Transdermal Nicotine Patch Effects on EEG Power Spectra and Heart Rate Variability During Sleep of Healthy Male Adults

OBJECTIVE: The effect of transdermal nicotine patch on sleep physiology is not well established. The current study aimed to examine the influence of nicotine patch on homeostatic sleep propensity and autonomic nervous system. METHODS: We studied 16 non-smoking young healthy volunteers with nocturnal polysomnography in a double blind crossover design between sleep with and without nicotine patch. We compared the sleep variables, sleep EEG power spectra, and heart rate variability. RESULTS: The night with nicotine patch showed significant increase in sleep latency, wake after sleep onset, and stage 1 sleep; and decrease in total sleep time, sleep efficiency, and percentage of REM sleep. Also, spectral analysis of the sleep EEG in the night with nicotine patch revealed decreased slow wave activity in stage 2 and REM sleep and increased alpha activity in the first NREM-REM sleep cycle. Heart rate variability showed no differences between the 2 nights, but the low to high ratio (a parameter indicative of sympathetic nervous system activity) positively correlated with wake after sleep onset in night with nicotine patch. CONCLUSION: Transdermal nicotine patch significantly disrupts sleep continuity, sleep architecture, and homeostatic sleep propensity. The overactivation of the sympathetic nervous system may be responsible for these changes.

The Changes in Polysomnographic Sleep Variables by Periodic Limb Movements During Sleep / 수면정신생리

OBJECTIVES: Periodic limb movement disorder (PLMD) has been debated with regard to its clinical significance and diagnostic criteria. The current diagnostic criterion for PLMD in adults has been changed from periodic limb movement index (PLMI) > 5/ hour to PLMI > 15/hour by the International Classification of Sleep Disorders (ICSD). In this study, we aimed to investigate the changes in polysomnographic sleep variables according to PLMI and to determine the relevance of the diagnostic criterion for PLMD. METHODS: Out of 4195 subjects who underwent standard polysomnography, we selected 666 subjects (370 males and 296 females, aged 47.1 ± 14.8) who were older than 17 years and were not diagnosed with primary insomnia, sleep apnea, narcolepsy, or REM sleep behavior disorder. Subjects were divided into three groups according to PLMI severity: group 1 (PLMI ≤ 5), group 2 (5 15). Demographic and polysomnographic sleep variables and Epworth sleepiness scale (ESS) were compared among the three groups. RESULTS: There were significant differences among the three groups in age and gender. Sleep efficiency (SE) and stage 3 sleep percentage in group 1 were significantly higher than those in groups 2 and 3. The wake after sleep onset (WASO) score in group 1 was significantly lower than those in groups 2 and 3. However, there were no significant differences in SE, stage 3 sleep percentage, or WASO between groups 2 and 3. Sleep latency (SL) in group 1 was significantly lower than that in group 3, but there was no difference in SL between group 2 and group 3. ESS score in group 1 was significantly higher than that in group 3, but there was no difference between group 2 and group 3. Partial correlation analysis adjusted by age showed that PLMI was significantly related to SE and WASO. CONCLUSION: This study suggests that PLMI influences polysomnographic sleep variables. In addition, we found the individuals who did not have PLMD but had PLMI > 5 were not different in polysomnographic sleep variables from the individuals who had PLMD according to the current criterion. These results raise questions about the relevance of the current diagnostic criterion of PLMD.

Preliminary Study on Quantitative Sleep EEG Characteristics in Patients with Schizophrenia

We used quantitative electroencephalography (EEG) spectral analysis to compare activity in the bilateral frontal, central, and occipital areas in nine patients with schizophrenia and ten healthy control subjects during standard nocturnal polysomnography. Patients with schizophrenia had longer sleep latency than controls. In N2 sleep, the patients had significantly lower 0.5–1 Hz power and higher theta power in the left frontal region, and higher beta power in the left occipital region than did control subjects. In N3 sleep, the patients with schizophrenia had significantly higher alpha power in the left occipital region than did controls. These findings show distinctive EEG sleep patterns in patients with schizophrenia, which may reflect brain dysfunction or medication effects.

