Two randomized placebo-controlled trials to evaluate the efficacy and tolerability of mirtazapine for the treatment of obstructive sleep apnea

Epidemiology of Sleep-Disordered Breathing and Heart Failure: What Drives What

PURPOSE OF REVIEW

The bidirectional relationships that have been demonstrated between heart failure (HF) and central sleep apnea (CSA) demand further exploration with respect to the implications that each condition has for the other. This review discusses the body of literature that has accumulated on these relationships and how CSA and its potential treatment may affect outcomes in patients with CSA.

RECENT FINDINGS

Obstructive sleep apnea (OSA) can exacerbate hypertension, type 2 diabetes, obesity, and atherosclerosis, which are known predicates of HF. Conversely, patients with HF more frequently exhibit OSA partly due to respiratory control system instability. These same mechanisms are responsible for the frequent association of HF with CSA with or without a Hunter-Cheyne-Stokes breathing (HCSB) pattern. Just as is the case with OSA, patients with HF complicated by CSA exhibit more severe cardiac dysfunction leading to increased mortality; the increase in severity of HF can in turn worsen the degree of sleep disordered breathing (SDB). Thus, a bidirectional relationship exists between HF and both phenotypes of SDB; moreover, an individual patient may exhibit a combination of these phenotypes. Both types of SDB remain significantly underdiagnosed in patients with HF and hence undertreated. Appropriate screening for, and treatment of, OSA is clearly a significant factor in the comprehensive management of HF, while the relevance of CSA remains controversial. Given the unexpected results of the Treatment of Sleep-Disordered Breathing with Predominant Central Sleep Apnea by Adaptive Servo Ventilation in Patients with Heart Failure trial, it is now of paramount importance that additional analysis of these data be expeditiously reported. It is also critical that ongoing and proposed prospective studies of this issue proceed without delay.

Obstructive sleep apnea: current perspectives

The prevalence of obstructive sleep apnea (OSA) continues to rise. So too do the health, safety, and economic consequences. On an individual level, the causes and consequences of OSA can vary substantially between patients. In recent years, four key contributors to OSA pathogenesis or "phenotypes" have been characterized. These include a narrow, crowded, or collapsible upper airway "anatomical compromise" and "non-anatomical" contributors such as ineffective pharyngeal dilator muscle function during sleep, a low threshold for arousal to airway narrowing during sleep, and unstable control of breathing (high loop gain). Each of these phenotypes is a target for therapy. This review summarizes the latest knowledge on the different contributors to OSA with a focus on measurement techniques including emerging clinical tools designed to facilitate translation of new cause-driven targeted approaches to treat OSA. The potential for some of the specific pathophysiological causes of OSA to drive some of the key symptoms and consequences of OSA is also highlighted.

From diagnosis to long-term management: the experiences of older New Zealanders with obstructive sleep apnoea

ABSTRACT INTRODUCTION In New Zealand (NZ), access to public sleep services is limited to people deemed with the highest need. The prevalence of obstructive sleep apnoea (OSA) increases with age, but the symptoms and the treatment pathway is expected to differ for older compared to younger patients. This study explored the experience of older people regarding diagnosis and treatment services for OSA in order to inform considerations required in primary health and sleep services. METHODS Patients who were initiated on Continuous Positive Airway Pressure (CPAP) therapy at the age of 65 years or older were invited to one of three 1.5-h focus group discussions. In total, 16 patients attended; nine were accompanied by their spouse or partner. Discussions were semi-structured and explored experiences with the OSA pathway, from diagnosis through to long-term management. RESULTS Thematic analysis highlights the key symptoms of OSA. Patients’ experiences with diagnostic and treatment services were generally positive. However, there was an overarching need for greater knowledge and follow up regarding OSA and CPAP therapy. Most patients were happy with CPAP treatment. Issues associated with long-term use, comfort and daily management were highlighted, and strategies used to overcome them discussed. DISCUSSION Focus groups reported similar experiences, positively endorsing the health value of OSA diagnosis and CPAP therapy. Mechanisms and resources are required at a primary healthcare level in order to raise awareness around sleep and aging, OSA and CPAP. This would aid earlier and more appropriate diagnosis and management of OSA and help overcome some of the gaps identified in this study.

Depressive symptoms in patients with obstructive sleep apnea: biological mechanistic pathways

This study examined the association between depressive symptoms, as well as depressive symptom dimensions, and three candidate biological pathways linking them to Obstructive sleep apnea (OSA): (1) inflammation; (2) circulating leptin; and (3) intermittent hypoxemia. Participants included 181 obese adults with moderate-to-severe OSA enrolled in the Cardiovascular Consequences of Sleep Apnea (COSA) trial. Depressive symptoms were measured using the Beck Depression Inventory-II (BDI-II). We assessed inflammation using C-reactive protein levels (CRP), circulating leptin by radioimmunoassay using a double antibody/PEG assay, and intermittent hypoxemia by the percentage of sleep time each patient had below 90% oxyhemoglobin saturation. We found no significant associations between BDI-II total or cognitive scores and CRP, leptin, or percentage of sleep time below 90% oxyhemoglobin saturation after controlling for relevant confounding factors. Somatic symptoms, however, were positively associated with percentage of sleep time below 90% saturation (β = 0.202, P = 0.032), but not with CRP or circulating leptin in adjusted models. Another significant predictor of depressive symptoms included sleep efficiency (β_{BDI Total} = -0.230, P = 0.003; β_cognitive = -0.173, P = 0.030 (β_somatic = -0.255, P = 0.001). In patients with moderate-to-severe OSA, intermittent hypoxia may play a role in somatic rather than cognitive or total depressive symptoms.

