Sleep apnea is a manifestation of the metabolic syndrome

Validation study of a portable monitoring device for identifying OSA in a symptomatic patient population

BACKGROUND AND OBJECTIVE

Obstructive sleep apnoea syndrome (OSAS) is a common disorder associated with early atherosclerosis, diabetes mellitus, ischaemic heart disease and cerebrovascular disease. The gold standard for confirming OSAS is based on an attended overnight polysomnography (PSG) in a sleep laboratory; however lack of health-care resources creates long waiting times for patient access to this diagnostic test. This study evaluated the ability of a portable sleep-monitoring device to identify patients in Hong Kong with suspected OSAS.

METHODS

Patients with symptoms of OSAS were invited to use the ARES (apnoea risk evaluation system) concurrently with an attended inpatient PSG. Several sets of AHI were generated by the ARES provider based on different oxygen desaturation criteria and surrogate parameters of arousal. The results were compared against PSG to determine the optimal sensitivity and specificity.

RESULTS

There were 141 patients who completed the study successfully. Results of AHI from the ARES study were presented in the order of different scoring criteria--4% oxygen desaturation alone, obstructive events with 3% oxygen desaturation and obstructive events with 1% desaturation plus surrogate arousal criteria. The sensitivity was 0.84 (95% confidence interval (CI): 0.77-0.90), 0.89 (95% CI: 0.89-0.94) and 0.97 (95% CI: 0.94-0.99), respectively. The specificity was 1, 1 and 0.63 (95% CI: 0.55-0.71), respectively. The receiver operating curve had an area of 0.96, 0.97 and 0.98, respectively. The kappa coefficient varied from 0.24 to 0.55 for agreement of severity between PSG and ARES. The likelihood ratio positive and the likelihood ratio negative were 2.61, infinity, infinity and 0.16, 0.11, 0.05, respectively, in the order of oxygen desaturation described earlier.

CONCLUSIONS

The ARES device has reasonable sensitivity and specificity for diagnosing severe OSAS in symptomatic Chinese patients. There is moderate agreement between ARES and PSG in the diagnosis of severe disease, but less agreement in patients with mild/moderate disease.

The metabolic syndrome

The "metabolic syndrome" (MetS) is a clustering of components that reflect overnutrition, sedentary lifestyles, and resultant excess adiposity. The MetS includes the clustering of abdominal obesity, insulin resistance, dyslipidemia, and elevated blood pressure and is associated with other comorbidities including the prothrombotic state, proinflammatory state, nonalcoholic fatty liver disease, and reproductive disorders. Because the MetS is a cluster of different conditions, and not a single disease, the development of multiple concurrent definitions has resulted. The prevalence of the MetS is increasing to epidemic proportions not only in the United States and the remainder of the urbanized world but also in developing nations. Most studies show that the MetS is associated with an approximate doubling of cardiovascular disease risk and a 5-fold increased risk for incident type 2 diabetes mellitus. Although it is unclear whether there is a unifying pathophysiological mechanism resulting in the MetS, abdominal adiposity and insulin resistance appear to be central to the MetS and its individual components. Lifestyle modification and weight loss should, therefore, be at the core of treating or preventing the MetS and its components. In addition, there is a general consensus that other cardiac risk factors should be aggressively managed in individuals with the MetS. Finally, in 2008 the MetS is an evolving concept that continues to be data driven and evidence based with revisions forthcoming.

Blood pressure associated with sleep-disordered breathing in a population sample of children

The current criteria for sleep-disordered breathing (SDB) in children are not based on a clinically relevant outcome. The purpose of this study was to assess the association of blood pressure with SDB in a random sample of the local elementary school children (kindergarten through grade 5) using a 2-phased strategy. During phase 1, a brief questionnaire was completed for all of the children (N=5740) with a response rate of 78.5%. During phase 2, 700 randomly selected children from phase 1 with a response rate of 70.0% were assessed with a full polysomnograph and a history/physical, including an ECG; ear, nose, and throat; and pulmonary evaluation. We observed a significantly elevated systolic blood pressure associated with the apnea hypopnea index (AHI): AHI >or=1 (2.9 mm Hg); AHI >or=3 (7.1 mm Hg); and AHI >or=5 (12.9 mm Hg). The SDB and blood pressure association remained significant after adjusting for age, sex, race, body mass index percentile or waist circumference, sleep efficiency, percentage of rapid eye movement sleep, and snoring. In addition, older age, body mass index percentile, waist circumference, and snoring were significantly associated with blood pressure, independent of SDB. Based on these findings, our study suggests that SDB is significantly associated with higher levels of systolic blood pressure in children aged 5 to 12 years even after adjusting for the various confounding factors. Clinically, the data support the threshold of AHI >or=5 for the initiation of treatment for SDB. Additional research is indicated to assess the efficacy of SDB treatment on reducing blood pressure.

Gender differences in obstructive sleep apnea and treatment implications

Obstructive sleep apnea (OSA) is a common cause of daytime sleepiness for millions of Americans. It is also a disease associated with an increased likelihood of hypertension, cardiovascular disease, stroke, daytime sleepiness, motor vehicle accidents, and diminished quality of life. A number of population-based studies have shown that OSA is more common in men than in women and this discrepancy is often evident in the clinical setting. There are a number of pathophysiological differences to suggest why men are more prone to the disease than women. Although the exact mechanisms are unknown, differences in obesity, upper airway anatomy, breathing control, hormones, and aging are all thought to play a role. The purpose of this review was to examine the literature on gender differences in OSA and to analyze whether or not these differences in pathogenic mechanisms affect diagnosis or treatment.

Obstructive sleep apnea syndrome is a systemic disease. Current evidence

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. Metabolic syndrome is another highly prevalence emerging public health problem that represents a constellation of cardiovascular risk factors. Each single component of the cluster increases the cardiovascular risk, but the combination of factors is much more significant. It has been suggested that the presence of OSAS may increase the risk of developing some metabolic syndrome features. Moreover, OSAS patients are at an increased risk for vascular events, which represent the greatest morbidity and mortality of all associated complications. Although the etiology of OSAS is uncertain, intense local and systemic inflammation is present. A variety of phenomena are implicated in this disease such as modifications in the autonomic nervous system, hypoxemia-reoxygenation cycles, inflammation, and coagulation-fibrinolysis imbalance. OSAS patients also present increased levels of certain biomarkers linked to endocrine-metabolic and cardiovascular alterations among other systemic consequences. All of this indicates that, more than a local abnormality, OSAS should be considered a systemic disease.

