Comparing patients treated with CBT for insomnia with healthy sleepers and sleepers with past insomnia on dimensions of sleep health

OBJECTIVES

To compare patients treated with cognitive behavioral therapy for insomnia (CBT-I) with healthy sleepers and individuals with past but not current insomnia on multidimensional sleep health.

METHODS

The study evaluates CBT-I on six dimensions of sleep health (regularity, satisfaction, alertness, timing, efficiency, duration) in a sample of individuals with insomnia compared to two other unique sleep samples. Participants were in one of three groups: insomnia (CUR, n = 299), healthy sleeper (HS, n = 122), or past insomnia (PAST, n = 35). Daily diaries and validated measures were employed to capture six dimensions of sleep health. The CUR group received four 60-minute sessions of CBT-I every 2weeks, and sleep health indices were measured at baseline and post-treatment. The HS and PAST groups were measured only at baseline.

RESULTS

Results of the pairwise t tests indicated improvements in sleep satisfaction, alertness (fatigue but not sleepiness), timing, efficiency, and duration (Cohen's d=0.22 to 1.55). ANCOVA models revealed significant differences in sleep health scores between treated insomnia patients and the other two sleep groups. Treated patients demonstrated less bedtime and risetime variability, in addition to lower napping duration. Overall, the study observed significant changes in various domains of sleep health after four sessions of cognitive behavioral therapy for insomnia; however, differences remain when compared to the other groups in the study.

CONCLUSION

There may be ongoing sleep vulnerability in patients treated with cognitive behavioral therapy for insomnia though future inclusion of a control group would increase internal validity. Borrowing from transdiagnostic sleep modules may be helpful to support remaining deficits after cognitive behavioral therapy for insomnia.

The influence of night shift work and associated factors on serum uric acid in aircraft maintenance workers

BACKGROUND AND OBJECTIVE

The prevalence of 12-hour shift work is increasing in various occupations. Shift work has been linked to circadian rhythm disruption, which may lead to hormonal changes and metabolic disorders, including alterations in glucose, lipid, and purine metabolism. Despite this, there is limited research on the potential connection between work shifts and abnormal serum uric acid (SUA) levels. Furthermore, the factors that contribute to abnormal SUA levels in shift workers are not well-understood. Therefore, this study aimed to analyze the SUA levels of shift workers employed in an aircraft maintenance company, investigate the potential association between shift work and SUA levels, and explore the factors that may influence abnormal SUA levels in shift workers.

METHODS

A total of 2263 male workers from an aircraft maintenance company were included in this study using the cluster sampling method. The workers were divided into two groups based on their working shifts: night shift (N = 1047, 46.27%) and day working (N = 1216, 53.73%). A survey was conducted between April 1st and June 30th, 2022 to gather information on work, lifestyle, physical examination results, and other relevant factors. The survey included a self-designed demographic information questionnaire to collect data on workers' characteristics, medical history, years of employment, smoking and drinking habits, and main lifestyle behaviors. The workers' SUA levels were measured using uricase colorimetry. One-way ANOVA was used to compare the difference in the abnormal detection rate of SUA between the two groups, and multi-factor logistic regression analysis was used to identify the factors that influence abnormal SUA levels.

RESULTS

The study indicated that 48.9% of night shift workers and 43.8% in the regular day workers had abnormal SUA levels, with a significant difference between the two groups (χ2 = 6.125, P = 0.013). Factors such as circadian rhythm type, shift work, age, the taste of diet, type of diet, smoking, overweight or obesity based on body mass index (BMI), concentration of urine creatinine (CREA), total cholesterol, triglyceride, and low-density lipoprotein cholesterol were found to be correlated with SUA abnormalities (P < 0.05). The risk of developing SUA abnormalities was found to be higher in individuals with an intermittent (OR = 1.34, 95% CI: 0.83-2.12, P < 0.05) or evening circadian rhythm type (OR = 1.45, 95% CI: 0.86-2.43, P > 0.05) compared to those with a morning type. Additionally, factors such as night shift work, a high-sodium diet, smoking, a diet high in meat and low in vegetables, being overweight or obese, and higher levels of CREA were also found to increase the risk of developing SUA abnormalities. The study also revealed a significant dose-response relationship between BMI and abnormal uric acid levels. After controlling for other factors, the risk of developing SUA abnormalities was found to be 1.18 times higher in the night shift work group than in the day work group (OR = 1.18, 95% CI:1.02-1.34, P = 0.01).

CONCLUSION

Shift work has been linked to a higher risk of developing SUA abnormalities, and there are several factors that may contribute to this risk. To prevent diseases, it is recommended that enterprises implement better health monitoring and management practices for shift workers.

A more accurate assessment of circadian typology is achieved by asking persons to indicate their preferred times rather than comparing themselves with most people

The aim of the present work was to compare two circadian questionnaires: the Preference Scale (PS) and the reduced version of the Morningness-Eveningness Questionnaire (rMEQ). A sample of 849 (35.10% men) university students, 421 of whom were Spanish (27.55% men; mean age 21.07 + 2.31) and 428 Italian (42.52% men; mean age 23.26 + 3.01), were administered both questionnaires. Gender (higher morningness in women) and nationality (higher eveningness in Spaniards) differences were replicated with rMEQ but not with PS, in which an inverse association between nationality and circadian preference was observed (i.e. higher morningness in Spaniards). Taking into account that the formulation of the rMEQ items, with its specific times, makes the answers less influenced by socio-cultural bias, we conclude that rMEQ is preferable to PS when evaluating circadian preference in young adults.

Protocol of the Budapest sleep, experiences, and traits study: An accessible resource for understanding associations between daily experiences, individual differences, and objectively measured sleep

Sleep is both a neurophysiological state and a biologically necessary behavior that performs a variety of indispensable roles for human health, development, and cognitive functioning. Despite this, comparatively little is known about the relationships between daily experiences and sleep features. Importantly, these relationships are bidirectional in nature, may be differently associated with subjectively and objectively assessed sleep, and may also be modulated by individual differences To address this challenge, we created the Budapest Sleep, Experiences, and Traits Study (BSETS), a multidisciplinary observational sleep study utilizing novel remote EEG devices. BSETS was designed to establish a dataset for future use in investigating the relationships between sleep features and daily experiences. In this paper we describe the protocol of the currently ongoing BSETS, which examines a community-dwelling sample of over 250 healthy participants who are studied in a naturalistic setting using a large questionnaire assessing psychological, demographic, and anthropometric information, as well as evening/morning diaries of sleep and daily experiences, and mobile EEG recordings over a period of 7 days. This dataset will become an accessible resource to the wider scientific community and can be utilized to investigate the complex multidirectional relationships between objectively and subjectively measured sleep, daily experiences, and individual differences, bestowing it with significant value for sleep researchers as well as practitioners working in clinical settings with patients suffering from disordered sleep.

