An update on obstructive sleep apnea and the metabolic syndrome

Pathogenesis of Hypertension in Metabolic Syndrome: The Role of Fructose and Salt

Metabolic syndrome is manifested by visceral obesity, hypertension, glucose intolerance, hyperinsulinism, and dyslipidemia. According to the CDC, metabolic syndrome in the US has increased drastically since the 1960s leading to chronic diseases and rising healthcare costs. Hypertension is a key component of metabolic syndrome and is associated with an increase in morbidity and mortality due to stroke, cardiovascular ailments, and kidney disease. The pathogenesis of hypertension in metabolic syndrome, however, remains poorly understood. Metabolic syndrome results primarily from increased caloric intake and decreased physical activity. Epidemiologic studies show that an enhanced consumption of sugars, in the form of fructose and sucrose, correlates with the amplified prevalence of metabolic syndrome. Diets with a high fat content, in conjunction with elevated fructose and salt intake, accelerate the development of metabolic syndrome. This review article discusses the latest literature in the pathogenesis of hypertension in metabolic syndrome, with a specific emphasis on the role of fructose and its stimulatory effect on salt absorption in the small intestine and kidney tubules.

Obstructive sleep apnoea-hypopnoea syndrome: state of the art

Obstructive sleep apnoea-hypopnoea syndrome (OSAHS) is an extremely common sleep-related breathing disorder (SRBD) characterised by complete or partial collapse of the upper airways. These nocturnal phenomena cause high-frequency hypoxemic desaturations (or intermittent hypoxia, IH) during sleep and alterations in gas exchange. The result of IH is the development or worsening of cerebro-cardio-vascular, metabolic and other diseases, which cause a high risk of death. Hence, OSAHS is a multifactorial disease affecting several organs and systems and presenting with various clinical manifestations involving different medical branches. Although it has been estimated that about one billion individuals worldwide are affected by OSAHS, this SRBD remains underestimated also due to misinformation regarding both patients and physicians. Therefore, this review aims to provide information on the main symptoms and risk factors for the detection of individuals at risk of OSAHS, as well as to present the diagnostic investigations to be performed and the different therapeutic approaches. The scientific evidence reported suggest that OSAHS is an extremely common and complex disorder that has a large impact on the health and quality of life of individuals, as well as on healthcare expenditure. Moreover, given its multifactorial nature, the design and implementation of diagnostic and therapeutic programmes through a multidisciplinary approach are necessary for a tailor-made therapy for each patient.

The relationship between metabolic syndrome and obstructive sleep apnea syndrome: a nationwide population-based study

There has been a need for research on the association between metabolic syndrome (MetS) and obstructive sleep apnea syndrome (OSAS) using large data such as nationwide population-based data that adjusts important confounding factors. Therefore, we investigated the relationship between MetS and OSAS. The data source we used was the National Health Insurance Service claims database managed by the Republic of Korea government, in which 10,113,560 individuals were enrolled in 2009 and followed up until 2018. The independent association of MetS with the risk of OSAS was determined using a Cox proportional hazards model with adjustment for age, sex, smoking status, alcohol consumption, regular physical exercise, and body mass index. Our results showed that MetS were strongly associated to OSAS which was adjusted for several confounding factors. Also, we found men, increased waist circumference and increased triglyceride are important risk factors for OSAS.

Changes of aldosterone levels in patients with type 2 diabetes complicated by moderate to severe obstructive sleep apnea-hypopnea syndrome before and after treatment with continuous positive airway pressure

Objective

Both obstructive sleep apnea–hypopnea syndrome (OSAHS) and type 2 diabetes mellitus (T2DM) are closely related to the renin-angiotensin-aldosterone system. We investigated whether hyperaldosteronemia is found in patients with OSAHS complicated by T2DM and whether continuous positive airway pressure (CPAP) treatment can significantly reduce the aldosterone level.

Methods

Patients with T2DM were classified into an OSAHS group [apnea–hypopnea index (AHI) of ≥15] and a control group (without OSAHS; AHI of <5). The OSAHS group was exposed to CPAP for 7 days (7 h/day).

Results

The plasma aldosterone, plasma renin, and urinary aldosterone levels were higher in the OSAHS than control group. The plasma aldosterone and renin levels were significantly lower after than before treatment in the OSAHS group, but they were still higher than the baseline levels in the control group. The post-treatment urinary aldosterone level was significantly higher in the OSAHS than control group. No correlation was found between the AHI and plasma renin, plasma aldosterone, and 24-hour urinary aldosterone levels. The blood glucose level in the OSAHS group did not significantly change after treatment.

Conclusions

The plasma and urine aldosterone levels are increased in patients with concurrent T2DM and OSAHS and are significantly reduced by CPAP.

