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1.  Reactive Oxygen Species Production in Peripheral Blood Neutrophils of Obstructive Sleep Apnea Patients 
The Scientific World Journal  2013;2013:421763.
Obstructive sleep apnea (OSA) as well as obesity is associated with increased production of reactive oxygen species (ROS). Neutrophils produce great amounts of ROS. The aim was to evaluate peripheral blood neutrophils ROS production in men with OSA and to establish relations with disease severity and obesity. Methods. Forty-six men with OSA and 10 controls were investigated. OSA was confirmed by polysomnography (PSG), when apnea/hypopnea index was >5/h. Body mass index (BMI) was evaluated. Neutrophils were isolated from peripheral blood in the morning after PSG. Dihydrorhodamine-123 was used for ROS detection. Data is presented as median (25th and 75th percentiles). All subjects were divided into four groups: nonobese mild-to-moderate OSA, obese mild-to-moderate OSA, nonobese severe OSA, and obese severe OSA. Results. Neutrophil ROS production was higher in nonobese severe OSA group compared to nonobese mild-to-moderate OSA (mean fluorescence intensity (MFI) 213.4 (89.0–238.9) versus 44.5 (20.5–58.4), P < 0.05). In obese patient groups, ROS production was more increased in severe OSA compared to mild-to-moderate OSA group (MFI 74.5 (47.9–182.4) versus 31.0 (14.8–53.8), P < 0.05). It did not differ in the groups with different BMI and the same severity of OSA. Conclusion. Increased neutrophil ROS production was related to more severe OSA but not obesity.
doi:10.1155/2013/421763
PMCID: PMC3666210  PMID: 23766689
2.  Polysomnography in Patients With Obstructive Sleep Apnea 
Executive Summary
Objective
The objective of this health technology policy assessment was to evaluate the clinical utility and cost-effectiveness of sleep studies in Ontario.
Clinical Need: Target Population and Condition
Sleep disorders are common and obstructive sleep apnea (OSA) is the predominant type. Obstructive sleep apnea is the repetitive complete obstruction (apnea) or partial obstruction (hypopnea) of the collapsible part of the upper airway during sleep. The syndrome is associated with excessive daytime sleepiness or chronic fatigue. Several studies have shown that OSA is associated with hypertension, stroke, and other cardiovascular disorders; many researchers believe that these cardiovascular disorders are consequences of OSA. This has generated increasing interest in recent years in sleep studies.
The Technology Being Reviewed
There is no ‘gold standard’ for the diagnosis of OSA, which makes it difficult to calibrate any test for diagnosis. Traditionally, polysomnography (PSG) in an attended setting (sleep laboratory) has been used as a reference standard for the diagnosis of OSA. Polysomnography measures several sleep variables, one of which is the apnea-hypopnea index (AHI) or respiratory disturbance index (RDI). The AHI is defined as the sum of apneas and hypopneas per hour of sleep; apnea is defined as the absence of airflow for ≥ 10 seconds; and hypopnea is defined as reduction in respiratory effort with ≥ 4% oxygen desaturation. The RDI is defined as the sum of apneas, hypopneas, and abnormal respiratory events per hour of sleep. Often the two terms are used interchangeably. The AHI has been widely used to diagnose OSA, although with different cut-off levels, the basis for which are often unclear or arbitrarily determined. Generally, an AHI of more than five events per hour of sleep is considered abnormal and the patient is considered to have a sleep disorder. An abnormal AHI accompanied by excessive daytime sleepiness is the hallmark for OSA diagnosis. For patients diagnosed with OSA, continuous positive airway pressure (CPAP) therapy is the treatment of choice. Polysomnography may also used for titrating CPAP to individual needs.
In January 2005, the College of Physicians and Surgeons of Ontario published the second edition of Independent Health Facilities: Clinical Practice Parameters and Facility Standards: Sleep Medicine, commonly known as “The Sleep Book.” The Sleep Book states that OSA is the most common primary respiratory sleep disorder and a full overnight sleep study is considered the current standard test for individuals in whom OSA is suspected (based on clinical signs and symptoms), particularly if CPAP or surgical therapy is being considered.
Polysomnography in a sleep laboratory is time-consuming and expensive. With the evolution of technology, portable devices have emerged that measure more or less the same sleep variables in sleep laboratories as in the home. Newer CPAP devices also have auto-titration features and can record sleep variables including AHI. These devices, if equally accurate, may reduce the dependency on sleep laboratories for the diagnosis of OSA and the titration of CPAP, and thus may be more cost-effective.
Difficulties arise, however, when trying to assess and compare the diagnostic efficacy of in-home PSG versus in-lab. The AHI measured from portable devices in-home is the sum of apneas and hypopneas per hour of time in bed, rather than of sleep, and the absolute diagnostic efficacy of in-lab PSG is unknown. To compare in-home PSG with in-lab PSG, several researchers have used correlation coefficients or sensitivity and specificity, while others have used Bland-Altman plots or receiver operating characteristics (ROC) curves. All these approaches, however, have potential pitfalls. Correlation coefficients do not measure agreement; sensitivity and specificity are not helpful when the true disease status is unknown; and Bland-Altman plots measure agreement (but are helpful when the range of clinical equivalence is known). Lastly, receiver operating characteristics curves are generated using logistic regression with the true disease status as the dependent variable and test values as the independent variable. Thus, each value of the test is used as a cut-point to measure sensitivity and specificity, which are then plotted on an x-y plane. The cut-point that maximizes both sensitivity and specificity is chosen as the cut-off level to discriminate between disease and no-disease states. In the absence of a gold standard to determine the true disease status, ROC curves are of minimal value.
At the request of the Ontario Health Technology Advisory Committee (OHTAC), MAS has thus reviewed the literature on PSG published over the last two years to examine new developments.
Methods
Review Strategy
There is a large body of literature on sleep studies and several reviews have been conducted. Two large cohort studies, the Sleep Heart Health Study and the Wisconsin Sleep Cohort Study, are the main sources of evidence on sleep literature.
To examine new developments on PSG published in the past two years, MEDLINE, EMBASE, MEDLINE In-Process & Other Non-Indexed Citations, the Cochrane Database of Systematic Reviews and Cochrane CENTRAL, INAHTA, and websites of other health technology assessment agencies were searched. Any study that reported results of in-home or in-lab PSG was included. All articles that reported findings from the Sleep Heart Health Study and the Wisconsin Sleep Cohort Study were also reviewed.
Diffusion of Sleep Laboratories
To estimate the diffusion of sleep laboratories, a list of sleep laboratories licensed under the Independent Health Facility Act was obtained. The annual number of sleep studies per 100,000 individuals in Ontario from 2000 to 2004 was also estimated using administrative databases.
Summary of Findings
Literature Review
A total of 315 articles were identified that were published in the past two years; 227 were excluded after reviewing titles and abstracts. A total of 59 articles were identified that reported findings of the Sleep Heart Health Study and the Wisconsin Sleep Cohort Study.
Prevalence
Based on cross-sectional data from the Wisconsin Sleep Cohort Study of 602 men and women aged 30 to 60 years, it is estimated that the prevalence of sleep-disordered breathing is 9% in women and 24% in men, on the basis of more than five AHI events per hour of sleep. Among the women with sleep disorder breathing, 22.6% had daytime sleepiness and among the men, 15.5% had daytime sleepiness. Based on this, the prevalence of OSA in the middle-aged adult population is estimated to be 2% in women and 4% in men.
Snoring is present in 94% of OSA patients, but not all snorers have OSA. Women report daytime sleepiness less often compared with their male counterparts (of similar age, body mass index [BMI], and AHI). Prevalence of OSA tends to be higher in older age groups compared with younger age groups.
Diagnostic Value of Polysomnography
It is believed that PSG in the sleep laboratory is more accurate than in-home PSG. In the absence of a gold standard, however, claims of accuracy cannot be substantiated. In general, there is poor correlation between PSG variables and clinical variables. A variety of cut-off points of AHI (> 5, > 10, and > 15) are arbitrarily used to diagnose and categorize severity of OSA, though the clinical importance of these cut-off points has not been determined.
Recently, a study of the use of a therapeutic trial of CPAP to diagnose OSA was reported. The authors studied habitual snorers with daytime sleepiness in the absence of other medical or psychiatric disorders. Using PSG as the reference standard, the authors calculated the sensitivity of this test to be 80% and its specificity to be 97%. Further, they concluded that PSG could be avoided in 46% of this population.
Obstructive Sleep Apnea and Obesity
Obstructive sleep apnea is strongly associated with obesity. Obese individuals (BMI >30 kg/m2) are at higher risk for OSA compared with non-obese individuals and up to 75% of OSA patients are obese. It is hypothesized that obese individuals have large deposits of fat in the neck that cause the upper airway to collapse in the supine position during sleep. The observations reported from several studies support the hypothesis that AHIs (or RDIs) are significantly reduced with weight loss in obese individuals.
Obstructive Sleep Apnea and Cardiovascular Diseases
Associations have been shown between OSA and comorbidities such as diabetes mellitus and hypertension, which are known risk factors for myocardial infarction and stroke. Patients with more severe forms of OSA (based on AHI) report poorer quality of life and increased health care utilization compared with patients with milder forms of OSA. From animal models, it is hypothesized that sleep fragmentation results in glucose intolerance and hypertension. There is, however, no evidence from prospective studies in humans to establish a causal link between OSA and hypertension or diabetes mellitus. It is also not clear that the associations between OSA and other diseases are independent of obesity; in most of these studies, patients with higher values of AHI had higher values of BMI compared with patients with lower AHI values.
