The effect of a very low-calorie diet-induced weight loss on the severity of obstructive sleep apnoea and autonomic nervous function in obese patients with obstructive sleep apnoea syndrome

Advancements in the neurocirculatory reflex response to hypoxia

Hypoxia is a pivotal factor in the pathophysiology of various clinical conditions, including obstructive sleep apnea, which has a strong association with cardiovascular diseases like hypertension, posing significant health risks. Although the precise mechanisms linking hypoxemia-associated clinical conditions with hypertension remains incompletely understood, compelling evidence suggests that hypoxia induces plasticity of the neurocirculatory control system. Despite variations in experimental designs and the severity, frequency, and duration of hypoxia exposure, evidence from animal and human models consistently demonstrates the robust effects of hypoxemia in triggering reflex-mediated sympathetic activation. Both acute and chronic hypoxia alters neurocirculatory regulation and, in some circumstances, leads to sympathetic outflow and elevated blood pressures that persist beyond the hypoxic stimulus. Dysregulation of autonomic control could lead to adverse cardiovascular outcomes and increase the risk of developing hypertension.

Obstructive sleep apnea heterogeneity and autonomic function: a role for heart rate variability in therapy selection and efficacy monitoring

Obstructive sleep apnea is a highly prevalent sleep-related breathing disorder, resulting in a disturbed breathing pattern, changes in blood gases, abnormal autonomic regulation, metabolic fluctuation, poor neurocognitive performance, and increased cardiovascular risk. With broad inter-individual differences recognised in risk factors, clinical symptoms, gene expression, physiological characteristics, and health outcomes, various obstructive sleep apnea subtypes have been identified. Therapeutic efficacy and its impact on outcomes, particularly for cardiovascular consequences, may also vary depending on these features in obstructive sleep apnea. A number of interventions such as positive airway pressure therapies, oral appliance, surgical treatment, and pharmaceutical options are available in clinical practice. Selecting an effective obstructive sleep apnea treatment and therapy is a challenging medical decision due to obstructive sleep apnea heterogeneity and numerous treatment modalities. Thus, an objective marker for clinical evaluation is warranted to estimate the treatment response in patients with obstructive sleep apnea. Currently, while the Apnea-Hypopnea Index is used for severity assessment of obstructive sleep apnea and still considered a major guide to diagnosis and managements of obstructive sleep apnea, the Apnea-Hypopnea Index is not a robust marker of symptoms, function, or outcome improvement. Abnormal cardiac autonomic modulation can provide additional insight to better understand obstructive sleep apnea phenotyping. Heart rate variability is a reliable neurocardiac tool to assess altered autonomic function and can also provide cardiovascular information in obstructive sleep apnea. Beyond the Apnea-Hypopnea Index, this review aims to discuss the role of heart rate variability as an indicator and predictor of therapeutic efficacy to different modalities in order to optimise tailored treatment for obstructive sleep apnea.

The effects of low calorie, high protein diet on body composition, duration and sleep quality on obese adults: A randomized clinical trial

Background and Aims

The effects of high-protein diets on regulating sleep have received research attention in recent decades. However, no studies have examined the effects of these diets in obese adults. Therefore, this study was conducted to investigate the effects of low-calorie high protein diets on sleep quality in obese adults.

Methods

This study is a randomized clinical trial conducted on 60 obese adults (BMI > 29.9 kg/m2) diagnosed with low-quality sleep. All participants were given a diet with a 750-calorie energy deficit. While the control group was given a normal diet, the intervention group received a diet with 30% more protein.

Results

The results showed a significant difference between the control group and intervention group with respect to sleep apnea at 30-, 60-, and 90-day follow-up (p < 0.01). Sleep quality, apnea-hypopnea index (AHI), sleep latency (SL), and polysomnography were significantly different between the two groups (p < 0.05), showing an improvement in sleep quality and obstructive sleep apnea in the intervention group (p < 0.05).

Conclusion

This study shows that low-calorie high-protein diets can effectively improve apnea, sleep quality, and body composition indices in obese adults.

Screening of obstructive sleep apnea syndrome by the deep breathing technique

STUDY OBJECTIVES

Obstructive sleep apnea syndrome (OSAS) is associated with alterations in heart rate variability (HRV) in relation to chronic autonomic dysfunction. We tested the ability of the deep breathing technique-a simple way to evaluate HRV-to identify patients with OSAS.

METHODS

Consecutive patients referred for suspected OSAS (without obesity, diabetes, and heart diseases) were included. They underwent a measure of HRV at rest and of heart rate oscillations during expiration vs inspiration (DeltaHRDB) when breathing deeply at the resonant frequency of 6 cycles per minute (deep breathing technique) while sitting awake, followed by a nighttime polysomnography. We measured DeltaHRDB and performed temporal and spectral HRV analysis.

RESULTS

Of 31 included participants (77% male), 14 had mild to moderate OSAS (apnea-hypopnea index median [IQR]: 18 [12]) and 17 had no OSAS. The conventional HRV analysis did not reveal any difference between the groups with vs without OSAS. However, the DeltaHRDB was lower in those with than without OSAS. Lower DeltaHRDB correlated with higher apnea-hypopnea index, arousal index, and desaturation degree. A DeltaHRDB below 11 beats per minute (bpm) predicted OSAS with a sensitivity of 100% and specificity of 86%.

CONCLUSIONS

The deep breathing technique accurately identifies a reduction in cardiac changes in patients with mild to moderate OSAS. It could be used as a simple screening tool to select patients for polysomnography.

CITATION

Onanga M, Joanny S, Rivals I, et al. Screening of obstructive sleep apnea syndrome by the deep breathing technique. J Clin Sleep Med. 2023;19(2):293-302.

Surgical management of obstructive sleep apnoea: A position statement of the Australasian Sleep Association. Respirology 2020;25:1292-1308. [PMID: 33190389 PMCID: PMC7839593 DOI: 10.1111/resp.13967]

Surgery for adult obstructive sleep apnoea (OSA) plays a key role in contemporary management paradigms, most frequently as either a second‐line treatment or in a facilitatory capacity. This committee, comprising two sleep surgeons and three sleep physicians, was established to give clarity to that role and expand upon its appropriate use in Australasia. This position statement has been reviewed and approved by the Australasian Sleep Association (ASA) Clinical Committee.

Association between a low-carbohydrate diet and sleep status, depression, anxiety, and stress score

BACKGROUND

Dietary intakes, especially carbohydrates, play an important role in blood glucose control in patients with diabetes. It is suggested that carbohydrate amounts may be effective in diabetes complications. This study aimed to reveal the association of low-carbohydrate diet (LCD) and sleep and mental status among patients with diabetes.

METHODS

This cross-sectional study was conducted among 265 women with type 2 diabetes. Anthropometric measures, as well as biochemical tests, were recorded. Dietary intakes were recorded using a validated food-frequency-questionnaire to calculate LCD score. To assess mental disorders and sleep quality, the Depression, Anxiety and Stress Scale and the Pittsburgh Sleep Quality Index were used respectively.

RESULTS

Patients in the highest LCD quartile were the ones with the lowest carbohydrate consumption. There was no significant association between cardiovascular risk factors and LCD score even after controlling confounder variables (P > 0.05). Subjects in the highest quartile of LCD score compared with those within the lowest quartile had a 69% lower risk of poor sleep after adjusting confounders. The odds of depressive symptoms were negatively related to the highest quartile of LCD score in the crude model and even after full-adjusted model (odds ratio: 0.42; 95% confidence interval: 0.17-1.01). Participants in the highest quartile of LCD score compared with those in the lowest quartile had a 73% lower risk of anxiety.

