INTRODUCTION: Detrended fluctuation analysis (DFA) is used as a way of studying nonlinearity of EEG. In this study, DFA is applied on sleep EEG of normal subjects to look into its nonlinearity in terms of EEG channels and sleep stages. METHOD: Twelve healthy young subjects (age: 23.8+/-2.5 years old, male:female=7:5) have undergone nocturnal polysomnography (nPSG). EEG from nPSG was classified in terms of its channels and sleep stages and was analyzed by DFA. Scaling exponents (SEs) yielded by DFA were compared using linear mixed model analysis. RESULTS: Scaling exponents (SEs) of sleep EEG were distributed around 1 showing long term temporal correlation and self-similarity. SE of C3 channel was bigger than that of O1 channel. As sleep stage progressed from stage 1 to slow wave sleep, SE increased accordingly. SE of stage REM sleep did not show significant difference when compared with that of stage 1 sleep. CONCLUSION: SEs of Normal sleep EEG showed nonlinear characteristic with scale-free fluctuation, long-range temporal correlation, self-similarity and self-organized criticality. SE from DFA differentiated sleep stages and EEG channels. It can be a useful tool in the research with sleep EEG.
Electroencephalography* ; Polysomnography ; Sleep Stages ; Sleep, REM

OBJECTIVES: The dream recall and sleep of patients with rapid eye movement sleep behavior disorder (RBD) were not sufficiently studied. We hypothesized that RBD patients have frequent dream recall with poor sleep quality, and investigated the relationship between the dream recall frequency and sleep quality in RBD patients compared to controls. METHODS: We analyzed 81 drug naïve patients [RBD (+), 64.6±8.3 y, 57 males] and 81 age and gender matched patients with sleep disturbances without RBD [RBD (−), 63.7±7.3 y, 57 males]. All completed Pittsburgh sleep quality index (PSQI), insomnia severity index (ISI), Epworth sleepiness scale and Beck depression inventory. The 5-point rating scale was used to categorize dream recall frequency of most recent month (0=never, 4=very frequent). RESULTS: In RBD (+), dream recall frequency was much higher [frequent dreaming, 77.2% vs. 35.4%], and subjective sleep quality was much better [PSQI, 6.36±3.26 vs. 8.71±4.69]. Insomnia severity was much less in RBD (+) (ISI, 9.13±5.86) than RBD (−) (12.43±7.62). No significant differences were found in sleep parameters except lower N2 sleep % in RBD (+). The relationship between dream recall frequency and sleep was not significant in RBD (+), yet, a positive correlation was noted in RBD (−). CONCLUSIONS: RBD (+) had better sleep quality despite higher frequency of dream recall compared to RBD (−). Also dream recall was not related to their sleep quality in RBD (+), which suggests that RBD patients may have different sleep perception about their sleep and sleep quality.
Depression ; Dreams ; Humans ; REM Sleep Behavior Disorder ; Sleep Initiation and Maintenance Disorders ; Sleep, REM

OBJECTIVE: To realize the characteristics of clinical symptoms and PSG in elderly patients with obstructive sleep apnea hypopnea syndrome (OSAHS). METHOD: The clinical presentations, epworth sleepiness scale (ESS) and polysomnography findings were compared between elderly patients with OSAHS and middle age patients with OSAHS. RESULT: There were no significantly differences in clinical presentations including snoring, apnea and daytime sleepiness complaint between the elderly and middle aged patients with OSAHS, but the incidences of complications such as hypertension and other cardiovascular diseases was significantly higher in elderly patients than those in the middle aged patients (P<0.01). The sleep architecture disturbance was significantly worse in elderly OSAHS patients compared with the middle age patients. The percentages of non-rapid eye movement (NREM) stage I sleep were significantly increased, the rapid eye movement (REM) sleep were significantly decreased in elderly OSAHS patients than those in middle aged group (P<0.01 or P<0.05), but the percentages of awake, NREM stage II sleep and NREM stage II-IV sleep had no significantly difference in the two groups. The apnea hypopnea index (AHI), apnea index (AI), hypopnea index (HI), snoring index, ESS and body mass index (BMI) were significantly decreased, the lowest oxygen saturation (LSO2) and micro-arousal index were significantly increased in elderly OSAHS patients than those in middle aged group (P<0.01 or P<0.05). CONCLUSION The elderly OSAHS patients are less sever than the middle age, but the elderly patients have worse sleep architecture disturbance and more complications such as hypertension and other cardiovascular diseases.
Aged ; Humans ; Middle Aged ; Polysomnography ; Sleep ; Sleep Apnea, Obstructive ; diagnosis ; physiopathology ; Sleep Stages ; Sleep, REM

