Sleep apnea disorders. Introduction to sleep and sleep disorders

Elder people can be more susceptible to the association between short-term ambient air pollution and sleep disorder outpatient visits: a time-series study

Sleep disorders attract increasing concerns. However, the evidence of the association between ambient air pollution and sleep disorders is limited. Therefore, our aim was to determine the association between short-term air pollution exposure and outpatient visits for sleep disorders in Xi'an, the largest city in Northwest China. Baseline outpatient data of daily sleep disorders between 2011 and 2013 were collected. Quasi-Poisson distribution was applied by adjusting the day of the week and weather conditions. A total of 49,282 sleep disorder outpatient visits were recorded. The most significant association between air pollutants and outpatient visits was observed on concurrent day: per 10 μg/m3 increase of NO2, SO2, and PM10 at lag 0 corresponded to increased outpatient sleep disorder visits at 0.22% (95% CI: 0.03%, 0.42%), 1.53% (95% CI: 0.53, 2.53%), and 2.57% (95% CI: 1.33%, 3.82%), respectively. As for gender-specific analysis, there was no statistically significant difference between males and females. The result of season-specific analysis showed no statistically significant difference between warm seasons and cool seasons, either. As for age-specific analysis, obvious associations were observed in 20-40 age group (NO2) and > 40 age group (PM10 and SO2), while no evident association was found for the young age group (< 20 years old). Conclusively, short-term exposure to air pollutants, especially gaseous air pollutants, might increase the risk of sleep disorders, and such association appears to be more obvious in elder people. We provide novel data that there may be age differences in the relationship between short-term air pollution exposure and sleep disorders.

Sleep as a random walk: a super-statistical analysis of EEG data across sleep stages

In clinical practice, human sleep is classified into stages, each associated with different levels of muscular activity and marked by characteristic patterns in the EEG signals. It is however unclear whether this subdivision into discrete stages with sharply defined boundaries is truly reflecting the dynamics of human sleep. To address this question, we consider one-channel EEG signals as heterogeneous random walks: stochastic processes controlled by hyper-parameters that are themselves time-dependent. We first demonstrate the heterogeneity of the random process by showing that each sleep stage has a characteristic distribution and temporal correlation function of the raw EEG signals. Next, we perform a super-statistical analysis by computing hyper-parameters, such as the standard deviation, kurtosis, and skewness of the raw signal distributions, within subsequent 30-second epochs. It turns out that also the hyper-parameters have characteristic, sleep-stage-dependent distributions, which can be exploited for a simple Bayesian sleep stage detection. Moreover, we find that the hyper-parameters are not piece-wise constant, as the traditional hypnograms would suggest, but show rising or falling trends within and across sleep stages, pointing to an underlying continuous rather than sub-divided process that controls human sleep. Based on the hyper-parameters, we finally perform a pairwise similarity analysis between the different sleep stages, using a quantitative measure for the separability of data clusters in multi-dimensional spaces.

To improve our understand of how EEG activity reflects the dynamics of human sleep, Metzner et al. use human EEG data and superstatistical analysis to demonstrate that each sleep stage has a characteristic distribution and temporal correlation function of raw EEG signals. They also show that the hyper-parameters controlling the EEG signals have characteristic, sleep-stage-dependent distributions, which can be exploited for a simple Bayesian sleep stage detection.

Mechanical properties of the upper airway

The importance of the upper airway (nose, pharynx, and larynx) in health and in the pathogenesis of sleep apnea, asthma, and other airway diseases, discussed elsewhere in the Comprehensive Physiology series, prompts this review of the biomechanical properties and functional aspects of the upper airway. There is a literature based on anatomic or structural descriptions in static circumstances, albeit studied in limited numbers of individuals in both health and disease. As for dynamic features, the literature is limited to studies of pressure and flow through all or parts of the upper airway and to the effects of muscle activation on such features; however, the links between structure and function through airway size, shape, and compliance remain a topic that is completely open for investigation, particularly through analyses using concepts of fluid and structural mechanics. Throughout are included both historically seminal references, as well as those serving as signposts or updated reviews. This article should be considered a resource for concepts needed for the application of biomechanical models of upper airway physiology, applicable to understanding the pathophysiology of disease and anticipated results of treatment interventions.