CONCLUSION

It seems that patients who consumed lower carbohydrate have better sleep status and are less involved with mental disorders. However, regarding the nature of the present study, well-designed cohort studies are suggested to be conducted in the future. © 2020 Society of Chemical Industry.

Weight loss and lifestyle interventions for obstructive sleep apnoea in adults: Systematic review and meta-analysis

Lifestyle interventions addressing diet, exercise-training, sleep hygiene, and/or tobacco/alcohol cessation are recommended in the management of obstructive sleep apnoea (OSA). Yet their effectiveness on this condition still requires further research. This systematic review and meta-analysis was aimed at establishing (a) the effectiveness of lifestyle interventions on apnoea-hypopnoea index (AHI), oxygen desaturation index (ODI), excessive daytime sleepiness (EDS), and secondary OSA measures among adults, and (b) which intervention characteristics may drive the greatest improvements. A systematic search of studies was conducted using CINAHL, ProQuest, Psicodoc, Scopus, and Web of Science, from inception to April 2018. Standardized mean differences were calculated using the inverse variance method and random-effects models. The meta-analyses of 13 randomized controlled trials and 22 uncontrolled before-and-after studies (1420 participants) revealed significant reductions on AHI (d = -0.61 and -0.46, respectively), ODI (d = -0.61 and -0.46) and EDS (d = -0.41 and -0.49). Secondary OSA outcomes were also improved after interventions. However, effectiveness of interventions differed depending on their components, OSA severity, and gender. Thus, until future research further supports the differential effectiveness among lifestyle interventions on OSA, those addressing weight loss through diet and exercise-training may be the most effective treatments for male patients with moderate-severe OSA.

Weight Management in Obstructive Sleep Apnea: Medical and Surgical Options

Obesity plays a pivotal role in the pathogenesis of obstructive sleep apnea (OSA) and as an exacerbating factor of OSA. Given the interlinking relationship of obesity and OSA, treatment of obesity is fundamental in the management of OSA. Weight loss of 7% to 11% significantly improves OSA with remission seen with greater weight loss. Weight loss also ameliorates the constellation of other obesity-related metabolic conditions, reducing the overall cardiovascular risk in an obese person with OSA. This article discusses specific weight loss interventions effective in improving OSA, including lifestyle interventions with dietary modification and physical activity, pharmacotherapy, and bariatric surgery.

Effects of obesity therapies on sleep disorders

Obesity is a significant risk factor for obstructive sleep apnea syndrome (OSAS), and has also been linked to reductions in sleep quality and quantity. Weight loss has been shown to be an effective treatment for improving OSAS; however, there is a high degree of variability in improvements of OSAS in response to weight loss. There are three modalities of obesity therapies: 1) lifestyle modification, which includes changes in dietary intake and physical activity, along with behavioral interventions; 2) pharmacologic agents; and 3) bariatric surgery. Individuals have a highly variable response to the various obesity interventions, and maintenance of weight loss can be especially challenging. These factors influence the effect of weight loss on sleep disorders. There is still a need for large, well-controlled studies examining short- and long-term efficacy of weight loss modalities and their impact on long-term treatment of OSAS and other sleep parameters, particularly in youth. Nonetheless, given our current knowledge, weight reduction should always be encouraged for people coping with obesity, OSAS, and/or sleep disruptions and resources identified to assist patients in choosing a weight loss approach that will benefit them the most.

Maintenance diets following rapid weight loss in obstructive sleep apnea: a pilot 1-year clinical trial

Very low energy diets (VLED) appear to be the most efficacious dietary-based obesity reduction treatments in obstructive sleep apnea (OSA); however, effective weight loss maintenance strategies remain untested in this condition. Our study aimed to assess the feasibility, tolerability and efficacy of two common maintenance diets during a 10-month follow-up period after rapid weight loss using a 2-month VLED. In this two-arm, single-centre, open-label pilot trial, obese adult OSA patients received a 2-month VLED before being allocated to either the Australian Guide to Healthy Eating diet (AGHE) or a low glycaemic index high-protein diet (LGHP). Outcomes were measured at 0, 2 and 12 months. We recruited 44 patients [113.1 ± 19.5 kg, body mass index (BMI): 37.2 ± 5.6 kg m^-2 , 49.3 ± 9.2 years, 12 females]. Twenty-four patients were on continuous positive airway pressure (CPAP) or mandibular advancement splint (MAS) therapy for OSA. Forty-two patients completed the VLED. The primary outcome of waist circumference was reduced by 10.6 cm at 2 months [95% confidence interval (CI): 9.2-12.1], and patients lost 12.9 kg in total weight (95% CI: 11.2-14.6). There were small but statistically significant regains in waist circumference between 2 and 12 months [AGHE = 3.5 cm (1.3-5.6) and LGHP = 2.8 cm (0.6-5.0]. Other outcomes followed a similar pattern of change. After weight loss with a 2-month VLED in obese patients with OSA, a structured weight loss maintenance programme incorporating commonly used diets was feasible, tolerable and efficacious for 10 months. This programme may be deployed easily within sleep clinics; however, future research should first test its translation within general clinical practice.

Bariatric Surgery or Non-Surgical Weight Loss for Obstructive Sleep Apnoea? A Systematic Review and Comparison of Meta-analyses

BACKGROUND

Obstructive sleep apnoea (OSA) is a well-recognised complication of obesity. Non-surgical weight loss (medical, behavioural and lifestyle interventions) may improve OSA outcomes, although long-term weight control remains challenging. Bariatric surgery offers a successful strategy for long-term weight loss and symptom resolution.

OBJECTIVES

To comparatively appraise bariatric surgery vs. non-surgical weight loss interventions in OSA treatment utilising body mass index (BMI) and apnoea-hypopnoea index (AHI) as objective measures of weight loss and apnoea severity.

METHODS

A systematic literature review revealed 19 surgical (n = 525) and 20 non-surgical (n = 825) studies reporting the primary endpoints of BMI and AHI before and after intervention. Data were meta-analysed using random effects modelling. Subgroup analysis, quality scoring and risk of bias were assessed.

RESULTS

Surgical patients had a mean pre-intervention BMI of 51.3 and achieved a significant 14 kg/m(2) weighted decrease in BMI (95%CI [11.91, 16.44]), with a 29/h weighted decrease in AHI (95%CI [22.41, 36.74]). Non-surgical patients had a mean pre-intervention BMI of 38.3 and achieved a significant weighted decrease in BMI of 3.1 kg/m(2) (95%CI [2.42, 3.79]), with a weighted decrease in AHI of 11/h (95%CI [7.81, 14.98]). Heterogeneity was high across all outcomes.

CONCLUSIONS

Both bariatric surgery and non-surgical weight loss may have significant beneficial effects on OSA through BMI and AHI reduction. However, bariatric surgery may offer markedly greater improvement in BMI and AHI than non-surgical alternatives. Future studies must address the lack of randomised controlled and comparative trials in order to confirm the exact relationship between metabolic surgery and non-surgical weight loss interventions in OSA resolution.