Differential Effects of Obesity on Obstructive Sleep Apnea Syndrome according to Age

OBJECTIVE: To evaluate the effect of obesity on obstructive sleep apnea syndrome (OSAS) by age in relation to anthropometric measurements. METHODS: The medical records of 1,110 participants diagnosed with OSAS were analyzed according to age. All participants underwent nocturnal polysomnography and had their body mass index, waist circumference, neck circumference (NC), and waist-to-hip ratio measured. RESULTS: According to the multiple linear regression analysis model for the natural logarithm of the apnea-hypopnea index treating all four anthropometric measurements and gender as covariates, the final stepwise model accounted for an increasing percentage of the variability in the severity of OSAS as a function of age: 7.0, 9.1, 14.5, and 25.6% for those aged <30, 30–39, 40–49, and 50–59 yrs, respectively. It accounted for a decreased percentage among those 60–69 (20.3%) and 70 yrs or older (3.9%). The correlation between NC and the severity of OSAS linearly increased as a function of age for those aged 30–59 yrs, peaked among those in their 60s, and dramatically decreased thereafter. CONCLUSION: Middle-aged patients with OSAS were more likely to be obese, as measured by anthropometric measurements, than were younger or older OSAS patients. In particular, the predictive value of NC was significantly lower for younger and older OSAS patients.

Periodic Limb Movements in Sleep is Associated with Increased Mortality

OBJECTIVE: To elucidate the association between periodic limb movements in sleep (PLMS) and mortality. METHODS: Nocturnal polysomnographic recordings of 1,344 subjects obtained from 1995 to 2008 were reviewed. The subjects were divided into four groups based on PLMS and insomnia: reference group (PLMS≤5), insomnia group (PLMS≤5 with insomnia symptoms), 515 group. We searched each subject's Identification Number in the death records from the Statistics of Korea, the national bureau of statistics, to determine deaths in the cohort that occurred prior to December, 2013. Cox-proportional hazard regression and Kaplan-Meier survival curve analyses were used to compare mortality among the four groups. RESULTS: Hazard ratios (HRs) in the 515 groups were significantly higher than that in the reference group before adjusting for age and gender [HR, 3.37; 95% confidence interval (CI), 1.73–6.55; p15 group had a higher mortality rate than that in the reference group after adjusting for age, gender, and sleep efficiency (HR, 1.99; 95% CI, 1.06–2.21; p=0.033). CONCLUSION: These results suggest that PLMS may be associated with increased mortality.

Comparative Effects of Mattress Type on Subjective and Objective Sleep Quality: A Preliminary Study / 수면정신생리

OBJECTIVES: We aimed to evaluate the effects of mattress type on both objective and subjective sleep quality in healthy good sleepers. METHODS: Fifteen healthy good sleepers with a mean age of 30.8 years participated in this study. A randomized crossover trial was carried out using two different mattress types: a standard mattress and a contour coil mattress. After a night of adaptation, all participants were randomized to either a standard mattress or a contour coil mattress. Then, nocturnal polysomnography was conducted for two consecutive nights. Subjective evaluations were obtained using a self-report questionnaire before and after the polysomnographic recording sessions. RESULTS: The polysomnographic showed no differences in total sleep time, sleep stage, or wake time after sleep onset between the two mattress conditions. Of the polysomnographic variables, only sleep onset latency was significantly reduced for the contour coil mattress. Additionally, participants reported better subjective sleep quality when sleeping on the contour coil mattress, according to the questionnaires. CONCLUSION: The type of mattress might affect not only subjective, but also objective sleep quality, including sleep onset latency.

Depressed REM Sleep Behavior Disorder Patients Are Less Likely to Recall Enacted Dreams than Non-Depressed Ones

OBJECTIVE: REM sleep behavior disorder (RBD) is associated with psychiatric symptoms, such as anxiety and alexithymia. However, only a few studies on the relationship between depression and RBD have been published. In this study, we investigated the occurrence of depression and associated factors in patients with RBD. METHODS: In total 94 patients (mean age: 61.9±12.7 years, male: 70.2%) diagnosed as RBD were examined using detailed clinical histories, the Beck Depression Inventory (BDI), the Epworth Sleepiness Scale (ESS), and nocturnal polysomnography (PSG). RESULTS: The mean BDI score of all patients was 12.4±10.3 and 44.7% of RBD patients showed depressed mood (BDI >11 points). Depressed RBD patients were less able to recall enacted dreams than were non-depressed patients (61.9% vs. 86.5%, p=0.008). Logistic regression analysis showed that failure to recall enacted dreams was significantly associated with depression, after controlling for confounding variables including the respiratory disturbance index and a history of psychiatric disorders (odds ratio=0.323, p=0.041). CONCLUSION: In this study, 44.7% of RBD patients were found to suffer from depressed mood. And, depression was found to be associated with reduced ability to recall enacted dreams. We suggest that routine evaluation of depression be performed in RBD patients, particularly when failure to recall enacted dreams is evident. We speculate that such failure may be associated with emotional dysregulation or neurodegeneration.