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.

Does obesity play a major role in the pathogenesis of sleep apnoea and its associated manifestations via inflammation, visceral adiposity, and insulin resistance?

Despite the early recognition of the strong association between obstructive sleep apnoea (OSA) and obesity, and OSA and cardiovascular problems, sleep apnoea has been treated as a "local abnormality" of the respiratory track rather than as a "systemic illness". In 1997, we first reported that the pro-inflammatory cytokines interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNFalpha) were elevated in patients with disorders of excessive daytime sleepiness (EDS) and proposed that these cytokines were mediators of daytime sleepiness. In subsequent studies, it was shown that IL-6, TNFalpha, and insulin levels were elevated in sleep apnoea independently of obesity and that visceral fat was the primary parameter linked with sleep apnoea. Further studies showed that women with the polycystic ovary syndrome (PCOS) were much more likely than controls to have sleep-disordered breathing (SDB) and daytime sleepiness, suggesting a pathogenetic role of insulin resistance in OSA. Additional accumulated evidence that supports the role of obesity and the associated metabolic aberrations in the pathogenesis of sleep apnoea and related symptoms include: obesity without sleep apnoea is associated with daytime sleepiness; the protective role of gonadal hormones as suggested by the increased prevalence of sleep apnoea in post-menopausal women and the significantly reduced risk for OSA in women on hormonal therapy; partial effects of continuous positive airway pressure (CPAP) in obese patients with apnoea on hypercytokinemia, insulin resistance indices, and visceral fat; and that the prevalence of the metabolic syndrome in the U.S. population from the Third National Health and Nutrition Examination Survey (1988-1994) parallels the prevalence of symptomatic sleep apnoea in general random samples. Furthermore, the beneficial effect of a cytokine antagonist on EDS and apnoea in obese, male apnoeics and that of exercise and weight loss on SDB and EDS in general random or clinical samples, supports the hypothesis that cytokines and insulin resistance are mediators of EDS and sleep apnoea in humans. Finally, our recent finding that in obese, hypothalamic CRH neuron is hypoactive, provides additional evidence on the potential central neural mechanisms for depressed ventilation and consequent development of sleep apnoea in obese individuals. In conclusion, accumulating evidence provides support to our thesis that obesity via inflammation, insulin resistance, visceral adiposity, and central neural mechanisms, e.g. hypofunctioning hypothalamic CRH, play a major role in the pathogenesis of sleep apnoea, sleepiness, and the associated cardiovascular co-morbidities.

Obesity and the lung: 3. Obesity, respiration and intensive care

Obesity is a major problem from a public health perspective and a difficult practical matter for intensivists. The obesity pandemic has required treating clinicians to develop an appreciation of the substantial pathophysiological effects of obesity on the various organ systems. The important physiological concepts are illustrated by focusing on obstructive sleep apnoea, obesity hypoventilation syndrome, abdominal compartment syndrome and ventilatory management of the obese patient with acute respiratory distress syndrome.

The metabolic syndrome, diabetes and lung dysfunction

Sleep-disordered breathing and sleep apnoea are conditions frequently associated with comorbidity, including obesity, diabetes, hypertension, insulin resistance (metabolic syndrome) and cardiovascular disease. The diabetic state (type 1 and type 2 diabetes) may be associated to diminished lung function and, in particular, decreased vital capacity, and the association between chronic obstructive pulmonary disease (COPD) and type 2 diabetes may be due to a shared inflammatory process. Also, the alteration in circulating endothelial progenitor cells found in respiratory disease, the metabolic syndrome and cardiovascular disease reflect a common condition of endothelial dysfunction.

Respiratory sleep disturbances in patients undergoing gastric bypass surgery and their relation to metabolic syndrome

BACKGROUND

The prevalence of obstructive sleep apnea syndrome (OSAS) is high in obese patients. Certain components of metabolic syndrome are linked to OSAS, but there is no information on their association in morbidly obese patients. Our aim was to ascertain the prevalence of respiratory disturbances during sleep in candidates for bariatric surgery and to study their association with metabolic syndrome.

METHODS

We examined the preoperative records (history, physical examination and laboratory findings, spirometry, and overnight pulse oximetry [arterial oxygen saturation by pulse oximetry, [SpO(2)]]) of patients scheduled for gastric bypass surgery for 1 year in our hospital; an overnight sleep study was performed if SpO(2) readings or symptoms suggested sleep disturbance. Metabolic syndrome was defined according to the criteria of the National Cholesterol Education Program's Adult Treatment Panel III.

RESULTS

Of the 31 patients studied, 19 (61.3%) had OSAS, including 15 newly diagnosed cases with a mean +/- standard deviation apnea-hypopnea index of 49 +/- 36. OSAS patients had higher fasting plasma glucose and triglyceride levels and a higher prevalence of diabetes. Metabolic syndrome was also more frequent in subjects with previously untreated OSAS (13/14, 92%) than in those without sleep disturbance (six of 11, 55%; p = 0.033). Conversely, the prevalence of OSAS in patients with metabolic syndrome was higher (13/19, 68%) than in subjects without metabolic syndrome (one of six, 17%; p = 0.026) even though the two groups had similar body mass index.

CONCLUSIONS

Sleep disordered breathing is very prevalent in obese patients who are candidates for bariatric surgery and its presence is related to metabolic syndrome.

Effects of acute intermittent hypercapnic hypoxia on insulin sensitivity in piglets using euglycemic clamp

Continuous hypoxia is associated with insulin resistance, altered glucose metabolism, and increased sympathetic nervous activity. This study examined the effect of 2 successive exposures to intermittent hypercapnic hypoxia (IHH) on glucose metabolism and insulin sensitivity in neonatal piglets. Piglets were assigned to 2 groups. One group was exposed to 2 x 90 minutes of hypercapnic hypoxia (8% O(2), 7% CO(2)), intermittently in 6-minute cycles alternating with 6-minute air. The second group was given 2 x 90 minutes of air. Blood pressure, blood gases, glucose, insulin, and lactate were measured during exposures. Insulin sensitivity was assessed using the euglycemic clamp before and after the exposures. Piglets in the IHH group exhibited reduced PO(2) (from 111.4 +/- 14.2 to 43.3 +/- 21.7), increased PCO(2) (from 33.6 +/- 1.9 to 49.4 +/- 5.4), and lactic acidosis. Compared with air, IHH decreased blood glucose (control [CON] 4.44 +/- 0.72 mmol/L vs IHH 2.67 +/- 1.2 mmol/L, P = .007), insulin (CON 12.5 +/- 7.4 microU/mL vs IHH 3.6 +/- 3.1 microU/mL, P = .03), and mean arterial pressure (CON 143.0 +/- 7.9 mm Hg vs IHH 112.5 +/- 9.5 mm Hg, P < .001) over 90 minutes. Maximal insulin-stimulated glucose disposal was not different between the groups on either day, nor was endogenous glucose production. Overall, exposure to hypoxia in an intermittent pattern reduced sympathetic drive as indicated by blood pressure and did not alter insulin sensitivity, resulting in decreases in blood glucose and insulin. We speculate that an intermittent hypoxic stimulus results in failure of initiation of compensatory responses to increased energy requirements that would usually be observed during sustained exposure to hypoxia.