The effects of moderate energy restriction on apnoea severity and CVD risk factors in obese patients with obstructive sleep apnoea

Nutritional intervention for weight loss is one of the treatment options for obstructive sleep apnoea (OSA) in patients with overweight or obesity. However, the effects of moderate energy restriction on OSA severity are not yet known. The present study aimed to evaluate the effects of moderate energy restriction on OSA severity and CVD risk factors in obese patients with OSA. In this 16-week randomised clinical trial, twenty-one obese subjects aged 20-55 years and presenting an apnoea/hypopnoea index (AHI)≥5 events/h were randomised into two groups: the energy restriction group (ERG) and the control group (CG). The ERG was instructed to follow an energy-restricted diet -3347·2 kJ/d (-800 kcal/d) and the CG was advised not to change their food intake. At the beginning and at the end of the study, participants underwent evaluation of the following: OSA (Watch-PAT200®), nutritional parameters, blood pressure, sympathetic activity, inflammatory biomarkers, metabolic profile and endothelial function. The ERG (n 11), compared with the CG (n 10), had a significantly greater reduction in body weight (Cohen's d=-1·19; P<0·001), in AHI (Cohen's d=-0·95; P=0·04) and in plasma concentrations of adrenaline (Cohen's d=-1·02; P=0·04) as well as a significantly greater increase in minimum O2 saturation (Cohen's d=1·08; P=0·03). Although energy restriction was not associated with significant improvements in CVD risk factors, medium-to-large effect sizes were observed, suggesting that the statistically non-significant difference between groups may be due to the small sample size. This study suggests that in obese patients with OSA, moderate energy restriction is able to reduce the parameters of OSA severity and sympathetic activity.

Weight loss from lifestyle interventions and severity of sleep apnoea: a systematic review and meta-analysis

BACKGROUND

Excess body weight is a risk factor for obstructive sleep apnoea (OSA). The aim of the systematic review was to establish whether weight loss via lifestyle interventions such as diet and exercise are useful in the treatment of OSA.

METHODS

A literature search was conducted between 1980 and February 2012. Systematic reviews and randomised controlled trials (RCTs) with participants who had OSA, were overweight or obese, and who had undergone lifestyle interventions with the aim of improving sleep apnoea were included. Meta analyses were conducted for a subset of RCTs with appropriate data.

RESULTS

Two systematic reviews and eight RCTs were included. Meta-analyses were conducted for four RCTs comparing intensive lifestyle interventions to a control. The overall weighted mean differences for weight change, change in apnoea -hypopnoea index (AHI) and change in oxygen desaturation index of ≥4% were as follows: -13.76 kg (95% confidence interval (CI) -19.21, --8.32), -16.09 (95% CI -25.64, -6.54) and -14.18 (95% CI -24.23, -4.13), respectively. Although high heterogeneity within the meta analyses, all studies favoured the interventions. Long-term follow-up data from three RCTs suggest that improvements in weight and AHI are maintained for up to 60 months.

CONCLUSIONS

Intensive lifestyle interventions are effective in the treatment of OSA, resulting in significant weight loss and a reduction in sleep apnoea severity. Weight loss via intensive lifestyle interventions could be encouraged as a treatment for mild to moderate OSA.

Weight loss through adjustable gastric banding and improvement in daytime sleepiness: 2 year interim results of APEX study

OBJECTIVE

Obesity is one factor associated with an increased risk of obstructive sleep apnea (OSA). This study reports the investigator-reported resolution or improvement of OSA and improvements in sleep-related quality of life (QOL) 2 years after surgical placement of the LAP-BAND AP * (LBAP) system.

RESEARCH DESIGN AND METHODS

The LBAP Experience (APEX) study is an ongoing 5 year, prospective, observational study assessing change in weight, comorbidities, and QOL after LBAP implantation. This is an interim analysis of patients with evaluable data at 24 months who had OSA at baseline.

CLINICAL TRIAL REGISTRATION

NCT00501085.

RESULTS

At baseline, 117 of 395 patients (29.6%; mean body mass index [BMI], 45.0 kg/m2) reported OSA; of these, 57 had evaluable patient-reported outcome data at 2 years. Investigator-reported resolution or improvement of OSA was 69% and 86% at post-operative years 1 and 2, respectively. Patients reporting resolution, improvement, or no change in OSA experienced mean changes in BMI and percentage of weight loss of -9.7 kg/m(2)/-21.7%, -8.3 kg/m(2)/-18.7%, and -5.7 kg/m(2)/-13.2%, respectively (n = 54). Mean 2 year BMI was not statistically different between the groups (p = not significant). Mean scores for all Epworth Sleepiness Scale responses for the OSA population improved by -0.43 from baseline (p < 0.0001; n = 78) compared with -0.29 for patients without OSA at baseline (n = 177; p = 0.037 between groups). In addition, the overall study population experienced resolution and/or improvement in other obesity-related comorbidities, such as type 2 diabetes (96%) and hypertension (91%).

CONCLUSIONS

These data support that surgically facilitated weight loss can improve sleep-related QOL and may result in resolution or improvement of OSA; the degree of weight loss may be related to these changes.

A pilot study investigating the effects of continuous positive airway pressure treatment and weight-loss surgery on autonomic activity in obese obstructive sleep apnea patients

BACKGROUND

We have previously demonstrated that severity of obstructive sleep apnea (OSA) as measured by the apnea-hypopnea index (AHI) is a significant independent predictor of readily-computed time-domain metrics of short-term heart rate variability (HRV).

METHODS

We aimed to assess time-domain HRV measured over 5-min while awake in a trial of obese subjects undergoing one of two OSA therapies: weight-loss surgery (n=12, 2 males, median and interquartile range (IQR) for BMI 43.7 [42.0, 51.4] kg/m2, and AHI 18.1 [16.3, 67.5] events/h) or continuous positive airway pressure (CPAP) (n=15, 11 males, median BMI 33.8 [31.3, 37.9] kg/m2, and AHI 36.5 [24.7, 77.3] events/h). Polysomnography was followed by electrocardiography during wakefulness; measurements were repeated at 6 and 12-18 months post-intervention.

RESULTS

Despite similar measurements at baseline, subjects who underwent surgery exhibited greater improvement in short-term HRV than those who underwent CPAP (p=0.04).

CONCLUSIONS

Our data suggest a possible divergence in autonomic function between the effects of weight loss resulting from bariatric surgery, and the amelioration of obstructive respiratory events resulting from CPAP treatment. Randomized studies are necessary before clinical recommendations can be made.

Impact of sleep-disordered breathing treatment on upper airway anatomy and physiology

Sleep-disordered breathing (SDB) is a major public health problem. Various anatomic, pathophysiologic, and environmental changes contribute to SDB. The successful treatment of SDB reverses many of these abnormal processes. The present article discusses the current clinical evidence that supports the reversibility and its potential application in the management of SDB. Continuous positive airway pressure reduces angiogenesis and inflammatory edema, increases pharyngeal size, and improves surrogate markers of vascular inflammation and tongue muscle fiber types. Mandibular advancement devices lead to favorable maxillary and mandibular changes, increase pharyngeal area, and improve hypertension. Uvulopalatopharyngoplasty increases posterior airway space and pharyngeal volume, reduces nasal and oral resistance, and lowers response to high CO2. Weight loss reduces nasopharyngeal collapsibility, critical closing pressure of the airway, apnea-hypopnea index, and improves oxygen saturations. Potential clinical benefits of these changes in the management of SDB and patient compliance with treatment are discussed.

Effectiveness of lifestyle interventions on obstructive sleep apnea (OSA): systematic review and meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA) is a common sleep disorder associated with several adverse health outcomes. Given the close association between OSA and obesity, lifestyle and dietary interventions are commonly recommended to patients, but the evidence for their impact on OSA has not been systematically examined.

OBJECTIVES

To conduct a systematic review and meta-analysis to assess the impact of weight loss through diet and physical activity on measures of OSA: apnea-hypopnea index (AHI) and oxygen desaturation index of 4% (ODI4).

METHODS

A systematic search was performed to identify publications using Medline (1948-2011 week 40), EMBASE (from 1988-2011 week 40), and CINAHL (from 1982-2011 week 40). The inverse variance method was used to weight studies and the random effects model was used to analyze data.

