Evaluation of two circadian rhythm questionnaires for screening for the delayed sleep phase disorder

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.

Delayed sleep wake phase disorder in adolescents: an updated review

PURPOSE OF REVIEW

This review examines the most common circadian rhythm disorder in adolescents, delayed sleep phase disorder. It explores the etiology, prevalence, clinical features, diagnostic tools and criteria, and treatment options to identify sleep disorders early in the course. This is important to help improve youths in terms of education and quality of life.

RECENT FINDINGS

Recent studies indicate that delayed sleep wake phase disorder has a range of prevalence between 1% and 16%. It is often associated with neurodevelopmental disorders (i.e. attention deficit hyperactivity disorder and autism spectrum disorder) as well as psychopathology (i.e. substance use, anxiety, and depression). It can present with a myriad of symptoms, such as insomnia, restless sleep, and poor daytime cognitive function, often seen in pediatric practice. Important diagnostic measures incorporate history-taking, sleep logs, actigraphy (i.e. Apple watches) and measurement of dim light melatonin onset. Treatments include improved sleep hygiene, chronotherapy, exogenous melatonin administration, and bright light therapy.

SUMMARY

There are many environmental and genetic factors that can predispose an individual to circadian rhythm disorders. Delayed sleep phase disorder has detrimental effects on overall health, cognition, and behavior. It is important to screen for this disorder in routine pediatric clinic visits. The goal of early intervention is to prevent health and behavioral complications and treat adolescents using a multimodal approach, especially those with affective/neurodevelopmental conditions, who are prone to having delayed sleep wake phase disorder.

Can morning affect protect us from suicide? The mediating role of general mental health in the relationship between chronotype and suicidal behavior among students

Although chronotype has been associated with suicidal behavior, current research suggest that this relationship may be mediated by other factors. The aim of this study was to assess whether chronotype, specifically morningness, may predict suicidal behavior and whether this relationship may be mediated by general mental health, depressive and anxiety symptoms, and/or social functioning among young adults. The study group comprised 306 students: 204 (65.8%) women, 101 (32.6%) men and one who chose not to identify with either option (0.3%). The participants completed The Composite Scale of Morningness, The General Health Questionnaire, 30-item version, Suicide Acceptance Questionnaire and The Suicidal Behaviors Questionnaire-Revised. Correlations between the continuous variables of interest revealed a weak, but significant, negative association between morning affect (CSM) and suicidal behavior (SBQ-R); a moderate positive association was found between suicidal behavior (SBQ-R) and depression/anxiety, and a weak one between suicidal behavior (SBQ-R) and interpersonal relations (GHQ-30). The models predicting suicidal behavior, and chronotype-related variables as predictors of suicidal behavior, were then tested. Although the morning affect predicted suicidal behavior, this effect became irrelevant when combined with mental health characteristics: psychopathological symptoms of depression and anxiety and the quality of interpersonal relations. Our findings imply that the role of chronotype is secondary to general mental health: mental disorder symptoms should be considered as the core risk factors for suicide and serve as the focus for suicide risk assessments.

Effects of Interrupted Daily Routine Due to COVID-19 on Circadian Chronotype and Leisure Time Physical Activity

Circadian chronotype is dependent on many factors including age, physical activity participation, eating and sleeping patterns, and typical schedule. Recently, the COVID-19 pandemic resulted in schedule changes for most individuals. Therefore, the purpose of this study is to examine whether sport participation influences circadian chronotype and physical activity and whether COVID-19 restrictions have impacted chronotype scores. Briefly, 128 physically active males (n = 62) and females (n = 66) between 18 and 55 years old (24.7 ± 7.1) completed a survey consisting of demographics information, the Morningness−Eveningness Questionnaire (MEQ), and the Godin Leisure Time Physical Activity Scale (LTPA). Participants were asked to answer relevant questions about their habits/preferences before and after COVID-19-related restrictions were implemented. MEQ scores categorized individuals into morning (MT), intermediate (IT), and evening (ET) chronotypes. Three-way (pre-COVID-19 chronotype x sport participation x time) repeated measures ANOVA was conducted to evaluate differences in MEQ and LTPA. A significant main effect of time was found for MEQ (p = 0.018) and LTPA (p = 0.002), indicating changes following COVID-19. A significant time x chronotype interaction was shown for MEQ (p < 0.001) with MT (p < 0.001), IT (p = 0.044), and ET (p = 0.044) individuals indicating chronotype-specific changes following COVID-19. LTPA was decreased and MEQ scores changed following COVID-19, with shifts toward IT scores.

