• Sleep Medicine and Psychophysiology
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• v.7 no.1
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• pp.27-33
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• 2000

Objectives: The sensitivity and accuracy of thermistor airflow signal has been debated. The purposes of this study were to compare apnea-hypopnea index(AHI) detected from a conventional thermistor signal and a nasal pressure transducer of airflow(NPT), to evaluate the value of NPT for the diagnosis of upper airway resistance syndrome(UARS), and to measure airway pressure fluctuations which produced respiratory arousals in UARS by naso-oro-esophageal manometer catheter. The subjects were 30 patients with obstructive sleep apnea syndrome [mild(540), 10), and 6 UARS patients. Airway resistance arousal in this study was defined as arousals which were not associated with apnea or hypopnea of thermistor signal, but showed significant decrease of nasal airflow pressure just before arousal and a prompt recovery of nasal airflow pressure after arousal. The airway pressure fluctuations were measured during 260 airway resistance arousals observed in 10 patients with OSAS, 2 with UARS. Results: Mean AHIs of patients with OSAS were 33.4 by thermistor and 48.4 by NPT. The AHIs of mild, moderate and severe OSAS groups were 10.2, 32.1, 65.4 respectively by thermistor and 23.1, 45.9, 76.4 by NPT. The mean AHI of patients with UARS was 3.2 by thermistor and 10.8 by NPT. The mean AHI of patients with nonspecific arousals was 2.7 by thermistor and 4.4 by NPT. The mean airway pressure changes during respiratory arousals of different groups were $8.7\;cmH_2O$ in mild OSAS, $11.4\;cmH_2O$ in moderate OSAS, $24.7\;cmH_2O$ in severe OSAS and $6.6\;cmH_2O$ in UARS. Conclusion: The nasal pressure transducer of airflow was more sensitive and accurate for assessing respiratory disturbances of patients with OSAS and was extremely helpful for the diagnosis of UARS without esophageal pressure monitoring. From the results, we would like to propose carefully the NPT diagnostic criteria for sleep disordered breathing as follows: NPT-AHI 5-15 $\rightarrow$ UARS, 15-35 $\rightarrow$ mild OSAS, 35-55 $\rightarrow$ moderate OSAS and >55 $\rightarrow$ severe OSAS.

• Sleep Medicine and Psychophysiology
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• v.7 no.1
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• pp.18-26
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• 2000

Objectives: To investigate the airway narrowing patterns by multi-level airway pressure(MAP) monitoring during sleep and to evaluate the value of CT scan taken during waking and sleep apneic periods to identify the level of airway narrowing(LAN) in patients with obstructive sleep apnea syndrome(OSAS). Methods: Eleven patients with OSAS underwent a night polysomnography with continuous MAP monitoring by 4-sensor(placed at nasopharynx, caudal-uvula, hypopharynx, esophagus) or 2-sensor(placed at caudal-uvula and esophagus) catheter. All patients had cine CT at five levels of high retro and alatal, low retropalatal, retroglossal, epiglottis and hypopharynx during awake and sleep periods. In each patient, LAN determined by CT scan($LAN_{CT}$) during sleep apnea was compared with LAN by MAP monitoring($LAN_{MAP}$). Results: MAP monitoring showed that four patients(36%) had a single pattern of LAN while the other seven patients(64%) showed two or more different LANs in different apneic episodes. Velopharynx was the most common level of frequently observed airway narrowing during sleep apnea(63.6%). However, a single pattern of airway narrowing was more frequent(72.7%) in airway CT during sleep apnea. Velopharynx was the most common narrowest level also in apneic CT(66%). In comparing $LAN_{CT}$ with $LAN_{MAP}$, the $LAN_{CT}$ of five patients(45.5%) were high-concordant, those of another five(45.5%) low-concordant, and that of one(9%) discordant with $LAN_{MAP}$. Conclusions: Cine CT scan during the awake state or sleep apnea may not reflect the LAN correctly in OSAS because most patients showed two or more different airway narrowing patterns during different episodes of sleep apnea in each patient.