Self-reported symptoms of sleep disturbance and inflammation, coagulation, insulin resistance and psychosocial distress: evidence for gender disparity

Self-reported ratings of sleep quality and symptoms of poor sleep have been linked to increased risk of coronary heart disease (CHD), Type 2 diabetes and hypertension with recent evidence suggesting stronger associations in women. At this time, the mechanisms of action that underlie these gender-specific associations are incompletely defined. The current study examined whether gender moderates the relation of subjective sleep and sleep-related symptoms to indices of inflammation, coagulation, insulin resistance (IR) and psychosocial distress, factors associated with increased risk of cardiovascular and metabolic disorders. Subjects were 210 healthy men and women without a history of sleep disorders. The Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality and frequency of sleep symptoms. In multivariate-adjusted models, overall poor sleep quality, more frequent problems falling asleep (>2 night/week) and longer periods to fall asleep (>30 min) were associated with greater psychosocial distress, higher fasting insulin, fibrinogen and inflammatory biomarkers, but only for women. The data suggest that subjective ratings of poor sleep, greater frequency of sleep-related symptoms, and longer period of time to fall asleep are associated with a mosaic of biobehavioral mechanisms in women and that these gender-specific associations have direct implications to recent observations suggesting gender differences in the association between symptoms of poor sleep and cardiovascular disease.

Selective effects of CPAP on sleep apnoea-associated manifestations

BACKGROUND

Visceral adiposity and obstructive sleep apnoea (OSA) may be independently associated with daytime sleepiness/low performance, insulin resistance, hypercytokinaemia, and/or hypertension. The objectives of this study are to simultaneously test these associations at baseline and after 3 months of continuous positive airway pressure (CPAP) therapy.

MATERIALS AND METHODS

Sixteen obese men with OSA; 13 non-apnoeic, obese controls, and 15 non-obese controls were monitored in the sleep laboratory for four consecutive nights. Objective measures of daytime sleepiness and performance, serial 24 h plasma measures of interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-alpha), TNF receptor 1 (TNF-r1) and adiponectin, fasting blood glucose and insulin, visceral adiposity and blood pressure were obtained. Sleep apnoeics were re-assessed using the same protocol after 3 months of CPAP.

RESULTS

At baseline, IL-6, TNF-r1, and insulin resistance were highest in OSA patients, intermediate in obese controls, and lowest in non-obese controls (P < 0.05). Visceral fat was significantly greater in sleep apnoeics than obese controls and predicted insulin resistance and IL-6 levels, whereas OSA predicted TNF-r1 levels (P < 0.05). CPAP decreased daytime sleepiness and blood pressure (P < 0.05), but did not affect fasting glucose or insulin or around the clock adiponectin, IL-6, TNF-alpha, or TNF-r1 levels.

CONCLUSIONS

In obese sleep apnoeics, visceral fat is strongly associated with insulin resistance and inflammation. CPAP decreases sleepiness and moderates hypertension but does not affect visceral adiposity, insulin resistance, hypoadiponectinaemia or hypercytokinaemia, all of which are independent risk factors for cardiovascular disease and diabetes.

Effects of continuous positive airway pressure on cardiovascular risk profile in patients with severe obstructive sleep apnea and metabolic syndrome

BACKGROUND

The increased risk of atherosclerotic morbidity and mortality in patients with obstructive sleep apnea (OSA) has been linked to arterial hypertension, insulin resistance, systemic inflammation, and oxidative stress. We aimed to determine the effects of 8 weeks of therapy with continuous positive airway pressure (CPAP) on glucose and lipid profile, systemic inflammation, oxidative stress, and global cardiovascular disease (CVD) risk in patients with severe OSA and metabolic syndrome.

METHODS

In 32 patients, serum cholesterol, triglycerides, high-density lipoprotein cholesterol, fibrinogen, apolipoprotein A-I, apolipoprotein B (ApoB), high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor (TNF)-alpha, leptin, malondialdehyde (MDA), and erythrocytic glutathione peroxidase (GPx) activity were measured at baseline and after 8 weeks of CPAP. The insulin resistance index (homeostasis model assessment [HOMA-IR]) was based on the homeostasis model assessment method, the CVD risk was calculated using the multivariable risk factor algorithm.

RESULTS

In patients who used CPAP for > or = 4 h/night (n = 16), CPAP therapy reduced systolic BP and diastolic BP (p = 0.001 and p = 0.006, respectively), total cholesterol (p = 0.002), ApoB (p = 0.009), HOMA-IR (p = 0.031), MDA (p = 0.004), and TNF-alpha (p = 0.037), and increased erythrocytic GPx activity (p = 0.015), in association with reductions in the global CVD risk (from 18.8 +/- 9.8 to 13.9 +/- 9.7%, p = 0.001). No significant changes were seen in patients who used CPAP for < 4 h/night. Mask leak was the strongest predictor of compliance with CPAP therapy.

CONCLUSIONS

In patients with severe OSA and metabolic syndrome, good compliance to CPAP may improve insulin sensitivity, reduce systemic inflammation and oxidative stress, and reduce the global CVD risk.