Trial registration: ChiCTR-ION-16009837

Economical lipid production from Trichosporon oleaginosus via dissolved oxygen adjustment and crude glycerol addition

The effect of dissolved oxygen concentration on lipid accumulation in Trichosporon oleaginosus has been investigated. The experiment was performed in 15 L fermenters. The dissolved oxygen concentration varied by adjusting the agitation and aeration. High dissolved oxygen level at 50%-60% enhanced cell growth. Maintaining low dissolved oxygen concentration at 20%-30% during lipogenesis phase led to high final lipid content (51%) in Trichosporon oleaginosus. The consumptions of energy and cost of the process were evaluated. The energy consumption in the dissolved oxygen level optimized process was 41% less than that with dissolved oxygen level at 50%-60%. In addition, the cost was also reduced around one time in the dissolved oxygen level optimized process compared to the one with dissolved oxygen level at 50%-60%. The study provided a feasible way of enhancing lipid accumulation in Trichosporon oleaginosus and reducing the consumption of energy and cost of lipid production from Trichosporon oleaginosus.

Online Obstructive Sleep Apnea Detection on Medical Wearable Sensors

Obstructive Sleep Apnea (OSA) is one of the main under-diagnosed sleep disorder. It is an aggravating factor for several serious cardiovascular diseases, including stroke. There is, however, a lack of medical devices for long-term ambulatory monitoring of OSA since current systems are rather bulky, expensive, intrusive, and cannot be used for long-term monitoring in ambulatory settings. In this paper, we propose a wearable, accurate, and energy efficient system for monitoring obstructive sleep apnea on a long-term basis. As an embedded system for Internet of Things, it reduces the gap between home health-care and professional supervision. Our approach is based on monitoring the patient using a single-channel electrocardiogram signal. We develop an efficient time-domain analysis to meet the stringent resources constraints of embedded systems to compute the sleep apnea score. Our system, for a publicly available database (PhysioNet Apnea-ECG), has a classification accuracy of up to 88.2% for our new online and patient-specific analysis, which takes the distinct profile of each patient into account. While accurate, our approach is also energy efficient and can achieve a battery lifetime of 46 days for continuous screening of OSA.

Psoriasis and obstructive sleep apnea

BACKGROUND

Psoriasis is a chronic inflammatory skin disorder that is associated with the metabolic syndrome and its components. An association between obstructive sleep apnea (OSA) and the metabolic syndrome was previously observed.

OBJECTIVES

To investigate the association between psoriasis and OSA in a comprehensive community-based database.

MATERIALS AND METHODS

The study was performed utilizing the medical database of Clalit Health Services. Patients with psoriasis were compared to controls regarding the prevalence of OSA in a case-control study. A logistic multivariate model was used to control for independent covariates.

RESULTS

The study included 12,336 patients with psoriasis ≥21 years and 24,008 age- and sex-matched controls. The prevalence of OSA in patients with psoriasis was increased compared to the control group (2.7%, 1.5%, respectively, P < 0.001). Multivariate analysis adjusting for age, sex, ethnicity, body mass index, chronic obstructive pulmonary disease, hypothyroidism, hyperlipidemia, and peptic disease demonstrated a significant association between psoriasis and OSA (odds ratio = 1.27, 95% confidence interval 1.08-1.49, P < 0.001).

CONCLUSION

We found an association between psoriasis and OSA among a large cohort of patients with psoriasis. Clinicians should take into account that patients with psoriasis may have undiagnosed OSA.

Self-reported obstructive sleep apnea, simple snoring, and various markers of sleep-disordered breathing as predictors of cardiovascular risk

PURPOSE

Our objective was to investigate whether self-reported obstructive sleep apnea (OSA), simple snoring, and various markers of sleep-disordered breathing (SDB) are associated with cardiovascular risk.

METHODS

We examined a representative nationwide cohort of 5177 Finnish adults aged ≥30 years. The participants underwent measurement of traditional cardiovascular risk factors and answered SDB-related questions derived from the Basic Nordic Sleep Questionnaire, which were used to operationalize self-reported OSA. The primary end point was incidence of a cardiovascular event (cardiovascular mortality, non-fatal myocardial infarction, non-fatal stroke, hospitalization for heart failure, or coronary interventions).

RESULTS

During a median follow-up of 11.2 years and 52,910 person-years of follow-up, 634 participants suffered a cardiovascular event. In multivariable-adjusted Cox models, self-reported OSA (hazard ratio [HR] 1.34; 95 % confidence interval [CI] 1.04-1.73; p = 0.03) was an independent predictor of cardiovascular events. Self-reported simple snoring by itself was not associated with future cardiovascular events (HR 0.88 versus non-snorers, 95 % CI 0.75-1.04, p = 0.15). However, among snorers (n = 3152), frequent breathing cessations (HR 2.19, 95 % CI 1.26-3.81, p = 0.006) and very loud and irregular snoring (HR 1.82, 95 % CI 1.31-2.54, p < 0.001) were associated with cardiovascular risk.

CONCLUSIONS

Self-reported OSA and SDB-related snoring variables are associated with cardiovascular risk, whereas simple snoring is not. In clinical practice and in surveys, questions concerning only habitual snoring should be amended with questions focusing on respiratory pauses and snoring stertorousness, which can be used to estimate the risk of OSA and cardiovascular events.

