Inter-individual differences in the human circadian system: a review

Psychometric properties of the Turkish reduced morningness and eveningness questionnaire

The aim of this study was to examine the psychometric properties of the 5-item Turkish Reduced Morningness-Eveningness Questionnaire (rMEQ) for the first time. The study involved 875 university students in an adaptation and validation study. Participants completed the rMEQ, MEQ, Depression Anxiety Stress Scale-21 (DASS-21), Insomnia Severity Index (ISI), Barratt Impulsiveness Scale Short Form (BIS-SF), and Oxford Happiness Questionnaire Short Form (OHQ-SF). The factor structure, convergent validity, internal consistency, sensitivity, and specificity of the rMEQ were examined. The confirmatory factor analysis showed that the rMEQ had a one-dimensional structure with good fit indices (χ2/df = 2.94, CFI = 0.990, TLI = 0.979, RMSEA = 0.047, and SRMR = 0.019). There was a significantly strong correlation between rMEQ and MEQ. In addition, we found a significantly weak correlation between rMEQ and DASS-21, ISI, BIS-SF, and OHQ-SF. The internal consistency coefficients of rMEQ were Cronbach's α = 0.706 and McDonald's ω = 0.740. The sensitivity and specificity of rMEQ were 83.3%-92.7% for morning types and 86.3%-87.3% for evening types. The Turkish rMEQ has adequate psychometric properties and can be used to assess an individual's chronotype.

Secretion of glucagon, GLP-1 and GIP may be affected by circadian rhythm in healthy males

BACKGROUND

Glucagon is secreted from pancreatic alpha cells in response to low blood glucose and increases hepatic glucose production. Furthermore, glucagon enhances hepatic protein and lipid metabolism during a mixed meal. Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are secreted from gut endocrine cells during meals and control glucose homeostasis by potentiating insulin secretion and inhibiting food intake. Both glucose homeostasis and food intake have been reported to be affected by circadian rhythms and vice versa. In this study, we investigated whether the secretion of glucagon, GLP-1 and GIP was affected by circadian rhythms.

METHODS

A total of 24 healthy men with regular sleep schedules were examined for 24 h at the hospital ward with 15 h of wakefulness and 9 h of sleep. Food intake was standardized, and blood samples were obtained every third hour. Plasma concentrations of glucagon, GLP-1 and GIP were measured, and data were analyzed by rhythmometric statistical methods. Available data on plasma glucose and plasma C-peptide were also included.

RESULTS

Plasma concentrations of glucagon, GLP-1, GIP, C-peptide and glucose fluctuated with a diurnal 24-h rhythm, with the highest levels during the day and the lowest levels during the night: glucagon (p < 0.0001, peak time 18:26 h), GLP-1 (p < 0.0001, peak time 17:28 h), GIP (p < 0.0001, peak time 18:01 h), C-peptide (p < 0.0001, peak time 17.59 h), and glucose (p < 0.0001, peak time 23:26 h). As expected, we found significant correlations between plasma concentrations of C-peptide and GLP-1 and GIP but did not find correlations between glucose concentrations and concentrations of glucagon, GLP-1 and GIP.

CONCLUSIONS

Our results demonstrate that under meal conditions that are similar to that of many free-living individuals, plasma concentrations of glucagon, GLP-1 and GIP were observed to be higher during daytime and evening than overnight. These findings underpin disturbed circadian rhythm as a potential risk factor for diabetes and obesity.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT06166368. Registered 12 December 2023.

Development and validation of a French version of the morningness-eveningness questionnaire

The aim of this study was to validate a French version (FMEQ) of the morningness-eveningness questionnaire (MEQ). Study 1 consisted of a translation by experts and an evaluation. The FMEQ and MEQ were proposed to 19 bilingual participants (age = 38.7 ± 13.7 years). Strong correlations between MEQ and FMEQ were obtained for most items. Study 2 tested the factorial structure and reliability of the FMEQ on a sample of 187 participants (20.46 ± 1.31 years). The confirmatory factor analysis indicated that the model had a good fit (χ2/df = 1.8; SRMR = 0.057) and a good reliability (Cronbach's alphas = 0.8). Concerning the temporal stability (20 participants: 20.48 ± 1.04 years), the Pearson r correlation coefficient for test-retest reliability was 0.87 (p < 0.001). Study 3 examined the predictive validity with 42 participants (19.52 ± 2.08 years). The global score of the FMEQ was significantly correlated with the time of peak temperature, wake-up time and bedtime. We did not observe superiority of a three-factors solution of the FMEQ. From now on, French subjects chronotype could be rigorously scored, and results from MEQ and FMEQ could be compared.

Is evening chronotype associated with higher alcohol consumption? A systematic review and meta-analysis

A broader understanding of whether and to what extent chronotype should be considered a risk factor for alcohol consumption is needed. The aim of this systematic review was to summarize the evidence on the association between evening chronotype and alcohol consumption. A systematic search of observational studies on this association was conducted in the PubMed, Scopus, Web of Science, Cochrane Library and PsycINFO databases up to April 30th, 2023. Random-effect models estimated the pooled odds ratio (OR) of alcohol consumption according to chronotype. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and Quality Assessment tool for Observational Cohorts and Cross-sectional Studies from the National Heart, Lung and Blood Institute were followed. A total of 33 studies involving 28 207 individuals (age range: 18-93 years) were included in this review. Overall, most studies indicated a higher volume and frequency of alcohol consumption in evening-type individuals than in individuals with different chronotypes. Additionally, a meta-analysis including 13 studies showed that evening-type individuals were 41% more likely to consume alcohol than those with other chronotypes (OR = 1.41, 95% confidence interval: 1.16-1.66; I2 = 38.0%). Limitations of the present findings are the predominance of cross-sectional studies and varied definitions of alcohol consumption. The available evidence supports an association between the evening chronotype and alcohol consumption. The evening-type population, especially young adults, is a specific target for educational interventions for preventing or reducing alcohol consumption.PROSPERO number: CRD42022343778.

Validity of the Persian version of the Munich ChronoType Questionnaire (MCTQIR)

PURPOSE

Currently, the most useful questionnaire for determining the chronotype is the Munich ChronoType Questionnaire (MCTQ). It determines chronotype based on sleep-wake behavior on workdays and work-free days and uses the mid-sleep time on free days (MSF), corrected for accumulated sleep debt over the work week to classify chronotype (MSFsc). Our study aimed at validating Persian version of the MCTQ.

METHODS

Participants completed the Persian version of the MCTQ, reduced Morningness-Eveningness Questionnaire (rMEQ), Epworth sleepiness scale (ESS), and demographic characteristics.

