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1.  Does ‘weight reduction’ help all adult snorers? 
Background:
Obesity is now a global epidemic. Obese people are at higher risk of snoring. Weight reduction could influence the prevalence of snoring. Present study tried to find out, whether weight reduction is of benefit in all adult snorers.
Materials and Methods:
It is a cross sectional study, on 349 subjects (196 males and 153 females). They and their spouses were asked for snoring habits. Their neck circumference, height and weight was measured and Body mass index (BMI) was calculated, and they were classified into low normal, high normal, pre-obese and obese BMI groups. Prevalence rates of snoring in different groups were compared, to find out any statistically significant difference, between them.
Results:
Statistically significant difference, in prevalence rates of snoring was found, when obese and pre-obese group were compared with normal BMI group, separately. No significant difference was found in prevalence rates, when comparison was made between obese and pre-obese group. Difference in prevalence of snoring, was also not significant, when comparison was made between low normal and high normal BMI groups. Neck circumference of snorers was significantly more than the neck circumference of non-snorers in all BMI groups. Gender wise difference, in prevalence of snoring was also not significant.
Conclusion:
Body mass index target needs to be set at 25 kg/m2, in weight reduction programmes, to achieve clinically relevant response in a snorer. There is no need to put extra emphasis, on further reduction of BMI. Weight reduction, is not helpful in all adult snorers, especially those with normal BMI, where other causes of snoring, like fat around upper airways, need to be considered.
doi:10.4103/0970-2113.106123
PMCID: PMC3644827  PMID: 23661911
Adult; body mass index; obesity; snoring; weight reduction
2.  Cephalometric measurements in snorers, non-snorers, and patients with sleep apnoea. 
Thorax  1991;46(6):419-423.
Cephalometry is often used to assess patients with sleep apnoea but whether these measurements differ from those in non-apnoeic snorers and how they are influenced by age is not clear. Cephalometric radiographs of patients with sleep apnoea were compared with those of snorers without sleep apnoea and those of non-snorers. Fifty two snorers with suspected sleep apnoea had a conventional sleep study and were divided into two groups: those with an apnoea-hypopnoea index greater than 10/h (n = 40, sleep apnoea group) and those whose apnoea-hypopnoea index was 10/h or less (n = 12, snorer group). The cephalometric measurements in these patients were compared with those of 34 non-snoring control subjects. Controls were subdivided into two groups: control group 1 included 17 subjects similar in age to the sleep apnoea and snorer groups (mean (SD) age 50.0 (10.9), 50.7 (9.4), and 50.6 (9.7) years); control group 2 included 15 young men (25.4 (2.6) years). The distance from the mandibular plane to the hyoid bone (MP-H) and the length of the soft palate were greater in the patients with sleep apnoea (28.7 (7.8) and 43.6 (5.0) mm) than in the snorers (23.7 (4.2) and 40.3 (4.9 mm). The MP-H was similar in snorers and age matched control subjects, but was significantly greater in the older than in the younger control subjects (22.1 (6.1) vs 17.0 (6.8]. The soft palate was longer in subjects who snored (both sleep apnoea patients and snorers) than in control subjects. The MP-H distance significantly correlated with age for all subjects (snorers and controls) and for the control subjects alone. This study shows that non-apnoeic snorers have cephalometric abnormalities that differ from those of patients with sleep apnoea and that cephalometric values are influenced by the subject's age.
Images
PMCID: PMC463188  PMID: 1858079
3.  Snoring, Inflammatory Markers, Adipokines and Metabolic Syndrome in Apparently Healthy Chinese 
PLoS ONE  2011;6(11):e27515.
Objective
Chronic low-grade inflammation and adipokines dysregulation are linked to mechanisms underscoring the pathogenesis of obesity-related metabolic disorders. Little is known about roles of these cytokines on the association between snoring and metabolic syndrome (MetS). We aimed to investigate whether a cluster of cytokines are related to snoring frequency and its association with MetS in apparently healthy Chinese.
Methods
Current analyses used a population-based sample including 1059 Shanghai residents aged 35–54 years. Self-reported snoring frequency was classified as never, occasionally and regularly. Fasting plasma glucose, lipid profile, insulin, C-reactive protein, interleukin-6, interleukin-18, lipopolysaccharide binding protein, high-molecular-weight adiponectin and leptin were measured. MetS was defined by the updated National Cholesterol Education Program Adult Treatment Panel III criteria for Asian-Americans.
Results
Overweight/obese subjects had significantly higher prevalence of regular snorers than their normal-weight counterparts (34.8% vs. 11.5%, P<0.001). Regular snoring was associated with unfavorable profile of inflammatory markers and adipokines. However, those associations were abolished after adjustment for body mass index (BMI) or waist circumference. The MetS risk (multivariate-adjusted odds ratio 5.41, 95% confidence interval 3.72–7.88) was substantially higher in regular snorers compared with non-snorers. Controlling for BMI remarkably attenuated the association (2.03, 1.26–3.26), while adjusting for inflammatory markers and adipokines showed little effects.