Insulin resistance in moderate to severe obstructive sleep apnea in nondiabetics and its response to continuous positive airway pressure treatment

Background:

The effects of nasal continuous positive airway pressure (CPAP) on insulin resistance (IR) in obstructive sleep apnea (OSA) are still under discussion especially in nondiabetics. Trials have found conflicting results in this regard.

Aims:

The study was to measure IR in nondiabetic patients with moderate to severe OSA and to evaluate the effect of nasal CPAP on IR in these patients.

Materials and Methods:

A total of 30 consecutively newly diagnosed patients with moderate to severe OSA was enrolled in the study. OSA was diagnosed by doing an overnight polysomnography. Plasma glucose and insulin levels were measured at baseline and after 1 month of CPAP treatment. IR was calculated by homeostasis model assessment (HOMA) method.

Results:

Of 30 OSA patients, 21 were males, and 9 were females. The mean age of the subjects was 49.9 years, and mean body mass index (BMI) was 29.33. All 30 patients had moderate to severe OSA with a mean apnea and hypopnea index (AHI) of 80.46/h. The Epworth sleepiness score (ESS) showed a significant change with 1 month of treatment with CPAP from baseline of 13 to 9.7 (P ≤ 0.0001). There was a significant reduction in fasting insulin levels from 21.75 to 19.39 (P = 0.009). There was a small fall in fasting glucose, but it was not significant. The HOMA IR also reduced from 5.78 to 4.82 which was significant (P = 0.024) without any significant change in BMI (P = 0.916). The HOMA IR did not showed any positive correlation with different variables of OSA severity, ESS (r = 0.156) (P = 0.410), AHI (r = 0.177) (P = 0.349), and percentage of test time <90% saturation (r = −0.296) (P = 0.112).

Conclusion:

Moderate to severe OSA is associated with an increase in IR and effective treatment with CPAP rapidly improves the insulin sensitivity in nondiabetic patients with OSA without any change in BMI.

Circadian clock desynchronisation and metabolic syndrome

There is emerging evidence in the literature to suggest that disruption of the normal circadian rhythm (sleep-wake cycle signalling) is a potential risk factor to explain the increased incidence of metabolic syndrome. Over the last century, obesity, diabetes and other components of metabolic syndrome have been on the rise. On the other hand, the amount of sleep has decreased from an average of 6-8 h per night. Furthermore, the quality of sleep has declined with more individuals voluntarily decreasing their amount of sleep to work or enjoy leisure activities. Over the last decade, researchers have examined the relationship between disruption in human circadian system and the emergence of symptoms related to metabolic syndrome. Indeed, epidemiological studies suggest a relation between sleep duration and diabetes and obesity. Moreover, experimental animal and human studies suggest such a relation. These studies propose optimum sleep duration of 7-8 h per night to avoid circadian rhythm disruption and suggest that sleep disturbance, whether iatrogenic or disease-related, should be considered as a risk factor for metabolic syndrome, and be addressed. This field is in its infancy and further understanding of specific pathophysiological pathways of circadian desynchronisation will help in developing novel preventive and therapeutic strategies.

Sleep apnoea adversely affects the outcome in patients who undergo posterior lumbar fusion: a population-based study

Despite the increasing prevalence of sleep apnoea, little information is available regarding its impact on the peri-operative outcome of patients undergoing posterior lumbar fusion. Using a national database, patients who underwent lumbar fusion between 2006 and 2010 were identified, sub-grouped by diagnosis of sleep apnoea and compared. The impact of sleep apnoea on various outcome measures was assessed by regression analysis. The records of 84,655 patients undergoing posterior lumbar fusion were identified and 7.28% (n = 6163) also had a diagnostic code for sleep apnoea. Compared with patients without sleep apnoea, these patients were older, more frequently female, had a higher comorbidity burden and higher rates of peri-operative complications, post-operative mechanical ventilation, blood product transfusion and intensive care. Patients with sleep apnoea also had longer and more costly periods of hospitalisation. In the regression analysis, sleep apnoea emerged as an independent risk factor for the development of peri-operative complications (odds ratio (OR) 1.50, confidence interval (CI) 1.38;1.62), blood product transfusions (OR 1.12, CI 1.03;1.23), mechanical ventilation (OR 6.97, CI 5.90;8.23), critical care services (OR 1.86, CI 1.71;2.03), prolonged hospitalisation and increased cost (OR 1.28, CI 1.19;1.37; OR 1.10, CI 1.03;1.18). Patients with sleep apnoea who undergo posterior lumbar fusion pose significant challenges to clinicians.

Relationship between aldosterone and the metabolic syndrome in patients with obstructive sleep apnea hypopnea syndrome: effect of continuous positive airway pressure treatment

Background

Metabolic syndrome (MS) occurs frequently in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). We hypothesized that aldosterone levels are elevated in OSAHS and associated with the presence of MS.

Methods

We studied 66 patients with OSAHS (33 with MS and 33 without MS) and 35 controls. The occurrence of the MS was analyzed according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) clinical criteria. Measurements of plasma renin activity (PRA), aldosterone, aldosterone:PRA ratio, creatinine, glucose, triglycerides, cholesterol and HDL cholesterol were obtained at baseline and after CPAP treatment.