Narrative review of contemporary treatment options in the care of patients with obstructive sleep apnoea

Snoring and obstructive sleep apnoea (OSA) are increasingly common conditions, and confer a significant health and socioeconomic burden. Furthermore, untreated OSA represents a significant mortality risk. Patients require careful assessment, including detailed clinical history and examination, sleep study and drug-induced sleep endoscopy (DISE). Although nasal continuous positive airway pressure (nCPAP) is the gold standard treatment for moderate and severe OSA, multidisciplinary team assessment is often required to develop the best treatment plan for an individual, especially when nasal CPAP is poorly tolerated. There is a wide range of medical and surgical treatment options, and following appropriate patient selection and assessment, a focused site-specific, often multilevel, intervention is indicated. There is an increasing body of evidence in the literature supporting these multilevel interventions and with agreement on standardized outcome measures more trials are likely to improve the robustness of these data further.

Understanding Phenotypes of Obstructive Sleep Apnea: Applications in Anesthesia, Surgery, and Perioperative Medicine

Obstructive sleep apnea (OSA) is a prevalent sleep-disordered breathing with potential long-term major neurocognitive and cardiovascular sequelae. The pathophysiology of OSA varies between individuals and is composed of different underlying mechanisms. Several components including the upper airway anatomy, effectiveness of the upper airway dilator muscles such as the genioglossus, arousal threshold of the individual, and inherent stability of the respiratory control system determine the pathogenesis of OSA. Their recognition may have implications for the perioperative health care team. For example, OSA patients with a high arousal threshold are likely to be sensitive to sedatives and narcotics with a higher risk of respiratory arrest in the perioperative period. Supplemental oxygen therapy can help to stabilize breathing in OSA patients with inherent respiratory instability. Avoidance of supine position can minimize airway obstruction in patients with a predisposition to upper airway collapse in this posture. In this review, the clinically relevant endotypes and phenotypes of OSA are described. Continuous positive airway pressure (CPAP) therapy is the treatment of choice for most patients with OSA but tolerance and adherence can be a problem. Patient-centered individualized approaches to OSA management will be the focus of future research into developing potential treatment options that will help decrease the disease burden and improve treatment effectiveness.

Influence of Lung Function and Sleep-disordered Breathing on All-Cause Mortality. A Community-based Study

RATIONALE

Whether sleep-disordered breathing (SDB) severity and diminished lung function act synergistically to heighten the risk of adverse health outcomes remains a topic of significant debate.

OBJECTIVES

The current study sought to determine whether the association between lower lung function and mortality would be stronger in those with increasing severity of SDB in a community-based cohort of middle-aged and older adults.

METHODS

Full montage home sleep testing and spirometry data were analyzed on 6,173 participants of the Sleep Heart Health Study. Proportional hazards models were used to calculate risk for all-cause mortality, with FEV₁ and apnea-hypopnea index (AHI) as the primary exposure indicators along with several potential confounders.

MEASUREMENTS AND MAIN RESULTS

All-cause mortality rate was 26.9 per 1,000 person-years in those with SDB (AHI ≥5 events/h) and 18.2 per 1,000 person-years in those without (AHI <5 events/h). For every 200-ml decrease in FEV₁, all-cause mortality increased by 11.0% in those without SDB (hazard ratio, 1.11; 95% confidence interval, 1.08-1.13). In contrast, for every 200-ml decrease in FEV₁, all-cause mortality increased by only 6.0% in participants with SDB (hazard ratio, 1.06; 95% confidence interval, 1.04-1.09). Additionally, the incremental influence of lung function on all-cause mortality was less with increasing severity of SDB (P value for interaction between AHI and FEV₁, 0.004).

CONCLUSIONS

Lung function was associated with risk for all-cause mortality. The incremental contribution of lung function to mortality diminishes with increasing severity of SDB.

An Official American Thoracic Society Research Statement: Impact of Mild Obstructive Sleep Apnea in Adults

BACKGROUND

Mild obstructive sleep apnea (OSA) is a highly prevalent disorder in adults; however, whether mild OSA has significant neurocognitive and cardiovascular complications is uncertain.

OBJECTIVES

The specific goals of this Research Statement are to appraise the evidence regarding whether long-term adverse neurocognitive and cardiovascular outcomes are attributable to mild OSA in adults, evaluate whether or not treatment of mild OSA is effective at preventing or reducing these adverse neurocognitive and cardiovascular outcomes, delineate the key research gaps, and provide direction for future research agendas.

METHODS

Literature searches from multiple reference databases were performed using medical subject headings and text words for OSA in adults as well as by hand searches. Pragmatic systematic reviews of the relevant body of evidence were performed.

RESULTS

Studies were incongruent in their definitions of "mild" OSA. Data were inconsistent regarding the relationship between mild OSA and daytime sleepiness. However, treatment of mild OSA may improve sleepiness in patients who are sleepy at baseline and improve quality of life. There is limited or inconsistent evidence pertaining to the impact of therapy of mild OSA on neurocognition, mood, vehicle accidents, cardiovascular events, stroke, and arrhythmias.

CONCLUSIONS

There is evidence that treatment of mild OSA in individuals who demonstrate subjective sleepiness may be beneficial. Treatment may also improve quality of life. Future research agendas should focus on clarifying the effect of mild OSA and impact of effective treatment on other neurocognitive and cardiovascular endpoints as detailed in the document.

Prevalence of Sleep-Disordered Breathing During Routine Electroencephalogram (EEG): A Hospital-Based Descriptive Study

Sleep-disordered breathing (SDB) in adults is a common condition that is associated with a range of medical problems including hypertension, cardiovascular complications, and increase of seizure frequency in susceptible individuals. Polysomnography (PSG) is considered the gold standard measure in the diagnosis of SDB. This is an observational study on the frequency of SDB in adult patients referred for routine EEG. We found that routine EEG was capable of detecting moderate to severe symptoms of SDB in 14% of adult patients (95% confidence interval = 8.1-19.9%). The state of sleep during a routine EEG recording could help in assessing a SDB pattern and could provide an opportunity for further diagnostic sleep consultation if the patient has not previously reported problems with sleep or if SDB was not considered by the referring physician. This study underscores the need for a practice approach to ensure that patients suffering from SDB are properly referred to a sleep specialist. In the context of this report, some training and experience in PSG can be an added advantage for EEG technologists in the detection of SDB.