The reciprocal interaction between sleep and pain has been reported by numerous studies. Patients with acute or chronic pain often complain of difficulty falling asleep, frequent awakenings, shorter sleep duration, unrefreshing sleep, and poor sleep quality in general. According to the majority of the experimental human studies, sleep deprivation may produce hyperalgesic changes. The selective disruption of slow wave sleep has shown this effect more consistently, while results after selective REM sleep deprivation remain unclear. Patients with chronic pain have a marked alteration of sleep structure and continuity, such as frequent sleep-stage shifts, increased nocturnal awakenings, decreased slow wave sleep (SWS), decreased rapid eye movement (REM) sleep, and alpha-delta sleep. Many analgesic medications can alter sleep architecture in a manner similar to the effects of acute and chronic pain, suppressing SWS and REM sleep.
Chronic Pain ; Humans ; Sleep Deprivation ; Sleep, REM

BACKGROUND AND PURPOSE: Discrepancies between objectively measured sleep and subjective sleep perception in patients with insomnia have been reported. However, few studies have investigated sleep-state misperception in patients with obstructive sleep apnea (OSA). We designed this study to 1) delineate the factors that could affect this discrepancy and 2) infer an underlying mechanism in patients with OSA. METHODS: We recruited patients who visited our sleep clinic for the evaluation of their snoring and/or observed OSA. Participants completed a structured questionnaire and underwent overnight polysomnography. On the following day, five sessions of the multiple sleep latency test (MSLT) were applied. We divided the patients into two groups: normal sleep perception and abnormal perception. The abnormal-perception group included patients whose perceived total sleep time was less than 80% of that measured in polysomnography. RESULTS: Fifty OSA patients were enrolled from a university hospital sleep clinic. Excessive daytime sleepiness, periodic limb movement index (PLMI), and the presence of dreaming were positively associated with poor sleep perception. REM sleep near the sleep termination exerted important effects. Respiratory disturbance parameters were not related to sleep perception. There was a prolongation in the sleep latency in the first session of the MSLT and we suspected that a delayed sleep phase occurred in poor-sleep perceivers. CONCLUSIONS: As an objectively good sleep does not match the subjective good-sleep perception in OSA, physicians should keep in mind that OSA patients who perceive that they have slept well does not mean that their OSA is less severe.
Dreams ; Extremities ; Humans ; Polysomnography* ; Sleep Apnea, Obstructive* ; Sleep Initiation and Maintenance Disorders ; Sleep, REM ; Snoring

Rapid eye movement sleep behavior disorder (RBD) is a sleep disorder characterized by loss of muscle atonia during REM sleep associated with dream enactment, which usually start at the age of older than 50. RBD in elders are known to be developing symptoms of neurodegenerative disorders in the course of disease. However, the pathophysiology and prognosis of "early-onset" idiopathic RBD is unclear. Several existing standard value about REM sleep without atonia (RSWA) of RBD patients was established with "late-onset" RBD for those diagnosed at age 50 and greater, RSWA metrics in "early-onset" RBD patients diagnosed prior to age 50 years have not been previously described. Therefore, we report here two patients who were diagnosed as "early-onset" idiopathic RBD, and performed quantitative RSWA scoring. We suggested that "early-onset" idiopathic RBD has different etiologies the various characteristics of RSWA than adults with RBD.
Adult ; Dreams ; Humans ; Neurodegenerative Diseases ; Polysomnography* ; Prognosis ; REM Sleep Behavior Disorder* ; Sleep, REM ; Young Adult*