A recent meta-analysis of bariatric surgery has shown that weight loss in obese individuals (mean BMI = 46.8 kg/m2; range = 32.30–68.80) significantly improved their health profile. Diabetes was resolved in 76.8% of patients, hypertension was resolved in 61.7% of patients, hyperlipidemia improved in 70% of patients, and OSA resolved in 85.7% of patients. This suggests that obesity leads to OSA, diabetes, and hypertension, rather than OSA independently causing diabetes and hypertension.
Health Technology Assessments, Guidelines, and Recommendations
In April 2005, the Centers for Medicare and Medicaid Services (CMS) in the United States published its decision and review regarding in-home and in-lab sleep studies for the diagnosis and treatment of OSA with CPAP. In order to cover CPAP, CMS requires that a diagnosis of OSA be established using PSG in a sleep laboratory. After reviewing the literature, CMS concluded that the evidence was not adequate to determine that unattended portable sleep study was reasonable and necessary in the diagnosis of OSA.
In May 2005, the Canadian Coordinating Office of Health Technology Assessment (CCOHTA) published a review of guidelines for referral of patients to sleep laboratories. The review included 37 guidelines and associated reviews that covered 18 applications of sleep laboratory studies. The CCOHTA reported that the level of evidence for many applications was of limited quality, that some cited studies were not relevant to the recommendations made, that many recommendations reflect consensus positions only, and that there was a need for more good quality studies of many sleep laboratory applications.
Diffusion
As of the time of writing, there are 97 licensed sleep laboratories in Ontario. In 2000, the number of sleep studies performed in Ontario was 376/100,000 people. There was a steady rise in sleep studies in the following years such that in 2004, 769 sleep studies per 100,000 people were performed, for a total of 96,134 sleep studies. Based on prevalence estimates of the Wisconsin Sleep Cohort Study, it was estimated that 927,105 people aged 30 to 60 years have sleep-disordered breathing. Thus, there may be a 10-fold rise in the rate of sleep tests in the next few years.
Economic Analysis
In 2004, approximately 96,000 sleep studies were conducted in Ontario at a total cost of ~$47 million (Cdn). Since obesity is associated with sleep disordered breathing, MAS compared the costs of sleep studies to the cost of bariatric surgery. The cost of bariatric surgery is $17,350 per patient. In 2004, Ontario spent $4.7 million per year for 270 patients to undergo bariatric surgery in the province, and $8.2 million for 225 patients to seek out-of-country treatment. Using a Markov model, it was concluded that shifting costs from sleep studies to bariatric surgery would benefit more patients with OSA and may also prevent health consequences related to diabetes, hypertension, and hyperlipidemia. It is estimated that the annual cost of treating comorbid conditions in morbidly obese patients often exceeds $10,000 per patient. Thus, the downstream cost savings could be substantial.
Considerations for Policy Development
Weight loss is associated with a decrease in OSA severity. Treating and preventing obesity would also substantially reduce the economic burden associated with diabetes, hypertension, hyperlipidemia, and OSA. Promotion of healthy weights may be achieved by a multisectorial approach as recommended by the Chief Medical Officer of Health for Ontario. Bariatric surgery has the potential to help morbidly obese individuals (BMI > 35 kg/m2 with an accompanying comorbid condition, or BMI > 40 kg/m2) lose weight. In January 2005, MAS completed an assessment of bariatric surgery, based on which OHTAC recommended an improvement in access to these surgeries for morbidly obese patients in Ontario.
Habitual snorers with excessive daytime sleepiness have a high pretest probability of having OSA. These patients could be offered a therapeutic trial of CPAP to diagnose OSA, rather than a PSG. A majority of these patients are also obese and may benefit from weight loss. Individualized weight loss programs should, therefore, be offered and patients who are morbidly obese should be offered bariatric surgery.
That said, and in view of the still evolving understanding of the causes, consequences and optimal treatment of OSA, further research is warranted to identify which patients should be screened for OSA.
PMCID: PMC3379160  PMID: 23074483
3.  Metabolic Alterations and Systemic Inflammation in Obstructive Sleep Apnea among Nonobese and Obese Prepubertal Children 
Rationale: Obstructive sleep apnea (OSA) has been associated with a higher prevalence and severity of the metabolic syndrome in adult patients, even after controlling for obesity. In contrast, OSA in prepubertal children does not appear to correlate with the magnitude of such metabolic derangements.
Objectives: To further establish the potential mechanistic role of OSA in metabolic regulation in prepubertal children.
Methods: Fasting glucose, insulin, C-reactive protein, apolipoprotein B, and serum lipid concentrations were determined during the initial polysomnographic diagnosis of OSA and 6–12 months after adenotonsillectomy in both obese and nonobese children.
Measurements and Main Results: Sixty-two children with OSA (37 obese and 25 nonobese), age 7.40 ± 2.6 years (mean ± SD) completed the study. After adenotonsillectomy, significant improvements in apnea–hypopnea index and sleep fragmentation occurred, particularly among nonobese children. In nonobese children, adenotonsillectomy was associated with mild increases in body mass index z scores, no changes in either fasting glucose or insulin, significant increases in high-density lipoprotein and reciprocal decreases in low-density lipoprotein, and reductions in plasma C-reactive protein and apolipoprotein B levels. In obese children, adenotonsillectomy did not result in body mass index or glucose changes, but was associated with marked improvements in all other measures.
Conclusions: OSA does not appear to induce insulin resistance in nonobese pediatric patients but seems to play a significant role in obese patients. The significant improvements in lipid profiles, C-reactive protein, and apolipoprotein B after adenotonsillectomy in the two groups suggest a pathogenic role for OSA in lipid homeostasis and systemic inflammation independent of the degree of adiposity.
doi:10.1164/rccm.200711-1670OC
PMCID: PMC2383995  PMID: 18276939
obstructive sleep apnea; inflammation; obesity; serum lipids; diabetes
4.  The Role of Obesity, Different Fat Compartments and Sleep Apnea Severity in Circulating Leptin Levels: The Icelandic Sleep Apnea Cohort Study 
Objectives
To assess whether sleep apnea severity has an independent relationship with leptin levels in blood after adjusting for different measures of obesity and whether the relationship between OSA severity and leptin levels differs depending on obesity level.
Methods
Cross-sectional study of 452 untreated obstructive sleep apnea (OSA) patients (377 males and 75 females), in the Icelandic Sleep Apnea Cohort (ISAC), age 54.3±10.6 (mean±SD), BMI 32.7±5.3 kg/m2 and apnea-hypopnea index (AHI) 40.2 ± 16.1 events/hour. A sleep study and magnetic resonance imaging of abdominal visceral and subcutaneous fat volume were performed as well as fasting serum morning leptin levels measured.
Results
Leptin levels were more highly correlated with body mass index (BMI), total abdominal and subcutaneous fat volume than visceral fat volume per se. No relationship was found between sleep apnea severity and leptin levels, assessed within three BMI groups (BMI<30, BMI 30–35 and BMI>35 kg/m2). In a multiple linear regression model, adjusted for gender, BMI explained 38.7% of the variance in leptin levels, gender explained 21.2% but OSA severity did not have a significant role and no interaction was found between OSA severity and BMI on leptin levels. However, hypertension had a significant effect on the interaction between OSA severity and obesity (p=0.04). In post-hoc analysis for nonhypertensive OSA subjects (n=249), the association between leptin levels and OSA severity explained a minor but significant variance (3.2%) in leptin levels. This relationship was greatest for nonobese nonhypertensive subjects (significant interaction with obesity level). No relationship of OSA severity and leptin levels was found for hypertensive subjects (n=199).
Conclusion
Obesity and gender are the dominant determinants of leptin levels. OSA severity is not related to leptin levels except to a minor degree in nonhypertensive nonobese OSA subjects.
doi:10.1038/ijo.2012.138
PMCID: PMC3537909  PMID: 22964793
Obstructive sleep apnea; leptin; visceral fat; subcutaneous fat; obesity; hypertension
5.  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.
doi:10.2174/1874306401307010071
PMCID: PMC3822706  PMID: 24222804
Obstructive sleep apnea; metabolic syndrome; HDL cholesterol; insulin resistance.
6.  Risk of obstructive sleep apnea in obese and non-obese women with polycystic ovary syndrome and healthy reproductively normal women 
Fertility and Sterility  2012;97(3):786-791.
Objective
To study the risk for obstructive sleep apnea (OSA) in a group of non-obese and obese PCOS and control women. Women with polycystic ovary syndrome (PCOS) are at high risk for obstructive sleep apnea (OSA). Whether this risk is independent of obesity is not clear.
Design/Patients/Interventions/Main Outcome Measures
In a prospective study, 44 women with PCOS and 34 control women completed the Berlin questionnaire for assessment of OSA risk. All women underwent fasting determination of androgens, glucose and insulin.