PSYCHOSOCIAL FACTORS IN PATIENTS WITH CHRONIC KIDNEY DISEASE: Sleepiness, Sleeplessness, and Pain in End-Stage Renal Disease: Distressing Symptoms for Patients

Symptoms are increasingly recognized as problematic for patients with end-stage renal disease (ESRD) treated with dialysis. Sleep disorders are common in ESRD patients treated with dialysis and are associated with patients' perceptions of quality of life, assessed by diverse measures, as well as depressive affect. Sleep disorders appear to be equally prevalent in peritoneal dialysis (PD) and hemodialysis (HD) patients. Treatment for sleep disorders in dialysis patients depends on establishing the diagnosis, often in a sleep laboratory, using polysomnography. Reversing coexistent medical and psychological disorders is important. The sleep apnea syndrome (SAS) can be treated with continuous positive airway pressure in dialysis patients, but conventional hemodialytic techniques have little effect on its severity. In contrast, nocturnal HD and transplantation appear to have important beneficial effects on sleep disordered breathing in ESRD patients. Although pain has been appreciated as a problem for ESRD patients for more than 20 years, few studies exist on this subject. Pain appears to be an underappreciated problem for ESRD patients. More research must be performed on the problem of pain in patients with chronic kidney disease (CKD).

Pain as a mediator of sleep problems in arthritis and other chronic conditions

OBJECTIVE

To examine the associations between arthritis and insomnia symptoms and unrefreshing sleep, as well as the role of pain as a mediator of these relationships.

METHODS

Analyses were conducted on the cross-sectional, nationally representative, weighted sample of adults > or =18 years of age (n = 118,336) in the 2000/2001 Canadian Community Health Survey. Four logistic regression models were estimated for each sleep problem (model 1: arthritis only; model 2: model 1 + sociodemographic characteristics, lifestyle factors, and other chronic conditions; model 3: model 2 + mental health [stress, depression]; and model 4: model 3 + pain). Mediation by pain was quantified by the percentage change in the effect of arthritis on a particular sleep problem by comparing models 3 and 4.

RESULTS

The prevalence of insomnia symptoms and unrefreshing sleep in persons with arthritis was 24.8% and 11.9%, respectively. These estimates are twice as high as those for persons without arthritis. In multivariate regression analyses, the addition of pain decreased the effect of arthritis by 53% (insomnia symptoms) and 64% (unrefreshing sleep). The effect of arthritis was still statistically significant in these models, suggesting that pain is a partial mediator of these relationships.

CONCLUSION

Insomnia symptoms and unrefreshing sleep affect a considerable proportion of individuals with arthritis. Pain mediates a substantial amount of the relationship between arthritis and sleep problems. Better pain management could significantly improve sleep in individuals with arthritis.

Narcolepsy: clinical features, new pathophysiologic insights, and future perspectives

Narcolepsy is characterized by excessive daytime sleepiness and abnormal manifestations of rapid eye movement sleep such as cataplexy. The authors review the clinical features of narcolepsy, including epidemiology, symptoms, diagnosis, and treatment, in detail. Recent findings show that a loss of hypocretin-producing neurons lies at the root of the signs and symptoms of narcolepsy. The authors review the current state of knowledge on hypocretin anatomy, physiology, and function with special emphasis on the research regarding the hypocretin deficiency in narcolepsy, which may also explain associated features of the disorder, such as obesity. Lastly, they discuss some future perspectives for research into the pathophysiology of sleep/wake disorders, and the potential impact of the established hypocretin deficiency on the diagnosis and treatment of narcolepsy.

