Influence of treatment on leptin levels in patients with obstructive sleep apnoea

Association of Short Sleep Duration and Obstructive Sleep Apnea with Central Obesity: A Retrospective Study Utilizing Anthropometric Measures

Background

Central obesity, as measured by examination instruments, has been shown to be associated with both OSA and short sleep duration. However, objective measurement tools like CT, MRI, and DXA are expensive, cause radiation exposure, and have limited availability, especially in resource-limited settings. Thus, this study aimed to demonstrate the relevance of Body Mass Index (BMI) and Waist-to-Height Ratio (WHtR) as surrogate indicators of visceral obesity in the assessment of OSA and short sleep duration. We also intend to evaluate whether WHtR, in combination with BMI, can be a suitable surrogate marker for visceral adiposity.

Methods

We recruited 333 adults with complete polysomnographic (PSG) records retrospectively. Logistic regression helped to assess the association of BMI and WHtR as surrogates for central adiposity with OSA and short sleep duration. Moreover, ROC curve analysis was conducted to evaluate the predictive ability of BMI and WHtR.

Results

Following the relevant adjustments, logistic regression analysis results showed that the combination of WHtR and BMI acting as central obesity surrogates was significantly associated with OSA and short sleep duration (p<0.05). According to univariate regression analysis, sleep latency and wake after sleep onset were independent predictors of the risk of central obesity in patients with short sleep duration and OSA. Additionally, ROC curve analysis demonstrated that the combination of BMI and WHtR provided a better assessment of central adiposity in patients with OSA and short sleep duration, compared to each measure alone.

Conclusion

BMI and WHtR are significantly associated with OSA and short sleep duration, and might serve as a potential surrogate marker for central obesity. Sleep latency and wake after sleep onset can independently predict the risk of central obesity in patients with short sleep time and OSA. Thus, larger prospective studies are needed to verify our findings.

Smoking Disturbs the Beneficial Effects of Continuous Positive Airway Pressure Therapy on Leptin Level in Obstructive Sleep Apnea

Background

This study aimed to determine how smoking alters the effect of positive airway pressure (PAP) therapy on metabolic syndrome in obstructive sleep apnea (OSA).

Methods

In this clinical trial, morphometric measures, metabolic syndrome parameters, and apnea-hypopnea index (AHI) in OSA patients were recorded and compared between active smokers and non-smokers. The mean change in metabolic syndrome parameters measured before and after 3 months of PAP therapy was determined. The study included 72 males and 43 females.

Results

Morphometric values and mean AHI did not differ between active smokers and non-smokers. When the percentage of unchanged, increased, or decreased metabolic parameters measured before and after treatment was analyzed, leptin level tended to increase in active smokers with OSA after PAP therapy compared with non-smokers (P=0.034, adjusted for confounders).

Conclusion

Serum leptin level was stable or decreased in non-smokers, while 40% of active smokers had increased leptin level. Therefore, smoking plays a predisposing role in leptin resistance despite PAP therapy in OSA patients.

Understanding the Association Between Obesity and Obstructive Sleep Apnea Syndrome: A Case-Control Study

Introduction Obstructive sleep apnea (OSA) represents a sleep-related impairment linked to upper airway function. The question of whether OSA drives obesity or if shared underlying factors contribute to both conditions remains unresolved. Hence, this present study aims to understand the interplay between obstructive sleep apnea syndrome (OSAS) and obesity through in-depth analysis of anthropometric data within control subjects and OSA patients. Methodology A case-control study was conducted, which included 40 cases and 40 matched healthy controls. Study participants with reported symptoms of snoring, daytime drowsiness, or both were included in the study. All the study participants underwent comprehensive anthropometric assessments such as height, weight, body mass index (BMI), neck circumference, waist circumference, hip circumference, waist-to-hip ratio, skin-fold thickness, and thickness measurements of biceps, triceps, suprailiac, and subscapular muscles. Results Within the OSA group, significant disparities emerged in mean age, waist circumference, waist-to-hip ratio, and diverse fat accumulations encompassing visceral, subcutaneous, trunk, and subcutaneous leg fat. Notably, skin-fold thickness at specific sites - biceps, triceps, subscapula, and suprailiac - demonstrated considerable augmentation relative to the control group. Furthermore, mean values associated with height, weight, BMI, neck circumference, fat percentage, subcutaneous arm fat, entire arm composition, and trunk skeletal muscle either equaled or exceeded those in the control group. However, statistical significance was not attained in these comparisons. Conclusion This investigation underscored a pronounced correlation between numerous endpoints characterizing OSA patients and markers of obesity. Consequently, addressing altered levels of obesity-linked anthropometric variables through pharmacological interventions might hold promise as a pivotal strategy for improving symptoms associated with OSA.

Gender Differences in the Context of Obstructive Sleep Apnea and Metabolic Diseases

The relationship between obstructive sleep apnea (OSA) and endocrine and metabolic disease is unequivocal. OSA, which is characterized by intermittent hypoxia and sleep fragmentation, leads to and exacerbates obesity, metabolic syndrome, and type 2 diabetes (T2D) as well as endocrine disturbances, such as hypothyroidism and Cushing syndrome, among others. However, this relationship is bidirectional with endocrine and metabolic diseases being considered major risk factors for the development of OSA. For example, polycystic ovary syndrome (PCOS), one of the most common endocrine disorders in women of reproductive age, is significantly associated with OSA in adult patients. Several factors have been postulated to contribute to or be critical in the genesis of dysmetabolic states in OSA including the increase in sympathetic activation, the deregulation of the hypothalamus-pituitary axis, the generation of reactive oxygen species (ROS), insulin resistance, alteration in adipokines levels, and inflammation of the adipose tissue. However, probably the alterations in the hypothalamus-pituitary axis and the altered secretion of hormones from the peripheral endocrine glands could play a major role in the gender differences in the link between OSA-dysmetabolism. In fact, normal sleep is also different between men and women due to the physiologic differences between genders, with sex hormones such as progesterone, androgens, and estrogens, being also connected with breathing pathologies. Moreover, it is very well known that OSA is more prevalent among men than women, however the prevalence in women increases after menopause. At the same time, the step-rise in obesity and its comorbidities goes along with mounting evidence of clinically important sex and gender differences. Metabolic and cardiovascular diseases, seen as a men's illness for decades, presently are more common in women than in men and obesity has a higher association with insulin-resistance-related risk factors in women than in men. In this way, in the present manuscript, we will review the major findings on the overall mechanisms that connect OSA and dysmetabolism giving special attention to the specific regulation of this relationship in each gender. We will also detail the gender-specific effects of hormone replacement therapies on metabolic control and sleep apnea.

Exploring the Mediators that Promote Carotid Body Dysfunction in Type 2 Diabetes and Obesity Related Syndromes

Carotid bodies (CBs) are peripheral chemoreceptors that sense changes in blood O₂, CO₂, and pH levels. Apart from ventilatory control, these organs are deeply involved in the homeostatic regulation of carbohydrates and lipid metabolism and inflammation. It has been described that CB dysfunction is involved in the genesis of metabolic diseases and that CB overactivation is present in animal models of metabolic disease and in prediabetes patients. Additionally, resection of the CB-sensitive nerve, the carotid sinus nerve (CSN), or CB ablation in animals prevents and reverses diet-induced insulin resistance and glucose intolerance as well as sympathoadrenal overactivity, meaning that the beneficial effects of decreasing CB activity on glucose homeostasis are modulated by target-related efferent sympathetic nerves, through a reflex initiated in the CBs. In agreement with our pre-clinical data, hyperbaric oxygen therapy, which reduces CB activity, improves glucose homeostasis in type 2 diabetes patients. Insulin, leptin, and pro-inflammatory cytokines activate the CB. In this manuscript, we review in a concise manner the putative pathways linking CB chemoreceptor deregulation with the pathogenesis of metabolic diseases and discuss and present new data that highlight the roles of hyperinsulinemia, hyperleptinemia, and chronic inflammation as major factors contributing to CB dysfunction in metabolic disorders.