Results
Women with PCOS were more obese compared to control women (p=0.02). However, there were no differences in BMI once subjects were divided into non-obese (PCOS n=17 and control n=26) and obese (PCOS n=26 and control n=8) groups. Women with PCOS had higher prevalence of high risk OSA compared to control women on the Berlin questionnaire (47% vs. 15%, P<0.01). However, none of the non-obese PCOS and control women screened positive for high risk OSA. Among the obese group, the risk did not differ between groups (77% vs. 63%, P= 0.65).
Conclusions
Our findings indicate that even though the risk for OSA in PCOS is high, it is related to the high prevalence of severe obesity. The risk for OSA among non-obese women with PCOS is very low. However, our findings are limited by lack of polysomnographic confirmation of OSA.
doi:10.1016/j.fertnstert.2011.12.024
PMCID: PMC3292664  PMID: 22264851
Berlin questionnaire; Obesity; Insulin resistance; Body mass index
7.  The correlation of anxiety and depression with obstructive sleep apnea syndrome 
Background:
Obstructive sleep apnea syndrome (OSAS) is a common sleep disorder characterized by repeated upper airway obstruction during sleep. While respiratory pauses followed by loud snoring and daytime sleepiness are the main symptoms of OSAS, the patients may complain from sleep disruption, headache, mood disturbance, irritability, and memory impairment. However, the association of sleep apnea with anxiety and depression is not completely understood. Adherence to continuous positive airway pressure (CPAP), the treatment of choice for OSAS, may be influenced by psychological conditions, especially claustrophobia. The aim of this study was to evaluate the association of OSAS with anxiety and depression symptoms. This study also investigated the association of anxiety with body mass index (BMI) and the severity of OSAS.
Materials and Methods:
We conducted a cross-sectional study on 178 adult individuals diagnosed with OSAS at the sleep laboratory between September 2008 and May 2012. The participants were interviewed according to a checklist regarding both their chief complaints and other associated symptoms. The psychological status was assessed according to Beck anxiety inventory (BAI) and Beck depression inventory (BDI) scoring. The severity of breathing disorder was classified as mild, moderate, and severe based on apnea–hypopnea index (AHI) which was ascertained by overnight polysomnography. Daytime sleepiness was assessed by Epworth sleepiness scale (ESS).
Results:
The mean (SD) age of participants was 50.33 years. In terms of sex, 85.5% of the study population were males and14.4% were females. We found no relation between sex and the symptoms of OSAS. Regarding the frequency of anxiety and depression symptoms, 53.9% of the individuals had some degree of anxiety, while 46.1% demonstrated depressive symptoms. In terms of OSAS severity, this study showed that OSAS severity was associated with the frequency of anxiety, chocking, and sleepiness (P : 0.001). According to polysomnographic results, we found that the majority of patients suffering from anxiety and chocking (66.7% and 71.4%, respectively) had severe OSAS, while only 23.1% of patients with sleepiness had severe OSAS.
Conclusion:
Our study showed that the frequency of anxiety in OSAS patients is higher than in the general population regardless of the gender. Furthermore, it is more likely that OSAS patients present with anxiety and depression than the typical symptoms.
PMCID: PMC4061640  PMID: 24949026
Anxiety; depression; obstructive sleep apnea syndrome
8.  A Relationship between the Obstructive Sleep Apnea Syndrome and the Erythrocyte Sedimentation Rate 
Objectives
The erythrocyte sedimentation rate (ESR) is a marker for inflammation, and it has been identified as a risk factor for atherothrombotic cardiovascular disease. The aim of this study was to determine the relationship between the plasma ESR level and nocturnal oxygen desaturation or other polysomnographic variables and to examine the role of obesity in patients with obstructive sleep apnea syndrome (OSAS).
Methods
This retrospective study included 72 patients with a diagnosis of OSAS who underwent overnight polysomnography and routine blood tests between July and December of 2005. We compared the plasma ESR level with the sum of all the polysomnographic variables and divided the patient group into obese and non-obese patients.
Results
The mean ESR level was 8.45 mm/hr. There was a significant difference in the ESR level between genders (P<0.001). A significant correlation was found between the percentage of time spent at a SpO2 below 90% and the ESR level in the obese group (BMI ≥25, N=43, P=0.012). In addition, the ESR levels had a positive correlation with age in the obese group (P=0.002). However, there was no significant correlation with the percentage of time spent at a SpO2 below 90% in the whole group of patients and in the non-obese group (BMI <25, N=29). The ESR level showed no correlation with the other polysomnographic variables.
Conclusion
The duration of deoxygenation in obese patients with OSAS may be associated with the ESR level which is an independent predictor of cardiovascular disease.
doi:10.3342/ceo.2009.2.3.126
PMCID: PMC2751876  PMID: 19784404
Blood sedimentation; Obstructive sleep apnea; Oximetry; Polysomnography
9.  Type 2 diabetes and pre-diabetes are associated with obstructive sleep apnea in extremely obese subjects: A cross-sectional study 
Background
Obstructive sleep apnea (OSA) is a common yet underdiagnosed condition. The aim of our study is to test whether prediabetes and type 2 diabetes are associated with obstructive sleep apnea (OSA) in extremely obese (BMI ≥ 40 kg/m2) subjects.
Methods
One hundred and thirty seven consecutive extremely obese patients (99 females) from a controlled clinical trial [MOBIL-study (Morbid Obesity treatment, Bariatric surgery versus Intensive Lifestyle intervention Study) (ClinicalTrials.gov number NCT00273104)] underwent somnography with Embletta® and a 2-hour oral glucose tolerance test (OGTT). OSA was defined by an apnea-hypopnea index (AHI) ≥ 5 events/hour. Patients were categorized into three groups according to criteria from the American Diabetes Association: normal glucose tolerance, pre-diabetes and type 2 diabetes. Multiple logistic regression analysis was used to identify possible determinants of OSA.
Results
The patients had a mean (SD) age of 43 (11) years and a body mass index (BMI) of 46.9 (5.7) kg/m2. Males had significantly higher AHI than females, 29 (25) vs 12 (17) events/hour, p < 0.001. OSA was observed in 81% of men and in 55% of women, p = 0.008. Twenty-nine percent of subjects had normal glucose tolerance, 42% had pre-diabetes and 29% had type 2 diabetes. Among the patients with normal glucose tolerance 33% had OSA, while 67% of the pre-diabetic patients and 78% of the type 2 diabetic patients had OSA, p < 0.001. After adjusting for age, gender, BMI, high sensitive CRP and HOMA-IR, both pre-diabetes and type 2 diabetes were still associated with OSA, odds ratios 3.18 (95% CI 1.00, 10.07), p = 0.049 and 4.17 (1.09, 15.88), p = 0.036, respectively. Mean serum leptin was significantly lower in the OSA than in the non-OSA group, while other measures of inflammation did not differ significantly between groups.
Conclusions
Type 2 diabetes and pre-diabetes are associated with OSA in extremely obese subjects.
Trial registration
MOBIL-study (Morbid Obesity treatment, Bariatric surgery versus Intensive Lifestyle intervention Study) (ClinicalTrials.gov number NCT00273104)
doi:10.1186/1475-2840-10-84
PMCID: PMC3206416  PMID: 21943153
Obstructive sleep apnea; type 2 diabetes; prediabetes; oral glucose tolerance test; inflammation
10.  Childhood Obstructive Sleep Apnea Associates with Neuropsychological Deficits and Neuronal Brain Injury 
PLoS Medicine  2006;3(8):e301.
Background
Childhood obstructive sleep apnea (OSA) is associated with neuropsychological deficits of memory, learning, and executive function. There is no evidence of neuronal brain injury in children with OSA. We hypothesized that childhood OSA is associated with neuropsychological performance dysfunction, and with neuronal metabolite alterations in the brain, indicative of neuronal injury in areas corresponding to neuropsychological function.
Methods and Findings
We conducted a cross-sectional study of 31 children (19 with OSA and 12 healthy controls, aged 6–16 y) group-matched by age, ethnicity, gender, and socioeconomic status. Participants underwent polysomnography and neuropsychological assessments. Proton magnetic resonance spectroscopic imaging was performed on a subset of children with OSA and on matched controls. Neuropsychological test scores and mean neuronal metabolite ratios of target brain areas were compared.
Relative to controls, children with severe OSA had significant deficits in IQ and executive functions (verbal working memory and verbal fluency). Children with OSA demonstrated decreases of the mean neuronal metabolite ratio N-acetyl aspartate/choline in the left hippocampus (controls: 1.29, standard deviation [SD] 0.21; OSA: 0.91, SD 0.05; p = 0.001) and right frontal cortex (controls: 2.2, SD 0.4; OSA: 1.6, SD 0.4; p = 0.03).
Conclusions
Childhood OSA is associated with deficits of IQ and executive function and also with possible neuronal injury in the hippocampus and frontal cortex. We speculate that untreated childhood OSA could permanently alter a developing child's cognitive potential.
Childhood obstructive sleep apnea is associated with deficits of IQ and executive function and also with possible neuronal injury in the hippocampus and frontal cortex.
Editors' Summary
Background.