Obesity and obstructive sleep apnea-hypopnea syndrome

Obstructive sleep apnea-hypopnea syndrome involves recurring episodes of total obstruction (apnea) or partial obstruction (hypopnea) of airways during sleep. Obstructive sleep apnea-hypopnea syndrome affects mainly obese individuals and it is defined by an apnea-hypopnea index of five or more episodes per hour associated with daytime somnolence. In addition to anatomical factors and neuromuscular and genetic factors, sleep disorders are also involved in the pathogenesis of sleep apnea. Obesity affects upper airway anatomy because of fat deposition and metabolic activity of adipose tissue. Obstructive sleep apnea-hypopnea syndrome and metabolic syndrome have several characteristics such as visceral obesity, hypertension and insulin resistance. Inflammatory cytokines might be related to the pathogenesis of sleep apnea and metabolic syndrome. Sleep apnea treatment includes obesity treatment, use of equipment such as continuous positive airway pressure, drug therapy and surgical procedures in selected patients. Currently, there is no specific drug therapy available with proven efficacy for the treatment of obstructive sleep apnea-hypopnea syndrome. Body-weight reduction results in improvement of sleep apnea, and obesity treatment must be emphasized, including lifestyle changes, anti-obesity drugs and bariatric surgery.

Risperidone use in children with Down syndrome, severe intellectual disability, and comorbid autistic spectrum disorders: a naturalistic study

OBJECTIVE

We report on an open-label, naturalistic study using risperidone to treat disruptive behaviors and self-injury in children with Down syndrome, severe intellectual disability, and comorbid autism spectrum disorders (DS+ASDs). We hypothesized that hyperactivity and disruptive behaviors would improve in response to risperidone treatment consistent with previous studies of children with ASD.

METHODS

Subjects were children (mean age, 7.8 +/- 2.6 years), consisting of 20 males and three females identified through our outpatient Down Syndrome Clinic between 2000 and 2004.

RESULTS

Using the Aberrant Behavior Checklist as the primary outcome measure, all five subscales showed significant improvement following risperidone treatment. The mean duration of treatment was 95.8 +/- 16.8 days, and mean total daily dose was 0.66 +/- 0.28 mg/day. The Hyperactivity, Stereotypy, and Lethargy subscale scores showed the most significant reduction (p < .001), followed by Irritability (p < .02), and Inappropriate Speech (p < .04). Children with disruptive behavior and self-injury showed the greatest improvement. Sleep quality improved for 88% of subjects with preexisting sleep disturbance. Subjects for whom a follow-up weight was available showed a mean weight increase of 2.8 +/- 1.5 kg during the treatment period.

CONCLUSIONS

These findings support our clinical impression of improvement on important target behaviors such as aggression, disruptiveness, self-injury, stereotypy, and social withdrawal. Low-dose risperidone appears to be well tolerated in children with DS+ASD, although concerns about weight gain and metabolic alterations may limit its usefulness over the long term in some children.

Structural equation modeling of sleep apnea, inflammation, and metabolic dysfunction in children

Obstructive sleep apnea (OSA), often concomitant with obesity, increases the risk for the metabolic syndrome. One mechanism that may participate in this association is upregulation of inflammatory pathways. We used structural equation modeling to assess the interrelations between childhood obesity, OSA, inflammation, and metabolic dysfunction. One hundred and eighty-four children (127 boys, mean age: 8.5 +/- 4.1 years) had height and weight measured, underwent overnight polysomnography and had fasting blood taken. The blood was analyzed for insulin, glucose, lipids, leptin, and cytokines [interferon (IFN)-gamma, granulocyte macrophage-colony stimulating factor, interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, tumor necrosis factor-alpha]. Structural equation modeling (SEM) was used to evaluate associations between the outcomes of interest including hypoxia, arousal (related to respiratory and spontaneous), obesity, metabolic dysfunction, and inflammatory markers. Two cytokine factors and one metabolic factor were derived for the SEM. These factors provided good fit in the structural equation model (chi(2)/df = 2.855; comparative fit index = 0.90, root mean squared error of approximation = 0.10) and all factor loadings were significantly different from zero (P < or = 0.01). Overall, our results indicate that while obesity (as measured by body mass index z-score) has a major influence on the metabolic dysfunction associated with OSA, arousal indices, and cytokine markers may also influence this association. Our results support the hypothesis that OSA is a contributor to the mechanisms that link sleep, systemic inflammation and insulin resistance, and show that the interrelations may begin in childhood.

Green tea catechin polyphenols attenuate behavioral and oxidative responses to intermittent hypoxia

RATIONALE

The intermittent hypoxia (IH) that characterizes sleep-disordered breathing impairs spatial learning and increases NADPH oxidase activity and oxidative stress in rodents. We hypothesized that green tea catechin polyphenols (GTPs) may attenuate IH-induced neurobehavioral deficits by reducing IH-induced NADPH oxidase expression, lipid peroxidation, and inflammation.

OBJECTIVES

To assess the effects of GTP administered in drinking water on the cognitive, inflammatory, and oxidative responses to long-term (>14 d) IH during sleep in male Sprague-Dawley rats.

METHODS

Cognitive assessments were conducted in the Morris water maze. We measured levels and expression of malondialdehyde (MDA), prostaglandin E(2), p47(phox) subunit of NADPH oxidase, receptor for advanced glycation end products (RAGE), and glial fibrillary acidic protein expression in rodent brain tissue.

MEASUREMENTS AND MAIN RESULTS

GTP treatment prevented IH-induced decreases in spatial bias for the hidden platform during the Morris water maze probe trails as well as IH-induced increases in p47phox expression within the hippocampal CA1 region. In untreated animals, IH exposure was associated with doubling of cortical MDA levels in comparison to room air control animals, and GTP-treated animals exposed to IH showed a 40% reduction in MDA levels. Increases in brain RAGE and glial fibrillary acidic protein expression were observed in IH-exposed animals, and these increases were attenuated in animals treated with GTP.

CONCLUSIONS

Oral GTP attenuates IH-induced spatial learning deficits and mitigates IH-induced oxidative stress through multiple beneficial effects on oxidant pathways. Because oxidative processes underlie neurocognitive deficits associated with IH, the potential therapeutic role of GTP in sleep-disordered breathing deserves further exploration.

An update on obstructive sleep apnea and the metabolic syndrome

PURPOSE OF REVIEW

Patients with obstructive sleep apnea are often overweight or obese, and they frequently exhibit metabolic aberrations, collectively known as the metabolic syndrome, an established cardiovascular risk factor. We review recent data on the relationship between obstructive sleep apnea and metabolic syndrome or its components, including abdominal obesity, insulin resistance, hypertension, and dyslipidemia.