'I don't have any energy': The experience of fatigue in young adult survivors of childhood cancer

Although it is speculated that fatigue occurs equally in adults, children and adolescents with cancer, little research exists to substantiate this view. Evidence that fatigue continues after treatment is limited in both the adult and paediatric oncology literature. Due to the current lack of knowledge, more information on the phenomenology of fatigue of childhood cancer survivors is desirable. Therefore a study was conducted to explore the concept of fatigue from a survivor's perspective. A semi-structured interview was conducted with a purposeful sample of 35 long-term survivors of childhood cancer who reported feeling extremely fatigued. The topics which were covered during the interview included the nature, onset and pattern of fatigue, sleep rest pattern, what helps with fatigue and what does not help, and the impact of fatigue on their daily life. Most survivors who were diagnosed with cancer in their adolescence identified fatigue as a significant side-effect of the treatment. The majority of survivors who were toddlers or preschooler at the time of cancer treatment mentioned that, as far as they could recall, they had suffered from fatigue their entire life. The course of fatigue during the day differed among the survivors, although the majority reported to be fatigued when waking up in the morning. None of the survivors reported sleep problems. Many survivors slept 9 hours or more. Fatigue was defined by all respondents as having a negative impact on their daily lives. Findings revealed that fatigue is a serious problem for some young adult survivors of childhood cancer and affects many aspects of quality of life.

Anxiety disorders and insomnia in geriatric patients

Anxiety and insomnia are among the more frequently encountered problems in geriatric cases. The effective clinical approach identifies underlying diagnostic syndromes or general medical conditions. An integrated approach to management combines pharmacotherapy and behavioral interventions as appropriate. Overall the prognosis for most patients is excellent.

Disordered sleep and noncompliance in a patient with end-stage renal disease

Sleep disorders are relatively common in patients with end-stage renal disease, but the diagnosis may be difficult to establish because of the similarity of uremic symptoms to those of the sleep apnea syndrome. After excluding anatomic and metabolic disorders associated with excessive sleepiness and disordered breathing in sleep and after ensuring that the patient is receiving adequate dialysis, the sleep disorder should be diagnosed using polysomnography. Continuous positive pressure airway breathing is an effective treatment for hemodialysis patients with obstructive sleep apnea syndrome, but the use of this machinery requires patient compliance, as does the delivery of an adequate amount of dialysis. The difficulties adjusting to end-stage renal disease requiring dialysis can be multiplied by the coexistence of a sleep disorder that requires some ventilatory assistance at night; the case presented in this article characterizes precisely that circumstance.

Sleep studies and supportive ventilatory treatment in patients with congenital muscle disorders

Eight ambulant children aged 6-13 years, four with congenital myopathy, two with congenital muscular dystrophy and two with the rigid spine syndrome, presented with recurrent chest infections, morning headaches, shallow breathing at night, or respiratory failure. Polysomnography confirmed the presence of nocturnal hypoxaemia with oxygen saturation on average less than 90% for 49% of sleep and less than 80% for 19% of sleep accompanied with severe hypoventilation. Additionally there was sleep disturbance characterised by an increased number of wake epochs from deep sleep (in comparison to 10 non-hypoxaemic subjects). The severity of sleep hypoxaemia did not correlate with symptoms. Treatment with night time nasal ventilation was started and repeat polysomnography showed normal overnight oxygen saturation and a reduced number of wake epochs during deep sleep. It is important to be vigilant for sleep hypoventilation in these patients and sleep studies should be part of the routine respiratory evaluation. Treatment with nasal ventilation is effective in reversing the nocturnal respiratory failure without significant disturbance to life style.

Freezing of gait in Parkinson's disease is improved by treatment with weak electromagnetic fields