Leptin: Master Regulator of Biological Functions that Affects Breathing

Obesity is a global epidemic in developed countries accounting for many of the metabolic and cardiorespiratory morbidities that occur in adults. These morbidities include type 2 diabetes, sleep-disordered breathing (SDB), obstructive sleep apnea, chronic intermittent hypoxia, and hypertension. Leptin, produced by adipocytes, is a master regulator of metabolism and of many other biological functions including central and peripheral circuits that control breathing. By binding to receptors on cells and neurons in the brainstem, hypothalamus, and carotid body, leptin links energy and metabolism to breathing. In this comprehensive article, we review the central and peripheral locations of leptin's actions that affect cardiorespiratory responses during health and disease, with a particular focus on obesity, SDB, and its effects during early development. Obesity-induced hyperleptinemia is associated with centrally mediated hypoventilation with decrease CO₂ sensitivity. On the other hand, hyperleptinemia augments peripheral chemoreflexes to hypoxia and induces sympathoexcitation. Thus, "leptin resistance" in obesity is relative. We delineate the circuits responsible for these divergent effects, including signaling pathways. We review the unique effects of leptin during development on organogenesis, feeding behavior, and cardiorespiratory responses, and how undernutrition and overnutrition during critical periods of development can lead to cardiorespiratory comorbidities in adulthood. We conclude with suggestions for future directions to improve our understanding of leptin dysregulation and associated clinical diseases and possible therapeutic targets. Lastly, we briefly discuss the yin and the yang, specifically the contribution of relative adiponectin deficiency in adults with hyperleptinemia to the development of metabolic and cardiovascular disease. © 2020 American Physiological Society. Compr Physiol 10:1047-1083, 2020.

Impact of CPAP treatment on leptin and adiponectin in adults with coronary artery disease and nonsleepy obstructive sleep apnoea in the RICCADSA trial

BACKGROUND

Increased leptin and decreased adiponectin levels are reported in coronary artery disease (CAD) as well as in obstructive sleep apnoea (OSA). Less is known regarding the impact of continuous positive airway pressure (CPAP) on these biomarkers. We aimed to determine variables associated with leptin and adiponectin in adults with CAD and nonsleepy OSA, and evaluate the effect of CPAP adjusted for confounding factors.

METHODS

This was one of the secondary outcomes of the RICCADSA trial, conducted in Sweden between 2005 and 2013. From 244 revascularized CAD and OSA patients (apnoea-hypopnoea index >15/h) without excessive daytime sleepiness (Epworth Sleepiness Scale score <10), 196 with blood samples at baseline, after 3, and 12 months were included in the randomized controlled trial arm; of those, 98 were allocated to auto-titrating CPAP, and 98 to no-CPAP.

RESULTS

No significant changes in leptin and adiponectin levels were observed during follow-up, whereas Body-Mass-Index and waist circumference increased in both CPAP and no-CPAP groups with no significant between-group differences. Alterations in plasma leptin were determined by changes in waist circumference (beta coefficient 2.47; 95% confidence interval 0.77-4.40), whereas none of the analyzed parameters was predictive for changes in adiponectin levels. No association was found with CPAP adherence.

CONCLUSIONS

CPAP had no significant effect on leptin and adiponectin in this cohort of nonsleepy OSA patients. An increase in waist circumference predicted an increase in plasma levels of leptin after 12 months, suggesting that lifestyle modifications should be given priority in adults with CAD and OSA regardless of CPAP treatment.

Gender-specific change in leptin concentrations during long-term CPAP therapy

Purpose

Nasal continuous positive airway pressure (CPAP) alleviates sleepiness in patients with obstructive sleep apnoea syndrome (OSAS), but part of OSAS patients keep gaining weight. Leptin and insulin-like growth factor-1 (IGF-1) interact with energy balance, and CPAP therapy has been suggested to influence these endocrine factors. We hypothesised that leptin would decrease during long-term CPAP therapy, and weight gain would associate with OSAS severity, lower CPAP adherence, lower IGF-1, and leptin concentrations.

Methods

Consecutive patients (n = 223) referred to sleep study with suspected OSAS were enrolled. Patients underwent cardiorespiratory polygraphy at baseline. Questionnaires were completed, and blood samples were drawn both at baseline and after 3 years. A total of 149 (67%; M 65, F 84) patients completed the follow-up. Plasma samples were available from 114 patients, 109 of which with CPAP adherence data (49 CPAP users, 60 non-users).

Results

At baseline, the CPAP users were more obese and had more severe OSAS than the non-users. Leptin concentrations did not differ. After follow-up, leptin concentrations were higher in CPAP users (30.2 ng/ml vs. 16.8 ng/ml; p = 0.001). In regression analysis, increase in leptin concentrations was independent of age, baseline body mass index (BMI), or the change in BMI. Leptin concentrations increased among females (− 8.9 vs. 12.7 ng/ml; p < 0.001); whereas in men, CPAP did not have an effect, if not opposed the natural decrease in leptin observed in men not using CPAP. Change in IGF-1 levels did not differ.

Conclusions

Our results suggest increase in leptin concentrations during long-term CPAP therapy among females.

Electronic supplementary material

The online version of this article (10.1007/s11325-019-01846-y) contains supplementary material, which is available to authorized users.

Role of Leptin in Obstructive Sleep Apnea

Leptin is a peptide hormone produced mainly in white adipose tissue. It is known to regulate energy homeostasis, inflammation, metabolism, and sympathetic nerve activity. Increasing evidence suggests it has a role in ventilatory function and upper airway obstruction. Leptin levels correlate positively with measurements of adiposity and can potentially provide important insights into the pathophysiology of diseases associated with obesity. Obesity is a strong risk factor for obstructive sleep apnea, a disease characterized by periodic upper airway occlusion during sleep. The neuromuscular activity that maintains upper airway patency during sleep and the anatomy of upper airway are key factors involved in its pathogenesis. Experimental studies using animal models of a low leptin state such as leptin deficiency have shown that leptin regulates sleep architecture, upper airway patency, ventilatory function, and hypercapnic ventilatory response. However, findings from human studies do not consistently support the data from the animal models. The effect of leptin on the pathophysiology of obstructive sleep apnea is being investigated, but the results of studies have been confounded by leptin's diurnal variation and the short-term effects of feeding, adiposity, age, and sex. Improved study design and methods of assessing functional leptin levels, specifically their central versus peripheral effects, will improve understanding of the role of leptin in sleep apnea.