Conclusion
Frequent snoring was associated with an elevated MetS risk independent of lifestyle factors, adiposity, inflammatory markers and adipokines in apparently healthy Chinese. Whether snoring pattern is an economic and no-invasive indicator for screening high-risk persons needs to be addressed prospectively.
doi:10.1371/journal.pone.0027515
PMCID: PMC3217970  PMID: 22110665
4.  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
5.  Snoring and obstructive sleep apnoea syndrome among hypertensive Nigerians: Prevalence and clinical correlates 
Background
Obstructive sleep apnoea (OSA) syndrome is a common disorder in the community. Association between hypertension and sleep apnoea and /or snoring has been described. The Berlin questionnaire is a validated instrument that is used to identify individuals who are at risk for OSA. The study aim to describe the prevalence of snoring and OSA among hypertensive subjects in South Western, Nigeria.
Methods
This was a descriptive study conducted at the Cardiology clinic of Ladoke Akintola University of Technology LAUTECH Teaching Hospital, Osogbo, South West Nigeria. One hundred consecutive hypertensive patients were recruited from the clinic. The Berlin questionnaire and the Epworth sleepiness scale (ESS) were used to determine excessive daytime sleepiness and the risk of having OSA. Statistical analysis was done using SPSS 16.0. Data were summarized as means ± S.D and percentages.
Results
The study participants consisted of 40 males (40.0%). The demographic data were similar between both genders except that females had higher mean body mass index than males. The prevalence of snoring was 50.0%. 52% were categorized as being at high risk of having OSA. Snorers were more likely to be older, males and to have a higher fasting blood sugar than non-snorers.96% of snorers reported excessive daytime somnolence as predicted by the ESS score compared to 4% of non snorers. Prevalence of snoring was also higher among overweight and obese hypertensive subjects than normal body mass index hypertensive subjects.
Conclusion
Snoring is common among hypertensive subjects in South Western Nigeria. Clinically suspected OSA was similarly high in prevalence among them. Early identification and management may reduce the cardiovascular risk of hypertensive subjects.
PMCID: PMC3361213  PMID: 22655109
Snoring; sleep apnoea; hypertension; prevalence; clinical correlates; Nigeria
6.  Assessment of Snoring and obstructive sleep apnoea in a Nigerian university: Association with cardiovascular risk factors 
Background:
Snoring remains under diagnosed in general population. It however has significant morbidity and mortality risk factors with multiple effects on the cardiovascular system. The Berlin questionnaire is a worldwide validated instrument to identify those at increased risk for obstructive sleep apnoea (OSA).
Materials and Methods:
In all, 206 workers of LAUTECH were invited to participate in the study. The Berlin questionnaire was used for this study. It was a cross-sectional study. Socio-demographic and clinical data were taken with a data form. Statistical Package for the Social Sciences software (SPSS 17.0) was used for statistical analysis. P < 0.05 was taken as statistically significant value.
Results:
The study participants consisted of 96 males (46.6%) and 110 (53.4%) females. The mean age was 45.3 ± 7.9 years. The mean body mass index was 28.5 ± 6.0 kg/m². The frequency of occurrence of snoring was 91 (44.2%) including 50 males (54.9% and 41 females (37.3 %, P <0.05). Using the Berlin score, 63 (30.6%) including 34 females (30.9%) were assessed to be at high risk for OSA. Snorers were more likely to be at higher risk of OSA compared to non snorers: odd risk was 113.8, relative risk was 3.3. Snoring was most likely to be associated with obesity, elevated blood pressure and male gender in this study.
Conclusion:
We concluded that snoring and high risk for sleep apnoea is common among this unselected University population and they are closely related to many conventional cardiovascular risk factors. Appropriate interventional strategies are indicated to reduce the burden of the increased morbidity and mortality associated with sleep apnoea in our population.
doi:10.4103/0300-1652.144698
PMCID: PMC4262842  PMID: 25538364
High risk; Nigeria; obstructive sleep apnoea; sleep disordered breathing; snoring; University workers
7.  Snoring as a risk factor for ischaemic heart disease and stroke in men. 
The association of snoring with ischaemic heart disease and stroke was studied prospectively in 4388 men aged 40-69. The men were asked, in a questionnaire sent to them, whether they snored habitually, frequently, occasionally, or never. Hospital records and death certificates were checked for the next three years to establish how many of the men developed ischaemic heart disease or stroke: the numbers were 149 and 42, respectively. Three categories of snoring were used for analysis: habitual and frequent snorers (n = 1294), occasional snorers (n = 2614), and non-snorers (n = 480). The age adjusted relative risk of ischaemic heart disease between habitual plus frequent snorers and non-snorers was 1.91 (p less than 0.01) and for ischaemic heart disease or stroke, or both, 2.38 (p less than 0.001). There were no cases of stroke among the non-snorers. Adjustment for age, body mass index, history of hypertension, smoking, and alcohol use did not significantly decrease the relative risks, which were 1.71 (p greater than 0.05) for ischaemic heart disease and 2.08 (p less than 0.01) for ischaemic heart disease and stroke combined. At the beginning of follow up in 1981, 462 men reported a history of angina pectoris or myocardial infarction. For them the relative risk of ischaemic heart disease between habitual plus frequent snorers and non-snorers was 1.30 (NS); for men without previous ischaemic heart disease 2.72 (p less than 0.05). Snoring seems to be a potential determinant of risk of ischaemic heart disease and stroke.