Freezing, a symptom characterized by difficulty in the initiation and smooth pursuit of repetitive movements, is a unique and well known clinical feature of Parkinson's disease (PD). It usually occurs in patients with long duration and advanced stage of the disease and is a major cause of disability often resulting in falling. In PD patients freezing manifests most commonly as a sudden attack of immobility usually experienced during walking, attempts to turn while walking, or while approaching a destination. Less commonly it is expressed as arrest of speech or handwriting. The pathophysiology of Parkinsonian freezing, which is considered a distinct clinical feature independent of akinesia, is poorly understood and is believed to involve abnormalities in dopamine and norepinephrine neurotransmission in critical motor control areas including the frontal lobe, basal ganglia, locus coeruleus and spinal cord. In general, freezing is resistant to pharmacological therapy although in some patients reduction or increase in levodopa dose may improve this symptom. Three medicated PD patients exhibiting disabling episodes of freezing of gait are presented in whom brief, extracerebral applications of pulsed electromagnetic fields (EMFs) in the picotesla range improved freezing. Two patients had freezing both during "on" and "off" periods while the third patient experienced random episodes of freezing throughout the course of the day. The effect of each EMFs treatment lasted several days after which time freezing gradually reappeared, initially in association with "off" periods. These findings suggest that the neurochemical mechanisms underlying the development of freezing are sensitive to the effects of EMFs, which are believed to improve freezing primarily through the facilitation of serotonin (5-HT) neurotransmission at both junctional (synaptic) and nonjunctional neuronal target sites.

Resolution of partial cataplexy in multiple sclerosis by treatment with weak electromagnetic fields

Cataplexy, an ancillary symptom of narcolepsy, involves the sudden loss of muscle tone without altered consciousness usually brought on by sudden excitement or emotional influence and extreme exertions (Guilleminault et al., 1974; Parks et al., 1974; Guilleminault, 1976; Aldrich, 1992; 1993; Scrima, 1981; Baker, 1985). Attacks of generalized cataplexy produce complete atonic, areflexic partial or complete paralysis of striated muscles commonly involving the leg muscles resulting in collapse of the knees and falling while milder forms often termed partial cataplexy may manifest by sagging of the face, eyelid, or jaw, dysarthria, blurred vision, drooping of the head, weakness of an arm or leg, buckling at the knees, or simply a momentary sensation of weakness that is imperceptible to observers (Guilleminault, 1976; Aldrich, 1993). The duration of cataplexy is usually a few seconds, although severe episodes can last several minutes and rarely several hours or days in the case of "status cataplecticus" (Parkes et al., 1974; Guilleminault, 1976; Billiard & Cadilhac, 1985; Aldrich, 1992; 1993). This report concerns a 51 year old man with chronic progressive multiple sclerosis who exhibited daily episodes of partial cataplexy which resolved within 3 weeks after he received treatment with picotesla electromagnetic fields.

The pineal gland, cataplexy, and multiple sclerosis

Since the discovery of melatonin as the principal hormone of the pineal gland in 1963, scientists have come to recognize that melatonin is a "master hormone" involved in the control of circadian rhythms and other biological functions. Although little is known about the influence of the pineal gland on motor control, important clues may be obtained by considering the pattern of melatonin secretion during the sleep cycles and particularly during rapid eye movement (REM) sleep when melatonin plasma levels are at their lowest. Since REM sleep is characterized by the occurrence of profound atonia which results in an almost complete paralysis of striated muscles, it is suggested that there might be a causal relationship between inhibition of melatonin secretion during REM sleep and the development of REM sleep atonia. This relationship is supported by the findings that melatonin regulates the activity of brainstem serotonin (5-HT) neurons which characteristically cease to fire during REM sleep and which faciliate the development of REM sleep atonia. Moreover, as the muscular atonia of REM sleep is physiologically and pharmacologically indistinguishable from cataplexy, it is possible that the pineal gland also influences to the development of cataplexy. Cataplexy is an ancillary symptom of narcolepsy and also occurs in multiple sclerosis (MS). In fact, it is believed that several of the neurological symptoms experienced by patients with MS such as weakness in the legs, feeling of collapsing knees, paroxysmal sudden falling, weakness in the neck, extreme fatigue, intermittent paresthesias, slurring of speech and intermittent blurring of vision, which often are exacerbated by stress and other emotional influences, may reflect the manifestations of cataplexy. Thus, several of the clinical features of MS may reflect a dissociated state of wakefulness and sleep and may improve by the administration of anticataplectic drugs.