RECENT FINDINGS

There is accumulating evidence for an independent association between obstructive sleep apnea and metabolic syndrome or its components. Recent epidemiologic and clinical data suggest a causal role of severe obstructive sleep apnea in development of hypertension, but findings for insulin resistance and dyslipidemia are controversial. Visceral obesity remains a confounding issue in analyses. Animal models and translational studies indicate that obstructive sleep apnea may promote metabolic dysfunction through cycles of intermittent hypoxia; proposed underlying pathophysiologic mechanisms include oxidative stress, sympathetic activation, and inflammation.

SUMMARY

There is suggestive evidence, but independent associations between obstructive sleep apnea and metabolic syndrome or its components are not fully established because of the confounding effect of obesity. Large randomized interventional trials are needed to identify any cause-effect relationship. Long-term follow-up studies would help to clarify the role of treatment of sleep apnea in reducing cardio-metabolic morbidity.

Distinct behavioral and neurochemical alterations induced by intermittent hypoxia or paradoxical sleep deprivation in rats

The current study investigated the effects of paradoxical sleep deprivation and intermittent hypoxia by examining whether a combination of the two would induce anxiety-like alterations in behavior. The neurochemical effects of these manipulations were investigated by measuring cortical, striatal and hippocampal monoamine concentrations. Wistar Hannover rats were submitted to subchronic (3 days) intermittent hypoxia exposure (alternating cycles of 2 min room air-2 min 10% O2 from 0700-1900 h) and paradoxical sleep deprivation using the single platform method. Rats were randomly assigned to four different protocols: 1) control, 2) intermittent hypoxia during the light period (12 h/day), 3) paradoxical sleep deprivation (24 h/day), and 4) intermittent hypoxia combined with paradoxical sleep deprivation. Rats subjected to intermittent hypoxia showed no modification in the behavioral or neurochemical parameters assessed. Although paradoxical sleep deprivation did not produce alterations in anxiety-like behavior, the rats did increase exploratory activity in the elevated plus-maze. Moreover, a significant increase in striatal epinephrine and hippocampal homovanilic acid (HVA) concentrations was found in the paradoxical sleep deprivation groups, but not in the intermittent hypoxia/paradoxical sleep deprivation group. Of note, both paradoxical sleep deprivation and intermittent hypoxia/paradoxical sleep deprivation groups showed an increase in plasma corticosterone concentration. These results suggest that paradoxical sleep deprivation induces behavioral alterations, and these abnormalities may reflect altered neurotransmission in the brain. When paradoxical sleep deprivation was combined with intermittent oxygen depletion, the behavioral and biochemical parameters were comparable to those of control rats.

Relationship between metabolic syndrome and sleep-disordered breathing in patients with cardiovascular disease--metabolic syndrome as a strong factor of nocturnal desaturation

OBJECTIVE

Metabolic syndrome (MetS) is one of the coronary risk factors for cardiovascular disease and is closely related with sleep-disordered breathing (SDB). Our aim in this study was to estimate the relationship between sleep-related breathing events and coronary risk factors, including MetS.

METHODS

We determined the prevalence of MetS in 195 patients with cardiovascular disease. Based on Japanese MetS criteria, 56 patients had MetS (Group A), whereas 139 patients did not (Group B). We assessed SDB and sleep-related breathing events, including nocturnal desaturation, in both groups using a type 3 apparatus (Morpheus); Teijin Pharma Limited, Tokyo, Japan).

RESULTS

Seventy-seven percent of the patients with MetS (43/56) met the criteria for SDB based on apnea hypopnea index (AHI). The AHI value was significantly greater in Group A than in Group B (30.1 +/- 19.0/hr vs. 17.7 +/- 14.7/hr; p < 0.001). Nocturnal oximetry showed that Group A spent a greater percentage of time at pulse-oximetric oxygen saturation below 90% (CT 90) than did Group B (10.6 +/- 13.2% vs. 5.0 +/- 12.5%; p < 0.01). On multivariate logistic regression analysis for CT 90, MetS showed that the odds ratio was 2.629 (95% confidence interval: 1.259-5.592; p = 0.011).

CONCLUSION

These results suggest that SDB is common in cardiovascular patients with MetS. Patients with MetS frequently experience a sleep-related breathing event. Compared with the incidence of apnea hypopnea, MetS is an equivalently strong factor of nocturnal desaturation in patients with cardiovascular disease.

The reciprocal interaction between sleep and type 2 diabetes mellitus: facts and perspectives

Type 2 diabetes mellitus is a systemic disease characterized by intolerance to glucose and peripheral resistance to insulin. This endocrine disease affects fundamental mechanisms of the central nervous system and jeopardizes the balance of vital functions such as the cardiovascular and circadian rhythm. The increased prevalence of metabolic disorders in our society is aggravated by endemic voluntary postponement of bedtime and by the current sedentary lifestyle, leading to epidemic proportions of obese people. Diabetes and chronic loss of sleep share the fact that both affect millions and one is detrimental to the other. Indeed, sleep deficits have marked modulatory effects on glucose metabolism and insulin sensitivity and foster metabolic syndrome that culminates in sleep disorders like restless syndrome and sleep apnea, which in turn lead to poor sleep quality. We examine the hypothesis that these two worldwide emerging disorders are due to two interlinked cycles. In our paradigm, we establish an intimate relationship between diabetes and sleep disturbances and postulate possible mechanisms that provide support for this conjecture. In addition, we propose some perspectives about the development of the reciprocal interaction between predictor components of metabolic syndrome and sleep disturbances that lead to poor sleep quality. The ability to predict the development and identify or associate a given mode of sleep disturbance to diabetes would be a valuable asset in the assessment of both. Furthermore, major advances in care coupled with healthy lifestyles can ensure a higher quality of life for people with diabetes.

Cytokines and pathological sleep

Cytokines are proteins produced by leukocytes and other cells that function as intercellular mediators acting on several target tissues, resulting in multiple biologic actions. Over the last decade, medical research has explored the interaction between cytokines and sleep disorders. The aim of this review is to illustrate recent advances in knowledge about the relationship between cytokines and disorders of excessive sleepiness. Cytokines may have an important role in mediating excessive daytime sleepiness in sleep loss or insomnia. Alterations of the immune system have also been associated with narcolepsy. The relationship between cytokines and hormonal regulatory mechanisms may explain symptoms like fatigue and sleepiness in chronic inflammatory diseases. Cytokines may play an important role in the pathogenesis of obstructive sleep apnea and cardiovascular consequences of this condition. New biologic treatments targeting cytokines have been investigated in conditions characterized by sleep disturbance.