RESULTS

Seven randomized controlled trials (519 participants) showed that weight reduction programs were associated with a decrease in AHI (-6.04 events/h [95% confidence interval -11.18, -0.90]) with substantial heterogeneity between studies (I(2) = 86%). Nine uncontrolled before-after studies (250 participants) showed a significant decrease in AHI (-12.26 events/h [95% confidence interval -18.51, -6.02]). Four uncontrolled before-after studies (97 participants) with ODI4 as outcome also showed a significant decrease in ODI4 (-18.91 episodes/h [95% confidence interval -23.40, -14.43]).

CONCLUSIONS

Published evidence suggests that weight loss through lifestyle and dietary interventions results in improvements in obstructive sleep apnea parameters, but is insufficient to normalize them. The changes in obstructive sleep apnea parameters could, however, be clinically relevant in some patients by reducing obstructive sleep apnea severity. These promising preliminary results need confirmation through larger randomized studies including more intensive weight loss approaches.

Supine position related obstructive sleep apnea in adults: pathogenesis and treatment

The most striking feature of obstructive respiratory events is that they are at their most severe and frequent in the supine sleeping position: indeed, more than half of all obstructive sleep apnea (OSA) patients can be classified as supine related OSA. Existing evidence points to supine related OSA being attributable to unfavorable airway geometry, reduced lung volume, and an inability of airway dilator muscles to adequately compensate as the airway collapses. The role of arousal threshold and ventilatory control instability in the supine position has however yet to be defined. Crucially, few physiological studies have examined patients in the lateral and supine positions, so there is little information to elucidate how breathing stability is affected by sleep posture. The mechanisms of supine related OSA can be overcome by the use of continuous positive airway pressure. There are conflicting data on the utility of oral appliances, while the effectiveness of weight loss and nasal expiratory resistance remains unclear. Avoidance of the supine posture is efficacious, but long term compliance data and well powered randomized controlled trials are lacking. The treatment of supine related OSA remains largely ignored in major clinical guidelines. Supine OSA is the dominant phenotype of the OSA syndrome. This review explains why the supine position so favors upper airway collapse and presents the available data on the management of patients with supine related OSA.

Obstructive sleep apnea syndrome (OSAS) and hypertension: pathogenic mechanisms and possible therapeutic approaches

Obstructive sleep apnea syndrome (OSAS), a chronic condition characterized by collapse of the pharynx during sleep, has been increasingly recognized as a health issue of growing importance over the last decade. Recently emerging evidence suggests that there is a causal link between OSAS and hypertension, and hypertension represents an independent risk factor in OSAS patients. However, the pathophysiological basis for patients with OSAS having an increased risk for hypertension remains to be elucidated. The main acute physiological outcomes of OSAS are intermittent hypoxia, intrapleural pressure changes, and arousal from sleep, which might induce endothelial dysfunction, sympathetic activation, renin-angiotensin-aldosterone system activation, lipid metabolism dysfunction, and increased oxidative stress. This brief review focuses on the current understanding of the complex association between OSAS and hypertension.

Obesity and obstructive sleep apnea--clinical significance of weight loss

Obesity is a major health burden that contributes to increased morbidity and mortality. Obesity is also the most important risk factor for obstructive sleep apnea (OSA); at least 70% of patients are obese. OSA as such, has been linked with increased cardiovascular morbidity and mortality, and OSA patients often display metabolic syndrome. The exact underlying mechanisms behind these associations are complex and not fully understood. In obese individuals, weight reduction and increased physical activity form cornerstones for the prevention and treatment of metabolic syndrome, and recent controlled intervention trials strongly suggest that weight reduction together with a healthy diet and increased physical activity may correct or at least improve the symptoms of OSA. However, regardless of promising results in terms of symptoms of OSA and the undoubted metabolic benefits of changing lifestyles, weight reduction as a treatment of OSA is still underrated by many clinicians. Based on the current knowledge, clinicians should revise their previous attitudes, including suspicions about weight reduction as an effective treatment for OSA patients. Nevertheless, we also need large well-controlled trials on the effects of different weight reduction programs among OSA patients to determine the overall efficacy of different treatment modalities and their long-term success.

Obstructive sleep apnoea syndrome and weight loss: review

Obstructive sleep apnoea (OSA) syndrome is common, and obesity is a major risk factor. Increased peripharyngeal and central adiposity result in increased pharyngeal collapsibility, through increased mechanical loading around the upper airway, reduced tracheal traction on the pharynx, and reduced neuromuscular activity, particularly during sleep. Significant and sustained weight loss, if achieved, is likely to be a useful therapeutic option in the management of OSA and may be attempted by behavioural, pharmacological, and surgical approaches. Behavioural therapy programs that focus on aspects such as dietary intervention, exercise prescription patients and general lifestyle counselling have been tested. Bariatric surgery is an option in the severely obese when nonsurgical measures have failed, and laparoscopic adjustable gastric banding and Roux-en-Y gastric bypass are the most commonly employed techniques in the United Kingdom. Most evidence for efficacy of surgery comes from cohort studies. The role of sibutramine in OSA in the obese patients has been investigated, however, there are concerns regarding associated cardiovascular risk. In this paper the links between obesity and OSA are discussed, and the recent studies evaluating the behavioural, pharmacological and surgical approaches to weight loss in OSA are reviewed.

Obstructive sleep apnea

Obstructive sleep apnea (OSA) affects millions of Americans and is estimated to be as prevalent as asthma and diabetes. Given the fact that obesity is a major risk factor for OSA, and given the current global rise in obesity, the prevalence of OSA will increase in the future. Individuals with sleep apnea are often unaware of their sleep disorder. It is usually first recognized as a problem by family members who witness the apneic episodes or is suspected by their primary care doctor because of the individual's risk factors and symptoms. The vast majority remain undiagnosed and untreated, despite the fact that this serious disorder can have significant consequences. Individuals with untreated OSA can stop breathing hundreds of times a night during their sleep. These apneic events can lead to fragmented sleep that is of poor quality, as the brain arouses briefly in order for the body to resume breathing. Untreated, sleep apnea can have dire health consequences and can increase the risk of hypertension, diabetes, heart disease, and heart failure. OSA management has also become important in a number of comorbid neurological conditions, including epilepsy, stroke, multiple sclerosis, and headache. Diagnosis typically involves use of screening questionnaires, physical exam, and an overnight polysomnography or a portable home study. Treatment options include changes in lifestyle, positive airway pressure, surgery, and dental appliances.

Sleep-disordered breathing and obesity: pathophysiology, complications, and treatment

Sleep-disordered breathing (SDB) is a medical condition that has increasingly recognized adverse health effects. Obesity is the primary risk factor for the development of SDB and contributes to cardiovascular and metabolic abnormalities in this population. However, accumulating evidence suggests that SDB may be related to the development of these abnormalities independent of obesity. Periodic apneas and hypopneas during sleep result in intermittent hypoxemia, arousals, and sleep disturbances. These pathophysiologic characteristics of SDB are likely mechanisms underlying cardiovascular and metabolic abnormalities including hypertension and other cardiovascular diseases, altered adipokines, inflammatory cytokines, insulin resistance, and glucose intolerance. Treatment of SDB with continuous positive airway pressure reverses some but not all of these abnormalities; however, studies to date have demonstrated inconsistent findings. Weight loss strategies, including diet, exercise, medications, and bariatric surgery, have been evaluated as a treatment strategy for SDB. In preliminary studies, dietary intervention and exercise reduced severity of SDB. One study demonstrated improvements in SDB severity using the weight-reducing medication sibutramine. In morbidly obese subjects, bariatric surgery effectively induces weight loss and improvement in SDB severity and symptoms, but long-term benefits remain uncertain. Large randomized trials are required to determine the utility of these strategies as long-term approaches to improving SDB and reducing associated complications.