RESULTS

The study sample was comprised of 250 Iranian men and women (mean age 34 years, age range 30 to 58 years, 113 men). Results showed that there is a significant negative relationship between the components of MCTQ and rMEQ, and the strongest relationship related to the MSF index. The results also showed that MCTQ parameters were not significantly related to the ESS scale. Cut-off values of MSFsc for chronotype categories were determined by inter-quartile range (Q25% = 3.44, Q50% = 4.68, and Q75% = 5.75).

CONCLUSIONS

Like the MCTQ in other languages, the Persian version of the MCTQ is a reliable tool for assessing chronotype.

What a difference a year makes: Objective rest/activity patterns, circadian phase markers, and sleep quality before and during the COVID-19 pandemic

OBJECTIVES

The COVID-19 pandemic led to numerous changes in sleep duration, quality, and timing. The goal of this study was to examine objective and self-reported changes in sleep and circadian timing before and during the pandemic.

METHODS

Data were utilized from an ongoing longitudinal study of sleep and circadian timing with assessments at baseline and 1-year follow-up. Participants had baseline assessment between 2019 and March 2020 (before pandemic) and 12-month follow-up between September 2020 and March 2021 (during pandemic). Participants completed 7 days of wrist actigraphy, self-report questionnaires, and laboratory-collected circadian phase assessment (dim light melatonin onset).

RESULTS

Actigraphy and questionnaire data were available for 18 participants (11 women and 7 men, Mean = 38.8 years, SD = 11.8). Dim light melatonin onset was available for 11 participants. Participants demonstrated statistically significant decreases in sleep efficiency (Mean = -4.11%, SD = 3.22, P = .001), worse scores on Patient-Reported Outcome Measurement Information System sleep disturbance scale (Mean increase = 4.48, SD = 6.87, P = .017), and sleep end time delay (Mean = 22.4 mins, SD = 44.4 mins, P = .046). Chronotype was significantly correlated with change in dim light melatonin onset (r = 0.649, P = .031). This suggests that a later chronotype is associated with a greater delay in dim light melatonin onset. There were also non-significant increases in total sleep time (Mean = 12.4 mins, SD = 44.4 mins, P = .255), later dim light melatonin onset (Mean = 25.2 mins, SD = 1.15 hrs, P = .295), and earlier sleep start time (Mean = 11.4 mins, SD = 48 mins, P = .322).

CONCLUSION

Our data demonstrate objective and self-reported changes to sleep during the COVID-19 pandemic. Future studies should look at whether some individuals will require intervention to phase advance sleep when returning to previous routines such as returning to office and school settings.

The relationship of quality of life and acne severity with chronotype and insomnia in patients with acne vulgaris

This study aimed to examine the relationship between acne severity and quality of life, insomnia, and chronotype. This study included 151 patients diagnosed with acne vulgaris, aged 18-30 years. A sociodemographic data form was completed by the clinician, and acne severity was evaluated using the Global Acne Grading System (GAGS). The Visual Analogue Scale (VAS), Acne Quality of Life Scale (AQLS), Hospital Anxiety Depression Scale (HADS), Insomnia Severity Index (ISI), and Morningness-Eveningness Questionnaire (MEQ) were completed by the participants. There was a significant difference between the MEQ scores of the participants who were divided into three groups according to the severity of global acne, as mild, moderate, and severe. In the post hoc analysis, the MEQ scores of the patients with mild acne were determined to be significantly higher than the scores of the patients with moderate and severe acne. A statistically significant negative correlation was observed between the GAGS scores and the MEQ scores. In addition, a statistically significant positive correlation was found between the participants' ISI scores and AQLS scores. Considering the variables related to chronotype and sleep in the treatment planning for patients with acne vulgaris may be appropriate within the scope of integrative treatment.

The association of dietary approaches to stop hypertension (DASH) and Mediterranean diet with mental health, sleep quality and chronotype in women with overweight and obesity: a cross-sectional study

PURPOSE

Mental and sleep disorders are global public health problems, especially in Middle Eastern countries, and are significantly associated with circadian rhythm. This study sought to investigate the association between the dietary approaches to stop hypertension (DASH) and Mediterranean diet scores and mental health, sleep quality, and circadian rhythm.

METHODS

We enrolled 266 overweight and obese women, and depression, anxiety, and stress scale (DASS) score, Pittsburgh Sleep Quality Index (PSQI), and Morning-Evening Questionnaire (MEQ), were assessed. The Mediterranean and DASH diet score was measured using a validated semi-quantitative Food Frequency Questionnaire (FFQ). The physical activity was evaluated using the International Physical Activity Questionnaire (IPAQ). Analysis of variance and analysis of covariance, chi-square, and multinomial logistic regression tests were used as appropriate.

RESULTS

Our results showed that there was a significant inverse association between adherence to the Mediterranean diet and mild and moderate anxiety scores (p < 0.05). In addition, there was an inverse association between adherence to the DASH diet and the risk of severe depression and extremely severe stress scores (p < 0.05). Moreover, higher adherence to both dietary scores was associated with good sleep quality (p < 0.05). There was a significant relationship between circadian rhythm and the DASH diet (p < 0.05).

CONCLUSION

A significant association exists between a DASH and Mediterranean diet with sleep status, mental health, and chronotype in women of childbearing age with obesity and overweight.

LEVEL OF EVIDENCE

Level V, Cross-sectional observational study.

The eveningness chronotype is associated with nightmare distress and dream recall: a cross-sectional study

Dreaming may be affected by sleep behavior; however, evidence of the effect of chronotypes on dreaming is limited. We investigated sleep patterns, dream recall, and nightmare distress according to chronotypes. This cross-sectional study retrospectively enrolled adult participants (age > 18 years) who visited a sleep laboratory between 2016 and 2021 and underwent standard polysomnography (PSG) and completed a self-reported questionnaire. Patients with major sleep disorders were excluded. Chronotypes and dreaming components were assessed using the Korean version of the morningness-eveningness questionnaire and a nine-item dreaming questionnaire (nightmare distress and dream recall), respectively. Among healthy participants without major sleep disorders, the eveningness chronotype correlated with better dream recall than the morningness and intermediate chronotypes. Participants with the eveningness chronotype were younger and more likely to be unmarried than those with the other chronotypes. No significant chronotype-based difference was observed in the subjective measurements of sleep quality, insomnia, daytime sleepiness, depression, and anxiety or in respiration and movement events on PSG. In multivariate linear regression analysis, the chronotypes were independently related to nightmare distress (b = - 0.296; p = 0.002) and dream recall (b = - 0.334; p = 0.002). The apnea-hypopnea index was associated with nightmare distress (b = - 0.209; p = 0.029) and dream recall (b = - 0.189; p = 0.044). Depression was positively correlated with nightmare distress (b = 0.450; p = 0.002). Dream recall was best in the eveningness group among healthy adults. Greater eveningness was associated with higher nightmare distress and better dream recall. Further research is needed to understand the role of chronotypes in dreaming.