PMCID: PMC1245038  PMID: 3101779
8.  Prevalence of Sleep Abnormalities and Their Association with Metabolic Syndrome among Asian Indians: Chennai Urban Rural Epidemiology Study (CURES – 67) 
Objective
To estimate the prevalence of sleep abnormalities and their association with glucose intolerance and metabolic syndrome (MS) in the normal-weight urban South Indian population.
Methods
This population-based, cross-sectional study was carried out in 358 subjects aged 20–76 years randomly selected from the Chennai Urban Rural Epidemiology Study in South India. A validated questionnaire assessing various sleep abnormalities (snoring, daytime sleepiness, lack of refreshing sleep, and number of hours of sleep) was administered. All subjects underwent an oral glucose tolerance test, and anthropometric biochemical measurements were obtained to assess cardiometabolic risk factors including glucose intolerance. Diabetes risk was assessed using a previously validated Indian Diabetes Risk Score (IDRS).
Results
The overall prevalence of snoring and daytime sleepiness was 40% and 59%, respectively. Snorers were more male, older, smokers, and had higher levels of cardiometabolic risk factors. Subjects with daytime sleepiness had higher body mass index (BMI) and abdominal obesity. Both snoring (50.9% vs 30.2%, p < 0.001) and daytime sleepiness (68% vs 49.7%, p < 0.001) were more prevalent among subjects with impaired glucose metabolism compared to those with normal glucose metabolism. Both sleep measures were associated with higher diabetes risk scores, as assessed by the IDRS (snoring: trend χ2, 11.14, p = 0.001; daytime sleepiness: trend χ2, 5.12, p = 0.024). Metabolic syndrome was significantly associated with snoring even after adjusting for age, sex, family history of diabetes, physical activity, smoking, and alcohol.
Conclusion
The prevalence of snoring and daytime sleepiness is high among urban South Indians and these two sleep measures are associated with glucose intolerance, MS, and higher diabetes risk scores.
PMCID: PMC3005066  PMID: 21129351
sleep abnormalities; snoring; daytime sleepiness; cardiometabolic risk factors; metabolic syndrome; Asian Indians
9.  Unique Features of Obstructive Sleep Apnea in World Trade Center Responders With Aerodigestive Disorders 
Objectives
To compare obstructive sleep apnea (OSA) in World Trade Center (WTC) responders with aerodigestive disorders and snoring with non-WTC habitual snorers, and to distinguish features of OSA in a subset of responders with worsening of snoring after 9/11 from responders with previous habitual snoring.
Methods
Cross-sectional comparative study of 50 WTC Medical Monitoring and Treatment Program responders with aerodigestive disorders and snoring and 50 nonresponders with snoring. Responders with worsening of snoring after 9/11 were compared with previous habitual snorers.
Results
While there was a strong correlation between body mass index (BMI), weight, and Apnea + Hypopnea Index (r = 0.36, P = 0.001; r = 0.29, P = 0.044) in the nonresponders, no correlation between either BMI or weight and Apnea + Hypopnea Index was found in the responders. Responders with worsening of snoring after 9/11 had a significantly lower BMI than previous habitual snorers.
Conclusion
Mechanisms other than obesity are important in the pathogenesis of OSA in WTC responders with aerodigestive disorders.
doi:10.1097/JOM.0b013e3182305282
PMCID: PMC4049316  PMID: 21866046
10.  Capability of a neck worn device to measure sleep/wake, airway position, and differentiate benign snoring from obstructive sleep apnea 
To evaluate the accuracy of a neck-worn device in measuring sleep/wake, detecting supine airway position, and using loud snoring to screen for obstructive sleep apnea. Study A included 20 subjects who wore the neck-device during polysomnography (PSG), with 31 records obtained from diagnostic and split-night studies. Study B included 24 community-based snorers studied in-home for up to three-nights with obstructive sleep apnea (OSA) severity measured with a validated Level III recorder. The accuracy of neck actigraphy-based sleep/wake was measured by assessing sleep efficiency (SE). Differences in sleep position measured at the chest and neck during PSG were compared to video-editing. Loud snoring acquired with an acoustic microphone was compared to the apnea-hypopnea index (AHI) by- and acrosspositions. Over-reported SE by neck actigraphy was inversely related to OSA severity. Measurement of neck and chest supine position were highly correlated with video-edits (r = 0.93, 0.78). Chest was bias toward over-estimating supine time while the majority of neck-device supine position errors occurred during CPAP titrations. Snoring was highly correlated with the overall, supine, and non-supine PSG-AHI (r = 0.79, 0.74, 0.83) and was both sensitive and specific in detecting overall, supine, and non-supine PSGAHI >10 (sensitivity = 81, 88, 82 %; specificity = 87, 79, 100 %). At home sleep testing-AHI > 10, the sensitivity and specificity of loud snoring was superior when users were predominantly non-supine as compared to baseline (sensitivity = 100, 92 %; specificity = 88, 77 %). Neck actigraphy appears capable of estimating sleep/wake. The accuracy of supine airway detection with the neck-device warrants further investigation. Measurement of loud snoring appears to provide a screening tool for differentiating positional apneic and benign snorers.
doi:10.1007/s10877-014-9569-3
PMCID: PMC4309901  PMID: 24599632
OSA; Positional; Snoring; Screening; Actigraphy; Validation
11.  Does the Oropharyngeal Fat Tissue Influence the Oropharyngeal Airway in Snorers? Dynamic CT Study 
Korean Journal of Radiology  2004;5(2):102-106.