Daily rhythms, light exposure and social jetlag correlate with demographic characteristics and health in a nationally representative survey

The timing of daily activity in humans have been associated with various demographic and health-related factors, but the possibly complex patterns of confounding and interaction between these has not been systematically explored. We use data from Hungarostudy 2021, a nationally representative survey of 7000 Hungarian adults to assess the relationship between self-reported chronotype, social jetlag (using the Munich Chronotype Questionnaire), demographic variables and self-reported health and demographic variables, including ethnic minority membership. Supporting the validity of self-reports, participants with later chronotypes reported the lowest daytime sleepiness at a later clock time. We found that older age, female sex, a more eastward and southward geographical position, residence in a smaller settlement, less education and income, religiousness and cohabiting with small children were associated with an earlier chronotype. Younger age, higher education and income, and cohabiting with small children were associated with increased social jetlag. Of the 48 health-related variables surveyed, the relationship with both chronotype and social jetlag were mostly accounted for by age, sex, and socioeconomic effects, but we identified alcohol consumption, smoking, and physical activity as predictors of both social jetlag and chronotype, while a number of disorders were either positively or negatively associated with chronotype and social jetlag. Our findings from a large, nationally representative sample indicate that both biological and social factors influence chronotype and identified both demographic and health-related variables as risk factors for social jetlag. Our results, however, do not support a causal relationship between light exposure and mental health.

Consistency of chronotype measurements is affected by sleep quality, gender, longitude, and latitude

Chronotype has received increasing research attention. However, there remains some confusion about the influence of gender, age, sleep quality, insomnia severity, longitude, and latitude on the consistency of the chronotype measured by the different tools. Chronotype measurement indicators were collected from 421 participants. The midpoint of sleep for actigraphy (MSF_A), sleep diary (MSF_D), and Munich Chronotype Questionnaire (MCTQ) (MSFsc) on free days and the Morningness-Eveningness Questionnaire (rMEQ) scores were used to measure the chronotype. In addition, demographic information, Pittsburgh Sleep Quality Index (PSQI), and Insomnia Severity Index (ISI) were also collected. A significant correlation was identified between the questionnaires (MSF_D, MSFsc, rMEQ) and actigraphy (MSF_A) as measures of chronotype. MSF_A was associated with sleep latency and sleep disturbance in the PSQI subdimensions. The correlation between MS_D and sleep disturbance was significant. Both rMEQ and MSFsc were significantly correlated with PSQI (total scores and daytime dysfunction) and ISI. The consistency of all chronotype measurements for the questionnaires and actigraphy was influenced by gender. Among them, MSF_D is also affected by age, while only the latitude and sleep disturbance effect was found in the MSFsc. The influence of age, gender, sleep quality, and latitude should be emphasized when measuring the chronotype using self-reported methods.

Change in Seasonal Beliefs Mediates the Durability Advantage of Cognitive-Behavioral Therapy Over Light Therapy for Winter Depression

In treating an acute episode of winter depression, cognitive-behavioral therapy for seasonal affective disorder (CBT-SAD) and light therapy are comparably efficacious, with improvement in depression symptoms during CBT-SAD mediated by reduced seasonal beliefs (i.e., maladaptive thoughts about the seasons, light availability, and weather). Here, we tested whether the enduring benefit of CBT-SAD over light therapy following treatment is associated with offsetting seasonal beliefs during CBT-SAD. Currently depressed adults with Major Depression, Recurrent with Seasonal Pattern (N = 177) were randomized to 6 weeks of light therapy or group CBT-SAD and followedup one and two winters after treatment. Outcomes measured during treatment and at each follow-up included depression symptoms on the Structured Clinical Interview for the Hamilton Rating Scale for Depression-SAD Version and Beck Depression Inventory-Second Edition. Candidate mediators measured at pre-, mid-, and posttreatment were SAD-specific negative cognitions (Seasonal Beliefs Questionnaire; SBQ); general depressogenic cognitions (Dysfunctional Attitudes Scale; DAS); brooding rumination (Ruminative Response Scale-Brooding subscale; RRS-B); and chronotype (Morningness-Eveningness Questionnaire; MEQ). Latent growth curve mediation models found a significant positive path from treatment group to the slope of SBQ during treatment, with CBT-SAD showing larger improvements in seasonal beliefs with overall change in seasonal beliefs in the medium-effect range, and significant positive paths from SBQ slope to depression scores at the first and second winter follow-ups, indicating greater change towards more flexible seasonal beliefs during active treatment was associated with less severe depression symptoms following treatment. Estimated indirect effects (treatment group → SBQ change * SBQ change → outcome) were also significant at each follow-up for each outcome with βindirect ranging from .091 to .162. Models also found significant positive paths from treatment group to the slope of MEQ and RRS-B during treatment, with light therapy showing a greater increase in "morningness" and CBT-SAD showing a greater decrease in brooding during active treatment; however, neither construct emerged as a mediator of follow-up depression scores. Change in seasonal beliefs during treatment mediates both the acute antidepressant and long-term effects of CBT-SAD and explains lower depression severity following CBT-SAD relative to light therapy.

The Effect of Symptom-Provocation on Inhibitory Control in Obsessive-Compulsive Disorder Patients Is Contingent upon Chronotype and Time of Day

Studies have shown that alertness can affect inhibitory control, the mechanism responsible for stopping behaviors, thoughts, or emotions. Inhibitory control is particularly important for helping individuals with Obsessive-Compulsive Disorder (OCD) resisting their symptoms. Chronotype is the mechanism governing an individual's fluctuation of alertness throughout the day. Previous studies have shown that individuals with a 'morning' chronotype have worse OCD symptoms in the evening and vice versa. We administered a novel 'symptom-provocation stop signal task' (SP-SST), in which individually tailored OCD triggers were presented and inhibitory control was measured. Twenty-five treatment-seeking OCD patients completed the SP-SST three times per day for seven consecutive days. Stop signal reaction time (SSRT), which measures inhibitory control, was calculated separately for symptom-provocation trials and for neutral trials. Results yielded that: (a) stopping was significantly harder in the symptom-provocation compared to neutral trials, and (b) the chronotype by time-of-day interaction predicts inhibition for both symptom-provocation and neutral trials, indicating better inhibition in the optimal time of day. Furthermore, we concluded that individually tailored OCD triggers have a detrimental effect on inhibitory control. Most importantly, higher alertness levels, which can be predicted by the interaction of chronotype and time of day, affect inhibitory control, both in general and for OCD triggers specifically.

Morning affect or sleep inertia? Comparing the constructs and their measurement

The construct of Morning Affect (MA; alertness upon awakening/time required to feel fully awake) emerged from exploratory factor analysis of morningness-eveningness questionnaires, and while it has been equated with morningness-eveningness preference it has much conceptual overlap with sleep inertia (SI; the transitional state between sleep and being fully awake). The current study compared questionnaire measures of these constructs to help clarify their inter-relationships. A volunteer sample of 453 students at an English-medium university in China completed an online survey including the Sleep Inertia Questionnaire (SIQ), the Morningness-Eveningness-Stability-Scale-improved (MESSi), with subscales for MA, Eveningness, and Distinctness (amplitude of diurnal variation), and the reduced Morningness-Eveningness Questionnaire (rMEQ). Measures of depression, sleep quality, mindfulness, and personality were also included. Exploratory factor analysis of the SIQ, MESSi, and rMEQ items revealed seven factors: Cognitive, Emotional, and Physiological SI, Responses to SI (including one MA item), and Duration of SI (one SIQ item, 3/5 MA items, and one rMEQ item); Morningness-Eveningness (MESSi Eveningness items, plus 3/5 rMEQ items); Distinctness (3/5 MESSi items). These results suggest that Morning Affect may be better characterised as a general measure of sleep inertia, and may contribute to ongoing development/refinement of questionnaire measures of circadian functioning.