Sleep is essential for health, and in children it is crucial to normal development. Symptomatic childhood sleep-disordered breathing (SDB) is the name for a range of conditions in which children have difficulties with breathing when they are asleep. The conditions range from simple snoring to the most severe condition, known as obstructive sleep apnea (OSA). Apnea means a temporary absence of breathing, and in OSA this is caused by a temporary but repeated blockage of the flow of air to the lungs. In children, OSA occurs for a number of reasons including enlarged tonsils, long-term allergy, and obesity. About two in every hundred children have OSA. The symptoms of OSA are loud snoring at night, disrupted, restless sleep, undue tiredness, and difficulties in concentration. The main test for it is a sleep study (polysomnography). If untreated, researchers believe that it may lead to a number of long-term problems with health and learning; children with disorders of sleep have been shown to have memory problems, lower general intelligence, and worse executive function (the ability to adapt to new situations), and may have behavioral problems similar to those of attention deficit hyperactivity disorder (ADHD).
Why Was This Study Done?
Adults with sleep apnea have been shown to have abnormalities of parts of their brain, specifically the frontal cortex, cerebellum, and hippocampus, but so far there are no data on whether there are similar changes in children. Children with sleep apnea may have cognitive deficits, but the research on this topic is limited.
What Did the Researchers Do and Find?
The researchers wanted to investigate the brains of children with OSA to see if there was any evidence of changes in the brain and if these changes were associated with any learning problems. They studied 31 children (19 with OSA and 12 healthy controls, aged 6–16 y). Participants underwent polysomnography and neuropsychological assessments, such as IQ tests and tests of their ability to perform tasks involving decision making. Some of the children also had specialized scans of their brains (known as proton magnetic resonance spectroscopic imaging) that can measure the levels of certain metabolites—substances that are produced as a result of brain activity. The researchers then compared the neuropsychological test scores with the levels of the metabolites. They found that relative to controls, children with severe OSA had lower IQ and ability to perform tasks involving decision making. Children with OSA also had changes in metabolites in the brain similar to those seen in diseases in which there is damage to brain cells.
What Do These Findings Mean?
It seems clear that OSA in children is associated with learning problems, and that these learning problems may in turn be associated with changes in brain metabolites. The changes in metabolites are not necessarily permanent—in other diseases where changes have been found they can be reversed with treatment. If these results are confirmed in other children with OSA, it will highlight the importance of treating children for OSA as soon as possible. In addition, the measurement of metabolites may be a way of measuring how well children are responding to treatment.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030301.
MedlinePlus's encyclopedia has an entry on sleep apnea
The American Sleep Apnea Association has information about having a child investigated for sleep apnea
The National Sleep Foundation also provides information about sleep disorders
doi:10.1371/journal.pmed.0030301
PMCID: PMC1551912  PMID: 16933960
11.  Body Mass Index, Gender, and Ethnic Variations Alter the Clinical Implications of the Epworth Sleepiness Scale in Patients with Suspected Obstructive Sleep Apnea§ 
Introduction:
The Epworth Sleepiness Scale (ESS) is often used in the evaluation of obstructive sleep apnea (OSA), though questions remain about the influence gender, ethnicity, and body morphometry have in the responses to this questionnaire. The aim of this study was to examine differences in ESS scores between various demographic groups of patients referred for polysomnography, and the relationship of these score to sleep-disordered breathing
Methods:
Nineteen hundred consecutive patients referred for polysomnographic diagnosis of OSA completed questionnaires, including demographic data and ESS. OSA was determined based on a respiratory disturbance index (RDI) ≥15 by polysomnography.
Results:
In this high risk population for OSA, the ESS was 10.7 ± 5.6. The highest ESS scores were seen in obese males; non-obese females and non-obese Caucasian males scored the lowest. ESS was weakly correlated with RDI (r = 0.17, P < 0.0001). The sensitivity of ESS for the diagnosis of OSA was 54% and the specificity was 57%. The positive (PPV) and negative (NPV) predictive values were 64% and 47%, respectively. In obese subjects, the sensitivity and specificity were 55% and 53%, compared with 47% and 63% in non-obese subjects. In obese, Hispanic males, the sensitivity, specificity, and PPV were 59%, 54%, and 84%, respectively. In non-obese, Caucasian females, the sensitivity, specificity, and NPV were 43%, 59%, and 72%.
Conclusions:
The ESS appears to be affected by many factors, including gender, ethnicity, and body morphometry. The ability of the ESS to predict OSA is modest, despite a significant correlation with the severity of OSA. The test characteristics improve significantly when applied to select populations, especially those at risk for OSA.
doi:10.2174/1874306401206010020
PMCID: PMC3367266  PMID: 22670164
Ethnicity; gender; obstructive sleep apnea; epworth sleepiness scale; screening.
12.  Overnight fluid shifts in subjects with and without obstructive sleep apnea 
Journal of Thoracic Disease  2014;6(12):1736-1741.
Objective
To investigate the characteristics of baseline body fluid content and overnight fluid shifts between non-obstructive sleep apnea (non-OSA) and obstructive sleep apnea (OSA) subjects.
Methods
A case-controlled study was performed between February 2013 and January 2014, with 36 (18 OSA and 18 non-OSA) outpatients enrolled in this study. Polysomnographic parameters and results of body fluid were compared between the two groups.
Results
There were no differences in age, weight, and body mass index (BMI) between groups. Compared with the non-OSA group, OSA group had significantly higher neck circumference (NC) and fluid volume shift in the legs. OSA patients had higher left and right leg fluid indices than non-OSA subjects. There were significant correlations between apnoea-hypopnoea index and baseline fluid indices in both legs as well as the reduction in overnight change in both legs fluid volume. The increase in NC was also significantly correlated with the reduction in overnight change in both legs fluid volume, but not with the change in head and neck fluid volume. There were significant correlations between change in NC and increased fluid shifts in head and neck volume.
Conclusions
OSA patients had a higher baseline fluid content in both legs as compared with non-OSA subjects, which may be the basic factor with regards to fluid shifts in OSA patients. The increase in head and neck fluid shift volume did not directly correlate with the severity of OSA.
doi:10.3978/j.issn.2072-1439.2014.11.19
PMCID: PMC4283308  PMID: 25589967
Obstructive sleep apnea (OSA); fluid shift; body composition analysis
13.  Inflammatory Markers and Obstructive Sleep Apnea in Obese Children: The NANOS Study 
Mediators of Inflammation  2014;2014:605280.
Introduction. Obesity and obstructive sleep apnea syndrome (OSA) are common coexisting conditions associated with a chronic low-grade inflammatory state underlying some of the cognitive, metabolic, and cardiovascular morbidities. Aim. To examine the levels of inflammatory markers in obese community-dwelling children with OSA, as compared to no-OSA, and their association with clinical and polysomnographic (PSG) variables. Methods. In this cross-sectional, prospective multicenter study, healthy obese Spanish children (ages 4–15 years) were randomly selected and underwent nocturnal PSG followed by a morning fasting blood draw. Plasma samples were assayed for multiple inflammatory markers. Results. 204 children were enrolled in the study; 75 had OSA, defined by an obstructive respiratory disturbance index (RDI) of 3 events/hour total sleep time (TST). BMI, gender, and age were similar in OSA and no-OSA children. Monocyte chemoattractant protein-1 (MCP-1) and plasminogen activator inhibitor-1 (PAI-1) levels were significantly higher in OSA children, with interleukin-6 concentrations being higher in moderate-severe OSA (i.e., AHI > 5/hrTST; P < 0.01), while MCP-1 levels were associated with more prolonged nocturnal hypercapnia (P < 0.001). Conclusion. IL-6, MCP-1, and PAI-1 are altered in the context of OSA among community-based obese children further reinforcing the proinflammatory effects of sleep disorders such as OSA. This trial is registered with ClinicalTrials.gov NCT01322763.
doi:10.1155/2014/605280
PMCID: PMC4058796  PMID: 24991089
14.  Obstructive Sleep Apnea and Risk of Cardiovascular Events and All-Cause Mortality: A Decade-Long Historical Cohort Study 
PLoS Medicine  2014;11(2):e1001599.
Tetyana Kendzerska and colleagues explore the association between physiological measures of obstructive sleep apnea other than the apnea-hypopnea index and the risk of cardiovascular events.
Please see later in the article for the Editors' Summary
Background
Obstructive sleep apnea (OSA) has been reported to be a risk factor for cardiovascular (CV) disease. Although the apnea-hypopnea index (AHI) is the most commonly used measure of OSA, other less well studied OSA-related variables may be more pathophysiologically relevant and offer better prediction. The objective of this study was to evaluate the relationship between OSA-related variables and risk of CV events.
Methods and Findings
A historical cohort study was conducted using clinical database and health administrative data. Adults referred for suspected OSA who underwent diagnostic polysomnography at the sleep laboratory at St Michael's Hospital (Toronto, Canada) between 1994 and 2010 were followed through provincial health administrative data (Ontario, Canada) until May 2011 to examine the occurrence of a composite outcome (myocardial infarction, stroke, congestive heart failure, revascularization procedures, or death from any cause). Cox regression models were used to investigate the association between baseline OSA-related variables and composite outcome controlling for traditional risk factors. The results were expressed as hazard ratios (HRs) and 95% CIs; for continuous variables, HRs compare the 75th and 25th percentiles. Over a median follow-up of 68 months, 1,172 (11.5%) of 10,149 participants experienced our composite outcome. In a fully adjusted model, other than AHI OSA-related variables were significant independent predictors: time spent with oxygen saturation <90% (9 minutes versus 0; HR = 1.50, 95% CI 1.25–1.79), sleep time (4.9 versus 6.4 hours; HR = 1.20, 95% CI 1.12–1.27), awakenings (35 versus 18; HR = 1.06, 95% CI 1.02–1.10), periodic leg movements (13 versus 0/hour; HR = 1.05, 95% CI 1.03–1.07), heart rate (70 versus 56 beats per minute [bpm]; HR = 1.28, 95% CI 1.19–1.37), and daytime sleepiness (HR = 1.13, 95% CI 1.01–1.28).The main study limitation was lack of information about continuous positive airway pressure (CPAP) adherence.
