• Sleep Medicine and Psychophysiology
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• v.3 no.1
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• pp.15-24
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• 1996

After rapid eye movement(REM) sleep was idenified in 1953, a lively interest developed concerning a possible role of this kind of sleep in memory processes. The author reviewed studies relating REM to memory/learning. Many studies in animals and humans gave substantial evidence for relating REM sleep to memory function. The evidence supporting the position taken in this paper comes from experiments showing that : (1) learning session is followed by the significant augmentation of REM sleep : (2) REM sleep deprivation, prior to learning or immediately thereafter, impairs the formation of a permanent memory/learning : (3) there is a vulnerable period of time(eg, REM sleep "window") following succussful learning, during which REM sleep deprivation results in memory impairment : (4) theta rhythm which develops during REM sleep induces long-term potentiation in hippocampus : (5) there are some evidences providing the relationship of neurotransmitter systems to the maintenance of REM sleep and memory storage processes.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.1
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• pp.1-11
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• 2022

Purpose : Obesity is a major public health burden in developed countries and a well-known risk factor for cardiovascular disease. Short sleep duration is associated with obesity, as well as diabetes, heart disease and death. In modern society, habitual sleep restrictions seem unavoidable due to social obligations and work schedules along with a tendency toward decreased sleep time. Therefore, the purpose of this study is to examine the effect of differences in sleep time between weekdays and weekends on body mass index (BMI). Methods : This study involved 4,234 Korean adults aged 20 to 64 years based on data obtained from the 7th national health and nutrition examination survey (2016). All subjects were classified into the weekend catch-up sleep group (weekend CUS group). and the non catch-up sleep group (non-CUS group). Results : The longer the average sleep time, the lower was the BMI, and the larger the difference in sleep time between weekdays and weekends, the lower was the BMI. Compared with those with an average sleep time of 8 hours or more, obesity was 1.6-fold higher when the average sleep time was less than 6 hours, and 1.2-fold higher in the case of sleep time of 7 hours or more and less than 8 hours. When the difference in sleep time between weekdays and weekends was 0 or less, more than 0 hours but less than 1 hour, and more than 1 hour and less than 2 hours, the risk of obesity was 1.2-fold, 1.1-fold and 1.1-fold higher, respectively, compared with the risk associated with a sleep time difference of 2 hours or greater between weekdays and weekends. However, the difference was not statistically significant. Conclusion : Short sleep duration is positively associated with obesity. In addition, weekend catch-up sleep affects BMI.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.30 no.1
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• pp.114-116
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• 2008

Mania in psychiatry describes not only the state of temporary elation of the mood but also of the general mental function such as contents of a thought, thinking process, motivation, enthusiasm, interest, behavior, slumber and physical activities. The time of period when the above changes of mood, mental and behavioral disorder appear is called a manic episode. Postoperative mania is very rare and it has been reported only 5 times in english literature. It's an extremely rare case which has not yet been reported in Oral and Maxillofacial surgery. Patients normally deny the symptoms and it is easy to miss the diagnosis since the patient tends to seem content and happy. Patients show the following initial symptoms of mania - postoperative insomnia, atypical gregariousness, euphoria and unstability. Patients who are not disaffected with insomnia can also be included.

• Investigative Magnetic Resonance Imaging
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• v.21 no.2
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• pp.102-105
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• 2017

In adolescents, sleep deprivation problem is getting worse, and increased caffeine consumption is considered to relieve the stress caused by sleep deprivation and academic burden. In this study, immediate neurologic effects of caffeine intake on adolescents were evaluated in three high school students using the ${\gamma}-aminobutyric$ acid (GABA)/creatine ratio on magnetic resonance spectroscopy (MRS). MEGA-PRESS MRS and TE 135 ms single voxel MRS were performed in the anterior cingulate cortex before and after drinking a cup of coffee, which contained 104 mg of caffeine. GABA and creatine were measured on LCModel 6.3, respectively. In all three students, GABA/creatine ratios were decreased after caffeine intake. The GABA/creatine ratios obtained before caffeine intake were decreased after caffeine intake in all the three adolescents. In this preliminary study, caffeine intake caused an immediate decrease in the GABA/creatine ratio in the brain and it may be related to the neurologic effects of caffeine on an adolescent's brain.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.311-318
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• 2020

This was a basic study to ascertain the changes in sleep patterns and the factors disrupting sleep in hospitalized children. The participants were children aged 6 years or younger who had been hospitalized in an advanced general hospital in a particular region. A total of 81 participants were included, and for data analysis using SPSS/WIN 21.0. The results showed that children's sleep duration decreased significantly after hospitalization compared to before (p<.001), and there were significant differences in sleep onset latency (p<.001) and frequency of sleep deprivation (p<.001). Factors perceived by the children's mothers to disrupt sleep included the child's health state, noise in the ward, nurses' treatments, and lighting in the ward. This study verified that children's sleep quality and duration decreases during hospitalization, demonstrating the need to prepare measures to improve sleep in hospitalized children based on an understanding of changes in sleep patterns and disrupting factors.