A randomized controlled trial of an ambulatory approach versus the hospital-based approach in managing suspected obstructive sleep apnea syndrome

Comparisons of home-based versus hospital-based approach in managing patients with suspected obstructive sleep apnoea syndrome(OSAS). A prospective, controlled CPAP parallel study of new referrals with suspected OSAS randomized into group A) home-based or B) hospital-based approach. Following detection of AHI ≥ 15/hr by Embletta sleep study (group A) or polysomnography (group B), patients received CPAP for 3 months after an overnight autoCPAP titration at home or in hospital respectively. Modified intention-to-treat analysis of those with AHI ≥ 15/hr on CPAP (n = 86 vs 86) showed no difference in Epworth sleepiness score, the primary endpoint, but greater improvement in Sleep-Apnoea-Quality-of-Life-Index[difference 0.3,(95%CI 0.02, 0.6), p = 0.033] at 3 months in group A. The mean costs for the patients in group A and group B were HK$8479(989) and HK$22,248(2407) respectively. The mean difference between groups was HK$-13,769(USD 1770 equivalent) per patient with 95% CI. (−14324, −13213), p < 0.001. The waiting time of patients with AHI ≥ 15/hr who were started on CPAP treatment from the first clinic consultation to the diagnostic sleep test, autoCPAP titration, and CPAP treatment was 189.6, 148.8 and 145.0 days shorter in group A than group B respectively. Home-based approach is non-inferior to hospital-based approach in managing patients with suspected OSAS, with shorter waiting time, and substantial cost savings.

2-Adrenergic blockade rescues hypoglossal motor defense against obstructive sleep apnea

Decreased noradrenergic excitation of hypoglossal motoneurons during sleep causing hypotonia of pharyngeal dilator muscles is a major contributor to the pathogenesis of obstructive sleep apnea (OSA), a widespread disease for which treatment options are limited. Previous OSA drug candidates targeting various excitatory/inhibitory receptors on hypoglossal motoneurons have proved unviable in reactivating these neurons, particularly during rapid-eye-movement (REM) sleep. To identify a viable drug target, we show that the repurposed α₂-adrenergic antagonist yohimbine potently reversed the depressant effect of REM sleep on baseline hypoglossal motoneuron activity (a first-line motor defense against OSA) in rats. Remarkably, yohimbine also restored the obstructive apnea-induced long-term facilitation of hypoglossal motoneuron activity (hLTF), a much-neglected form of noradrenergic-dependent neuroplasticity that could provide a second-line motor defense against OSA but was also depressed during REM sleep. Corroborating immunohistologic, optogenetic, and pharmacologic evidence confirmed that yohimbine's beneficial effects on baseline hypoglossal motoneuron activity and hLTF were mediated mainly through activation of pontine A7 and A5 noradrenergic neurons. Our results suggest a 2-tier (impaired first- and second-line motor defense) mechanism of noradrenergic-dependent pathogenesis of OSA and a promising pharmacotherapy for rescuing both these intrinsic defenses against OSA through disinhibition of A7 and A5 neurons by α₂-adrenergic blockade.

Effect of adrenal medullectomy on metabolic responses to chronic intermittent hypoxia in the frequently sampled intravenous glucose tolerance test

Obstructive sleep apnea is associated with type 2 diabetes. We have previously developed a mouse model of intermittent hypoxia (IH) mimicking oxyhemoglobin desaturations in patients with sleep apnea and have shown that IH increases fasting glucose, hepatic glucose output, and plasma catecholamines. We hypothesize that adrenal medulla modulates glucose responses to IH and that such responses can be prevented by adrenal medullectomy. We performed adrenal medullectomy or sham surgery in lean C57BL/6J mice, which were exposed to IH or intermittent air (control) for 4 wk followed by the frequently sampled intravenous glucose tolerance test (FSIVGTT) in unanesthetized unrestrained animals. IH was administered during the 12-h light phase (9 AM to 9 PM) by decreasing inspired oxygen from 21 to 6.5% 60 cycles/h. Insulin sensitivity (S_I), insulin independent glucose disposal [glucose effectiveness (S_G)], and the insulin response to glucose (AIR_G) were determined using the minimal model method. In contrast to our previous data obtained in restrained mice, IH did not affect fasting blood glucose and plasma insulin levels in sham-operated mice. IH significantly decreased S_G but did not affect S_I and AIR_G Adrenal medullectomy decreased fasting blood glucose and plasma insulin levels and increased glycogen synthesis in the liver in hypoxic mice but did not have a significant effect on the FSIVGTT metrics. We conclude that, in the absence of restraints, IH has no effect on glucose metabolism in lean mice with exception of decreased S_G, whereas adrenal medullectomy decreases fasting glucose and insulin levels in the IH environment.NEW & NOTEWORTHY To our knowledge, this is the first study examining the role of adrenal catecholamines in glucose metabolism during intermittent hypoxia (IH) in unanesthetized unrestrained C57BL/6J mice. We report that IH did not affect fasting glucose and insulin levels nor insulin sensitivity and insulin secretion during, whereas glucose effectiveness was decreased. Adrenal medullectomy decreased fasting blood glucose and insulin levels in mice exposed to IH but had no effect on glucose metabolism, insulin secretion, and insulin sensitivity.