The CLOCK 3111T/C polymorphism is associated with hour-by-hour physical activity levels only on weekends among Japanese male and female university students

BACKGROUND

CLOCK 3111T/C has been shown to be closely associated with morningness-eveningness, such as sleep-wake rhythms in healthy humans. However, previous studies examined the physical activity (PA) in a single day, and no study has investigated the relationships between CLOCK 3111T/C polymorphism and PA for an entire week. It was hypothesized that the CLOCK 3111T/C polymorphism might be associated with diurnal PA patterns, especially on the weekends.

METHODS

Eighty-one university students (male, n=14; female, n=67; age, 20.4±2.9 years) wore a digital accelerometer for 7 successive days, including the weekend, to collect hour-by-hour objectively-measured PA. CLOCK 3111T/C polymorphism was assessed using the oral mucosa. During the study, participants recorded their wake time and bedtime each day. Furthermore, lifestyle-related variables (i.e. morningness-eveningness, habitual meal and sleep timings) were collected using questionnaires. Linear mixed-effects models assessed the association of polymorphism (TT carriers vs. TC+CC carriers) with wake time and bedtime as well as daily PA throughout the week (time).

RESULTS

TT carriers had an earlier wake time (weekly mean: 44 min [95% CI, -82 to -5 min], time interaction: p=0.026) and bedtime (weekly mean: 30 min [95% CI, -61 min to - 15 sec], time interaction: p=0.048) than TC+CC carriers. Furthermore, TT carriers' wake time and bedtime on Saturday were significantly later than on other days (gene interaction: all p<0.05). On Saturday, the hour-by-hour PA in TT carriers was significantly greater than that in TC+CC carriers (hourly mean 1.7 min [95% CI, 0.2 to 3.4 min], time: p<0.001, group: p=0.028, interaction: p=0.155).

CONCLUSIONS

CLOCK 3111T/C polymorphism may be associated with objectively measured hour-by-hour PA only on Saturday. Academic/social obligations may mask the genetically determined biological rhythm of PA on weekdays.

Sleep-wake rhythm and its association with lifestyle, health-related quality of life and academic performance among Japanese nursing students: a cross-sectional study

Background

Young adults are likely to have activities and go to bed late at night due to their age-dependent delayed endogenous circadian clock. The purpose of the present study was to clarify sleep–wake rhythm and its association with lifestyle, health-related quality of life, and academic performance among nursing students.

Methods

Self-reported questionnaires were distributed to undergraduate nursing students at six universities in Japan. Sleep–wake rhythm was assessed using the morningness-eveningness questionnaire. A quantitative design using the generalized linear mixed effect model was utilized to identify the factors related to the evening type among female nursing students (n = 447).

Results

About 18% of the participants were identified as the evening type. Evening type was associated with living alone, part-time job, and club activity. Sleep duration on weekdays was shorter, meal time duration was the shortest, and the percentages of students who skipped meals and those who gained body weight were higher in the evening type than in the morning type and intermediate type. Mental health-related quality of life was lower in the intermediate type and evening type than in the morning type, while there was no difference in physical health-related quality of life among these groups. The percentages of the nursing students who have experienced absence, tardiness, falling asleep during class, and/or interference with academic achievement were higher in the evening type than in other groups.

Conclusions

The present study has important implications for nursing students’ biological characteristics and lifestyle, which are associated with their health-related quality of life and academic performance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12912-021-00748-3.

Is chronotype profile a risk indicator for caries in children and adolescents in sub-urban Nigeria?

OBJECTIVES

To determine the association between chronotype and the prevalence of caries among in-school pupils aged 6- to 16-year-old residing in a sub-urban area in Nigeria. We hypothesize that in-school pupils who are evening chronotypes will have significantly higher prevalence of caries than those who are intermediate or morning chronotypes.

