A stepped approach for prediction of obstructive sleep apnea in overtly asymptomatic obese subjects: a hospital based study

Fibroblast growth factor 21 is an independent predictor of prevalent and incident obstructive sleep apnea

Fibroblast growth factor 21 (FGF21) is a metabolic regulator and a potential biomarker of metabolic diseases. Limited data are available on the association between FGF21 and obstructive sleep apnea (OSA), which is considered as a manifestation of metabolic syndrome. In the present cross-sectional and longitudinal analyses, the FGF21 level was associated with OSA. This analysis of two clinical cohorts is the first to show that the FGF21 level increased significantly with OSA severity and was an independent predictor of incident OSA in Chinese adults. The circulating FGF21 level could serve as a potential serum biomarker of OSA and its comorbidities and thus aid risk evaluation and early intervention.

Alzheimer's Disease, Sleep Disordered Breathing, and Microglia: Puzzling out a Common Link

Sleep Disordered Breathing (SDB) and Alzheimer's Disease (AD) are strongly associated clinically, but it is unknown if they are mechanistically associated. Here, we review data covering both the cellular and molecular responses in SDB and AD with an emphasis on the overlapping neuroimmune responses in both diseases. We extensively discuss the use of animal models of both diseases and their relative utilities in modeling human disease. Data presented here from mice exposed to intermittent hypoxia indicate that microglia become more activated following exposure to hypoxia. This also supports the idea that intermittent hypoxia can activate the neuroimmune system in a manner like that seen in AD. Finally, we highlight similarities in the cellular and neuroimmune responses between SDB and AD and propose that these similarities may lead to a pathological synergy between SDB and AD.

Obstructive Sleep Apnea in Patients with Chronic Obstructive Pulmonary Disease: Facts and Perspectives

The co-occurrence of obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) in the same patient, named the overlap syndrome (OS), was first described in 1985. Although the American Thoracic Society underlined the limited knowledge of OS, stated research priorities for this condition, and recommended a "screening" strategy to identify OSA in COPD patients with chronic stable hypercapnia, research studies on OS remain scarce. This review aims to summarize the current knowledge and perspectives related to OSA in COPD patients. OS prevalence is 1.0-3.6% in the general population, 3-66% in COPD patients, and 7-55% in OSA patients. OS patients may have worse sleep quality than those with OSA or COPD alone. Scoring hypopneas may be difficult in COPD patients; desaturation episodes may have origins in these patients, namely upper airway obstruction, hypoventilation during paradoxical sleep, ventilation/perfusion mismatches, and obesity. The apnea-hypopnea index is similar in OSA and OS patients. Desaturations may be greater and more prolonged in OS patients than in patients with COPD or OSA alone. Low body mass index, hyperinflation, and less collapsible airways reduce the risk of OSA in COPD patients. OSA is a risk factor for pulmonary hypertension in COPD patients. Whether OS increases mortality and morbidity risks compared to COPD or OSA alone remains to be confirmed. No guidelines currently recommend specific approaches to the treatment of OSA in patients with COPD.

Does neck circumference predict obstructive sleep apnea in children with obesity?

OBJECTIVES

Obstructive sleep apnea (OSA) affects 10-50% of children with obesity, but its identification is challenging and wait times for testing are long. Previous studies suggest that neck circumference (NC) and neck-to-height ratio (NHR) may predict OSA. Our objectives were to 1) evaluate associations of NC and NHR with OSA; 2) model NHR as a predictor of OSA, adjusting for age, sex, and Tanner stage; and 3) identify thresholds of NHR associated with OSA, in children with obesity.

METHODS

Participants were aged 8-17 years, with obesity (BMI >95%ile), undergoing polysomnography. Associations between NC and NHR with OSA were evaluated. NHR, age, sex and self-reported Tanner stage (early/late) were included in a negative binomial multiple regression model to predict obstructive apnea hypopnea index (OAHI).

RESULTS

71 children participated, with median age 14.8 years (IQR 12.6, 16.0), 54% male, median BMI z-score 2.5 (IQR 2.3, 2.7), and 77% late Tanner stage. OSA was severe in 18 children (25.4%), moderate in 12 (16.9%), and mild in 18 (25.4%). In the model, each 0.01 increase in NHR was associated with a 55% increase in OAHI (95% CI: 36%, 80%); boys had a 119% higher OAHI than girls (95% CI: 10%, 337%). Threshold NHR associated with moderate-severe OSA was 0.25 in females and 0.23 in males.

CONCLUSIONS

NHR and male sex independently predict OSA severity in children with obesity, adjusting for age and Tanner stage. Children with obesity and NHR above identified thresholds are more likely to have moderate-severe OSA, and may benefit from earlier polysomnography.

Screening of Obstructive Sleep Apnea Syndrome by Electronic-Nose Analysis of Volatile Organic Compounds

Obstructive Sleep Apnea Syndrome (OSAS) carries important social and economic implications. Once the suspicion of OSAS has arisen, Polysomnography (PSG) represents the diagnostic gold standard. However, about 45% of people who have undergone PSG are free from OSAS. Thus, efforts should be made to improve the selection of subjects. We verified whether the pattern of Volatile Organic Compounds (VOCs) helps to select patients amenable to PSG. We studied 136 subjects (20 obese non-OSAS, 20 hypoxic OSAS, 20 non-hypoxic OSAS, and 20 non-hypoxic Chronic Obstructive Pulmonary Disease (COPD) vs 56 healthy controls) without any criteria of exclusion for comorbidity to deal with a real-life population. VOCs patterns were analyzed using electronic-nose (e-nose) technology. A Discriminant Analysis (Partial Least Square-Discriminant Analysis) was performed to predict respiratory functions and PSG parameters. E-nose distinguished controls (100% correct classification) from others and identified 60% of hypoxic, and 35% of non-hypoxic OSAS patients. Similarly, it identified 60% of COPD patients. One-by-one group comparison yielded optimal discrimination of OSAS vs controls and of COPD vs controls (100% correct classification). In conclusion, e-nose technology applied to breath-analysis can discriminate non-respiratory from respiratory diseased populations in real-life multimorbid populations and exclude OSAS. If confirmed, this evidence may become pivotal for screening purposes.

Differential Effects of Obesity on Obstructive Sleep Apnea Syndrome according to Age

OBJECTIVE

To evaluate the effect of obesity on obstructive sleep apnea syndrome (OSAS) by age in relation to anthropometric measurements.

METHODS

The medical records of 1,110 participants diagnosed with OSAS were analyzed according to age. All participants underwent nocturnal polysomnography and had their body mass index, waist circumference, neck circumference (NC), and waist-to-hip ratio measured.

