reactive protein, interleukin-6, interleukin-18, lipopolysaccharide binding protein, high-molecular-weight adiponectin and leptin were measured. MetS was defined by the updated National Cholesterol Education Program Adult Treatment Panel III criteria for Asian-Americans.

RESULTS

Overweight/obese subjects had significantly higher prevalence of regular snorers than their normal-weight counterparts (34.8% vs. 11.5%, P<0.001). Regular snoring was associated with unfavorable profile of inflammatory markers and adipokines. However, those associations were abolished after adjustment for body mass index (BMI) or waist circumference. The MetS risk (multivariate-adjusted odds ratio 5.41, 95% confidence interval 3.72-7.88) was substantially higher in regular snorers compared with non-snorers. Controlling for BMI remarkably attenuated the association (2.03, 1.26-3.26), while adjusting for inflammatory markers and adipokines showed little effects.

CONCLUSION

Frequent snoring was associated with an elevated MetS risk independent of lifestyle factors, adiposity, inflammatory markers and adipokines in apparently healthy Chinese. Whether snoring pattern is an economic and no-invasive indicator for screening high-risk persons needs to be addressed prospectively.