• Sleep Medicine and Psychophysiology
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• v.23 no.1
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• pp.10-15
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• 2016

Since its development in the early 70s, actigraphy has been widely used in sleep research and clinical sleep medicine as an assessment tool of sleep and sleep-wake cycles. The validation and reliability of actigraphic measures have been reasonably examined in healthy normal individuals with good sleep patterns. Recent literature suggests that the use of actigraphy could be further extended to monitor insomnia and circadian sleep-wake disturbances, and detect sleep changes associated with drug treatments and non-pharmacologic interventions, although it is generally recommended to use complementary assessments such as sleep diaries and overnight polysomnography when possible. The development of actigraphy includes its improved hardware sensors for better detection of movements and advanced algorithms to score sleep and wake epochs. In this paper, we briefly review the quantitative analysis methods of actigraphy and its potential applications in sleep research.

• Sleep Medicine and Psychophysiology
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• v.19 no.2
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• pp.59-62
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• 2012

Borderline personality disorder (BPD) is characterized by identity and interpersonal problem, affective dysregulation and pervasive severe impulsivity. Although sleep disturbances are not primary symptoms of BPD, they are important aspects of this disorder. However, clinicians and researchers did not give much attention to the sleep symptoms of BPD yet. Measured by nocturnal polysomnography, increased sleep latency as well as reduced total sleep time and sleep efficiency, and 'depression-like' REM abnormalities (i.e., reduced REM latency and increased REM density) are found in BPD patients. Co-morbid sleep disorders such as chronic insomnia, nightmare disorder or circadian rhythm sleep disorder associated with BPD have been reported. Clinicians should focus on the sleep complaints of BPD patients, and carefully manage such symptoms with sleep hygiene education, cognitive psychotherapy or light therapy.

• Tuberculosis and Respiratory Diseases
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• v.45 no.1
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• pp.153-168
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• 1998

Background: The existing data indicate that obstructive sleep apnea syndrome contributes to the development of cardiovascular dysfunction such as systemic hypertension and cardiac arrhythmias, and the cardiovascular dysfunction has a major effect on high long-term mortality rate in obstructive sleep apnea syndrome patients. To a large extent the various studies have helped to clarify the pathophysiology of obstructive sleep apnea, but many basic questions still remain unanswered. Methods: In this study, the influence of obstructive sleep apnea on systemic blood pressure, cardiac rhythm and urinary catecholamines concentration was evaluated. Over-night polysomnography, 24-hour ambulatory blood pressure and ECG monitoring, and measurement of urinary catecholamines, norepinephrine (UNE) and epinephrine (UEP), during waking and sleep were undertaken in obstructive sleep apnea syndrome patients group (OSAS, n=29) and control group (Control, n=25). Results: 1) In OSAS and Control, UNE and UEP concentrations during sleep were significantly lower than during waking (P<0.01). In UNE concentrations during sleep, OSAS showed higher levels compare to Control (P<0.05). 2) In OSAS, there was a increasing tendency of the number of non-dipper of nocturnal blood pressure compare to Control (P=0.089). 3) In both group (n=54), mean systolic blood pressure during waking and sleep showed significant correlation with polysomnographic data including apnea index (AI), apnea-hypopnea index (AHI), arterial oxygen saturation nadir ($SaO_2$ nadir) and degree of oxygen desaturation (DOD). And UNE concentrations during sleep were correlated with AI, AHI, $SaO_2$ nadir, DOD and mean diastolic blood pressure during sleep. 4) In OSAS with AI>20 (n==14), there was a significant difference of heart rates before, during and after apneic events (P<0.01), and these changes of heart rates were correlated with the duration of apnea (P<0.01). The difference of heart rates between apneic and postapneic period (${\Delta}HR$) was significantly correlated with the difference of arterial oxygen saturation between before and after apneic event (${\Delta}SaO_2$) (r=0.223, P<0.001). 5) There was no significant difference in the incidence of cardiac arrhythmias between OSAS and Control In Control, the incidence of ventricular ectopy during sleep was significantly lower than during waking. But in OSAS, there was no difference between during waking and sleep. Conclusion : These results suggested that recurrent hypoxia and arousals from sleep in patients with obstructive sleep apnea syndrome may increase sympathetic nervous system activity, and recurrent hypoxia and increased sympathetic nervous system activity could contribute to the development of cardiovascular dysfunction including the changes of systemic blood pressure and cardiac function.