The intrinsic variance of beauty judgment

Recall memory and sequential dependence threaten the independence of successive beauty ratings. Such independence is usually assumed when using repeated measures to estimate the intrinsic variance of a rating. We call "intrinsic" the variance of all possible responses that the participant could give on a trial. Variance arises within and across participants. In attributing the measured variance to sources, the first step is to assess how much is intrinsic. In seven experiments, we measure how much of the variability across beauty ratings can be attributed to recall memory and sequential dependence. With a set size of one, memory is a problem and contributes half the measured variance. However, we showed that for both beauty and ellipticity, with set size of nine or more, recall memory causes a mere 10% increase in the variance of repeated ratings. Moreover, we showed that as long as the stimuli are diverse (i.e., represent different object categories), sequential dependence does not affect the variance of beauty ratings. Lastly, the variance of beauty ratings increases in proportion to the 0.15 power of stimulus set size. We show that the beauty rating of a stimulus in a diverse set is affected by the stimulus set size and not the value of other stimuli. Overall, we conclude that the variance of repeated ratings is a good way to estimate the intrinsic variance of a beauty rating of a stimulus in a diverse set.

Factors Underpinning the Shift to Eveningness during Early Adolescence: Pubertal Development and Family Conflicts

Biological and psychosocial factors have been related to the shift to eveningness during early adolescence but it is necessary to study them from a longitudinal perspective. This longitudinal study examined the contribution of these factors to the onset of a shift towards eveningness in early adolescence. A sample of 440 (49.9% boys) Spanish adolescents were assessed for pubertal development, family conflicts, and morningness/eveningness. The same measures were taken twice at the age of 12 and one year later (T1: M = 12.47, SD = 0.75 and T2: M = 13.64, SD = 0.78). Pubertal development and family conflicts were considered predictors of morningness/eveningness in a mixed-effects multilevel model. The developmental shift towards eveningness appeared in girls but not in boys. The shift was related to more advanced pubertal development and more conflicts in the family. This study has implications for shaping healthy sleep habits in adolescents and possible interventions focused on family dynamics.

Beyond sleep: A multidimensional model of chronotype

Chronotype can be defined as an expression or proxy for circadian rhythms of varied mechanisms, for example in body temperature, cortisol secretion, cognitive functions, eating and sleeping patterns. It is influenced by a range of internal (e.g., genetics) and external factors (e.g., light exposure), and has implications for health and well-being. Here, we present a critical review and synthesis of existing models of chronotype. Our observations reveal that most existing models and, as a consequence, associated measures of chronotype have focused solely or primarily on the sleep dimension, and typically have not incorporated social and environmental influences on chronotype. We propose a multidimensional model of chronotype, integrating individual (biological and psychological), environmental and social factors that appear to interact to determine an individual's true chronotype with potential feedback loops between these factors. This model could be beneficial not only from a basic science perspective but also in the context of understanding health and clinical implications of certain chronotypes as well as designing preventive and therapeutic approaches for related illnesses.

Sleep and Circadian Rhythm in Relation to COVID-19 and COVID-19 Vaccination-National Sleep Survey of South Korea 2022

BACKGROUND

Currently, information on sleep and circadian patterns in relation to COVID-19 or vaccination remains limited. We aimed to investigate sleep and circadian patterns according to history of COVID-19 and COVID-19 vaccination side effects.

METHODS

We used data from the National Sleep Survey of South Korea 2022, a nationwide cross-sectional population-based survey regarding sleep-wake behaviors and sleep problems among Korean adults. Analysis of covariance (ANCOVA) and logistic regression analyses were performed to explore the different sleep and circadian patterns according to the history of COVID-19 or self-reported side effects of the COVID-19 vaccination.

RESULTS

The ANCOVA showed that individuals with a history of COVID-19 presented a later chronotype than individuals without a history of COVID-19. Individuals who had experienced vaccine-related side effects had a shorter sleep duration, poorer sleep efficiency, and worse insomnia severity. Multivariable logistic regression analysis showed a later chronotype related to COVID-19. A short sleep duration, poorer sleep efficiency, and worse insomnia severity were associated with self-reported side effects of the COVID-19 vaccination.

CONCLUSIONS

Individuals who recovered from COVID-19 had a later chronotype than those without a history of COVID-19. Individuals who had experienced vaccine-related side effects presented with poorer sleep than those without side effects.

Time-of-Day Effect on Postural Balance and Its Associations with Menopausal Symptoms in Postmenopausal Women

Postmenopausal women suffer from postural balance issues. During a 24-hour time span, postural performance undergoes radical changes as influenced by the circadian rhythm. In this study, we aimed to investigate time-of-day effects on postural balance in postmenopausal women and balance relationships with menopausal symptoms. Two groups of women, aged 40-50 years, participated in this study: a menopausal group and a control group. We evaluated their postural balance and menopausal symptoms (mood, sleepiness and fatigue) in five sessions over the course of a day: at 06:00 hours, at 10:00, at 14:00, at 18:00 and at 22:00. The results showed that postural balance (center of pressure area (CoP_area)) values of postmenopausal women were significantly worse (p < .05) at 22:00. Moreover, at this time-of-day, participants in the menopausal group were more tired, less vigilant and experienced a lower mood. We found negative correlations between postural balance and both mood and fatigue levels. However, there was no time-of-day effect on postural balance, mood, fatigue, and sleepiness among participants in the control group. Thus, time-of-day should be considered a factor to control when assessing postural balance and designing intervention studies for postmenopausal women; and it is important for these women to be cautious of fall risks at night, as they are then less stable than at other times-of-day.

Time-related meal patterns and breakfast quality in a sample of Iranian adults

BACKGROUND

Some evidence shows that meal timing is associated with diet quality. We aimed to investigate the relationship between meal timing and breakfast quality in a sample of Iranian adults.

METHODS

This cross-sectional study was conducted on 850 men and women living in Tehran, Iran. Dietary data was recorded by three non-consecutive 24-h dietary recalls. The Breakfast Quality Index (BQI) was calculated. Time-related meal patterns included the interval between the first and last meal (eating and fasting window), frequency of meals, length of sleep, and time of first and last eating occasion. The multiple linear regression analysis was used to identify the relationships between time-related meal patterns and BQI.

RESULTS

The mean (95% CI) of BQI was 4.52 (4.45-4.65) and the maximum was 8. Bread, cheese, vegetables, fruits, energy, and carbohydrate intake showed positive associations with BQI scores. Longer fasting time showed a positive association with fruits (β (CI 95%)) (0.11 (0.0003-0.005), and vegetable consumption (0.12 (0.009-0.07)) and BQI score (0.39 (0.001-0.06)). Time of first eating occasions indicated a negative association with protein and fat intake and BQI score. Time of last eating occasions showed a positive association with vegetables consumption and BQI score. The longer length of sleep was associated with a higher BQI score. The frequency of meals was significantly and positively related to energy and macronutrients intake and BQI.