Neuroadrenergic dysfunction in obesity: an overview of the effects of weight loss

PURPOSE OF REVIEW

The prevalence of obesity is rising to epidemic proportions worldwide, and in tandem so is that of type 2 diabetes. Neuroadrenergic abnormalities, comprising increased resting sympathetic nervous system activity and blunted sympathetic neural responsiveness are recognized features of metabolic syndrome obesity, which contribute importantly to both the pathophysiology and adverse clinical prognosis of this high-risk population. Weight loss is recommended as first-line treatment for obesity. This review examines the effects of nonpharmacological weight loss on sympathetic nervous system function under basal and stimulated conditions.

RECENT FINDINGS

Human weight loss trials show that even moderate weight reduction is accompanied by significant attenuation in resting whole-body norepinephrine spillover rate and muscle sympathetic nerve activity, an improvement in cardiac autonomic modulation, and a reversal of blunted sympathetic responsiveness at both peripheral and central nervous system levels. Recent findings underscore the relevance of insulin resistance in mediating blunted sympathetic responsiveness to endogenous hyperinsulinemia induced by glucose ingestion. Impaired insulin transport across the blood-brain barrier may be one mechanism mediating these effects. Weight loss reverses blunted sympathetic responsiveness to glucose, which has implications for postprandial energy expenditure and body weight homeostasis.

SUMMARY

The autonomic dysfunction of obesity is reversible with weight loss, highlighting the importance of lifestyle intervention as a key therapeutic modality.

The relationship of obesity and obstructive sleep apnea

Obstructive sleep apnea is a common disorder, and obesity is a known risk factor for its development. The prevalence of obesity is increasing worldwide, and a corresponding increase in the prevalence of obstructive sleep apnea and its cardiovascular and noncardiovascular consequences is likely. This article reviews the established evidence supporting obesity as a risk factor for obstructive sleep apnea and discusses the evidence suggesting that obesity is also a consequence of obstructive sleep apnea. There is evidence that treating obesity reduces the severity of obstructive sleep apnea and that treating obstructive sleep apnea decreases obesity. However, the evidence does not support a sustained correlation between weight loss and improvement in sleep-disordered breathing.

Effect of a very low energy diet on moderate and severe obstructive sleep apnoea in obese men: a randomised controlled trial

OBJECTIVE

To assess the effect of weight loss induced by a very low energy diet on moderate and severe obstructive sleep apnoea in obese men. Design Single centre, two arm, parallel, randomised, controlled, open label trial. Blocked randomisation procedure used for treatment allocation. Setting Outpatient obesity clinic in a university hospital in Stockholm, Sweden. Participants 63 obese men (body mass index 30-40, age 30-65 years) with moderate to severe obstructive sleep apnoea (apnoea-hypopnoea index (AHI) >or=15), treated with continuous positive airway pressure.

INTERVENTIONS

The intervention group received a liquid very low energy diet (2.3 MJ/day) for seven weeks to promote weight loss, followed by two weeks of gradual introduction of normal food, reaching 6.3 MJ/day at week 9. The control group adhered to their usual diet during the nine weeks of follow-up.

MAIN OUTCOME MEASURE

AHI, the major disease severity index for obstructive sleep apnoea. Data from all randomised patients were included in an intention to treat analysis (baseline carried forward for missing data). Results Of the 63 eligible patients, 30 were randomised to intervention and 33 to control. Two patients in the control group were dissatisfied with allocation and immediately discontinued. All other patients completed the trial. Both groups had a mean AHI of 37 events/h (SD 15) at baseline. At week 9, the intervention group's mean body weight was 20 kg (95% confidence interval 18 to 21) lower than that of the control group, while its mean AHI was 23 events/h (15 to 30) lower. In the intervention group, five of 30 (17%) were disease free after the energy restricted diet (AHI <5), with 15 of 30 (50%) having mild disease (AHI 5-14.9), whereas the AHI of all patients in the control group except one remained at 15 or higher. In a subgroup analysis of the intervention group, baseline AHI significantly modified the effectiveness of treatment, with a greater improvement in AHI in patients with severe obstructive sleep apnoea (AHI >30) at baseline compared with those with moderate (AHI 15-30) sleep apnoea (AHI -38 v -12, P<0.001), despite similar weight loss (-19.2 v -18.2 kg, P=0.55). Conclusion Treatment with a low energy diet improved obstructive sleep apnoea in obese men, with the greatest effect in patients with severe disease. Long term treatment studies are needed to validate weight loss as a primary treatment strategy for obstructive sleep apnoea.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN70090382.

Effects and clinical potential of very-low-calorie diets (VLCDs) in type 2 diabetes

A recent study has shown that obese patients with newly diagnosed type 2 diabetes who lose 10% of their body weight are more likely to achieve glycaemic and blood pressure targets, despite weight regain. A well-established non-surgical method for achieving weight loss >or=10% within 3 months is the use of very-low-calorie diets (VLCDs). In patients with diabetes, VLCDs are associated with rapid improvement in glycaemia and cardiovascular risk factors. The present review analyses the evidence from available trials on the effects of VLCDs on body weight, glycaemic control and complications, and their potential for clinical use in diabetes management.

Obstructive Sleep Apnoea (OSA) Patterns in Bariatric Surgical Practice and Response of OSA to Weight Loss after Laparoscopic Adjustable Gastric Banding (LAGB)

Introduction: This study aims to evaluate the incidence of Obstructive Sleep Apnoea (OSA) in severely obese Asians and to study the impact of weight loss on OSA. Materials and Methods: We report the results of routine preoperative Polysomnograms in 350 Asian patients undergoing bariatric surgery in our institute. Polysomnograms were repeated in 75 randomly selected patients with moderate to severe OSA after target weight loss with the laparoscopically placed adjustable gastric band (LAGB). Results: The prevalence of OSA in obese Asians is high. Moderate OSA was found in 46% of patients and severe OSA was found in 33%. Severe OSA was significantly more in the Chinese (46%) compared to the Malays (29%) or Indians (21%) (P = 0.035). We identified other risk factors for severe OSA (male sex, higher body mass index and the presence of hypertension) but were unable to select identifying parameters for very low (<5%) likelihood of severe OSA such that routine sleep studies prior to bariatric surgery could be omitted. Apnoea Hypoapnoea Index (AHI) showed improvement of 50% at 20 kg excess weight loss with the cure of OSA in preoperatively severe cases (P <0.005). Mild to moderate cases reported similar improvements although a direct correlation could not be established. Desaturation events, apnoea episodes, work of breathing and subjective assessment of sleepiness scores and quality of life (QOL) showed improving trends, albeit not statistically significant. Similar improvements were seen in sleep architecture with increased rapid eye movement (REM) and stage 3 sleep. Conclusions: The incidence of OSA in Asians undergoing bariatric surgery is high. Routine sleep studies in Asian patients are justified. Weight loss brought about a significant improvement in AHI and continuous positive airway pressure requirements. LAGB placement should be considered a broadly effective therapy for sleep apnoea in the severely obese patient. Introduction: This study aims to evaluate the incidence of Obstructive Sleep Apnoea (OSA) in severely obese Asians and to study the impact of weight loss on OSA. Materials and Methods: We report the results of routine preoperative Polysomnograms in 350 Asian patients undergoing bariatric surgery in our institute. Polysomnograms were repeated in 75 randomly selected patients with moderate to severe OSA after target weight loss with the laparoscopically placed adjustable gastric band (LAGB). Results: The prevalence of OSA in obese Asians is high. Moderate OSA was found in 46% of patients and severe OSA was found in 33%. Severe OSA was significantly more in the Chinese (46%) compared to the Malays (29%) or Indians (21%) (P = 0.035). We identified other risk factors for severe OSA (male sex, higher body mass index and the presence of hypertension) but were unable to select identifying parameters for very low (<5%) likelihood of severe OSA such that routine sleep studies prior to bariatric surgery could be omitted. Apnoea Hypoapnoea Index (AHI) showed improvement of 50% at 20 kg excess weight loss with the cure of OSA in preoperatively severe cases (P <0.005). Mild to moderate cases reported similar improvements although a direct correlation could not be established. Desaturation events, apnoea episodes, work of breathing and subjective assessment of sleepiness scores and quality of life (QOL) showed improving trends, albeit not statistically significant. Similar improvements were seen in sleep architecture with increased rapid eye movement (REM) and stage 3 sleep. Conclusions: The incidence of OSA in Asians undergoing bariatric surgery is high. Routine sleep studies in Asian patients are justified. Weight loss brought about a significant improvement in AHI and continuous positive airway pressure requirements. LAGB placement should be considered a broadly effective therapy for sleep apnoea in the severely obese patient.