• Sleep Medicine and Psychophysiology
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• v.3 no.2
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• pp.18-31
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• 1996

Jet-lag can be defined as the cumulative physiological and psychological effects of rapid air travel across multiple time zones. Many reports have suggested that age-related changes in sleep reflect fundamental changes in the circadian system and in significant declines in slow wave sleep. Jet lag is a dramatic situation in which the changes of the phase of circadian process and homeostatic process of sleep occur. Thus the authors evaluatead the changes of sleep-wake cycle from jet lag by age. Thirty-eight healthy travellers were studied for 3 days before and 7 days after jet-flights across seven to ten time zone. They were aged 19-70, They trareled eastbound, Seoul to North America (USA, Canada). Sleep onset time, wake-up time, sleep latency, awakening frequency on night sleep, awakening duration on night sleep, sleepiness at wake-up and nap length were evaluated. Our results suggest that by the 7 to 10 time zone shift, the old age group was significantly influenced in sleep-wake cycles. The date on which subjective physical condition was recovered was $6.23{\pm}83$ day after arrivals for old age group, while for young and middle age group, $4.46{\pm}1.50$ day and $4.83{\pm}1.52$ day, respectively. In old age group, sleep onset time was later than baselines and could not recover untill 7th day. But in other groups, the recovery was within 5th day. Nap dura fion was longer in old age group through jet lag than younger age group. In other parameters, there was no definite difference among three age groups. Our results suggested that the old age was significantly influenced by the disharmony between internal body clock and sleep-wake cycle needed at the travel site. Thus we proved that recovery ability from jet lag was age-dependent as well as travelling direction-dependent. To demonstrate more definite evidence, EEG monitoring and staging of sleep were funthun encouraged.

• Sleep Medicine and Psychophysiology
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• v.2 no.2
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• pp.146-155
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• 1995

Jet lag can be defined as the cumulative physiological and psychological effects of rapid air travel across multiple time zone. The consequences of jet lag include fatigue, general malaise, sleep disturbances, and reductions of cognitive and psychomotor performance, all of which have been documented in experimental biological and air crew personnel studies. Thus authors tried to study the jet lag of natural travellers by modified self reporting sleep log. Total 61 healthy travellers was studied for 3 days before and 7 days after jet-flights across seven to ten time zone. The eastbound travelling group was 38 persons, aged 19 -70 and westbound travelling group was 23 persons, aged 13 - 69. Sleep onset time, wake-up time, sleep latency, awakening frequency on night sleep, awakening duration on night sleep, sleepiness at wake-up and nap length were evaluated. Our results suggested that the 7 to 10 time zone shift gave significant influence to traveller's sleep-wake cycles. The date which subjective physical condition was recovered on was $5.16{\pm}1.50$ day after arrivals for eastbound, while for westbound, $4.91{\pm}1.62$ day. In eastbound travelling, sleep onset time became later than baselines and could not recover until 7th day. But in westbound, it became earlier than baseline and could recover until 6th day. The mean score of 24-hour sleepiness was greater in eastboumd than westbound. Therefore the eastbound travelling caused more sleep-wake cycle disturbance and daytime dysfunction than westbound travelling. In other parameters, there was no definite difference between east and westbound. From our results, it was suggested that the symptom severity of jet lag was dependent on the travelling direction. To demonstrate more definite evidence, large sized data collections and comparision by age difference were needed.

• Journal of Internet Computing and Services
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• v.17 no.1
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• pp.35-45
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• 2016

Melatonin hormone involved in human's circadian rhythm adjustment sensitively responds to light's specific short wavelength ratio. A shift worker's circadian rhythm disturbance and sleep disorder are caused by the existing lighting conditions, whose short wavelength ratio is fixed. The life pattern of a shift worker changes irregularly because of irregular working hours and the same lighting environment; thus, his/her concentration is reduced. For such a reason, negative effects ensue to the detriment of healthy everyday life, including a high risk of accidents or having unsound sleep after leaving work. A smartphone-based wavelength control LED lighting system that targets shift workers and that can easily measure and control lighting suitable for wake-sleep cycle, according to working hours and closing hours, is proposed in this paper. First, after the light characteristics of LED lighting that changes depending on light control ratio are measured through the color sensor installed on the smartphone and the externally-linked Mini-Spectrometer, they are stored in the database. Based on the stored optical characteristics data, the measurement module and light control module are implemented. Lighting is offered using a control ratio having the maximum rate of short wavelength in consideration of the target illuminance, classified according to work type by identifying working hours as time when waking is required for shift workers. After a shift work leaves work, the amount of lighting is varied, using a control ratio having a minimum short wavelength rate so that a shift worker can enter the sleep state naturally.

• Sleep Medicine and Psychophysiology
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• v.28 no.2
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• pp.70-77
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• 2021