Hypothalamic-pituitary-adrenal axis activity in obese men with and without sleep apnea: effects of continuous positive airway pressure therapy

CONTEXT

Previous studies on the association between the hypothalamic-pituitary-adrenal axis activity and sleep apnea (SA) and obesity are inconsistent and/or limited.

OBJECTIVE

In this study, we evaluated the activity of the hypothalamic-pituitary-adrenal axis in nonpsychologically distressed obese subjects with and without SA and examined the impact of continuous positive airway pressure (CPAP) in SA patients.

DESIGN AND PARTICIPANTS

In study I, four-night sleep laboratory recordings and serial 24-h plasma measures of cortisol were obtained in 45 obese men with and without apnea and nonobese controls. Sleep apneic patients were reassessed after 3 months of CPAP use. In study II, 38 obese men with and without sleep apnea and nonobese controls were challenged with ovine CRH administration after four nights in the sleep laboratory.

RESULTS

The sleep patterns were similar between obese and nonobese controls. Twenty-four-hour plasma cortisol levels were highest in nonobese controls, intermediate in obese apneic patients, and lowest in obese controls (8.8 +/- 0.4 vs. 8.1 +/- 0.3 vs. 7.5 +/- 0.3 microg/dl, P < 0.05). CPAP tended to reduce cortisol levels in the apneic patients (difference -0.7 +/- .4 microg/dl, P = 0.1). CRH administration resulted in a higher ACTH response in both obese groups, compared with nonobese controls; the three groups were not different in cortisol response.

CONCLUSIONS

Nonpsychologically distressed, normally sleeping, obese men had low cortisol secretion. The cortisol secretion was slightly activated by SA and returned to low by CPAP use. The low cortisol secretion in obesity through its inferred hyposecretion of hypothalamic CRH might predispose the obese to sleep apnea.

Metabolic syndrome: treatment of hypertensive patients

Metabolic syndrome (MetSyndr), a constellation of abnormalities [obesity, glucose intolerance, insulin resistance (IR), dyslipidemia (low HDL-cholesterol, high LDL-cholesterol and triglycerides (TG)], and elevated blood pressure (BP)], increases the risk of cardiovascular (CV) disease and premature death. From 10% to 30% of the adult population in industrialized countries has MetSyndr, which effectively predicts the development of type 2 diabetes mellitus (T2D) and CV disease. Because of the complex etiology of MetSyndr, a multi-targeted, integrated therapeutic approach is required to simultaneously treat high BP, obesity, lipid disorders and T2D (if present), to fully protect CV, cerebrovascular and renal systems. If lifestyle modification (weight control, diet, exercise, smoking cessation, moderation of alcohol intake) is ineffective, pharmaco-theraphy should be added to treat simultaneously the lipid- and non-lipid CV risk factors. Patients with HTN and MetSyndr should be started on angiotensin-converting enzyme (ACE) inhibitors, unless contraindicated. The ACE inhibitors and angiotensin receptor blockers (ARBs) reduce the odds of developing new onset T2D and also decrease albuminuria. The ACE inhibitors provide cardioprotective and renoprotective benefits beyond their effect on BP; they also improve IR. The ARBs are renoprotective in addition to being cardioprotective. Long-acting calcium channel blockers are also recommended in hypertensive patients with MetSyndr; these drugs also improve IR. Thiazides (at low doses) and selected ss-blockers can be given to patients with HTN and MetSyndr. Celiprolol in combination with diuretics has a favorable effect on glucose tolerance and IR in patients with HTN and MetSyndr, and spironolactone added to ACE inhibitor or ARB therapy provides additional reno- and CV protective benefits in patients with diabetic nephropathy. Carvedilol, a ss-blocker with vasodilating properties, added to ACE inhibitor or ARB therapy, is effective in preventing worsening of microalbuminuria in patients with HTN and MetSyndr; it also improves IR and glycemic control. Most patients eventually require two or more antihypertensive drugs to reach BP goal. It is recommended that therapy in patients whose BP is more than 20/10 mm Hg above target at diagnosis be initiated with a combination of antihypertensive drugs, administered either as individual drugs or as fixed-dose formulations. Treatment with fixed-dose combinations, such as irbesartan + hydrochlorothiazide provides good BP control in more than two-thirds of hypertensive patients with MetSyndr. Lipid and BP targets are reached in a high percent of patients with HTN and CV disease treated with a combination of amlodipine + atorvastatin. In conclusion, hypertensive patients with the MetSyndr be treated aggressively for each component of the syndrome to provide CV, cerebrovascular and renal protection.

Obesity in neurobiology

Obesity reflects an imbalance between energy uptake and expenditure that is mediated by behavior. Obesity is a growing epidemic and a major risk factor for neurobiological diseases like stroke, dementia, intracranial hypertension and sleep disorders. Conversely, obesity can also be induced by neurobiological disorders and drugs. The etiology of obesity is complex and includes biology, behavior and environment. Physicians are faced with the need to manage obesity while strategies for prevention and sustained weight reduction are limited. Present treatment options comprise lifestyle modification, diet, pharmacotherapy and bariatric surgery. Considerable headway has been made into elucidating the neurobiological underpinnings of obesogenic behavior. There is now a growing understanding of the metabolic, hormonal and behavioral circuitries that contribute to the complex and redundant system for energy balance. Changing the net balance of this system to prevent or reduce obesity requires multimodal and long-term interventions.

Very low birth weight increases risk for sleep-disordered breathing in young adulthood: the Helsinki Study of Very Low Birth Weight Adults

OBJECTIVE

We investigated whether very low birth weight (<1500 g) is associated with the risk of sleep-disordered breathing in young adulthood.

METHODS

The study was a retrospective longitudinal study of 158 young adults born with very low birth weight and 169 term-born control subjects (aged 18.5-27.1 years). The principal outcome variable was sleep-disordered breathing defined as chronic snoring.

RESULTS

The crude prevalence of chronic snoring was similar in both groups: 15.8% for the very low birth weight group versus 13.6% for the control group. However, after controlling for the confounding variables in multivariate logistic regression models (age, gender, current smoking, parental education, height, BMI, and depression), chronic snoring was 2.2 times more likely in the very low birth weight group compared with the control group. In addition, maternal smoking during pregnancy was significantly and independently of very low birth weight related to risk of sleep-disordered breathing. Maternal preeclampsia, standardized birth weight, and, for very low birth weight infants, small-for-gestational-age status were not related to sleep-disordered breathing.

