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Concept: Sleep medicine

196

Characterizing respiratory rate variability (RRV) in humans during sleep is challenging, since it requires the analysis of respiratory signals over a period of several hours. These signals are easily distorted by movement and volitional inputs. We applied the method of spectral analysis to the nasal pressure transducer signal in 38 adults with no obstructive sleep apnea, defined by an apnea-hypopnea index <5, who underwent all-night polysomnography (PSG). Our aim was to detect and quantitate RRV during the various sleep stages, including wakefulness. The nasal pressure transducer signal was acquired at 100 Hz and consecutive frequency spectra were generated for the length of the PSG with the Fast Fourier Transform. For each spectrum, we computed the amplitude ratio of the first harmonic peak to the zero frequency peak (H1/DC), and defined as RRV as (100 - H1/DC) %. RRV was greater during wakefulness compared to any sleep stage, including rapid-eye-movement. Furthermore, RRV correlated with the depth of sleep, being lowest during N3. Patients spent most their sleep time supine, but we found no correlation between RRV and body position. There was a correlation between respiratory rate and sleep stage, being greater in wakefulness than in any sleep stage. We conclude that RRV varies according to sleep stage. Moreover, spectral analysis of nasal pressure signal appears to provide a valid measure of RRV during sleep. It remains to be seen if the method can differentiate normal from pathological sleep patterns.

Concepts: Pulmonology, Sleep, Sleep disorder, Discrete Fourier transform, Sleep apnea, Polysomnography, Obstructive sleep apnea, Sleep medicine

186

A 61-year-old man was referred to our hospital for evaluation of sleep apnea. He snored loudly and had apnea during sleep. During the day, he was sleepy, and when lying down, he could quickly fall asleep. He had a score of 15 on the Epworth Sleepiness Scale, which ranges from 0 to 24, with a score of more than 10 suggestive of excessive daytime somnolence. On physical examination, there were no abnormalities other than obesity (100 kg [220 lb]; body-mass index [the weight in kilograms divided by the square of the height in meters], 31). Overnight polygraphy revealed a score . . .

Concepts: Mass, Sleep, Sleep disorder, Sleep apnea, Sleep medicine, Epworth Sleepiness Scale, Somnolence, Kilogram

169

BACKGROUND: The recent SLEEMSA study that evaluated excessive daytime sleepiness (EDS) in Caucasian patients with multiple system atrophy (MSA) demonstrated that EDS was more frequent in patients (28%) than in healthy subjects (2%). However, the prevalence and determinants of EDS in other ethnic populations have not been reported to date. METHODS: We performed a single-hospital prospective study on patients with probable MSA. To ascertain the prevalence and determinants of EDS in Japanese MSA patients, we assessed the patients' degree of daytime sleepiness by using the Japanese version of the Epworth Sleepiness Scale (ESS). In addition, we investigated the effects of sleep-disordered breathing (SDB) and abnormal periodic leg movements in sleep (PLMS), which were measured by polysomnography, on the patients' ESS scores. RESULTS: A total of 25 patients with probable MSA (21 patients with cerebellar MSA and 4 patients with parkinsonian MSA) were included in this study. All patients underwent standard polysomnography. The mean ESS score was 6.2 +/- 0.9, and EDS was identified in 24% of the patients. SDB and abnormal PLMS were identified in 24 (96%) and 11 (44%) patients, respectively. The prevalences of EDS in patients with SDB and abnormal PLMS were 25% and 18%, respectively. No correlations were observed between ESS scores and the parameters of SDB or abnormal PLMS. CONCLUSIONS: The frequency of EDS in Japanese patients with MSA was similar to that in Caucasian MSA patients. SDB and abnormal PLMS were frequently observed in MSA patients, although the severities of these factors were not correlated with EDS. Further investigations using objective sleep tests need to be performed.