Clinical manifestations and consequences of obstructive sleep apnea

Obstructive sleep apnea is a common respiratory disorder that is underdiagnosed and associated with a variety of adverse health and safety consequences. Treatment is effective in improving quality of life and reducing morbidity. This underscores the importance of considering the diagnosis in suitable patients, verifying the diagnosis, and initiating prompt, effective therapy. In this review, the risk factors, symptoms and signs, diagnosis, clinical consequences, and treatment of obstructive sleep apnea are discussed.

Aerobic and anaerobic exercise capacities in obstructive sleep apnea and associations with subcutaneous fat distributions

Obesity is a strong risk factor for the development and progression of sleep apnea. Responses to exercise by patients with obstructive sleep apnea syndrome (OSAS) are clinically relevant to reducing body weight and cardiovascular risk factors. This study aimed to clarify the aerobic and anaerobic exercise capacities and their possible relationships with other findings in patients with OSAS. Forty patients (30 males, 10 females) and 40 controls (30 males, 10 females) were enrolled in this study. Questionnaires (excessive daytime sleepiness, daytime tiredness, morning headache, waking unrefreshed, and imbalance), overnight polysomnography, indirect laryngoscopy, and aerobic and anaerobic exercise tests were performed. Triceps, subscapular, abdomen, and thigh skinfold thicknesses were measured. Subcutaneous abdominal fat (abdomen skinfold) was significantly higher in OSAS patients than in controls. Maximal anaerobic power and anaerobic capacity were not different significantly between the patients and controls. We found that aerobic capacity was significantly lower in OSAS patients than in controls. Aerobic capacity was negatively correlated with upper-body subcutaneous fat (triceps and subscapular skinfolds) but not correlated with subcutaneous abdominal fat in OSAS patients. In multivariate analyses using all patients, the apnea-hypopnea index remained a significant independent predictor of aerobic capacity after controlling for a variety of potential confounders including body mass index. Our data confirm that central obesity (subcutaneous abdominal fat) is prominent in patients with OSAS. Our results suggest that lower aerobic exercise capacity in patients with OSAS might be due to daily physical activity that is restricted by OSA itself. This study also suggests that the degree of subcutaneous abdominal fat cannot be used for predicting aerobic capacity level. We think that upper-body subcutaneous fat might be suitable for determining the physical fitness of patients with OSAS.

Lifestyle intervention with weight reduction: first-line treatment in mild obstructive sleep apnea

RATIONALE

Obesity is the most important risk factor for obstructive sleep apnea (OSA). However, although included in clinical guidelines, no randomized controlled studies have been performed on the effects of weight reduction on mild OSA.

OBJECTIVES

The aim of this prospective, randomized controlled parallel-group 1-year follow-up study was to determine whether a very low calorie diet (VLCD) with supervised lifestyle counseling could be an effective treatment for adults with mild OSA.

METHODS

Seventy-two consecutive overweight patients (body mass index, 28-40) with mild OSA were recruited. The intervention group (n = 35) completed the VLCD program with supervised lifestyle modification, and the control group (n = 37) received routine lifestyle counseling. The apnea-hypopnea index (AHI) was the main objectively measured outcome variable. Change in symptoms and the 15D-Quality of Life tool were used as subjective measurements.

MEASUREMENTS AND MAIN RESULTS

The lifestyle intervention was found to effectively reduce body weight (-10.7 +/- 6.5 kg; body mass index, -3.5 +/- 2.1 [mean +/- SD]). There was a statistically significant difference in the mean change in AHI between the study groups (P = 0.017). The adjusted odds ratio for having mild OSA was markedly lowered (odds ratio, 0.24 [95% confidence interval, 0.08-0.72]; P = 0.011) in the intervention group. All common symptoms related to OSA, and some features of 15D-Quality of Life improved after the lifestyle intervention. Changes in AHI were strongly associated with changes in weight and waist circumference.

CONCLUSIONS

VLCD combined with active lifestyle counseling resulting in marked weight reduction is a feasible and effective treatment for the majority of patients with mild OSA, and the achieved beneficial outcomes are maintained at 1-year follow-up.

Effect of weight reduction on rhinometric measurements in overweight patients with obstructive sleep apnea

BACKGROUND

Elevated nasal resistance and obesity predispose to obstructive sleep apnea (OSA). Weight loss has been shown to result in an alleviation of OSA, but its effect on nasal airflow has not been studied.

METHODS

This study was a prospective, randomized, controlled study with two parallel groups. A total of 52 adult overweight patients (body mass index [BMI], 28-40 kg/m2) with mild obstructive sleep apnea (apnea-hypopnea index (AHI), 5-15) were randomized into two study groups. The intervention group (n = 26) followed a very low calorie diet with a supervised lifestyle intervention while the control group (n = 26) received routine lifestyle counseling. The changes in BMI, total nasal resistance, total nasal volume, and quality of life scores (Mini Rhinoconjunctivitis Quality of Life Questionnaire, MiniRQLQ) were assessed at baseline and after the intervention at 3 months.

RESULTS

The reduction in BMI in the intervention group was significantly greater than that achieved by patients in the control group (5.4 kg/m2 versus 0.5 kg/m2). Accordingly, AHI was reduced by 3.2 events/hour in the intervention group and by 1.3 in the control group. However, there were no significant changes in rhinometric measurements despite significant weight loss. There was no correlation between the reduction of BMI and the change in nasal resistance or MiniRQLQ scores.

CONCLUSION

Weight reduction does not seem to have any effect on nasal resistance or volume in overweight patients with mild OSA. Patients with OSA and impaired nasal breathing need specific medical or surgical treatment to restore nasal airflow.

Effect of physical activity on heart rate variability in normal weight, overweight and obese subjects: results from the SAPALDIA study

Many studies have demonstrated an association of both a sedentary lifestyle and a high body mass index (BMI) with greater risk for cardiovascular disease. Within the prospective SAPALDIA cohort (Swiss cohort Study on Air Pollution and Lung Diseases in Adults), we investigated whether regular exercise was protective against reduced heart rate variability (HRV), a clinically relevant predictor of cardiovascular morbidity and mortality, and whether adverse effects of obesity and weight gain on HRV were modified by regular exercise. Twenty-four-hour electrocardiograms were recorded in 1,712 randomly selected SAPALDIA participants aged >or=50, for whom BMI was assessed in the years 1991 and 2001-2003. Other examinations included an interview investigating health status (especially respiratory and cardiovascular health and health relevant behaviours including physical activity) and measurements of blood pressure, body height and weight. The association between regular physical activity and HRV and interactions with BMI and BMI change was assessed in multivariable linear regression analyses. Compared to sedentary obese subjects, SDNN (standard deviation of all RR intervals) was 14% (95% CI: 8-20%) higher in sedentary normal weight subjects; 19% (CI: 12-27%) higher in normal weight subjects exercising regularly >or=2 h/week; and 19% (CI: 11-28%) higher in obese subjects exercising regularly >or=2 h/week. Compared with sedentary subjects who gained weight, those who gained weight but did exercise regularly had a 13% higher SDNN (CI: 7-20%). Regular physical exercise has strong beneficial effects on cardiac autonomic nervous function and thus appears to offset the negative effect of obesity on HRV.