OBJECTIVES: A few studies have compared REM sleep-dependent obstructive sleep apnea syndrome (REM-OSA) with sleep stage non-dependent apnea syndrome (SND-OSA). Despite that REM-OSA might be more common in women than men, no studies have examined the probable characteristics of women patients with obstructive sleep apnea syndrome (OSAS). This study aimed at finding out the characteristics of REM-OSA in women by comparing it with SND-OSA. METHODS: Fifty-three subjects diagnosed as OSAS (AHI>5; AHI: apnea-hypopnea index) with nocturnal polysomnography at the Center for Sleep and Chronobiology of the Seoul National University Hospital between October 2004 and February 2006 were studied. Of them, 44 subjects with OSAS severity of mild (5REM-OSA were AHI-R/AHI-NR>2 and AHI-NR<15 (AHI-R: AHI during REM sleep, AHI-NR: AHI during non-REM sleep). We compared REM-OSA group with SND-OSA as well as the criteria-determined REM-OSA cases with the visually-determined ones. RESULTS: Among 44 subjects, 28 persons (63.6%) turned out to have REM-OSA by our criteria and 24 persons (54.5%) by visual determination. Statistically significant differences (p<0.05) were found between REM-OSA and SND-OSA groups in AHI, hypopnea index, total sleep time, total wake time, sleep efficiency index, percents of stage 1, 2 and REM sleep, and REM latency. Percent of stage REM sleep (%REM) turned out to have influence on AHI ratio (AHI-R/AHI-NR) (B=0.537, p=0.002). REM-OSA was likely to be diagnosed in milder severity of OSAS (chi-square=13.117, p<0.001) and those with higher %REM (chi-square=11.325, p=0.001). There was no significant difference between the criteria-determined and the visually-determined cases of REM-OSA. CONCLUSION: We suggest that REM-OSA and SND-OSA patients be differentiated in terms of pathophysiology and treatment strategies. Visual determination of REM-OSA might be useful as the screening procedure of REM-OSA. Further studies on women with OSAS and REM-OSA need to be done.
Apnea ; Female ; Humans ; Male ; Mass Screening ; Polysomnography ; Sleep Apnea, Obstructive ; Sleep Stages ; Sleep, REM

Unlike the case of adult obstructive sleep apnea syndrome (OSAS), there was no consistent finding on the changes of sleep architecture in childhood OSAS. Further understanding of the sleep electroencephalogram (EEG) should be needed. Non-linear analysis of EEG is particularly useful in giving us a new perspective and in understanding the brain system. The objective of the current study is to compare the sleep architecture and the scaling exponent (alpha) from detrended fluctuation analysis (DFA) on sleep EEG between OSAS and normal children. Fifteen normal children (8 boys/7 girls, 6.0+/-2.2 years old) and twelve OSAS children (10 boys/2 girls, 6.4+/-3.4 years old) were studied with polysomnography (PSG). Sleep-related variables and OSAS severity indices were obtained. Scaling exponent of DFA were calculated from the EEG channels (C3/A2, C4/A1, O1/A2, and O2/A1), and compared between normal and OSAS children. No difference in sleep architecture was found between OSAS and normal controls except stage 1 sleep (%) and REM sleep latency (min). Stage 1 sleep (%) was significantly higher and REM latency was longer in OSAS group (9.3+/-4.3%, 181.5+/-59.9 min) than in controls (5.6+/-2.8%, 133.5+/-42.0 min). Scaling exponent (alpha) showed that sleep EEG of OSAS children also followed the 'longrange temporal correlation' characteristics. Value of alpha increased as sleep stages increased from stage 1 to stage 4. Value of alpha from C3/A2, C4/A1, O1/A2, O2/A1 were significantly lower in OSAS than in control (1.36+/-0.05 vs. 1.41+/-0.04, 1.37+/-0.04 vs. 1.41+/-0.04, 1.37+/-0.05 vs. 1.41+/-0.05, and 1.36+/-0.07 vs. 1.41+/-0.05, p<0.05). Higher stage 1 sleep (%) in OSAS children was consistent finding with OSAS adults. Lower 'alpha' in OSAS children suggests decrease of self-organized criticality or the decreased piling-up energy of brain system during sleep in OSAS children.
Adult ; Brain ; Child ; Electroencephalography ; Humans ; Polysomnography ; Sleep Apnea, Obstructive ; Sleep Stages ; Sleep, REM