Implicit and Explicit Stigma of Chronotype in Emerging Adults

BACKGROUND

Individuals with poor sleep (e.g., insomnia) and mental health (e.g., depression) experience negative stigma but no studies have examined the relationship between stigma and evening chronotype. The present mixed methods study aimed to assess and describe explicit and implicit attitudes about evening and morning chronotypes in a sample of emerging adults.

PARTICIPANTS

49 undergraduates (M_age = 19.9 [SD = 1.5], 83.7% female).

METHODS

Participants completed self-reports of demographics and chronotype. Attitudes about "night owls" and "early birds" were measured with self-report questionnaires (explicit attitudes) and an Implicit Association Task (implicit attitudes). Participants described associations with evening and morning chronotypes in free-text responses, which were qualitatively coded.

RESULTS

We found evidence of implicit bias against night owls and for early birds. The positive mean implicit d score was 0.57 (SD = 0.47), indicating a moderate implicit bias for pairing "bad" with "night owl" and "good" with "early bird." No baseline characteristics, including chronotype, were significantly associated with implicit bias. Analyses of explicit bias revealed participants perceived night owls as significantly more lazy, unhealthy, undisciplined, immature, creative, and young. Analysis of free-text responses provided further evidence of these associations.

CONCLUSIONS

Consistent with hypothesis, undergraduates demonstrated predominantly negative implicit and explicit stigma toward evening chronotypes compared to morning types. As stigma can lead to adverse consequences, future studies should assess the impact of negative societal and self-stigma on evening types. Consideration of societal stigma within clinical intervention contexts could have the potential to reduce shame or other emotions that interfere with sleep.

Digital cognitive behaviour therapy for insomnia (dCBT-I): Chronotype moderation on intervention outcomes

Using data from 1721 participants in a community-based randomized control trial of digital cognitive behavioural therapy for insomnia compared with patient education, we employed linear mixed modelling analyses to examine whether chronotype moderated the benefits of digital cognitive behavioural therapy for insomnia on self-reported levels of insomnia severity, fatigue and psychological distress. Baseline self-ratings on the reduced version of the Horne-Östberg Morningness-Eveningness Questionnaire were used to categorize the sample into three chronotypes: morning type (n = 345; 20%); intermediate type (n = 843; 49%); and evening type (n = 524; 30%). Insomnia Severity Index, Chalder Fatigue Questionnaire, and Hospital Anxiety and Depression Scale were assessed pre- and post-intervention (9 weeks). For individuals with self-reported morning or intermediate chronotypes, digital cognitive behavioural therapy for insomnia was superior to patient education on all ratings (Insomnia Severity Index, Chalder Fatigue Questionnaire, and Hospital Anxiety and Depression Scale) at follow-up (p-values ≤ 0.05). For individuals with self-reported evening chronotype, digital cognitive behavioural therapy for insomnia was superior to patient education for Insomnia Severity Index and Chalder Fatigue Questionnaire, but not on the Hospital Anxiety and Depression Scale (p = 0.139). There were significant differences in the treatment effects between the three chronotypes on the Insomnia Severity Index (p = 0.023) estimated difference between evening and morning type of -1.70, 95% confidence interval: -2.96 to -0.45, p = 0.008, and estimated difference between evening and intermediate type -1.53, 95% confidence interval: -3.04 to -0.03, p = 0.046. There were no significant differences in the treatment effects between the three chronotypes on the Chalder Fatigue Questionnaire (p = 0.488) or the Hospital Anxiety and Depression Scale (p = 0.536). We conclude that self-reported chronotype moderates the effects of digital cognitive behavioural therapy for insomnia on insomnia severity, but not on psychological distress or fatigue.

Circadian preference is associated with multiple domains of trait and state level impulsivity

Impulsivity is a multidimensional construct with well-documented risk for substance use problems at both the trait- and state levels. A circadian preference towards eveningness has been linked to trait-level, global impulsivity, but whether this association holds true across multiple dimensions of impulsivity and whether actual sleep timing shows parallel associations with impulsivity remain unclear. Here, we extend existing literature by investigating whether eveningness is associated with multiple facets of both trait- and state-level impulsivity. We also examined these associations utilizing daily measures of sleep timing and duration and explored whether they differed by sex and/or race. All participants were moderate-to-heavy social drinkers aged 21-35. Primary analyses included 78 participants (100% White male participants: Sample 1) with circadian preference data (Composite Scale of Morningness: CSM) and sleep timing (midsleep) and duration assessed via daily self-report over 10 days. Five facets of impulsivity were assessed via the UPPS-P, both at baseline (full scale; trait-level) and up to 6 times per day over 10 days (reduced scale; state-level). Linear regression and mixed-effects models were used to examine between- and within-person associations of impulsivity with measures of circadian preference, timing, and duration, accounting for covariates. Exploratory analyses combined Sample 1 with an additional more diverse sample (Sample 2), resulting in a total of 182 participants (29.1% self-identified as Black, 29.7% as female) with daily self-report sleep timing and duration only (no circadian preference). Primary between-person models found that eveningness was associated with multiple facets of impulsivity, at trait (lack of perseverance) and state levels (negative and positive urgency, lack of perseverance, and lack of premeditation), while average midsleep and duration were generally unrelated to impulsivity. Primary within-person models largely paralleled the between-person findings. Exploratory analyses in the larger combined Samples 1 and 2 (without circadian preference) found that later midsleep timing was associated with greater mean state-level impulsivity across multiple facets, associations that may differ by race and sex. In a sample of White male participants, circadian preference for eveningness was strongly associated with multiple facets of impulsivity, at both trait- and state-levels, which may contribute to risk for substance use. Preliminary findings suggest sex and race differences in sleep-impulsivity associations, but future research with objective sleep/circadian measures in larger, more diverse samples will be important to clarify implications for sleep-focused prevention and/or treatment of substance use.

Validity of chronotype questionnaires in adolescents: Correlations with actigraphy

There are only a few validated chronotype and morningness-eveningness questionnaires for adolescents. We evaluated three such questionnaires, namely Morningness-Eveningness Stability Scale improved; reduced Morningness-Eveningness Questionnaire for Children and Adolescents; and Composite Scale of Morningness in adolescents against actigraphy. Fifty-five healthy 13- to 16-year-old adolescents completed the Morningness-Eveningness Stability Scale improved, reduced Morningness-Eveningness Questionnaire for Children and Adolescents, Composite Scale of Morningness, and Pediatric Daytime Sleepiness Scale, and provided a 7-day actigraphy and sleep diary recording about their sleep-wake patterns. We examined the correlations between sleep-wake and activity parameters, and the questionnaires. The influence of age and sex on chronotype classification was studied using uni- and multivariate analyses. All three chronotype questionnaires showed good internal consistency and convergent validity. Spearman correlations reflected less daytime sleepiness, earlier sleep times, midpoints of sleep, and acrophase in morning-oriented participants. Evening-oriented participants had more sleepiness and later respective sleep-wake times. Chronotype classification differed significantly between questionnaires. The Composite Scale of Morningness classified more participants as morning types when compared with the reduced Morningness-Eveningness Questionnaire for Children and Adolescents (12 versus 7, respectively), and fewer adolescents as evening types (5 versus 9, respectively). Age and sex had no significant influence on questionnaire scores. The Morningness-Eveningness Stability Scale improved, reduced Morningness-Eveningness Questionnaire for Children and Adolescents, and Composite Scale of Morningness are valid instruments to determine circadian preference in adolescents; however, chronotype classification from the Composite Scale of Morningness and reduced Morningness-Eveningness Questionnaire for Children and Adolescents cannot be used interchangeably.

