• Genomics & Informatics
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• v.18 no.4
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• pp.38.1-38.9
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• 2020

Chronotype is an important moderator of psychiatric illnesses, which seems to be controlled in some part by genetic factors. Clock genes are the most relevant genes for chronotype. In addition to the roles of individual genes, gene-gene interactions of clock genes substantially contribute to chronotype. We investigated genetic associations and gene-gene interactions of the clock genes BHLHB2, CLOCK, CSNK1E, NR1D1, PER1, PER2, PER3, and TIMELESS for chronotype in 1,293 healthy Korean individuals. Regression analysis was conducted to find associations between single nucleotide polymorphism (SNP) and chronotype. For gene-gene interaction analyses, the quantitative multifactor dimensionality reduction (QMDR) method, a nonparametric model-free method for quantitative phenotypes, were performed. No individual SNP or haplotype showed a significant association with chronotype by both regression analysis and single-locus model of QMDR. QMDR analysis identified NR1D1 rs2314339 and TIMELESS rs4630333 as the best SNP pairs among two-locus interaction models associated with chronotype (cross-validation consistency [CVC] = 8/10, p = 0.041). For the three-locus interaction model, the SNP combination of NR1D1 rs2314339, TIMELESS rs4630333, and PER3 rs228669 showed the best results (CVC = 4/10, p < 0.001). However, because the mean differences between genotype combinations were minor, the clinical roles of clock gene interactions are unlikely to be critical.

• Korean Journal of Biological Psychiatry
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• v.28 no.2
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• pp.58-69
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• 2021

Objectives The aim of this study was to examine the association between the sleep pattern, chronotype (midpoint of sleep on free days) and the depressive symptoms in adults aged 19 years and over in Korea. This study also investigated the mediating effect of perceived usual stress (PUS) and self-rated health (SRH) on the association between chronotype and depressive symptoms. Methods Among the subjects of the 7th Korea National Health and Nutrition Examination Survey (KNHANES) 2016 and 2018, 16142 adults aged 19 or over responded to the survey and finally 8604 were analyzed according to the exclusion conditions. Logistic regression analysis was conducted to see the risk of depressive symptoms, suicidal ideation over sleep pattern, chronotype. Finally, mediation analysis was performed in order to clarify how PUS and SRH are associated to chronoytpe and depression. Results After controlling for potential covariates, weekly sleep duration < 5 hours, ≥ 10 hours was associated with depressive symptoms. And late bed time sleeping after am 1:00 and later midpoints of sleep was associated with a higher level of depressive symptoms. Additionally, the PUS and SRH between chronotype and depressive symptoms showed a serial multiple mediation effect. Conclusions Short or long sleep duration, late bed time and later midpoints of sleep on free days are associated with depressive symptoms. Furthermore, the mechanism between chronotype and depressive symptoms needs to be further clarified by identifying the serial multiple mediation effects of PUS and SRH.

• Journal of Korean Biological Nursing Science
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• v.21 no.1
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• pp.70-76
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• 2019

Purpose: The aim of this study is to identify the influence of chronotype and self-efficacy on drinking problem in undergraduate students. Methods: A cross-sectional survey design was adopted for the 177 undergraduate students in D, G, and K city in 2017. The data was analyzed for descriptive statistics, t-test, ANOVA, Pearson's correlation coefficients and multiple regression analysis using the SPSS 18.0 program. Results: Chronotype (${\beta}=-.31$, p< .001), self-efficacy (${\beta}=27$, p< .001) and religion (${\beta}=-.19$, p= .005) were identified as the factors influencing drinking problem in the subjects. The model explained 19% of variance in drinking problem (F= 11.36, p< .001). Conclusion: It is necessary to develop and apply a program that would consider chronotype and self-efficacy factors to reduce the drinking problem in undergraduate students.

• Journal of the Ergonomics Society of Korea
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• v.19 no.3
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• pp.1-12
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• 2000

The Korean version of the morningness-eveningness questionnaire (MEQ) and sleep habits inventory were administered to 1,038 Korean male daytime workers and were analyzed according to age and chronotype to determine what these factors reveal about sleep habits in view of phase difference of circadian rhythm. The mean and distribution of scores on the MEQ moved significantly toward the morning type with aging. Bedtimes and waking times were progressively later from the morning, intermediate, to evening types, and were also earlier with aging. Preferred bedtimes and waking times showed more distinct differences than did the habitual times in each chronotype. The percentage of subjects who answered that sleep length was 'short', mood upon waking was 'bad', and variabilities of bedtime and sleep length were 'large' were greater in the young and evening types than in the elder and morning types, respectively. These findings suggested that subjects were shifted toward the morning type and the phase of circadian rhythm had moved forward with aging. Preferred bedtime and waking time were a better reflection of individual circadian rhythms than habitual bedtime and waking time.