Objectives: Our study aims to investigate the clinical and polysomnographic variables associated with subjective sleep perception. Methods: Among the patients who underwent nocturnal polysomnography (PSG) at the Center for Sleep and Chronobiology of Seoul National University Hospital from May 2018 to July 2019, 109 diagnosed with insomnia disorder based on DSM-5 were recruited for the study, and their medical records were retrospectively analyzed. Self-report questionnaires about clinical characteristics including Pittsburgh sleep quality index (PSQI), Beck depression inventory (BDI), and Epworth sleepiness scale (ESS) were completed. Subjective sleep quality was measured using variables of subjective total sleep time (subjective TST), subjective sleep onset latency (subjective SOL), subjective number of awakenings, morning feeling after awakening, and sleep discrepancy (subjective TST-objective TST) the morning after PSG. Pearson and Spearman correlation analyses were used to determine the factors associated with subjective sleep perception. Results: In patients with insomnia, subjective TST was negatively correlated with Wake After Sleep Onset (WASO) (p = 0.001) and N1 sleep (p = 0.039) parameters on polysomnography. Also, it was negatively correlated with PSQI (p < 0.001) and BDI (p = 0.014) scores. Sleep discrepancy was negatively correlated with PSQI score (p = 0.018). Morning feeling was negatively correlated with PSQI (p = 0.019) and BDI (p < 0.001) scores. Conclusion: Our results demonstrated that subjective sleep perception is associated with PSG variables (WASO and N1 sleep) and with PSQI and BDI scores. In clinical practice, it is helpful to assess and manage insomnia patients in consideration of objective sleep variables, subjective sleep quality, and depressed mood, which can influence subjective sleep perception.

• Sleep Medicine and Psychophysiology
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• v.25 no.2
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• pp.82-91
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• 2018

Objectives: Synchronous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) has been used to explore sleep stage dependent functional brain networks. Despite a growing number of sleep studies using EEG-fMRI, few studies have conducted network analysis on whole night sleep due to difficulty in data acquisition, artifacts, and sleep management within the MRI scanner. Methods: In order to perform network analysis for whole night sleep, we proposed experimental procedures and data processing techniques for EEG-fMRI. We acquired 6-7 hours of EEG-fMRI data per participant and conducted signal processing to reduce artifacts in both EEG and fMRI. We then generated a functional brain atlas with 68 brain regions using independent component analysis of sleep fMRI data. Using this functional atlas, we constructed sleep level dependent functional brain networks. Results: When we evaluated functional connectivity distribution, sleep showed significantly reduced functional connectivity for the whole brain compared to that during wakefulness. REM sleep showed statistically different connectivity patterns compared to non-REM sleep in sleep-related subcortical brain circuits. Conclusion: This study suggests the feasibility of exploring functional brain networks using sleep EEG-fMRI for whole night sleep via appropriate experimental procedures and signal processing techniques for fMRI and EEG.

• Tuberculosis and Respiratory Diseases
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• v.60 no.1
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• pp.76-82
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• 2006

Background : The objective of this study was to understand sleep-related problems, and to determine whether the sleep questionnaires is a clinically useful method in patients who need polysomnography. Methods : Subjects were patients who performed polysomnography and who asked to answer a sleep questionnaires at the Sleep Disorders Clinic of St. Paul's Hospital, Catholic University of Korea. Baseline characteristics, past medical illness, behaviors during sleep-wake cycle, snoring, sleep-disordered breathing and symptoms of daytime sleepiness were analyzed to compare with data of polysomnography. Results : The study population included 1081 patients(849 men, 232 female), and their mean age was $44.2{\pm}12.8years$. Among these patients, 38.9% had an apnea-hypopnea index(AHI)<5, 27.9% had $5{\leq}AHI<20$, 13.2% had $20{\leq}AHI<40$, and 20.0% had $40{\leq}AHI$. The main problems for visiting our clinic were snoring(91.7%), sleep apnea(74.5%), excessive daytime sleepiness(8.0%), insomnia(4.3%), bruxism(1.1%) and attention deficit(0.5%). The mean value of frequency of interruptions of sleep was 1.6 and the most common reason was urination(46.3%). Epworth Sleepiness Scale(ESS) had a weak correlation with AHI(r=0.209, p<0.01). When we performed analysis of sleep questionnaires, there were significant differences in the mean values of AHI according to the severity of symptoms including snoring, daytime sleepiness, taking a nap and arousal state after wake(p<0.05). Conclusion : On the basis of statistical analysis of sleep questionnaires, the severity of subjective symptoms such as ESS, snoring, daytime sleepiness and arousal state after wake correlated with the AHI significantly. Therefore the sleep questionnaires can be useful instruments for prediction of the severity of sleep disorder, especially sleep-disordered breathing.

• Sleep Medicine and Psychophysiology
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• v.21 no.2
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• pp.51-60
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• 2014

A 'circadian rhythm' is a self-sustained biological rhythm (cycle) that repeats itself approximately every 24 hours. Circadian rhythms are generated by an internal clock, or pacemaker, and persist even in the absence of environmental time cues, collectively termed 'zeitgebers.' Although organisms generate circadian rhythms internally, they are entrained by environmental stimuli, particularly the light-dark cycle. Measurement of the endogenous melatonin rhythm provides relatively reliable surrogate way of assessing the timing of the internal circadian clock. Also, core body temperature and cortisol can be used as markers of circadian rhythms. The sleep-wake cycle, body temperature, and melatonin rhythm have a stable internal phase relationship in humans and other diurnal species. They play an important role in controlling daily behavioral rhythms including task performance, blood pressure, and synthesis and secretion of several hormones. In this review, we address not only the properties, methods of measurement, and markers of circadian rhythms, but also the physiological and psychological importance of human circadian rhythms.