Circadian rhythmicity of cortisol and body temperature: morningness-eveningness effects

Effects of Chronotherapeutic Interventions in Adults With ADHD and Delayed Sleep Phase Syndrome (DSPS) on Regulation of Appetite and Glucose Metabolism

Background: ADHD is highly comorbid with Delayed Sleep Phase Syndrome (DSPS). Both are associated with obesity and diabetes, which can be caused by long-term dysregulations of appetite and glucose metabolism. This study explores hormones involved in these processes and the effects of chronotherapeutic interventions in a small sample of adults with ADHD and DSPS. Methods: Exploratory, secondary analysis of data from the PhASE study, a three-armed randomized clinical trial, are presented, including 37 adults (18-53 years) with ADHD and DSPS receiving three weeks of 0.5 mg/day (1) placebo, (2) melatonin, or (3) melatonin plus 30 minutes of bright light therapy (BLT). Leptin (appetite-suppressing), ghrelin (appetite-stimulating), insulin, insulin-like growth factor-1 (IGF-1), and glucose were measured from blood collected at 08:00 hours. Salivary cortisol was collected during the first 30 minutes after awakening and self-reported appetite was assessed. Results: Baseline leptin and IGF-1 levels were higher than reference ranges, and ghrelin and cortisol levels were lower, while insulin and glucose were normal. Melatonin treatment decreased leptin and insulin. Other outcomes remained unchanged and melatonin + BLT had no effects. Conclusion: Due to the small sample size and exploratory nature of the study, results should be interpreted with caution. Overall, these results show no strong indications for dysregulation of appetite and glucose metabolism to suggest high risk of obesity and diabetes in this small sample of adults with ADHD and DSPS. However, baseline appetite was suppressed, likely because measurements took place in the early morning which could be considered the biological night for this study population. Melatonin treatment seemed to cause subtle changes in appetite-regulating hormones suggesting increased appetite. Chronotherapeutic treatment may affect appetite-regulating hormones by advancing the biological rhythm and/or altering eating behaviors, but this remains to be investigated in larger samples using detailed food diaries.

A prospective examination of sleep chronotype and future suicide intent among adults in the United Kingdom: A test of the integrated motivational volitional model of suicide

OBJECTIVES/BACKGROUND

Prior research identified a connection between evening chronotype and suicidality, but the mechanism underlying that connection is not well understood. The Integrated Motivational Volitional (IMV) Model of Suicide may provide a theoretical explanation for this link. The current project includes a three-time point longitudinal survey to examine whether 1) suicide intent likelihood varies across time, 2) chronotype affects suicide intent likelihood prospectively, and 3) defeat and entrapment explain the association between chronotype and suicide intent likelihood.

PATIENTS/METHODS

Participants (n = 187 UK adults) completed a baseline survey (demographics, chronotype (morning-eveningness; MEQ), defeat and entrapment, and perceived intent to make a future suicide attempt), and follow-up surveys (MEQ and suicide intent likelihood) 3 and 6 months later.

RESULTS

Results indicated that suicidal intent at 6-month follow-up was lower than baseline or 3-month follow-up. It was also found that strong evening chronotype at baseline is associated with increased suicidal intent 6 months later, and that defeat mediates this relationship.

CONCLUSION

Our theoretically informed findings shed light on the psychological mechanisms linking chronotype (i.e., eveningness) and future suicide intent by highlighting the role of defeat and entrapment. We propose that feelings of defeat might be derived from evening types' experiences of social jetlag (resulting from conflict between biologically driven sleep schedules and externally dictated social schedules), which consequently drives entrapment and greater future suicide intent. Within this context, defeat and entrapment may be good transdiagnostic and modifiable target variables for future intervention development.

The clockwork of champions: Influence of circadian biology on exercise performance

Exercise physiology and circadian biology are distinct and long-standing fields. Recently they have seen increased integration, largely due to the discovery of the molecular components of the circadian clock and recognition of human exercise performance differences over time-of-day. Circadian clocks, ubiquitous in cells, regulate a daily tissue specific program of gene expression that contribute to temporal patterns of physiological functions over a 24-h cycle. Understanding how circadian clock function in skeletal muscle, as well as other tissues contribute to exercise performance is still in the very early stages. This review provides background on this emerging field with a review of early exercise and time-of-day studies in both human and animals. We then move into the role of the circadian clock and its daily program of gene expression in skeletal muscle with a focus on specific metabolic and physiological outputs that vary over time-of-day. Lastly, we discuss the recognition that the timing of exercise communicates with the skeletal muscle circadian clock to adjust its phase settings and why this maybe important for performance and health.

Bimodal diurnal preference in undergraduate students is associated with negative health and sleep outcomes

The bimodal preference is a fourth diurnal preference proposed by re-scoring the Morningness-Eveningness Questionnaire. The present work aimed to describe the prevalence of the bimodal preference in a sample of undergraduate students and to characterize the bimodal type in terms of their health and sleep-related outcomes. A web-based cross-sectional study conducted between September 2018 and March 2021 (convenience sampling method). The sample was composed of undergraduate students who completed an electronic form that included the Morningness and Eveningness Questionnaire, the Pittsburgh Sleep Quality Index, the Self-Compassion Scale, the Epworth Sleepiness Scale, the Hospital Anxiety and Depression Scale, and the World Health Organization Subjective Well-Being Index. The final sample consisted of 615 students (82% female, mean age: 23.4 ± 6.5 years), of whom 108 (18%) had positive bimodality indexes. Bimodal subjects comprised 48 students, 8% of the total sample. Bimodal subjects had poorer subjective sleep quality, more daytime sleepiness, lower subjective well-being, greater anxiety and depression symptoms, and lower self-compassion than morning and/or intermediate types; they did not differ from evening types. The description of bimodal diurnal preference in this population may be of interest for the design of academic policies more in line with the circadian reality of students.