CONCLUSION

Earlier first and last meal, longer sleep length, longer fasting window, and a greater meal frequency were associated with a better breakfast quality.

The Effect of Chronotype on Risk-Taking Behavior: The Chain Mediation Role of Self-Control and Emotional Stability

BACKGROUND

Although previous studies indicate that chronotype might be associated with risk-taking behavior, the specific mechanism has not been thoroughly discussed. This study aimed to fill this gap by exploring the mediating role of self-control and the chain mediating role of self-control and emotional stability between chronotype and risk-taking behavior.

METHODS

A total of 547 Chinese college students between 18 and 24 years old were selected to complete the Morningness-Eveningness Questionnaire (MEQ), Self-Control Scale (SCS), Eysenck's Personality Questionnaire-neuroticism (EPQ-N), and Adolescent Risk-Taking Questionnaire: Risk Behavior Scale (ARQ-RB) to assess chronotype, risk-taking behavior, self-control, and emotional stability, respectively. Hayes' PROCESS macro for SPSS was used to test the relationships among these variables.

RESULTS

Our result showed significant positive correlations among chronotype, self-control, emotional stability, and significant negative correlations between self-control, emotional stability, and risk-taking behavior. We also found that chronotype had a significant predictive effect on risk-taking behavior in the chain mediation model. Specifically, chronotype affected risk-taking behavior through two pathways: the separate mediating role of self-control and the serial mediation pathway of self-control → emotional stability.

CONCLUSIONS

Our study provides direct evidence that chronotype is associated with risk-taking behavior. The results showed that the predictive function of chronotype was mediated by self-control and emotional stability. This study provides a new perspective on preventing and reducing risk-taking behavior.

Changes in dietary intake, chronotype and sleep pattern upon Ramadan among healthy adults in Jeddah, Saudi Arabia: A prospective study

Background

Notable lifestyle changes can occur in Ramadan due to the sudden shift in eating routine with fasting during daylight hours. This study aimed to examine the changes in dietary intakes, chronotype, sleep pattern, and physical activity level before and during Ramadan in healthy adults.

Methods

This study was conducted in Jeddah city, Saudi Arabia, and convenience sampling was used. To compare dietary, chronotype and sleep pattern changes before and during Ramadan, data were collected in two separate periods: the first period was 2 months before Ramadan, and the second period was during the last 3 weeks of Ramadan. Dietary intake was assessed using 24-h food recall and chronotype using Morningness-Eveningness Questionnaire. Daytime sleepiness and sleep duration were assessed using the Epworth sleepiness scale and a sleep diary for seven consecutive days, respectively. Anthropometric measurements were also taken across the study periods.

Results

A total of 115 adults (96 females and 19 males) were included in the study. Significant increases in daily calorie and carbohydrate intakes during Ramadan than before Ramadan were noted (calorie intake: 1,482.9 ± 536.4 kcal/day before Ramdan vs. 1,635.5 ± 635.1 kcal/day during Ramadan; carbohydrate intake: 180.8 ± 72.1 g/day before Ramadan vs. 202.6 ± 88.7 g/day during Ramadan; p < 0.05). Chronotypes and daytime sleepiness were also associated significantly with Ramadan fasting. A significant slight reduction in body weight during Ramadan was observed (66.4 ± 18.1 kg before Ramdan vs. 66.1 ± 17.8 kg before Ramadan and during Ramadan, respectively; p < 0.05).

Conclusion

This study indicates that Ramadan diurnal fasting was associated with greater calorie and carbohydrate intake, changes in chronotype, and daytime sleepiness. The study also suggests that Ramadan diurnal fasting model may be a promising weight loss strategy.

The psychometric properties of the Spanish version of the Morningness-Eveningness Stability Scale improved (MESSi) in adolescents

The aim of the present study was to adapt the Morningness-Eveningness-Stability Scale improved (MESSi) to the Spanish adolescent population, testing its factor structure and construct validity. The participants were 725 adolescents (52.9% girls; M = 14.8, SD = 1.99) who completed the MESSi, the Morningness Eveningness Scale of Children (MESC), questions about sleep habits adapted from the School Sleep Habits Survey, and self-reported academic performance. The psychometric results support a three-factor model with the factors of morning affect, eveningness, and distinctness, which show good internal consistency. The pattern of correlations between MESSi and the other measures was in the expected direction. The MESC correlated positively with morning affect and negatively with eveningness, whereas distinctness was uncorrelated. Boys reported higher morningness, whereas girls reported higher distinctness. Eveningness was negatively related to academic performance. Overall, the results support the validity and reliability of the Spanish adolescent version of the MESSi.

Association between chronotype, tobacco use or alcohol use, and high-risk drinking by age group: The Seventh Korea National Health and Nutrition Examination Survey (VII: 2016-2017)

OBJECTIVES

To analyze the association between chronotype, tobacco use or alcohol use, and high-risk drinking by age group and examine the differences across groups.

METHODS

A cross-sectional descriptive study design was adopted. Data from 12,189 participants aged ≥ 12 years from 2016 to 2017, excluding shift workers, were gathered from the Korea Disease Control and Prevention Agency's Seventh Korea National Health and Nutrition Examination Survey. A general linear model was used to determine the aforementioned associations and differences across age groups. Chronotype was measured using the Munich Chronotype Questionnaire. It was divided into quintiles. We used current tobacco use, monthly alcohol use, and high-risk drinking as indexes of tobacco use and alcohol use. These data were extracted from the national representative data.

RESULTS

Among adolescents and adults, both tobacco use and alcohol use showed a linear increasing trend, although it was greatest among adolescents. In older adults, tobacco use showed a linear increasing trend with delayed chronotype. When the chronotypes of all age groups were aggregated, high-risk drinking was higher in both extreme types, Quintiles 1 and 5.

CONCLUSIONS

Tobacco use and alcohol use were mostly associated with delayed chronotype. Therefore, interventions to address delayed chronotype at all ages are needed. As the trend of increase in tobacco use and alcohol use in adolescents was higher than in other age groups, a special strategy is required aimed at this population. Moreover, both extreme chronotypes should be considered risk factors for high-risk drinking.

Effect of diurnal changes on dichotic listening in younger adults with normal hearing

Background

Diurnal changes can be defined as the time of the day over an individual's performance level for different activities that involve physical and mental tasks.

Objective

The current study aimed to evaluate the effect of diurnal changes in scores obtained for the Dichotic Consonant-Vowel paradigm by young adults with normal hearing sensitivity.