A systematic review and meta-analysis of sleep and circadian rhythms disturbances in individuals at high-risk of developing or with early onset of bipolar disorders

Sleep and circadian rhythms disturbances (SCRD) in young people at high risk or with early onset of bipolar disorders (BD) are poorly understood. We systematically searched for studies of self, observer or objective estimates of SCRD in asymptomatic or symptomatic offspring of parents with BD (OSBD), individuals with presentations meeting recognized BD-at-risk criteria (BAR) and youth with recent onset of full-threshold BD (FT-BD). Of 76 studies eligible for systematic review, 35 (46%) were included in random effects meta-analyses. Pooled analyses of self-ratings related to circadian rhythms demonstrated greater preference for eveningness and more dysregulation of social rhythms in BAR and FT-BD groups; analyses of actigraphy provided some support for these findings. Meta-analysis of prospective studies showed that pre-existing SCRD were associated with a 40% increased risk of onset of BD, but heterogeneity in assessments was a significant concern. Overall, we identified longer total sleep time (Hedges g: 0.34; 95% confidence intervals:.1,.57), especially in OSBD and FT-BD and meta-regression analysis indicated the effect sizes was moderated by the proportion of any sample manifesting psychopathology or receiving psychotropic medications. This evolving field of research would benefit from greater attention to circadian rhythm as well as sleep quality measures.

Validation of the Chinese version of the Munich Chronotype Questionnaire (MCTQHK) in Hong Kong Chinese youths

Chronotype, referred to as an individual's diurnal preference of timing for rest and activity, can be subjectively measured using the Munich Chronotype Questionnaire (MCTQ). However, the validity of MCTQ has yet to be tested in the youth population. In addition, it remains uncertain if MCTQ is a good measure of chronotype in individuals with insomnia. The current study aimed to validate the Chinese version of MCTQ (MCTQ^HK) in the youth population and to explore the utility of MCTQ^HK in individuals with insomnia. The original MCTQ was translated into Chinese language using the translation-back-translation method. Part one of this study included 988 youths who completed a battery of self-report questionnaires online consisting of the MCTQ^HK and the morningness-eveningness questionnaire (MEQ) for the measures of circadian preference, Insomnia Severity Index (ISI) to assess insomnia symptoms, and Patient Health Questionnaire (PHQ-9) to measure depressive symptoms. Test-retest reliability was examined in 442 participants at one-month follow-up. Of the overall sample, 69 participants were randomly drawn to complete the second part of the study, which included prospective 7-day actigraphy monitoring and a further subset (n = 40) additionally completed a laboratory-based assessment of dim-light melatonin onset (DLMO) as a circadian phase marker. A total of 659 participants with valid responses were finally included in the analyses of the data collected from part one of the study (female = 67.7%; mean age: 20.7 ± 2.02). Results showed that MCTQ parameters, namely the midpoint of sleep on free days (MSF), midpoint of sleep on workdays (MSW), and midpoint of sleep adjusted for sleep debt (MSFsc), were significantly correlated with MEQ score (r = -.514 to -.650, p < .01). Test-retest reliability for MCTQ^HK was good (intraclass correlation = 0.75 to 0.84). Later MSFsc was significantly associated with greater insomnia and depressive symptoms after controlling for age and sex. All MCTQ parameters showed significant correlations with actigraphy-based midpoint of sleep and circadian rhythm parameters, i.e., acrophase and L5 onset (r = .362 to .619, p < .01), as well as DLMO (r = .393 to .517, p < .05). The associations remained significant after controlling for age. MSFsc derived from MCTQ was significantly correlated with MEQ score in both the healthy sleepers and participants with insomnia (as defined by ISI > 14), r = -.600, p < .001 and r = -.543, p < .001, respectively. The present study demonstrated that MCTQ^HK is suitable for assessing chronotype with good reliability and validity in Chinese youths and supported the utility of MCTQ^HK in individuals with insomnia.

Human chronotype: Comparison of questionnaires and wrist-worn actigraphy

In this work, we investigated the accuracy of chronotype estimation from actigraphy while evaluating the required recording length and stability over time. Chronotypes have an important role in chronobiological and sleep research. In outpatient studies, chronotypes are typically evaluated by questionnaires. Alternatively, actigraphy provides potential means for measuring chronotype characteristics objectively, which opens many applications in chronobiology research. However, studies providing objective, critical evaluation of agreement between questionnaire-based and actigraphy-based chronotypes are lacking. We recorded 3-months of actigraphy and collected Morningness-Eveningness Questionnaire (MEQ), and Munich Chronotype Questionnaire (MCTQ) results from 122 women. Regression models were applied to evaluate the questionnaire-based chronotypes scores using selected actigraphy features. Changes in predictive strength were evaluated based on actigraphy recordings of different duration. The actigraphy was significantly associated with the questionnaire-based chronotype, and the best single-feature-based models explained 37% of the variability (R²) for MEQ (p < .001), 47% for mid-sleep time MCTQ-MSFsc (p < .001), and 19% for social jetlag MCTQ-SJLrel (p < .001). Concerning stability in time, the Mid-sleep and Acrophase features showed high levels of stability (test-retest R ~ 0.8), and actigraphy-based MSFsc_acti and SJLrel_acti showed high temporal variability (test-retest R ~ 0.45). Concerning required recording length, features estimated from recordings with 3-week and longer observation periods had sufficient predictive power on unseen data. Additionally, our data showed that the subjectively reported extremes of the MEQ, MCTQ-MSFsc, and MCTQ-SJLrel are commonly overestimated compared to objective activity peak and middle of sleep differences measured by actigraphy. Such difference may be associated with chronotype time-variation. As actigraphy is considered accurate in sleep-wake cycle detection, we conclude that actigraphy-based chronotyping is appropriate for large-scale studies, especially where higher temporal variability in chronotype is expected.

Waxing and waning: The roles of chronotype and time of day in predicting symptom fluctuations in obsessive-compulsive disorder using a daily-monitoring design

Obsessive-compulsive disorder (OCD) symptoms fluctuate throughout the day, but scientists are not sure what underlies these fluctuations. One factor which may explain how OCD symptoms wax and wane throughout the day is alertness. Increased alertness is associated with greater inhibitory control, a factor which plays a significant role in patients' ability to overcome their OCD symptoms. The current study examined the relationship between chronotype (morningness/eveningness preference, a measure of alertness) and within-day OCD symptom severity fluctuations. We hypothesized that increased alertness leads to better inhibitory abilities and, therefore, reduced OCD symptoms. OCD Symptoms were measured through 7-days of monitoring in which participants were asked to retrospectively rate their symptoms at several timepoints throughout the day. Chronotype was measured using the Morningness/Eveningness Questionnaire (MEQ). Consistent with our hypotheses, results revealed an interaction between chronotype and time of day, such that those with an eveningness preference tended to have worse symptoms in the morning, and vice versa. In addition, we also report novel findings regarding the effect of bedtime, sleep duration, and sleep quality on symptom severity the next day. Taken together, these findings suggest that alertness may modulate OCD symptom severity throughout the day such that individuals experience more severe symptoms during times of low alertness. The clinical and theoretical implications of these findings are discussed.