• Sleep Medicine and Psychophysiology
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• v.9 no.2
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• pp.106-114
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• 2002

Objectives: Daytime sleepiness is a common symptom and is associated with sleep behavior, sleep deprivation, and night shift, etc. It is also one of the most important symptoms of sleep disorders like obstructive sleep apnea (OSA). According to our survey on Korean literature, a few studies have dealt with daytime sleepiness, and we have not been able to locate any study comparing normal subjects with polysomnography-proven sleep disorder patients regarding daytime sleepiness. We aimed at comparing daytime sleepiness among normal healthy daytime workers, medical students being expected to have daytime sleepiness due to chronic sleep deprivation, and patients having sleep disorders diagnosed with polysomnography. We also studied the association between subjective daytime sleepiness and objective polysomnographic findings in patients with sleep disorders. Methods: One hundred three hospital workers, 137 medical students, and patients with sleep disorders were studied. Sleep disorders included OSA, periodic limb movements in sleep (PLMS), insomnia, and narcolepsy. The degree of subjective sleepiness in each group was measured by the Korean version of Epworth sleepiness scale and compared. The relationship between polysomnographic findings reflecting severity of sleep disorder in each patient group and subjective sleepiness was analyzed. As for patients with narcolepsy, the relationship between the mean sleep latency and subjective sleepiness was studied. Results: There was a significant difference of ESS score (F=68.190, dF=5.752, p<0.001) among daytime workers, medical students, and sleep disorder patients. In OSA patient group, the degree of the sleepiness had no significant correlation either with mean O2 satuaration (p=0.062) or with RDI (p=0.807). In PLMS patient group, there was no correlation between periodic limb movement index (PLMI) and subjective sleepiness (p=0.761). In narcolepsy patient group, the subjective sleepiness had no correlation with mean sleep latency measured with MSLT (p=0.055). Conclusion: We found a significant difference of subjective sleepiness among daytime workers, medical students, and patients with sleep disorders. However, no consistent correlation was found between severity of subjective sleepiness and objective polysomnographic findings reflecting severity of each sleep disorder. This research confirms that the evaluation of subjective sleepiness is important clinically, but it cannot substitute the objective measures such as nocturnal polysomnography and MSLT.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.19 no.3
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• pp.156-161
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• 2008

Objectives: The purpose of this study was to investigate the prevalence of sleep problems in Korean elementary school children and the differences in sleep problems elated to their school grade and gender. Methods : One public elementary school in Dae-gu, Korea as randomly selected. And, parents who agreed to participate this study were asked to complete a modified version of Tucson Children's Assessment of Sleep Apnea screening questionnaire (TuCASA). Results: The most common sleep problem was 'falling asleep in vehicle (44.2%)' and the prevalence rate of this problem differed by school grade. The prevalence rate of falling asleep while watching TV before 8 P.M. (8.0%), daytime fatigue (21.9%) and nocturnal enuresis during the past 6 months (5.3%) were significantly differed by school grade. The prevalence rate of falling asleep while doing home work, falling sleep during a lesson, snoring and bruxism were 12.6%, 1.0%, 26.7% and 13.2% respectively. Although these rates did not show any differences between grades, snoring as more in boys and daytime fatigue was more in girls. Conclusion: This study demonstrates that many elementary school children may have various sleep problems. Lower grade elementary schoolers had sleep problems which related to euro-developmental factors, whereas higher grade elementary schoolers had sleep problems related to sleep deprivation and stress. Finally, more female schooler showed signs of fatigue or sleepiness than male schoolers.

• Journal of the Korean Society of School Health
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• v.28 no.1
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• pp.1-9
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• 2015

Purpose: The purpose of this study is to examine the effect of sleep duration on suicidal ideation in Korean adolescents. Methods: This study used the data drawn from Korea Youth Risk Behavior Web-Based Survey in 2013. A total data of 63,301 adolescents were included in the analysis. Included variables were general characteristics, health status variables, hours of sleep, and suicidal ideation. For sample description weighted percentage and means were used. Rao-Scott ${\chi}^2$ test and simple and multiple logistic regression with dummy variables were conducted with use of SAS 9.2. Results: Among general characteristics and health status variables, gender, grade, school level, school achievement, family's economic status, living with parents, subjective health, happiness, stress, and feeling of despair were found to be significantly related to suicidal ideation. Rates of having suicidal ideation were 22.4% in the case of students with less than 5 hours of sleep and 12.9% in students with 8 or more hours of sleep. After controlling general characteristics and subjectively perceived variables, hours of sleep was still significantly related to suicidal ideation. That is, compared to adolescents with 8 hours or more of sleep, those with less than 5 hours of sleep showed significantly higher risk for having suicidal ideation (adjusted odds ratio: 1.20, p<.001). Conclusion: These findings suggest that short sleep has negative effects on psychological health in adolescents. Particularly, less than 5 hours of sleep has harmful effect on adolescents' increased risk for having suicidal ideation.