Method

Based on the ‘Morningness-Eveningness questionnaire’ given by Horne & Ostberg, the subjects were divided into moderately-morning, intermediate and moderately-evening categories. The Dichotic Consonant-Vowel tests were performed during morning and evening, and the right ear, left ear and double correct scores were compared between morning and evening for each category.

Results

There was significant diurnal changes noted for moderately morning and evening categories, where morning-type individuals performed better during morning and evening-type individuals performed better during the evening. The scores of intermediate individuals remained unchanged between morning and evening test results.

Conclusion

Diurnal change is a phenomenon associated with an individual's biological clock mechanism. Hence, attention and inhibitory controls aid them in carrying out tasks that require sufficient physical and mental efforts. The current study suggests that clinicians and researchers consider diurnal changes as an extraneous variable that could affect the reliability of the Dichotic Consonant-Vowel test results.

Predicting Math Performance of Middle Eastern Students: The Role of Dispositions

The present research examines the contribution of individual differences in chronotype and self-efficacy to the math performance of male and female students in STEM and no-STEM majors. Questionnaires assessing the selected individual differences were distributed to students of Middle Eastern descent enrolled in math courses of the general education curriculum. Summative assessment indices were used to measure performance comprehensively across the entire semester (course grades) and as a one-time occurrence (final test grades). The contribution of morningness and self-efficacy to both course and test performance of STEM students was sensitive to the interaction of gender and major. Instead, neither factor contributed to no-STEM students’ course and test performance. These findings were used to plan improvements in the instruction and advising of students in STEM majors, thereby complying with a key tenet of action research.

Quantifying daily rhythms with non-negative matrix factorization applied to mobile phone data

Human activities follow daily, weekly, and seasonal rhythms. The emergence of these rhythms is related to physiology and natural cycles as well as social constructs. The human body and its biological functions undergo near 24-h rhythms (circadian rhythms). While their frequencies are similar across people, their phases differ. In the chronobiology literature, people are categorized into morning-type, evening-type, and intermediate-type groups called chronotypes based on their tendency to sleep at different times of day. Typically, this typology builds on carefully designed questionnaires or manually crafted features of time series data on people’s activity. Here, we introduce a method where time-stamped data from smartphones are decomposed into components using non-negative matrix factorization. The method does not require any predetermined assumptions about the typical times of sleep or activity: the results are fully context-dependent and determined by the most prominent features of the activity data. We demonstrate our method by applying it to a dataset of mobile phone screen usage logs of 400 university students, collected over a year. We find four emergent temporal components: morning activity, night activity, evening activity and activity at noon. Individual behavior can be reduced to weights on these four components. We do not observe any clear categories of people based on the weights, but individuals are rather placed on a continuous spectrum according to the timings of their phone activities. High weights for the morning and night components strongly correlate with sleep and wake-up times. Our work points towards a data-driven way of characterizing people based on their full daily and weekly rhythms of activity and behavior, instead of only focusing on the timing of their sleeping periods.

Change in circadian preference predicts sustained treatment outcomes in patients with unipolar depression and evening preference

STUDY OBJECTIVES

Eveningness is associated with worse outcomes in depression. It remained unclear if eveningness could be altered with chronobiological therapy and whether such a change would predict long-term outcomes of depression.

METHODS

Data from a randomized controlled trial of 5-week adjunctive bright light therapy with a gradual advance protocol conducted in 91 adult patients with nonseasonal unipolar depression and eveningness (Morningness-Eveningness Questionnaire, score ≤ 41) was examined. "Change of eveningness" was defined by Morningness-Eveningness Questionnaire score over 41 at posttreatment week 5 and "persistent change of eveningness" was defined as maintenance of Morningness-Eveningness Questionnaire score > 41 throughout the follow-up period from week 5 to posttreatment 5 months.

RESULTS

Thirty-three participants (36%) had change of eveningness at week 5. Generalized estimating equations models showed that a change of eveningness at week 5 predicted a 2-fold increase in remission of depression over the 5-month follow up (odds ratio = 2.61 95% confidence interval 1.20-5.71, P = .016). Twenty-five participants (75.7%) had a persistent change and were more likely to achieve a remission of depression over the 5-month follow up (odds ratio = 3.18, 95% confidence interval: 1.35-7.50, P = .008).

CONCLUSIONS

One-third of the patients with depression changed their evening-preference after 5-week of chronotherapeutic treatment, and such change predicted a higher likelihood of depression remission over 5 months of follow-up.

CLINICAL TRIAL REGISTRATION

Registry: Chinese Clinical Trial Registry; Name: Adjunctive light treatment in major depressive disorder patients with evening chronotype-A randomized controlled trial; URL: https://www.chictr.org.cn/showprojen.aspx?proj=11672; Identifier: ChiCTR-IOR-15006937.

CITATION

Chan JWY, Chan NY, Li SX, et al. Change in circadian preference predicts sustained treatment outcomes in patients with unipolar depression and evening preference. J Clin Sleep Med. 2022;18(2):523-531.

Guiding principles for determining work shift duration and addressing the effects of work shift duration on performance, safety, and health: guidance from the American Academy of Sleep Medicine and the Sleep Research Society

CITATION

Risks associated with fatigue that accumulates during work shifts have historically been managed through working time arrangements that specify fixed maximum durations of work shifts and minimum durations of time off. By themselves, such arrangements are not sufficient to curb risks to performance, safety, and health caused by misalignment between work schedules and the biological regulation of waking alertness and sleep. Science-based approaches for determining shift duration and mitigating associated risks, while addressing operational needs, require: (1) a recognition of the factors contributing to fatigue and fatigue-related risks; (2) an understanding of evidence-based countermeasures that may reduce fatigue and/or fatigue-related risks; and (3) an informed approach to selecting workplace-specific strategies for managing work hours. We propose a series of guiding principles to assist stakeholders with designing a shift duration decision-making process that effectively balances the need to meet operational demands with the need to manage fatigue-related risks.