Circadian preference and sleep quality in healthy controls and psychiatric inpatients with major depressive disorder - An actigraphy study incorporating morning and evening mood assessments

Major depressive disorder (MDD) is frequently accompanied by sleep disturbance. Regarding diurnal preference (chronotype), sleep problems and low mood have been associated with evening orientation. Considering diurnal preference, we investigated subjective restorative value of sleep and actigraphy sleep parameters together with mood assessments twice a day, i.e. in the morning and evening, during weekdays and weekends in MDD psychiatric inpatients and healthy controls (HCs). The restorative value of sleep was higher during the weekend in HC, and bedtimes and risetimes were delayed during the weekend compared to weekdays in HC and MDD. Morning mood affected subjective sleep ratings in both groups, while association with symptom severity (BDI) in MDD remained insignificant. In HC, better evening mood was associated with later bedtimes. Regarding the chronotype in HC, evening orientation was associated with relatively low restorative value of sleep during weekdays, and morning orientation was associated with relatively higher actigraphy sleep efficiency during weekdays compared to weekend. In MDD, an association of evening orientation with later rise times could be observed, while no chronotype dependent effect emerged regarding the restorative value of sleep or sleep efficiency. Our results emphasize that research on sleep in MDD should incorporate weekdays as well as weekends, chronotype assessment, and measures of morning and evening mood, as these can be associated with ratings of the subjective restorative value of sleep (i.e. in our study, better morning mood was associated with higher restorative values), but also with behavioral sleep parameters (i.e. in our study, more positive evening mood was associated with later bedtimes). Potentially, the restorative value of sleep in MDD evening types can be improved by maintaining a regular sleep schedule, which needs to be investigated in an experimental design.

Daylight Saving Time preferences in Norway: Do individual chronotype and home address' latitude and longitude matter?

Daylight Saving Time is highly debated and associated with several health risks. Health experts recommend terminating adjusting the clock time, and to keep permanent standard (winter) time year around. The aims of the study were to investigate preferences for keeping or terminating this biannual adjustment of clock times and for permanent standard or summer time, in the general Norwegian population. Furthermore, we aimed to investigate whether such preferences depended on individual chronotype and home address' latitude/longitude. The online survey included 47,194 participants. Chronotype was measured with the Composite Scale of Morningness (morning types, intermediate types, evening types). Results showed that 78.2% preferred to terminate adjusting the clock time. Summer time year around was preferred by 61.5% whereas 29.1% preferred standard time year around, and 9.4% did not have any preference. Preferences for terminating adjustment of clock times and summer time year around were found in all chronotypes and regardless of living south (latitude 58-59°N), north (latitude 69-71°N), west (longitude 5-6°E) or east (longitude 19-31°E). However, a relatively larger proportion of evening chronotypes preferred to terminate adjusting the clock time compared to morning chronotypes, and relatively more people living north or east preferred termination than people living south or west, respectively. Permanent standard time was more strongly preferred by extreme morning types in comparison with the other chronotypes. In conclusion, nearly four out of five participants reported to prefer to terminate adjusting the clock time, in line with recommendations. However, in contrast to advice from health experts, permanent summer time was preferred by twice as many as permanent standard time. Both chronotype and home address' latitude and longitude mattered in regard to such preferences, but only to a small degree.

Circadian preference and intelligence - an updated meta-analysis

A large number of previous studies reported a link between circadian preference and psychometric intelligence with mixed results and various hypotheses about the source of this correlation. In this study, we aimed to update a previous meta-analysis about the correlation between circadian preference and intelligence. Our literature search identified a large number of new studies, resulting in an increase of over 100% in the number of studies and over 400% in the number of involved participants (total k = 30, total N = 11160) over the previous meta-analysis, sampling a much wider age range from children to adults in late middle age. Our meta-analysis revealed no significant link between morningness and intelligence (r = -0.008) when the entire sample was studied, and no evidence for publication bias. This overall effect, however, obscured the moderating effect of age. The morningness-intelligence correlation decreased with mean sample age (R² = 54%), ranging from a non-significant positive trend in children and adolescents to a significant negative correlation after young adulthood. Eveningness was positively correlated with intelligence (r = 0.056), but this finding is based on a more age-restricted sample and only reached significance with some model specifications. We hypothesize that the age-moderated correlation between circadian preference and intelligence reflects social effects, where more intelligent individuals are more able to adjust their daily schedules to their natural circadian rhythm.

A daily diary study of sleep chronotype among Mexican-origin adolescents and parents: Implications for adolescent behavioral health

The current study used daily assessments of sleep to examine stability and change in sleep chronotype in adolescents and their parents. The study assessed adolescent sleep chronotype according to age, gender, and parent chronotype, and evaluated its associations with emotional and behavioral problems in youth. Participants included of 417 Mexican American adolescents (Mage = 16.0 years, Range = 13.9-20.0) and 403 caregivers, who reported bed and wake times daily for 2 consecutive weeks at two time points spaced 1 year apart. In addition, adolescents completed established self-report questionnaires of emotional and behavioral problems. Chronotype was computed as the midsleep point from bed to wake time on free days, correcting for sleep debt accumulated across scheduled days. Multilevel modeling showed a curvilinear association between adolescent age and chronotype, with a peak eveningness observed between ages 16 to 17. Adolescent and parent chronotypes were contemporaneously correlated, but each was only moderately stable over the 1-year period. Later adolescent chronotype was contemporaneously associated with more substance use in all adolescents. Individual development and the family context shape sleep chronotype in adolescents and parents. Sleep chronotype is implicated in adolescent behavioral health.

Circadian typology and implications for adolescent sleep health. Results from a large, cross-sectional, school-based study

STUDY OBJECTIVES

To investigate circadian typology in a large, representative sample of Norwegian adolescents, and its implications for sleep health.

METHODS

The sample included 3920 1^st year high school students aged 16-17 years. Respondents completed a web-based survey, including the short version of the Horne-Ostberg Morningness-Eveningness Questionnaire (rMEQ), the Munich Chronotype Questionnaire (MCTQ) and items on sleep-related behaviors (eg electronic media usage in bed, consumption of caffeinated beverages), sleep beliefs and daytime sleepiness. Data were analyzed using one-way ANOVAs and Chi-squared tests.

RESULTS

In all, 7.8% were categorized as morning, 52.3% as intermediate and 39.9% as evening types, respectively. Evening types had later sleep timing, longer sleep latency, more social jetlag and shorter school day sleep duration than morning types, with intermediate types displaying a sleep pattern between these two extremes. None of the circadian types met the minimum recommended amount of sleep on school nights (ie 8+ hours), and only morning types had a mean sleep duration of 7+ hours (7:19 h, nearly 1 h more than evening types who slept 6:20 h, p < 0.001). Evening types reported more use of electronic media in bed, more consumption of caffeinated beverages and more daytime sleepiness than the other circadian types. They were also less satisfied with their school day sleep duration and perceived it more difficult to change their sleep pattern.