Acute stress promotes effort mobilization for safety-related goals

Although the acute stress response is a highly adaptive survival mechanism, much remains unknown about how its activation impacts our decisions and actions. Based on its resource-mobilizing function, here we hypothesize that this intricate psychophysiological process may increase the willingness (motivation) to engage in effortful, energy-consuming, actions. Across two experiments (n = 80, n = 84), participants exposed to a validated stress-induction protocol, compared to a no-stress control condition, exhibited an increased willingness to exert physical effort (grip force) in the service of avoiding the possibility of experiencing aversive electrical stimulation (threat-of-shock), but not for the acquisition of rewards (money). Use of computational cognitive models linked this observation to subjective value computations that prioritize safety over the minimization of effort expenditure; especially when facing unlikely threats that can only be neutralized via high levels of grip force. Taken together, these results suggest that activation of the acute stress response can selectively alter the willingness to exert effort for safety-related goals. These findings are relevant for understanding how, under stress, we become motivated to engage in effortful actions aimed at avoiding aversive outcomes.

Influence of acute dietary nitrate supplementation timing on nitrate metabolism, central and peripheral blood pressure and exercise tolerance in young men

PURPOSE

Dietary nitrate (NO3-) supplementation can lower systolic blood pressure (SBP) and improve exercise performance. Salivary flow rate (SFR) and pH are key determinants of oral NO3- reduction and purported to peak in the afternoon. We tested the hypotheses that NO3--rich beetroot juice (BR) would increase plasma [nitrite] ([NO2-]), lower SBP and improve exercise performance to a greater extent in the afternoon (AFT) compared to the morning (MORN) and evening (EVE).

METHOD

Twelve males completed six experimental visits in a repeated-measures, crossover design. NO3--depleted beetroot juice (PL) or BR (~ 13 mmol NO3-) were ingested in the MORN, AFT and EVE. SFR and pH, salivary and plasma [NO3-] and [NO2-], brachial SBP and central SBP were measured pre and post supplementation. A severe-intensity exercise tolerance test was completed to determine cycling time to exhaustion (TTE).

RESULTS

There were no between-condition differences in mean SFR or salivary pH. The elevation in plasma [NO2-] after BR ingestion was not different between BR-MORN, BR-AFT and BR-EVE. Brachial SBP was unchanged following BR supplementation in all conditions. Central SBP was reduced in BR-MORN (- 3 ± 4 mmHg), BR-AFT (- 4 ± 3 mmHg), and BR-EVE (- 2 ± 3 mmHg), with no differences between timepoints. TTE was not different between BR and PL at any timepoint.

CONCLUSION

Acute BR supplementation was ineffective at improving TTE and brachial SBP and similarly effective at increasing plasma [NO2-] and lowering central SBP across the day, which may have implications for informing NO3- supplementation strategies.

The effect of physical barriers under a raised house on mosquito entry: an experimental study in rural Gambia

BACKGROUND

Anopheles gambiae, the major malaria mosquito in sub-Saharan Africa, feed largely indoors at night. Raising a house off the ground with no barriers underneath reduces mosquito-house entry. This experiment tested whether walling off the space under an elevated hut affects mosquito-hut entry.

METHODS

Four inhabited experimental huts, each of which could be moved up and down, were used in rural Gambia. Nightly collections of mosquitoes were made using light traps and temperature and carbon dioxide levels monitored indoors and outdoors using loggers. Each night, a reference hut was kept at ground level and three huts raised 2 m above the ground; with the space under the hut left open, walled with air-permeable walls or solid walls. Treatments were rotated every four nights using a randomized block design. The experiment was conducted for 32 nights. Primary measurements were mosquito numbers and indoor temperature in each hut.

RESULTS

A total of 1,259 female Anopheles gambiae sensu lato were collected in the hut at ground level, 655 in the hut with an open ground floor, 981 in the hut with air-permeable walls underneath and 873 in the hut with solid walls underneath. Multivariate analysis, adjusting for confounders, showed that a raised hut open underneath had 53% fewer mosquitoes (95% CI 47-58%), those with air-permeable walls underneath 24% fewer (95% CI 9-36%) and huts with solid walls underneath 31% fewer (95% CI 24-37%) compared with a hut on the ground. Similar results were found for Mansonia spp. and total number of female mosquitoes, but not for Culex mosquitoes where hut entry was unaffected by height or barriers. Indoor temperature and carbon dioxide levels were similar in all huts.

CONCLUSION

Raising a house 2 m from the ground reduces the entry of An. gambiae and Mansonia mosquitoes, but not Culex species. The protective effect of height is reduced if the space underneath the hut is walled off.

Association of Meal Timing with Sleep Quality and Anxiety According to Chronotype: A Study of University Students

There are several determinants of mental health symptoms, ranging from individual characteristics to social factors. Consistent with patterns in the general population, students with evening characteristics tend to exhibit more anxiety symptoms and poorer sleep quality compared to morning students. Meal timing also appears to affect sleep and may be associated with mental health symptoms. In this context, the aim of the present study was to investigate the association of the timing of the main and last meals of the day with sleep quality and anxiety levels, according to the chronotype of university students. This study was conducted in colleges in São Paulo, Brazil, and involved application of a questionnaire to 162 university students. The questionnaire collected sociodemographic information meal and study times, and included scales assessing eveningness and morningness, sleep quality, and anxiety. Students demonstrating a phase delay in both chronotype and dinner timing exhibited higher levels of anxiety compared to morning-type students. Although no associations were observed between meal timing and sleep quality, sleeping later was associated with poorer sleep quality. The study suggests that evening students and those who eat late at night are more prone to presenting mental health symptoms. More studies are needed to further investigate this association.