Objective
The aim of this study was to determine if snorers have a narrower oropharyngeal airway area because of fat infiltration, and an elevated body mass index.
Materials and Methods
Ten control subjects and 19 patients that snored were evaluated. We obtained 2-mm-thick axial CT scan images every 0.6 seconds during expiration and inspiration at the same level of the oropharynx. We selected the largest and the smallest oropharyngeal airway areas and found the differences. From the slice that had the smallest oropharyngeal airway area, the thickness of the parapharyngeal and subcutaneous fat was measured. The measurements from the left and right side were added together and single values for parapharyngeal and subcutaneous fat tissue thickness were then found.
Results
The conventional measure of body mass index was significantly higher in the snorers (p < 0.05). The difference in the smallest oropharyngeal airway area between snorers and the controls was statistically significant (p < 0.01). The average difference between the largest and the smallest oropharyngeal area in the control group and the snorer group was statistically significant (p < 0.05). There was no significant difference in the largest oropharyngeal airway area, the total subcutaneous fat width and the total parapharyngeal fat width between snorers and control subjects (p > 0.05).
Conclusion
We concluded that the oropharyngeal fat deposition in snorers is not an important factor, and it does not predispose a person to the upper airway narrowing.
doi:10.3348/kjr.2004.5.2.102
PMCID: PMC2698137  PMID: 15235234
Computed tomography (CT); Computed tomography (CT), functional imaging; Neek, CT; Neck, anatomy
12.  Effect of body position on tongue posture in awake patients with obstructive sleep apnoea 
Thorax  1997;52(3):255-259.
BACKGROUND: Snoring and obstructive sleep apnoea (OSA) are worse or may only occur in the supine position. The effect of body position on upper airway size has been reported, but the effect on tongue posture has not previously been examined. METHODS: Detailed measurements were made of tongue posture from upright and supine lateral cephalograms on 24 men with OSA and 13 men with non-apnoeic snoring matched for age, body mass index, and craniofacial skeletal pattern. Patients with OSA had apnoea/hypopnoea indices (AHI) of > 50/hour and/or apnoea indices (AI) of > 25/hour while non-apnoeic snorers had AHI of < 10/hour and AI of < 5/hour. RESULTS: In non-apnoeic snorers the tongue depth measurements for the superior-posterior portion of the tongue were larger in the supine than in the upright position (p < 0.05). There was no significant difference in tongue depth measurements between the upright and the supine position in the patients with OSA. CONCLUSIONS: When awake patients with OSA move from the upright to the supine position they maintain their upright tongue posture which may tend to protect against upper airway collapse secondary to the increased gravitational load on the tongue. In contrast, when awake non-apnoeic snorers move from the upright to the supine position a significant dorsal movement in the superior-posterior portion of the tongue is observed. 



PMCID: PMC1758500  PMID: 9093342
13.  Persistent Snoring in Preschool Children: Predictors and Behavioral and Developmental Correlates 
Pediatrics  2012;130(3):382-389.
OBJECTIVE:
To clarify whether persistent snoring in 2- to 3-year-olds is associated with behavioral and cognitive development, and to identify predictors of transient and persistent snoring.
METHODS:
Two hundred forty-nine mother/child pairs participated in a prospective birth cohort study. Based upon parental report of loud snoring ≥2 times weekly at 2 and 3 years of age, children were designated as nonsnorers, transient snorers (snored at 2 or 3 years of age, but not both), or persistent snorers (snored at both ages). We compared groups by using validated measures of behavioral and cognitive functioning. Potential predictors of snoring included child race and gender, socioeconomic status (parent education and income), birth weight, prenatal tobacco exposure (maternal serum cotinine), childhood tobacco exposure (serum cotinine), history and duration of breast milk feeding, and body mass relative to norms.
RESULTS:
In multivariable analyses, persistent snorers had significantly higher reported overall behavior problems, particularly hyperactivity, depression, and inattention. Nonsnorers had significantly stronger cognitive development than transient and persistent snorers in unadjusted analyses, but not after demographic adjustment. The strongest predictors of the presence and persistence of snoring were lower socioeconomic status and the absence or shorter duration of breast milk feeding. Secondary analyses suggested that race may modify the association of childhood tobacco smoke exposure and snoring.
CONCLUSIONS:
Persistent, loud snoring was associated with higher rates of problem behaviors. These results support routine screening and tracking of snoring, especially in children from low socioeconomic backgrounds; referral for follow-up care of persistent snoring in young children; and encouragement and facilitation of infant breastfeeding.
doi:10.1542/peds.2012-0045
PMCID: PMC3428758  PMID: 22891224
sleep-disordered breathing; behavior problems; preschool; environmental tobacco smoke; breastfeeding; overweight
14.  Correlation of obstructive sleep apnea hypopnea syndrome with metabolic syndrome in snorers 
Journal of Biomedical Research  2014;28(3):222-227.