High fat diet blunts the effects of leptin on ventilation and on carotid body activity

KEY POINTS

Leptin plays a role in the control of breathing, acting mainly on central nervous system; however, leptin receptors have been recently shown to be expressed in the carotid body (CB), and this finding suggests a physiological role for leptin in the regulation of CB function. Leptin increases minute ventilation in both basal and hypoxic conditions in rats. It increases the frequency of carotid sinus nerve discharge in basal conditions, as well as the release of adenosine from the CB. However, in a metabolic syndrome animal model, the effects of leptin in ventilatory control, carotid sinus nerve activity and adenosine release by the CB are blunted. Although leptin may be involved in triggering CB overactivation in initial stages of obesity and dysmetabolism, resistance to leptin signalling and blunting of responses develops in metabolic syndrome animal models.

ABSTRACT

Leptin plays a role in the control of breathing, acting mainly on central nervous system structures. Leptin receptors are expressed in the carotid body (CB) and this finding has been associated with a putative physiological role of leptin in the regulation of CB function. Since, the CBs are implicated in energy metabolism, here we tested the effects of different concentrations of leptin administration on ventilatory parameters and on carotid sinus nerve (CSN) activity in control and high-fat (HF) diet fed rats, in order to clarify the role of leptin in ventilation control in metabolic disease states. We also investigated the expression of leptin receptors and the neurotransmitters involved in leptin signalling in the CBs. We found that in non-disease conditions, leptin increases minute ventilation in both basal and hypoxic conditions. However, in the HF model, the effect of leptin in ventilatory control is blunted. We also observed that HF rats display an increased frequency of CSN discharge in basal conditions that is not altered by leptin, in contrast to what is observed in control animals. Leptin did not modify intracellular Ca²⁺ in CB chemoreceptor cells, but it produced an increase in the release of adenosine from the whole CB. We conclude that CBs represent an important target for leptin signalling, not only to coordinate peripheral ventilatory chemoreflexive drive, but probably also to modulate metabolic variables. We also concluded that leptin signalling is mediated by adenosine release and that HF diets blunt leptin responses in the CB, compromising ventilatory adaptation.

High-intensity interval training improves obstructive sleep apnoea

Background

Three hours per week of vigorous physical activity is found to be associated with reduced odds of sleep-disordered breathing.

Aim

To investigate whether 12 weeks of high-intensity interval training (HIIT) reduced the apnoea–hypopnea index (AHI) in obese subjects with moderate-to-severe obstructive sleep apnoea.

Methods

In a prospective randomised controlled exercise study, 30 (body mass index 37±6 kg/m², age 51±9 years) patients with sleep apnoea (AHI 41.5±25.3 events/hour) were randomised 1:1 to control or 12 weeks of supervised HIIT (4×4 min of treadmill running or walking at 90%–95% of maximal heart rate two times per week).

Results

In the HIIT group, the AHI was reduced by 7.5±11.6 events/hour (within-group p<0.05), self-reported sleepiness (Epworth scale) improved from 10.0±3.6 to 7.3±3.7 (between-group p<0.05) and maximal oxygen uptake improved from 28.2±7.4 to 30.2±7.7 mL/kg/min (between-group p<0.05) from baseline to 12 weeks. The AHI, self-reported sleepiness and VO_2maxwere unchanged from baseline to 12 weeks in controls (baseline AHI 50.3±25.5 events/hour, Epworth score 5.9±4.3, maximal oxygen uptake 27.0±6.8 mL/kg/min). Body weight remained unchanged in both groups.

Conclusion

Twelve weeks of HIIT improved the AHI and self-reported daytime sleepiness in subjects with obese sleep apnoea without any change in the desaturation index and body weight.

Obstructive Sleep Apnea, Daytime Sleepiness, and Type 2 Diabetes

PURPOSE

The purpose of this article is to review the literature on obstructive sleep apnea, resultant daytime sleepiness, and type 2 diabetes mellitus, as the state of evidence exists.

METHODS

A search was conducted on Medline and CINAHL using the search terms sleep apnea syndromes, obstructive sleep apnea, disorders of excessive somnolence, type 2 diabetes mellitus, and insulin resistance. This review includes only published research studies in English, in adults aged 19 years or older. There were 109 citations when the terms were combined, 36 citations that were identified as research studies, no randomized clinical trials, and only 1 qualitative study.

RESULTS

Obstructive sleep apnea and type 2 diabetes share the risk factors of age and central abdominal obesity. Recent studies suggest that obstructive sleep apnea and type 2 diabetes not only frequently coexist but also have a bidirectional association wherein each condition exacerbates the other. The mechanism whereby obstructive sleep apnea affects glucose metabolism is likely repetitive hypoxia and sleep fragmentation, which cause a stress response with increased sympathetic nervous system activity, increased fatigue-causing cytokines, and altered leptin levels that result in weight gain. In addition, daytime sleepiness results in an impaired mood state that may impede diabetes management.

CONCLUSIONS

Type 2 diabetes is prevalent in persons with obstructive sleep apnea, although the direction of causality is unknown. More research, including randomized clinical trials, is needed to determine how obstructive sleep apnea and daytime sleepiness affect persons with type 2 diabetes.

Effects of continuous positive airway pressure on energy intake in obstructive sleep apnea: A pilot sham-controlled study

Obesity is among the leading risk factors for obstructive sleep apnea (OSA). A reciprocal relationship between obesity and OSA has been proposed, which may be due to excessive food intake. We conducted a pilot study to test the effects of continuous positive airway pressure (CPAP) on energy intake (EI) in OSA patients using a sham-controlled crossover design. In-laboratory total daily EI was assessed after 2mo of active and sham CPAP. Four men were enrolled (age±SEM: 51.8±2.1y; body mass index: 31.5±1.5kg/m²). All received active treatment first. Meals (breakfast, lunch, dinner, snack) were served in excess portions at fixed times and additional palatable snacks were freely available throughout the day. Total EI was lower after active (3744±511kcal/d) vs. sham (4030±456kcal/d) CPAP but this difference was not significant (p=0.51) due to variability in the free snack intake. When only fixed eating occasions were considered, daily EI was significantly lower in the active (3105±513kcal/d) vs. sham (3559±420kcal/d) condition (p=0.006). This small pilot and feasibility study is the first to utilize a sham-controlled design to investigate the effects of CPAP treatment on objective measures of EI. Findings suggest that CPAP may cause a reduction in fixed meal intake. In demonstrating feasibility of study methodology, our study also suggests a larger randomized sham-controlled trial be conducted to fully characterize the effects of CPAP treatment on EI and energy balance overall.

Effects of continuous positive airway pressure on energy balance regulation: a systematic review

Obesity is both a cause and a possible consequence of obstructive sleep apnoea (OSA), as OSA seems to affect parameters involved in energy balance regulation, including food intake, hormonal regulation of hunger/satiety, energy metabolism and physical activity. It is known that weight loss improves OSA, yet it remains unclear why continuous positive airway pressure (CPAP) often results in weight gain.The goal of this systematic review is to explore if and how CPAP affects the behaviour and/or metabolism involved in regulating energy balance.CPAP appears to correct for a hormonal profile characterised by abnormally high leptin and ghrelin levels in OSA, by reducing the circulating levels of each. This is expected to reduce excess food intake. However, reliable measures of food intake are lacking, and not yet sufficient to make conclusions. Although studies are limited and inconsistent, CPAP may alter energy metabolism, with reports of reductions in resting metabolic rate or sleeping metabolic rate. CPAP appears to not have an appreciable effect on altering physical activity levels. More work is needed to characterise how CPAP affects energy balance regulation.It is clear that promoting CPAP in conjunction with other weight loss approaches should be used to encourage optimal outcomes in OSA patients.