METHODS

This secondary analysis of a dataset collected in 2019 from 1502 children aged 6- to 16-year-old attending private and public primary and secondary schools in Ife Central Local Government Area, Nigeria. The dependent variable was caries prevalence. The explanatory variable was participants' chronotype profile (morning, intermediate, and evening). The confounding variables were caries risk factors (socio-economic status, age at last birthday, sex, use of fluoridated toothpaste, frequency of consumption of refined carbohydrates, and oral hygiene status). Poisson regression analysis was conducted.

RESULTS

Data of 1001 (66.6%) students were retrieved. Of these, 59 (5.9%) had caries, 42 (4.2%) were evening type, 526 (52.5%) were intermediate type, and 433 (43.3%) were morning type. There was no significant association between chronotype and the prevalence of caries though children who were intermediate type (APR = 0.83; 95%CI: 0.41-1.66) and morning type (APR = 0.57; 95% CI: 0.27-1.18) were less likely to have caries than were those who were evening type.

CONCLUSION

The children and adolescents' chronotype was not a significant risk indicator for caries in the study population.

Validation of the 6-item Evening Chronotype Scale (ECS): a modified version of Composite Scale Morningness

In a previous study comparing two representative chronotype questionnaires to screen for delayed sleep-phase disorder, six items from the simplified language version of Composite Scale of Morningness (CSM) have been found to be useful and effective for screening evening-type person. In this study, we reverse coded the six items from CSM and named them Evening Chronotype Scale (ECS). The primary aim of this study was to examine the psychometric properties, validity, and test-retest reliability of the ECS when administered on mood disorder patients. The secondary aim was to further examine the relationship between circadian preferences and symptoms of mood disorders. The study sample was of 472 mood disorder patients including major depressive disorder, bipolar disorder I, and bipolar disorder II. The 13-item full version CSM and 6-item ECS were externally validated by self-reported sleep time, wake time, sleep latency, depressive symptoms, hypomanic symptoms, quality of life, and impulsivity. Cronbach's alpha was calculated for the internal consistency of the ECS, and the test-retest reliability analysis was also performed. Our results suggest that the ECS is a reliable and valid instrument to assess circadian preference in mood disorder patients. First, the ECS showed moderate to good internal consistency (Cronbach's alpha = 0.727). Also, it showed external validity comparable to that of the 13-item CSM. Participants who were more evening-oriented according to the ECS slept and woke up later, took longer time to fall asleep, showed more depressive and hypomanic symptoms, and showed lower quality of life and higher impulsivity. As circadian rhythm disruption has been shown to affect the regulation of mood symptoms in patients with mood disorders, assessment of circadian preferences may be crucial in clinical settings. We suggest that ECS appears to be an easy-to-use instrument that is reliable and valid.

Chronotype and cellular circadian rhythms predict the clinical response to lithium maintenance treatment in patients with bipolar disorder

Bipolar disorder (BD) is a serious mood disorder associated with circadian rhythm abnormalities. Risk for BD is genetically encoded and overlaps with systems that maintain circadian rhythms. Lithium is an effective mood stabilizer treatment for BD, but only a minority of patients fully respond to monotherapy. Presently, we hypothesized that lithium-responsive BD patients (Li-R) would show characteristic differences in chronotype and cellular circadian rhythms compared to lithium non-responders (Li-NR). Selecting patients from a prospective, multi-center, clinical trial of lithium monotherapy, we examined morning vs. evening preference (chronotype) as a dimension of circadian rhythm function in 193 Li-R and Li-NR BD patients. From a subset of 59 patient donors, we measured circadian rhythms in skin fibroblasts longitudinally over 5 days using a bioluminescent reporter (Per2-luc). We then estimated circadian rhythm parameters (amplitude, period, phase) and the pharmacological effects of lithium on rhythms in cells from Li-R and Li-NR donors. Compared to Li-NRs, Li-Rs showed a difference in chronotype, with higher levels of morningness. Evening chronotype was associated with increased mood symptoms at baseline, including depression, mania, and insomnia. Cells from Li-Rs were more likely to exhibit a short circadian period, a linear relationship between period and phase, and period shortening effects of lithium. Common genetic variation in the IP3 signaling pathway may account for some of the individual differences in the effects of lithium on cellular rhythms. We conclude that circadian rhythms may influence response to lithium in maintenance treatment of BD.