RESULTS

According to the multiple linear regression analysis model for the natural logarithm of the apnea-hypopnea index treating all four anthropometric measurements and gender as covariates, the final stepwise model accounted for an increasing percentage of the variability in the severity of OSAS as a function of age: 7.0, 9.1, 14.5, and 25.6% for those aged <30, 30-39, 40-49, and 50-59 yrs, respectively. It accounted for a decreased percentage among those 60-69 (20.3%) and 70 yrs or older (3.9%). The correlation between NC and the severity of OSAS linearly increased as a function of age for those aged 30-59 yrs, peaked among those in their 60s, and dramatically decreased thereafter.

CONCLUSION

Middle-aged patients with OSAS were more likely to be obese, as measured by anthropometric measurements, than were younger or older OSAS patients. In particular, the predictive value of NC was significantly lower for younger and older OSAS patients.

Age, gender, neck circumference, and Epworth sleepiness scale do not predict obstructive sleep apnea (OSA) in moderate to severe chronic obstructive pulmonary disease (COPD): The challenge to predict OSA in advanced COPD

The combination of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) is associated with substantial morbidity and mortality. We hypothesized that predictors of OSA among patients with COPD may be distinct from OSA in the general population. Therefore, we investigated associations between traditional OSA risk factors (e.g. age), and sleep questionnaires [e.g. Epworth Sleepiness Scale] in 44 patients with advanced COPD. As a second aim we proposed a pilot, simplified screening test for OSA in patients with COPD. In a prospective, observational study of patients enrolled in the UCSD Pulmonary Rehabilitation Program we collected baseline characteristics, cardiovascular events (e.g. atrial fibrillation), and sleep questionnaires [e.g. Pittsburgh Sleep Quality Index (PSQI)]. For the pilot questionnaire, a BMI ≥25 kg/m2 and the presence of cardiovascular disease were used to construct the pilot screening test. Male: 59%; OSA 66%. FEV1 (mean ± SD) = 41.0±18.2% pred., FEV1/FVC = 41.5±12.7%]. Male gender, older age, and large neck circumference were not associated with OSA. Also, Epworth Sleepiness Scale and the STOP-Bang questionnaire were not associated with OSA in univariate logistic regression. In contrast, BMI ≥25 kg/m2 (OR = 3.94, p = 0.04) and diagnosis of cardiovascular disease (OR = 5.06, p = 0.03) were significantly associated with OSA [area under curve (AUC) = 0.74]. The pilot COPD-OSA test (OR = 5.28, p = 0.05) and STOP-Bang questionnaire (OR = 5.13, p = 0.03) were both associated with OSA in Receiver Operating Characteristics (ROC) analysis. The COPD-OSA test had the best AUC (0.74), sensitivity (92%), and specificity (83%). A ten-fold cross-validation validated our results. We found that traditional OSA predictors (e.g. gender, Epworth score) did not perform well in patients with more advanced COPD. Our pilot test may be an easy to implement instrument to screen for OSA. However, a larger validation study is necessary before further clinical implementation is warranted.

Anthropometric and Dental Measurements in Children with Obstructive Sleep Apnea

STUDY OBJECTIVES

A number of authors have shown that children with OSA are more likely to have certain physical characteristics than healthy controls. With this in mind, our objectives were to collect normative baseline data and determine if there was a significant difference in anthropometric and dental measurements between children with OSA and age-matched nonsnoring controls.

METHODS

Children 2 to 12 y of age, in whom OSA was diagnosed by overnight polysomnography, were recruited to our experimental group. Age-matched nonsnoring controls were screened for signs of sleep-disordered breathing. Anthropometric measurements, including waist, neck, and hip circumferences, and waist-hip and neck-waist ratios, were obtained on all study participants preoperatively. Dental casts were acquired to determine intertooth distances and palatal height.

RESULTS

Sixty-one children (42 with OSA [69%] and 19 controls [31%]) with a mean age of 4.7 y participated in the study. Waist and hip circumferences were significantly larger in children with OSA (p = 0.001 and 0.001, respectively). However, there was no difference in neck circumference and waist-hip ratios between the two groups. Neck-waist ratio in children with OSA was significantly smaller than in controls (p = 0.001). Intertooth distance for the first (p < 0.0001) and second deciduous (p = 0.0002) and first permanent molars (p = 0.022) were significantly narrowed in children with OSA; however, no difference was seen in palatal height between groups. Body mass index was similar between groups (p = 0.76).

CONCLUSIONS

Anthropometric and dental measurements were significantly different in children with OSA compared to nonsnorers. Future studies with a large sample size may allow us to determine if these measurements can be used by clinicians to identify children at risk for OSA.

COMMENTARY

A commentary on this article appears in this issue on page 1213.

Neck circumference percentile: A screening tool for pediatric obstructive sleep apnea

RATIONALE

Large neck circumference (NC) is associated with obstructive sleep apnea (OSA) in adults, especially males. Since NC changes with age and sex, a lack of reference ranges makes neck size difficult to assess as a screening tool in children.

METHODS

Using a population-based dataset of 1,913 children, we developed reference ranges for NC by age and sex for children aged 6-17 years. In this study, we collected NC data on 245 children aged 6-17 years presenting to the Children's Hospital of Eastern Ontario for polysomnography. The association between NC>the 95th percentile and OSA (total apnea-hypopnea-index>5 events/hr and/or obstructive-apnea-index ≥ 1 event/hr) was explored. Thresholds of BMI percentile and waist circumference were also examined.

RESULTS

Individuals with NC>95th percentile for age and sex had increased risk of OSA (relative risk 1.7 [95% CI 1.0-3.0], P=0.04), compared to those with NC ≤ 95th percentile. BMI ≥ 95th percentile gave similar results (relative risk 1.8 [95% CI 1.1-2.9], P=0.02). When examined by sex, the association was significant in males ≥ 12 years (relative risk 3.3 [95% CI 1.0-10.4], P=0.04), but not females (P=0.63). Neither BMI  ≥ 95th percentile nor waist circumference>95th percentile was significant.

CONCLUSIONS

Children and youth with NC>95th percentile for age and sex have significantly increased risk of OSA. This effect is significant in males ≥ 12 years, whereas BMI is not. NC percentile may be an additional screening tool for OSA in children and youth.

Does neck-to-waist ratio predict obstructive sleep apnea in children?

OBJECTIVES

Central adiposity and large neck circumference are associated with obstructive sleep apnea (OSA) in adults but have not been evaluated in children as predictors of OSA. Study objectives were to determine whether (1) anthropometric measures including neck-to-waist ratio are associated with OSA in older children; (2) body fat distribution, measured by neck-to-waist ratio, is predictive of OSA in overweight/obese children.