Sleep complaints and sleep breathing disorders in upper and lower obstructive lung diseases

Upper and lower obstructive lung diseases can induce sleep complaints and can be part of the pathogenesis of sleep breathing disorders. In fact, the physiological changes of the pattern of respiration during sleep, added to the airways disease can lead to symptomatic worsening of rhinitis, asthma and chronic obstructive pulmonary diseases (COPD); moreover, their functional and anatomical features can lead to sleep breathing disorders such as obstructive sleep apnea syndrome (OSAS). This review highlights the above-mentioned relationships and the effect of disease management on its comorbidities and the patient's quality of life. Rhinitis, asthma and COPD represent causes of sleep complaints that may be reduced with optimal management of these obstructive airways diseases. Continuous positive airway pressure (CPAP) treatment of sleep apnea needs to be tailored after optimization of the therapy of concomitant diseases, but it can often ameliorate comorbid disease.

The correlation of serum growth differentiation factor-15 level in patients with obstructive sleep apnea

PURPOSE

Growth differentiation factor-(GDF-) is a prognostic biomarker in cardiovascular disorders (CVD). GDF-15 level was not studied in patients with obstructive sleep apnea syndrome (OSAS) before. In this study, we investigated serum GDF-15 levels in OSAS patients and compared them with healthy controls.

MATERIAL AND METHODS

Polysomnographically, confirmed forty consecutive OSAS patients (20 men and 20 women) and forty consecutive healthy controls (23 men and 17 women) were enrolled in the study. The samples in each group had similar demographic characteristics and body mass index (BMI) values.

RESULTS

In the study, no significant correlation was found about GDF-15 levels of OSAS group and healthy controls. However, there was a significant statistical correlation between age and GDF-15 level. In correlation analysis, there was not any significant correlation between age and BMI.

CONCLUSION

Although various developing biomarkers have been studied in cardiovascular disorders, GDF-15 levels have attracted a widespread interest as predictors of cardiovascular risk. GDF-15 level has not been evaluated previously in patients with OSAS. A significant statistical correlation was found between age and GDF-15 level. To reveal close relation between OSAS and GDF-15, further studies are needed with combination of GDF-15 and other biomarkers in OSAS.

Obstructive sleep apnoea, insulin resistance and adipocytokines

Obstructive sleep apnoea (OSA) is associated with multiple cardiometabolic abnormalities. Obesity is considered a major risk factor for the development of OSA, and it is also an established risk factor for insulin resistance and other cardiometabolic disorders. The enigma remains whether OSA has any causal role in the adverse metabolic profile, independent of or beyond that due to obesity. Sleep apnoeas and hypopnoeas result directly in intermittent hypoxaemia and cerebral arousals, both of which may evoke a cascade of downstream biologic responses in various body tissues and cells. Adipose tissue is a major source of adipocytokines many of which play important roles in the regulation of various metabolic functions. It is hypothesized that OSA may, through its unique pathophysiology, affect metabolic function through modulation of production or action of adipocytokines. This review focuses on insulin resistance, glucose metabolism and relevant adipocytokines in the context of OSA.

Effect of continuous positive airway pressure on leptin levels in patients with obstructive sleep apnea: a meta-analysis

OBJECTIVES

Continuous positive airway pressure (CPAP) is an effective treatment for obstructive sleep apnea hypopnea syndrome (OSAHS), but previous studies assessing the effect of CPAP on leptin in patients with OSAHS yielded conflicting results. In this study, we conducted a meta-analysis to determine whether CPAP therapy could reduce serum leptin levels.

DATA SOURCES

Databases of PubMed, Elsevier, and SCI were thoroughly searched by 2 independent reviewers.

METHODS

RevMan (version 5.2) was used for data synthesis. Weighted mean difference (WMD) before and after CPAP therapy was calculated to estimate the effects of CPAP therapy.

RESULTS

A total of 11 studies involving 413 participants were included. Meta-analysis showed that the total WMD for leptin levels was 1.44 units (95% confidence interval: 1.11-1.77, P < .01) before and after CPAP therapy. Subgroup analysis exhibited that leptin was decreased within 3 days after the therapy, and it was further reduced within 1 to 3 months and beyond.

CONCLUSIONS

The results of our meta-analysis showed that CPAP could significantly reduce leptin levels in OSAHS patients without concomitant weight loss.

Obstructive sleep apnea and asthma

Symptoms of sleep-disordered breathing, especially obstructive sleep apnea syndrome (OSAS), are common in asthma patients and have been associated with asthma severity. It is known that asthma symptoms tend to be more severe at night and that asthma-related deaths are most likely to occur during the night or early morning. Nocturnal symptoms occur in 60-74% of asthma patients and are markers of inadequate control of the disease. Various pathophysiological mechanisms are related to the worsening of asthma symptoms, OSAS being one of the most important factors. In patients with asthma, OSAS should be investigated whenever there is inadequate control of symptoms of nocturnal asthma despite the treatment recommended by guidelines having been administered. There is evidence in the literature that the use of continuous positive airway pressure contributes to asthma control in asthma patients with obstructive sleep apnea and uncontrolled asthma.

Obstructive sleep apnea and atrial fibrillation: understanding the connection

There is a high incidence of atrial fibrillation (AF) in patients with obstructive sleep apnea (OSA). Whether this represents a causative relationship or is merely an association remains to be determined. This review describes the current understanding of pathophysiologic links supporting a causative relationship between OSA and AF. The management of AF with antiarrhythmics, cardioversion and ablation success depends on compliance with OSA treatment. OSA worsens every risk factor resulting in a higher stroke risk in AF patients. Strategies for early screening and compliance with OSA treatment are the need of the hour.

The correlation of serum levels of leptin, leptin receptor and NO x (NO 2 (-) and NO 3 (-)) in patients with obstructive sleep apnea syndrome

The aim of this study was to investigate the relations between nitric oxide (NO) and leptin levels in a cohort of untreated adult Obstructive sleep apnea syndrome (OSAS) patients. Between June 1, 2012, and January 1, 2013, we evaluated a total of 58 subjects including 36 OSAS patients and 22 healthy controls, both polysomnographically confirmed. Following the completion of polysomnographic evaluation, serum samples were taken at 08:00. Leptin, leptin receptor, NO2 (-) and NO3 (-) levels were analyzed by commercial ELISA kits. Data analysis was performed using the Statistical Package for the Social Sciences (SPSS) version 16.0 (SPSS Inc., Chicago, IL, USA). There was no statistically significant difference between the OSAS patients and control groups with relation to the demographic parameters and body mass index (p > 0.05). Significantly higher serum leptin and plasma NO levels were found in OSAS patients compared to the controls (p < 0.001). In this study, higher leptin levels which were positively correlated with NO levels in OSAS group may indicate a possible link with increased incidence of airway pathologies in these patients.

Association between continuous positive airway pressure and changes in serum leptin in patients with obstructive sleep apnoea: a meta-analysis

PURPOSE

The role of leptin in the development of obstructive sleep apnoea (OSA) has been identified. However, the effects of OSA treatment using continuous positive airway pressure (CPAP) on serum leptin levels remain controversial. To address this issue, a meta-analysis was conducted to evaluate the effects of CPAP therapy on serum leptin levels in OSA.