Sleep-disordered breathing is related to an increased risk for type 2 diabetes in middle-aged men, but not in women--the FIN-D2D survey

AIM

To determine the association between sleep-disordered breathing (SDB) and obesity, diabetes and glucose intolerance among middle-aged men and women in Finland.

METHODS

A multicentre, population-based, cross-sectional survey in Finland. A total of 1396 men and 1500 women aged 45-74 years participated in the survey between 2004 and 2005. The study subjects underwent a health examination including an oral glucose tolerance test and filled a questionnaire describing their sleep habits.

RESULTS

Middle-aged men with SDB had an increased prevalence of diabetes and abnormal glucose tolerance. These associations were not found among middle-aged women. After adjustments for age, body mass index, smoking and central nervous system-affecting medication, SDB was independently associated with diabetes and glucose intolerance in men, but not in women.

CONCLUSION

Middle-aged men with SDB have an independent risk of type 2 diabetes. However, both diabetes and SDB exhibit a strong association with obesity and especially with central obesity, reflecting increased visceral fat. In clinical practice especially male patients with diabetes should always be asked about habitual snoring and about possible sleep apnoea.

The link between cardiac autonomic activity and sleep delta power is altered in men with sleep apnea-hypopnea syndrome

We hypothesize that sleep apnea-hypopnea alters interaction between cardiac vagal modulation and sleep delta EEG. Sleep apnea-hypopnea syndrome (SAHS) is related to cardiovascular complications in men. SAHS patients show higher sympathetic activity than normal subjects. In healthy men, non-rapid eye movement (NREM) sleep is associated with cardiac vagal influence, whereas rapid eye movement (REM) sleep is linked to cardiac sympathetic activity. Interaction between cardiac autonomic modulation and delta sleep EEG is not altered across a life span nor is the delay between appearances of modifications in both signals. Healthy controls, moderate SAHS, and severe SAHS patients were compared across the first three NREM-REM cycles. Spectral analysis was applied to ECG and EEG signals. High frequency (HF) and low frequency (LF) of heart rate variability (HRV), ratio of LF/HF, and normalized (nu) delta power were obtained. A coherency analysis between HFnu and delta was performed, as well as a correlation analysis between obstructive apnea index (AI) or hypopnea index (HI) and gain, coherence, or phase shift. HRV components were similar between groups. In each group, HFnu was larger during NREM, while LFnu predominated across REM and wake stages. Coherence and gain between HFnu and delta decreased from controls to severe SAHS patients. In SAHS patients, the delay between modifications in HFnu and delta did not differ from zero. AI and HI correlated negatively with coherence, while HI correlated negatively with gain only. Apneas-hypopneas affect the link between cardiac sympathetic and vagal modulation and delta EEG demonstrated by the loss of cardiac autonomic activity fluctuations across shifts in sleep stages. Obstructive apneas and hypopneas alter the interaction between both signals differently.

Assessment of continuous positive airway pressure treatment in obstructive sleep apnea syndrome using 24-hour urinary catecholamines

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is related to diurnal sympathetic hyperactivity and increased blood pressure, both factors that are likely to lead to the development of cardiovascular disease.

HYPOTHESIS

The study investigated whether 24-h urinary catecholamines would reflect the effect of obstructive sleep apnea on autonomic activity.

METHODS

Standard polysomnography was performed in 17 patients with OSAS (age 53.7 +/- 13.5 years, mean +/- standard deviation). The number of apnea/hypopnea episodes per hour of sleep (apnea/hypopnea index [AHI]); number of oxygen desaturation episodes per hour (desaturation index [DSI]); arousals per hour (arousal index); lowest oxygen saturation (lowest SpO2); and percentages of stages 1, 2, 3/4, and rapid eye movement sleep (% stage 1, -2, and -3/4, and % REM, respectively) were measured. Overnight continuous positive airway pressure (CPAP) titration was performed the night after the baseline sleep measurements had been taken. Twenty-four-hour urinary adrenaline and noradrenaline were also examined.

RESULTS

During the CPAP treatment, both 24-h urinary adrenaline and noradrenaline were significantly lower compared with natural sleep. Continuous positive airway pressure significantly decreased the AHI, DSI, % stage 1, and arousal index and significantly increased the lowest SpO2. There were no significant differences in % stage 2, % stage 3/4, and % REM between before and during CPAP treatment. Multiple analysis of covariance tests revealed that lowest SpO2 was the most important factor for increasing 24-h urinary noradrenaline levels (F = 4.75, p = 0.048).

CONCLUSIONS

One night CPAP treatment could improve autonomic dysfunction. The assessment of 24-h urinary noradrenaline would provide important information for evaluating the effect of CPAP treatment.

Polysomnography before and after weight loss in obese patients with severe sleep apnea

OBJECTIVE

While obstructive sleep apnea (OSA) is strongly related to obesity, few studies have examined polysomnographic (PSG) changes with major weight loss. We examined the effect of weight loss following laparoscopic adjustable gastric banding (LAGB) on the PSG changes in patients with severe OSA. In addition, we studied daytime sleepiness, the metabolic syndrome and quality of life (QOL).

METHODS

A prospective study was conducted of 25 severely obese patients (17 men, eight women) with paired diagnostic PSG, biochemical and questionnaire studies, the first prior to LAGB and the second at least 1 y later. Subjects with a baseline apnea-hypopnea index (AHI) >25/h were included.

RESULTS

Subject baseline age was 44.7 y, weight 154 kg and body mass index 52.7 kg/m(2). The second PSG study was conducted 17.7+/-10 (range 12-42) months after surgery and mean percentage of excess loss and weight loss were 50.1+/-15% (range 24-80%) and 44.9+/-22 kg (range 18-103 kg), respectively. There was a significant fall in AHI from 61.6+/-34 to 13.4+/-13, improved sleep architecture with increased REM and stage III and IV sleep, daytime sleepiness, as measured by Epworth Sleepiness Scale, of 13+/-7.0 to 3.8+/-3.0, and fewer patients requiring nasal continuous positive airways pressure (CPAP). There were also major improvements in the metabolic syndrome, QOL, body image and fewer symptoms of depression (P<0.05 for all).

CONCLUSION

Weight loss provides major improvement or resolution of OSA and CPAP requirements. It also reduces daytime sleepiness, and improves the metabolic syndrome and QOL. LAGB placement should be considered a broadly effective therapy for sleep apnea in the severely obese patient.

Demographics and diagnosis of obstructive sleep apnea

This article reviews the terminology of obstructive sleep apnea and the associated diagnostic tests and provides an overview of the risk factors for this chronic condition. Sleep apnea affects 2% to 4% of middle-aged working adults in the general population, however, a considerable number of affected individuals remain undiagnosed. Patients with the disease may be at a higher risk for adverse perioperative outcomes. Knowledge of factors associated with an increased risk of obstructive sleep apnea is vital to the perioperative assessment and anesthetic plan.