Sleep EEG Characteristics in Young and Elderly Patients with Obstructive Sleep Apnea Syndrome

OBJECTIVE: In the present study, it was hypothesized that the sleep electroencephalogram (EEG) characteristics of young (55 yrs) OSAS patients would differ. METHODS: We analyzed 76 sleep EEG recordings from OSAS patients (young group: n=40, mean age: 24.3±4.9 yrs; elderly group: n=36, mean age: 59.1±4.9 yrs), which were obtained during nocturnal polysomnography. The recordings were assessed via spectral analysis in the delta (0.5–4.5 Hz), theta (4.5–8 Hz), alpha (8–12 Hz), beta (12–32 Hz), slow sigma (11–13 Hz), and fast sigma (13–17 Hz) frequency bands. RESULTS: Apnea Hypopnea Index (AHI) and sleep efficiency (%) did not differ significantly between the two groups (19.8±14.4 vs. 25.9±16.0, p=0.085; 84.4±12.6 vs. 80.9±11.0, p=0.198, respectively). After adjusting for gender, the slow/fast sigma ratio was not significantly correlated with AHI in the elderly group (r=-0.047, p=0.790) but AHI was inversely correlated with the slow/fast sigma ratio in the young group (r=-0.423, p=0.007). A multiple linear regression analysis revealed that a higher AHI was related with a lower slow/fast sigma ratio in the young group (β=-0.392, p=0.028) but not the elderly. CONCLUSION: In the present study, sleep EEG activity differed between young and elderly OSAS patients. The slow/fast sigma ratio was associated with OSAS severity only in young patients, suggesting that young OSAS patients may have a distinctive brain plasticity compared with elderly patients.

Reliability and Validity of the Fatigue Severity Scale among University Student in South Korea

OBJECTIVES: There are only a limited number of studies on instruments assessing fatigue in university students, although fatigue exerts negative influences on their health and academic performances and fatigue-related complaints are more frequently reported in young adults than middle-aged adults. The aim of this study was to validate the 9-item Fatigue Severity Scale (FSS) among university students including both undergraduate and graduate students in South Korea. METHODS: A total of 176 university students completed a battery of self-report questionnaires, including the FSS, the Brief Fatigue Inventory (BFI), the Beck Depression Inventory-II (BDI-II), the Beck Anxiety Inventory (BAI), the Medical Outcomes Study Short Form 36 version 2 (MOS-SF36v2), and the Inclusion of Community in the Self Scale (ICS). The data were collected from February of 2012 to June of 2012. The reliability, convergent validity, divergent validity, and exploratory factor analyses were conducted to assess psychometric properties of the FSS. RESULTS: The mean FSS score was 3.20 (standard deviation = 1.43). The FSS demonstrated an excellent internal consistency (Cronbach's alpha = 0.93) and item-total correlations ranged from 0.56 to 0.90. Correlations of the FSS with the BFI (r = 0.71, p < 0.01), BDI-II (r = 0.54, p < 0.01), BAI (r = 0.46, p < 0.01), MOS-SF36v2 physical component summary (r = -0.28, p < 0.01), MOS-SF36v2 mental component summary (r = -0.55, p < 0.01), and ICS (Spearman's rho = -0.07, p = 0.33) showed acceptable convergent and divergent validity. Exploratory factor analysis defined one underlying factor (eigenvalue = 5.67) that explained 93.50% of the total variance. CONCLUSIONS: To the best of our knowledge, this is the first study to investigate reliability and validity of the FSS in university students. The FSS exhibits good psychometric properties for evaluation of fatigue among university students in South Korea. Since the FSS is easy to administer, score, and interpret, it could be a useful tool in research and practice for assessing fatigue among university students.