Variability of corticospinal and spinal reflex excitability for the ankle dorsiflexor tibialis anterior across repeated measurements in people with and without incomplete spinal cord injury

To adequately evaluate the corticospinal and spinal plasticity in health and disease, it is essential to understand whether and to what extent the corticospinal and spinal responses fluctuate systematically across multiple measurements. Thus, in this study, we examined the session-to-session variability of corticospinal excitability for the ankle dorsiflexor tibialis anterior (TA) in people with and without incomplete spinal cord injury (SCI). In neurologically normal participants, the following measures were obtained across 4 days at the same time of day (N = 13) or 4 sessions over a 12-h period (N = 9, at 8:00, 12:00, 16:00, and 20:00): maximum voluntary contraction (MVC), maximum M-wave and H-reflex (Mmax and Hmax), motor evoked potential (MEP) amplitude, and silent period (SP) after MEP. In participants with chronic incomplete SCI (N = 17), the same measures were obtained across 4 days. We found no clear diurnal variation in the spinal and corticospinal excitability of the TA in individuals with no known neurological conditions, and no systematic changes in any experimental measures of spinal and corticospinal excitability across four measurement days in individuals with or without SCI. Overall, mean deviations across four sessions remained in a range of 5-13% for all measures in participants with or without SCI. The study shows the limited extent of non-systematic session-to-session variability in the TA corticospinal excitability in individuals with and without chronic incomplete SCI, supporting the utility of corticospinal and spinal excitability measures in mechanistic investigation of neuromodulation interventions. The information provided through this study may serve as the reference in evaluating corticospinal plasticity across multiple experimental sessions.

Hemodialysis-induced chronodisruption and chronotype distribution in patients with chronic kidney disease

Changes in circadian rhythms have been observed in patients with chronic kidney disease (CKD), and evidence suggests that these changes can have a negative impact on health. This study aimed to investigate the existence of hemodialysis-induced chronodisruption, the chronotype distribution, and their association with sleep quality and quality of life (QoL). This was a cross-sectional study that enrolled 165 patients (mean age: 51.1 ± 12.5 y, 60.6% male) undergoing hemodialysis from three local units. The following instruments were used: the Morning-Eveningness Questionnaire (MEQ); a modified version of the Munich Chronotype Questionnaire (MCQT) to estimate hemodialysis-induced chronodisruption (HIC); the Kidney Disease QoL Short Form (KDQOL-SF); the Epworth Sleepiness Scale (ESS); the Pittsburgh Sleep Quality Index (PSQI) and the 10-Cognitive Screener (10-CS). HIC was present in 40.6% of CKD patients. Morning chronotype was prevalent in CKD patients (69%) compared to evening-type (17.1%) and significantly different from a paired sample from the general population (p < 0.001). HIC and chronotype were associated with different domains of QoL but not with sleep quality. This study suggests that there is a HIC and that morning chronotype is associated with CKD patients undergoing hemodialysis, with implications for QoL.

Evening Chronotype and Suicide: Exploring Neuroinflammation and Psychopathological Dimensions as Possible Bridging Factors-A Narrative Review

A chronotype is generally defined as the variability of the phase angle of entrainment, while the latter reflects the relationship between the timing of a certain rhythm (e.g., the sleep-wake cycle) and the timing of an external temporal cue. Individuals can be placed on a spectrum from "morning types" (M types) to "evening types" (E types). E-chronotype has been proposed as a transdiagnostic risk factor for psychiatric conditions, and it has been associated with psychopathological dimensions. Eveningness seems to be correlated with both suicidal ideation (SI) and suicidal behavior (SB) through several possible mediating factors. Immunological alterations have also been linked to later chronotypes and SI/SB. This narrative review aims to summarize the evidence supporting the possible association between chronotypes and suicide and the eventual mediating role of neuroinflammation and several psychopathological dimensions. A search of the literature (2003-2023) was conducted using various databases: PUBMED, EMBASE, Scopus, UpToDate, PsycINFO, and Cochrane Library. English-language articles were collected and screened for eligibility. Despite the apparent absence of a direct correlation between E-chronotype and suicidality, E-chronotype promotes a chain of effects that could be involved in an increased risk of SB, in which with neuroinflammation possibly plays an intriguing role and some psychopathological dimensions may stand out.

Chronotype is differentially associated with lifetime mood and panic-agoraphobic spectrum symptoms in patients with bipolar disorder and healthy controls

OBJECTIVE

Although the association between chronotype and mood disorders has been consistently reported, conversely, attempts to measure the association between chronotype and anxiety symptoms have generated inconsistent results. We aimed at evaluating whether chronotype (assessed through subjective and objective measures) is associated with lifetime mood and panic-agoraphobic spectrum symptoms in healthy controls (HCs) and in patients with bipolar disorder (BD).

METHODS

Overall, 173 subjects, patients with BD in euthymic phase (n = 76) and HC (n = 97), were evaluated through the reduced Morningness-Eveningness Questionnaire (rMEQ), actigraphy monitoring and mood and panic-agoraphobic spectrum self-report (MOODS-SR and PAS-SR). The discrepancy between objective (actigraphic-based) versus subjective (rMEQ-based) circadian typology was estimated through the Circadian Classification Discrepancy Index (CCDI).

RESULTS

rMEQ-based evening chronotype (ET) was associated with higher scores in MOODS-SR depressive and rhythmicity and vegetative functions domains in HC and BD.Both ET and morning chronotypes (MT) were associated with higher PAS-SR scores in BD only. Actigraphic-based MT was associated with higher MOODS-SR depressive scores in HC. Likewise, the discrepancy between actigraphic-based and rMEQ-based circadian typology was associated with depressive symptoms in HC only.

CONCLUSION

Self-reported ET was consistently associated with mood symptoms, while associations with panic-agoraphobic symptoms only emerged in BD and involved both extreme chronotypes. The discrepancy between the preferred circadian typology (rMEQ-based) and the actual one (actigraphic-based) could contribute to depressive symptoms in HC. These results pave the way for interventional studies targeting circadian typology in an attempt to prevent or treat mental health disorders.