CONCLUSIONS

Results from this study suggest that eveningness represents a sleep health challenge for older adolescents.

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.

Composite Scale of Morningness: Psychometric properties, validity with Munich ChronoType Questionnaire and age/sex differences in Poland

The present study aimed at testing psychometric properties of the Composite Scale of Morningness (CSM) and validating it with mid sleep on free days (MSF) derived from the Munich ChronoType Questionnaire (MCTQ) in Poland, along with analyzing age and sex differences in the CSM and MSF. A sample of 952 Polish residents (62.6% females) aged between 13 and 46 was tested. Additionally, a sample of 33 university students were given MCTQ and filled in a sleep diary for 8 days. MSF derived from MCTQ was related to the one from sleep diary (r = .44). The study revealed good reliability of the CSM (α = .84) and its validity: greater morningness preference was associated with earlier MSF from MCTQ (r = –.52). CSM scores were distributed over its full range, with a mean of 34, and did not differ between sexes, although females were earlier than males by 23 minutes in MSF. Regarding age, eveningness estimated with both CSM and MSF was greatest in subjects aged 16–18 years, and a shift toward eveningness during puberty and a shift back toward morningness in older age was observed. The Polish version of the CSM consisted of two components of morningness. Cutoff scores were: for evening types (lower 10%) 24 or less, for morning types (upper 10%) 43 or more. The Polish CSM presents good psychometric properties, which are similar to those reported in other language versions, and also presents sex/age patterns similar to those found previously.

Psychometric properties of a Japanese version of Composite Scale of Morningness

This study aimed to assess the factor structure and validity of the Composite Scale of Morningness (CSM) in Japanese samples. A sample of 348 Japanese university students (196 men, 152 women) and 170 adults from the community (50 men, 120 women) completed a questionnaire including the CSM, the Diurnal Type Scale (DTS) and questions regarding sleeping and waking times. Four measurement models were compared, and a two-factor measurement model with Morningness/Time of day preference (α = 0.78) and Morning Affect/Alertness (α = 0.80) factors yielded the closest fit. Both Morningness/Time of day preference and Morning Affect/Alertness were positively correlated with DTS score. Morningness/Ttime of day preference was negatively correlated with the midpoint of sleep on weekdays and free days. The measurement model was invariant across the university and community groups. The community group, which was older, was characterized by greater morningness. The results provide evidence of the validity of the Japanese CSM, thus opening up the possibility of including Japanese samples in cross-cultural research on morningness.

Daytime midpoint as a digital biomarker for chronotype in bipolar disorder

BACKGROUND

Bipolar disorder (BD) is associated with later sleep and daily activity (evening rather than morning chronotype). Objective chronotype identification (e.g., based on actigraphs/smartphones) has potential utility, but to date, chronotype has mostly been assessed by questionnaires. Given the ubiquity of accelerometer-based devices (e.g. actigraphs/smartphones) worn/used during daytime and tendency to recharge rather than wear at night, we assessed chronotype using daytime (rather than sleep) interval midpoints.

METHODS

Sixty-one participants with BD type I (BD-I) or II (BD-II) and 61 healthy controls completed 25-50 days of continuous actigraphy. The Composite Scale of Morningness (CSM) was completed by a subset of this group. Daytime activity midpoint was calculated for each daytime interval, excluding naps. Evening chronotype was defined as having a daytime interval midpoint at or after 16:15:00 (4:15:00 PM).

RESULTS

BD versus controls had delayed daytime midpoint (mean ± standard deviation) (16:49:07 ± 01:26:19 versus 16:12:51 ± 01:02:14, p < 0.01), and greater midpoint variability (73.3 ± 33.9 min versus 58.1 ± 18.3 min, p < 0.01). Stratifying by gender and age, females and adolescents with BD had delayed and more variable daytime midpoints versus controls. Adults with BD had greater midpoint variability than controls. Within-person mean and standard deviations of daytime midpoints were highly correlated with sleep midpoints (r = 0.99, p < 0.01 and r = 0.86, p < 0.01, respectively). Daytime midpoint mean was also significantly correlated with the CSM (r = -0.56, p < 0.01).

LIMITATIONS

Small sample size; analyses not fully accounting for daytime napping.

CONCLUSIONS

Wrist actigraphy for determination of daytime midpoints is a potential tool to identify objective chronotype. Exploration of the use of consumer devices (wearables/smartphones) is needed.

More than just sleeping in: a late timing of sleep is associated with health problems and unhealthy behaviours in adolescents

OBJECTIVE

New research suggests that the timing of sleep, or chronotype, affects the mental well-being of adolescents, however evidence of its links to physical health is limited. We investigated the associations between chronotype and various health outcomes and behaviours in a national sample of Canadian adolescents.

METHODS

Data were from the 2014 Canadian Health Behaviour in School-Aged Children survey (29,470 students; ages 10-18). Chronotype was estimated using the midpoint of sleep on weekends, corrected for catch-up sleep. We tested the associations with physical health (headache, stomach ache, back ache, dizziness, overweight, self-rated health) and health behaviours (consumption of fruits, vegetables, sweets, soft drinks, and energy drinks, smoking, physical activity, screen time) using random-effects regressions adjusted for sleep duration and individual, family, and school characteristics.

RESULTS

The average chronotype was 4:11 a.m. for boys and 4:10 for girls. Each 1-h delay in chronotype was associated with more headaches, stomach aches, and back aches [proportional odds ratios (PropORs) 1.08, 1.08, 1.07, respectively (boys), 1.10, 1.10, 1.08, respectively (girls)], and dizziness and worse self-rated health in girls (PropORs 1.10 and 1.09, respectively), but not overweight. A 1-h delay in chronotype also related to daily soft drink consumption [ORs 1.17 (boys), 1.11 (girls)], smoking [ORs 1.23 (boys), 1.37 (girls)], screen time [additional 0.64 h (boys), 0.74 h (girls)], less vegetable consumption in boys (OR 0.96), and daily energy drink consumption in girls (OR 1.42).

CONCLUSION

A later chronotype related to worse physical health and unhealthy behaviours in Canadian adolescents. Studies are needed to clarify the underlying mechanisms.

Long working hours are inversely related to sick leave in the following 3 months: a 4-year registry study

PURPOSE

The aim of this study was to investigate the effects of long working hours (≥ 12 h shifts) on sick leave using objective records of shift work exposure and of sick leave.

METHODS

A total of 1538 nurses (mean age 42.5, SD 12.0; response rate 42%) participated. Payroll and archival sick leave data over a 4-year period were retrieved from employers' records and aggregated over every third calendar month. A multilevel negative binomial model was used to investigate the effects of exposure to long working hours, on subsequent sick leave rates the following 3 months. Covariates included prior sick leave, number of shifts worked, night and evening shifts, personality, and demographic characteristics.