Chronotype and suicide: The mediating effect of depressive symptoms

BACKGROUND

Chronotype is individual characteristic, and people who stay up late are acknowledged to be more likely to experience depressive symptoms as well as impulsivity and suicide. Depression is also associated with suicidality. The purpose of this study was to investigate and analyze the role of depression in its effects on chronotype and suicidality.

METHOD

A total of 5632 university students were recruited as participants. We evaluated their chronotype, depressive symptoms, and suicidality using questionnaires. Correlation analysis, analysis of covariance, and path analysis were performed.

RESULTS

Depressive symptoms and suicidality were higher among individuals with an eveningness chronotype: the greater the depressive symptoms, the higher the suicidality. The results of path analysis showed that the direct effect of suicidality in relation to chronotype was not statistically significant, but the indirect effect of depressive symptoms was statistically significant. This result indicates that depressive symptoms fully mediated the relationship between chronotype and suicidality.

CONCLUSION

Morningness may be a protective factor, not only against depression but also against suicide. To assess the risk of suicide, we must evaluate not only depressive symptoms, but also the effects of chronotype on depressive symptoms.

Morningness-Eveningness questionnaire in bipolar disorder

The Morningness-Eveningness Questionnaire (MEQ) is among the most commonly used scales to measure chronotype. We aimed to evaluate psychometric properties and clinical correlates of MEQ in bipolar disorder. Patients with a clinical diagnosis of bipolar disorder (n = 53) answered questionnaires for chronotype (MEQ), mood (Quick Inventory of Depressive Symptoms-16, Altman Self-Rating Mania Scale), insomnia (Athens Insomnia Scale, AIS), and sleepiness (Epworth Sleepiness Scale). Mood was evaluated using Montgomery-Åsberg Depression Rating Scale and Young Mania Rating Scale. The MEQ showed high internal consistency with Cronbach's alpha of .85. Lower MEQ scores (eveningness) correlated with insomnia (AIS) (r = -.34, p = .013). The estimate for eveningness (13/53, 24.5%) in our study was higher than in comparable studies in the general population. Patients on lithium exhibited a higher mean MEQ score (56.0 on lithium vs 46.9 with no lithium, p = .007), whereas this score was lower for patients on an antidepressant (46.0 on antidepressants vs 52.6 with no antidepressants, p = .023). We conclude that the MEQ score is psychometrically reliable. However, future studies should further evaluate the association of medication with chronotype. Validation of categorical cut-offs for MEQ in a larger sample of bipolar patients is needed to increase clinical utility.

Circadian alterations during early stages of Alzheimer's disease are associated with aberrant cycles of DNA methylation in BMAL1

INTRODUCTION

Circadian alterations are prevalent in Alzheimer's disease (AD) and may contribute to cognitive impairment, behavioral symptoms, and neurodegeneration. Epigenetic mechanisms regulate the circadian clock, and changes in DNA methylation have been reported in AD brains, but the pathways that mediate circadian deregulation in AD are incompletely understood. We hypothesized that aberrant DNA methylation may affect circadian rhythms in AD.

METHODS

We investigated DNA methylation, transcription, and expression of BMAL1, a positive regulator of the circadian clock, in cultured fibroblasts and brain samples from two independent cohorts of aging and AD.

RESULTS

DNA methylation modulated rhythmic expression of clock genes in cultured fibroblasts. Moreover, rhythmic methylation of BMAL1 was altered in AD brains and fibroblasts and correlated with transcription cycles.

DISCUSSION

Our results indicate that cycles of DNA methylation contribute to the regulation of BMAL1 rhythms in the brain. Hence, aberrant epigenetic patterns may be linked to circadian alterations in AD.