METHODS

A comprehensive literature search was performed to identify studies that focused on the effects of CPAP therapy (treatment duration, ≥4 weeks) on the serum leptin levels of OSA patients. Standardised mean difference (SMD) was used to analyse the summary estimates for CPAP therapy.

RESULTS

Fifteen studies involving 427 patients were included in the meta-analysis. Results indicate that the overall SMD of the leptin levels before and after CPAP therapy was 0.137 (95% confidence interval (CI) 0.002 to 0.272); test for overall effect z=1.99 (P=0.046). Sources of heterogeneity were not found by subgroup and meta-regression analyses. Subgroup analyses showed that differences in OSA severity, baseline body mass index, compliance, CPAP duration and leptin assay did not affect the effectiveness of CPAP therapy.

CONCLUSIONS

The evidence for the use of CPAP therapy on decrease of leptin levels in OSA patients is low, and stronger evidence is needed.

Leptin: a biomarker for sleep disorders?

Leptin, a pleiotropic protein hormone produced mainly by fat cells, regulates metabolic activity and many other physiological functions. The intrinsic circadian rhythm of blood leptin is modulated by gender, development, feeding, fasting, sleep, obesity, and endocrine disorders. Hyperleptinemia is implicated in leptin resistance. To determine the specificity and sensitivity of leptin concentrations in sleep disorders, we summarize here the alterations of leptin in four conditions in animal and human studies: short duration of sleep, sleep fragmentation, obstructive sleep apnea (OSA), and after use of continuous positive airway pressure (CPAP) to treat OSA. The presence and causes of contradictory findings are discussed. Though sustained insufficient sleep lowers fasting blood leptin and therefore probably contributes to increased appetite, obesity and OSA independently result in hyperleptinemia. Successful treatment of OSA by CPAP is predicted to decrease hyperleptinemia, making leptin an ancillary biomarker for treatment efficacy. Current controversies also call for translational studies to determine how sleep disorders regulate leptin homeostasis and how the information can be used to improve sleep treatment.

Pathophysiologic mechanisms of cardiovascular disease in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a highly prevalent sleep disorder, characterized by repeated disruptions of breathing during sleep. This disease has many potential consequences including excessive daytime sleepiness, neurocognitive deterioration, endocrinologic and metabolic effects, and decreased quality of life. Patients with OSAS experience repetitive episodes of hypoxia and reoxygenation during transient cessation of breathing that provoke systemic effects. Furthermore, there may be increased levels of biomarkers linked to endocrine-metabolic and cardiovascular alterations. Epidemiological studies have identified OSAS as an independent comorbid factor in cardiovascular and cerebrovascular diseases, and physiopathological links may exist with onset and progression of heart failure. In addition, OSAS is associated with other disorders and comorbidities which worsen cardiovascular consequences, such as obesity, diabetes, and metabolic syndrome. Metabolic syndrome is an emerging public health problem that represents a constellation of cardiovascular risk factors. Both OSAS and metabolic syndrome may exert negative synergistic effects on the cardiovascular system through multiple mechanisms (e.g., hypoxemia, sleep disruption, activation of the sympathetic nervous system, and inflammatory activation). It has been found that CPAP therapy for OSAS provides an objective improvement in symptoms and cardiac function, decreases cardiovascular risk, improves insulin sensitivity, and normalises biomarkers. OSAS contributes to the pathogenesis of cardiovascular disease independently and by interaction with comorbidities. The present review focuses on indirect and direct evidence regarding mechanisms implicated in cardiovascular disease among OSAS patients.

The role of obesity, different fat compartments and sleep apnea severity in circulating leptin levels: the Icelandic Sleep Apnea Cohort study

Objectives

To assess whether sleep apnea severity has an independent relationship with leptin levels in blood after adjusting for different measures of obesity and whether the relationship between OSA severity and leptin levels differs depending on obesity level.

Methods

Cross-sectional study of 452 untreated obstructive sleep apnea (OSA) patients (377 males and 75 females), in the Icelandic Sleep Apnea Cohort (ISAC), age 54.3±10.6 (mean±SD), BMI 32.7±5.3 kg/m² and apnea-hypopnea index (AHI) 40.2 ± 16.1 events/hour. A sleep study and magnetic resonance imaging of abdominal visceral and subcutaneous fat volume were performed as well as fasting serum morning leptin levels measured.

Results

Leptin levels were more highly correlated with body mass index (BMI), total abdominal and subcutaneous fat volume than visceral fat volume per se. No relationship was found between sleep apnea severity and leptin levels, assessed within three BMI groups (BMI<30, BMI 30–35 and BMI>35 kg/m²). In a multiple linear regression model, adjusted for gender, BMI explained 38.7% of the variance in leptin levels, gender explained 21.2% but OSA severity did not have a significant role and no interaction was found between OSA severity and BMI on leptin levels. However, hypertension had a significant effect on the interaction between OSA severity and obesity (p=0.04). In post-hoc analysis for nonhypertensive OSA subjects (n=249), the association between leptin levels and OSA severity explained a minor but significant variance (3.2%) in leptin levels. This relationship was greatest for nonobese nonhypertensive subjects (significant interaction with obesity level). No relationship of OSA severity and leptin levels was found for hypertensive subjects (n=199).

Conclusion

Obesity and gender are the dominant determinants of leptin levels. OSA severity is not related to leptin levels except to a minor degree in nonhypertensive nonobese OSA subjects.

The reciprocal interaction between obesity and obstructive sleep apnoea

Obesity is a significant risk factor in the pathogenesis of obstructive sleep apnoea (OSA) altering airway anatomy and collapsibility, and respiratory control. The association between obesity and OSA has led to an increasing focus on the role of weight loss as a potential treatment for OSA. To date, most discussion of obesity and OSA assumes a one-way cause and effect relationship, with obesity contributing to the pathogenesis of OSA. However, OSA itself may contribute to the development of obesity. OSA has a potential role in the development and reinforcement of obesity via changes to energy expenditure during sleep and wake periods, dietary habits, the neurohormonal mechanisms that control satiety and hunger, and sleep duration arising from fragmented sleep. Thus, there is emerging evidence that OSA itself feeds back into a complex mechanism that leads either to the development or reinforcement of the obese state. Whilst current evidence does not confirm that treatment of OSA directly influences weight loss, it does suggest that the potential role OSA plays in obesity and weight loss deserves further research.

Nocturnal asthma

PURPOSE OF REVIEW

The aim is to review pathophysiological mechanisms and treatment of nocturnal asthma.

RECENT FINDINGS

Physiologic changes accompanying sleep, as well as the nocturnal phase of circadian rhythms, may have an adverse effect on asthma control. Chronotherapeutic principles, which consider circadian variation in relevant biologic rhythms, may improve asthma outcomes. Administration of long-acting bronchodilators and inhaled corticosteroids which achieve maximum efficacy at night may improve nocturnal asthma. Comorbid conditions that may contribute to nocturnal asthma should be considered. The prevalence of obstructive sleep apnea is greater in a cohort of patients with severe asthma than in moderate asthma and in BMI and age matched nonasthmatic controls, suggesting a link between these diseases. A large trial concluded that esomeprazole did not improve asthma control even with comorbid acid reflux, questioning the importance of acid reflux in asthma. The role of polymorphisms of the β2-adrenergic receptor and their relationship with nocturnal asthma remain controversial.