Results

Aldosterone levels were associated with the severity of OSAHS and higher than controls (p = 0.046). Significant differences in aldosterone levels were detected between OSAHS patients with and without MS (p = 0.041). A significant reduction was observed in the aldosterone levels in patients under CPAP treatment (p = 0.012).

Conclusion

This study shows that aldosterone levels are elevated in OSAHS in comparison to controls, and that CPAP therapy reduces aldosterone levels. It also shows that aldosterone levels are associated with the presence of metabolic syndrome, suggesting that aldosterone excess might predispose or aggravate the metabolic and cardiovascular complications of OSAHS.

Trial registration

The study is not a randomized controlled trial and was not registered.

The history of sleep apnea is associated with shorter leukocyte telomere length: the Helsinki Birth Cohort Study

OBJECTIVES

Sleep apnea poses an elevated risk for chronic age-related diseases. Leukocyte telomere length (LTL), a biomarker and factor associated with accelerated cellular aging processes, may serve as a novel mechanism underlying these disease risks. We investigated if a history of clinician-diagnosed sleep apnea or primary snoring was associated with LTL in later adulthood.

METHODS

Data on sleep apnea, primary snoring and LTL, were available for 1948 participants from the Helsinki Birth Cohort Study. Patients with sleep apnea (n=44) and primary snoring (n=29) severe enough to be recorded as an inpatient diagnosis for hospitalization were identified by their case records through the Finnish Hospital Discharge Register. The LTL was measured by using the realtime quantitative polymerase chain reaction (PCR) method at a mean age of 61.5 years (standard deviation [SD], 2.9).

RESULTS

A history of sleep apnea was associated with shorter LTL (P=.010). Adjustment for a number of covariates did not alter the association.

CONCLUSIONS

Accelerated cellular aging reflected in shorter LTL in patients with a history of sleep apnea may partly explain their higher risk for age-related diseases. Future studies elucidating the impacts of long-term or successful treatment history of sleep apnea on the maintenance of LTL are warranted.

Obstructive sleep apnea and metabolic syndrome in spanish population

Obstructive sleep apnea (OSA) is a clinical picture characterized by repeated episodes of obstruction of the upper airway. OSA is associated with cardiovascular risk factors, some of which are components of metabolic syndrome (MS).

OBJECTIVES

First, determine the prevalence of MS in patients with OSA visited in sleep clinic. Second, evaluate whether there is an independent association between MS components and the severity of OSA.

METHODS

Patients with clinical suspicion of OSA were evaluated by polysomnography. Three groups were defined according to apnea hypoapnea index (AHI): no OSA (AHI <5), mild-moderate (AHI≥ 5 ≤30), and severe (AHI> 30). All patients were determined in fasting blood glucose, total cholesterol, HDL cholesterol, triglycerides and insulin. MS was defined according to criteria of National Cholesterol Education Program (NCEP).

RESULTS

A total of 141 patients (mean age 54 ± 11 years) were evaluated. According to AIH, 25 subjects had no OSA and 116 had OSA (41mild-moderate and 75 severe). MS prevalence ranged from 43-81% in OSA group. Also, a significant increase in waist circumference, triglycerides, glucose, blood pressure levels, and a decrease in HDL cholesterol levels was observed in more severe OSA patients. All polysomnographic parameters correlated significantly with metabolic abnormalities. After a multiple regression analysis, abdominal obesity (p <0.02), glucose (p <0.01) and HDL cholesterol (p <0.001) were independently associated with OSA.

CONCLUSIONS

Our findings show high prevalence of MS in OSA, especially in severe group. A significant association between OSA and some of the components of MS was found in Spanish population.

Morbidities associated with obstructive sleep apnea

Obstructive sleep apnea (OSA)-induced biological changes include intermittent hypoxia, intermittent hypercapnia, intrathoracic pressure changes, sympathetic activation and sleep fragmentation. OSA can cause metabolic dysregulation, endothelial dysfunction, systemic inflammation, oxidative stress and hypercoagulation, and neurohumoral changes. There is evidence suggesting that OSA is independently associated with metabolic syndrome. OSA has been shown to increase the risk for systemic hypertension, pulmonary vascular disease, ischemic heart disease, cerebral vascular disease, congestive heart failure and arrhythmias. Although there are evidences accumulating that there may be a causal relationship between OSA and cardiovascular disorders, there is a need for more data from randomized controlled intervention trials to confirm this relationship. Many risk factors of OSA (age, male gender and obesity) are also known risk factors for cardiovascular disease. Severe OSA-hypopnea significantly increases the risk of fatal and nonfatal cardiovascular events in both men and women, and continuous positive airway pressure treatment reduces this risk in both. Neurocognitive consequences of OSA include daytime sleepiness, loss of alertness, memory deficit, reduced vigilance, impaired executive function, increased risk for automobile and occupational accidents, and decreased quality of life.