CONCLUSIONS

Premature infants with very low birth weight have a twofold risk of sleep-disordered breathing as young adults. In addition, maternal smoking during pregnancy increases the risk of sleep-disordered breathing by more than twofold.

Treatment of obstructive sleep apnea using an adjustable mandibular repositioning appliance fitted to a total prosthesis in a maxillary edentulous patient

This paper reports on the case of an oral appliance used in the treatment of obstructive sleep apnea syndrome (OSAS) fitted to a superior total prosthesis. In this case, the chosen device was the adjustable PMPositioner, a mandibular repositioning appliance. A polysomnogram (PSG) both prior and with the oral appliance "in situ" was applied to evaluate the effect of the adaptation of the adjustable PMPositioner fixed onto a maxillary full denture in decreasing the apnea-hypopnea index from 18.0 to 2.2 as well as increasing the minimum oxygen saturation (SaO2 nadir) from 83 to 92%, proving that the device remained in position during sleep.

Alveolar-derived exhaled nitric oxide is reduced in obstructive sleep apnea syndrome

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is associated with cardiovascular diseases, in particular systemic arterial hypertension. We postulated that intermittent nocturnal hypoxia in OSAS may be associated to decreased fractional exhaled nitric oxide (FENO) levels from distal airspaces.

METHODS

Multiple flow rate measurements have been used to fractionate nitric oxide (NO) from alveolar and bronchial sources in 34 patients with OSAS, in 29 healthy control subjects, and in 8 hypertensive non-OSAS patients. The effect of 2 days of treatment with nasal continuous positive airway pressure (nCPAP) on FENO was examined in 18 patients with severe OSAS.

RESULTS

We found that the mean [+/- SE] concentrations of exhaled NO at a rate of 50 mL/s was 21.8 +/- 1.9 parts per billion (ppb) in patients with OSAS, 25.1 +/- 3.3 ppb in healthy control subjects, and 15.4 +/- 1.7 ppb in hypertensive control patients. The mean fractional alveolar NO concentration (CANO) in OSAS patients was significantly lower than that in control subjects (2.96 +/- 0.48 vs 5.35 +/- 0.83 ppb, respectively; p < 0.05). In addition, CANO values were significantly lower in OSAS patients with systemic hypertension compared to those in normotensive OSAS patients and hypertensive patients without OSAS. The mean values of CANO significantly improved after nCPAP therapy (2.67 +/- 0.41 to 4.69 +/- 0.74 nL/L, respectively; p = 0.01).

CONCLUSIONS

These findings suggest that alveolar FENO, and not bronchial FENO, is impaired in patients with OSAS and that this impairment is associated with an increased risk of hypertension. NO production within the alveolar space is modified by treatment with nCPAP.

Sleep and the body mass index and overweight status of children and adolescents

Associations between sleep and the body mass index (BMI) and overweight status of children and adolescents were estimated using longitudinal data from a nationally representative sample of 2,281 children aged 3-12 years at baseline. Controlling for baseline BMI, children who slept less, went to bed later, or got up earlier at the time of the first assessment had higher BMIs 5 years later and were more likely to be overweight. Child age moderated the relationship between bedtime and BMI. In addition, the study reports nationally representative data on the sleep habits of American children aged 3-18 years. This study underscores the likely importance of sleep on children's physical health and suggests that sleep is important for understanding childhood weight problems.

Sleep apnea: clinical investigations in humans

Sleep apnea syndrome (SAS), a common disorder, is characterized by repetitive episodes of cessation of breathing during sleep, resulting in hypoxemia and sleep disruption. The consequences of the abnormal breathing during sleep include daytime sleepiness, neurocognitive dysfunction, development of cardiovascular disorders, metabolic dysfunction, and impaired quality of life. There are two types of SAS: obstructive sleep apnea syndrome (OSAS) and central sleep apnea syndrome (CSAS). OSAS is a prevalent disorder in which there is snoring, repetitive apneic episodes, and daytime sleepiness. Anatomical conditions causing upper airway obstruction (obesity or craniofacial abnormalities such as retrognathia or micrognathia) can cause OSAS. CSAS, much less common than OSAS, is a disorder characterized by cessation of breathing which is caused by reduced respiratory drive from the central nervous system to the muscles of respiration. The latter condition is common in patients with heart failure and cerebral neurologic diseases. The diagnosis of SAS requires assessment of subjective symptoms and apneic episodes during sleep documented by polysomnography. Treatments of OSAS include continuous positive airway pressure (CPAP), oral appliances, and surgery; patients with CSAS are treated with oxygen, adaptive servo-ventilation, or CPAP. With assessment and treatment of the SAS, patients usually have resolution of their disabling symptoms, subsequently resulting in improved quality of life.

Diagnostic and therapeutic approach to nonsleepy apnea

Epidemiological and observational studies suggest that sleep-disordered breathing is associated with the subsequent development of hypertension and ultimately with cardiovascular consequences. It may therefore be assumed that continuous positive airway pressure (CPAP) not only avoids sleep-related symptoms but could also mitigate cardiovascular consequences. Short-term studies have revealed a drop in blood pressure, especially in more severe, symptomatic cases of obstructive sleep apnea. Two recent studies have reported that nonsleepy obstructive sleep apnea is associated with an absence of reduced blood pressure after CPAP treatment. This suggests that this group of patients is less susceptible to the consequences of apneas, even those with mild-moderate hypertension or other cardiovascular disorders. However, in patients with severe cardiovascular disease or a higher number of obstructive events, CPAP treatment should be seriously considered.

Sleep medicine content of major medical textbooks continues to be underrepresented

OBJECTIVE

Sleep-related material in medical textbooks may be the only method by which physicians educate themselves about sleep. In the last decade significant progress in sleep research has been made, but how textbooks in relevant fields reflect it has not been examined. Our purpose was to review and compare (2005 with 1998) sleep content in representative medical textbooks.

METHODS

Sleep content of the latest edition of textbooks in four specialties was evaluated. Present sleep content in seven textbooks was compared with that found in 1998. Numbers of pages devoted to sleep were counted and reported for the subjects covered and for the specialty of the textbook.

RESULTS

Thirty-one textbooks were examined for current content and seven textbooks for content comparison. Sleep coverage in medical textbooks uniformly received less than 2% of the text volume. Focus of topics covered varied with specialty. Compared with 1998, the proportion of pages devoted to sleep remained the same or decreased. Coverage of new topics remained minimal.

