OBJECTIVES: Night shift workers suffer from sleep and daytime disturbances due to circadian misalignment. To investigate the role of environmental light in daytime sleep following 12 h-night shift work. METHODS: We enrolled 12 h-shift female nurses working at one university-affiliated hospital (n=10, mean age 26.6 years, shift work duration 3.8 years). This is a cross-over study to compare sleep between under light exposure (30 lux) and in the dark (<5 lux) following 12 h-night duty. Two sessions of experiments were underwent and the interval between sessions was about a month. Psychomotor vigilance test (PVT) had performed on awakening from sleep at each session and sleep-wake pattern had been monitored by actigraphy throughout the study period. Daytime sleep was also compared with night sleep of age-and gender matched daytime workers (n=10). RESULTS: Sleep parameters and PVT scores were not different between two light conditions. Activities during sleep seemed to be more abundant under 30 lux condition than in the dark, which was not significant. Compared to night sleep, daytime sleep of shift workers was different in terms of rapid eye movement (REM) sleep. Three shift workers showed sleep onset REM sleep and first REM sleep period was the longest during daytime sleep. CONCLUSIONS: Unexpectedly, daytime sleep of 12 h night shift workers was well-maintained regardless of light exposure. Early occurrence of REM sleep and shorter sleep latency during daytime sleep suggest that shift workers meet with misalignment of circadian rhythm as well as increased homeostatic sleep pressure drive.
Actigraphy ; Circadian Rhythm ; Cross-Over Studies ; Female ; Humans ; Polysomnography ; Sleep, REM

Obstructive sleep apnea (OSA) and dizziness are common conditions observed in the general population, and several epidemiological studies have reported an association between OSA and dizziness. Vestibular dysfunction, autonomic instability, and cerebellar degeneration secondary to recurrent hypoxia are implicated as mechanisms underlying dizziness in patients with OSA. Moreover, OSA is a risk factor for many diseases associated with dizziness, including Meniere disease, stroke, and psychiatric conditions. A dizziness questionnaire, vestibular function tests, and tests for autonomic function are useful for evaluation of OSA and concomitant dizziness. A growing body of evidence has shown that effective treatment of OSA including continuous positive airway pressure therapy reduces dizziness in these patients. Greater attention to dizziness is warranted in patients with OSA.

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

Melatonin and cortisol are clinically important for diagnosing sleep and mood disorders.We developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/ MS) assay for simultaneous measurement of salivary melatonin and cortisol concentrations according to the Clinical and Laboratory Standards Institute guidelines. Additionally, we compared the LC-MS/MS assay with immunoassays, ELISA (Direct Salivary Melatonin Elisa EK-DSM, Bühlmann Laboratories AG, Schönenbuch, Switzerland) and electrochemiluminescence immunoassay (Cortisol II, Roche, Mannheim, Germany), using 121 saliva samples. The LC-MS/MS assay exhibited good performance in terms of linearity, precision, accuracy, limit of detection, lower limit of quantification, extraction recovery, carry-over, and matrix effect. The LC-MS/MS assay and immunoassays showed strong correlation (Pearson’s r = 0.910 for melatonin, r = 0.955 for cortisol), but demonstrated a significant mean bias of 23.2% (range 54.0–143.7%) for melatonin and 48.9% (range 59.7–184.7%) for cortisol. Our LC-MS/MS assay provided more sensitive and reliable salivary melatonin and cortisol quantification results compared with immunoassays.

Background: and Purpose Epidemiological data on narcolepsy are rare in South Korea.We aimed to provide an overview of the burden of narcolepsy and its temporal trend in South Korea. Methods: Patients with narcolepsy were identified by their registration in the Rare and Intractable Disease (RID) register and the Health Insurance Review and Assessment database.Individuals registered in the RID program with the code V234 were considered as having ‘definite narcolepsy’, while those who claimed health insurance with G47.4 as the primary diagnostic code were considered as having ‘probable narcolepsy’. We estimated the annual prevalence, incidence, and medical costs of narcolepsy between 2010 and 2019. Results: The prevalence of definite narcolepsy was 8.4/100,000 in 2019, peaking at 32.0/100,000 in those aged 15–19 years. The prevalence was higher in males, with a relative risk of 1.72. The prevalence has increased over the past 6 years, with an average annual growth rate (AAGR) of 12.2%. The prevalence of probable narcolepsy was 10.7/100,000 in 2019. The incidence of definite narcolepsy increased up to 1.3/100,000 in 2019 with an AAGR of 7.1%. Annual medical expenditure for definite narcolepsy gradually increased up to 4.1 billion KRW in 2019, with a compound annual growth rate of 11.9%. Conclusions This study has provided the first nationwide estimates for narcolepsy in South Korea. The prevalence of diagnosed narcolepsy in South Korea was at the low end of the range of narcolepsy prevalence rates reported for other countries. However, the prevalence and incidence have been steadily increasing over the past decade.