• Journal of the Korean society of biological therapies in psychiatry
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• v.24 no.3
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• pp.194-201
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• 2018

Objectives : Some studies have reported that chronotypes, among several factors, could contribute to problematic drinking. However, there is little evidence confirming this relationship between chronotype and problematic drinking based on gender differences in mood disorder. This study is to investigate the difference of the relationship between chronotype and problematic drinking according to gender differences in mood disorder. Methods : Two hundred fifteen patients with mood disorder were recruited. Problematic drinking and chronotypes were assessed by the Alcohol Use Disorder Identification Test in Korea(AUDIT) and the Korean translation of composite scale of morningness(KtCS). We analyzed the correlation between KtCS and AUDIT using Pearson's correlation, and compared AUDIT scores according to chronotypes classified by KtCS between male and female patients using analysis of variance(ANOVA). Results : There was no significant difference in AUDIT scores between the male and female patients(t=0.91, p=0.183). In female patients, eveningness had significantly higher AUDIT scores than other chronotypes(F=0.199, p=0.033). Meanwhile, in male patients, there was no significant difference in AUDIT score among chronotypes(F=0.008, p=0.933). Conclusion : This study suggests that eveningness might be associated with problematic drinking in female patients who suffer from mood disorder. It also suggests that chronotherapeutical treatment might be able to help improve the course in female patients with mood disorder. In the future, a large-scale prospective study is needed to confirm these results.

• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.1
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• pp.148-167
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• 2020

Today, digital shoppers express increasingly complex buying behavior. They can use multiple channels for shopping and also they can switch from one to another channel almost effortlessly, in the result of engaging in omnichannel shopping behavior. A few years ago, consumers were using brick and mortar stores to make their purchases. However, nowadays, they possess different digital devices (mobile and/or desktop) to search for different alternatives and to make a better shopping choice. These devices (mobile and desktop) are different and offer unique benefits to consumers. However, there has been very little research that has treated mobile and desktop devices separately. Perhaps this study is the pioneer when it comes to investigating the effect of regulatory focus (prevention vs. promotion) and chronotype (morning and evening person) on a sample of university students using desktop and mobile channels for their shopping. The findings from a sample of 312 digital consumers (mobile and/or desktop) confirmed that the desktop channel provides a greater fit for morning-type respondents and that the mobile channel offers better value for evening-type respondents in e-retail. Furthermore, promotion-focused shoppers favor the mobile channel, and prevention-focused shoppers favor the desktop channel. The new insights and contributions of this study provide a better understanding of digital consumers to help sellers to develop a more effective e-retail strategy.

• Korean Journal of Biological Psychiatry
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• v.21 no.1
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• pp.14-20
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• 2014

Objectives The current study investigated the putative relationship between chronotype and suicidality or bipolarity in patients with major depressive disorder (MDD). Method Nineteen outpatients who met the criteria for MDD according to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders-text revision were recruited for the current study. The subjects were divided into two subgroups based on their Basic Language Morningness (BALM) scores (dichotomized according to the median BALM score). The Loudness Dependence of Auditory Evoked Potentials (LDAEP) was evaluated by measuring the auditory event-related potentials before beginning medication with serotonergic agents. In addition, K-Mood Disorder Questionaire (K-MDQ), Beck Scale for Suicidal Ideation (BSS), Beck Hopelessness Scale (BHS), Barratt Impulsiveness Scale (BIS) were applied. Results The K-MDQ, BSS, BHS, BIS score was higher for the eveningness group than for the morningness group. However, the LDAEP, Hamilton Depression Rating Scale, Hamilton Anxiety Scale scores did not differ significantly between them. There were negative correlations between the total BALM score and the total K-MDQ, BSS, and BHS scores (r=-0.64 and p=0.0033, r=-0.61 and p=0.0055, and r=-0.72 and p=0.00056, respectively). Conclusions Depressed patients with eveningness are more vulnerable to the suicidality than those with morningness. Eveningness is also associated with bipolarity.

• 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.

• Sleep Medicine and Psychophysiology
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• v.29 no.1
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• pp.21-28
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• 2022

Objectives: Our study aimed to investigate the relationship between the anxiety at first year and chronotype and sleep quality at third year in medical students. We also investigated the association between sleep quality, chronotype, depression and resilience at third year. Methods: Fifty two medical students (36 males, 69%, aged 21 ± 0.93) in first year, and forty four medical students (31 males, 70.5%, aged 23.05 ± 0.99) at third year answered Beck Depression Inventory 2, Beck anxiety inventory, Insomnia severity index-K, Composite scale of morningness and Conner-Davidson Resilience scale-10. Multiple linear regression analysises were performed to identify predictors of chronotype, sleep quality and resilience. Results: Higher anxiety (β = -0.434, p = 0.006) at first year was significant predictor of eveningness at third year, while lower anxiety score (β = 0.606, p < 0.001) at first year was significant predictor of sleep quality at third year. Lower sleep quality (β = -0.314, p = 0.042) and eveningness (β = 0.315, p = 0.041) were associated with low resilience at third year. Also, Lesser depression (β = -0.717, p < 0.001) was associated with higher resilience at third year. Conclusion: Our study showed that higher anxiety in first year had significantly related with eveningness and poor sleep quality at third year. In addition, higher sleep quality, morningness and less depression had significantly associated with better resilience at third year.