Obesity and obstructive sleep apnea

There is a very high prevalence of OSA in obese individuals and a high prevalence of obesity in patients with OSA. The pathophysiology of OSA is intimately linked to obesity. Anatomic and functional considerations of the pharyngeal airway, the CNS, central obesity, and leptin likely interact in the development of OSA in obese individuals. OSA may itself predispose individuals to worsening obesity because of sleep deprivation, daytime somnolence, and disrupted metabolism. The diagnosis of OSA requires the clinician's awareness of its potential to cause a spectrum of acute and chronic neurocognitive, psychiatric, and nonspecific symptoms in patients who may be unaware that their sleep is disturbed. Symptoms and examination findings help predict which obese individuals have OSA, and polysomnography is the gold standard by which to make the diagnosis and assess the effects of treatment. Numerous disease states are associated with both OSA and obesity, and it is becoming clear that the relationships are mediated by complex interrelated mechanisms. Common diseases and disease mechanisms in OSA and obesity suggest that conditions related to obesity may be better managed if patients, particularly those who are morbidly obese, are evaluated and treated for previously undiagnosed OSA. OSA is cured in only specific cases with craniofacial or upper airway surgery, and the general application of UVP is not efficacious. OSA also can be cured with sufficient lifestyle-mediated or surgical weight loss; however, in the absence of long-term weight maintenance, OSA returns with weight gain. Although not curative, nasal CPAP is the initial treatment of choice for most patients because of its noninvasive approach and technical efficacy. It is limited, however, by patient acceptance and long-term compliance. Advances in mask comfort and use of humidified air should increase its acceptance. Future management strategies include newer generations of positive airway devices that automatically titrate pressures (which are not yet recommended by expert organizations) and multidisciplinary approaches to managing the care of patients with OSA.

Health-related quality of life in obese outpatients losing weight with very-low-energy diet and behaviour modification--a 2-y follow-up study

OBJECTIVE

To study health-related quality of life (HRQL) in a clinically selected sample of obese outpatients.

DESIGN

A single-strand before and after study with 2-y follow-up after treatment comprising 10 weeks on very-low-energy diet (VLED) and 4 months of behaviour modification in groups.

SUBJECTS

A total of 126 (mean (s.d.) age 48.2 (11.1) y and body mass index 42.8 (6.2) kg/m(2) obese patients (63% women) referred for treatment in an obesity clinic.

MEASUREMENTS

Weight and HRQL using questionnaires (RAND 36-Item Health Survey 1.0 and Obesity-related Psychosocial problems scale (OP-scale)).

RESULTS

A total of 100 patients (61% women) completed the treatment and 67 (71% women) completed the 2-y follow-up. The mean (s.d.) weight loss was 12.5 (5.6)% at the end of group therapy, 6.0 (7.1)% at 1 y, and 2.6 (7.5)% at 2 y. At baseline, the mean (s.d.) score for the OP-scale was 61.9 (24.6). The mean scores on every RAND-36 scale were markedly lower than in the Finns without chronic conditions. All the scales in HRQL improved markedly during the treatment. During the follow-up, all the scales started to return towards baseline levels, and at 2 y only obesity-related psychosocial problems and physical functioning were still improved relative to baseline. In categories of weight change at 2 y (>or=10% weight loss, 0-9.9% weight loss, weight gain), obesity-related psychosocial functioning, physical functioning, and general health showed dose-response improvement with increasing weight loss. A >or=10% weight loss at 2 y after treatment was associated with clear improvement in obesity-related psychosocial problems, physical functioning, physical role functioning, bodily pain, general health, mental health, and vitality. A 0-9.9% weight loss was associated with improvement in obesity-related psychosocial problems and physical functioning. Weight gain was associated with improvement in obesity-related psychosocial problems and social functioning. The study population was too small to examine possible gender differences.

CONCLUSIONS

Treatment with VLED and behaviour modification produces marked short-term weight loss and clear improvement in all aspects of HRQL. At 2 y after treatment, the average maintained weight loss is modest. However, 1/3 of patients maintained a >or=5% weight loss. Improvement in obesity-related psychosocial problems and physical functioning is associated even with less than 10% of maintained weight loss. Since the pattern of HRQL changes only partly followed the pattern of weight change as expected, other factors, such as the therapeutic effect of participating in the weight loss programme or increase in physical activity, may affect HRQL responses.

Health-related quality of life in obese outpatients losing weight with very-low-energy diet and behaviour modification: a 2-y follow-up study

OBJECTIVE

To study health-related quality of life (HRQL) in a clinically selected sample obese outpatients.

DESIGN

A single-strand before and after study with 2-y follow-up after treatment comprising 10 weeks on very-low-energy diet (VLED) and 4 months of behaviour modification in groups.

SUBJECTS

A total of 126 patients (mean (s.d.) age 48.2 (11.1) y and body mass index (BMI) 42.8 (6.2) kg/m(2) (63% women)) referred for treatment in an obesity clinic.

MEASUREMENTS

Weight and HRQL using questionnaires (RAND 36-Item Health Survey 1.0 and Obesity-related Psychosocial problems-scale).

RESULTS

In all, 100 patients (61% women) completed the treatment and 67 (71% women) completed the 2-y follow-up. The mean (s.d.) weight loss was 12.5 (5.6)% at the end of group therapy, 6.0 (7.1)% at 1 y, and 2.6 (7.5)% at 2 y. At baseline, the mean (s.d.) score for OP-scale was 61.9 (24.6). The mean scores on every RAND-36 scale were markedly lower than in the Finns without chronic conditions. All the scales in HRQL improved markedly during the treatment. During the follow-up, all the scales started to return back towards baseline levels and at 2 y, only obesity-related psychosocial problems and physical functioning were still improved relative to baseline. In categories of weight change at 2 y (> or =10% weight loss, 0-9.9% weight loss, weight gain), obesity-related psychosocial functioning, physical functioning, and general health showed dose-response improvement with increasing weight loss. A > or =10% weight loss at 2 y after treatment was associated with clear improvement in obesity-related psychosocial problems, physical functioning, physical role functioning, bodily pain, general health, mental health, and vitality. A 0-9.9% weight loss was associated with improvement in obesity-related psychosocial problems and physical functioning. Weight gain was associated with improvement in obesity-related psychosocial problems and social functioning. The study population was too small to examine possible gender differences.

CONCLUSIONS

Treatment with VLED and behaviour modification produces marked short-term weight loss and clear improvement in all aspects of HRQL. At 2 y after treatment, the average maintained weight loss is modest. However, one-third of patients maintain > or =5% weight loss. Improvement in obesity-related psychosocial problems and physical functioning is associated even with &<10% of maintained weight loss. Since the pattern of HRQL changes did only partly follow the pattern of weight change as expected, other factors, such as the therapeutic effect of participating in the weight loss programme or increase in physical activity, may affect HRQL responses.

Behavioral and pharmacologic therapy of obstructive sleep apnea

Previous attempts at using pharmacologic agents in the treatment of OSA have been disappointing. Medroxyprogesterone has not been found to be useful in the treatment of OSA. Use of protriptyline is limited by frequent side effects, but its role in mild and REM-related OSA must be clarified. SSRIs seem to be ineffective in treatment of severe OSA. Further studies are needed to determine their effect in persons with mild disease. This is important because patients with mild OSA (AHI < 15 hours) are most likely to be noncompliant with CPAP therapy [91]. A recent systematic review of drug treatments for OSA concluded that the current data do not support the use of any drug as an alternative to CPAP [92]. Of 56 studies identified, only 9 studies met methodologic criteria. Clearly, basic research and adequately powered clinical trials are needed to identify an effective medication for OSA.