METHODS

Cross-sectional study involving children 7-18 years scheduled to undergo polysomnography at a tertiary care children's hospital. OSA was defined as total apnea-hypopnea index > 5 events/h and/or obstructive apnea index > 1 event/h. Recursive partitioning was used to select candidate predictors of OSA from: age, sex, height and weight percentile, body mass index (BMI) z-score, neck-to-waist ratio, tonsil size, and Mallampati score. These were then evaluated using log binomial models and receiver operator characteristic analysis.

RESULTS

Two hundred twenty-two participants were included; 133 (60%) were overweight/obese, 121 (55%) male,47 (21%) had OSA. Neck-to-waist ratio (relative risk [RR] 1.97 per 0.1 units, 95% CI 1.48 to 2.84) and BMI z-score (RR 1.63 per unit, 95% CI 1.30 to 2.05) were identified as independent predictors of OSA. Considering only overweight/obese children, neck-to-waist ratio (RR 2.16 per 0.1 units, 95% CI 1.79 to 2.59) and BMI z-score (RR 2.02 per unit, 95% CI 1.25 to 3.26) also independently predicted OSA. However, in children not overweight/obese, these variables were not predictive of OSA.

CONCLUSIONS

Neck-to-waist ratio, an index of body fat distribution, predicts OSA in older children and youth, especially in those who were overweight/obese.

Sleep apnea and fatty liver disease: The growing link and management issues

Obstructive sleep apnea (OSA) is associated with metabolic, cardiovascular and neuropsychological disorders, with substantial morbidity and economic costs. OSA has been estimated to affect 4%-11% of the population, depending on age. Obesity is a significant risk factor for OSA. Non alcoholic fatty liver disease (NAFLD) has emerged as an integral component of the metabolic syndrome, with insulin resistance as the central pathogenic feature. Estimates based on imaging and autopsy studies suggest that about 20%-30% of adults in the United States and other Western countries have NAFLD. Evidence now suggests that NAFLD is independently correlated to insulin resistance regardless of adiposity. Some authors have suggested that OSA may be another contributor to NAFLD development. In complex diseases, several or many different genes interact with environmental factors in determining disease presence or its phenotype. Individual genes only have a small effect on disease risk and can therefore be very difficult to identify. The genetic and hormonal determinants of OSA and NAFLD have received little attention. A wide variety of intermediate phenotypes and genes are involved in OSA and NAFLD which makes this syndrome genetically complex. Various adipokines, the most important of which are leptin, adiponectin, tumor necrosis factor-alpha, resistin and interleukin-6, have a key role in NAFLD and OSA. Some studies have suggested that oxidative stress may also contribute to the development of NAFLD and OSA. Lifestyle intervention, insulin sensitizer drugs and bariatric surgery aim to improve metabolic syndrome, OSA and NAFLD but need further investigation.

Airway management in obese patients

The well-known difficulties in airway management in obese patients are caused by obesity-related airways and respiratory changes. Anesthesiologists confront a number of troubles, including rapid oxygen desaturation, difficulty with laryngoscopy/intubation and mask ventilation, and increased susceptibility to the respiratory depressant effects of anesthetic drugs. Preoperative assessment of the airways in the obese should include examination of specific predictors of difficult mask ventilation other than those for difficult intubation. Difficulties in airway management are decreased after providing optimal preoxygenation and positioning ("ramped"). Other strategies may include availability of alternative airway management devices, including new video laryngoscopes that significantly improve the visualization of the larynx and thereby facilitate intubation. If awake intubation is mandatory, it may be performed with fibrobronchoscope after providing an adequate topical anesthesia and sedation with short-acting drugs, such as remifentanil. Succinylcholine for rapid sequence induction might be replaced by rocuronium where sugammadex is available for reversal. A complete reversal of neuromuscular block, measured by train-of-four monitoring, should be obtained before extubation, which requires a fully awake patient in the same position with airway equipment used for intubation.

Body mass index and obstructive sleep apnoea in the UK: a cross-sectional study of the over-50s

BACKGROUND

An increasing prevalence of obesity in the UK has also seen a rise in the diagnosis of co-morbidities. Obstructive sleep apnoea (OSA) has previously been associated with body mass index (BMI) but has not been fully explored in a UK population.

AIMS

To quantify the association between BMI and a recorded diagnosis of OSA in primary care for people aged 50 years or over in the UK.

METHODS

A descriptive analysis is given of men and women aged 50 or over in the UK from The Health Improvement Network (THIN) database with regard to diagnosis of OSA, snoring, and BMI. Logistic regression was performed for the likelihood of OSA depending on BMI classification recorded after adjusting for gender, age, region, and socioeconomic status (Townsend quintile). The analyses were repeated for snoring.

RESULTS

After adjusting for confounders, those with a BMI recorded of 40+ kg/m2 were 27.39 times (95% CI 24.64 to 30.46) more likely to have OSA (p<0.0001). There was a lower prevalence of OSA with increasing age and levels of deprivation.

CONCLUSIONS

Obesity and snoring were both strongly associated with a diagnosis of OSA. The decreasing prevalence of OSA with increasing age and levels of deprivation needs further study to ensure that these groups are not being systematically under-investigated.

Prevalence of metabolic syndrome in a north Indian hospital-based population with obstructive sleep apnoea

BACKGROUND & OBJECTIVES

Obstructive sleep apnoea (OSA) is known to be associated with cardiovascular risk factors and metabolic syndrome (MS). The burden of MS in patients with OSA in India is unknown. We investigated the prevalence of MS and its components in a cross-sectional study in patients with and without OSA in a hospital-based population of a tertiary health care centre in New Delhi, India.

METHODS

Consecutive patients undergoing overnight polysomnography in the Sleep Laboratory of the Department of Internal Medicine of All India Institute of Medical Sciences (AIIMS) hospital, New Delhi, were studied. Anthropometry and body composition analysis, blood pressure (BP), fasting blood glucose, insulin resistance by homeostasis model assessment (HOMA-IR) and fasting blood lipid profile were measured. MS was defined using the National Cholesterol Education Program Adult treatment panel III criteria, with Asian cut-off values for abdominal obesity.

RESULTS

Of the 272 subjects recruited, 187 (82%) had OSA [apnoea-hypopnoea index (AHI)>5 events/h] while 40 (18%) had a normal sleep study. Prevalence of MS in OSA patients was 79 per cent compared to 48 per cent in non-OSA individuals [OR 4.15, (2.05-8.56), P<0.001]. Prevalence of OSA in mild, moderate and severe OSA was 66, 72 and 86 per cent, respectively (P<0.001). Patients with OSA were more likely to have higher BP [OR: 1.06 (1.02-1.11)], fasting insulin [OR: 1.18 (1.05-1.32)], HOMA-IR [OR: 1.61 (1.11-2.33)] and waist circumference [OR: 1.20 (1.13-1.27)].