• Sleep Medicine and Psychophysiology
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• v.7 no.1
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• pp.43-50
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• 2000

Objectives: Obstructive sleep apnea syndrome(OSAS) is known to be associated with the changes of autonomic nervous system (ANS). Nasal continuous positive airway pressure(nCPAP) treatment was found to correct abnormal ANS changes in OSAS but it remains to be further clarified. We aimed to assess the effects of nCPAP on ANS manifested on electrocardiogram, using spectrum analysis in the subjects with OSAS. Methods: Digital polysomnography was performed in 18 patients with OSAS(mean age $43.7{\pm}16.6$ years ; 17 males, 1 female ; mean respiratory disturbance index (RDI) $48.6{\pm}20.9$) for one baseline and another CPAP nights. From each night, 300 continuous beats of ECGs without artifact were chosen from both stage 2 sleep and REM sleep and they were used for power spectrum analysis. We compared between baseline and CPAP nights the heart rate variability including VLF(very low frequency power), LF (low frequency power), HF(high frequency power), R-R means, R-R variance, and LF/HF ratio, using Wilcoxon signed ranks test. Results: In all patients, nCPAP proved to be effective in relieving apneas and snoring. During nCPAP night compared with baseline night, decreases in VLF(p<0.05), LF(p<0.01), and R-R variance(p<0.05) were found in stage 2 sleep, and decreased LF(p<0.05) was found in REM sleep. No significant differences in each sleep stage were found in other variables between the two nights. Conclusion: Our findings suggest that OSAS increases the activity of sympathetic nervous system and nCPAP application effectively decreases the activity. And nCPAP does not appear to influence the parasympathetic nervous activity in OSAS.

• Sleep Medicine and Psychophysiology
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• v.7 no.1
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• pp.51-59
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• 2000

Objectives: It is been reported that sleep patterns change significantly during the adolescent years. In Korea, the sleep patterns of adolescents have not been investigated systematically. The authors performed preliminary study about sleep patterns of middle and high school students in Seoul before nationwide study. Methods: The authors selected one of middle and high schools located in typical middle class area in Seoul. The study was performed during the periods when examination or vacation did not affect the sleep cycle. Fifty to one hundred male and female students were selected from one school year each. One of investigators explained the purposes and methods of this study to the students and gave additional explanation to the teachers in charge. We designed a questionnaire for subjects to describe the nap time, bedtime, sleep latency, total sleep time, rise time and sleep efficiency, and the students recorded sleep logs for seven days including weekend. Eight hundred three students answered the questionnaires. Among them, we selected the subjects who recorded sleep logs at least three days and filled up the questionnaires completely. Finally, seven hundred seventy one subjects were included in this study. Weekend was defined as the time from Saturday morning to Sunday morning, and Sunday sleep patterns were treated separately. Results: Across the six school years, school-night bedtimes were delayed one hundred twenty four minutes and school-ight rise times were advanced by thirty five minutes. School-night total sleep times were decreased by one hundred fifty eight minutes, and weekend bedtimes were delayed by one hundred twenty five minutes. The students tended to oversleep on weekends, and the mean of weekend oversleep was ninety six minutes. But, bedtime in weekends was not delayed. Daytime sleep, sleep latency and sleep efficiency were not changed greatly across six school years. Total sleep time of female students was decreased significantly between third middle school year and first high school year, but time of male students was decreased between first and second high school year. Conclusion: It is supposed that sleep deficiency of middle and high school students in Seoul was due to delayed bedtimes and advanced rise times across the school years.

• Sleep Medicine and Psychophysiology
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• v.22 no.1
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• pp.30-34
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• 2015

Obesity hypoventilation syndrome (OHS) is characterized by severe obesity, excessive daytime sleepiness, hypoxemia and hypercapnea. Because OHS mimics pulmonary hypertension or cor pulmonale, clinicians should recognize and treat this syndrome appropriately. A 58-year-old female visited the emergency room because of dyspnea. She was obese and had kyphoscoliosis. The patient also experienced snoring, recurrent choking during sleep and daytime hypersomnolence which worsened after gaining weight in the recent year. The arterial blood gas analysis showed she experienced hypoxemia and hypercapnea not only during nighttime but also daytime. We suspected OHS and the patient underwent polysomnography to confirm whether obstructive sleep apnea was present. During the polysomnography test, sleep obstructive apnea was observed and apnea-hypopnea index was 9.2/hr. The patient was treated with bilevel positive airway pressure therapy (BiPAP). After BiPAP for 4 days, hypoxemia and hypercapnia were resolved and she is currently well without BiPAP. We report a case successfully treated with clinical improvement by presuming OHS early in a patient who had typical OHS symptoms, even while having other conditions which could cause hypoventilation.