RESULTS

Exposure to long working hours was associated with fewer sick leave days in the subsequent 3 months [adjusted model, incidence rate ratio (IRR) = 0.946, 95% CI 0.919-0.973, p < 0.001]. The interaction long working hours by a number of work days showed that sick leave days the subsequent 3 months was higher by long shifts when number of shifts was high compared to when number of shifts was low [adjusted model, IRR 1.002, 95% CI 1.000-1.004, p < 0.05].

DISCUSSION

Long working hours was associated with fewer sick leave days. The restorative effects of extra days off with long working hours are discussed as possible explanations to this relationship.

How Young “Early Birds” Prefer Preservation, Appreciation and Utilization of Nature

Since the 1990s, the Two Major Environmental Value model (2-MEV) has been applied to measure adolescent environmental attitudes by covering two higher order factors: (i) Preservation of Nature (PRE) which measures protection preferences and (ii) Utilization of Nature (UTL) which quantifies preferences towards exploitation of nature. In addition to the 2-MEV scale, we monitored the Appreciation of Nature (APR) which, in contrast to the UTL, monitors the enjoyable utilization of nature. Finally, we employed the Morningness–Eveningness Scale for Children (MESC) which monitors the diurnal preferences and associates with personality and behavioral traits. In this study, we analyzed data from 429 Irish students (14.65 years; ±1.89 SD) with the aim of reconfirming the factor structure of the 2-MEV+APR and monitoring the relationship between the MESC and the environmental values (PRE, UTL, APR). Our findings identified a significant association between PRE and APR with MESC. In addition, we observed a gender difference. Our results suggest that morningness preference students are more likely to be protective of and appreciative towards nature. Recommendations for outreach programs as well as conclusions for environmental education initiatives in general are discussed.

Morningness-eveningness and social anxiety symptoms: the influence of depression symptoms on the indirect effect through punishment sensitivity and experiential avoidance

Social anxiety has recently been linked to morningness-eveningness; however, the psychological mechanisms underlying this relationship are not well known. As such, the purpose of the current study is to propose a model by which morningness-eveningness is related to social anxiety symptoms through punishment sensitivity and experiential avoidance within an adult American, community sample recruited via Amazon's Mechanical Turk (MTurk). It was hypothesized that experiential avoidance and punishment sensitivity would be associated with increased social anxiety symptoms and that morningness-eveningness would be negatively related to social anxiety symptoms. Furthermore, eveningness was hypothesized to be associated with increased punishment sensitivity and in turn, greater experiential avoidance. Lastly, the relationship between morningness-eveningness and social anxiety was hypothesized to be mediated by punishment sensitivity among the group with high depression levels, but not among the group with lesser depression symptoms. The results indicated that eveningness was related to social anxiety symptoms through experiential avoidance, and that depression symptoms influenced the relationship between morningness-eveningness and punishment sensitivity such that, in those high in depression symptoms, there was a significant association between eveningness and punishment sensitivity, but not among those with lower depression levels. The study findings build upon existing chronobiological research and addresses inconsistencies in previous literature.

Subjective versus objective evening chronotypes in bipolar disorder

BACKGROUND

Disturbed sleep timing is common in bipolar disorder (BD). However, most research is based upon self-reports. We examined relationships between subjective versus objective assessments of sleep timing in BD patients versus controls.

METHODS

We studied 61 individuals with bipolar I or II disorder and 61 healthy controls. Structured clinical interviews assessed psychiatric diagnoses, and clinician-administered scales assessed current mood symptom severity. For subjective chronotype, we used the Composite Scale of Morningness (CSM) questionnaire, using original and modified (1, ¾, ⅔, and ½ SD below mean CSM score) thresholds to define evening chronotype. Objective chronotype was calculated as the percentage of nights (50%, 66.7%, 75%, or 90% of all nights) with sleep interval midpoints at or before (non-evening chronotype) vs. after (evening chronotype) 04:15:00 (4:15:00a.m.), based on 25-50 days of continuous actigraph data.

RESULTS

BD participants and controls differed significantly with respect to CSM mean scores and CSM evening chronotypes using modified, but not original, thresholds. Groups also differed significantly with respect to chronotype based on sleep interval midpoint means, and based on the threshold of 75% of sleep intervals with midpoints after 04:15:00. Subjective and objective chronotypes correlated significantly with one another. Twenty-one consecutive intervals were needed to yield an evening chronotype classification match of ≥ 95% with that made using the 75% of sleep intervals threshold.

LIMITATIONS

Limited sample size/generalizability.

CONCLUSIONS

Subjective and objective chronotype measurements were correlated with one another in participants with BD. Using population-specific thresholds, participants with BD had a later chronotype than controls.

Working Conditions and Individual Differences Are Weakly Associated with Workaholism: A 2-3-Year Prospective Study of Shift-Working Nurses

This study focuses on individual differences and the demand-support-control model in relation to workaholism. We hypothesized that unfavorable working conditions (high job demands, low job control/decision latitude, and low social support at work) and individual differences concerning sleep/wake-related variables (high flexibility, high morningness, and low languidity) would be related to workaholism measured 2–3 years later. Survey data stemmed from a prospective cohort of shift-working nurses (N = 1,308). The results showed that social support at work was negatively related to workaholism, whereas job demands were positively related to workaholism. Flexibility in terms of time for working/sleeping was also positively related to workaholism. The analyses further revealed that workaholism was inversely associated with age as well as having a child or having a child move in. Conjointly, the independent variables explained 6.4% of the variance in workaholism, while their relative importance was small overall. After controlling for all other independent variables, high job demands had the strongest relationship (small-to-medium) with workaholism. This implies that less pressure from the external environment to work excessively hard may prevent an increase in workaholic behaviors. Overall, the study adds to our understanding of the relationships between working conditions, individual differences, and workaholism.

The relationship between chronotype and depressive symptoms: A meta-analysis

BACKGROUND

Expanding our understanding of the factors that influence depression is crucial for prognosis and treatment. In light of increasing evidence of an association between disrupted circadian rhythms and affective symptoms, a meta-analysis was used to examine the relationship between an eveningness chronotype and depression.

METHODS

Electronic searches of the PsycINFO, Medline, Scopus, and Google Scholar databases were conducted in February 2016. Relevant reviews, related journals, and reference lists were manually searched. Statistical data were reported or transformed to a Fisher's z correlational coefficient for effect size analysis.

RESULTS

Data from 36 studies (n =15734) met the inclusion criteria and were analysed under a random effects model. Nearly all included studies utilised the Composite Scale of Morningness (CSM) or the Morningness-Eveningness Questionnaire (MEQ) as a measure of chronotype. Overall effect size from 58 effect sizes was small (z=-.20; 95% CI: -.18 to -.23). Effect sizes based on the CSM were significantly larger than those based on the MEQ. There was no evidence of publication bias.

LIMITATIONS

The number of studies comparing different mood disorders or the potential moderating effects of gender and age were too few to draw conclusions regarding their respective effect sizes. Future research should utilise longitudinal designs to draw causal inferences on the directionality of this relationship.

CONCLUSIONS

Findings from this meta-analysis indicate an eveningness orientation is somewhat associated with more severe mood symptoms. Chronobiological approaches may contribute to the prevention and treatment of depressive disorders.