Procedural Memory Consolidation in Attention-Deficit/Hyperactivity Disorder Is Promoted by Scheduling of Practice to Evening Hours

In young adults without attention-deficit/hyperactivity disorder (ADHD) training on a novel movement sequence results not only in large within-session (online) gains in task performance but also in additional (delayed, off-line) gains in the performance, expressed after an interval of sleep. In contrast, young people with ADHD, given an identical practice, were shown to improve online but expressed much smaller delayed gains overnight. As delayed gains in performance are taken to reflect procedural ("how to") memory consolidation processes, this may explain skill learning deficits in persons with ADHD. However, motor training is usually provided in morning sessions, and, given that persons with ADHD are often evening types, chronobiological constraints may constitute a hidden factor. Here, we tested the hypothesis that evening training, compared to morning training, would result in larger overnight consolidation gains following practice on a novel motor task in young women with ADHD. Participants with (N = 25) and without (N = 24) ADHD were given training on a finger opposition sequence tapping task, either in the morning or at evening. Performance was assessed before and immediately after training, overnight, and at 2 weeks post-training. Individuals with ADHD reported a general preference for evening hours. Evening training was equally effective in participants with and without ADHD, both groups showing robust consolidation gains in task performance overnight. However, the ability to express delayed gains overnight was significantly reduced in participants with ADHD if trained in the morning. Typical peers were as effective in expressing overnight consolidation phase gains irrespective of the time-of-day wherein the training session was afforded. Nevertheless, even after morning training, participants with ADHD fully retained the gains acquired within the first 24 h over an interval of about 2 weeks. Our results suggest that procedural memory consolidation processes are extant and effective in ADHD, but require that specific biobehavioral conditions be met. The affordance of training in the evening hours can relax some of the constraints on these processes in ADHD. The current results are in line with the notion that the control of what is to be retained in procedural memory is atypical or more stringent in ADHD.

Eveningness and poor sleep quality independently contribute to self-reported depression severity in psychiatric inpatients with affective disorder

Background Chronotype and insomnia have been related to the development and to an unfavourable course of depression. However, the mutual relationship of both risk factors is as yet unclear, especially in acute, clinically manifest depressive disorders. Aims The present study was carried out to elucidate the separate direct and indirect influence of chronotype and poor sleep quality on depression severity in patients hospitalized for depression. Methods Depression severity (BDI-II), chronotype (Morningness-Eveningness Questionnaire), and subjective sleep quality (Pittsburgh Sleep Quality Index total score) were assessed concurrently in inpatients with a depressive syndrome and insomnia during routine treatment. Correlations, multiple regression and bootstrapping methods for testing mediation models were applied to assess the independent direct and indirect effects of chronotype and sleep quality on depression severity, after adjusting for effects of age and gender. Results Data from 57 consecutively admitted patients (88% with major depression) were analyzed (68% women, mean age 41 ± 13 years). Significant correlations between morningness-eveningness (p <0.05) or sleep quality (p <0.01) and depression severity were found; in a multiple regression model comprising chronotype, sleep quality, age and gender, only chronotype (p <0.05) and sleep disturbances (p <0.01) remained as independent significant concurrent predictors of depression severity (R(2) = 0.184, p <0.01). Two mediation models revealed no significant results. Conclusions Eveningness and poor subjective sleep quality were independently and directly associated with higher depression severity in inpatients with depressive syndromes. Chronotype and sleep quality should be taken into account not only in risk assessment and prevention but also in hospitalized patients to develop and improve treatment options.

Normalizing sleep quality disturbed by psychiatric polypharmacy: a single patient open trial (SPOT)