Abstract
Though obstructive sleep apnea hypopnea syndrome (OSAHS) and metabolic syndrome (MS) are correlated; the contributing factors for the occurrence of MS in Chinese snorers remain largely undefined. We aimed to investigate the associated pathogenesis of coexistence of OSAHS and MS in Chinese snorers. A total of 144 Chinese habitual snorers were divided into 3 groups, the control group (simple snorers) (n  =  36), the mild OSAHS group (n  =  52) and the moderate-to-severe OSAHS group (n  =  56). The incidence of MS in the moderate-to-severe OSAHS group (26.8%) was significantly higher than that in the control group (8.3%), the mild OSAHS group (11.1%) and all the OSAHS patients (19.45%) (all P < 0.05). Homeostatic model assessment (HOMA) index and proinsulin (PI) were negatively correlated with nocturnal meanSpO2 and miniSpO2. Meanwhile, nocturnal SpO2 were negatively correlated with body mass index, waist and neck circumferences and diastolic blood pressure, but positively correlated with total cholesterol and high-density lipoprotein cholesterol. The study indicated that in Chinese snorers, moderate-to-severe OSAHS was closely associated with MS via nocturnal hypoxemia.
doi:10.7555/JBR.28.20120120
PMCID: PMC4085559  PMID: 25013405
hypoxia; insulin resistance; metabolic syndrome; obstructive sleep apnea hypopnea syndrome
15.  Predictors and prevalence of obstructive sleep apnoea and snoring in 1001 middle aged men. 
Thorax  1991;46(2):85-90.
One thousand and one men, aged 35-65 years, were identified from the age-sex register of one group general practice. Over four years 900 men were visited at home and asked questions about symptoms potentially related to sleep apnoea and snoring. Height, weight, neck circumference, resting arterial oxygen saturation (SaO2), and spirometric values were also determined. All night oximetry was then performed at home and the tracing analysed for the number of dips in SaO2 of more than 4%. Subjects with more than five dips of 4% SaO2 or more per hour were invited for sleep laboratory polysomnography. Seventeen per cent of the men admitted to snoring "often." Multiple linear regression techniques identified and ranked neck circumference (r2 = 7.2%), cigarette consumption (r2 = 3.4%), and nasal stuffiness (r2 = 2%) as the only significant independent predictors of snoring. Together these account for at least a sixfold variation in the likelihood of being an "often" snorer. Forty six subjects (5%) had greater than 4% SaO2 dip rates of over five an hour and 31 of these had full sleep studies. Three subjects had clinically obvious and severe symptomatic obstructive sleep apnoea, giving a prevalence of three per 1001 men (0.3%; 95% confidence interval 0.07-0.9%). Eighteen men had obstructive sleep apnoea only when supine and in 10 the cause of the SaO2 dipping on the original home tracing was not elucidated. The greater than 4% SaO2 dip rates correlated with the history of snoring. Multiple linear regression techniques identified and ranked neck circumference (r2 = 7.9%), alcohol consumption (r2 = 3.7%), age (r2 = 1%) and obesity (r2 = 1%) as the only significant independent predictors of the rate of overnight hypoxic dipping. This study shows that snoring in this randomly selected population correlates best with neck size, smoking, and nasal stuffiness. Obstructive sleep apnoea, defined by nocturnal hypoxaemia, correlates best with neck size and alcohol, and less so with age and general obesity.
PMCID: PMC462949  PMID: 2014507
16.  COMPARISON OF CBCT PARAMETERS AND SLEEP QUESTIONNAIRES IN SLEEP APNEA PATIENTS AND CONTROLS 
Objective
To compare the Cone-Beam Computerized Tomography (CBCT) scan measurements between patients with Obstructive Sleep Apnea (OSA) and snorers to develop a prediction model for OSA based on CBCT imaging and the Berlin Questionnaire.
Materials and methods
80 subjects (46 OSA patients with Apnea-Hypoapnea Index [AHI]≥ 10 and 34 snorers AHI<10 based on ambulatory somnographic assessment) were recruited through flyers and mail at USC School of Dentistry and at a private practice. Each patient answered the Berlin Questionnaire, and was imaged with CBCT in supine position. Linear and volumetric measurements of the upper airway were performed by one blinded operator and multivariate logistic regression analysis was used to identify risk factors for OSA.
Results
OSA patients were predominantly male, older, had a larger neck size and larger Body Mass index than the snorers. The minimum cross-sectional area of the upper airway and its lateral dimension were significantly smaller in the cases. Airway uniformity defined as the minimum cross-sectional area divided by the average area was significantly smaller in the OSA patients.
Conclusions
Age>57 years, male gender, a “high risk” Berlin Questionnaire and narrow upper airway lateral dimension (<17mm) were identified as significant risk factors for OSA. The results of this study indicate that 3-dimensional CBCT airway analysis could be used as a tool to assess the presence and severity of OSA. The presence and severity (as measured by the RDI) of OSA is associated with a narrow lateral dimension of the airway, increasing age, male gender, and the Berlin questionnaire.
doi:10.1016/j.tripleo.2009.09.033
PMCID: PMC2900776  PMID: 20123412
Cone-Beam Computerized Tomography; Obstructive sleep apnea; Upper airway; Volume
17.  Association between primary nocturnal enuresis and habitual snoring in children with obstructive sleep apnoea-hypopnoea syndrome 
Introduction
Nocturnal enuresis (NE) and obstructive sleep apnoea-hypopnoea syndrome (OSAHS) are common problems during childhood, and population studies have reported a significant correlation between them. This study aimed to assess whether habitual snoring, mouth breathing and daytime sleepiness are associated with increased incidence of NE in children with OSAHS.