Impact of concomitant medications on obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is characterized by repeated episodes of apnoea and hypopnoea during sleep. Little is known about the potential impact of therapy drugs on the underlying respiratory disorder. Any influence should be taken into account and appropriate action taken, including drug withdrawal if necessary. Here, we review drugs in terms of their possible impact on OSA; drugs which (1) may worsen OSA; (2) are unlikely to have an impact on OSA; (3) those for which data are scarce or contradictory; and (4) drugs with a potentially improving effect. The level of evidence is ranked according to three grades: A - randomized controlled trials (RCTs) with high statistical power; B - RCTs with lower power, non-randomized comparative studies and observational studies; C - retrospective studies and case reports. Our review enabled us to propose clinical recommendations. Briefly, agents worsening OSA or inducing weight gain, that must be avoided, are clearly identified. Drugs such as 'Z drugs' and sodium oxybate should be used with caution as the literature contains conflicting results. Finally, larger trials are needed to clarify the potential positive impact of certain drugs on OSA. In the meantime, some, such as diuretics or other antihypertensive medications, are helpful in reducing OSA-associated cardiovascular morbidity.

Heart rate acceleration runs and deceleration runs in patients with obstructive sleep apnea syndrome

PURPOSE

This study aimed to explore the patterns of heart rate acceleration runs and deceleration runs in patients with obstructive sleep apnea syndrome and to investigate the influence of apnea events on this pattern.

METHODS

The 6-h electrocardiography results of patients who were referred for overnight polysomnography were retrospectively analyzed. The frequencies of heart rate acceleration runs and deceleration runs of different lengths were calculated for each patient and compared among patients with obstructive sleep apnea syndrome of varying degrees of severity, between patients with obstructive sleep apnea on and off continuous positive airway pressure, and between two matched groups of patients with idiopathic central sleep apnea and obstructive sleep apnea.

RESULTS

A total of 231 patients were enrolled. Patients with severe obstructive sleep apnea exhibited significantly increased frequencies of long acceleration and deceleration runs after multivariate adjustment, while no significant differences were observed in the frequencies of short runs. Thirty-nine obstructive sleep apnea patients who were treated with continuous positive airway pressure showed a significant decrease in the frequency of long deceleration runs and a decreasing trend in the frequency of long acceleration runs. Patients with idiopathic pure central sleep apnea exhibited no significant changes in the frequencies of acceleration and deceleration runs after they were placed on continuous positive airway pressure.

CONCLUSIONS

The distributions of heart rate acceleration and deceleration runs are related to the severity of obstructive sleep apnea. Long runs are more closely related to obstructive respiratory events, while short runs do not appear to be related to these events.

Obstructive sleep apnoea and risks of all-cause mortality: preliminary evidence from prospective cohort studies

PURPOSE

A meta-analysis of prospective cohort studies was conducted to clarify the association between obstructive sleep apnoea (OSA) and future risk of all-cause mortality.

METHODS

Eligible studies were identified by searching the PubMed and EMBASE databases up to July 2015. Pooled hazard ratios (HRs) and their corresponding 95 % confidence intervals (CIs) were calculated to estimate the association between OSA and risk of all-cause mortality. Sources of heterogeneity were identified by subgroup and meta-regression analyses.

RESULTS

Twelve prospective cohort studies involving 34,382 participants were included in this meta-analysis. The pooled HR of all-cause mortality was 1.262 (95 % CI 1.093-1.431) with significant heterogeneity. Subgroup analyses indicated that the pooled HRs of all-cause mortality in patients with mild, moderate and severe OSA were 0.945 (95 % CI 0.810-1.081), 1.178 (95 % CI 0.978-1.378) and 1.601 (95 % CI 1.298-1.902), respectively. OSA severity could be a possible sources of heterogeneity. Existing publication bias produced a minor contribution to effect size.

CONCLUSION

Severe, but not mild to moderate, OSA is significantly associated with increased risk of all-cause mortality.

Obstructive sleep apnea: management considerations in psychiatric patients

Psychiatric disorders and obstructive sleep apnea (OSA) are often comorbid. However, there is limited information on the impact of psychotropic medications on OSA symptoms, on how to manage psychiatric pharmacotherapy in patients presenting with OSA, or on the effectiveness and challenges of OSA treatments in patients with comorbid mental illness. As such, the objective of this article is to provide an overview of some epidemiological aspects of OSA and treatment considerations in the management of OSA in individuals with comorbid psychiatric disorders. Predefined keywords were used to search for relevant literature in electronic databases. Data show that OSA is particularly prevalent in patients with psychiatric disorders. The medical care that patients with these comorbidities require can be challenging, as some of the psychiatric medications used by these patients may exacerbate OSA symptoms. As such, continuous positive airway pressure continues to be the first-line treatment, even in patients with psychiatric comorbidity. However, more controlled studies are required, particularly to determine continuous positive airway pressure compliance in patients with mental illness, the impact of treating OSA on psychiatric symptoms, and the impact of the use of psychotropic medications on OSA symptoms.

Lateral teleradiography of the head as a diagnostic tool used to predict obstructive sleep apnea

OBJECTIVES

To (1) assess the relationship between obstructive sleep apnea (OSA) and craniofacial, pharyngeal anatomy and (2) to submit the recommendations for clinicians for increasing the sensitivity in the diagnostics of OSA.

METHODS

A review of the relevant literature linking OSA in adults with cephalometric analysis was performed. In total, 11 articles with similar procedural criteria were selected. The data were analysed using the Comprehensive Meta-Analysis Software (Biostat Inc., Englewood, NJ) and Statistica 12.0 (StatSoft Inc., Dell Software, Tulsa, OK).

RESULTS

Adults with OSA did not show statistically significant differences in the sagittal and vertical skeletal planes in comparison with the controls (p > 0.05). The patients with OSA had soft palate length, width and area increased accordingly by 4.21, 1.99 mm and 0.86 cm(2), tongue area increased by 2.02 cm(2), the upper posterior pharyngeal space (SPAS) and lower posterior pharyngeal space reduced accordingly by 4.53 and 1.32 mm, mandibular plane to the hyoid bone (MP-H) distance increased by 4.14 mm compared with the controls (p < 0.05). The SPAS parameter of the patients with OSA did not show statistically significant differences between the studies, with the mean value being 5.69 mm.