• Sleep Medicine and Psychophysiology
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• v.22 no.1
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• pp.25-29
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• 2015

Objectives: The pathophysiology of restless legs syndrome (RLS) has not been fully elucidated. Oxidative stress might play a role in the development of RLS and other antipsychotic-induced side effects such as tardive dyskinesia. In the present study, we investigated whether the glutathione S-transferase (GST) gene polymorphisms are associated with antipsychotic-induced RLS in schizophrenia. Methods: We assessed antipsychotic-induced RLS symptoms in 190 Korean schizophrenic patients using the diagnostic criteria of the International Restless Legs Syndrome Study Group. The GST-M1, GST-T1 and GST-P1 loci were analyzed using PCR-based methods. Results: We divided the subjects into 2 groups: those with RLS symptoms (n = 96) and those without RLS symptoms (n = 94). There were no significant differences in the distributions of the GST-M1 genotypes (${\chi}^2=3.56$, p = 0.059), GST-T1 (${\chi}^2=0.51$, p = 0.476) and GST-P1 (${\chi}^2=0.57$, p = 0.821) between the 2 groups. Comparison of the RLS score among genotypes of the GST-M1 (t = -1.54, p = 0.125), GST-T1 (t = -0.02, p = 0.985) and GST-P1 (F = 0.58, p = 0.560) revealed no significant difference. Conclusion: These data suggest that GST gene polymorphisms do not confer increased susceptibility to RLS symptoms in schizophrenic patients. Future studies are necessary to evaluate the possible influences of other candidate genes involved in the reactive oxygen species system.

• Sleep Medicine and Psychophysiology
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• v.22 no.1
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• pp.11-19
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• 2015

Objectives: Whether daytime sleepiness is proportional to the severity of sleep apnea in obstructive sleep apnea syndrome (OSAS) is controversial. In this study we investigated how insomnia severity affects the association between daytime sleepiness and sleep apnea severity in OSAS. Methods: The present study included 235 male subjects who were diagnosed with OSAS based on clinical history and nocturnal polysomnography. Pearson's correlation analysis was conducted among sleep and mood-related self-reported data, polysomnographic data and demographic data of all subjects. Based on Pittsburgh Sleep Quality Index (PSQI), the subjects were divided into 2 groups; group A (n = 75; $PSQI{\leq}5$) and group B (n = 160; PSQI > 5). Partial correlation analysis was performed between the Epworth Sleepiness Scale (ESS) and other data in both groups. Multiple linear regression analysis was conducted to investigate the factors which affected the ESS in group A. Results: Pearson's correlation analysis showed weak or non-existent correlations between ESS and apnea severity data such as apnea-hypopnea index (AHI) (r = 0.148, p = 0.023), apnea index (AI) (r = 0.137, p = 0.036), hypopnea index (HI) (r = 0.058, p = 0.377), oxygen desaturation index (ODI) (r = 0.149, p = 0.022) and arousal total index (ATI) (r = 0.129, p = 0.048). Positive correlations between ESS and apnea severity data such as AHI ($r_p=0.313$, p = 0.008), AI ($r_p=0.339$, p = 0.004), ODI ($r_p=0.289$, p = 0.015) and ATI ($r_p=0.256$, p = 0.031) were observed only in group A. Multiple regression analysis showed that AI (t = 2.996, p = 0.004) and BAI (t = 2.721, p = 0.008) were associated with ESS in group A. Conclusion: The correlation between daytime sleepiness and sleep apnea severity was shown only in group A. This result suggests that associations between daytime sleepiness in OSAS and sleep apnea severity will become prominent when controlling for insomnia-related variables.