Background: and PurposeSleep disturbance is common in patients with primary headache disorders. We were interest in whether poor sleep quality affects patients directly or via increases in the frequency and severity of headaches. To that end, we investigated the direct and indirect effects of sleep quality on the headache-related impact among patients with primary headache disorders. Methods: We analyzed migraine and tension-type headache (TTH) in patients included in the headache registry of our headache clinic from October 2015 to May 2018. We collected information on the headache frequency, severity, and psychological status. Sleep quality and headache-related impact were measured using the Pittsburgh Sleep Quality Index and Headache Impact Test-6, respectively. We performed path analyses with headache frequency and severity as covariates to determine the direct effect of sleep quality on the headache-related impact, and the indirect effects mediated by increases in the headache frequency and severity. Results: This study included 915 patients: 784 with migraine and 131 with TTH. Worse sleep quality was independently associated with greater headache-related impact in both patients with migraine and those with TTH. Path analysis revealed a direct effect (β=0.207,p<0.001) of sleep quality and an indirect effect mediated by headache frequency and severity (β=0.067, p=0.004) on the headache-related impact in migraine. In TTH, only direct effects of sleep quality on the headache-related impact were significant (β=0.224, p=0.004). Conclusions We suggest that poor sleep quality can directly increase the headache-related impact in both patients with migraine and TTH as well as indirectly by increasing the headache frequency and severity in patients with migraine.

Background: and Purpose: Organic light-emitting diodes (OLEDs) emit less blue light than traditional light-emitting diodes (LEDs), but the effects of OLED light exposure (LE) on melatonin and sleep have not been evaluated. Methods: Twenty-four healthy subjects (age 26.9±5.7 years; including 18 females) with the intermediate chronotype were exposed to three different light conditions [4,000 K 150 lux OLED LE, 4,000 K 150 lux LED LE, and dim light (DL) at <10 lux] for 6.5 h from 17:30 to 24:00, in a random order and with a 1-week interval. Participants entered the unit for the experiment at 16:00, and their daylight was measured by actigraphy from 8:00 to 16:00 during each session. Saliva samples for melatonin were taken every hour from 18:00 to 24:00. Sleep was monitored by polysomnography, and vigilance was evaluated by psychomotor vigilance test upon awakening. Results: Melatonin onset occurred at 21:11±01:24, 21:20±01:19, and 21:36±01:16 in the DL, OLED, and LED conditions, respectively. Melatonin onset was significantly delayed under LED LE compared to DL (p=0.007) but did not differ under OLED LE (p=0.245). Melatonin suppression, sleep parameters, and vigilance were similar among the three light conditions. The accumulated amount of daytime light in each session was negatively correlated with the melatonin onset time under the DL (rho=-0.634, p=0.002) and OLED (rho=-0.447, p=0.029) conditions, not under the LED condition (p=0.129). Conclusions Melatonin onset under OLED LE was not significantly delayed compared to DL.Exposure to sufficient daylight may advance melatonin onset even when a subject is exposed to OLED LE in the evening.

OBJECTIVES: Significant benefit of intravenous ferric carboxymaltose (FCM) for restless legs syndrome (RLS) has been demonstrated. However, clinical indicators to expect treatment response of RLS are not clarified. The aim of this study is to find out determinant factors to predict treatment outcome of FCM. METHODS: We enrolled consecutive 108 patients with RLS who visited sleep clinic and received FCM from April 2016 to November 2017. Obtained data were detailed history including international restless legs scale (IRLS) and questionnaires, comorbid diseases, medication. Complete blood cell count, serum iron, ferritin, and total iron-binding capacity were sampled before and after treatment. Treatment response was assessed about four weeks after FCM administration. Patients with more than 40% decrease on IRLS were classified into the responders. RESULTS: 99 patients (mean 54.5 y and 79 females) were included. 58 patients (58.6%) were classified to be responders. There were substantial differences in post-treatment IRLS and symptom reduction rate between responders (7.4±6.4, 77.5±18.6%) and non-responders (29.7±8.7, 7.4±10.3%). No significant differences were found in demographics, baseline IRLS, sleep, and mood status between two groups. Serum ferritin and transferrin saturation was significantly lower in responders (37.6 ng/mL, 25.0%) than non-responders (55.1 ng/mL, p=0.014 and 36.5%, p=0.001). Patients with a history of gastrectomy (n=8) showed an excellent response to FCM (83.8% of symptom reduction). Comorbid lumbosacral radiculopathy had lower response rate (29.4%). CONCLUSIONS: Peripheral iron compromised state and gastrectomy history may indicate good response to intravenous FCM in patients with RLS. Patients with lumbosacral radiculopathy tend to be poor responders to intravenous FCM.
Blood Cell Count ; Demography ; Ferritins ; Gastrectomy ; Humans ; Iron ; Radiculopathy ; Restless Legs Syndrome ; Transferrin ; Treatment Outcome

Neuromyelitis optica spectrum disorder (NMOSD) is a rare inflammatory demyelinating disease. Anti-aquaporin-4 antibodies serve as a specific biomarker, while other factors including antecedent infection may also play a role in the development of NMOSD. Abnormal cerebrospinal fluid (CSF) findings such as leukocytosis with concentration >50/mm3 are one of the characteristics of NMOSD, but these were not specific for identifying other infective neurological diseases. Here we describe a rare case of NMOSD with CSF findings suggestive of bacterial meningomyelitis.

Monoamniotic twin pregnancies are relatively rare, but perinatal mortality is high about 30-70%. The major cause of fetal death is cord accident, congenital anomalies, twin-twin transfusion syndrome, and intrauterine growth restriction. Especially cord entanglement occurs; perinatal mortality is about 50%. So the active management of monoamniotic twins to reduce the complication of cord entanglement is important. This is a case of monoamniotic twin pregnancy with cord entanglement and both fetuses survival by elective cesarean section at 32+4 weeks after medical amnioreduction and intensive fetal surveillance.
Cesarean Section ; Female ; Fetal Death ; Fetus ; Humans ; Perinatal Mortality ; Pregnancy ; Pregnancy, Twin