There is a growing interest in personalized and preventive medicine initiatives that leverage serious patient engagement, such as those initiated and pursued among participants in the quantified-self movement. However, many of the self-assessments that result are not rooted in good scientific practices, such as exploiting controls, dose escalation strategies, multiple endpoint monitoring, etc. Areas where individual monitoring and health assessments have great potential involve sleep and behavior, as there are a number of very problematic sleep and behavior-related conditions that are hard to treat without personalization. For example, winter depression or seasonal affective disorder (SAD) is a serious, recurrent, atypical depressive disorder impacting millions each year. In order to prevent yearly recurrence antidepressant drugs are used to prophylactically treat SAD. In turn, these antidepressant drugs can affect sleep patterns, further exacerbating the condition. Because of this, possibly unique combinatorial or ‘polypharmaceutical’ interventions involving sleep aids may be prescribed. However, little research into the effects of such polypharmacy on the long-term sleep quality of treated individuals has been pursued. Employing wireless monitoring in a patient-centered study we sought to gain insight into the influence of polypharmacy on sleep patterns and the optimal course of therapy for an individual being treated for SAD with duloxetine (Cymbalta) and temazepam. We analyzed continuous-time sleep data while dosages and combinations of these agents were varied. We found that the administration of Cymbalta led to an exacerbation of the subject’s symptoms in a statistically significant way. We argue that such analyses may be necessary to effectively treat individuals with similar overall clinical manifestations and diagnosis, despite their having a unique set of symptoms, genetic profiles and exposure histories. We also consider the limitations of our study and areas for further research.

Chronotypes in Patients with Epilepsy: Does the Type of Epilepsy Make a Difference?

Circadian rhythms govern all biological functions. Circadian misalignment has a major impact on health. Late chronotype is a risk factor for circadian misalignment which in turn can affect the control of seizures in epilepsy patients. We compared a group of 87 confirmed epilepsy patients regardless of subtypes with age- and sex-matched healthy controls. We compared generalized epilepsy patients with localization related epilepsy patients and with healthy controls. We found that primary generalized epilepsy patients were 5 times more likely to have a late chronotype than healthy controls. We did not find any significant differences between localization related epilepsy patients and healthy controls or between the overall epilepsy cohort and healthy controls. Generalized epilepsy patients are more likely to be evening types as compared to those with focal epilepsy or subjects without epilepsy. Epilepsy patients do not experience the same age related increase in morningness as do age-matched healthy controls. This is important in regard to timing of AED, identifying and preventing sleep deprivation, and integrating chronotype evaluations and chronotherapy in comprehensive epilepsy care. Further studies, using objective phase markers or the impact of chronotherapy on seizure control, are necessary.

Genetic variants associated with sleep disorders

OBJECTIVE

The diagnostic boundaries of sleep disorders are under considerable debate. The main sleep disorders are partly heritable; therefore, defining heritable pathophysiologic mechanisms could delineate diagnoses and suggest treatment. We collected clinical data and DNA from consenting patients scheduled to undergo clinical polysomnograms, to expand our understanding of the polymorphisms associated with the phenotypes of particular sleep disorders.

METHODS

Patients at least 21 years of age were recruited to contribute research questionnaires, and to provide access to their medical records, saliva for deoxyribonucleic acid (DNA), and polysomnographic data. From these complex data, 38 partly overlapping phenotypes were derived indicating complaints, subjective and objective sleep timing, and polysomnographic disturbances. A custom chip was used to genotype 768 single-nucleotide polymorphisms (SNPs). Additional assays derived ancestry-informative markers (eg, 751 participants of European ancestry). Linear regressions controlling for age, gender, and ancestry were used to assess the associations of each phenotype with each of the SNPs, highlighting those with Bonferroni-corrected significance.

RESULTS

In peroxisome proliferator-activated receptor gamma, coactivator 1 beta (PPARGC1B), rs6888451 was associated with several markers of obstructive sleep apnea. In aryl hydrocarbon receptor nuclear translocator-like (ARNTL), rs10766071 was associated with decreased polysomnographic sleep duration. The association of rs3923809 in BTBD9 with periodic limb movements in sleep was confirmed. SNPs in casein kinase 1 delta (CSNK1D rs11552085), cryptochrome 1 (CRY1 rs4964515), and retinoic acid receptor-related orphan receptor A (RORA rs11071547) were less persuasively associated with sleep latency and time of falling asleep.

CONCLUSIONS

SNPs associated with several sleep phenotypes were suggested, but due to risks of false discovery, independent replications are needed before the importance of these associations can be assessed, followed by investigation of molecular mechanisms.

