• Sleep Medicine and Psychophysiology
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• v.26 no.1
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• pp.5-15
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• 2019

Chronotype (CT) is defined as an inter-individual difference in sleep-wake cycles and daily activities. Previous studies have suggested that this individual difference can influence our biological and psychological functioning. Literature regarding the psychometric properties and validity of CT measures are reviewed. We provide an overview of biological indicators (sleep-wake cycle, body temperature, cortisol, and melatonin) that are used for distinguishing two chronotypes: morningness (MT) and eveningness (ET). We also review the differences between CT in relation to personality traits and the occurrence of psychopathology. In addition, the methodological limitations of studies on CT are discussed. Finally, future research directions in terms of CT are proposed.

• Journal of Life Science
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• v.23 no.8
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• pp.1064-1072
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• 2013

Circadian rhythm is controlled by hormonal oscillations governing the physiology of all living organisms. In mammals, the main function of the pineal gland is to transform the circadian rhythm generated in the hypothalamic suprachiasmatic nucleus into rhythmic signals of circulating melatonin characterized by a largely nocturnal increase that closely reflects the duration of night time. The pineal gland has lost direct photosensitivity, but responds to light via multi-synaptic pathways that include a subset of retinal ganglion cells. Rhythmic control is achieved through a tight coupling between environmental lighting and arylalkylamine-N-acetyltransferase (AANAT) expression, which is the rhythm-controlling enzyme in melatonin synthesis. Previous studies on the nocturnal expression of AANAT protein have described transcriptional, post-transcriptional, and post-translational regulatory mechanisms. Molecular mechanisms for dependent AANAT expression provide novel aspects for melatonin's circadian rhythmicity. Extensive animal research has linked pineal melatonin for the expression of seasonal rhythmicity in many mammalian species to the modulation of circadian rhythms and to sleep regulation. It has value in treating various circadian rhythm disorders, such as jet lag or shift-work sleep disorders. Melatonin, also, in a broad range of effects with a significant regulation influences many of the body's physiological functions. In addition, this hormone is known to influence reproductive, cardiovascular, and immunological regulation as well as psychiatric disorders.

• Journal of Korean Neuropsychiatric Association
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• v.57 no.4
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• pp.276-286
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• 2018

Circadian rhythm is a periodic and continuous change in physiological, behavioral, and mental characteristics that occurs in most organisms on the Earth, because the Earth rotates in a 24-hour cycle. The circadian system regulates daily rhythms of physiology and behavior, such as the sleep/wake cycle, body temperature, hormonal secretion, and mood. The influence of circadian rhythm is very powerful, but limited research has addressed its effects. However, many recent studies have shown that circadian dysregulation may play an important role in the pathogenesis of bipolar disorder. This review study examined current and noteworthy studies, including the authors' own works, and proposes a possible clinical application of bipolar disorder based on evidence that circadian rhythm dysregulation in bipolar disorder may be a key pathogenetic mechanism.

• Sleep Medicine and Psychophysiology
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• v.29 no.2
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• pp.40-44
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• 2022

Bipolar disorders are a group of mood disorders characterised by relapsing mood episodes throughout the course of illness. Patients with bipolar disorders commonly present with various sleep problems. Patients in a manic episode generally show decreased need of sleep and those in a depressed episode frequently complain about hypersomnia. Current literature even points to evidence that patients with bipolar disorder in euthymic state may still show signs of sleep disturbances when compared to the general population. Clinicians may also note intricate interactions between changes of circadian rhythm and evolution of mood episodes in patients with bipolar disorder. Also, commonly prescribed medications which plays a crucial role in treatment of bipolar disorders including mood stabilisers and antipsychotic medications often cause significant weight gain over time. Being a risk factor of sleep apnoea, weight gain can predispose the patient to develop sleep apnoea. In this narrative review, we summarised current evidence and literature regarding characteristics of circadian rhythm and comorbid sleep apnoea in patients with bipolar disorder. We also present literature regarding implications of circadian disturbance and comorbid sleep apnoea in managing patients with bipolar disorder.

• Sleep Medicine and Psychophysiology
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• v.15 no.1
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• pp.12-16
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• 2008

Light therapy (also called light treatment or phototherapy) involves scheduled exposure to bright artificial light. Evidence-based treatments for sleep disorders especially for circadian rhythm sleep disorders include light therapy and pharmacotherapy. In clinical practice, many of patients with sleep problems tend to impair circadian rhythmicity. Considering that light is the most potent entraining agent of circadian rhythm, careful use of light therapy can be recommended for patients with several kinds of sleep disorders. I briefly review the possible therapeutic mechanisms and clinical applications of light therapy, focusing on circadian sleep disorders.

• Journal of Korean Biological Nursing Science
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• v.19 no.1
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• pp.48-54
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• 2017

Purpose: This study was done to identify the influence of severity of drinking problem, circadian rhythm and sleep quality in patients with alcohol use. Methods: A descriptive study design was utilized. Data were collected using self-report questionnaires from 139 patients with alcohol use disorder who were admitted to a psychiatric hospital in D city, Korea. The questionnaires included Alcohol Use Disorders Identification Test (AUDIT), Composite Scale of Morningness (CMS), Pittsburgh Sleep Quality Index (PSQI), and Korea sleep scale A. Data were analyzed using descriptive statistics, Pearson's correlation coefficients, and multiple regressions using the SPSS 20.0 program. Results: There was significant correlations among severity of problem drinking, circadian rhythm, sleep quality and sleep disorder. The significant factors influencing sleep disorder were severity of problem drinking(${\beta}=.12$, p= .042), circadian rhythm(${\beta}=-.14$, p= .039) and sleep quality(${\beta}=.63$, p= < .001). This model explained 56% of variance in sleep disorder(F = 57.34, p= < .001). Conclusion: The results of this study suggest that the development of sleep intervention programs for alcohol use disorder patients needs to consider severity of alcohol use, circadian rhythm and sleep quality, and sleep assessment and intervention are needed the early stage of the treatment and recovery process.