SUMMARY

Sleep is a time of vulnerability to respiratory compromise, especially in asthma patients experiencing nocturnal exacerbations. This asthma phenotype is associated with poorer control, reduced sleep quality, daytime somnolence and increased morbidity and mortality. Nocturnal asthma is a common but under-recognized problem.

The influence of obesity and obstructive sleep apnea on metabolic hormones

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is a common disorder characterized by excessive daytime sleepiness and repetitive upper airway obstruction episodes during sleep. Clinically, obesity is a major risk factor for developing OSAS. However, OSAS has been associated with hormonal and metabolic alterations that could predispose patients to obesity. The aim of this study was to investigate the independent role of apneas and obesity on plasma levels of metabolic hormones (adiponectin, ghrelin, and leptin) in patients with OSAS.

METHODS

We have studied patients with OSAS and controls with and without obesity. All patients were male, had an apnea-hypopnea index of 20/h or greater, and were eligible for nasal continuous positive airway pressure (nCPAP) treatment. Patients were considered obese (n = 28) when their BMI was higher than 30 kg/m(2) and non-obese (n = 21) when it was lower than 27 kg/m(2). Non-obese control subjects (n = 20) were non-snorers with a normal cardiorespiratory sleep study, while obese control subjects (n = 10) were recruited from those obese subjects who were visited in our sleep unit and for whom OSAS was excluded by full polysomnography. A single blood sample was obtained from an antecubital vein in all participants after the completion of the nocturnal sleep laboratory recording. Plasma leptin, adiponectin, and ghrelin levels were determined by radioimmunoassay.

RESULTS

The adiponectin, ghrelin, and leptin plasma levels were similar in both patients and controls. There were differences in leptin and adiponectin plasma levels between the obese and non-obese in both patient and control groups. In the case of ghrelin, differences between obese and non-obese subjects were only seen in patients. There were no significant differences in hormone levels between the obese controls and obese patients or between non-obese controls and non-obese patients. After 3 months of nCPAP treatment, adiponectin levels decreased significantly both in obese and non-obese patients, and leptin levels decreased in obese patients. Finally, nCPAP did not reduce ghrelin in either obese or non-obese patients.

CONCLUSIONS

The basal levels of leptin, adiponectin, and ghrelin were mostly associated with obesity. We found that sleep apnea was not a determinant factor in leptin, adiponectin, and ghrelin hormonal levels. Interestingly, nCPAP treatment diminishes leptin in obese OSA patients and adiponectin levels in obese and non-obese patients with OSAS.

Sleep and obesity

PURPOSE OF REVIEW

This review summarizes the most recent evidence linking decreased sleep duration and poor sleep quality to obesity, focusing upon studies in adults.

RECENT FINDINGS

Published and unpublished health examination surveys and epidemiological studies suggest that the worldwide prevalence of obesity has doubled since 1980. In 2008, 1 in 10 adults was obese, with women more likely to be obese than men. This obesity epidemic has been paralleled by a trend of reduced sleep duration. Poor sleep quality, which leads to overall sleep loss has also become a frequent complaint. Growing evidence from both laboratory and epidemiological studies points to short sleep duration and poor sleep quality as new risk factors for the development of obesity.

SUMMARY

Sleep is an important modulator of neuroendocrine function and glucose metabolism and sleep loss has been shown to result in metabolic and endocrine alterations, including decreased glucose tolerance, decreased insulin sensitivity, increased evening concentrations of cortisol, increased levels of ghrelin, decreased levels of leptin, and increased hunger and appetite. Recent epidemiological and laboratory evidence confirm previous findings of an association between sleep loss and increased risk of obesity.

Respiratory complications of obesity

Obesity, well known as a cardiovascular risk factor, can also lead to significant respiratory complications. The respiratory changes associated with obesity extend from a simple change in respiratory function, with no effect on gas exchange, to the more serious condition of hypercapnic respiratory failure, characteristic of obesity hypoventilation syndrome. More recently, it has been reported that there is an increased prevalence of asthma which is probably multifactorial in origin, but in which inflammation may play an important role. Hypoventilation in the obese subject is the result of complex interactions that involve changes in the ventilatory mechanics and anomalies in breathing control. Two other conditions (COPD and sleep apnea-hypopnea syndrome [SAHS], often present in obese patients, can trigger or aggravate it. The prevalence of hypoventilation in the obese is under-estimated and the diagnosis is usually established during an exacerbation, or when the patient is studied due to suspicion of SAHS. Ventilatory management of these patients includes either CPAP or NIV. The choice of one or another will depend on the underlying clinical condition and whether or not there is another comorbidity. Both NIV and CPAP have demonstrated their effectiveness, not only in the control of gas exchange, but also in improving the quality of life and survival of these patients.

Sleep apnea and diabetes: insights into the emerging epidemic

The rampant diabetes pandemic over the past few decades has been associated with an increased rise in cardiovascular events and deaths. Risk factors such as obesity, family history of diabetes, decreased physical activity, and aging are among the most common in the development of diabetes. Emerging evidence in the past 10 years has suggested that sleep apnea is a novel risk factor in the development of diabetes. Associations between diabetes and sleep apnea are supported by both epidemiologic and clinical sleep apnea studies. In this report, we discuss epidemiologic and clinical evidence suggesting that sleep apnea is involved in the pathogenesis of altered glucose metabolism. In light of current evidence, sleep apnea treatment should be incorporated into existing pharmacotherapeutic regimens for optimal management of diabetes among diabetic patients with sleep apnea to reduce associated cardiovascular risk. Suggestions to improve practice guidelines in the management of diabetic patients with sleep apnea are provided.

The role of leptin in the respiratory system: an overview

Since its cloning in 1994, leptin has emerged in the literature as a pleiotropic hormone whose actions extend from immune system homeostasis to reproduction and angiogenesis. Recent investigations have identified the lung as a leptin responsive and producing organ, while extensive research has been published concerning the role of leptin in the respiratory system. Animal studies have provided evidence indicating that leptin is a stimulant of ventilation, whereas researchers have proposed an important role for leptin in lung maturation and development. Studies further suggest a significant impact of leptin on specific respiratory diseases, including obstructive sleep apnoea-hypopnoea syndrome, asthma, COPD and lung cancer. However, as new investigations are under way, the picture is becoming more complex. The scope of this review is to decode the existing data concerning the actions of leptin in the lung and provide a detailed description of leptin's involvement in the most common disorders of the respiratory system.

Obstructive sleep apnea syndrome and fatty liver: Association or causal link?

Obstructive sleep apnea (OSA) is a complex disorder that consists of upper airway obstruction, chronic intermittent hypoxia and sleep fragmentation. OSA is well known to be associated with hypoxia, insulin resistance and glucose intolerance, and these factors can occur in the presence or absence of obesity and metabolic syndrome. Although it is well established that insulin resistance, glucose intolerance and obesity occur frequently with non-alcoholic fatty liver disease (NAFLD), it is now becoming apparent that hypoxia might also be important in the development of NAFLD, and it is recognized that there is increased risk of NAFLD with OSA. This review discusses the association between OSA, NAFLD and cardiovascular disease, and describes the potential role of hypoxia in the development of NAFLD with OSA.