INTERPRETATION & CONCLUSIONS

Our findings suggest that OSA is associated with a 4-fold higher occurrence of MS than patients without OSA. The prevalence of MS increases with increasing severity of OSA, therefore, early detection will be beneficial.

Obesity, obstructive sleep apnoea and metabolic syndrome

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

Prediagnosis of obstructive sleep apnea via multiclass MTS

Obstructive sleep apnea (OSA) has become an important public health concern. Polysomnography (PSG) is traditionally considered an established and effective diagnostic tool providing information on the severity of OSA and the degree of sleep fragmentation. However, the numerous steps in the PSG test to diagnose OSA are costly and time consuming. This study aimed to apply the multiclass Mahalanobis-Taguchi system (MMTS) based on anthropometric information and questionnaire data to predict OSA. Implementation results showed that MMTS had an accuracy of 84.38% on the OSA prediction and achieved better performance compared to other approaches such as logistic regression, neural networks, support vector machine, C4.5 decision tree, and rough set. Therefore, MMTS can assist doctors in prediagnosis of OSA before running the PSG test, thereby enabling the more effective use of medical resources.

Subjective sleepiness and daytime functioning in bariatric patients with obstructive sleep apnea

PURPOSE

The purpose of this study was to evaluate associations between obstructive sleep apnea (OSA) severity and self-reported sleepiness and daytime functioning in patients considering bariatric surgery for treatment of obesity.

METHODS

Using a retrospective cohort design, we identified 342 patients who had sleep evaluations prior to bariatric surgery. Our final sample included 269 patients (78.6 % of the original cohort, 239 females; mean age = 42.0 ± 9.5 years; body mass index = 50.2 ± 7.7 kg/m(2)) who had overnight polysomnography and completed the Epworth Sleepiness Scale (ESS) and the Functional Outcomes of Sleep Questionnaire (FOSQ). Patients' OSA was classified as none/mild (apnea-hypopnea index (AHI) < 15, n = 112), moderate (15 ≤ AHI < 30, n = 77), or severe (AHI ≥ 30, n = 80). We calculated the proportion of unique variance (PUV) for the five FOSQ subscales. ANOVA was used to determine if ESS and FOSQ were associated with OSA severity. Unpaired t tests compared ESS and FOSQ scores in our sample with published data.

RESULTS

The average AHI was 29.5 ± 31.5 events per hour (range = 0-175.8). The mean ESS score was 6.3 ± 4.8, and the mean global FOSQ score was 100.3 ± 18.2. PUVs for FOSQ subscales showed moderate-to-high unique contributions to FOSQ variance. ESS and global FOSQ score did not differ by AHI group. Only the FOSQ vigilance subscale differed by OSA severity with the severe group reporting more impairment than the moderate and none/mild groups. Our sample reported less sleepiness and daytime impairment than previously reported means in patients and controls.

CONCLUSIONS

Subjective sleepiness and functional impairment were not associated significantly with OSA severity in our sample of patients considering surgery for obesity. Further research is needed to understand individual differences in sleepiness in patients with OSA. If bariatric patients underreport symptoms, self-report measures are not an adequate substitute for objective assessment and clinical judgment when evaluating bariatric patients for OSA. Patients with severe obesity need evaluation for OSA even in the absence of subjective complaints.

Anthropometric Predictors of High Risk of Obstructive Sleep Apnea Syndrome in a Rural Population

Objective. To evaluate which anthropometric parameter better predicts the high risk of obstructive sleep apnea syndrome (OSA) in a rural population. Material and Method. 254 subjects were enrolled. We measured weight, height, waist circumference (WC) and neck circumference (NC) and calculated body mass index (BMI), waist-to-height ratio (WHtR) and neck circumference/height ratio (NC/Height). The risk of OSA was assessed by using Berlin Questionnaire. Results. Subjects with high risk of OSA had a significant higher BMI, WC, WHtR, NC, and NC/Height. A higher percentage of those with large WC (≥80cm and ≥94cm for women and men, respectively) (p<0.001), WHtR ≥0.5 (p<0.001), NC ≥40cm (p=0.004), NC/Height ratio ≥0.23 (p=0.002) had a high risk of OSA. Using ROC curves of anthropometric parameters studied we found that WHtR was the best predictor for high risk of OSA, with AUC of 0.760, 95% CI: 0.699 to 0.815. Conclusions. WHtR was the best predictor for high risk of OSA as assessed by the Berlin Questionnaire.

CPAP for the metabolic syndrome in patients with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea is associated with an increased prevalence of the metabolic syndrome and its components. It is unclear whether treatment of obstructive sleep apnea syndrome with continuous positive airway pressure (CPAP) would modify these outcomes.

METHODS

In our double-blind, placebo-controlled trial, we randomly assigned patients with obstructive sleep apnea syndrome to undergo 3 months of therapeutic CPAP followed by 3 months of sham CPAP, or vice versa, with a washout period of 1 month in between. Before and after each intervention, we obtained measurements of anthropometric variables, blood pressure, fasting blood glucose levels, insulin resistance (with the use of homeostasis model assessment), fasting blood lipid profile, glycated hemoglobin levels, carotid intima-media thickness, and visceral fat. The metabolic syndrome was defined according to National Cholesterol Education Program Adult Treatment Panel III criteria, with Asian cutoff values for abdominal obesity.

RESULTS

A total of 86 patients completed the study, 75 (87%) of whom had the metabolic syndrome. CPAP treatment (vs. sham CPAP) was associated with significant mean decreases in systolic blood pressure (3.9 mm Hg; 95% confidence interval [CI], 1.4 to 6.4; P=0.001), diastolic blood pressure (2.5 mm Hg; 95% CI, 0.9 to 4.1; P<0.001), serum total cholesterol (13.3 mg per deciliter; 95% CI, 5.3 to 21.3; P=0.005), non-high-density lipoprotein cholesterol (13.3 mg per deciliter; 95% CI, 4.8 to 21.8; P=0.009), low-density lipoprotein cholesterol (9.6 mg per deciliter; 95% CI, 2.5 to 16.7; P=0.008), triglycerides (18.7 mg per deciliter; 95% CI, 4.3 to 41.6; P=0.02), and glycated hemoglobin (0.2%; 95% CI, 0.1 to 0.4; P=0.003). The frequency of the metabolic syndrome was reduced after CPAP therapy (reversal found in 11 of 86 patients [13%] undergoing CPAP therapy vs. 1 of 86 [1%] undergoing sham CPAP). Accelerated hypertension developed 1 patient receiving CPAP therapy first, intolerance to CPAP developed in 2 others, and another patient declined to continue sham CPAP.