Sex Differences in Cerebellar Structure of Healthy Adults

OBJECTIVES: Although there have been studies that examine sex differences of the brain structures using magnetic resonance imaging, studies that specifically investigate cerebellar structural differences between men and women are scarce. The purpose of current study was to examine sex differences in structures of the cerebellum using cerebellar template and cerebellum analysis methods. METHODS: Sixteen men and twenty women were included in the study. A MATLAB based program (MathWorks, Natick, MA, USA), Statistical Parametric Mapping 5 (SPM5) using the spatially unbiased infra-tentorial atlas template (SUIT) as the cerebellum template, was used to analyze the brain imaging data. RESULTS: There was no significant difference in age between men (mean age = 28.1) and women (mean age = 27.2). Men showed higher gray matter density than women in two left cerebellar areas including the clusters in the lobules IV and V (a cluster located across the lobules IV and V), and the lobule VIIIb (lobules IV and V, t = 4.75, p < 0.001 ; lobule VIIIb, t = 3.08, p = 0.004). CONCLUSIONS: The current study found differences in cerebellar gray matter density between men and women. The current study holds its significance for applying the template specifically developed for the analysis of cerebellum.

Sleep and Pain / 수면정신생리

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.

Snoring Clinic Visitors' Knowledge of Obstructive Sleep Apnea Syndrome / 수면정신생리

OBJECTIVES: OSAS (obstructive sleep apnea syndrome) is a common disorder and its consequences are often serious. It is important to detect the disorder early in the course for proper treatment. This study is to grasp the snoring clinic visitors' knowledge level of OSAS. METHODS: One hundred and seventy-nine visitors at the of snoring clinic of Seoul National University Hospital were surveyed by questionnaire about reasons of visit and knowledge of treatment methods of snoring and OSAS, diagnostic method, OSAS-related symptoms, and complications. RESULTS: Most of the respondents (89.4%) "have already heard about OSAS" and the major sources of information was the mass media (58.1%) such as television and radio. More than half (60.3%) were aware that snoring is closely related to OSAS. More than half (59.8%) recognized that a nocturnal polysomnograpy was necessary for proper diagnosis. Two thirds (67%) of the respondents noted surgery as a treatment for snoring. More than half (55.9%) answered that they would follow the doctor's advice on the treatment choice. Only 12.3% of respondents "have heard about nCPAP". No one chose nCPAP (nasal continuous positive airway pressure) as a treatment for either snoring or OSAS. About one third (34.6%) of the respondents were aware that OSAS is related to hypertension. Only 12.8% noted that OSAS is related to diabetes mellitus. CONCLUSION: Visitors at the snoring clinic were found to have substantially limited knowledge of health risks and proper treatments of OSAS. We suggest that it is crucially important to educate patients and offer easy-to-understand information on snoring and OSAS. We predict that provision of educaiton and information to patients and general public will faciliate the diagnosis and treatment of snoring and OSAS and reduce the related disorders such as hypertension, stroke, and diabetes mellitus.

Characteristics of Obstructive Sleep Apnea Syndrome Patients Proven with Nocturnal Polysomnography as Correlates of Age and Gender / 수면정신생리

OBJECTIVES: The purpose of this study was to assess the clinical and polysomnographic characteristics of Korean patients with obstructive sleep apnea syndrome (OSAS), especially in relation to differences due to age and gender. METHODS: All subjects were consecutive patients who were proven to have OSAS with nocturnal polysomnography. They were interviewed with a structured interview format including sociodemographic information, past medical history, medication, and sleep-related history. Simultaneously, they were also given Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) to answer in order to check subjective sleep quality and subjective sleepiness. RESULTS: Mean age of the 308 subjects was 49.5+/-13.3 years, with 77.6% of the subjects being males and 22.4% of the subjects being females. The aging effects on the sleep architecture in Korean OSAS corresponded with normal aging, but with the effect of OSAS itself superimposed, the extent of aging effects was more marked than that of normal aging. The severity of Korean patients of OSAS was not correlated with age. When divided into age subgroups, significant correlation was found between RDI and BMI in patients of each subgroup of those in the 4th to 7th decades. The oldest subgroup (>70 years) described their subjective sleep quality as poorer than any other age subgroups, despite of less subjective drowsiness. The severity of OSAS and the change of sleep architecture of male subjects turned out to be severer than those of female ones. The female/male ratio of the subjects tended to increase with aging. CONCLUSIONS: The aging effect on the sleep architecture in Korean OSAS seems to be a mixture of the changes by normal aging and sleep disorder per se. The severity of OSAS was not correlated with age, but highly correlated with BMI. The severity of OSAS and the change of sleep architecture of male patients were severer than those of female ones.