CONCLUSIONS

Analysed cephalometric data totally supported the concept of soft-tissue abnormalities in subjects with OSA, skeletal-only halfway; MP-H and SPAS being the most reliable parameters. Increased MP-H may serve as a predictor when differentiating normal subjects and patients with OSA. Reduced SPAS width could be a prognostic parameter for suspecting OSA. These two values should be kept in mind by dentists and can also be used as a simple auxiliary method by physicians; nevertheless, it is still underestimated and more studies are needed.

Eight Hours of Nightly Continuous Positive Airway Pressure Treatment of Obstructive Sleep Apnea Improves Glucose Metabolism in Patients with Prediabetes. A Randomized Controlled Trial

RATIONALE

Although obstructive sleep apnea (OSA) is associated with impaired glucose tolerance and diabetes, it remains unclear whether OSA treatment with continuous positive airway pressure (CPAP) has metabolic benefits.

OBJECTIVES

To determine the effect of 8-hour nightly CPAP treatment on glucose metabolism in individuals with prediabetes and OSA.

METHODS

In a randomized controlled parallel group study, 39 participants were randomly assigned to receive either 8-hour nightly CPAP (n = 26) or oral placebo (n = 13). Sleep was polysomnographically recorded in the laboratory on each night. CPAP adherence was ensured by continuous supervision. Participants continued their daily routine activities outside the laboratory. Glucose metabolism was assessed at baseline and after 2 weeks of assigned treatment using both the oral and intravenous glucose tolerance tests. The primary outcome was the overall glucose response as quantified by the area under the curve for glucose during 2-hour oral glucose tolerance testing. Secondary outcomes included fasting and 2-hour glucose and insulin, the area under the curves for insulin and insulin secretion, norepinephrine, insulin sensitivity, acute insulin response to glucose, and 24-hour blood pressure.

MEASUREMENTS AND MAIN RESULTS

The overall glucose response was reduced (treatment difference: -1,276.9 [mg/dl] · min [95% confidence interval, -2,392.4 to -161.5]; P = 0.03) and insulin sensitivity was improved (treatment difference: 0.77 [mU/L](-1) · min(-1) [95% confidence interval, 0.03-1.52]; P = 0.04) with CPAP as compared with placebo. Additionally, norepinephrine levels and 24-hour blood pressure were reduced with CPAP as compared with placebo.

CONCLUSIONS

In patients with prediabetes, 8-hour nightly CPAP treatment for 2 weeks improves glucose metabolism compared with placebo. Thus, CPAP treatment may be beneficial for metabolic risk reduction. Clinical trial registered with www.clinicaltrials.gov (NCT 01156116).

Obstructive sleep apnoea syndrome

Obstructive sleep apnoea syndrome (OSAS) is a common clinical condition in which the throat narrows or collapses repeatedly during sleep, causing obstructive sleep apnoea events. The syndrome is particularly prevalent in middle-aged and older adults. The mechanism by which the upper airway collapses is not fully understood but is multifactorial and includes obesity, craniofacial changes, alteration in upper airway muscle function, pharyngeal neuropathy and fluid shift towards the neck. The direct consequences of the collapse are intermittent hypoxia and hypercapnia, recurrent arousals and increase in respiratory efforts, leading to secondary sympathetic activation, oxidative stress and systemic inflammation. Excessive daytime sleepiness is a burden for the majority of patients. OSAS is also associated with cardiovascular co-morbidities, including hypertension, arrhythmias, stroke, coronary heart disease, atherosclerosis and overall increased cardiovascular mortality, as well as metabolic dysfunction. Whether treating sleep apnoea can fully reverse its chronic consequences remains to be established in adequately designed studies. Continuous positive airway pressure (CPAP) is the primary treatment modality in patients with severe OSAS, whereas oral appliances are also widely used in mild to moderate forms. Finally, combining different treatment modalities such as CPAP and weight control is beneficial, but need to be evaluated in randomized controlled trials. For an illustrated summary of this Primer, visit: http://go.nature.com/Lwc6te.

Impaired functional capacity predicts mortality in patients with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is associated with increased mortality, for which impaired functional capacity (IFC) has been established as a surrogate. We sought to assess whether IFC is associated with increased mortality in patients with OSA and whether IFC is predictive of increased mortality after accounting for coronary artery disease.

METHODS

Patients with OSA who underwent both polysomnography testing and exercise stress echocardiogram were selected. Records were reviewed retrospectively for demographics, comorbidities, stress echocardiographic parameters, and polysomnography data. Univariable and multivariable logistic regression analysis was used to evaluate the association between IFC and overall mortality. We then evaluated the variables associated with IFC in the overall population and in the subgroup with normal Duke treadmill score (DTS).

RESULTS

In our cohort, 404 (26%) patients had IFC. The best predictors of IFC were female sex, history of smoking, ejection fraction less than 55, increased body mass index, presence of comorbidities, abnormal exercise echocardiogram, abnormal heart rate recovery, and abnormal DTS. Compared with those without IFC, patients with IFC were 5.1 times more likely to die (odds ratio [OR], 5.1; 95% confidence interval [CI], 2.5-10.5; P < 0.0001) by univariate analysis and 2.7 times more likely to die (OR, 2.7; 95% CI, 1.2-6.1; P = 0.02) by multivariate analysis, when accounting for heart rate recovery, DTS, and sleep apnea severity. Among those without coronary artery disease, patients with IFC were at significantly increased risk of mortality (OR, 4.3; 95% CI, 1.35-13.79; P = 0.0088) compared with those with preserved functional capacity.