• Yonsei Medical Journal
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• v.59 no.9
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• pp.1138-1142
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• 2018

This study aimed to analyze the impact of sleep deprivation (SD) on cardiac, hemodynamic, and endothelial parameters and to determine whether these are sustained with increased periods of SD. The study included 60 healthy men (mean: age $31.2{\pm}6.3years$; body mass index $24.6{\pm}2.6kg/m^2$). Hemodynamic parameters, parameters of myocardial contractility, spectral analysis of heart rate (HR) and blood pressure (BP) variability, and the sensitivity of arterial baroreflex function were evaluated. Biochemical tests were performed to assess L-arginine (L-Arg) and asymmetric dimethylarginine (ADMA) levels in reflection of endothelial nitric oxide synthase ability. Measurements of cardiovascular system parameters were obtained at 9 a.m. (baseline) on the first day of the study and 9 a.m. (24-h SD), 1 p.m. (28-h SD), and 5 p.m. (32-h SD) on the second day. Blood samples for evaluating biochemical parameters were obtained at baseline and after 24-h SD. ANOVA Friedman's test revealed a significant effect for time in relation to HR (${\chi}^2=26.04$, df=5, p=0.000), systolic BP (${\chi}^2=35.98$, df=5, p=0.000), diastolic BP (${\chi}^2=18.01$, df=5, p=0.003), and mean BP (${\chi}^2=28.32$, df=5, p=0.000). L-Arg and ADMA levels changed from $78.2{\pm}12.9$ and $0.3{\pm}0.1$ at baseline to $68.8{\pm}10.2$ and $0.4{\pm}0.1$ after 24-hr SD, respectively (p=0.001, p=0.004). SD in healthy men is associated with increases in BP, which appear to occur after 24 hours of SD and are maintained over increasing periods of SD. The observed hemodynamic changes may have resulted due to disordered vascular endothelial function, as reflected in alterations in L-Arg and ADMA levels.

• Sleep Medicine and Psychophysiology
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• v.13 no.1
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• pp.15-21
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• 2006

Introduction: The objective of the present study was to investigate bedtime, rise time and time-in-bed of Korean college students, separately on weekday and on weekend and to compare them. In addition, this study also aimed to evaluate the influence of gender, age and grade on the above sleep parmeters in Korean college students. Methods: Information regarding bedtime and rise time, separately on weekday and on weekend, of Korean college students were obtained by self-administered questionnaire. Questionnaires of 1,825 students (1,416 females and 409 males, age 18-30；mean age $21.1{\pm}2.2$) were used for statistical analyses. Results: Korean college students retired to bed 50 minutes later (00：49 on weekday；01：40 on weekend；t=39.67, p<0.001), rose 1 hour 58 minutes later (07：52 on weekday；09：50 on weekend；t=39.46, p<0.001), and slept 1 hour 8 minutes longer (t=13.33, p<0.001) on weekend. Compared to male students, female students had earlier rise time (t=8.96, p<0.01；t=3.89, p<0.01) and earlier bedtime both on weekday and weekend (t=7.10, p<0.01；t=6.04, p<0.01), and shorter time-in-bed on weekday (t=1.99, p<0.01). In addition, rise time delay and time-in-bed increase on weekend were more prominent in female students than in male students (t=3.41, p<0.01; t=3.68, p<0.01). Grade was correlated with bedtime and rise time on weekday (${\beta}=0.1022$, p<0.01；${\beta}=0.1009$, p<0.01), bedtime and time-in-bed on weekend (${\beta}=0.1096$, p<0.01；${\beta}=-0.0990$, p<0.01), and differences between week-day and weekend of the rise time and the time-in-bed (${\beta}=-0.0906$, p<0.01；${\beta}=-0.1115$, p=0.02). Conclusions: In this study, Korean college students had earlier bedtime/rise time and shorter time-in-bed on weekday than on weekend. These findings suggest that weekday sleep-wake schedule of Korean college students may be advanced relative to their biological sleep-wake cycle and that this discrepancy may be associated with weekday sleep deprivation. In addition, differences of sleep patterns between weekday and weekend were more prominent in female students and students with lower grade. Therefore, discrepancy between weekday sleep-wake schedule and biological sleep-wake cycle, as well as weekday sleep deprivation, might be more serious in female or lower-grade students.