OBJECTIVE: To study the clinical characteristics and relationship between sleep body posture, sleep phase and occurrence in patients with various degree of obstructive sleep apnea-hypopnea syndrome (OSAHS). METHOD: Polysomnography recordings of 100 adults with OSAHS were divided into 3 groups according to AHI: mild with apnea-hypopnea indices (5 < or = AHI < or = 15), moderate (15 < AHI < or = 30) and severe (30 < AHI). The polysomnography data and clinical characteristics were compared between each groups. REM sleep-related OSAHS was defined as REM AHI/NREM AHI > or = 2. Positional OSAHS was defined as supine AHI/non-supine AHI > or = 2. RESULT: 90.91% (20/22) patients with mild and 82.35% (14/17) patients with moderate OSAHS were position dependent, 40.91% (9/22) patients with mild and 23.53% (4/17) patients with moderate OSAHS were REM sleep-related OSAHS. The percentage of REM sleep-related OSAHS and position dependent OSAHS were significantly higher in mild and moderate groups compared with in severe group (P < 0.05, respectively). In both mild and moderate groups, the supine AHI was significantly correlated with AHI (r = 0.491, 0.771, P < 0.05, respectively). In severe groups, the non-supine AHI was significantly correlated with AHI and Lowest oxygen saturation (LSaO2) (r = -0.424, 0.527,P < 0.01, respectively), NREM AHI was significantly correlated with LSaO2 (r = 0.470, P < 0.01). CONCLUSION Body position play significant effects in mild and moderate but not severe OSAHS. Patients with severe OSAHS are less likely to spend time in the supine position and REM compared with patients with mild and moderate OSAHS.
Adult ; Female ; Humans ; Male ; Middle Aged ; Polysomnography ; Posture ; Sleep Apnea, Obstructive ; etiology ; Sleep Stages ; Sleep, REM

BACKGROUND AND OBJECTIVES: Sleep has five different periods manifested by changes in the EEG activity and certain behavioral correlates. It has been proposed that the upper airway mechanics would be influenced by sleep stage. Although several methods have been used to evaluate the regions over which the upper airway collapses during sleep, there were seldom reports about the changes of upper airway according to the sleep stage. The present study was conducted to determine the effect of sleep stage on the upper airway dynamics. MATERIALS AND METHOD: Using electron beam, we studied ten normal subjects who did not have any sleep-disordered breathing. Each patient being monitored with EEG was scanned while sleeping naturally. The images were acquired during light sleep, deep sleep and REM sleep during at least two full respiratory cycles. RESULTS: Upper airway collapse was increased with the progression of sleep, but the level of stenosis was relatively constant throughout the sleep. Sleep stage had differential effects on the upper airway size depending on the investigated site. CONCLUSION: Our data suggest that upper airway mechanics are influenced by each sleep stage. This would indicate that the study of either point of sleep or either site of airway in isolation may not allow a proper insight on the overall upper airway pathophysiology.
Airway Obstruction ; Constriction, Pathologic ; Diagnostic Imaging ; Electroencephalography ; Humans ; Mechanics ; Sleep Apnea Syndromes ; Sleep Stages* ; Sleep, REM