CONCLUSIONS

Major medical textbooks present small amounts of sleep content and few provide a comprehensive overview of sleep medicine. In comparison to textbook editions from the 1990s, current editions still devote little attention to sleep, and the diversity of topics has not improved.

Is excessive daytime sleepiness a predictor of carotid atherosclerosis in sleep apnea?

OBJECTIVE

To elucidate the relationship between excessive daytime sleepiness (EDS) in obstructive sleep apnea (OSA) and carotid atherosclerosis determined by ultrasonography and serum surrogate markers.

METHODS

One hundred and forty-seven patients (102 males) with snoring and sleep-disordered breathing were investigated. Carotid atherosclerosis was evaluated by serum analysis of high-sensitivity C-reactive protein and fibrinogen and four sonographic indices: intima media thickness (IMT) of the common carotid artery (CCA), IMT from the bulb to the internal carotid artery (ICA), combined IMT measurements from all segments and a plaque score. EDS was assessed by the Epworth Sleepiness Scale (ESS). Pearson correlation analysis, intergroup comparison (ANOVA) and two multiple regression models explored associations between confounders, surrogate markers and EDS.

RESULTS

Forty-four patients had no OSA (apnea-hypopnea index AHI<5h(-1)), 27 mild (5-15), 25 moderate (15-30) and 51 severe OSA (>30). The ESS significantly distinguished severe OSA from non-OSA patients (p=0.003). It showed significant correlations with the BMI, HbA1c, systolic RR, the AHI, sleep time spent with an oxygen saturation <90%, the respiratory arousal index, IMT of the CCA and combined IMT measurements, but no correlation with serum markers. The ESS was found to be an independent predictor of CCA-IMT in the pre-polysomnographic multiple regression model (p=0.008), but not in the post-polysomnographic model after including respiratory variables.

CONCLUSION

EDS is associated with obesity, diabetes and all respiratory variables in OSA patients and may serve as an independent predictor of carotid atherosclerosis before polysomnography.

Obstructive sleep apnea: an update on mechanisms and cardiovascular consequences

BACKGROUND AND AIM

There is growing recognition of the widespread incidence and health consequences of obstructive sleep apnea (OSA). This review examines the evidence linking sleep apnea with cardiovascular disease and discusses potential mechanisms underlying this link.

DATA SYNTHESIS

The weight of evidence provides increasing support for a causal relationship between OSA and hypertension. Furthermore, OSA may contribute to the initiation and progression of cardiac ischemia, heart failure and stroke. Chronic sympathetic activation appears to be a key mechanism linking OSA to cardiovascular disease. Other potential mechanisms include inflammation, endothelial dysfunction, increased levels of endothelin, hypercoagulability and stimulation of the renin angiotensin system. OSA, hypertension and obesity often coexist and interact, sharing multiple pathophysiological mechanisms and cardiovascular consequences. Effective treatment of OSA may attenuate neural and humoral abnormalities in circulatory control, improve blood pressure control and conceivably reduce the risk of future cardiovascular events.

CONCLUSION

Patients with OSA are at increased risk for cardiovascular disease. OSA should be considered in the differential diagnosis of hypertensive patients who are obese. In particular, OSA should be excluded in patients with hypertension resistant to conventional drug therapy.

Autonomic dysfunction in obstructive sleep apnea is associated with impaired glucose regulation

INTRODUCTION

Autonomic dysfunction has been theorized to be responsible for the increased risk of cardiovascular disease in obstructive sleep apnea (OSA). Previous studies did not control for the presence of impaired glucose regulation (IGR, comprising impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and diabetes) which is also associated with abnormalities in autonomic function.

METHODS

Thirty-two patients were recruited for the study. Patients underwent autonomic testing consisting of heart rate response to deep breathing, valsalva maneuver, tilt-up, and quantitative sudomotor axon reflex testing. Polysomnography (PSG) and a 2-h oral glucose tolerance test were performed. Results were analyzed with logistic regression, with age, race, body mass index (BMI), and gender as covariates.

RESULTS

Nineteen of 24 patients with OSA had abnormal glucose (79%, p=0.04) compared to two of nine patients without OSA. The correlation between IGR, OSA and total autonomic dysfunction was similar (p=.10 for IGR, p=0.06 for OSA). However, cardiac autonomic function was more strongly associated with IGR than OSA (p=.10 vs. 0.50). Age was a significant confounder, as glucose correlated with adrenergic autonomic dysfunction significantly when age was removed from the model (p=0.006).

CONCLUSIONS

The presence of IGR may be a confounding factor in studies of autonomic function in OSA. Larger studies are needed to delineate whether OSA is directly associated with autonomic dysfunction or whether the previously described association between dysautonomia and OSA may have been due to glucose dysregulation.

[Obstructif sleep apnea-hypopnea syndrome: evolution of an old concept]

This review summarizes the well-known clinical features of the obstructive sleep apnea-hypopnea syndrome (OSAHS) and emphasizes new research on this syndrome. Though described in the seventies, the prevalence OSAHS is known mainly in the US. A dramatic increasing in prevalence has been related to the increase prevalence of obesity, raising a substantial public health problem. Discussion continues on the proper definition of the syndrome and degrees of severity. Multiple factors are involved in the pathogenesis of sleep apnea: anatomic abnormalities, mechanical factors, nervous alterations, muscular imbalance between pharyngeal constrictor and dilator muscles or part of a metabolic syndrome? Indeed, obstructive sleep apnea with and without obesity is increasingly implicated in the initiation and progression of metabolic disorders and of cardiovascular diseases (hypertension, cardiac ischemia and probably congestive heart failure, cardiac arrhythmias and strokes). An extended literature reports the neural, humoral, thrombotic, metabolic and inflammatory mechanisms linking OSAHS to endocrinology and cardiovascular diseases. Daytime sleepiness, cognitive, memory and performance deficits with their risks are also stressed. These consequences require treating this syndrome as soon as possible. Multiple interventions (medical, mechanical-nasal positive airway pressure or oral appliances, and sometimes surgical management) can be used but nasal continuous positive airway pressure is the "gold standard" treatment in severe OSAHS. More often multiple interventions are appropriate in a given patient. Finally, there is growing evidence that genetic factors influence the expression of OSAHS. Numerous genetic studies have investigated the etiology of OSAHS with the goal of improving our understanding of its pathogenesis.