CONCLUSIONS

In patients with moderate-to-severe obstructive sleep apnea syndrome, 3 months of CPAP therapy lowers blood pressure and partially reverses metabolic abnormalities. (Funded by Pfizer; ClinicalTrials.gov number, NCT00694616.).

[Anesthesia and bariatric surgery]

Today obesity is accepted as an independent disease. The WHO describes obesity as an epidemic disease occurring worldwide and associated comorbidities affect all organ systems. Bariatric operations lead to an improvement or even complete remission of obesity-correlated comorbidities. Bariatric operations are conducted as restrictive, malabsorptive, or mixed procedures. The preoperative anesthetic evaluation of comorbidities is carried out with a special focus on preexisting impairments of cardiac and lung function (e.g. cardiomyopathy, obstructive respiratory dysfunctions). Extremely obese patients are at risk of aspiration. Airway management at anesthesia induction includes normal intubation or, if additional risk factors are present, either fiber optic awake intubation or rapid sequence induction. The pharmacokinetics of all applicable drugs are altered in extremely obese patients and they are at risk for developing postoperative thromboembolic complications with a high mortality rate. Therefore early and sufficient thrombotic prophylaxis is important.

Obstructive sleep apnea syndrome: from phenotype to genetic basis

Obstructive sleep apnea syndrome (OSAS) is a complex chronic clinical syndrome, characterized by snoring, periodic apnea, hypoxemia during sleep, and daytime hypersomnolence. It affects 4-5% of the general population. Racial studies and chromosomal mapping, familial studies and twin studies have provided evidence for the possible link between the OSAS and genetic factors and also most of the risk factors involved in the pathogenesis of OSAS are largely genetically determined. A percentage of 35-40% of its variance can be attributed to genetic factors. It is likely that genetic factors associated with craniofacial structure, body fat distribution and neural control of the upper airway muscles interact to produce the OSAS phenotype. Although the role of specific genes that influence the development of OSAS has not yet been identified, current researches, especially in animal model, suggest that several genetic systems may be important. In this chapter, we will first define the OSAS phenotype, the pathogenesis and the risk factors involved in the OSAS that may be inherited, then, we will review the current progress in the genetics of OSAS and suggest a few future perspectives in the development of therapeutic agents for this complex disease entity.

Stepped approach for prediction of syndrome Z in patients attending sleep clinic: a north Indian hospital-based study

PURPOSE

Syndrome Z is the occurrence of metabolic syndrome (MS) with obstructive sleep apnea. Knowledge of its risk factors is useful to screen patients requiring further evaluation for syndrome Z.

METHODS

Consecutive patients referred from sleep clinic undergoing polysomnography in the Sleep Laboratory of AIIMS Hospital, New Delhi were screened between June 2008 and May 2010, and 227 patients were recruited. Anthropometry, body composition analysis, blood pressure, fasting blood sugar, and lipid profile were measured. MS was defined using the National Cholesterol Education Program (adult treatment panel III) criteria, with Asian cutoff values for abdominal obesity.

RESULTS

Prevalence of MS and syndrome Z was 74% and 65%, respectively. Age, percent body fat, excessive daytime sleepiness (EDS), and ΔSaO(2) (defined as difference between baseline and minimum SaO(2) during polysomnography) were independently associated with syndrome Z. Using a cutoff of 15% for level of desaturation, the stepped predictive score using these risk factors had sensitivity, specificity, positive predictive value, and negative predictive value of 75%, 73%, 84%, and 61%, respectively for the diagnosis of syndrome Z. It correctly characterized presence of syndrome Z 75% of the time and obviated need for detailed evaluation in 42% of the screened subjects.

CONCLUSIONS

A large proportion of patients presenting to sleep clinics have MS and syndrome Z. Age, percent body fat, EDS, and ΔSaO(2) are independent risk factors for syndrome Z. A stepped predictive score using these parameters is cost-effective and useful in diagnosing syndrome Z in resource-limited settings.

Predicting sleep apnea in bariatric surgery patients

BACKGROUND

Because of the high prevalence and potentially serious complications of obstructive sleep apnea (OSA) in obese individuals, several prediction models have been developed to detect moderate-to-severe OSA in patients undergoing bariatric surgery. Using commonly collected variables (body mass index [BMI], age, observed sleep apnea, hemoglobin A1c, fasting plasma insulin, gender, and neck circumference), Dixon et al. developed a model with a sensitivity of 89% and specificity of 81% for patients undergoing laparoscopic adjustable gastric band surgery suspected to have OSA. The present study evaluated the prediction model of Dixon et al. in 310 gastric bypass patients (mean BMI 46.8 kg/m(2), age 41.6 years, 84.5% women), with no preselection for OSA symptoms in a bariatric surgery partnership.

METHODS

The patients underwent overnight limited polysomnography to determine the presence and severity of OSA as measured using the apnea-hypopnea index.

RESULTS

Of the 310 patients, 44.2% had moderate-to-severe OSA (apnea-hypopnea index ≥ 15/h). Most variables in the Dixon model were associated with a greater prevalence of OSA. The sensitivity (75%) and specificity (57%) for the model-based classification of OSA were considerably lower in the present sample than originally reported. An alternate prediction model identified 10 unique predictors of OSA. The presence of ≥ 5 of these predictors modestly improved the sensitivity (77%) and greatly improved the specificity (77%) in predicting an apnea-hypopnea index of ≥ 15/h. When applied to the validation sample, the sensitivity (76%) and specificity (72%) were essentially the same.

CONCLUSION

Although the Dixon model and our model included overlapping predictors (BMI, gender, age, neck circumference), when applied in our sample of gastric bypass patients, neither model achieved the sensitivity and specificity for predicting OSA previously reported by Dixon et al.

A novel approach to prediction of mild obstructive sleep disordered breathing in a population-based sample: the Sleep Heart Health Study

This manuscript considers a data-mining approach for the prediction of mild obstructive sleep disordered breathing, defined as an elevated respiratory disturbance index (RDI), in 5,530 participants in a community-based study, the Sleep Heart Health Study. The prediction algorithm was built using modern ensemble learning algorithms, boosting in specific, which allowed for assessing potential high-dimensional interactions between predictor variables or classifiers. To evaluate the performance of the algorithm, the data were split into training and validation sets for varying thresholds for predicting the probability of a high RDI (≥7 events per hour in the given results). Based on a moderate classification threshold from the boosting algorithm, the estimated post-test odds of a high RDI were 2.20 times higher than the pre-test odds given a positive test, while the corresponding post-test odds were decreased by 52% given a negative test (sensitivity and specificity of 0.66 and 0.70, respectively). In rank order, the following variables had the largest impact on prediction performance: neck circumference, body mass index, age, snoring frequency, waist circumference, and snoring loudness.