Obesity hypoventilation syndrome

Obesity is becoming a major medical concern in several parts of the world, with huge economic impacts on health- care systems, resulting mainly from increased cardiovascular risks. At the same time, obesity leads to a number of sleep-disordered breathing patterns like obstructive sleep apnea and obesity hypoventilation syndrome (OHS), leading to increased morbidity and mortality with reduced quality of life. OHS is distinct from other sleep- related breathing disorders although overlap may exist. OHS patients may have obstructive sleep apnea/hypopnea with hypercapnia and sleep hypoventilation, or an isolated sleep hypoventilation. Despite its major impact on health, this disorder is under-recognized and under-diagnosed. Available management options include aggressive weight reduction, oxygen therapy and using positive airway pressure techniques. In this review, we will go over the epidemiology, pathophysiology, presentation and diagnosis and management of OHS.

APAP impact on metabolic syndrome in obstructive sleep apnea patients

PURPOSE

Prevalence of metabolic syndrome (MS) in obstructive sleep apnea (OSA) patients is high. The effect of autoadjusting positive airway pressure (APAP) on MS remains unclear. This study aimed to determine the prevalence of MS in OSA patients before and 6 months after APAP, and to identify potential determinants of metabolic status change.

METHODS

Seventy-four male patients with moderate to severe OSA were enrolled. MS diagnosis was established according to the National Cholesterol Education Program/Adult Treatment Panel III. APAP was prescribed to all patients.

RESULTS

In the studied population, mean age was 55.9 years (SD 10.7 years), median body mass index (BMI), Epworth sleepiness scale (ESS), and respiratory disturbance index (RDI) were 33.4 kg/m(2) (interquartile range (IQR) 8.4 kg/m(2)), 12.0 (IQR 8.0), and 46.9/h (IQR 33.6/h), respectively. Prevalence of MS before and 6 months after APAP was 63.5% and 47.3%, respectively, and this difference was statistically significant (p = 0.004). In the subgroup of patients with MS at baseline (n = 47), 14 did not present MS after APAP. In these patients, a significant negative association with RDI (p = 0.016) and a positive association with percent of total days of usage (p = 0.014) were found. Blood pressure (p = 0.018) and serum triglycerides (p = 0.001) had a statistically significant reduction during this period. In patients that still had MS, 22.2% presented a reduction of the number of MS criteria.

CONCLUSIONS

After 6 months, APAP reduced the prevalence of MS, mainly in patients with less severe OSA and with a better therapeutic compliance. Blood pressure and serum triglycerides reduction contributed to this metabolic status change.

Sex differences in the association of regional fat distribution with the severity of obstructive sleep apnea

STUDY OBJECTIVES

To describe sex differences in the associations between severity of obstructive sleep apnea (OSA) and measures of obesity in body regions defined using both dual-energy absorptiometry and traditional anthropometric measures in a sleep-clinic sample.

DESIGN

A prospective case-series observational study.

SETTING

The Western Australian Sleep Health Study operating out of the Sir Charles Gairdner Hospital Sleep Clinic, Perth, Western Australia.

PARTICIPANTS

Newly referred clinic patients (60 men, 36 women) suspected of having OSA.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Obstructive sleep apnea severity was defined by apnea-hypopnoea index from laboratory-based overnight polysomnography. Body mass index, neck, waist and hip circumference, neck-to-waist ratio, and waist-to-hip ratio were measured. Dual energy absorptiometry measurements included percentage fat and lean tissue. Multivariate regression models for each sex were developed. In women, percentage of fat in the neck region and body mass index together explained 33% of the variance in apnea-hypopnea index. In men, percentage of fat in the abdominal region and neck-to-waist ratio together accounted for 37% of the variance in apnea-hypopnea index.

CONCLUSIONS

Regional obesity is associated with obstructive sleep apnea severity, although differently in men and women. In women, a direct influence of neck fat on the upper airway patency is implicated. In men, abdominal obesity appears to be the predominant influence. The apnea-hypopnea index was best predicted by a combination of Dual Energy Absorptiometry-measured mass and traditional anthropometric measurements.

Telomere shortening in sleep apnea syndrome

BACKGROUND

Telomere length (TL) in circulating leukocytes relates to the chronological age of the individual but it is believed to reflect also the cumulative burden of oxidative stress and inflammation over the life-time. Shortening of TL has been reported in several chronic conditions characterized by oxidative stress and inflammation, such as diabetes and atherosclerosis. Because these conditions also occur in patients with Obstructive Sleep Apnea Syndrome (OSAS), we hypothesized that TL would be reduced in patients with OSAS.

METHODS

We compared TL in 256 patients with OSAS and 148 controls without OSAS. We also investigated if TL was related to the severity of OSAS, the presence of metabolic disorders and/or cardiovascular risk factors in these patients.

RESULTS

TL was significantly shorter in patients with OSAS than in controls (p<0.001). This difference persisted after adjustment for age, body mass index, cholesterol, triglycerides, glucose, and uric acid levels, smoking status and the presence of arterial hypertension (p=0.018). TL was not related to the severity of OSAS as assessed by the apnea-hypopnea index, nocturnal oxygen saturation and daytime sleepiness.