The association between chronotype and sleep quality, and cardiometabolic markers in patients with schizophrenia

Current data on chronotype and sleep quality and their relationship with clinical characteristics of schizophrenia are insufficient to evaluate whether these variables are associated with cardiometabolic risk. We aimed to identify the interplay between chronotype, sleep quality and metabolic indices that can potentially predict negative cardiometabolic outcomes in schizophrenia patients. One-hundred schizophrenia patients who were under a stable antipsychotic regime were enrolled in the study. Clinical information, anthropometric measurements, as well as recent metabolic parameters including serum lipids, atherogenic, and metabolic indices suggestive of cardiometabolic risk were recorded. High and low sleep quality groups (HSQ and LSQ) were determined via the Pittsburgh Sleep Quality Index and chronotypes were evaluated with the Morningness-Eveningness Questionaire. Patients with eveningness chronotype had poorer sleep quality compared to intermediate or morningness (p = .017) patients. The LSQ group had higher total cholesterol (p = .004) and low-density lipoprotein (LDL) (p = .041) compared to the HSQ group. Mean blood pressure was higher in the eveningness chronotype patients compared to intermediate or morningness patients (p = .015). According to a logistic regression model, total cholesterol, disposition index, and having an eveningness chronotype significantly predicted LSQ in schizophrenia. Eveningness chronotype may lead to impaired cardiometabolic regulation with the mediation of poor sleep quality in schizophrenia patients. Cardiovascular diseases, sleep quality, and sleep patterns can influence each other; thus, this complex relationship in schizophrenia should be considered while configuring both pharmacological and behavioral interventions.

Guiding principles for determining work shift duration and addressing the effects of work shift duration on performance, safety, and health: guidance from the American Academy of Sleep Medicine and the Sleep Research Society

Risks associated with fatigue that accumulates during work shifts have historically been managed through working time arrangements that specify fixed maximum durations of work shifts and minimum durations of time off. By themselves, such arrangements are not sufficient to curb risks to performance, safety, and health caused by misalignment between work schedules and the biological regulation of waking alertness and sleep. Science-based approaches for determining shift duration and mitigating associated risks, while addressing operational needs, require: (1) a recognition of the factors contributing to fatigue and fatigue-related risks; (2) an understanding of evidence-based countermeasures that may reduce fatigue and/or fatigue-related risks; and (3) an informed approach to selecting workplace-specific strategies for managing work hours. We propose a series of guiding principles to assist stakeholders with designing a shift duration decision-making process that effectively balances the need to meet operational demands with the need to manage fatigue-related risks.

Chronotype, general health and quality of sleep in a population of Spanish nurses

OBJECTIVE

The aim of this study was to investigate the association between chronotype, general health status and sleep quality in a sample of Spanish nurses.

METHOD

An observational study assessing morningness-eveningness predisposition, general health status and quality of sleep was conducted between January and April 2018. Univariate and multivariate analyses were performed. A linear regression model was carried out to determine the influence of the variables on the morningness-eveningness type.

RESULTS

Morning-type was associated with aging (β = 0.249, p = 0.005), being married (β = 3.970, p = 0.033), and with a self-assessed low daily sleepiness (β = -0.311, p = 0.152). Good quality of sleep was moderately correlated with high values of general health (r = 0.337) and perceived quality of life (r = 0.426).

CONCLUSION

Anomalies of the circadian rhythm together with the features of shift workers may play an important role in predicting self-assessed general health status or the quality of sleep in nurses.

Sleep quality in students: Associations with psychological and lifestyle factors

Disturbed sleep is prevalent in adult populations and has been associated with negative health outcomes. This cross-sectional study assessed how psychological and lifestyle factors relate to subjective sleep quality in university students. In a large (N = 1114) sample of Dutch university students we assessed chronotype (Morningness-Eveningness Questionnaire), depressive symptoms (Quick Inventory of Depressive Symptoms), cognitive emotion regulation styles (Cognitive Emotion Regulation Questionnaire), and substance use (caffeine, alcohol, smoking, cannabis), and analysed whether these factors were related to subjective sleep quality (Pittsburgh Sleep Quality Index). The sample was predominantly (77.8%) female, mean age 21.1 (SD = 2.9) years, and 42.8% had clinically significant poor subjective sleep quality. More eveningness (B = −.05, p = .001), more depressive symptoms (B = .31, p = .001), less use of the emotion regulation strategy ‘putting into perspective’ (B = −.06, p = .02) and smoking (B = .53, p = .02) were independently associated with poorer subjective sleep quality. More eveningness, more depressive symptoms, less use of the emotion regulation style ‘putting into perspective’ and smoking were independently associated with poorer subjective sleep quality in a large sample of Dutch university students.

Cortisol, chronotype, and coping styles as determinants of tolerance of nursing staff to rotating shift work

Hypothalamo-pituitary-adrenal axis activity and cortisol patterns are likely to play a role in shift work tolerance, i.e., ability to adapt to shift work without suffering stress-related consequences. Yet, the evidence is scanty. Here, salivary cortisol output during night shifts and leisure days was assessed in fast-forward rotating shift work nursing staff (N = 30), and possible links with a series of variables - gender (30% male), age (M = 39.6, SEM = 1.57 y), years of service (M = 12.43, SEM = 1.48 y), BMI (M = 23.29, SEM = 0.66 Kg/m²), self-rated chronotype, sleep quality, and psycho-behavioral factors - were investigated. Main results show that cortisol output during night shifts: i) is larger in morning-oriented chronotypes, thus affected by the circadian misalignment between biological and working rhythms; ii) associates with dysfunctional coping styles at work; iii) positively correlates with diurnal cortisol secretion on leisure days, i.e., individuals with larger cortisol output during shifts display higher cortisol secretion on non-working days. Chronotype and psycho-behavioral factors explain most of the correlational weight linking cortisol output during the night shift and off-days. In conclusion, we confirm salivary cortisol testing as a suitable objective marker of occupational stress and propose it as a valuable index for monitoring shift work tolerance, in combination with chronotype. Moreover, we emphasize the importance of evaluating psycho-behavioral factors in professional settings, because these modifiable variables can be addressed with tailored psychological interventions to ameliorate poor job satisfaction, reduce work-related distress, and avoid chronic cortisol excess experienced by shift workers.

Does visual search mediate the effect of chronotype on driving behaviour: Evidence from simulated driving

Chronotype refers to individual differences in the timing of circadian sleep-wake cycles and subjective alertness throughout the day. It is a potential factor influencing people's driving behaviour, but no research has explored the mechanisms underlying this topic. The current study aimed to explore the relationship between morningness-eveningness preferences and driving behaviour and the mediating effect of visual search between them. Thirty-eight drivers were selected to participate in this study based on their chronotype. They were divided into morning-type and evening-type groups by their score on the reduced Morningness-Eveningness Questionnaire (rMEQ). Both groups completed a visual search task and a simulated driving task in a morning session and an evening session. The results showed that morningness-eveningness preferences had synchronous effects on basic driving performance; specifically, morning-type drivers showed better driving behaviour in the morning than in the evening, and evening-type drivers showed the opposite trend. Furthermore, visual search abilities showed a mediating effect between morningness-eveningness preference and driving performance. The mechanisms underlying these results are discussed. Related results and data could aid with schedule arrangements for professional drivers.