Different impacts of neck circumference and visceral obesity on the severity of obstructive sleep apnea syndrome

Our aim was to investigate the significance of neck circumference (NC) on the presence and severity of obstructive sleep apnea (OSA) syndrome independent of visceral fat (VF) obesity. A total of 219 subjects with suspected OSA underwent a complete polysomnography (PSG) study, along with the measurement of NC, and total body fat (TF) and VF levels (VFLs) measured by bioelectrical impedance analysis. We proposed NC divided by height (NC/H) as the simple index for height-corrected NC in Japanese subjects. NC/H exhibited a significantly stronger correlation than NC per se with BMI (r = 0.781 vs. 0.675, P = 0.0178), TF (r = 0.531 vs. 0.156, P < 0.0001), and VF (r = 0.819 vs. 0.731, P = 0.0203), indicating that NC/H is a better indicator of visceral obesity than NC per se. Interestingly, despite the strong correlation between NC/H and VFL, VFL was significantly associated with the apnea-hypopnea index (AHI) ≥ 5, ≥ 15, and ≥ 30, but not with ≥ 40 or ≥ 50, whereas NC/H was significantly associated with higher AHI values, i.e., AHI ≥ 50 but not with lower AHI value. Furthermore, multiple regression analyses revealed that VFL and NC/H were independently associated with the square root of AHI (AHI(0.5)) levels in obese and nonobese patients, respectively. In conclusion, NC is associated with the severity of OSA independently of visceral obesity, especially in nonobese patients.

Prediction of obstructive sleep apnea syndrome in a large Greek population

PURPOSE

We aimed to evaluate the predictive value of anthropometric measurements and self-reported symptoms of obstructive sleep apnea syndrome (OSAS) in a large number of not yet diagnosed or treated patients. Commonly used clinical indices were used to derive a prediction formula that could identify patients at low and high risk for OSAS.

METHODS

Two thousand six hundred ninety patients with suspected OSAS were enrolled. We obtained weight; height; neck, waist, and hip circumference; and a measure of subjective sleepiness (Epworth sleepiness scale--ESS) prior to diagnostic polysomnography. Excessive daytime sleepiness severity (EDS) was coded as follows: 0 for ESS ≤ 3 (normal), 1 for ESS score 4-9 (normal to mild sleepiness), 2 for score 10-16 (moderate to severe sleepiness), and 3 for score >16 (severe sleepiness). Multivariate linear and logistic regression analysis was used to identify independent predictors of apnea-hypopnea index (AHI) and derive a prediction formula.

RESULTS

Neck circumference (NC) in centimeters, body mass index (BMI) in kilograms per square meter, sleepiness as a code indicating EDS severity, and gender as a constant were significant predictors for AHI. The derived formula was: AHIpred = NC × 0.84 + EDS × 7.78 + BMI × 0.91 - [8.2 × gender constant (1 or 2) + 37]. The probability that this equation predicts AHI greater than 15 correctly was 78%.

CONCLUSIONS

Gender, BMI, NC, and sleepiness were significant clinical predictors of OSAS in Greek subjects. Such a prediction formula can play a role in prioritizing patients for PSG evaluation, diagnosis, and initiation of treatment.

Update on best practice recommendations for anesthetic perioperative care and pain management in weight loss surgery, 2004-2007

To reevaluate and update evidence-based best practice recommendations published in 2004 for anesthetic perioperative care and pain management in weight loss surgery (WLS), we performed a systematic search of English-language literature on anesthetic perioperative care and pain management in WLS published between April 2004 and May 2007 in MEDLINE and the Cochrane Library. We identified relevant abstracts by using key words, retrieved full text articles, and stratified the resulting evidence according to systems used in established evidence-based models. We updated prior evidence-based best practice recommendations based upon interim literature. In instances of controversial or inadequate scientific evidence, the task force reached consensus recommendations following evaluation of the best available information and expert opinion. The search yielded 1,788 abstracts, with 162 potentially relevant titles; 45 were reviewed in detail. Despite more information on perioperative management of patients with obstructive sleep apnea (OSA), evidence to support preoperative testing and treatment or to guide perioperative monitoring is scarce. New evidence on appropriate intraoperative dosing of muscle relaxants allows for greater precision in their use during WLS. A novel application of alpha-2 agonists for perioperative anesthetic care is emerging. Key elements that may enhance patient safety include integration of the latest evidence on WLS, obesity, and collaborative multidisciplinary care into clinical care. However, large gaps remain in the evidence base.

Prevalence and risk factors of obstructive sleep apnea among middle-aged urban Indians: a community-based study

BACKGROUND

The epidemiology of obstructive sleep apnea (OSA) and obstructive sleep apnea syndrome (OSAS) is not well studied among Indians. We sought to determine the prevalence and risk factors of OSA in a middle-aged urban Indian population.

METHODS

We conducted a two-stage, cross-sectional, community-based study in four different socioeconomic zones of the South Delhi district, India, from April 2005 to June 2007. In stage 1, subjects of either gender aged 30-65 yrs were administered a questionnaire by door-to-door survey using systematic random sampling. Subjects that responded were classified as habitual and non-habitual snorers. In stage 2, all the habitual and 10% of randomly selected non-habitual snorers were invited for overnight polysomnographic study.

RESULTS

Of the 2860 subjects approached, 2505 (88%) completed stage 1. Habitual snoring was present in 452 (18%) subjects. In stage 2, OSA defined as apnea-hypopnea index 5 was observed in 94 (32.4%) of 290 habitual snorers and 3 (4%) of 75 non-habitual snorers. Estimated population prevalence of OSA and OSAS was 9.3% (95% CI 8.2-10.5%) and 2.8% (2.1-3.4%) respectively. On multivariable analysis, male gender (adjusted odds ratio 3.8 [1.7-4.9]), body-mass index 25 kg/m(2) (4.1 [2.0-8.3]), and abdominal obesity (2.2 [1.9-5.3]) were independently associated with the presence of OSA. A linear trend was observed in the prevalence of OSA across the socioeconomic strata.

CONCLUSIONS

OSA is a significant public health problem in the middle-aged Indian population across the socioeconomic spectrum. OSA is associated with some of the well known risk factors for cardiovascular disease.