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

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

Salivary cortisol concentration and perceived stress measure in response to acute natural stress: The role of morningness-eveningness preference

Chronotype reflects the morningness-eveningness preference over a 24-h period. Significant data indicates meaningful differences between evening types (ET) and morning types (MT) in behavior, personality traits, health and well-being. The aim of this study was to investigate cortisol response and subjective perceived stress of MT and ET individuals in response to an acute natural stressor. Twenty six definite MT (mean age 23.4 ± 1.7) and twenty six definite ET (mean age 23.8 ± 1.3) college students were recruited for this study. Participants were instructed to evaluate their perceived subjective stress and to provide saliva samples for cortisol levels at four different time points: Morning of regular school day, morning immediately before a final exam, afternoon of a regular school day and afternoon immediately before a final exam. For general mood assessment, the participants were also asked to fill out the Positive and Negative Affect Schedule (PANAS) questionnaire. The most outstanding finding of this study was the blunting of cortisol increase in response to acute stress in the morning in the ET group: Salivary cortisol was higher before a final exam only in MT but not in ET. However, no differences between the groups were found in the subjective stress measure. In the PANAS scale, ET showed lower positive affect, and a trend towards a higher negative affect. Overall, our results suggest dysregulation of cortisol response in ET individuals, possibly due to their daily struggle to function in a morning-oriented society. These results further highlight the challenges faced by ET individuals and raise the question of possible interventions to assist them.

Metabolic Adaptations to Morning Versus Afternoon Training: A Systematic Review and Meta-analysis

BACKGROUND

Some physiological responses such as circulating glucose as well as muscle performance show a circadian rhythmicity. In the present study we aimed to quantitatively synthesize the data comparing the metabolic adaptations induced by morning and afternoon training.

METHODS

PubMed, SCOPUS, and Web of Science databases were systematically searched for studies comparing the metabolic adaptations (> 2 weeks) between morning and afternoon training. A meta-analysis was performed using random-effects models with DerSimonian-Laird methods for fasting blood glucose, hemoglobin A1c (HbAc1), homeostatic model assessment (HOMA), insulin, triglycerides, total cholesterol, low-density lipoprotein (LDL), and high-density lipoprotein (HDL).

RESULTS

We identified 9 studies with 11 different populations (n = 450 participants). We found that afternoon exercise was more effective at reducing circulating triglycerides [standardized mean difference (SMD) - 0.32; 95% confidence interval (CI) - 0.616 to - 0.025] than morning training. Moreover, afternoon tended to decrease fasting blood glucose (SMD - 0.24; 95% CI - 0.478 to 0.004) to a greater extent than morning training.

CONCLUSION

Metabolic adaptations to exercise may be dependent on the time of day. Morning training does not show superior effects to afternoon exercise in any of the analyzed outcomes. However, afternoon training is more effective at reducing circulating triglyceride levels and perhaps at reducing fasting blood glucose than morning training. The study was preregistered at PROSPERO (CRD42021287860).

Exploring synchrony effects in performance on tasks involving cognitive inhibition: An online study of young adults

Inhibition is one of the core components of cognitive control. In experimental tasks which measure cognitive inhibition, performance may vary according to an interplay of individuals' chronotype and the time of day of testing ("synchrony effect", or the beneficial impact on cognitive performance of aligning testing with the time of day preferred by an individual's chronotype). Some prior studies have reported a synchrony effect specifically emerging in activities which require cognitive inhibition, but not in general processing speed, but existing findings are inconsistent. If genuine, synchrony effects should be taken into account when comparing groups of participants. Here we explored whether synchrony effects emerge in a sample of young adults. In a multi-part online study, we captured various components of inhibition (response suppression; inhibitory control; switching) plus a general measure of processing speed across various times of the day. Individuals' chronotype was included as a predictor of performance. Critically, we found no evidence of a synchrony effect (an association between chronotype and component of interest where the directionality is dependent on time of testing) in our study.

Chronotype and athletes’ performance in sports: A narrative review

The circadian system is managed by the suprachiasmatic nucleus, which is also called a master clock, and peripheral clocks spread all over the body. A complex system of neuronal, hormonal, and autonomous signals coordinates these clocks. However, this narrative review aimed to discuss the influence of circadian rhythms on the athlete’s performance, rate of perceived exertion, resynchronization, and aerobic and anaerobic exercise. An adequately timed wake-up is believed to play an essential role in an athlete’s performance. Based on the literature, chronotype appears to correlate with ratings of perceived exertion and fatigue scores, and morning types are less fatigued in the morning. When chronotype was evaluated, fatigue and vigor had time-by-group interactions. Swimmers with morning-type profiles showed lower fatigue scores before the (06:30 hour) time test than before the (18:30 hour) time test, while those with neither-type profiles had similar fatigue scores in both sessions. Vigor scores were also higher in the morning types than in the neither-types (17.9±7.1) before the morning test and (15.6±5.5) before the evening test. Studies have also shown that exercise enhances aerobic capacity based on the day. However, several reasons can lead to conflicting evidence regarding the chronotype effect on performance studies. Thus, more research is needed regarding the chronotype effect on athletes’ performance and the impact of time of day on muscle strength.

A better alignment between chronotype and school timing is associated with lower grade retention in adolescents

Schools start early in the morning all over the world, contrasting with adolescents' late chronotype. Interestingly, lower academic performance (i.e. grades or qualifications) was associated with later chronotypes. However, it is unclear whether it is a direct effect of chronotype or because students attend school too early to perform at their best. Moreover, little is known about how this affects students' academic success beyond their grades. To address this gap in knowledge, we studied how school timing and chronotype affect grade retention (i.e. repeat a year) in a unique sample of students randomly assigned to one of three different school timings (starting at 07:45, 12:40, or 17:20). Even when controlling for academic performance, we found that later chronotypes exhibit higher odds of grade retention only in the morning, but not in later school timings. Altogether, ensuring a better alignment between school timing and students' biological rhythms might enhance future opportunities of adolescents.