CONCLUSIONS

In our OSA population, IFC was a strong predictor of increased mortality. Among those with normal DTS, IFC identified a cohort at increased risk of mortality.

Use of continuous positive airway pressure for sleep apnea in the treatment of hypertension

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) and hypertension are highly prevalent and treatable conditions that often coexist and both contribute to an increased cardiovascular risk. The ability of continuous positive airway pressure (CPAP) to improve blood pressure in hypertensive patients with OSA is debated. This review highlights findings from recent studies that have investigated the impact of CPAP on blood pressure in patients with OSA.

RECENT FINDINGS

Comparing the results of various studies is complicated by important methodological differences among them. In hypertensive patients with OSA, treatment with CPAP improves blood pressure to a smaller degree than that derived from antihypertensive medication. Patients with more severe OSA and with greater adherence to CPAP are likely to gain the most benefit from the therapy.

SUMMARY

CPAP should be used in combination with antihypertensive medications in hypertensive patients with OSA. CPAP has the additional benefits of restoring nocturnal dipping and improving arterial stiffness, thus potentially influencing cardiovascular morbidity in these high-risk patients.

Comorbidity of diabetes and obstructive sleep apnea in hospitalized patients

Obstructive sleep apnea (OSA) and type 2 diabetes are two morbidities commonly encountered in the hospitalized setting. Both diseases will present with an array of complications if not managed in a timely, competent manner. However, a growing body of evidence suggests a link between these two pathologies. It is our hope that through careful review of the literature, we may generate heightened awareness of the OSA/diabetes comorbidity. Through better understanding of these conditions and their interactions, we may insure efficient management in the clinical setting and prevent exacerbation of common complications.

Pharmacological treatment of sleep disorders and its relationship with neuroplasticity

Sleep and wakefulness are regulated by complex brain circuits located in the brain stem, thalamus, subthalamus, hypothalamus, basal forebrain, and cerebral cortex. Wakefulness and NREM and REM sleep are modulated by the interactions between neurotransmitters that promote arousal and neurotransmitters that promote sleep. Various lines of evidence suggest that sleep disorders may negatively affect neuronal plasticity and cognitive function. Pharmacological treatments may alleviate these effects but may also have adverse side effects by themselves. This chapter discusses the relationship between sleep disorders, pharmacological treatments, and brain plasticity, including the treatment of insomnia, hypersomnias such as narcolepsy, restless legs syndrome (RLS), obstructive sleep apnea (OSA), and parasomnias.

Sleep apnea is not associated with worse outcomes in kidney transplant recipients

Obstructive sleep apnea(OSA) is one of the most common sleep disorders in kidney transplant recipients, however its long-term consequences have only rarely been investigated. Here, we hypothesized that the presence of OSA would be associated with higher risk of mortality and faster decline of graft function in kidney transplant recipients. In a prospective cohort study 100 prevalent kidney transplant recipients who underwent one-night polysomnography at baseline and were followed for a median 75 months. Generalized linear mixed-effects models and Cox regression models were used to assess the association between OSA and the rate of progression of chronic kidney disease(CKD) and mortality. The estimated slopes of estimated glomerular filtration rate(eGFR) in patients with and without OSA were compared using a two-stage model of eGFR change including only OSA as a variable. In this model patients with OSA (eGFR versus time was −0.93 ml/min/1.73 m²/yr(95%CI:−1.75 to−0.11) had a similar slope as compared to patients without OSA(eGFR versus time was −1.24 ml/min/1.73 m²/yr(95%CI: −1.67 to −0.81). In unadjusted Cox proportional regression analyses OSA was not associated with higher all-cause mortality risk (Hazard Ratio(HR) = 1.20; 95% Confidence Interval(CI): 0.50–2.85). No association was found between the presence of OSA and the rate of progression of CKD or all-cause mortality in prevalent kidney transplant recipients.

Fighting insomnia and battling lethargy: the yin and yang of palliative care

There is an interdependent relationship between insomnia and fatigue in the medical literature, but both remain distinct entities. Insomnia entails problematic sleep initiation, maintenance, or restoration with an accompanying decrease in perceived daytime function. Lethargy is a symptom that has a wide differential diagnosis that heavily overlaps with cancer-related fatigue; however, insomnia may contribute to worsened fatigue and lethargy in cancer patients. Insomnia is a major risk factor for mood disturbances such as depression, which may also contribute to lethargy in this at-risk population. The pathophysiology of fatigue and insomnia is discussed in this review, including their differential diagnoses as well as the emerging understanding of the roles of neurotransmitters, branched-chain amino acids, and inflammatory cytokines. Treatment approaches for insomnia and fatigue are also discussed and reviewed, including the role of hypnotics, psychotropics, hormonal agents, and alternative therapies.

Can mitochondrial dysfunction be a predictive factor for oxidative stress in patients with obstructive sleep apnea?

Mitochondrial dysfunction reflects a lifelong cumulative burden of cellular damage, and a decrease in mitochondrial DNA (mtDNA) copy number is associated with oxidative stress and chronic inflammation. The goal of this study was to assess whether mitochondrial dysfunction and a decrease in mtDNA copy number are common features of patients with obstructive sleep apnea syndrome (OSA). We compared mtDNA copy number between 20 healthy volunteers and 20 patients with OSA and investigated whether a significant attenuation of mtDNA copy number was observed in genomic DNA isolated from whole blood of OSA patients. Our observations lead to the hypothesis that mtDNA copy number is lower in whole blood DNA of OSA subjects and might be related to OSA severity, reflecting excessive oxidative stress in patients with OSA.

Metabolic activity of the tongue in obstructive sleep apnea. A novel application of FDG positron emission tomography imaging

RATIONALE

The metabolic activity of the tongue is unknown in patients with obstructive sleep apnea (OSA). Tongue electromyographic (EMG) activity is increased in patients with OSA. This increase in tongue EMG activity is thought to be related to either increased neuromuscular compensation or denervation with subsequent reinnervation of the muscle fibers. Increased glucose uptake in the tongue would support increased neuromuscular compensation, whereas decreased glucose uptake in the tongue would support denervation with subsequent reinnervation of the muscle fibers.