Disorders of glucose metabolism in sleep-disordered breathing

Despite proliferating literature, the exact relationship between obstructive sleep apnea (OSA) and alterations in glucose metabolism is still controversial. There is growing evidence to suggest that OSA imposes adverse effects on glucose metabolism, but the translation into clinical effect is not well delineated. Many potential mechanisms are being explored, mostly relating to peripheral tissue response to insulin and more recently regarding pancreatic beta cell function of insulin secretion. The effect of OSA on glucose metabolism is likely to be influenced by many personal characteristics. Age, degree of adiposity, lifestyle, comorbidities, and even the stage of glucose disorder itself may modify the relationship between OSA and glucose metabolism. In the biologic system of the human body, all these interact to culminate in clinically relevant outcomes.

Changes in obstructive sleep apnea severity, biomarkers, and quality of life after multilevel surgery

OBJECTIVES/HYPOTHESIS

To evaluate the impact of multilevel obstructive sleep apnea surgical treatment on sleep-disordered breathing severity, health-related measures, and quality of life, and to examine the association between changes in sleep-disordered breathing severity and these other outcomes.

STUDY DESIGN

Prospective cohort study.

METHODS

Subjects with obstructive sleep apnea unable to tolerate positive airway pressure therapy and with evidence of multilevel (palate and hypopharynx) obstruction underwent uvulopalatopharyngoplasty, tonsillectomy, and genioglossus advancement, with or without hyoid suspension. All subjects had preoperative and postoperative study assessments, including blood draw for C-reactive protein, interleukin-6, homocysteine, homeostasis model of insulin resistance, and leptin, and evaluation with the Functional Outcomes of Sleep Questionnaire.

RESULTS

Thirty subjects underwent multilevel surgical treatment. The mean apnea-hypopnea index decreased from 44.9 +/- 28.1 to 27.8 +/- 26.4 events/hour (P = .008). Thirteen (43%) subjects in this heterogeneous sample achieved a response to surgery (defined as an apnea-hypopnea index reduction of >or=50% to an absolute level <15 events/hour), and body mass index <or=32 kg/m(2) was associated with a higher likelihood (55%, 12/22) of response (P = .04). There was no overall change in C-reactive protein levels, but responders demonstrated a decrease (-1.02 +/- 0.98 mg/L, P = .003) that was independent of changes in body weight. There were no significant changes in other health-related measures. Responders and nonresponders both demonstrated improvements in sleep-related quality of life.

CONCLUSIONS

This multilevel surgery was associated with a low likelihood of response in subjects with body mass index >32 kg/m(2). Responders had decreased C-reactive protein levels that were independent of changes in body weight.

Obstructive sleep apnea and the metabolic syndrome

Obstructive sleep apnea (OSA) and the metabolic syndrome have a strong association with each other owing to their common feature of obesity, but an association independent of obesity has been demonstrated in several studies. There is also evidence, of varying strengths, from epidemiologic and clinical studies, for the independent association between OSA and individual core components of the metabolic syndrome, including hypertension, insulin resistance and dyslipidemia. To date, the data are strongest for hypertension, while data for adverse glucose or lipid metabolism are more controversial. Obesity and other factors, such as alcohol drinking and smoking, obviously pose major confounding hurdles to the clarification of the causal or aggravational role of OSA on cardiometabolic risks. Recurrent episodes of obstructed breathing notably result in intermittent hypoxemia and sleep fragmentation, and these may in turn lead to many adverse body responses, including sympathetic activation, neurohumeral changes and inflammation, which are the seeds for cardiometabolic dysfunctions, such as atherosclerosis and diabetes mellitus. Evidence from translational studies or animal/cell work are forthcoming in the delineation of these pathogenetic mechanisms.

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.

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.

Obstructive sleep apnea, inflammation, and the metabolic syndrome

The combination of metabolic syndrome and obstructive sleep apnea (OSA) has been termed "syndrome Z." The prevalence of both OSA and metabolic syndrome is increasing worldwide, in part linked to the epidemic of obesity. Beyond their epidemiologic relationship, growing evidence suggests that OSA may be causally related to metabolic syndrome. We are only beginning to understand the potential mechanisms underlying the OSA-metabolic syndrome interaction. Although there is no clear consensus, there is growing evidence that alterations in the hypothalamic-pituitary axis, generation of reactive oxygen species (ROS) due to repetitive hypoxia, inflammation, and generation of adipokines may be implicated in the changes associated with both OSA and metabolic syndrome. Whether some or all of these metabolic alterations mechanistically link OSA to metabolic syndrome remains to be proven, but it is an area of intense scientific interest.

Daytime Sleepiness and Functional Outcomes in Older Adults With Diabetes

Purpose

This secondary analysis examined the effect of excessive sleepiness on daytime function in older adults with diabetes from the National Sleep Foundation's Sleep and Aging poll.

Methods

Respondents were older adults (N = 1506; age range, 55-84 years) evaluated by telephone survey on their sleep duration, sleep disturbances, daytime functional outcomes, and self-reported height, weight, and comorbidities.

Results

Approximately 16% (n = 244) of the sample acknowledged a diagnosis of diabetes; they were older, had more comorbidities, had a higher body mass index (BMI), and were more likely to be sleepy during the daytime than nondiabetic respondents (all P < .05). Respondents with diabetes who reported frequent daytime sleepiness (n = 50; 20%) had significantly (P < .05) higher BMI, lower self-rated health, and more sleep disturbances than those who were not sleepy (n = 194). Sleepy respondents with diabetes also reported more frequent feelings of depression, decreased pleasure in life, naps, feeling drowsy, or dozing off while driving (all P < .05). Excessive sleepiness was significantly associated (P < .001) with an increased risk for depressive symptoms while controlling for BMI, age, and number of comorbidities.

Conclusions

These results indicate that sleep disturbances affect not only sleep quality but also daytime function in older adults with diabetes.

Effects of poor and short sleep on glucose metabolism and obesity risk

The importance of sleep to hormones and glucose metabolism was first documented more than four decades ago. Since then, sleep curtailment has become an endemic behavior in modern society. In addition, the prevalence of sleep disorders, particularly obstructive sleep apnea (OSA), has increased. OSA is very common in endocrine and metabolic disorders, but often remains undiagnosed. This Review summarizes the laboratory and epidemiologic evidence that suggests how sleep loss, either behavioral or disease-related, and poor quality of sleep might promote the development of obesity and diabetes mellitus, and exacerbate existing endocrine conditions. Treatment of sleep disorders has the potential to improve glucose metabolism and energy balance. Screening for habitual sleep patterns and OSA might be critically important for patients with endocrine and metabolic disorders.

Acylated ghrelin level in patients with OSA before and after nasal CPAP treatment

BACKGROUND AND OBJECTIVE

Patients with newly diagnosed OSA have been reported to have recent weight gain prior to diagnosis. Ghrelin stimulates food intake and increases weight gain. Plasma ghrelin is decreased in obese and increased in lean individuals. Of the two circulating forms of ghrelin, acylated and unacylated, the former is thought to be essential for the biological activity of ghrelin.

METHODS

The plasma levels of the two forms of ghrelin were measured in 21 OSA patients (with a mean of 46.2 sleep-disordered events/h) before and after 1 month of nasal CPAP (nCPAP) treatment, and were compared with those in 14 untreated OSA patients and 13 individuals without OSA.