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.

Beyond sleep: A multidimensional model of chronotype

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

Chronotype, Time of Day, and Performance on Intelligence Tests in the School Setting

Research suggests the existence of an association between chronotype and intellectual performance, but the nature of this link remains unclear. Studies conducted in a laboratory setting point to the synchrony effect (better performance at a person's preferred time of day) for fluid intelligence, but not for crystallized intelligence, whereas studies that have analyzed students' grades suggest that the effect exists for both. In the present study, we aimed to verify the synchrony effect by applying direct measures of crystallized intelligence, fluid intelligence, and subjective sleepiness-alertness in a sample of high school students during their morning or afternoon class. The results revealed a synchrony effect for crystallized, but not for fluid intelligence. During morning class, students with a morning chronotype performed better than evening chronotypes on a test of crystallized intelligence, whereas during afternoon class there was no difference between chronotypes. The association resulted from decreased performance during morning class in evening chronotypes that improved during afternoon class and constant performance in morning chronotypes. These effects were independent of sleepiness-alertness levels. The results suggest that individual differences between chronotypes may be important for tasks performed during morning classes, but not during afternoon ones, and that performance across school days may depend on time of day in evening chronotypes.

Chronotypes and their Association with Obesity-Related Lifestyle Behaviors among Young Female Adults

Circadian rhythms have emerged as key influences on lifestyle behaviors. Circadian rhythms vary inter-individually, and people can be stratified by circadian preference, known as their chronotype, from extreme morning types to extreme evening types. Young adults undergo chronotype changes that involve shifts from morning to evening types. We aimed to examine the association between chronotype and obesity-related lifestyle behaviors, including dietary intake, physical activity, and sleep patterns, among young females. A total of 387 college female students aged 18-25 years completed this cross-sectional study. The participants were classified into three groups (morning, intermediate, and evening types) according to the Morningness-Eveningness Questionnaire (MEQ; long version) score. Each individual's anthropometry and body composition were measured. Dietary intakes were assessed using a 24-h dietary recall. The Bouchard Three-Day Physical Activity Record was used to assess physical activity levels. Sleep patterns were evaluated using the Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS). The differences between chronotype groups were tested using a Chi-square test and one-way ANOVA. The chronotypes were significantly associated with sleep quality (p = 0.010) and daytime sleepiness (p = 0.035). However, no significant associations between dietary intake, physical activity, and sleep duration with the chronotypes were found. Our results show that both sleep quality and daytime sleepiness were associated with the chronotypes. Further research is warranted to identify the potential bidirectional associations between circadian rhythms and lifestyle behaviors among different age groups.

Chronotype and Sleep Quality in Obesity: How Do They Change After Menopause?

PURPOSE OF REVIEW

This review primarily provides an overview of the current evidence on chronotype (which reflects an individual's preference for the timing of sleeping, eating, and activity in a 24-h period) and sleep quality changes in obesity in postmenopausal women. It also explores possible nutritional strategies to manage these changes in this phase of a woman's life.

RECENT FINDINGS

Menopause is a life stage frequently associated with sleep disturbances and changes in circadian rhythms. Sleep disturbances are one of the main symptoms of menopause and are caused by several factors such as hormonal changes, obesity, and melatonin reduction. In addition, the chronotype also changes following menopause. Nutritional strategies are essential because they could help manage menopausal sleep disturbances and circadian misalignment, particularly by tackling obesity and overweight. In the management of postmenopausal women, especially those experiencing obesity, careful assessment of sleep disturbances and chronotype and subsequent development of the most appropriate treatment, including nutritional management, should be part of the treatment routine.

Predictors of stress in college students during the COVID-19 pandemic

Background

College students experience high stress levels during emergency remote classes in the COVID-19 pandemic. However, it is not clear whether this is due to the summation effect of both stressors (classes and pandemic). Therefore, the aim of this study was to investigate predictors of stress in college students before and during remote classes five months after the beginning of the COVID-19 pandemic.

Methods

The study was conducted before (BRC, July-August 2020) and during remote classes (DRC, October-November 2020). The sample consisted of 177 individuals (80 in BRC, 97 in DRC). Students were asked to self-collect saliva for cortisol analysis at each moment of the study, and to fill out a form to characterize the individual and assess the chronotype (Morningness-Eveningness Questionnaire), sleep quality (Pittsburgh Sleep Quality Index) and the stress (Perceived Stress Scale–10).

Results

There was no difference between the evaluated periods for cortisol, perceived stress or sleep quality. Predictors for cortisol levels were gender, academic semester, chronotype, sleep quality and sadness due to pandemic (p<0.001).

Limitations

Short interval between BRC and DRC assessments of perceived stress and salivary cortisol.

Conclusions

Age, sex, income, academic semester, chronotype, and the impact of the pandemic on mood are predictors of stress among college students. In addition, emergency remote classes and sleep quality contribute to less perceived stress.

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.

Hair cortisol level might be indicative for a 3PM approach towards suicide risk assessment in depression: comparative analysis of mentally stable and depressed individuals versus individuals after completing suicide

Depression and suicidal behavior are interrelated, stress-associated mental health conditions, each lacking biological verifiability. Concepts of predictive, preventive, and personalized medicine (3PM) are almost completely missing for both conditions but are of utmost importance. Prior research reported altered levels of the stress hormone cortisol in the scalp hair of depressed individuals, however, data on hair cortisol levels (HCL) for suicide completers (SC) are missing. Here, we aimed to identify differences in HCL between subject with depression (n = 20), SC (n = 45) and mentally stable control subjects (n = 12) to establish the usage of HCL as a new target for 3PM. HCL was measured in extracts of pulverized hair (1-cm and 3-cm hair segments) using ELISA. In 3-cm hair segments, an average increase in HCL for depressed patients (1.66 times higher; p = .011) and SC (5.46 times higher; p = 1.65 × 10⁻⁵) compared to that for controls was observed. Furthermore, the average HCL in SC was significantly increased compared to that in the depressed group (3.28 times higher; p = 1.4 × 10⁻⁵). A significant correlation between HCL in the 1-cm and the 3-cm hair segments, as well as a significant association between the severity of depressive symptoms and HCL (3-cm segment) was found. To conclude, findings of increased HCL in subjects with depression compared to that in controls were replicated and an additional increase in HCL was seen in SC in comparison to patients with depression. The usage of HCL for creating effective patient stratification and predictive approach followed by the targeted prevention and personalization of medical services needs to be validated in follow-up studies.