Psychophysiological Characteristics of Chronic Pain Patients Measured by Biofeedback System / 수면정신생리

OBJECTIVES: Chronic pain is one of the most common experiences of humans and a typical psychophysiological disorder. The aim of this study was to measure the psychophysiological responses in chronic pain patients using a biofeedback system, and to compare them with the results from normal healthy subjects. METHODS: Forty two patients with chronic pain (17 males and 25 females, average age 44.67+/-11.10 years) and 42 normal healthy controls (17 males and 25 females, average age 45.17+/-10.46 years) participated in this study. Electromyography (EMG), skin conductance (SC), and skin temperature (ST) were recorded using biofeedback system during the 3 phases (baseline, stress, and recovery) of stress reactivity test, and average values of them were calculated. Difference of values between two groups in each corresponding phase was analyzed with independent t-test, and change of values across phases of stress reactivity test was analyzed with paired t-test (all two-tailed, p<0.05). RESULTS: Compared to normal controls, chronic pain patients had higher value of EMG (baseline : 8.10+/-5.97 micronV vs 4.72+/-1.52 micronV, t=-3.56, p<0.01 ; stress : 11.25+/-6.89 micronV vs 8.49+/-4.78 micronV, t=-2.13, p<0.05 ; recovery : 7.12+/-3.77 micronV vs 4.78+/-1.59 micronV, t= -3.70, p<0.01) and SC (baseline : 1.06+/-1.0 micronS vs 0.42+/-0.29 micronS, t=-4.0. p<0.01 ; stress : 1.87+/-2.05 micronS vs 1.03+/-0.86 micronS, t=-2.47, p<0.05 ; recovery : 1.74+/-1.77 micronS vs 0.64+/-0.59 micronS, t=-3.8, p<0.01) in all the 3 phases. But, skin temperature comparison did not reveal significant differences in all the 3 phases between two groups. CONCLUSION: Psychophysiological responses of chronic pain patients in stress reactivity test were different from those of normal healthy controls. These results suggest that sympathetic nervous system is more activated in chronic pain patients.

Sleep Fragementation Decreases during the nCPAP Titration Night in Obstructive Sleep Apnea Syndrome / 수면정신생리

OBJECTIVES: Obstructive sleep apnea syndrome (OSAS) not only causes respiratory disturbances during sleep but also decreases the quality of nocturnal sleep through sleep fragmentation and sleep structure change. We aimed at comparing the changes in sleep fragmentation and structure between baseline (diagnostic) nocturnal polysomnography (NPSG) and nCPAP (nasal continuous positive airway pressure) titration trial. METHODS: One hundred and three patients with a baseline night of respiratory disturbance index (RDI) of 5 or greater and reduced RDI score during nCPAP titration night were retrospectively selected for the study. Sleep fragementation and sleep structure between baseline NPSG and the NPSG during nCPAP titration were compared. Sleep fragmentation index (SFI) was defined as the total number of awakenings and shifts to stage 1 sleep divided by the total sleep time in hour. SFI and other polysomnographic parameters were statistically compared between the two nights. RESULTS: SFI during baseline NPSG and nCPAP titration nights were 29.0+/-13.8 and 15.2+/-8.8, respectively, indicating a significant SFI decrease during nCPAP titration (t=9.7, p<0.01). SFI showed significant negative correlations with sleep efficiency (r=-0.60, p<0.01) and total sleep time (r=-0.45, p<0.01) and a positive correlation with RDI (r=0.28, p<0.01). CONCLUSION: Use of nCPAP, even during the titration, significantly decreases sleep fragmentation and improves sleep structure in OSAS patients. We suggest that SFI may be utilized as a measure of assessing OSAS severity and nCPAP efficacy.