OBJECTIVES

To investigate the metabolic activity of the genioglossus and control upper airway muscles in obese patients with sleep apnea compared with obese control subjects.

METHODS

Obese subjects with and without OSA underwent a standard overnight sleep study to determine an apnea-hypopnea index. Each subject had a positron emission tomography with [(18)F]-2-fluoro-2-deoxy-D-glucose scan in addition to noncontrast computed tomography or magnetic resonance imaging. Glucose uptake was quantified within upper airway tissues with the standardized uptake value.

MEASUREMENTS AND MAIN RESULTS

We recruited 30 obese control subjects (apnea-hypopnea index, 4.7 ± 3.1 events per hour) and 72 obese patients with sleep apnea (apnea-hypopnea index, 43.5 ± 28.0 events per hour). Independent of age, body mass index, sex, and race, patients with OSA had significantly reduced glucose uptake in the genioglossus (P = 0.03) in comparison with obese normal subjects. No differences in standardized uptake value were found in the control muscles (masseter [P = 0.38] and pterygoid [P = 0.70]) and subcutaneous fat deposits (neck [P = 0.44] and submental [P = 0.95]) between patients with OSA and control subjects.

CONCLUSIONS

There was significantly reduced glucose uptake in the genioglossus of patients with sleep apnea in comparison with obese normal subjects with [(18)F]-2-fluoro-2-deoxy-D-glucose positron emission tomography imaging. The reduction in glucose uptake was likely secondary to alterations in tongue muscle fiber-type or secondary to chronic denervation. The reduced glucose uptake argues against the neuromuscular compensation hypothesis explaining the increase in tongue EMG activity in obese patients with OSA.

Carotid body denervation prevents fasting hyperglycemia during chronic intermittent hypoxia

Obstructive sleep apnea causes chronic intermittent hypoxia (IH) and is associated with impaired glucose metabolism, but mechanisms are unknown. Carotid bodies orchestrate physiological responses to hypoxemia by activating the sympathetic nervous system. Therefore, we hypothesized that carotid body denervation would abolish glucose intolerance and insulin resistance induced by chronic IH. Male C57BL/6J mice underwent carotid sinus nerve dissection (CSND) or sham surgery and then were exposed to IH or intermittent air (IA) for 4 or 6 wk. Hypoxia was administered by decreasing a fraction of inspired oxygen from 20.9% to 6.5% once per minute, during the 12-h light phase (9 a.m.-9 p.m.). As expected, denervated mice exhibited blunted hypoxic ventilatory responses. In sham-operated mice, IH increased fasting blood glucose, baseline hepatic glucose output (HGO), and expression of a rate-liming hepatic enzyme of gluconeogenesis phosphoenolpyruvate carboxykinase (PEPCK), whereas the whole body glucose flux during hyperinsulinemic euglycemic clamp was not changed. IH did not affect glucose tolerance after adjustment for fasting hyperglycemia in the intraperitoneal glucose tolerance test. CSND prevented IH-induced fasting hyperglycemia and increases in baseline HGO and liver PEPCK expression. CSND trended to augment the insulin-stimulated glucose flux and enhanced liver Akt phosphorylation at both hypoxic and normoxic conditions. IH increased serum epinephrine levels and liver sympathetic innervation, and both increases were abolished by CSND. We conclude that chronic IH induces fasting hyperglycemia increasing baseline HGO via the CSN sympathetic output from carotid body chemoreceptors, but does not significantly impair whole body insulin sensitivity.

Medication effects on sleep and breathing

Sleep respiration is regulated by circadian, endocrine, mechanical and chemical factors, and characterized by diminished ventilatory drive and changes in Pao2 and Paco2 thresholds. Hypoxemia and hypercapnia are more pronounced during rapid eye movement. Breathing is influenced by sleep stage and airway muscle tone. Patient factors include medical comorbidities and body habitus. Medications partially improve obstructive sleep apnea and stabilize periodic breathing at altitude. Potential adverse consequences of medications include precipitation or worsening of disorders. Risk factors for adverse medication effects include aging, medical disorders, and use of multiple medications that affect respiration.

Risk assessment for obstructive sleep apnea and anxiety in a Pakistani population with coronary artery disease

PURPOSE

Previous studies in the western world have reported the possible association of obstructive sleep apnea (OSA) with anxiety and cardiovascular diseases. However, the data from developing countries such as Pakistan remains scarce in this regard. The main aim of this study was to investigate the prevalence of coronary artery disease (CAD) patients who are at high risk of OSA and to determine the association between the risk of OSA and levels of anxiety.

METHODS

The sample population consisted of 400 participants including 200 patients, who had been previously diagnosed with CAD, and 200 healthy controls. The 200 CAD patients were approached for inclusion in the study on their follow-ups after their acute symptoms had subsided. The patients were interviewed after a mean time period of 13 weeks post event. All patients with lung disease or respiratory infection were excluded from the study. The risk of OSA was determined using Berlin questionnaire, while the levels of anxiety were measured by Beck anxiety inventory scale (BAI).

RESULTS

More than half (n = 104) of the CAD patients were at high risk of OSA while majority (n = 168) of the healthy controls were at low risk. The high risk of OSA was significantly (P < 0.0001) more prevalent in CAD patients compared with controls. It was also observed that the patients who were at high risk of OSA, among both cases and controls, had significantly (P values <0.001) higher levels of anxiety.

CONCLUSION

A significant proportion of CAD patients are at high risk of OSA in our region. Moreover, OSA is also associated with greater levels of anxiety in both healthy people and CAD patients.