Conclusion
OSA-related factors other than AHI were shown as important predictors of composite CV outcome and should be considered in future studies and clinical practice.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder, particularly among middle-aged and elderly people. It is characterized by apnea—a brief interruption in breathing that lasts at least 10 seconds—and hypopnea—a decrease of more than 50% in the amplitude of breathing that lasts at least 10 seconds or clear but smaller decrease in amplitude associated with either oxygen desaturation or an arousal. Patients with OSA experience numerous episodes of apnea and hypopnea during the night; severe OSA is defined as having 30 or more episodes per hour (an apnea-hypopnea index [AHI] of >30). These breathing interruptions occur when relaxation of the upper airway muscles decreases the airflow, which lowers the amount of oxygen in the blood. As a result, affected individuals frequently wake from deep sleep as they struggle to breathe. Symptoms of OSA include loud snoring and daytime sleepiness. Treatments include lifestyle changes such as losing weight (excess fat around the neck increases airway collapse) and smoking cessation. For severe OSA, doctors recommend continuous positive airway pressure (CPAP), in which a machine blows pressurized air through a face mask into the airway to keep it open.
Why Was This Study Done?
OSA can be life-threatening. Most directly, daytime sleepiness can cause accidents, but OSA is also associated with an increased risk of developing cardiovascular disease (CVD, disease that affects the heart and the circulation). To date, studies that have investigated the association between OSA and the risk of myocardial infarction (heart attack), congestive heart failure, stroke, and other CVDs have used the AHI to diagnose and categorize the severity of OSA. However, by focussing on AHI, clinicians and researchers may be missing opportunities to improve their ability to predict which patients are at the highest risk of CVD. In this historical cohort study, the researchers investigate the association between other OSA-related variables (for example, blood oxygen saturation and sleep fragmentation) and the risk of cardiovascular events and all-cause mortality (death). A historical cohort study examines the medical records of groups of individuals who have different characteristics at baseline for the subsequent occurrence of specific outcomes.
What Did the Researchers Do and Find?
The researchers used administrative data (including hospitalization records and physicians' claims for services supplied to patients) to follow up adults referred for suspected OSA who underwent diagnostic polysomnography (a sleep study) at a single Canadian hospital between 1994 and 2010. A database of the polysomnography results provided information on OSA-related variables for all the study participants. Over an average follow-up of about 6 years, 11.5% of the 10,149 participants were hospitalized for a myocardial infarction, stroke, or congestive heart failure, underwent a revascularization procedure (an intervention that restores the blood supply to an organ or tissue after CVD has blocked a blood vessel), or had died from any cause. After adjusting for multiple established risk factors for CVD such as smoking and age in Cox regression models (a statistical approach that examines associations between patient variables and outcomes), several OSA-related variables (but not AHI) were significant predictors of CVD. The strongest OSA-related predictor of cardiovascular events or all-cause mortality was total sleep time spent with oxygen saturation below 90%, which increased the risk of a cardiovascular event or death by 50%. Other statistically significant OSA-related predictors (predictors that were unlikely to be associated with the outcome through chance) of cardiovascular events or death included total sleep time, number of awakenings, frequency of periodic leg movements, heart rate, and daytime sleepiness.
What Do These Findings Mean?
These findings indicate that OSA-related factors other than AHI are important predictors of the composite outcome of a cardiovascular event or all-cause mortality. Indeed, although AHI was significantly associated with the researchers' composite outcome in an analysis that did not consider other established risk factors for CVD (“confounders”), the association became non-significant after controlling for potential confounders. The accuracy of these findings, which need to be confirmed in other settings, is likely to be limited by the lack of information available about the use of CPAP by study participants and by the lack of adjustment for some important confounders. Importantly, however, these findings suggest that OSA-related factors other than AHI should be considered as predictors of CVD in future studies and in clinical practice.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001599.
The US National Heart Lung and Blood Institute has information (including several videos) about obstructive sleep apnea (in English and Spanish), sleep studies, heart disease, and other cardiovascular diseases (some information in English and Spanish)
The UK National Health Service Choices website provides information (including personal stories) about sleep apnea and about cardiovascular disease
The not-for-profit American Sleep Apnea Association provides detailed information about sleep apnea for patients and health-care professionals, including personal stories about the condition
The MedlinePlus encyclopedia has pages on obstructive sleep apnea and on polysomnography; MedlinePlus provides links to further information and advice about obstructive sleep apnea, heart diseases, and vascular diseases (in English and Spanish)
doi:10.1371/journal.pmed.1001599
PMCID: PMC3913558  PMID: 24503600
15.  Metabolic syndrome, insulin resistance, fibrinogen, homocysteine, leptin, and C-reactive protein in obese patients with obstructive sleep apnea syndrome 
Annals of Thoracic Medicine  2011;6(3):120-125.
OBJECTIVE:
The prevalence of obstructive sleep apnea syndrome (OSAS) and metabolic syndrome is increasing worldwide, in part linked to epidemic of obesity. The purposes of this study were to establish the rate of metabolic syndrome and to compare fibrinogen, homocysteine, high-sensitivity C-reactive protein (hsCRP), leptin levels, and homeostasis model assessment insulin resistance (HOMA-IR) in the obese patients with and without OSAS.
METHODS:
The study population included 36 consecutive obese patients with OSAS (23 males; mean age, 50.0 ±19.7 years), and 34 obese patients without OSAS (17 males; mean age, 49.7±11.1 years) were enrolled as control group. Metabolic syndrome was investigated; fibrinogen, homocysteine, CRP, and leptin levels were measured, and IR was assessed.
RESULTS:
Metabolic syndrome was found in 17 (47.2%) obese OSAS patients, whereas only 29.4% of obese subjects had metabolic syndrome (P > 0.05). Obese patients with OSAS had significantly higher mean levels of triglyceride (P < 0.001), total-cholesterol (P = 0.003), low-density lipoprotein-cholesterol (P = 0.001), fasting glucose (P = 0.01), HOMA-IR (P <0.001), thyroid-stimulating hormone (P = 0.03), fibrinogen (P < 0.003), hsCRP (P <0.001), and leptin (P = 0.03) than control group . Besides, leptin level was positively correlated with waist (r = 0.512, P = 0.03) and neck circumferences (r = 0.547, P = 0.03), and fasting glucose (r = 0.471, P = 0.04) in OSAS patients, but not in obese subjects.
CONCLUSION:
This study demonstrated that obese OSAS patients may have an increased rate of metabolic syndrome and higher levels of serum lipids, fasting glucose, IR, leptin, fibrinogen, and hsCRP than obese subjects without sleep apnea. Thus, clinicians should be encouraged to systematically evaluate the presence of metabolic abnormalities in OSAS and vice versa.
doi:10.4103/1817-1737.82440
PMCID: PMC3131753  PMID: 21760842
C-reactive protein; fibrinogen; homocysteine; insulin resistance; leptin; metabolic syndrome; obesity; obstructive sleep apnea syndrome
16.  Retinal nerve fiber layer thickness changes in obstructive sleep apnea syndrome: one year follow-up results 
AIM
To investigate the retinal nerve fiber layer (RNFL) thickness changes in patients with obstructive sleep apnea syndrome (OSAS) for one year follow-up. To discuss the possibility of detecting tendency of glaucoma in this population by using spectral domain optical coherence tomography (3D-OCT-2000 Spectral domain).
METHODS
After polysomnographic study, all subjects (64 OSAS patients and 40 controls) underwent detailed ophthalmological examination. After these examinations, patients with glaucoma and patients who had ophthalmological and/or systemic disease were excluded from the study. Totally, 20 patients in OSAS group and five patients in controls were excluded from the study in the first examination and follow-up period. The RNFL thickness was assessed with OCT. Forty-four OSAS patients and 35 control subjects were followed up 12mo. RNFL thickness change and OSAS patients were evaluated for severity of disease by Apnea-Hypopnea Index (AHI).
RESULTS
Forty-four OSAS patients and 35 controls were enrolled in the study. Statistically significance was found between OSAS patients and controls at the 12th mo. Average RNFL thickness was found to be significantly lower in last measurements in OSAS patients when compared with first measurements and control subjects (P<0.001, 0.002, respectively). There was a statistically significant correlation among AHI, and RNFL thickness (P<0.05).
CONCLUSION
The results suggest that the patients with OSAS were related with a proportional decrease in the RNFL thickness. These patients should be followed up regularly for glaucomatous changes. Detecting more RNFL thinning in severe OSAS was important.
doi:10.3980/j.issn.2222-3959.2014.04.22
PMCID: PMC4137211  PMID: 25161947
obstructive sleep apnea syndrome; optical coherence tomography; retinal nerve fiber layer thickness
17.  Upper Airway Structure and Body Fat Composition in Obese Children with Obstructive Sleep Apnea Syndrome 
Rationale: Mechanisms leading to obstructive sleep apnea syndrome (OSAS) in obese children are not well understood.