Sleep Patterns and Academic Performance in Medical Students / 수면정신생리

INTRODUCTION: Although it is well known that medical students are not getting an adequate amount of sleep, there have been only few studies on the sleep patterns of medical students in Korea. Therefore, the present study aimed to investigate the life style and sleep patterns of Korean medical students and the impact they have on the students' academic performance. METHODS: A questionnaire package was administered to the 3rd year medical students at the Seoul National University to examine their sleep patterns on weekdays and weekends. It consisted of questions asking about their lifestyles as well as Pittsburgh sleep quality index (PSQI) and GPA (Grade Point Average) that are considered relevant to their sleep patterns. A total of 110 students (85 males and 25 females, mean age 24.4+/-20.6) responded to the survey and the result was analyzed using the independent t-test, the chi-square test, the paired t-test, Pearson's rank correlation and ANOVA. P-values of less than 0.05 were considered statistically significant in all analyses. RESULTS: The weekend bedtime was significantly delayed (01:24 on weekday; 03:12 on weekend; t=-5.23, p<0.01), the weekend rise time was delayed (07:36 on weekday; 10:30 on weekend; t=-24.48, p<0.01) and the total sleep time was increased on weekends (5:57 on weekday; 8:17 on weekend; t=15.94, p<0.01). They wished to sleep for 7 hours 6 minutes which was different from their actual weekday total sleep time (t=-11.41, p<0.01). The poor sleeper group had lower GPAs than the good sleeper group (t=2.05, p<0.05). The GPA of medical students were negatively correlated with age (r=-0.23, p<0.05), daily amount of smoking (r=-0.78, p<0.01), total amount of smoking (r=-0.75, p<0.01), weekday sleep latency (r=-0.23, p<0.05), weekend sleep latency (r=-0.23, p<0.05) and PSQI score (r=-0.30, p<0.01). CONCLUSION: Medical students were experiencing a lack of sleep during weekdays as they have a later bedtime and earlier rise time, and consequently had more hours of sleep on weekends. Overall, the responded students were experiencing poor sleep quality, and the GPAs of the poor sleeper group were lower than those of the good sleeper group.

Comparison of REM Sleep-Dependent Obstructive Sleep Apnea Syndrome with Sleep Stage Non-Dependent One in Women Patients / 수면정신생리

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 (52 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.

Spectral Analysis of REM Sleep EEG in Narcolepsy and REM Sleep Behavior Disorder / 수면정신생리

INTRODUCTION: It has been proposed that narcolepsy and REM sleep behavior disorder (RBD) have overlapped symptom profile and pathophysiology. This study was aimed at measuring and comparing changes in EEG frequency band of REM sleep in narcolepsy and RBD, applying EEG spectral analysis method. METHODS: Nine patients diagnosed as narcolepsy and the same number of RBD patients were studied. Spectral analysis of the REM sleep EEG was performed in each patient on 9 epochs selected evenly from the first, second, and third REM periods. Then, we compared frequency band percentages of REM sleep EEG in narcolepsy and RBD. RESULTS: Narcolepsy patients had significantly higher delta frequency ratio than RBD ones (p=0.00). In alpha and beta2 frequency bands, RBD patients showed higher percentage than narcolepsy ones. Slow wave sleep was more prevalent in narcolepsy patients. But, no difference of REM sleep percentage was found between the two groups (p=0.93). CONCLUSION: Higher delta frequency ratio in REM sleep of narcolepsy patients than RBD ones reflects that sleep-promoting mechanism is more dominant in narcolepsy than in RBD.

Detrended Fluctuation Analysis on Sleep EEG of Healthy Subjects / 수면정신생리

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.

Role of Actigraphy in the Estimation of Sleep Quality in Obstructive Sleep Apnea Syndrome / 수면정신생리

BACKGROUND: Actigraphy is a reliable and valid method for assessing sleep in normal, healthy populations, but it may be less reliable and valid for detecting disturbed sleep in patients. In this study, we attempted to assess the utility of actigraphy in the estimation of sleep quality in patients with obstructive sleep apnea syndrome (OSAS), a major sleep disorder. METHOD: We analyzed the data of patients who underwent polysomnography (PSG) and actigraphy simultaneously for one night at the Center for Sleep and Chronobiology, Seoul National University Hospital from November 2004 to March 2006. Eighty-nine subjects with OSAS alone and 21 subjects with OSAS and periodic limb movement disorder (PLMD) were included for final data analyses between groups. Polysomnographic and actigraphic data were also compared. RESULTS: In subjects with mild OSAS (RDI<15), modretae (15< or = RDI<30), and OSAS with PLMD, PSG and actigraphy did not show significant difference in total sleep time and sleep efficiency. However in severe (30< or =RDI) OSAS subjects, PSG and actigraphy showed significant difference in total sleep time and sleep efficiency. In all patients, no correlations were found between sleep parameters from PSG and from those using actigraphy. CONCLUSIONS: We suggest that in severe OSAS patients, PSG is the diagnostic tool. In mild and moderate cases, actigraphy might be used as a screening tool.