Effects of the COVID-19 lockdown on mental health, wellbeing, sleep, and alcohol use in a UK student sample

The COVID-19 pandemic and the consequent restrictions imposed by governments worldwide have had profound social and psychological effects, particularly for young adults. This study used longitudinal data to characterise effects on mental health and behaviour in a UK student sample, measuring sleep quality and diurnal preference, depression and anxiety symptoms, wellbeing and loneliness, and alcohol use. Self-report data was collected from 254 undergraduates (219 females) at a UK university at two-time points: autumn 2019 (baseline, pre-pandemic) and April/May 2020 (under 'lockdown' conditions).  Longitudinal analyses showed a significant rise in depression symptoms and a reduction in wellbeing at lockdown. Over a third of the sample could be classed as clinically depressed at lockdown compared to 15% at baseline. Sleep quality was not affected across the sample as a whole. The increase in depression symptoms was highly correlated with worsened sleep quality. A reduction in alcohol use, and a significant shift towards an 'evening' diurnal preference, were also observed. Levels of worry surrounding contracting COVID-19 were high. Results highlight the urgent need for strategies to support young people's mental health: alleviating worries around contracting COVID, and supporting good sleep quality, could benefit young adults' mental health as the COVID-19 crisis unfolds.

Chronotypes in elite Japanese athletes: assessed by the reduced Morningness-Eveningness and Munich ChronoType Questionnaires

This study aimed to test in elite athletes the correlation between the chronotype determined by the reduced version of the Morningness-Eveningness Questionnaire (rMEQ) and that determined by the Munich ChronoType Questionnaire (MCTQ). In total, 351 elite athletes filled out the rMEQ questionnaire, 59 athletes filled out the MCTQ questionnaire, and 39 athletes filled out both questionnaires. The rMEQ score and the corrected midpoint of sleep from the MCTQ correlated weakly (|r| = 0.360, p < .05); however, some cases were mismatched. The MSFsc also weakly correlated with age (|r| = 0.374, p < .05), while rMEQ did not. Our results may suggest that the choice of questionnaire to determine chronotype should depend on the purpose and the type of sport athlete.

The rhythm of affect, autonomy, competence and relatedness: A pilot diary study

The aim of this study was to explore the circadian rhythm of affect, autonomy, competence, and relatedness in the at-home sleep environmental setting. Participants completed electronic questionnaires at 06:30 h, 16:00 h and 21:00 h for seven days. Ninety-six respondents participated. Among these, 70 were students (73.7%; of which 65.7% were 18-25 years of age, the remainder being 26 years old or more) and 25 nonstudents (26.3%; all 26 years old or more), with one person neglecting to report such status. A total of 24 (25.0%) respondents had full-time jobs during the data collection, 51 (53.1%) had a part-time job, and 21 (21.9%) did not have a job. There was significant difference between times of day for positive affect, autonomy frustration, and competence frustration. This included an increase in positive affect from morning to afternoon, and reduction in autonomy frustration and competence frustration from afternoon to evening. Chronotype was not related to the daily variations in the studies psychological variables. We conclude that although there are some intra-daily variations in some of the basic needs, these are not as strong as those seen for positive affect, in terms of consistency across several days.

Effects of diurnal changes on temporal processing in morning-type and evening-type individuals with normal hearing

OBJECTIVE

The present study aims at determining the influence of diurnal changes in duration discrimination and temporal resolution in the morning- and evening-type individuals with normal hearing sensitivity.

METHOD

Sixty individuals with normal hearing were divided into morning, evening and intermediate types using the Morningness-Eveningness Questionnaire. Tests for Duration discrimination, Gap detection, and Temporal modulation transfer function were carried out in all the participants during morning and evening. The performance of subjects of all the three groups during both morning and evening was analyzed.

RESULTS

Results revealed a diurnal effect on morning and evening type individuals' performance where morning type exhibited better performance when tested during morning and evening individuals when tested during the evening. At the same time, there were no significant diurnal effects seen in the intermediate type.

CONCLUSIONS

The poor cognitive performance and lack of inhibitory control at the time of the off-peak hours possibly result in the poor scores. Furthermore, the diurnal effects on objective audiological tests in morning and evening type individuals should be studied. The influence of diurnal changes could be considered an extraneous variable in future research on psychoacoustic tests in younger adults.

Chronotype patterns associated with job satisfaction of shift working healthcare providers

Job satisfaction of healthcare providers is important for their own health and also the quality of care provided to their patients. The aim of our study was to measure the chronotype patterns among healthcare providers and its association with their job satisfaction. Using stratified cluster random sampling, we recruited 210 healthcare providers working permanent morning or evening shifts for a cross-sectional study in Sari, Iran. By in-person interview, we collected data on demographic characteristics and assessed both chronotype, using the Horne-Östberg M-E Questionnaire, and job satisfaction, using the Danet's Job Satisfaction Questionnaire. We grouped job satisfaction scores into four ordinal categories and assessed correlations with study variables by ordinal multivariate logistic regression. The average age of the participants was 39.0 (SD 8.02) years. Most were younger than 45 years of age (74.27%), female (66.67%), married (62.24%), of high income (45.71%), and employed in permanent full-time healthcare work (56.67%). Overall, 63.4% of the participants had moderately high to high job satisfaction. Those who worked the morning shift who were moderate morning and high morning chronotypes, compared to those who were intermediate chronotype, had a statistically significant adjusted odd ratio (AOR), respectively, of 11.36 and 6.53 of higher job satisfaction. Likewise, those who worked the evening shift and were moderate evening and high evening chronotype, compared to intermediate chronotype, had a statistically higher AOR of job satisfaction, respectively, 3.44 and 32.63. We found the match between chronotype and work shift schedule to be linked with increased job satisfaction. If the findings are verified in other investigations, the relatively easy measure of chronotype should be considered to assign people to a work shift to improve job satisfaction of healthcare and perhaps other workers.

Sleep quality and athletic performance according to chronotype

BACKGROUND

When studying the quality of sleep in relation to athletic performance, the athlete's chronotype and habitual time consider important factors. We aim to investigate the sleep quality and athletes' performance according to chronotype in elite athletes.

METHODS

Three hundred forty elite athletes (males = 261, females = 79) were recruited for the present study. All participants were screening for chronotype by the Korean versions of the Morningness - Eveningness Questionnaire (MEQ-K). The Pittsburgh Sleep Quality Index (PSQI) and Wingate Anaerobic Test (WAnT) were measurement after screening.

RESULTS

PSQI global score, PSQI sleep quality, PSQI sleep onset latency, PSQI sleep disturbance, and PSQI daytime dysfunction were significant differences among the groups. WAnT mean power (W), mean power (W/kg), peak power (W), and peak power (W/kg) were significant differences among the groups. A negative correlation coefficient was found between PSQI score and WAnT mean power (W) (r = - 0.256, p < 0.01), mean power (W/kg) (r = - 0.270, p < 0.01), peak power (W) (r = - 0.220, p < 0.01), and peak power (W/kg) (r = - 0.248, p < 0.01).