Concepts: Sleep, Sleep disorder, Parkinson's disease, Sleep apnea, Sleep medicine, Epworth Sleepiness Scale, Excessive daytime sleepiness, Sleep disorders

147

We often experience troubled sleep in a novel environment [1]. This is called the first-night effect (FNE) in human sleep research and has been regarded as a typical sleep disturbance [2-4]. Here, we show that the FNE is a manifestation of one hemisphere being more vigilant than the other as a night watch to monitor unfamiliar surroundings during sleep [5, 6]. Using advanced neuroimaging techniques [7, 8] as well as polysomnography, we found that the temporary sleep disturbance in the first sleep experimental session involves regional interhemispheric asymmetry of sleep depth [9]. The interhemispheric asymmetry of sleep depth associated with the FNE was found in the default-mode network (DMN) involved with spontaneous internal thoughts during wakeful rest [10, 11]. The degree of asymmetry was significantly correlated with the sleep-onset latency, which reflects the degree of difficulty of falling asleep and is a critical measure for the FNE. Furthermore, the hemisphere with reduced sleep depth showed enhanced evoked brain response to deviant external stimuli. Deviant external stimuli detected by the less-sleeping hemisphere caused more arousals and faster behavioral responses than those detected by the other hemisphere. None of these asymmetries were evident during subsequent sleep sessions. These lines of evidence are in accord with the hypothesis that troubled sleep in an unfamiliar environment is an act for survival over an unfamiliar and potentially dangerous environment by keeping one hemisphere partially more vigilant than the other hemisphere as a night watch, which wakes the sleeper up when unfamiliar external signals are detected.

Concepts: Neuroimaging, Sleep, Sleep deprivation, Sleep disorder, Sleep apnea, Polysomnography, Sleep medicine, Medial longitudinal fissure

63

Acute sleep deprivation can lead to judgement errors and thereby increases the risk of accidents, possibly due to an impaired working memory. However, whether the adverse effects of acute sleep loss on working memory are modulated by auditory distraction in women and men are not known. Additionally, it is unknown whether sleep loss alters the way in which men and women perceive their working memory performance. Thus, 24 young adults (12 women using oral contraceptives at the time of investigation) participated in two experimental conditions: nocturnal sleep (scheduled between 22:30 and 06:30 hours) versus one night of total sleep loss. Participants were administered a digital working memory test in which eight-digit sequences were learned and retrieved in the morning after each condition. Learning of digital sequences was accompanied by either silence or auditory distraction (equal distribution among trials). After sequence retrieval, each trial ended with a question regarding how certain participants were of the correctness of their response, as a self-estimate of working memory performance. We found that sleep loss impaired objective but not self-estimated working memory performance in women. In contrast, both measures remained unaffected by sleep loss in men. Auditory distraction impaired working memory performance, without modulation by sleep loss or sex. Being unaware of cognitive limitations when sleep-deprived, as seen in our study, could lead to undesirable consequences in, for example, an occupational context. Our findings suggest that sleep-deprived young women are at particular risk for overestimating their working memory performance.

Concepts: Psychology, Cognitive psychology, Sleep, Sleep deprivation, Cognition, Sleep medicine

59

Many studies have investigated factors that affect susceptibility to false memories. However, few have investigated the role of sleep deprivation in the formation of false memories, despite overwhelming evidence that sleep deprivation impairs cognitive function. We examined the relationship between self-reported sleep duration and false memories and the effect of 24 hr of total sleep deprivation on susceptibility to false memories. We found that under certain conditions, sleep deprivation can increase the risk of developing false memories. Specifically, sleep deprivation increased false memories in a misinformation task when participants were sleep deprived during event encoding, but did not have a significant effect when the deprivation occurred after event encoding. These experiments are the first to investigate the effect of sleep deprivation on susceptibility to false memories, which can have dire consequences.

Concepts: Psychology, Cognitive psychology, Sleep, Sleep deprivation, Cognition, Memory, Sleep medicine

40

To test the hypothesis that sleep disorder diagnosis would be associated with increased risk of preterm birth and to examine risk by gestational age, preterm birth type, and specific sleep disorder (insomnia, sleep apnea, movement disorder, and other).