Prevalence and Correlates of Insomnia and Excessive Sleepiness in Adults with Obstructive Sleep Apnea Symptoms

This study investigated the prevalence and correlates of insomnia and excessive sleepiness in adults presenting symptoms of obstructive sleep apnea (OSA) in the general population. Randomly selected participants ( N = 1,502; 50.7% men, 49.3% women), ages 40 to 70 yr. ( M = 53.6, SD = 8.5) were interviewed over the telephone. Insomnia and excessive sleepiness (hypersomnia) were assessed with the Bergen Insomnia Scale and the Epworth Sleepiness Scale, respectively. OSA symptoms were identified by self- or spouse reports on snoring, breathing cessations during sleep, and being tired or sleepy. The prevalence of OSA was 6.2%. Among these participants with OSA, 57.6% reported insomnia and 30.1% reported excessive sleepiness. Furthermore, OSA symptoms were associated with self-reported obesity, hypertension, diabetes, and depression, but only in participants with comorbid insomnia or excessive sleepiness.

Clinical services for obstructive sleep apnea patients in pharmacies: the Australian experience

BACKGROUND

In Australia, certain pharmacies have undertaken a role in the management of the chronic sleep disorder, obstructive sleep apnea. The perspectives of pharmacy staff involved in this niche clinical service have never been formally collated on a national scale. The experiences of Australian pharmacies could provide a template for pharmacies in other health systems to adopt similar roles.

OBJECTIVE

To provide an overview of the perspectives of pharmacy staff involved in Continuous Positive Airway Pressure (CPAP) and sleep apnea-related services. Specifically, to describe clinical and structural elements, explore benefits and barriers, investigate viability, and gauge perspectives on future directions.

SETTING

Australian community pharmacies involved in CPAP and sleep apnea-related services.

METHOD

Cross-sectional mail survey. A questionnaire designed to meet the study objectives was developed by the researchers and mailed to all pharmacies in Australia providing CPAP services during the period of study recruitment. Pharmacies were identified through the distributor lists of the major CPAP manufacturers and a comprehensive Internet search. Non-responders were contacted in two subsequent recruitment rounds.

MAIN OUTCOME MEASURE

Self-reported sleep apnea service specifics.

RESULTS

A response rate of 55 % was achieved (n = 106 questionnaires valid for data entry). Benefits of providing a CPAP service included meeting patient and community needs, and professional satisfaction. Barriers included the cost of CPAP equipment to patients and lack of time. A majority of pharmacies (71 %) reported the service was financially viable despite most (63 %) not charging a 'fee for service.' Respondents expressed the view that CPAP provision should remain a specialist area of practice within the pharmacy profession. Key areas identified for improvement within the service were: (1) Staff training and knowledge (2) Promotion of the service and increasing public awareness (3) Infrastructure and expansion (4) Inter-professional collaboration and communication (5) Patient follow-up.

CONCLUSION

The provision of CPAP and sleep apnea-related services can be a viable and rewarding experience for pharmacists. The role may need to remain a specialised area for those willing to invest significantly in the service--in time, staff, resources and finances.

Mandibular advancement device and CPAP upon cardiovascular parameters in OSA

PURPOSE

This study aims to compare the effects of a mandibular advancement device (MAD) with continuous positive airway pressure (CPAP) treatment for obstructive sleep apnea (OSA) on blood pressure (BP), oxidative stress, and heart rate variability (HRV) in a randomized, crossed-over, single-blind, and controlled trial.

METHODS

Twenty-nine moderate-to-severe adult OSA patients underwent MAD, CPAP, and placebo oral appliance treatment. Polysomnography, Epworth sleepiness scale, 24-h ambulatory BP monitoring, oxidative stress parameters (malondialdehyde, catalase, superoxide dismutase, vitamins C, E, B6, B12, folate, homocysteine, uric acid), and HRV were assessed at baseline and after 1 month of each treatment. Diaries were used to evaluate compliance for devices and a pressure-time meter for CPAP.

RESULTS

Both active treatments resulted in decreases in apnea and hypopnea index and Epworth sleepiness scale; CPAP showed a greater effect. Frequency of diastolic BP dipping was higher in the MAD group compared with the CPAP group. A significant drop from baseline levels for catalase activity was observed after MAD. For HRV, there was a significant decrease in total power at night with CPAP and MAD compared with POA, and a decrease in index of sleep autonomic variation with MAD compared with baseline levels. Compliance rates were higher with MAD rather than CPAP.

CONCLUSIONS

Even though CPAP proved to be more effective at attenuating OSA, better compliance with MAD favored the reduction of one of the enzymes which participates in oxidative stress and better autonomic modulation during sleep.

Diagnosis and treatment of sleep apnoea in women with schizophrenia

BACKGROUND

Obstructive sleep apnoea (OSA) is often overlooked in the context of schizophrenia because its hallmark, daytime sleepiness, is so easily attributable to antipsychotic drugs. This is a special problem for women.

AIMS

To underscore the importance of diagnosing and treating OSA in women with schizophrenia.

METHODS

A review of the recent literature (search terms: Obstructive Sleep Apnoea; Schizophrenia; Women (or Gender); Obesity; Antipsychotics; Continuous Positive Airway Pressure (CPAP)) as it applies to a composite case vignette taken from the files of a specialty clinic that treats women with psychosis.

RESULTS

The rate of OSA in women who are both obese and postmenopausal is very similar to that of men. Family history, smoking, and the use of tobacco, alcohol and of antipsychotic medication increase the risk. Despite reluctance, patients with schizophrenia generally agree to undergo sleep studies. Compliance with CPAP is difficult, but can be aided by the physician and is, on the whole, relatively high in women. CPAP improves sleep parameters and may also improve cardiometabolic and cognitive indices, although this still needs to be more fully researched.

CONCLUSION

Schizophrenia and untreated OSA are both associated with high mortality rates in women as well as men.