Inter- and intra-rater reliability of neck circumference measurements in children

RATIONALE

Increased neck circumference is a risk factor for obstructive sleep apnea in adults. With rising obesity prevalence in children, it may be an important identifier of obstructive sleep apnea in children. The reliability of measuring neck circumference in children has not been systematically evaluated.

OBJECTIVE

To determine the inter- and intra-rater reliability of neck circumference measurements in children aged 2-16 years.

METHODS

Children aged 2-16 years with limb fractures were recruited. Neck circumference was measured by three investigators each using two separate unmarked paper tapes in the 2-5 year age group (N = 43), and three separate tapes in the 6-10 and 11-16 year age groups (N = 18 and 40).

RESULTS

Neck circumference measurements showed excellent inter-rater reliability for children 6-10 and 11-16 years (ICC = 0.952 and 0.989). Substantial variation was observed for the 2-5 year age group (ICC = 0.701). Good intra-rater reliability was demonstrated for the three groups (ICC range: 0.776, 0.950). Repeatability coefficients were 2.5-3.4 cm in the youngest age group and were 1.2-1.4 cm in the 6-16 year age group.

CONCLUSION

In children 6-16 years old, neck circumference shows very good inter and good intra-rater reliability. Multiple measurements are not required for precision and reliability.

Usefulness of truncal obesity indices as predictive factors for obstructive sleep apnea syndrome

BACKGROUND

Optimization of the indications for nocturnal polysomnography in the diagnosis of obstructive sleep apnea syndrome (OSAS) could lead to significant reductions in health expenditure. To this end, we assessed the usefulness of truncal obesity measurements in the diagnosis of OSAS.

METHODS AND PROCEDURES

One hundred ninety-two patients (152 men and 40 women) referred to our clinic with suspected OSAS underwent a complete polysomnography study and their BMI and truncal obesity measurements were obtained.

RESULTS

Comparison of patients defined as snorers with OSAS patients, by means of the Student's t -test revealed significant differences in the truncal obesity parameters such as waist-to-hip ratio (0.94 vs. 0.98) and waist circumference (100.7 cm vs. 106.3 cm). We found no significant differences between BMI values in the two groups. Indices of truncal obesity were analyzed as predictive factors for OSAS using a multivariate logistic regression model that included variable sex, and in which waist-to-hip ratio, BMI, neck circumference, and age were analyzed as binary variables. According to this model, our patients' risk of suffering from OSAS was 2.6 times greater if the waist-to-hip ratio was >1 in men and >0.85 in women. The risk of OSAS was also increased if the patients were men or over 52 years of age.

DISCUSSION

Obtaining simple measurements such as those for truncal obesity may help prioritize the use of polysomnography in patients with a greater risk of OSAS. Our results suggest that BMI is not a good predictor of OSAS in a group of patients with a high BMI.

Challenges in pulmonary risk assessment and perioperative management in bariatric surgery patients

Bariatric surgery has serious associated medical comorbidity and procedure-related risks and is, thus, considered an intermediate-to-high-risk non-cardiac surgery. Altered respiratory mechanics, obstructive sleep apnea (OSA), and less often, pulmonary hypertension and postoperative pulmonary embolism are the major contributors to poor pulmonary outcomes in obese patients. Attention to posture and positioning is critical in patients with OSA. Suspected OSA patients requiring intravenous narcotics should be kept in a monitored setting with frequent assessments and naloxone kept at the bedside. Use of reverse Tredelenburg position, preinduction, maintenance of positive end-expiratory pressure, and use of continuous positive airway pressure can help improve oxygenation in the perioperative period.

Obesity, and not obstructive sleep apnea, is responsible for increased serum hs-CRP levels in patients with sleep-disordered breathing in Delhi

OBJECTIVE

The present study was conducted to evaluate serum levels of high-sensitivity C-reactive protein (hs-CRP) in newly diagnosed patients with obstructive sleep apnea (OSA).

SUBJECTS AND METHODS

Between April 2005 and March 2006, a total of 231 consecutive adult habitual snorers underwent polysomnography (PSG) in the sleep laboratory. Ninety-seven subjects were found suitable for hs-CRP measurement after application of the following exclusion criteria: patients with diabetes mellitus, hypertension, coronary artery disease, acromegaly, hypothyroidism, chronic renal failure, congestive cardiac failure, or smoking history, patients who were pregnant, on steroid treatment, on hormone replacement therapy, or with chronic use of drugs such as non-steroidal anti-inflammatory drugs, oral anticoagulants and lipid-lowering drugs and patients having undergone upper airway surgery. Patients were classified as apneic [apnea-hypopnea index (AHI)>5], obese non-apneic [body mass index (BMI)>25, AHI<5] and non-obese non-apneic (BMI<25, AHI<5). C-reactive protein levels were measured in stored sera by high-sensitivity enzyme immunoassay (Biocheck, Inc. Foster City, CA, USA). After checking normality with the Kolmogorov-Smirnov test and using a square-root transformation, Pearson's and partial correlation coefficients were calculated for identified risk factors and confounders. A multiple linear regression model was used to identify variables that were independently associated with hs-CRP.

RESULTS

The mean serum levels of hs-CRP were found to be 0.25+/-0.23, 0.58+/-0.55, and 0.51+/-0.37 mg/dl in non-obese non-apneics (n=23), obese non-apneics (n=45) and apneics (obese and non-obese, n=29), respectively. Pearson's correlation coefficient of hs-CRP with BMI was found to be 0.25 (p=0.01), and with AHI 0.16 (p=0.12). Partial correlation analysis showed that hs-CRP levels correlated significantly with BMI after adjustment for AHI and age (r=0.22, p=0.03), while correlation with disease severity as assessed by AHI after adjustment for BMI and age was not significant (r=0.10, p=0.33). After stepwise multiple linear regression, only BMI was found to be significantly associated with serum hs-CRP levels (beta=0.02, p=0.01).

CONCLUSIONS

In this first comprehensive cross-sectional study on Indian subjects, we found that obesity, and not obstructive sleep apnea, is associated with elevated serum levels of hs-CRP. No independent correlation was found between severity of OSA and hs-CRP in the present study.

The incremental effect of obstructive sleep apnoea syndrome on arterial stiffness in newly diagnosed essential hypertensive subjects

OBJECTIVE

Although obstructive sleep apnoea syndrome (OSAS) is accompanied by an increased atherosclerotic cardiovascular disease burden, its relationship with arterial stiffness is not yet well determined. We investigated whether essential hypertensive individuals with OSAS are characterized by increased arterial stiffness.