Objectives: The aim of the study was to determine anatomical risk factors associated with OSAS in obese children as compared with obese control subjects without OSAS.
Methods: Magnetic resonance imaging was used to determine the size of upper airway structure, and body fat composition. Paired analysis was used to compare between groups. Mixed effects regression models and conditional multiple logistic regression models were used to determine whether body mass index (BMI) Z-score was an effect modifier of each anatomic characteristic as it relates to OSAS.
Measurements and Main Results: We studied 22 obese subjects with OSAS (12.5 ± 2.8 yr; BMI Z-score, 2.4 ± 0.4) and 22 obese control subjects (12.3 ± 2.9 yr; BMI Z-score, 2.3 ± 0.3). As compared with control subjects, subjects with OSAS had a smaller oropharynx (P < 0.05) and larger adenoid (P < 0.01), tonsils (P < 0.05), and retropharyngeal nodes (P < 0.05). The size of lymphoid tissues correlated with severity of OSAS whereas BMI Z-score did not have a modifier effect on these tissues. Subjects with OSAS demonstrated increased size of parapharyngeal fat pads (P < 0.05) and abdominal visceral fat (P < 0.05). The size of these tissues did not correlate with severity of OSAS and BMI Z-score did not have a modifier effect on these tissues.
Conclusions: Upper airway lymphoid hypertrophy is significant in obese children with OSAS. The lack of correlation of lymphoid tissue size with obesity suggests that this hypertrophy is caused by other mechanisms. Although the parapharyngeal fat pads and abdominal visceral fat are larger in obese children with OSAS we could not find a direct association with severity of OSAS or with obesity.
doi:10.1164/rccm.201008-1249OC
PMCID: PMC3081285  PMID: 20935105
lymphoid hypertrophy; MRI; obese children
18.  The Potential Association between Obstructive Sleep Apnea and Diabetic Retinopathy in Severe Obesity—The Role of Hypoxemia 
PLoS ONE  2013;8(11):e79521.
Background
Obstructive sleep apnea (OSA) is common in obese patients with type 2 diabetes mellitus (DM) and may contribute to diabetic microvascular complications.
Methods
To investigate the association between OSA, hypoxemia during sleep, and diabetic retinal complications in severe obesity. This was a prospective observational study of 93 obese patients mean (SD) age: 52(10) years; mean (SD) body mass index (BMI): 47.3(8.3) kg/m2) with DM undergoing retinal screening and respiratory monitoring during sleep. OSA was defined as apnea-hypopnea index (AHI) of ≥15 events/hour, resulting in two groups (OSA+ vs. OSA−).
Results
Forty-six patients were OSA+: median (95% CI) AHI = 37(23–74)/hour and 47 were OSA–ve (AHI = 7(4–11)/hour). Both groups were similar for ethnicity, BMI, cardiovascular co-morbidities, diabetes duration, HbA1c, and insulin treatment (p>0.05). The OSA+ group was significantly more hypoxemic. There was no significant difference between OSA+ and OSA− groups for the presence of retinopathy (39% vs. 38%). More OSA+ subjects had maculopathy (22% vs. 13%), but this did not reach statistical significance. Logistic regression analyses showed that AHI was not significantly associated with the presence of retinopathy or maculopathy (p>0.05). Whilst minimum oxygen saturation was not significantly associated with retinopathy, it was an independent predictor for the presence of maculopathy OR = 0.79 (95% CI: 0.65–0.95; p<0.05), after adjustment.
Conclusions
The presence of OSA, as determined by AHI, was not associated with diabetic retinal complications. In contrast, severity of hypoxemia during sleep (minimum oxygen saturations) may be an important factor. The importance of hypoxia in the development of retinal complications in patients with OSA remains unclear and further studies assessing the pathogenesis of hypoxemia in patients with OSA and diabetic retinal disease are warranted.
doi:10.1371/journal.pone.0079521
PMCID: PMC3832592  PMID: 24260240
19.  Comparison of cardiovascular co-morbidities and CPAP use in patients with positional and non-positional mild obstructive sleep apnea 
BMC Pulmonary Medicine  2014;14(1):153.
Background
This retrospective cohort study aimed to determine if there are differences in cardiovascular co-morbidities, blood pressure (BP) and continuous positive airway pressure (CPAP) use between patients with positional-dependent and nonpositional-dependent obstructive sleep apnea (OSA).
Methods
Patients who were referred for overnight polysomnography for suspected OSA between 2007 and 2011 were screened. A total of 371 patients with OSA were included for analysis and divided into six groups according to positional-dependency and severity of OSA: positional mild (n = 52), positional moderate (n = 29), positional severe (n = 24), non-positional mild (n = 18), non-positional moderate (n = 70) and non-positional severe group (n = 178). The six groups were compared for anthropometric and polysomnographic variables, presence of cardiovascular co-morbidities, morning and evening BP and the changes between evening and morning BP, and CPAP device usage patterns.
Results
Demographic and anthropometric variables showed non-positional severe OSA had poor sleep quality and higher morning blood pressures. Positional mild OSA had the lowest cardiovascular co-morbidities. Overall CPAP acceptance was 45.6%. Mild OSA patients had the lowest CPAP acceptance rate (10%), followed by moderate group (37.37%) and severe group (61.88%, P < 0.001). However, the significant difference in CPAP acceptance across OSA severity disappeared when the data was stratified by positional dependency.
Conclusions
This study found that positional mild OSA had less cardiovascular co-morbidities compared with subjects with positional severe OSA. Independent of posture, CPAP acceptance in patients with mild OSA was low, but CPAP compliance was similar in CPAP acceptors regardless of posture dependency of OSA. Since there are increasing evidences of greater cardiovascular risk for untreated mild OSA, improving CPAP acceptance among mild OSA patients may be clinically important regardless of posture dependency.
doi:10.1186/1471-2466-14-153
PMCID: PMC4189203  PMID: 25257571
Obstructive sleep apnea; Positional sleep apnea; Cardiovascular co-morbidities; Hypertension; Continuous positive airway pressure
20.  Adipocytokines in sleep apnea syndrome 
European Journal of Medical Research  2009;14(Suppl 4):255-258.
Objective
Biomarkers of adipose tissue may affect glucose and lipid metabolism and present pro-inflammatory properties, thus could be involved in the pathobiochemistry of cardiovascular disease (CVD). The coexistence of sleep apnea syndrome (OSA) and metabolic risk factors of CVD is worth explaining. The aim of the study was to compare the serum adipocytokines in subjects with and without OSA, who had all elevated body mass index (BMI).
Methods
Overweight (BMI: 25.0-29.9 kg/m2) and obese (BMI: 30.0-39.9 kg/m2) OSA-suspected Caucasian males, aged 30-63, with no acute disease or chronic disorder underwent polysomnographic evaluation to select OSA-positive (AHI ≥ 5) and OSA-negative (AHI < 5) subjects. Four subgroups were created of 18 persons each: Over(weight)-OSA-Neg, Over-OSA-Pos, Obese-OSA-Neg, Obese-OSA-Pos. In all subjects, plasma carbohydrate and lipid metabolism parameters, and serum uric acid, resistin and leptin concentrations were determined.
Results
A decreased resistin level was observed in Over-OSA-Pos vs. Over-OSA-Neg subjects (P = 0.037) as well as in Obese-OSA-Pos vs. Obese-OSA-Neg (P = 0.045). No differences in leptin concentrations were observed. A positive correlation between leptin and BMI was in both overweight subgroups and a negative one between resistin and fasting glucose was in both obese subgroups.
Conclusions
OSA may decrease the serum resistin level in subjects with excess body mass and also may contribute to glucose metabolism, but has no influence on the leptin level.
doi:10.1186/2047-783X-14-S4-255
PMCID: PMC3521364  PMID: 20156767
obstructive sleep apnea; body mass index; adipocytokines; leptin; resistin
21.  Association of Adenotonsillectomy with Asthma Outcomes in Children: A Longitudinal Database Analysis 
PLoS Medicine  2014;11(11):e1001753.
Rakesh Bhattacharjee and colleagues use data from a US private health insurance database to compare asthma severity measures in children one year before and one year after they underwent adenotonsillectomy with asthma measures in those who did not undergo adenotonsillectomy.
Please see later in the article for the Editors' Summary
Background
Childhood asthma and obstructive sleep apnea (OSA), both disorders of airway inflammation, were associated in recent observational studies. Although childhood OSA is effectively treated by adenotonsillectomy (AT), it remains unclear whether AT also improves childhood asthma. We hypothesized that AT, the first line of therapy for childhood OSA, would be associated with improved asthma outcomes and would reduce the usage of asthma therapies in children.