• Sleep Medicine and Psychophysiology
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• v.19 no.1
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• pp.22-26
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• 2012

Objectives: The percentage of positional sleep apnea in obstructive sleep apnea (OSA) varies in different reports from 9% to 60%. If there is a positional dependency in patients with OSA, positional therapy alone could be successful in treating about 50% of all OSA cases. The aim of this report is to compare anthropomorphic and polysomnographic data between the positional sleep apnea group and non-positional sleep apnea group with OSA whose conditions were diagnosed in our sleep clinic. Methods: This is a retrospective study of anthropomorphic and polysomnographic data of patients with OSA who was performed a nocturnal polysomnography. Positional sleep apnea was defined as having a supine apnea-hypopnea index (AHI) of twice or more compared to the AHI in the non-supine position. The patients were divided in the positional sleep apnea group and the non-positional sleep apnea group. Results: In 101 patients with OSA, 81 were male, and the mean age was $49.2{\pm}11.9$ years. Seventy-six (75.2%) were diagnosed as the positional sleep apnea. Waist to hip ratio and body mass index (BMI) were significantly higher in non-positional sleep apnea group. The frequency of severe OSA was significantly higher in this group. In the positional sleep apnea group, nocturnal sleep quality was better preserved, and consequently these patients were less sleepy during daytime. AHI was significantly lower and minimal arterial oxygen saturation during sleep was significantly higher in this group. Conclusion: The percentage of positional sleep apnea in OSA was 75.2%. AHI, BMI, and waist to hip ratio were lower in the positional sleep apnea group. These patients have less severe breathing abnormalities than the non-positional sleep apnea group in polysomnography.

• Sleep Medicine and Psychophysiology
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• v.17 no.1
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• pp.21-27
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• 2010

Objectives: It is well established that primary insomnia affects the activity of autonomic nervous system. We tried to know how the activity of autonomic nervous system during night sleep changes by analyzing correlation between heart rate variability (HRV) index and the variables related with sleep structure in primary insomnia. Methods: Thirty three subjects (mean age: $36.2{\pm}14.2$ years, male:female=15:18) who were diagnosed with primary insomnia were selected for the study. Nocturnal polysomnography (NPSG) was carried out on each subject and correlation was analyzed between high frequency/low frequency ratio (LF/HF ratio), one of HRV indices and the variables related with sleep structure which were calculated from NPSG. Results: When age and sex were controlled, LF/HF ratio showed negative correlations with slow wave sleep and stage 2 sleep, respectively ($r_p$=-0.43, p=0.01; $r_p$=-0.37, p=0.04). On the other hands LF/HF ratio showed a positive correlation with arousal index ($r_p$=0.65, p<0.001). The activity of autonomic nervous system responded differentially depending on the change of sleep structure in primary insomnia. Especially the increase of arousal index and the decrease of slow wave sleep and stage 2 sleep which are the components of non-REM sleep provoked hyperactivity of sympathetic nervous system. Conclusion: This study suggests that the typical change of sleep structure in primary insomnia can negatively impact on cardiovascular system.

• Sleep Medicine and Psychophysiology
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• v.9 no.1
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• pp.41-47
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• 2002

Objectives: In a number of simulated night shift studies, timed exposure to bright light improves sleep quality and work performance. We evaluated the effect of bright light on adaptation to night shift work with a field study. Methods: Five female nurses working shifts at Korea University Hospital were recruited for participation in this study. We investigated two series of six consecutive shift rotations comprising three day and three night shifts, using wrist Actigraphy, the Stanford Sleepiness Scale, Visual-analogue scales, STIM and tympanic membrane temperature for daytime sleep quality, alertness, subjective feeling, attention performance, and temperature rhythm. The subjects were exposed to bright light (2,500 lux) from 24:00 to 04:00 a.m. on three consecutive night shifts during the second series, whereas they worked under normal lightening (650 lux) conditions during the first series. Results: Actigraphic assessment of daytime sleep showed no significant difference between the first and third night shift in both baseline and light exposure phase. The mean lowest temperature shifted earlier during baseline phase but not during the light exposure phase. Also, the score for subjective feelings of depression, anxiety, physical discomfort and sleepiness was significantly higher in the third night shift than the first during baseline phase but not during the light exposure phase. Attention and attention switching ability was significantly improved in the third night shift compared to the first night during the light exposure phase but there were no significant changes during the baseline phase. Conclusion: This result suggests that there were no significant differences between the two phases in measures of quality of daytime sleep, but subjective feelings, attention and alertness were enhanced during light exposure. Although some placebo effects and learning effects might influence this result, bright light exposure between midnight and 4:00 a.m. may improve adaptation to night shift. In future, further controlled studies with a larger sample size, including melatonin measurement, are needed for real shift workers.