The Effects of Sleep Deprivation on Soccer Skills

Many athletes sleep poorly due to stress, travel, and competition anxiety. In the present study, we investigated the effects of sleep deprivation on soccer skills (juggling, dribbling, ball control, continuous kicking, 20 and 40 m sprint, and 30 m sprint with changes of direction). In all, 19 male junior soccer players (14-19 years old) were recruited and participated in a cross-balanced experimental study comprising two conditions; habitual sleep and 24 hours sleep deprivation. In both conditions, testing took place between 8 a.m. and 10 a.m. Order of tests was counterbalanced. Each test was conducted once or twice in a sequence repeated three times. The results revealed a negative effect of sleep deprivation on the continuous kicking test. On one test, 30 meter sprint with directional changes, a significant condition × test repetition interaction was found, indicating a steeper learning curve in the sleep deprived condition from Test 1 to Test 2 and a steeper learning curve in the rested condition from Test 2 to Test 3. The results are discussed in terms of limitations and strengths, and recommendations for future studies are outlined.

Spanish Adaptation of the Morningness-Eveningness-Stability-Scale improved (MESSi)

The aim of the present study was to conduct the preliminary adaptation of the Morningness-Eveningness-Stability-Scale improved (MESSi) to Spanish population, testing its factor structure and construct validity. Participants were 261 adults (65% women;M= 31.4,SD= 12.01) who filled out measures of Morningness-Eveningness (MESSi and CSM), sleep habits, personality traits, positive and negative affect, and subjective level of alertness during the day. Psychometric results supported a three factorial model with the factors Morning Affect, Eveningness and Distinctness (RMSEA = .072). The factors showed good internal consistence (α = 0.72–0.85). The pattern of correlations between MESSi and the other measures were in the expected direction (low to moderated size effects). Morning Affect was positively predicted by morning chronotype (R2= .64), Eveningness was negatively predicted by age and positively by evening chronotype (R2= .41), and Distinctness was negatively predicted by sex (women reported higher DI than men) and age (R2= .08). This study provides evidence for the factor structure of a new measure of Morningness-Eveningness based on a rigorous psychometric evaluation.

From Lark to Owl: developmental changes in morningness-eveningness from new-borns to early adulthood

Morningness-eveningness or chronotype changes significantly throughout the life span. This has been reported for the transition during adolescence in some studies, and to a lesser extent in early adulthood. Primary and pre-school children have been under investigation in fewer studies. This is the first comprehensive study covering the age range from very young children until early adulthood (0-30 years) based on the same measurement instrument. Here, we show that the turn towards eveningness starts at an early age in German children. Based on 26,214 cross-sectional data, we further show that at the end of adolescence, morningness-eveningness does not significantly change during early adulthood. Sex differences arise during puberty and remain until 30 years. The breaking point for the turn towards morningness is 15.7 years in girls and 17.2 boys. At the age of 0-1 years, there are about 70% morning types, and about 1% evening types, while at the age of 16 years, only 5% are morning types and 19% are evening types.

Short rest between shift intervals increases the risk of sick leave: a prospective registry study

OBJECTIVES

The purpose of this study was to use objective registry data to prospectively investigate the effects of quick returns (QR, <11 hours of rest between shifts) and night shifts on sick leave.

METHODS

A total of 1538 nurses (response rate =41.5%) answered questionnaires on demographics and personality and provided consent to link this information to registry data on shift work and sick leave from employers' records. A multilevel negative binomial model was used to investigate the predictive effect of exposure to night shifts and QR every month for 1 year, on sick leave the following month.

RESULTS

Exposure to QR the previous month increased the risk for sick leave days (incidence rate ratio (IRR)=1.066, 95% CI 1.022 to 1.108, p<0.01) and sick leave spells (IRR=1.059, 95% CI 1.025 to 1.097, p<0.001) the following month, whereas night shifts did not. 83% per cent of the nurses experienced QR within a year, and on average they were exposed to 3.0 QR per month (SD=1.6). Personality characteristics associated with shift work tolerance (low on morningness, low on languidity and high on flexibility) were not associated with sick leave, and did not moderate the relationship between QR and sick leave.

CONCLUSIONS

We found a positive linear relationship between QR and sick leave. Avoiding QR may help reduce workers' sick leave. The restricted recovery opportunity associated with QR may give little room for beneficial effects of individual characteristics usually associated with shift work tolerance.

Morningness-eveningness and amplitude - development and validation of an improved composite scale to measure circadian preference and stability (MESSi)

Measuring morningness-eveningness is an important aspect of individual differences because it is associated with many aspects of personality and health. The present study outlines recent advancements in the field of measurement and proposes an improved assessment of morningness-eveningness, such as the measurement of circadian amplitude, updating and reflecting new item developments, addressing the clock time based measures, the morning-biased items and the aspect of uni versus multidimensionality. Four studies have been carried out in Germany to present a novel development (with a total sample of N = 1181). In study I, the exploratory factor analysis (EFA) revealed three dimensions, one of morningness, one of eveningness and one of amplitude/stability. Then, items were reduced to present a clearer factor structure by removing ambiguous items. In the second study, a shortened questionnaire was applied, with 15 items (5 per construct), but Confirmatory Factor Analysis (CFA) did not provide acceptable fit indices. Refining items were made in study III, which again showed a clearer factor structure in EFA, and subsequently, in study IV, the refined set of 15 items provided a good fit of a CFA. The final questionnaire was tested for validity by applying clock times, personality questions and alertness ratings. Thus, this newly developed questionnaire contains three distinct dimensions. To reflect the new content, the scale is labelled morningness-eveningness-stability-scale improved (MESSi).

Prospective study of predictors and consequences of insomnia: personality, lifestyle, mental health, and work-related stressors

OBJECTIVE

To prospectively investigate the reciprocal relationships between personality traits, lifestyle factors, mental health, sleepiness, and work-related stressors against insomnia.

METHODS

A total of 799 Norwegian shift-working nurses (mean age 33.2 years, 90% female) participated in this prospective cohort study. They were assessed on self-report instruments (Bergen Insomnia Scale, Diurnal Type Scale, Hospital Anxiety and Depression Scale, Negative Acts Questionnaire-Revised, Work-Family Interface Scale, among others) in 2008/2009 (wave 1) and 2011 (wave 3). Structural equation modeling was employed to investigate the bidirectional relationship between a wide range of individual and work-related variables and insomnia.

RESULTS

Languidity (β = 0.18***), anxiety (β = 0.11**), depression (β = 0.14***), exposure to bullying behavior (β = 0.08*), and negative spillover between work and family life (work to family, β = 0.08*; family to work, β = 0.07*) predicted increased symptoms of insomnia over time. Morningness (β = -0.09*) and positive spillover from work to family (β = -0.11**) predicted less symptoms of insomnia over time. No support was found for night work as a predictor of increased insomnia. Insomnia was a precursor for anxiety (β = 0.11**), but not for depression (*p <0.05, **p <0.01, ***p <0.001).

CONCLUSION

The data suggested that insomnia more often emerges as a consequence of individual and work-related factors than as a precursor to them. The scope of factors causing insomnia, and factors protecting against it, should be further investigated. Insomnia should be considered in prediction models for mental illnesses and as an outcome of adverse work-related experiences.