CONCLUSIONS

TL in circulating leukocytes is shorter in patients with OSAS than subjects without OSAS. The mechanism of this observation is unresolved since it appears independent of chronological age, the severity of OSAS and/or the presence of cardiovascular or metabolic alterations but the potential utility of TL as a biomarker of increased cardiovascular risk in these patients justifies further studies.

Day/Night rhythm of hemostatic factors in obstructive sleep apnea

STUDY OBJECTIVES

To investigate the hypothesis that day/night patterns of prothrombotic activity differ between patients with obstructive sleep apnea (OSA) and individuals with no OSA.

DESIGN

Prothrombotic markers' day/night rhythms recorded over one 24-h period.

SETTING

General clinical research center.

PATIENTS

38 untreated OSA patients as verified by polysomnography (apnea-hypopnea index > or = 10/h sleep) and 22 non-OSA controls.

MEASUREMENTS AND RESULTS

Blood samples were collected every 2 h to measure plasma levels of fibrinolysis-inhibiting plasminogen activator inhibitor (PAI)-1 and the primary fibrin degradation product D-dimer. Day/night variation in hemostasis factors was examined using a cosinor analysis. Mesor (mean) PAI-1 over the 24-h period was higher (P = 0.015), and mesor of D-dimer was lower (P = 0.001) in patients with OSA than in the non-OSA controls. These group differences stayed significant when controlling for age and gender. After further adjustment for body mass index, mean arterial pressure, and smoking, the relationship between OSA and PAI-1 became non-significant, but the relationship between OSA and D-dimer continued to be significant (P = 0.006). In the fully adjusted analysis, the amplitude (peak) for D-dimer was lower in OSA patients than in non-OSA controls (P = 0.048). The acrophase (time of the peak) for PAI-1 and D-dimer did not significantly differ between groups.

CONCLUSIONS

The relatively higher average level of PAI-1 and lower average level of D-dimer across the 24-h in OSA patients might reflect decreased fibrinolytic capacity and fibrin degradation, respectively. The findings provide some evidence for a prothrombotic state in OSA, but were only partially independent of metabolic variables.

Sleep-disordered breathing in obese children: the southern Italy experience

BACKGROUND

The association of obesity with sleep-associated respiratory disturbances, which has traditionally been described as a problem in adults, actually originates in childhood. We sought an association between sleep-disordered breathing (SDB) and overweight and/or obesity in a large cohort of school- and preschool-aged children in Southern Italy.

METHODS

One thousand two hundred seven children (612 girls and 595 boys; mean age 7.3 years) were screened by self-administered questionnaires. According to answers, subjects were divided into three groups: nonsnorers (NS), occasional snorers (OS), and habitual snorers (HS). All HS, who also failed an oximetry study at home, underwent polysomnographic monitoring for the definition of SDB. BMI was calculated according to Italian growth charts.

RESULTS

A total of 809 subjects (67.0%) were eligible for the study. Of them, 44 subjects (5.4%) were classified as HS, 138 (17.0%) as OS, and 627 (77.5%) as NS. Fourteen subjects (1.7%) were given a diagnosis of obstructive sleep apnea syndrome (OSAS). Sixty-four subjects (7.9%) were defined as obese, 121 (14.9%) as overweight, and 624 (77.2%) as normal weight. The frequency of HS was significantly higher in obese subjects than in overweight and normal-weight subjects (12.5% vs 5.8% vs 4.6%, respectively; P = .02), whereas the frequency of OSAS was 1.6% in normal-weight, 1.6% in overweight, and 3.1% in obese subjects (P = not significant).

CONCLUSIONS

Our findings in a large sample of Italian children suggest that obesity is associated with snoring.

Obstructive sleep apnea (OSA) and excessive sleepiness associated with OSA: recognition in the primary care setting

Obstructive sleep apnea (OSA) is a common and debilitating condition characterized by recurrent episodes of upper airway obstruction, resulting in intermittent occurrence of apnea-hypopnea. Clinical features include snoring or disturbed sleep, reduced concentration and memory, mood disorders, and excessive sleepiness (ES). Left undiagnosed and untreated, OSA may have detrimental consequences, including cardiovascular (CV) morbidity and mortality, decreased health-related quality of life, and increased incidence of motor vehicle accidents. As most individuals affected by OSA will initially present in the primary care setting, primary care physicians have the opportunity to recognize the condition and refer patients for treatment when necessary. Management of the condition should include lifestyle changes and continuous positive airway pressure (CPAP) treatment if required. Wakefulness-promoting agents may be considered if ES persists despite CPAP. Effective intervention for OSA not only provides symptomatic benefits, but also improves hypertension and reduces the risk for fatal and nonfatal CV events associated with the condition.