METHODS

Our study population consisted of 46 consecutive patients with newly diagnosed untreated stage I-II essential hypertension suffering from OSAS (35 men, aged 49 +/- 8 years) and 53 hypertensive individuals without OSAS, matched for age, sex, and smoking status. All subjects underwent polysomnography, echocardiography and aortic stiffness evaluation by means of carotid-femoral pulse wave velocity (c-fPWV) measurements.

RESULTS

Hypertensive subjects with OSAS [apnoea/hypopnoea index (AHI)>or =5] compared with hypertensive subjects without OSAS (AHI < 5) demonstrated increased levels of body mass index (31.4 +/- 4 versus 29.3 +/- 4 kg/m2, P = 0.015), office systolic/diastolic blood pressure (151/99 versus 145/94 mmHg, respectively, P < 0.05, for both cases) and relative wall thickness (RWT; 0.46 +/- 0.06 versus 0.42 +/- 0.07, P=0.010). Hypertensive subjects with OSAS compared with those without OSAS had significantly increased c-fPWV by 9% (8.56 +/- 0.49 versus 7.85 +/- 0.93 m/s, P=0.001) and this difference remained significant even after adjustment for confounders (P=0.04). In the total study population, c-fPWV was correlated with age (r=0.35, P=0.015), office systolic blood pressure (r=0.30, P=0.007), RWT (r=0.30, P=0.03), logAHI (r=0.389, P=0.0001) and minimum oxygen saturation (r=-0.418, P=0.0001).

CONCLUSIONS

OSAS has a significant incremental effect on aortic stiffening in the setting of middle-aged essential hypertensive subjects. This finding suggests that the presence of OSAS in a hypertensive patient accelerates vascular damage, increasing cardiovascular risk.

Obesity, and not obstructive sleep apnea, is responsible for metabolic abnormalities in a cohort with sleep-disordered breathing

OBJECTIVE

To assess the profile of metabolic abnormalities in subjects with obstructive sleep apnea (OSA).

PATIENTS AND METHODS

In a case-control study conducted in two years, from April 2003 to March 2005, data obtained from polysomnography study, lipid profile, fasting blood sugar, serum insulin, insulin resistance, leptin and adiponectin levels, were compared between the various groups. Included in the study were OSA subjects from a sleep laboratory and matched controls from the community. Those with recent myocardial infarction, upper airway surgery, class III/IV heart failure, pregnancy, acromegaly, chronic renal failure, or who were on treatment for hyperthyroidism, on systemic steroid treatment, or on hormonal replacement therapy, were excluded from the study.

RESULTS

Forty apneic obese subjects (AHI=32.19, range 13-52.75) were compared with 40 non-apneic obese controls (AHI=1.3, range 0-2.45) and 40 normal weight control subjects (AHI=0.7, range 0-1). No significant difference was noted in levels of fasting blood sugar, insulin resistance (obese apneics 61.9, obese controls 47.8, non-obese controls 19.1), leptin (obese apneics 10.65 microg/L, obese controls 8.52 microg/L, non-obese controls 2.83 microg/L) or adiponectin (obese apneics 4959.3 ng/ml, obese controls 5706 ng/ml, non-obese controls 7412 ng/ml) in the OSA group compared to obese controls.

CONCLUSIONS

OSA has no independent association with lipid abnormalities, insulin resistance, serum leptin and adiponectin levels. In multivariate analysis, obesity was the major determinant of metabolic abnormalities in this cohort.

Prevalence and risk factors of obstructive sleep apnea syndrome in a population of Delhi, India

OBJECTIVE

Obstructive sleep apnea (OSA) has been recognized in the Western world as a public health burden, but there has been no community-based study performed to assess the prevalence of the condition in India. The study was performed to assess the prevalence and risk factors of OSA in a semi-urban Indian population.

DESIGN

A two-stage, cross-sectional, community-based prevalence study.

SETTING

A semi-urban community in Delhi.

DURATION

Two years (2003 to 2005).

PATIENTS AND PARTICIPANTS

All citizens residing in the community who were 30 to 60 years of age. Exclusion criteria included those patients with recent myocardial infarction, upper airway surgery, class III/IV congestive heart failure, pregnancy, hypothyroidism on treatment, acromegaly, chronic renal failure, systemic steroid treatment, and hormone replacement therapy.

INTERVENTION

An OSA assessment was performed in 2,400 subjects who were screened in stage 1 of the study by means of a sleep questionnaire. Subjects were then divided into habitual and nonhabitual snorers. Eighty-three randomly selected habitual snorers and 80 nonhabitual snorers were invited to participate in stage 2 of the study, which consisted of in-hospital polysomnography studies.

OBSERVATIONS AND RESULTS

A total of 2,150 subjects returned questionnaires (response rate, 90%). Of 550 habitual snorers and 1,596 nonhabitual snorers, 77 habitual snorers and 73 nonhabitual snorers underwent polysomnography. A total of 36 habitual snorers (46.75%) and 2 nonhabitual snorers (2.73%) were found to have OSA, giving prevalence rates of 13.74% and 3.57%, respectively, for OSA and OSA syndrome (OSAS) on extrapolation. Multivariate analysis revealed that male gender, age, obesity (defined by a high body mass index), and waist/hip ratio as significant risk factors for OSAS.

CONCLUSIONS

This study demonstrated that the risk factors and prevalence for OSA in India are similar to those in the West, which is contrary to the findings of some previous reports, which had a strong inclusion bias.

Shared genetic risk factors for obstructive sleep apnea and obesity

Both obesity and obstructive sleep apnea (OSA) are complex disorders with multiple risk factors, which interact in a complicated fashion to determine the overall phenotype. In addition to environmental risk factors, each disorder has a strong genetic basis that is likely due to the summation of small to moderate effects from a large number of genetic loci. Obesity is a strong risk factor for sleep apnea, and there are some data to suggest sleep apnea may influence obesity. It is therefore not surprising that many susceptibility genes for obesity and OSA should be shared. Current research suggests that approximately half of the genetic variance in the apnea hypopnea index is shared with obesity phenotypes. Genetic polymorphisms that increase weight will also be risk factors for apnea. In addition, given the interrelated pathways regulating both weight and other intermediate phenotypes for sleep apnea such as ventilatory control, upper airway muscle function, and sleep characteristics, it is likely that there are genes with pleiotropic effects independently impacting obesity and OSA traits. Other genetic loci likely interact with obesity to influence development of OSA in a gene-by-environment type of effect. Conversely, environmental stressors such as intermittent hypoxia and sleep fragmentation produced by OSA may interact with obesity susceptibility genes to modulate the importance that these loci have on defining obesity-related traits.