Material and methods
Polysomnography was performed in 42 children (66.7% males), 3.5-14.5 years old, who were evaluated for sleep-disordered breathing (SDB).
Results
Fourteen out of 42 children (33.3%) presented mild, 16 out of 42 (38.1%) moderate and 12 out of 42 (28.6%) severe degree of OSAHS. Apnea hypopnea index (AHI) ranged between 1.30-94.20 (10.54 ±15.67) events per hour of sleep. Nocturnal enuresis was reported in 7/42 (16.7%) of them. The main observed symptoms were snoring (90.5%), restless sleep (81%), mouth breathing (71.4%), nasal congestion (76.2%), and difficulty in arousal (52.4%). A statistically significant association was found between NE and mouth breathing (p = 0.014) or nasal congestion (p = 0.005). Children with OSAHS and NE had a higher arousal index (8.14 ±8.05) compared with OSAHS children without NE (4.61 ±7.95) (p = 0.19, z = –1.28). Snorers had higher levels of AHI (11.02 ±16.37) compared with non-snorers (6.05 ±4.81) (p = 0.33, z = –0.96), and habitually snorers (23/42, 54.76%) were at greater risk of having NE (4/23) than were non-snorers (0/4, p = 0.36). However, the prevalence of enuresis was not related to the severity of OSAHS, expressed as AHI (p = 0.70).
Conclusions
Mouth breathing, nasal congestion and high threshold of arousal during sleep should be more carefully evaluated in cases of children with NE who do not respond to standard treatment and present SDB.
doi:10.5114/aoms.2012.28809
PMCID: PMC3400898  PMID: 22852010
nocturnal enuresis; sleep apnoea syndrome
18.  The Associations between Anthropometric Indices and Obstructive Sleep Apnea in a Korean Population 
PLoS ONE  2014;9(12):e114463.
Background
Obesity is a major risk factor for the development of obstructive sleep apnea (OSA). Although clinical and epidemiological studies have shown that OSA and obesity are strongly associated, few Asian studies have examined the associations between anthropometric obesity indices and OSA, especially in the Korean population. The purpose of this study was to evaluate the influence of anthropometric obesity indices on OSA in a Korean population.
Methods
Anthropometric indices, including neck circumference, waist circumference, and body mass index, were assessed in 383 consecutive subjects with suspected OSA.
Results
Of the 383 subjects assessed, 316 (82.5%) were diagnosed with OSA. Neck circumference (r = 0.518), waist circumference (r = 0.570), and body mass index (r = 0.512) were correlated with the apnea-hypopnea index (p<0.001, for all). After adjusting for age, sex, alcohol consumption, and smoking, a logistic regression model showed that neck circumference [odds ratio (OR), 1.414; p<0.001)], waist circumference (OR, 1.114; p<0.001), and body mass index (OR, 1.364; p<0.001) were associated with OSA. The linear regression model showed that neck circumference (β = 3.748, p<0.001), waist circumference (β = 1.272, p<0.001), and body mass index (β = 3.082, p<0.001) were associated with apnea-hypopnea index. The cut-off values for predicting OSA were determined as 34.5 cm for neck circumference, 76.5 cm for waist circumference, and 23.05 kg/m2 for body mass index for females, and 38.75 cm for neck circumference, 88.5 cm for waist circumference, and 24.95 kg/m2 for body mass index for males.
Conclusion
Increased anthropometric indices were significantly associated with the presence and severity of OSA in a Korean population. In addition, this study demonstrated the cut-off values for body mass index, waist circumference, and neck circumference for increased OSA risk.
doi:10.1371/journal.pone.0114463
PMCID: PMC4256422  PMID: 25474257
19.  Impact of Obstructive Sleep Apnea and Snoring on Left Ventricular Mass and Diastolic Function in Hypertensive Nigerians 
Background:
Systemic hypertension (HTN) and obstructive sleep apnea (OSA) are individually associated with left ventricular structural and functional adaptations. However, little is known about the impact of OSA on the left ventricle in Africans with HTN.
Aim:
The aim of this study is to determine the association between OSA and left ventricular mass (LVM) and diastolic dysfunction in Nigerian hypertensive subjects.
Subjects and Methods:
A total of 104 hypertensive subjects were enrolled for this study. Risk for OSA was assessed with the Berlin score. Clinical history and examination were performed. Echocardiography was performed and diastolic dysfunction was diagnosed using the pulse wave Doppler. Statistical analysis was performed using the statistical package for social sciences 17.0. (Chicago Ill, USA). Comparism between groups was done using t-test and Chi-square and P < 0.050 was taken as statistically significant.