Evaluation of a novel ambulatory device for screening of sleep apnea

The gold standard for diagnosis of obstructive sleep apnea (OSA) is the sleep laboratory polysomnography, which is technically demanding, labor-intensive, and time-consuming. Thus, screening of large undiagnosed population for OSA may be cost efficient only by means of ambulatory devices suitable for home recordings. The aim of our study was to evaluate the diagnostic and technical reliability of a novel ambulatory device (APV2, Remote Analysis Oy) introduced for sleep apnea diagnostics. APV2 records breathing movements, nasal and oral air flow, position, snore, blood oxygen saturation, and heart rate. The evaluation was done by comparing 10 simultaneous polygraphic recordings with APV2 and with commonly used clinical reference instrumentation (Embla, Embla Co.) at a sleep laboratory. Furthermore, the technical reliability of measurements was evaluated by analyzing the fraction of clinical APV2 and Embletta (Embla Co.) home recordings (n = 149 and n = 169, respectively) that were technically of diagnostically unacceptable quality. Similar diagnostic sensitivity in detecting OSA was found with the APV2 compared to the simultaneous reference recording with the Embla. Apnea-hypopnea indices and oxygen desaturation indices, recorded with APV2 and Embla, were closely correlated (r = 0.996-0.997, p < 0.0001). The quality of 90.0% of home recordings with APV2 was technically perfect and 96.0% of recordings were of diagnostically acceptable quality. As a comparison, the clinical evaluation of a widely used ambulatory polygraphy device (Embletta) showed that 77.2% of home recordings were technically perfect and 80.8% of recordings were diagnostically acceptable. In conclusion, the novel device was found clinically applicable, technically reliable, and sensitive for the diagnostics of OSA.

Melatonin reduces microvascular damage and insulin resistance in hamsters due to chronic intermittent hypoxia

Obstructive sleep apnea (OSA) causes intermittent hypoxia (IH) associated with hypertension, insulin resistance and a systemic inflammatory response. We evaluated the effects of melatonin on vasodilation, capillary perfusion in hamster cheek pouch and insulin resistance, hypertension, and reactive oxygen species (ROS) and nitrate/nitrite levels after IH for 4 wk. Syrian hamsters were divided into four groups: control group (CON), IH group, and melatonin (10 mg/kg) intraperitoneally administered daily for 4 wk/30 min before intermittent air (MEL) or IH (IH + MEL) exposure. IH alone caused elevated blood pressure, increased hematocrit, fasting hyperglycemia, elevated ROS and nitrite/nitrate levels, and vasoconstriction and reduced microvascular perfusion. Melatonin treatment of IH-exposed animals decreased blood pressure, blood glucose, and ROS and nitrite/nitrate levels, and increased vasodilation and capillary perfusion. An oral glucose tolerance test was performed after 4 wk of IH. During the last 30 min of the hyperinsulinemic euglycemic clamp, blood glucose, and insulin levels were identically matched between groups, but the glucose infusion rate was significantly reduced in IH (29.9 +/- 1.9 mg/kg/min) versus IH + MEL group (45.4 +/- 1.5 mg/kg/min, P < 0.05) demonstrating a decrease in insulin sensitivity. These results suggest that ROS and nitrite/nitrate levels play important roles in the microvascular dysfunction in IH and that this process is attenuated by melatonin. In conclusion, protection induced by melatonin against functional and metabolic impairment in IH is related to the regulation of ROS and nitrite/nitrate levels in the microcirculation. These observations may have importance to OSA pathological changes.

Essential role of SBP-1 activation in oxygen deprivation induced lipid accumulation and increase in body width/length ratio in Caenorhabditis elegans

Epidemiological evidence suggests a link between chronic oxygen starvation and fat accumulation/obesity, however the underlying mechanism remains unclear. Using Caenorhabditis elegans we found extended oxygen deprivation resulted in activation of SBP-1, the worm homologue of SREBP1, a transcription factor important in maintaining lipid homeostasis. SBP-1 knockdown prevented hypoxia-induced fat accumulation and the associated increase in worm width/length ratio, demonstrating that SBP-1/SREBP1 plays an essential role in hypoxia-induced lipid accumulation and body shape alteration. This study provides the first evidence suggesting that activation of SREBP1 may be a critical pathogenic factor contributing to chronic hypoxia associated excessive fat accumulation/obesity in humans.

Design, construction and evaluation of an ambulatory device for screening of sleep apnea

Obstructive sleep apnea syndrome (OSAS) is a major public health problem. The golden reference for diagnosing OSAS is the sleep-laboratory based polysomnography (PSG). However, screening of population for OSAS may be practical and cost efficient only through ambulatory home recordings. In this work we aimed to design, construct and evaluate a novel ambulatory device for these recordings. The device was designed to record breathing movements, nasal and oral flow, position, snore, blood oxygen saturation and heart rate. The first part of clinical evaluation was done by recording 19 patients simultaneously with the novel device and with clinical reference instrumentation at a sleep laboratory. In the simultaneous recordings, no statistically significant difference was detected in the apnea-hypopnea index. All patients were correctly diagnosed, as compared to the reference instrumentation, with the novel ambulatory device. The second part of clinical evaluation was conducted through 323 ambulatory home recordings of which 275 (193 males and 82 females) were of diagnostically acceptable quality. A total of 106 and 169 recordings were successfully conducted with the novel device and a commercial ambulatory device, respectively. Both devices showed similar diagnostic capability in detecting sleep apnea. The novel device was found clinically applicable, technically reliable and sensitive for the diagnostics of OSAS.