Methods and Findings
Using the 2003–2010 MarketScan database, we identified 13,506 children with asthma in the United States who underwent AT. Asthma outcomes during 1 y preceding AT were compared to those during 1 y following AT. In addition, 27,012 age-, sex-, and geographically matched children with asthma without AT were included to examine asthma outcomes among children without known adenotonsillar tissue morbidity. Primary outcomes included the occurrence of a diagnostic code for acute asthma exacerbation (AAE) or acute status asthmaticus (ASA). Secondary outcomes included temporal changes in asthma medication prescriptions, the frequency of asthma-related emergency room visits (ARERs), and asthma-related hospitalizations (ARHs). Comparing the year following AT to the year prior, AT was associated with significant reductions in AAE (30.2%; 95% CI: 25.6%–34.3%; p<0.0001), ASA (37.9%; 95% CI: 29.2%–45.6%; p<0.0001), ARERs (25.6%; 95% CI: 16.9%–33.3%; p<0.0001), and ARHs (35.8%; 95% CI: 19.6%–48.7%; p = 0.02). Moreover, AT was associated with significant reductions in most asthma prescription refills, including bronchodilators (16.7%; 95% CI: 16.1%–17.3%; p<0.001), inhaled corticosteroids (21.5%; 95% CI: 20.7%–22.3%; p<0.001), leukotriene receptor antagonists (13.4%; 95% CI: 12.9%–14.0%; p<0.001), and systemic corticosteroids (23.7%; 95% CI: 20.9%–26.5%; p<0.001). In contrast, there were no significant reductions in these outcomes in children with asthma who did not undergo AT over an overlapping follow-up period. Limitations of the MarketScan database include lack of information on race and obesity status. Also, the MarketScan database does not include information on children with public health insurance (i.e., Medicaid) or uninsured children.
Conclusions
In a very large sample of privately insured children, AT was associated with significant improvements in several asthma outcomes. Contingent on validation through prospectively designed clinical trials, this study supports the premise that detection and treatment of adenotonsillar tissue morbidity may serve as an important strategy for improving asthma control.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
The global burden of asthma has been rising steadily over the past few decades. Nowadays, about 200–300 million adults and children worldwide are affected by asthma, a chronic condition caused by inflammation of the airways (the tubes that carry air in and out of the lungs). Although asthma can develop at any age, it is often diagnosed in childhood—asthma is one of the commonest chronic diseases in children. In the US, for example, asthma affects around 7.1 million children under the age of 18 years and is the third leading cause of hospitalization of children under the age of 15 years. In people with asthma, the airways can react very strongly to allergens such as animal fur or to irritants such as cigarette smoke. Exercise, cold air, and infections can trigger asthma attacks, which can be fatal. The symptoms of asthma include wheezing, coughing, chest tightness, and shortness of breath. Asthma cannot be cured, but drugs can relieve its symptoms and prevent acute asthma attacks.
Why Was This Study Done?
Recent studies have found an association between severe childhood asthma and obstructive sleep apnea (OSA). In OSA, airway inflammation promotes hypertrophy (excess growth) of the adenoids and the tonsils, immune system tissues in the upper airway. During sleep, the presence of hypertrophic adenotonsillar tissues predisposes the walls of the throat to collapse, which results in apnea—a brief interruption in breathing. People with OSA often snore loudly and frequently wake from deep sleep as they struggle to breathe. Childhood OSA, which affects 2%–3% of children, can be effectively treated by removal of the adenoids and tonsils (adenotonsillectomy). Given the association between childhood OSA and severe asthma and given the involvement of airway inflammation in both conditions, might adenotonsillectomy also improve childhood asthma? Here, the researchers analyze data from the MarketScan database, a large database of US patients with private health insurance, to investigate whether adenotonsillectomy is associated with improvements in asthma outcomes and with reductions in the use of asthma therapies in children.
What Did the Researchers Do and Find?
The researchers used the database to identify 13,506 children with asthma who had undergone adenotonsillectomy and to obtain information about asthma outcomes among these children for the year before and the year after the operation. Because asthma severity tends to decrease with age, the researchers also used the database to identify 27,012 age-, sex-, and geographically matched children with asthma who did not have the operation so that they could examine asthma outcomes over an equivalent two-year period in the absence of complications related to adenotonsillar hypertrophy. Comparing the year after adenotonsillectomy with the year before the operation, adenotonsillectomy was associated with a 30% reduction in acute asthma exacerbations, a 37.9% reduction in acute status asthmaticus (an asthma attack that is unresponsive to the drugs usually used to treat attacks), a 25.6% reduction in asthma-related emergency room visits, and a 35.8% reduction in asthma-related hospitalizations. By contrast, among the control children, there was only a 2% reduction in acute asthma exacerbations and only a 7% reduction in acute status asthmaticus over an equivalent two-year period. Adenotonsillectomy was also associated with significant reductions (changes unlikely to have occurred by chance) in prescription refills for most types of drugs used to treat asthma, whereas there were no significant reductions in prescription refills among children with asthma who had not undergone adenotonsillectomy. The study was limited by the lack of measures of race and obesity, which are both associated with severity of asthma.
What Do These Findings Mean?
These findings show that in a large sample of privately insured children in the US, adenotonsillectomy was associated with significant improvements in several asthma outcomes. These results do not show, however, that adenotonsillectomy caused a reduction in the severity of childhood asthma. It could be that the children who underwent adenotonsillectomy (but not those who did not have the operation) shared another unknown factor that led to improvements in their asthma over time. To prove a causal link, it will be necessary to undertake a randomized controlled trial in which the outcomes of groups of children with asthma who are chosen at random to undergo or not undergo adenotonsillectomy are compared. However, with the proviso that there are some risks associated with adenotonsillectomy, these findings suggest that the detection and treatment of adenotonsillar hypertrophy may help to improve asthma control in children.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001753.
The US Centers for Disease Control and Prevention provides information on asthma, including videos, games, and links to other resources for children with asthma
The American Lung Association provides detailed information about asthma and a fact sheet on asthma in children; it also has information about obstructive sleep apnea
The National Sleep Foundation provides information on snoring and obstructive sleep apnea in children
The UK National Health Service Choices website provides information (including some personal stories) about asthma, about asthma in children, and about obstructive sleep apnea
The “Global Asthma Report 2014” will be available in October 2014
MedlinePlus provides links to further information on asthma, on asthma in children, on sleep apnea, and on tonsils and adenoids (in English and Spanish)
doi:10.1371/journal.pmed.1001753
PMCID: PMC4219664  PMID: 25369282
22.  Effect of Treatment of Obstructive Sleep Apnea on Depressive Symptoms: Systematic Review and Meta-Analysis 
PLoS Medicine  2014;11(11):e1001762.
In a meta-analysis of randomized controlled trials, Matthew James and colleagues investigate the effects of continuous positive airway pressure or mandibular advancement devices on depression.
Please see later in the article for the Editors' Summary
Background
Obstructive sleep apnea (OSA) is associated with increased morbidity and mortality, and decreased quality of life. Treatment with continuous positive airway pressure (CPAP) or mandibular advancement devices (MADs) is effective for many symptoms of OSA. However, it remains controversial whether treatment with CPAP or MAD also improves depressive symptoms.
Methods and Findings
We performed a systematic review and meta-analysis of randomized controlled trials that examined the effect of CPAP or MADs on depressive symptoms in patients with OSA. We searched Medline, EMBASE, the Cochrane Central Registry of Controlled Trials, and PsycINFO from the inception of the databases until August 15, 2014, for relevant articles.
In a random effects meta-analysis of 19 identified trials, CPAP treatment resulted in an improvement in depressive symptoms compared to control, but with significant heterogeneity between trials (Q statistic, p<0.001; I2 = 71.3%, 95% CI: 54%, 82%). CPAP treatment resulted in significantly greater improvement in depressive symptoms in the two trials with a higher burden of depression at baseline (meta-regression, p<0.001). The pooled standardized mean difference (SMD) in depressive symptoms with CPAP treatment in these two trial populations with baseline depression was 2.004 (95% CI: 1.387, 2.621), compared to 0.197 (95% CI: 0.059, 0.334) for 15 trials of populations without depression at baseline. Pooled estimates of the treatment effect of CPAP were greater in parallel arm trials than in crossover trials (meta-regression, p = 0.076). Random effects meta-analysis of five trials of MADs showed a significant improvement in depressive symptoms with MADs versus controls: SMD = 0.214 (95% CI: 0.026, 0.401) without significant heterogeneity (I2 = 0%, 95% CI: 0%, 79%). Studies were limited by the use of depressive symptom scales that have not been validated specifically in people with OSA.
Conclusions
CPAP and MADs may be useful components of treatment of depressive symptoms in individuals with OSA and depression. The efficacy of CPAP and MADs compared to standard therapies for depression is unknown.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Obstructive sleep apnea (OSA) is a sleep-related breathing disorder that is particularly common among middle-aged and elderly people, although most are unaware that they have the condition. It is characterized by the occurrence of numerous brief (ten seconds or so) breathing interruptions during sleep. These “apneas” occur when relaxation of the upper airway muscles decreases airflow, which lowers the level of oxygen in the blood. Consequently, affected individuals are frequently aroused from deep sleep as they struggle to breathe. Symptoms of OSA include loud snoring and daytime sleepiness. Treatments include lifestyle changes such as losing weight (excess fat around the neck increases airway collapse) and smoking cessation. Mild to moderate OSA can also be treated using a mandibular advancement device (MAD), a “splint” that fits inside the mouth and pushes the jaw and tongue forward to increase the space at the back of the throat and reduce airway narrowing. For severe OSA, doctors recommend continuous positive airway pressure (CPAP), in which a machine blows pressurized air into the airway through a facemask to keep it open.
Why Was This Study Done?