Association between Breakfast Meal Categories and Timing of Physical Activity of Japanese Workers

Background: Breakfast is the most important meal of the day and has been associated with longevity. Regular breakfast consumers often have a healthy lifestyle, including a healthy diet and regular physical activity. Methods: We examined the association between breakfast type, chronotype (morningness-eveningness), and physical activity in 3395 Japanese workers using a cross-sectional web survey. Results: Participants who ate Japanese breakfasts showed an early chronotype, while those who ate breakfast cereal exhibited a later chronotype. Physical activity was positively associated with adopting a Japanese breakfast style. Japanese breakfast eaters performed physical activities from 6:00–9:00 compared with other breakfast eaters. Conclusion: Our findings suggest that eating a Japanese breakfast is associated with an earlier chronotype (morningness) and higher physical activity.

Diurnal variations of resting-state fMRI data: A graph-based analysis

Circadian rhythms (lasting approximately 24 h) control and entrain various physiological processes, ranging from neural activity and hormone secretion to sleep cycles and eating habits. Several studies have shown that time of day (TOD) is associated with human cognition and brain functions. In this study, utilizing a chronotype-based paradigm, we applied a graph theory approach on resting-state functional MRI (rs-fMRI) data to compare whole-brain functional network topology between morning and evening sessions and between morning-type (MT) and evening-type (ET) participants. Sixty-two individuals (31 MT and 31 ET) underwent two fMRI sessions, approximately 1 hour (morning) and 10 h (evening) after their wake-up time, according to their declared habitual sleep-wake pattern on a regular working day. In the global analysis, the findings revealed the effect of TOD on functional connectivity (FC) patterns, including increased small-worldness, assortativity, and synchronization across the day. However, we identified no significant differences based on chronotype categories. The study of the modular structure of the brain at mesoscale showed that functional networks tended to be more integrated with one another in the evening session than in the morning session. Local/regional changes were affected by both factors (i.e., TOD and chronotype), mostly in areas associated with somatomotor, attention, frontoparietal, and default networks. Furthermore, connectivity and hub analyses revealed that the somatomotor, ventral attention, and visual networks covered the most highly connected areas in the morning and evening sessions: the latter two were more active in the morning sessions, and the first was identified as being more active in the evening. Finally, we performed a correlation analysis to determine whether global and nodal measures were associated with subjective assessments across participants. Collectively, these findings contribute to an increased understanding of diurnal fluctuations in resting brain activity and highlight the role of TOD in future studies on brain function and the design of fMRI experiments.

From dawn to dusk-mimicking natural daylight exposure improves circadian rhythm entrainment in patients with severe brain injury

STUDY OBJECTIVES

While light therapy has proven effective in re-entraining circadian rhythms, the potential of such an intervention has not been evaluated systematically in post-comatose patients with disorders of consciousness (DOC), who often have strongly altered circadian rhythms.

METHODS

We recorded skin temperature over 7-8 days in patients with DOC in each of two conditions: habitual light (HL), and dynamic daylight (DDL) condition. While patients were in a room with usual clinic lighting in the HL condition, they were in an otherwise comparable room with biodynamic lighting (i.e. higher illuminance and dynamic changes in spectral characteristics during the day) in the DDL condition. To detect rhythmicity in the patients' temperature data, we computed Lomb-Scargle periodograms and analyzed normalized power, and peak period. Furthermore, we computed interdaily stability and intradaily variability, which provide information about rhythm entrainment and fragmentation.

RESULTS

We analyzed data from 17 patients with DOC (i.e. unresponsive wakefulness syndrome [n = 15] and minimally conscious state [n = 2]). The period length of the patients' temperature rhythms was closer to 24 h in the DDL as compared to the HL condition (median median deviation from 24 h: DDL = 0.52 h, HL = 3.62 h). Specifically, in 11/17 (65%) patients the period length was closer to 24 h in the DDL condition. Furthermore, the patients' rhythm was more pronounced, more stable, and less variable in the DDL condition.

CONCLUSIONS

Our results indicate that DDL stimulation entrains and stabilizes circadian rhythms. This highlights the importance of adequate room lighting as an adjunct therapeutic approach for improving circadian rhythms in severely brain-injured patients.

TRIAL REGISTRATION INFORMATION

German Clinical Trials Register (DRKS00016041); registration: 18.01.2019; recording start: 04.06.2019 https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00016041.

Bright Light Decreases Peripheral Skin Temperature in Healthy Men: A Forced Desynchrony Study Under Dim and Bright Light (II)

Human thermoregulation is strictly regulated by the preoptic area of the hypothalamus, which is directly influenced by the suprachiasmatic nucleus (SCN). The main input pathway of the SCN is light. Here, thermoregulatory effects of light were assessed in humans in a forced desynchrony (FD) design. The FD experiment was performed in dim light (DL, 6 lux) and bright white light (BL, 1300 lux) in 8 men in a semi-randomized within-subject design. A 4 × 18 h FD protocol (5 h sleep, 13 h wake) was applied, with continuous core body temperature (CBT) and skin temperature measurements at the forehead, clavicles, navel, palms, foot soles and toes. Skin temperature parameters indicated sleep-wake modulations as well as internal clock variations. All distal skin temperature parameters increased during sleep, when CBT decreased. Light significantly affected temperature levels during the wake phase, with decreased temperature measured at the forehead and toes and increased navel and clavicular skin temperatures. These effects persisted when the lights were turned off for sleep. Circadian amplitude of CBT and all skin temperature parameters decreased significantly during BL exposure. Circadian proximal skin temperatures cycled in phase with CBT, while distal skin temperatures cycled in anti-phase, confirming the idea that distal skin regions reflect heat dissipation and proximal regions approximate CBT. In general, we find that increased light intensity exposure may have decreased heat loss in humans, especially at times when the circadian system promotes sleep.