Results:
LVM, posterior wall and interventricular septum were significantly higher among hypertensive patients with high risk for OSA than those with low risk (263.610 g [11.202] g vs. 208.714 g [47.060] g; 12.100 mm [2.712] mm vs. 10.711 mm [2.101] mm; 13.210 [3.114] mm vs. 11.700 mm [2.402] mm respectively). A similar finding was reported between hypertensive snorers and hypertensive non-snorers. Fasting blood glucose was also significantly higher among hypertensive snorers than non-snorers. However, mean transmitral early (E) to late (A) flow E/A ratio was lower among hypertensive with low risk of OSA and snorers than those with a high risk and non-snorers respectively. Left Ventricular hypertrophy was also more common among hypertensive with high risk of OSA than non-snorers and low risk of OSA (39/55, 70.9% vs. 28/49, 57.1% respectively, P < 0.05).
Conclusion:
OSA is associated with significant additional left ventricular changes in hypertensive subjects. Therefore, aggressive effort at managing OSA and snoring among hypertensive subjects may further reduce their cardiovascular risk.
doi:10.4103/2141-9248.133458
PMCID: PMC4071732  PMID: 24971207
Africa; Hypertension; Sleep apnea; Snoring
20.  Heart rate variability in non-apneic snorers and controls before and after continuous positive airway pressure 
Background
We hypothesized that sympathetic nervous system activity (SNSA) is increased and parasympathetic nervous system activity (PNSA) is decreased during non-rapid eye movement (NREM) sleep in non-apneic, otherwise healthy, snoring individuals compared to control. Moreover, we hypothesized that these alterations in snoring individuals would be more evident during non-snoring than snoring when compared to control.
Methods
To test these hypotheses, heart rate variability was used to measure PNSA and SNSA in 11 normotensive non-apneic snorers and 12 control subjects before and 7-days after adapting to nasal continuous positive airway pressure (nCPAP).
Results
Our results showed that SNSA was increased and PNSA was decreased in non-apneic snorers during NREM compared to control. However, these changes were only evident during the study in which snoring was eliminated with nCPAP. Conversely, during periods of snoring SNSA and PNSA were similar to measures obtained from the control group. Additionally, within the control group, SNSA and PNSA did not vary before and after nCPAP application.
Conclusion
Our findings suggest that long-lasting alterations in autonomic function may exist in snoring subjects that are otherwise healthy. Moreover, we speculate that because of competing inputs (i.e. inhibitory versus excitatory inputs) to the autonomic nervous system during snoring, the full impact of snoring on autonomic function is most evident during non-snoring periods.
doi:10.1186/1471-2466-5-9
PMCID: PMC1208915  PMID: 16048652
21.  Association between self reported snoring, STOP questionnaire and postoperative pulmonary complications in patients submitted to ortophaedic surgery 
Background
Obstructive sleep apnea (OSA) may increase perioperative complications. The aim of this study was to determine the relationship among postoperative pulmonary complication, snoring and STOP questionnaire in patients with ortophaedic surgery.
Methods
1,406 consecutive records of patients who had undergone elective ortophaedic surgery during the period January 2005-December 2008 were investigated retrospectively. Demographic information, sleep symptoms, STOP questionnaire, comorbidities and outcome data were collected.
Results
There were 289 (20.5%) snorers and 1,117 (79.5%) non-snorers in the study group. There was no significant difference between snorer and non-snorer patients (p > 0.05) in the prevalence of pneumonia and respiratory failure. But in snorer patients the rate of postoperative atelectasis was significantly higher than in non-snorer group (p < 0.0001). The STOP Questionnaire was given to 1,406 patients and 147 (10.4%) out of them were classified at high risk of OSA. There was no significant difference in the prevalence of pneumonia and respiratory failure between low and high risk group (p > 0.05). However, in high risk patients the occurrence of postoperative atelectasis was significantly higher than in low risk group (p < 0.0001).
Conclusion
Postoperative atelectasis was significantly more prevalent in the high risk group according to STOP questionnaire.
doi:10.1186/2049-6958-8-3
PMCID: PMC3598696  PMID: 23331468
Atelectasis; Obesity; Orthopedic surgery; Sleep apnea; STOP questionnaire
22.  Snoring as a risk factor for disease: an epidemiological survey. 
In a study conducted in four family practice units in Toronto, Canada, 2001 subjects reported on snoring and medical conditions in members of their households. For spouses the prevalence of snoring increased with age up to the seventh decade, with a higher prevalence of nearly 85% in husbands. For 11 medical problems an association existed between snoring, its frequency, and the presence of the condition. This association continued when the data were corrected for sex, age, and marital state. For hypertension both men and women who snored between the fifth and 10th decades had a twofold increase over non-snorers. The prevalence of heart disease and other conditions, except for diabetes and asthma, also increased in snorers in this age group. When corrected for smoking and obesity the association between snoring, hypertension, and heart disease persisted. These findings extend those of Lugaresi et al, and if they could be confirmed snoring as a risk factor for conditions other than sleep apnoea and sleep disorders might be considered. Methods of alleviating the acoustic annoyance of snoring may also provide direct medical benefits.
PMCID: PMC1417471  PMID: 3928056
23.  Habitual snoring with and without obstructive sleep apnoea: the importance of cephalometric variables. 
Thorax  1992;47(3):157-161.