OSA is a serious condition that is associated with an increased risk of illness and death. Clinical depression (long-lasting, overwhelming feelings of sadness and hopelessness), for example, is common among people with OSA. The interaction between these frequently co-morbid (co-existing) conditions is complex. The sleep disruption and weight gain that are often associated with depression could cause or worsen OSA. Conversely, OSA could trigger depression by causing sleep disruption and by inducing cognitive changes (changes in thinking) by intermittently starving the brain of oxygen. If the latter scenario is correct, then treating OSA with CPAP or MADs might improve depressive symptoms. Several trials have investigated this possibility, but their results have been equivocal. Here, the researchers undertake a systematic review and meta-analysis of randomized controlled trials that have examined the effect of CPAP or MADs on depressive symptoms in patients with OSA to find out whether treating co-morbid OSA in patients with depression can help to treat depression. A randomized controlled trial compares the outcomes of individuals chosen to receive different interventions through the play of chance, a systematic review uses predefined criteria to identify all the research on a given topic, and meta-analysis uses statistical methods to combine the results of several studies.
What Did the Researchers Do and Find?
The researchers identified 22 trials that investigated the effects of CPAP or MAD treatment in patients with OSA and that measured depressive symptoms before and after treatment. Meta-analysis of the results of 19 trials that provided information about the effect of CPAP on depressive symptoms indicated that CPAP improved depressive symptoms compared to the control intervention (usually sham CPAP) but revealed considerable heterogeneity (variability) between trials. Notably, CPAP treatment resulted in a greater improvement in depressive symptoms in trials in which there was a high prevalence of depression at baseline than in trials in which there was a low prevalence of depression at baseline. Moreover, the magnitude of this improvement in depressive symptoms in trials with a high prevalence of depression at baseline was large enough to be clinically relevant. Meta-analysis of five trials that provided information about the effect of MADs on depressive symptoms indicated that MADs also improved depressive symptoms compared to the control intervention (sham MAD).
What Do These Findings Mean?
These findings suggest that both CPAP and MAD treatment for OSA can result in modest improvements in depressive symptoms and that populations with high initial levels of depressive symptoms may reap the greatest benefits of CPAP treatment. These findings give no indication of the efficacy of CPAP and MADs compared to standard treatments for depression such as antidepressant medications. Moreover, their accuracy may be limited by methodological limitations within the trials included in the meta-analyses reported here. For example, the questionnaires used to measure depression in these trials were not validated for use in people with OSA. Further high-quality randomized controlled trials are therefore needed to confirm the findings of this systematic review and meta-analysis. For now, however, these findings suggest that the use of CPAP and MADs may help improve depressive symptoms among people with OSA.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001762.
The US National Heart, Lung, and Blood Institute has information (including several videos) about sleep apnea (in English and Spanish)
The UK National Health Service Choices website provides information and personal stories about obstructive sleep apnea and depression
The not-for-profit American Sleep Apnea Association provides detailed information about sleep apnea for patients and healthcare professionals, including personal stories about the condition
The US National Institute of Mental Health provides information on all aspects of depression (in English and Spanish)
The Anxiety and Depression Association of America provides information about sleep disorders
The MedlinePlus encyclopedia has a page on obstructive sleep apnea; MedlinePlus provides links to further information and advice about obstructive sleep apnea and about depression (in English and Spanish)
doi:10.1371/journal.pmed.1001762
PMCID: PMC4244041  PMID: 25423175
23.  Obstructive Airway Disease and Obstructive Sleep Apnea: Effect of Pulmonary Function 
Lung  2010;189(1):37-41.
This study sought to determine whether reduced pulmonary function in obstructive airway disease (OAD) is an independent risk factor for obstructive sleep apnea (OSA). This was a prospective observational study conducted at an outpatient pulmonary clinic. Adults with a known diagnosis of COPD/asthma were enrolled as OAD group. Family members without a history of COPD/asthma who accompanied these patients to the clinic were enrolled as a control group. The Berlin Questionnaire (BQ) was used to assess OSA risk in the OAD group and controls. Forced expiratory volume in 1 second (FEV1 % predicted) was determined from spirometry. The subjects at high risk for OSA were referred for a full overnight polysomnogram (PSG). The prevalence of patients with a high risk of OSA was 55.2% in the OAD group, which was higher than in the controls (7.5%, p < 0.0001). OAD subjects had a higher body mass index (BMI) and larger neck circumference than controls (p < 0.01). There was no difference in FEV1 % predicted between the OAD patients at high risk and low risk of OSA. On receiver operator curve (ROC) analysis, FEV1 % predicted was not a significant predictor of high OSA risk. Using logistic regression, FEV1 % predicted had no association with OSA risk. There was no correlation between FEV1 % predicted and total apnea-hypopnea index (AHI), oxygen desaturation index, % time spent below oxygen saturation 90%, and mean oxygen saturation on multiple regression analysis. OSA appears to be common in patients with COPD or asthma in an urban outpatient pulmonary clinic. However, the high prevalence of OSA in OAD patients appears to be due to obesity, and reduced pulmonary function is not an independent risk factor for OSA.
doi:10.1007/s00408-010-9270-3
PMCID: PMC3417329  PMID: 21132554
Asthma; Chronic obstructive pulmonary disease; COPD; Lung; Obstructive sleep apnea; OSA; Pulmonary function
24.  Association of Obstructive Sleep Apnea and Glucose Metabolism in Subjects With or Without Obesity 
Diabetes Care  2013;36(12):3909-3915.
OBJECTIVE
The purpose of this study was to investigate whether the impact of obstructive sleep apnea (OSA) on glucose metabolism was different according to the presence or absence of obesity.
RESEARCH DESIGN AND METHODS
A total of 1,344 subjects >40 years old from the Korean Genome and Epidemiology Study were included. OSA was detected by home portable sleep monitoring. Plasma glucose, HbA1c, and insulin resistance were compared according to OSA and obesity status. The associations between OSA and impaired fasting glucose (IFG), impaired glucose tolerance (IGT), IFG + IGT, and diabetes were evaluated in subjects with and without obesity after adjusting for several confounding variables. The effect of visceral obesity on this association was evaluated in 820 subjects who underwent abdominal computed tomography scanning.
RESULTS
In subjects without obesity, fasting glucose, 2-h glucose after 75-g glucose loading, and HbA1c were higher in those with OSA than in those without after controlling for age, sex, and BMI. In addition, the presence of OSA in nonobese subjects was associated with a higher prevalence of IFG + IGT and diabetes after adjusting for several confounding variables (odds ratio 3.15 [95% CI 1.44–6.90] and 2.24 [1.43–3.50] for IFG + IGT and diabetes, respectively). Further adjustment for visceral fat area did not modify this association. In contrast, in those with obesity, none of the abnormal glucose tolerance categories were associated with OSA.
CONCLUSIONS
The presence of OSA in nonobese individuals is significantly associated with impaired glucose metabolism, which can be responsible for future risk for diabetes and cardiovascular disease.
doi:10.2337/dc13-0375
PMCID: PMC3836097  PMID: 24101695
25.  Comparison of Low Resolution Electromagnetic Tomography Imaging Between Subjects With Mild and Severe Obstructive Sleep Apnea Syndrome: A Preliminary Study 
Psychiatry Investigation  2008;5(1):45-51.
Objective
The purpose of this study was to identify the regions of the brain associated with recurrent nocturnal chronic hypoxic episodes in patients with untreated obstructive sleep apnea syndrome (OSAS) using low-resolution electromagnetic tomography (LORETA) and quantitative electroencephalography (QEEG).
Methods
Nocturnal polysomnograph (NPSG) and subsequent morning electroencephalograph (EEG) were measured in 20 subjects with OSAS. Mild (n=10 ages 39.5±12.1 years) and severe (n=10 ages 41.7±13.6 years) right-handed male OSAS subjects were selected by interview and questionnaires including the NPSG, Beck Depression Inventory, Beck Anxiety Inventory, Epworth Sleepiness Scale, and Pittsburgh Sleep Quality Index. The LORETA and QEEG were compared between the severe and mild OSAS groups by frequency bands (delta 1-3 Hz, theta 4-7 Hz, alpha 8-12 Hz, beta1 13-18 Hz, beta2 19-21 Hz, beta3 22-30 Hz, and total 1-30 Hz) made by spectral analysis during resting with the eyes closed.
Results
The LORETA analysis showed decreased alpha activity at the right posterior cingulate gyrus (Brodmann area 23) in cases with severe OSAS compared to mild OSAS (p<0.05). For the QEEG, the absolute power of the alpha activity (8-12 Hz) was decreased in P3 (p=0.047), PZ (p=0.039) and O2 (p=0.04) in cases with severe OSAS compared to mild OSAS cases. The LORETA and QEEG analyses had similar results with regard to band, activation and location.
Conclusion
The decreased activity of the alpha frequency in the right posterior cingulate gyrus, in patients with severe OSAS compared to those with mild OSAS, suggests that chronic repeated short-term hypoxia during sleep, in OSAS, could provoke cortical brain dysfunction associated with cognitive dysfunction such as memory and attention.
doi:10.4306/pi.2008.5.1.45
PMCID: PMC2796088  PMID: 20046408
Obstructive sleep apnea syndrome; Low-resolution electromagnetic tomography; Quantitative electroencephalography; Hypoxic brain damage

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