Changes in diaphragmatic EMG activity during sleep in space

It remains unknown how increased upper airway resistance (UAR) during sleep could be a function of gravity. We therefore conducted quantitative evaluation of the gravitational influence on diaphragmatic EMG activity (EMGdi) in an astronaut to estimate the effect of UAR in space. EMGdi was recorded by paired surface electrodes on the ground (control, C) and abroad a short-term space mission (space, S) for 30 consecutive h. Mean EMGdi recorded during quiet breathing in wakefulness was assigned the value of 100. EMGdi in C was significantly enhanced in all sleep stages compared with that while awake in the supine position (mean +/- SD, 230 +/- 23.2% in non-rapid eye movement (non-REM) Stage II, 233 +/- 13.8 in slow-wave sleep, and 233 +/- 40.0 in REM sleep versus 100 +/- 17.3 in wakefulness, p < 0.001). In contrast, there was no statistical difference in EMGdi in S between awake and any non-REM sleep stage (mean +/- SD, 100 +/- 20.5% in wakefulness versus 103 +/- 16.9 in non-REM Stage II and 100 +/- 14.8 in slow-wave sleep; NS). However, EMGdi in REM sleep in S was statistically greater (132 +/- 28.3%) than that during wakefulness or any other sleep stage in space (p < 0.001). Therefore, gravity may play a much more significant role in the normal healthy human in the increased upper airway resistance during sleep than the relative atonia of the upper airway muscles.

Sleep apnea in male patients with the fibromyalgia syndrome

PURPOSE

Fibromyalgia is a common pain syndrome that is often associated with sleep disturbances. The most characteristic pattern noted on formal sleep study is alpha-wave intrusion on delta-wave sleep. This nonrestorative sleep pattern may be endogenous, or caused by any of a number of sleep disturbances. Our goal was to determine the frequency of sleep apnea and its relationship to a nonrestorative sleep pattern in our patients with fibromyalgia syndrome.

PATIENTS AND METHODS

All new fibromyalgia patients seen in the Rheumatology Clinic at Fitzsimons Army Medical Center were screened using history and physical examination for suspicion of sleep apnea. When this condition was suspected, the patients underwent formal polysomnography to delineate any sleep disturbance.

RESULTS

Four of 92 women, and 13 of 25 men with the new diagnosis of fibromyalgia syndrome underwent polysomnography. Of the women, 2.2% (2 of 92) had significant sleep apnea at formal evaluation; both were obese and had obstructive findings. In contrast, 44% (11 of 25) of the men had significant sleep apnea.

CONCLUSIONS

Sleep apnea is not a significant cause of fibromyalgia symptoms in females. In male patients with fibromyalgia, sleep apnea was observed in a large percentage. Fibromyalgia may be a marker for occult sleep apnea in males.

A rational approach to shift work in emergency medicine

As the only medical specialists who routinely provide continuous 24-hour daily coverage, emergency physicians are all too familiar with the demands of shift work. Although shift work has a pervasive effect on the practice of emergency medicine and is regarded as a major stressor, it has received little attention per se in our literature and in our residency training programs. We review the principles of circadian rhythms and their effects on sleep and alertness, and recommend ways by which emergency physicians can better schedule themselves to mitigate the negative consequences of working shifts.

A comparison of reported sleep disorders in patients on chronic hemodialysis and continuous peritoneal dialysis