BACKGROUND: The obstructive sleep apnoea syndrome is characterised by an increased apnoea-hypopnoea index and a reduction in the minimal arterial oxygen saturation (SaO2) values during sleep. The extent to which these variables can be predicted by cephalometric and otorhinolaryngological variables was tested. METHODS: One hundred consecutive habitual snorers (84% male), with a mean (SD) age of 50.1 (10.1) years, were studied. The 45 patients with less severe sleep apnoea, with an apnoea-hypopnoea index of 10 or less (group A), were compared with the 55 with an index above 10 (group B). RESULTS: Body mass index, some cephalometric variables, and some otorhinolaryngological variables differed significantly between group A and group B, in particular the soft tissue measures PNS-P (posterior nasal spine to palate), MP-H (mandibular plane to hyoid bone), degree of oropharynx stenosis, and tongue size. In a multiple regression correlation analysis MP-H, SNB (angle from sella to nasion to subspinale point), SNA (angle from sella to nasion to supramentale point), PAS (posterior airway space), tongue size, and body mass index contributed significantly to the equation explaining the severity of sleep apnoea. Nevertheless, these variables together explained only 33% of the variance of the apnoea-hypopnoea index in the total sample; they were more important for patients with moderate to severe stages of the disease. CONCLUSION: The lack of association between cephalometric variables and mild sleep apnoea suggests that the differences in these variables (soft tissue measures) may be the consequence rather than the cause of habitual snoring and the obstructive sleep apnoea syndrome.
PMCID: PMC1021003  PMID: 1519191
24.  Screening of Patients with Snoring and Obstructive Sleep Apnoea using Heart Rate Variability Indices 
Objective:
Snoring and obstructive sleep apnea (OSA) are common disorders. Snoring associated with excessive daytime sleepiness is the most prevalent symptoms of OSA. Heart rate variability (HRV) is altered in patients with OSA and the degree of alteration may be linked to the severity of OSA. Alterations in HRV in 24 hour tachograms have recently been used in screening OSA patients. Autonomic components causing HRV can be reliably studied using spectral analysis techniques involving fast Fourier transformation (FFT).
Methods:
Twenty-three subjects, 13 with severe OSA and 10 controls matched for age and body mass index, were selected from patients who had undergone polysomnography (PSG) for snoring at Sultan Qaboos University Hospital, Oman. A 24- hour electrocardiogram (ECG) Holter recording was done at home, starting at 10am. Spectral analysis of ECG from sleep Holter and PSG recordings was analysed using fast Fourier transformation (FFT).
Results:
The ECG RR intervals of snorers with OSA were significantly shorter than in snorers without OSA (p<0.01). The low frequency (LF) spectral densities of HRV from polysomnography and Holter were significantly higher in OSA patients than in snorers, (p< 0.0001). The power spectral density of the high frequency bands was similar in the two groups. The overnight ECG Holter accurately identified all 13 snorers with severe OSA.
Conclusion:
The spectral power of the LF band obtained using FFT of sleep HRV from Holter tachograms may be a useful and cost effective test in identifying snorers with severe OSA.
PMCID: PMC3087734  PMID: 21654953
Obstructive Sleep Apnea; Heart Rate Variability
25.  Mechanisms used to restore ventilation after partial upper airway collapse during sleep in humans 
Thorax  2007;62(10):861-867.
Background
Most patients with obstructive sleep apnoea (OSA) can restore airflow after an obstructive respiratory event without arousal at least some of the time. The mechanisms that enable this ventilatory recovery are unclear but probably include increased upper airway dilator muscle activity and/or changes in respiratory timing. The aims of this study were to compare the ability to recover ventilation and the mechanisms of compensation following a sudden reduction of continuous positive airway pressure (CPAP) in subjects with and without OSA.
Methods
Ten obese patients with OSA (mean (SD) apnoea‐hypopnoea index 62.6 (12.4) events/h) and 15 healthy non‐obese non‐snorers were instrumented with intramuscular genioglossus electrodes and a mask/pneumotachograph which was connected to a modified CPAP device that could deliver either continuous positive or negative pressure. During stable non‐rapid eye movement sleep the CPAP was repeatedly reduced 2–10 cm H2O below the level required to eliminate flow limitation and was held at this level for 5 min or until arousal from sleep occurred.
Results
During reduced CPAP the increases in genioglossus activity (311.5 (49.4)% of baseline in subjects with OSA and 315.4 (76.2)% of baseline in non‐snorers, p = 0.9) and duty cycle (123.8 (3.9)% of baseline in subjects with OSA and 118.2 (2.8)% of baseline in non‐snorers, p = 0.4) were similar in both groups, yet patients with OSA could restore ventilation without cortical arousal less often than non‐snorers (54.1% vs 65.7% of pressure drops, p = 0.04). When ventilatory recovery did not occur, genioglossus muscle and respiratory timing changes still occurred but these did not yield adequate pharyngeal patency/ventilation.
Conclusions
Compensatory mechanisms (increased genioglossus muscle activity and/or duty cycle) often restore ventilation during sleep but may be less effective in obese patients with OSA than in non‐snorers.
doi:10.1136/thx.2006.070300
PMCID: PMC2094262  PMID: 17412778

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