RESULTS

The BMI was significantly higher in the 21 OSA patients than in the non-OSA group as were the baseline acylated (11.4 +/- 5.86 vs 7.19 +/- 3.80 fmol/mL, P = 0.03) and unacylated (84.2 +/- 50.6 vs 48.3 +/- 23.2 fmol/mL, P = 0.02) ghrelin levels. The total ghrelin level was positively correlated with the number of sleep-disordered breathings (P = 0.002). After 1 month of nCPAP treatment, the acylated ghrelin level significantly decreased (P = 0.02) while the unacylated ghrelin level did not (P = 0.09).

CONCLUSIONS

Treatment of OSA may play an important role in the management of obesity in these patients by reducing the acylated ghrelin level.

Obstructive sleep apnea syndrome and asthma: the role of continuous positive airway pressure treatment

OBJECTIVE

To review the concept of a possible link between asthma and obstructive sleep apnea syndrome (OSAS) and the impact on asthma symptoms of treatment of OSAS with continuous positive airway pressure (CPAP) in patients with both conditions.

DATA SOURCES

The Ovid, MEDLINE, and PubMed databases from 1950 to the present were searched for relevant articles regarding a possible relationship between asthma and OSAS and the effectiveness of CPAP in treating OSAS.

STUDY SELECTION

Articles describing pathophysiologic conditions occurring in OSAS that may be linked to asthma pathogenesis were used for this review.

RESULTS

The data suggest that OSAS is an independent risk factor for asthma exacerbations. CPAP has been shown in prospective clinical studies to have a positive impact on asthma outcome in patients with concomitant OSAS. Ameliorative mechanisms of treatment with CPAP include mechanical and neuromechanical effects, gastroesophageal acid reflux suppression, local and systemic anti-inflammatory effects (including suppression of increased serum levels of inflammatory cytokines, chemokines, and vascular endothelial growth factor), cardiac function improvements, leptin level suppression, weight reduction, and sleep restoration.

CONCLUSIONS

Asthma and OSAS are increasingly troublesome public health issues. Mounting evidence implicates OSAS as a risk factor for asthma exacerbations, thereby linking these 2 major epidemics. We describe potential mechanisms whereby CPAP, the first line of therapy for OSAS, might modify airway smooth muscle function and asthma control in patients with both disorders. Despite the ever-increasing population of patients with both disorders, large, prospective, randomized controlled studies are necessary to more fully evaluate CPAP and asthma outcomes.

Autoadjusting-CPAP effect on serum leptin concentrations in obstructive sleep apnoea patients

Background

Leptin is an hormone that regulates body weight. Studies have shown increasing leptin concentrations according to body mass index (BMI) and intermittent hypoxia.

Our aim is to evaluate the basal leptin levels in OSA patients and its possible relation to OSA severity, independently of confounders and investigate the Autoadjusting-CPAP effect on leptin values.

Methods

In ninety eight male patients with moderate to severe OSA leptin serum levels were evaluated before therapy, 9 days and 6 months after therapy.

Results

In this group mean age was 55.3 years, mean BMI was 33.2 Kg/m2 and mean Apnoea- Hypopnea Index (AHI) was 51.7/h. Mean basal serum leptin value was 12.1 ug/L. Univariate analysis showed a significant correlation between serum leptin values and BMI (R = 0.68; p < 0.001), waist-hip ratio (R = 0.283; p = 0.004) and AHI (R = 0.198; p = 0.048); in stepwise multiple regression analysis only BMI (p < 0.001) was a predictor of serum leptin values.

One week after therapy, mean leptin serum level decreased to 11.0 ug/L and 6 months after it was 11.4 ug/L. (p = 0.56 and p = 0.387, respectively)

Conclusion

Baseline leptin serum levels positively correlate with BMI, fat distributioand OSA severity.

BMI is the only predictor of basal leptin levels.

Treatment with Autoadjusting-CPAP has a small effect on leptin levels.

Association of sleep apnea severity and obesity with insulin resistance, C-reactive protein, and leptin levels in male patients with obstructive sleep apnea

Obesity is the major confounding factor in the relationship between obstructive sleep apnea and increased risk for cardiovascular disease. The aim of the study was to investigate the association of sleep apnea severity with insulin resistance, leptin, and CRP levels in a cohort of male patients. Sixty-seven men referred to our sleep laboratory for evaluation of suspected obstructive sleep apnea syndrome (OSAS) were divided into three groups according to apnea severity: non-OSAS group (n=15), mild to moderate OSAS group (n=26), and severe OSAS (n=26). Insulin resistance was estimated by the homeostasis model assessment method. HOMA values were similar in the three groups: (3.2+/-2.2 vs. 3.3+/-1.8 vs. 3.6+/-1.5, respectively, p=0.71). Leptin levels were higher in the mild to moderate OSAS group (23.1+/-21.8 ng/ml, p<0.05) and in the severe OSAS group (20.2+/-17.5 ng/ml, p<0.05) than in the non-OSAS group (9.4+/-6.4 ng/ml). CRP levels were significantly higher in severe sleep apnea (0.35+/-0.3 vs. 0.19+/-0.1 mg/dl, p<0.05). In multiple regression analyses, waist-to-hip ratio (WHR) was the most significant determinant of HOMA estimation for insulin resistance. WHR and the percentage of total sleep time spent with hypoxemia (%TST with SaO2 <90%) were significant predictors for leptin levels, while body mass index (BMI) and the %TST with SaO2 <90% were the best predicting parameters for CRP levels. Insulin resistance estimated by the HOMA method in male patients with OSAS was not associated with sleep apnea severity independent of obesity. The severity of nocturnal hypoxemia was associated with leptin and CRP levels independent of obesity.

Abdominal fat and sleep apnea: the chicken or the egg?

Obstructive sleep apnea (OSA) syndrome is a disorder characterized by repetitive episodes of upper airway obstruction that occur during sleep. Associated features include loud snoring, fragmented sleep, repetitive hypoxemia/hypercapnia, daytime sleepiness, and cardiovascular complications. The prevalence of OSA is 2-3% and 4-5% in middle-aged women and men, respectively. The prevalence of OSA among obese patients exceeds 30%, reaching as high as 50-98% in the morbidly obese population. Obesity is probably the most important risk factor for the development of OSA. Some 60-90% of adults with OSA are overweight, and the relative risk of OSA in obesity (BMI >29 kg/m(2)) is >or=10. Numerous studies have shown the development or worsening of OSA with increasing weight, as opposed to substantial improvement with weight reduction. There are several mechanisms responsible for the increased risk of OSA with obesity. These include reduced pharyngeal lumen size due to fatty tissue within the airway or in its lateral walls, decreased upper airway muscle protective force due to fatty deposits in the muscle, and reduced upper airway size secondary to mass effect of the large abdomen on the chest wall and tracheal traction. These mechanisms emphasize the great importance of fat accumulated in the abdomen and neck regions compared with the peripheral one. It is the abdomen much more than the thighs that affect the upper airway size and function. Hence, obesity is associated with increased upper airway collapsibility (even in nonapneic subjects), with dramatic improvement after weight reduction. Conversely, OSA may itself predispose individuals to worsening obesity because of sleep deprivation, daytime somnolence, and disrupted metabolism. OSA is associated with increased sympathetic activation, sleep fragmentation, ineffective sleep, and insulin resistance, potentially leading to diabetes and aggravation of obesity. Furthermore, OSA may be associated with changes in leptin, ghrelin, and orexin levels; increased appetite and caloric intake; and again exacerbating obesity. Thus, it appears that obesity and OSA form a vicious cycle where each results in worsening of the other.