Intense illumination in the morning hours improved mood and alertness but not mental performance

Cognitive performance and alertness are two determinants for work efficiency, varying throughout the day and depending on bright light. We conducted a prospective crossover study evaluating the impacts of exposure to an intense, early morning illumination on sustained attention, alertness, mood, and serum melatonin levels in 33 healthy individuals. Compared with a dim illumination, the intense illumination negatively impacted performance requiring sustained attention; however, it positively impacted subjective alertness and mood and had no impact on serum melatonin levels. These results suggest that brief exposure to bright light in the morning hours can improve subjective measures of mood and alertness, but can also have detrimental effects on mental performance as a result of visual distraction. Therefore, it is important that adequate lighting should correspond to both non-visual and visual demands.

Circadian polymorphisms in night owls, in bipolars, and in non-24-hour sleep cycles

People called night owls habitually have late bedtimes and late times of arising, sometimes suffering a heritable circadian disturbance called delayed sleep phase syndrome (DSPS). Those with DSPS, those with more severe progressively-late non-24-hour sleep-wake cycles, and those with bipolar disorder may share genetic tendencies for slowed or delayed circadian cycles. We searched for polymorphisms associated with DSPS in a case-control study of DSPS research participants and a separate study of Sleep Center patients undergoing polysomnography. In 45 participants, we resequenced portions of 15 circadian genes to identify unknown polymorphisms that might be associated with DSPS, non-24-hour rhythms, or bipolar comorbidities. We then genotyped single nucleotide polymorphisms (SNPs) in both larger samples, using Illumina Golden Gate assays. Associations of SNPs with the DSPS phenotype and with the morningness-eveningness parametric phenotype were computed for both samples, then combined for meta-analyses. Delayed sleep and "eveningness" were inversely associated with loci in circadian genes NFIL3 (rs2482705) and RORC (rs3828057). A group of haplotypes overlapping BHLHE40 was associated with non-24-hour sleep-wake cycles, and less robustly, with delayed sleep and bipolar disorder (e.g., rs34883305, rs34870629, rs74439275, and rs3750275 were associated with n=37, p=4.58E-09, Bonferroni p=2.95E-06). Bright light and melatonin can palliate circadian disorders, and genetics may clarify the underlying circadian photoperiodic mechanisms. After further replication and identification of the causal polymorphisms, these findings may point to future treatments for DSPS, non-24-hour rhythms, and possibly bipolar disorder or depression.

Reviewing the psychometric properties of contemporary circadian typology measures

The accurate measurement of circadian typology (CT) is critical because the construct has implications for a number of health disorders. In this review, we focus on the evidence to support the reliability and validity of the more commonly used CT scales: the Morningness-Eveningness Questionnaire (MEQ), reduced Morningness-Eveningness Questionnaire (rMEQ), the Composite Scale of Morningness (CSM), and the Preferences Scale (PS). In addition, we also consider the Munich ChronoType Questionnaire (MCTQ). In terms of reliability, the MEQ, CSM, and PS consistently report high levels of reliability (>0.80), whereas the reliability of the rMEQ is satisfactory. The stability of these scales is sound at follow-up periods up to 13 mos. The MCTQ is not a scale; therefore, its reliability cannot be assessed. Although it is possible to determine the stability of the MCTQ, these data are yet to be reported. Validity must be given equal weight in assessing the measurement properties of CT instruments. Most commonly reported is convergent and construct validity. The MEQ, rMEQ, and CSM are highly correlated and this is to be expected, given that these scales share common items. The level of agreement between the MCTQ and the MEQ is satisfactory, but the correlation between these two constructs decreases in line with the number of "corrections" applied to the MCTQ. The interesting question is whether CT is best represented by a psychological preference for behavior or by using a biomarker such as sleep midpoint. Good-quality subjective and objective data suggest adequate construct validity for each of the CT instruments, but a major limitation of this literature is studies that assess the predictive validity of these instruments. We make a number of recommendations with the aim of advancing science. Future studies need to (1) focus on collecting data from representative samples that consider a number of environmental factors; (2) employ longitudinal designs to allow the predictive validity of CT measures to be assessed and preferably make use of objective data; (3) employ contemporary statistical approaches, including structural equation modeling and item-response models; and (4) provide better information concerning sample selection and a rationale for choosing cutoff points.