Chronotype at the beginning of secondary school and school timing are both associated with chronotype development during adolescence

The misalignment between late chronotypes and early school start times affect health, performance and psychological well-being of adolescents. Here we test whether, and how, the baseline chronotype (i.e. chronotype at the beginning of secondary school) and the school timing affect the magnitude and the direction of the developmental change in chronotype during adolescence. We evaluated a sample of Argentinian students (n = 259) who were randomly assigned to attend school in the morning (07:45 a.m.–12:05 p.m.), afternoon (12:40 p.m.–05:00 p.m.) or evening (05:20 p.m.–09:40 p.m.) school timings. Importantly, chronotype and sleep habits were assessed longitudinally in the same group of students along secondary school (at 13–14 y.o. and 17–18 y.o.). Our results show that: (1) although chronotypes partially align with class time, this effect is insufficient to fully account for the differences observed in sleep-related variables between school timings; (2) both school timing and baseline chronotype are independently associated with the direction and the magnitude of change in chronotype, with greater delays related to earlier baseline chronotypes and later school timings. The practical implications of these results are challenging and should be considered in the design of future educational timing policies to improve adolescents’ well-being.

Asymmetric effects of acute stress on cost and benefit learning

BACKGROUND

Humans are continuously exposed to stressful challenges in everyday life. Such stressful events trigger a complex physiological reaction - the fight-or-flight response - that can hamper flexible decision-making and learning. Inspired by key neural and peripheral characteristics of the fight-or-flight response, here, we ask whether acute stress changes how humans learn about costs and benefits.

METHODS

Healthy adults were randomly exposed to an acute stress (age mean=23.48, 21/40 female) or no-stress control (age mean=23.80, 22/40 female) condition, after which they completed a reinforcement learning task in which they minimize cost (physical effort) and maximize benefits (monetary rewards). During the task pupillometry data were collected. A computational model of cost-benefit reinforcement learning was employed to investigate the effect of acute stress on cost and benefit learning and decision-making.

RESULTS

Acute stress improved learning to maximize rewards relative to minimizing physical effort (Condition-by-Trial Type interaction: F(1,78)= 6.53, p = 0.01, n²_G= 0.04; reward > effort in stress condition: t(39) = 5.40, p < 0.01). Computational modelling revealed that asymmetric learning could be explained by changes in the learning rates of reward value and action cost [condition-by-learning rate (αR, αE) interaction: F(1,78)= 6.42, p = 0.01, n²_G= 0.03; αE> αR in control condition: t(39) = -4.75, p < 0.001]. This process was associated with distinct alterations in pupil size fluctuations. Data and scripts are available (https://osf.io/ydv2q/).

CONCLUSIONS

Here we demonstrate that acute stress is associated with asymmetric learning about reward value versus action cost, thereby providing new insights into learning strategies under acute stress, which, depending on the context, may be maladaptive or beneficial. Our pupillometry and physiological results tentatively link asymmetric cost and benefit learning to stress-related changes in catecholamine activity.

Chronotype Profile, Stress, Depression Level, and Temporomandibular Symptoms in Students with Type D Personality

Background: Despite a growing interest in the types of human circadian activity, different chronotypes and personality-related issues have been rarely studied. It has already been emphasized that ‘stress personality’ is considered a risk factor for certain psychosomatic diseases and may be a temporomandibular disorders (TMDs) predictor. Therefore, an attempt has been made to analyze the chronotypes, stress levels, stress factors, and the occurrence of depression and TMDs in students with type D personalities. People with this personality trait tend to experience negative emotions more—depression, anxiety, anger, or hostility—yet may have a negative image of themselves and report somatic complaints. Aim: The aim of this study was to analyze the importance of the chronotype profile for the level of stress perceived, as well as for the occurrence of depression and TMDs in people with type D personalities. Material and Methods: The study has been conducted on a group of 220 physical therapy students. The study group G1 consisted of 110 participants with type D personalities, the control group G2 consisted of the same number of participants without the stress personality. All participants have been analyzed for the chronotype (MEQ), stress perception (PSS10), the occurrence of depression (Beck scale-BDI), the occurrence of TMDs symptoms and have completed the stress factor assessment questionnaire during the study, followed by DS14 questionnaire—a tool for assessing the prevalence of type D personality. Results: In students with type D personalities (G1), the definitely evening and evening chronotypes have been significantly more predominant than in the control group (G2). A significantly higher number of stressors and TMDs symptoms have been observed in the respondents from the G1 group than in the control group (<0.001). Univariate logistic regression analysis showed that type D personality was strongly associated with a more frequent occurrence of all TMD symptoms. Additionally, a significant influence of the evening chronotype on the occurrence of type D personality was observed. Among the potential confounding variables, female gender and a mild and moderate degree of depression have an impact on the occurrence of type D personality (p < 0.05). In the multivariate model, adjusted with the above-mentioned factors, an increased risk of the type D personality trait was found. Conclusion: The evening chronotype and type D personality may imply greater feelings of stress, greater depression, and more frequent symptoms of TMDs in young adults.