CONCLUSIONS

This study indicates that related poor sleep quality and late-type chronotype may reduce the athletes' performance in elite athletes. In addition, the sleep quality is much higher in the early-type chronotype than in the late-type chronotype. Moreover, it also the athletic performance was better in the early-type chronotype than in the late-type chronotype.

Relationships between morningness, Big Five personality traits, and problematic Internet use in young adult university students: mediating role of depression

The aim of this study was twofold. Firstly, it explored the relationships between morningness, Big Five personality traits, depression, and problematic Internet use (PIU). Secondly, it examined the possible mediating role of depression in these relationships. The following measures were used: the Internet Addiction Test, the Composite Scale of Morningness, the International Personality Item Pool-Big Five Markers-20, and the Center for Epidemiologic Studies Depression Scale. The participants in the study were 398 university students 18 to 30 (M = 20.37, SD = 2.29) years of age. The study found that PIU Total, PIU Mental Disorder, and PIU Time Management Disorder are positively related to depression and negatively related to morningness, Extraversion, Agreeableness, Conscientiousness, Emotional Stability, and Openness. PIU was more often found in individuals with an evening chronotype. The study confirmed the role of depression as a mediator in the relationship of personality traits and morningness to PIU Mental Disorder and PIU Time Management Disorder. For PIU Mental Disorder, the study revealed a full mediation effect of depression in the case of morningness, Emotional Stability, and Extraversion, and partial mediation in the case of Agreeableness and Intellect. For PIU Time Management Disorder, there was a full mediation effect of depression in the case of Emotional Stability, Extraversion, and Agreeableness, and partial mediation in the case of morningness and Intellect. The results highlight the importance of including depression when investigating the relationship between morningness and personality in studies of PIU.

Morningness in German and Spanish students: a comparative study

Humans show pronounced individual differences in circadian orientation. Transcultural comparisons are interesting since biological (or environmental) factors together with cultural ones may contribute to differences in morningness–eveningness. We compared Spanish and German undergraduates using the Composite Scale of Morningness (CSM) to assess circadian preferences. Confirmatory and multiple groups confirmatory factor analysis were used to assess factor structure and structural invariance across countries. The results showed that a three‐factor model of morningness best characterises the CSM structure of both samples. Partial factorial invariance (factor loadings) across countries was demonstrated for the factors ‘morningness’ and ‘morning alertness’. Scores of both factors were higher in German students. Potential cultural and biological explanations for the differences are discussed. Copyright © 2007 John Wiley & Sons, Ltd.

Morningness–eveningness as a dimension of personality: Trait, state, and psychophysiological correlates

Personality, mood, and psychophysiological correlates of Home and östberg's (1976) Morningness‐Eveningness Questionnaire (MEQ) are reported. State data were collected at both morning and evening times of day. MEQ score was related to personality traits associated with psychopathology—trait anxiety in males and psychoticism in females. The best explanation of these correlations is that personality and subject sex affect attention to zeitgebers or time of day cues. MEQ score was related to extroversion only in female subjects. A between‐subjects study showed that morningness was positively associated with high energetic arousal in the morning, as predicted, but the MEQ did not predict physiological arousal measures reliably. A subsequent within‐subjects study demonstrated sex differences in interactive effects of time of day and morningness‐eveningness in mood states related to psychological disorder. The MEQ predicted two somewhat independent circadian rhythms—one related to arousal, and one to depression. It is concluded that personality may be linked to morningness‐eveningness through associations between personality traits and cognitive and social factors affecting the entrainment of circadian rhythms to the sleep‐wake cycle.

Diurnal variation, morningness‐eveningness, and momentary affect

The research questions of this study are the following: To what degree can results such as those of Thayer and colleagues (1978a, 1985, 1986, 1988) concerning diurnal variation and differences between diurnal types, obtained for energetic and tense arousal, be (1) replicated, (2) extended to elation and pleasantness, and (3) generalized to positive and negative affect? With regard to energetic arousal, all results were in line with those of Thayer and colleagues. However, regarding tense arousal, there was an unexpected main effect for time of day. For energetic arousal, elation, pleasantness, positive affect, and negative affect, there was (a) a significant main eflect for time of day, (b) a quadratic trend for diurnal variation, and (c) a significant Diurnal Type × Time of Day interaction, There were no significant sex differences in diurnal variation. Two final hypothetical statements are made about the diurnal variation and differences between diurnal types with regard to state scales: (a) the diurnal variation of a state scale cannot be described with a quadratic function if that scale is completely unrelated to energetic arousal; and (b) the characteristic differences between morning types and evening types, especially when measured in the morning and in the evening, will not manifest themselves on a state scale if that scale is entirely unrelated to energetic arousal. Finally, the possible usefulness of the results of this study for practical applications and the development of theories are discussed.

Circadian preferences and personality traits: A meta‐analysis

In this study we report results of a meta‐analysis of studies linking personality to circadian rhythms. A total of 35 independent samples, 96 correlations and 8589 participants were included. Results showed that conscientiousness is the personality dimension that mostly related to morningness (r = .29). Agreeableness was also related to morningness although to a lesser degree (r = .13). Openness to experience, extraversion and neuroticism, contribute to a very small degree (i.e. −.09, −.06 and −.07, respectively). Furthermore, moderation analyses suggested effects of personality measure (big five vs. other) and sample (students vs. workers). Average age of participants had no significant impact on the relationship between morningness and personality, apart from a very trivial influence on openness to experience. Copyright © 2010 John Wiley & Sons, Ltd.

Associations between diurnal preference, impulsivity and substance use in a young-adult student sample

A diurnal preference for eveningness is common in young adulthood and previous research has associated eveningness with anxiety symptoms as well as increased smoking and alcohol use behaviors. There is some evidence that impulsivity might be an important explanatory variable in these associations, but this has not been comprehensively researched. Here we used both subjective and objective measures of impulsivity to characterize impulsive tendencies in young adults and investigated whether trait impulsivity or trait anxiety could mediate the link between eveningness and substance use. A total of 191 university students (169 females), age range 18-25 y, completed the study. Diurnal preference, sleep quality, anxiety, impulsivity, and substance use were assessed by questionnaire. Impulsivity was also measured using a delay discounting task. Eveningness correlated with trait anxiety and trait impulsivity, and these associations were still significant after controlling for sleep quality. On the delayed discounting task, eveningness correlated with a tendency to prefer smaller immediate rewards over delayed, larger ones. Evening types also reported higher levels of alcohol and cigarette use even after controlling for sleep quality. These associations were found to be completely mediated by self-reported impulsivity; anxiety did not contribute. The current results could help inform interventions aiming to reduce substance use in young adult populations.