Concepts: Childbirth, Sleep, Sleep deprivation, Sleep disorder, Sleep apnea, Sleep medicine

33

Zolpidem (Ambien, Sanofi) is the most widely used prescription drug for insomnia and one of the most commonly used drugs in the United States. Treatment of insomnia, which has important effects on patients' quality of life, may also have larger public health benefits. In its 2006 report, the Institute of Medicine (IOM) Committee on Sleep Medicine and Research concluded that sleep deprivation and sleep disorders represent an unaddressed public health problem that has substantial health consequences and leads to high health care costs.(1) The IOM noted that one of every five serious injuries from driving accidents can be attributed to . . .

Concepts: Health care, Pharmacology, Health economics, Sleep deprivation, Sleep disorder, Illness, Sleep medicine, Insomnia

28

ABSTRACT BACKGROUND: Systemic symptoms are common in sarcoidosis and are associated with a decreased quality of life. Excessive daytime sleepiness (EDS) is often associated with obstructive sleep apnea (OSA), but may be a systemic symptom independently associated with sarcoidosis. The aim of this study was to assess the relationship between sarcoidosis and EDS. METHODS: In a retrospective analysis, we compared sleepiness by the Epworth Sleepiness Scale score in 62 patients with sarcoidosis to 1,005 adults without sarcoidosis referred for polysomnography for suspicion of OSA. Linear regression models controlled for covariates. In a subgroup analysis of sarcoidosis patients, sleepiness scores and polysomnogram results were compared between those with normal and abnormal pulmonary function based on total lung capacity. RESULTS: EDS was more common in sarcoidosis than in controls, and sarcoidosis remained an independent predictor of increased sleepiness after controlling for covariates. Compared to controls referred for polysomnography, fewer sarcoidosis patients had clinically significant OSA. However, among sarcoidosis patients, OSA was more severe in those with abnormal lung function. CONCLUSIONS: Sarcoidosis is independently associated with EDS. Sleepiness may contribute to the morbidity of sarcoidosis, and should be followed even after treating for potentially co-existing OSA or depression. Abnormal lung function in sarcoidosis may contribute to OSA, although the mechanisms for this are not known.

Concepts: Lung, Sleep, Sleep disorder, Sleep apnea, Obstructive sleep apnea, Sleep medicine, Epworth Sleepiness Scale, Sleep disorders

28

Object The association of Chiari malformation Type I (CM-I) with syndromic craniosynostosis (SC) in children is well established. Central sleep apnea (CSA) may subsequently occur. However, sleep studies performed in these patients have been focused mainly on assessing the severity of obstructive sleep apnea. Therefore, the incidence and management of CSA in these patients remains poorly defined. Authors of this study aimed to assess the efficacy of foramen magnum decompression (FMD) in resolving CSA, initially detected incidentally, in a small cohort of patients with CM-I and SC. Methods The clinical data for 5 children who underwent FMD for CSA at Alder Hey Children’s Hospital between December 2007 and December 2009 were retrospectively analyzed. Outcomes were evaluated with respect to FMDs by utilizing pre- and postdecompression sleep studies. Of the 5 patients, 2 had Crouzon syndrome and 3 had Pfeiffer syndrome. Results Patient age at the time of surgery ranged from 1.1 to 12.6 years (median 4.1 years). The median postoperative follow-up was 3.6 years. Sleep studies revealed that 2 children experienced a > 80% reduction in CSAs at 1.5 and 21 months after decompression. The remaining 3 children experienced a > 60% reduction in CSAs when reevaluated between 2 and 10 months after decompression. The associated central apnea index improved for all patients. Conclusions Findings suggested that FMD is an effective treatment modality for improving CSA in patients with SC and associated CM-I. The use of multimodal polysomnography technology may improve the evaluation and management of these patients.

Concepts: Sleep, Sleep disorder, Sleep apnea, Polysomnography, Obstructive sleep apnea, Sleep medicine, Arnold-Chiari malformation, Alder Hey Children's Hospital