There are few data about the prevalence and characteristics of reported sleep disorders in chronic dialysis patients and, although insomnia is often used as a marker of uremia, there are few data relating complaints of sleep to adequacy of dialysis. We therefore surveyed 48 hemodialysis (HD) patients, 22 continuous peritoneal dialysis (PD) patients, and 41 healthy control subjects about disordered sleep. The questionnaire included demographic data, questions characterizing the reported sleep problems, and linear analogue scales quantitating the severity of the sleep disturbance and feelings of anxiety, worry, and sadness. Kt/V determinations were also made for each dialysis patient. Fifty-two percent of the HD, 50% of the PD, and 12% of the control subjects reported problems sleeping (P less than 0.001, all dialysis patients v controls). No differences between HD and PD in characteristics of sleep problems were seen. Sleep severity scale results confirmed sleep disorders (7.2 in those with v 0.95 in those without sleep disorders, where 0 = sleep a little problem and 10 = a big problem, P less than 0.001). Caffeine intake (P less than 0.05) and worry (P less than 0.004) were the only factors associated with reported sleep disturbances. Kt/V values (1.4 +/- 0.3) did not predict reported sleep problems. Mean reported hours of sleep per night (5.5 +/- 2 v 5.8 +/- 1.4) and desired hours of sleep per night (8.3 +/- 2 v 7.6 +/- 1.3) were similar among dialysis patients and controls reporting sleep problems. Dialysis patients and controls without self-reported sleep disorders slept a mean of 7.1 +/- 2.4 and 7 +/- 1.1 h/night, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Negative polysomnogram in patients with obstructive sleep apnea syndrome

We evaluated the possibility that in some patients with obstructive sleep apnea, the initial polysomnogram may be negative. We reviewed polysomnograms performed at the Medical College of Georgia from 1984 to 1990 and found nine patients whose initial polysomnogram was negative but whose repeat polysomnogram confirmed obstructive sleep apnea. All nine patients (five women and four men; average age, 44.2 years) had an apnea index of less than 5 (fewer than five apneic episodes per hour) and had a total of fewer than 20 apneic episodes during the initial overnight polysomnogram. The change in average weight was not significant. Three patients had received short-term oxygen therapy, and two of these three received nasal continuous positive airway pressure prior to the initial study. The time that patients spent supine increased from 101 min in the initial study to 180 min in the second, but this was not significant (p = 0.12). Comparison of the initial and diagnostic polysomnograms showed significantly reduced total sleep time (from 3.75 +/- 1.84 h to 5.32 +/- 1.11 h; p = 0.04) and reduced rapid eye movement (REM) sleep time (from 0.27 +/- 0.27 h to 0.75 +/- 0.58 h; p = 0.037) in the initial study. We conclude that in a small subset of patients with obstructive sleep apnea, the initial polysomnogram may be falsely negative, which could be due to previous therapy, a reduction in total sleep time and REM sleep, or other unidentified factors.

Sleep apnea and essential hypertension: a critical review of the epidemiological evidence for co-morbidity

This paper reviews the epidemiological literature on the linkage between sleep apnea and essential hypertension. Despite the large number of case reports, general overviews and the wide acceptance of this linkage, surprisingly, only four epidemiological articles were identified. The prevalence of sleep apnea among hypertensives ranged between 26% and 47.8% (mean = 33.6%) across the studies as compared to the estimated prevalence of 0.4% to 1.4% in the general population. There seem to be no consistently replicated risk factors for apnea amongst hypertensives, although older age, relative obesity, and severity of hypertension have been suggested as possible markers for this co-morbidity. The findings require further replication with special efforts at studying: (1) unmedicated hypertensive patients; (2) patients without significant cardiac or renal complications; and (3) patients across a broad range of age, obesity, and severity of hypertension.

Narcolepsy: a review of a common, life-long sleep disorder

Narcolepsy is a severe debilitating chronic life-long sleep disorder that can be ameliorated but not cured. In the United States, its prevalence is at least 1 in 1000 making it more common than multiple sclerosis or Parkinson's disease. Its symptoms lead to severe lifestyle consequences, with profound impact on the affected persons, their interpersonal relationships, job, school experiences, and family life. Despite this, little has appeared in the nursing literature about the disorder. The most characteristic symptoms include uncontrollable excess daytime sleepiness, cataplexy (bilateral voluntary muscle weakness), sleep paralysis, hypnagogic hallucinations and disturbed night-time sleep. Characteristics of normal sleep are reviewed and compared with disturbances seen in narcolepsy. The aetiology, assessment, diagnosis, pharmacologic therapy, non-pharmacologic therapy and psychosocial issues are discussed along with needed research directions.