Adipocytokines and the metabolic complications of obesity

CONTEXT

Adipose tissue is increasingly recognized as an active endocrine organ with many secretory products and part of the innate immune system. With obesity, macrophages infiltrate adipose tissue, and numerous adipocytokines are released by both macrophages and adipocytes. Adipocytokines play important roles in the pathogenesis of insulin resistance and associated metabolic complications such as dyslipidemia, hypertension, and premature heart disease.

EVIDENCE ACQUISITION

Published literature was analyzed with the intent of addressing the role of the major adipose secretory proteins in human obesity, insulin resistance, and type 2 diabetes.

EVIDENCE SYNTHESIS

This review analyzes the characteristics of different adipocytokines, including leptin, adiponectin, pro-inflammatory cytokines, resistin, retinol binding protein 4, visfatin, and others, and their roles in the pathogenesis of insulin resistance.

CONCLUSIONS

Inflamed fat in obesity secretes an array of proteins implicated in the impairment of insulin signaling. Further studies are needed to understand the triggers that initiate inflammation in adipose tissue and the role of each adipokine in the pathogenesis of insulin resistance.

Pulmonary hypertension in interstitial lung disease

PURPOSE OF REVIEW

To examine recent advances in the understanding of the prevalence, pathophysiology, natural history, diagnosis, and treatment of pulmonary hypertension associated with interstitial lung disease.

RECENT FINDINGS

Significant progress has recently been made in understanding the etiology of various causes of pulmonary hypertension, including those associated with interstitial lung disease, and new data regarding the various pathophysiologic mechanisms of pulmonary hypertension in interstitial lung disease have been published. Therapeutic agents that were initially studied in patients with idiopathic pulmonary arterial hypertension are now being applied to interstitial lung disease-related pulmonary hypertension. Short-term hemodynamic benefits and disease-related quality of life outcomes that are associated with these advanced therapies are now better understood, but data regarding long-term outcomes and the efficacy of combination therapies remain lacking for interstitial lung disease-related pulmonary hypertension. Lung transplantation outcomes in the treatment of pulmonary hypertension associated with interstitial lung disease have been further defined.

SUMMARY

Pulmonary hypertension associated with interstitial lung disease is now frequently recognized and is associated with substantial morbidity and mortality. Various new pharmacotherapies as well as lung transplantation are increasing the treatment options for these disorders, although timing of advanced therapies and long-term benefits and toxicities remain uncertain.

Metabolic effects of the obstructive sleep apnea syndrome and cardiovascular risk

The obstructive sleep apnea syndrome (OSAS) is characterized by collapse of the upper airway during sleep, recurring apneas, intermittent hypoxemia and daytime somnolence. OSAS is often associated with obesity, and its prevalence is expected to rise due to the obesity epidemics worldwide. OSAS is associated with increased cardiovascular risk which appears to be normalized by treatment with nasal continuous positive airway pressure (nCPAP) during sleep, suggesting an independent role of OSAS in accelerating atherosclerosis. Insulin resistance (IR) and the metabolic syndrome (MetS) are often found in OSAS patients, but the relative role played by OSAS and obesity is still unclear. Both OSAS and MetS may exert negative synergistic effects on the cardiovascular system through multiple mechanisms (hypoxemia, sleep disruption, activation of the sympathetic nervous system, inflammatory activation). Besides nCPAP treatment, pharmacologic interventions to treat obesity and the MetS could improve cardiovascular prevention in OSAS.

Biology of peripheral blood cells in obstructive sleep apnea--the tip of the iceberg

Obstructive sleep apnea (OSA), a highly prevalent breathing disorder in sleep, characterized by intermittent and recurrent pauses in respiration, has emerged as an independent risk factor for cardiovascular morbidity and mortality. Accumulated evidence implicates Leukocyte-endothelial cell activation and adhesion as critical components that induce inflammation and injury to the vasculature resulting in the development of cardiovascular complications. Similar cellular interactions were described in conditions of ischemia/reperfusion, and various components of the metabolic syndrome as hypercholesterolemia and hypertension. The hallmark of sleep apnea--the multiple cycles of hypoxia/reoxygenation--promote oxidative stress and inflammation. These facilitate increased interactions of blood cells with endothelial cells, resulting in endothelial cell injury and dysfunction. Such events can promote atherosclerosis and the development of cardiovascular morbidities in OSA. However, inter-individual differences in response to intermittent hypoxia and activation of anti-inflammatory cytokine profiles in T lymphocytes can serve as protective mechanisms.

The underlying mechanisms for development of hypertension in the metabolic syndrome

High blood pressure is an important constituent of the metabolic syndrome. However, the underlying mechanisms for development of hypertension in the metabolic syndrome are very complicated and remain still obscure. Visceral/central obesity, insulin resistance, sympathetic overactivity, oxidative stress, endothelial dysfunction, activated renin-angiotensin system, increased inflammatory mediators, and obstructive sleep apnea have been suggested to be possible factors to develop hypertension in the metabolic syndrome. Here, we will discuss how these factors influence on development of hypertension in the metabolic syndrome.