• Journal of Korean Biological Nursing Science
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• v.23 no.3
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• pp.227-236
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• 2021

Purpose: The purpose of this study was to investigate the sleep duration, social jetlag (SJL), and subjective sleep disturbance according to the individual chronotype in rotating shift nurses. Methods: A total of 344 rotating 3-shift nurses (mean age 28.67 years) were recruited at one university affiliated hospital. They completed the following questionnaires, which were used to assess their chronotype and sleep: the morningness-eveningness questionnaire (MEQ), self-reported sleep duration of work days (SDW_shift) and free days (SDF_shift) in each shift (day [D], evening [E], night [N]), and sleep disturbance (Insomnia severity index, ISI). SJL_shift was calculated as the difference in midsleep (MS=sleep onset+1/2 sleep duration) between work days (MSW) and free days (MSF). Results: Subjects were divided into 3 chronotype groups according to the MEQ; morning (MG, 4.4%) intermediate (IG, 57.8%), and evening groups (EG, 37.8%). SDW_D was shortest (4.68 hr) and SDF_E was longest (8.93 hr) in the EG. SJL_D was longest in the EG (3.77 hr), and SJL_N was longest in the MG (7.37 hr). The prevalence of sleep disturbance was 33.3% (MG), 29.6% (IG), and 40.0% (EG), respectively, without any statistical significance. Conclusion: In order to improve the sleep of shift workers, it is recommended that the evening chronotypes should reduce the day shifts and the morning chronotypes should reduce the night shifts. We also propose a study to determine whether these shift assignments can improve the sleep in shift nurses.

• Sleep Medicine and Psychophysiology
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• v.30 no.1
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• pp.13-21
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• 2023

The Seasonal Affective Disorder (SAD) is a disorder characterized by prolonged periods of depression and various physical and psychological symptoms experienced during specific seasons, typically winter. In this review aims to provide a comprehensive overview of SAD with a specific focus on psychophysiological aspects. Through the review from ancient times to the present, this paper explores the characteristics, causes, and underlying mechanisms of SAD. Particularly, it comprehensively reviews the research findings on the relationship between external factors such as light, sunlight, climate, and their association with SAD. Furthermore, the paper discusses the interplay between SAD and psychophysiological changes, along with the latest research trends in treatment and prevention strategies. By combining theoretical and practical perspectives on SAD, this article aims to provide a holistic understanding and offer suggestions for future research directions and clinical interventions.

• Journal of Korean Biological Nursing Science
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• v.25 no.4
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• pp.306-315
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• 2023

Purpose: This study aimed to evaluate the rest-activity circadian rhythm (RAR) using data obtained from wearable actigraph devices in hospitalized older adults with mild cognitive impairment (MCI), and to investigate its relationship with salivary alpha amylase (sAA). Methods: This secondary data analysis used data from the Hospitalized Older Adults' Cognition and Physical Activity Study. Actigraph data for 3-4 days were analyzed for RAR. RAR indices such as interdaily stability (IS), intradaily variability (IV), activity level during the most active 10-hour period and during the most least active 5-hour period, and relative amplitude (RA) were calculated. Data on sAA collected in the morning and general characteristics, including body mass index (BMI), were analyzed. Results: Data from 92 hospitalized older adults with MCI were analyzed. The IS, IV, RA were 0.23, 0.73, 0.88, respectively. The average level of sAA was 77.02 U/mL, and a higher level of sAA was significantly associated with better IS and RA in the regression analysis, while age, BMI, and cognitive level were not. BMI showed positive correlations with IS and RA. Conclusion: RAR in the hospitalized older adults with MCI was attenuated, showing especially low IS, which implies they failed to maintain regular and repetitive 24-hour RAR. Increased sAA and BMI were associated with robust RAR. Nurses need to pay attention to maintain robust RAR in hospitalized older adults with MCI, and strategies should be developed to improve their RAR.

• Sleep Medicine and Psychophysiology
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• v.7 no.2
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• pp.115-119
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• 2000

Objectives Summary: A 20-year-old man was presented with a history of difficult waking for 10 years. He suffered from morning headache, chronic fatigue and mild daytime sleepiness but had no history of irresistible sleep attack, cataplexy, hypnagogic hallucination or sleep paralysis. Methods: Night polysomnography (PSG), multiple sleep latency test (MSLT) and HLA-typing were carried out. Results: The PSG showed short sleep latency (4.0 min) and REM latency (2.5 min), increased arousal index (15.7/hour), periodic limb movements during sleep (PLMS index=8.1/hr) with movement arousal index 2.1/hr and normal sleep efficiency (97.5%). The MSLT revealed normal sleep latency (15 min 21 sec) and 4 times sleep-onset REM (SOREM). HLA-typing showed DQ6- positive, that corresponded at the genomic level to the subregion DQB1*0601, which was different from the usual locus in narcolepsy patients (DQB1*0602 and DQA1*0102). Conclusion: Differential diagnosis should be made with circadian rhythm disorder and other causes of primary waking disorder. The possibility of a variant type of narcolepsy could be suggested with an unusual clinical manifestation and a new genetic marker.