Acute Effects of Esports on the Cardiovascular System and Energy Expenditure in Amateur Esports Players

Introduction

Esports is practiced by millions of people worldwide every day. On a professional level, esports has been proven to have a high stress potential and is sometimes considered equivalent to traditional sporting activities. While traditional sports have health-promoting effects through muscle activity and increased energy expenditure, amateur esports could represent a purely sedentary activity, which would carry potentially harmful effects when practiced regularly. Therefore, this study aims to investigate the acute effects of esports on the cardiovascular system and energy expenditure in amateur esports players to show whether esports can be considered as physical strain or mental stress or whether amateur esports has to be seen as purely sedentary behavior.

Methods

Thirty male subjects participated in a 30-min gaming session, playing the soccer simulation game FIFA 20 or the tactical, first-person multiplayer shooter Counter-Strike: Global Offensive. Respiratory and cardiovascular parameters, as well as energy expenditure, blood glucose, lactate, and cortisol, were determined pre-, during, and post-gaming.

Results

There were no significant changes in oxygen uptake, carbon dioxide output, energy expenditure, stroke volume, or lactate levels. Heart rate, blood glucose and cortisol decreased through the intervention until reaching their minimum levels 10 min post-gaming (Cortisolpre: 3.1 ± 2.9 ng/ml, Cortisolpost: 2.2 ± 2.3 ng/ml, p &lt; 0.01; HRmin0.5: 82 ± 11 bpm, HRpost: 74 ± 13 bpm, p &lt; 0.01).

Conclusion

A 30-min esports intervention does not positively affect energy expenditure or metabolism in amateur esports players. Therefore, it cannot provide the same health-promoting effects as traditional sports participation, but could in the long-term rather cause the same potentially health-damaging effects as purely sedentary behavior. However, it does not trigger a negative stress response in the players. Deliberate physical activity and exercise routines adapted to these demands should therefore be part of the daily life of amateur esports players.

What Can Make the Difference Between Chronotypes in Sleep Duration? Testing the Similarity of Their Homeostatic Processes

The two-process conceptualization of sleep-wake regulation suggests that the biological underpinnings of the differences between morning and evening types in sleep timing and duration might be related to either the circadian process or the homeostatic process or both. The purpose of this report was to test whether morning and evening types might have similar homeostatic processes to achieve such ultimate goal of homeostatic sleep regulation as taking an adequate amount of sleep on free days. Weekend and weekday rise- and bedtimes reported for 50 paired samples of morning and evening types were averaged and simulated with a model of sleep-wake regulation. In morning and evening types of the same age, the homeostatic components of the sleep-wake regulation were found to be identical. Therefore, the difference in the circadian process between chronotypes of similar age can account for the observed differences between them in sleep timing and duration on weekdays and weekends. It was also demonstrated that the model-based simulations might have practical implications for informing an individual about the extent of unrecoverable reduction of his/her sleep on weekdays.

Circadian clocks and their role in lactation competence

Circadian rhythms are 24 h cycles of behavior, physiology and gene expression that function to synchronize processes across the body and coordinate physiology with the external environment. Circadian clocks are central to maintaining homeostasis and regulating coordinated changes in physiology in response to internal and external cues. Orchestrated changes occur in maternal physiology during the periparturient period to support the growth of the fetus and the energetic and nutritional demands of lactation. Discoveries in our lab made over a decade ago led us to hypothesize that the circadian timing system functions to regulate metabolic and mammary specific changes that occur to support a successful lactation. Findings of studies that ensued are summarized, and point to the importance of circadian clocks in the regulation of lactation competence. Disruption of the circadian timing system can negatively affect mammary gland development and differentiation, alter maternal metabolism and impair milk production.

Infrared Thermography for Measuring Elevated Body Temperature: Clinical Accuracy, Calibration, and Evaluation

Infrared thermographs (IRTs) implemented according to standardized best practices have shown strong potential for detecting elevated body temperatures (EBT), which may be useful in clinical settings and during infectious disease epidemics. However, optimal IRT calibration methods have not been established and the clinical performance of these devices relative to the more common non-contact infrared thermometers (NCITs) remains unclear. In addition to confirming the findings of our preliminary analysis of clinical study results, the primary intent of this study was to compare methods for IRT calibration and identify best practices for assessing the performance of IRTs intended to detect EBT. A key secondary aim was to compare IRT clinical accuracy to that of NCITs. We performed a clinical thermographic imaging study of more than 1000 subjects, acquiring temperature data from several facial locations that, along with reference oral temperatures, were used to calibrate two IRT systems based on seven different regression methods. Oral temperatures imputed from facial data were used to evaluate IRT clinical accuracy based on metrics such as clinical bias (Δcb), repeatability, root-mean-square difference, and sensitivity/specificity. We proposed several calibration approaches designed to account for the non-uniform data density across the temperature range and a constant offset approach tended to show better ability to detect EBT. As in our prior study, inner canthi or full-face maximum temperatures provided the highest clinical accuracy. With an optimal calibration approach, these methods achieved a Δcb between ±0.03 °C with standard deviation (σΔcb) less than 0.3 °C, and sensitivity/specificity between 84% and 94%. Results of forehead-center measurements with NCITs or IRTs indicated reduced performance. An analysis of the complete clinical data set confirms the essential findings of our preliminary evaluation, with minor differences. Our findings provide novel insights into methods and metrics for the clinical accuracy assessment of IRTs. Furthermore, our results indicate that calibration approaches providing the highest clinical accuracy in the 37-38.5 °C range may be most effective for measuring EBT. While device performance depends on many factors, IRTs can provide superior performance to NCITs.

Player Chronotype Does Not Affect In-Game Performance during the Evening (>18:00 h) in Professional Male Basketball Players

Sport-specific skills display diurnal variation across various team sports such as badminton and tennis serving accuracy and soccer dribbling, volleying, and chipping execution. However, the effects of athlete chronotype on in-game sport-specific skill performance according to time of day across team sports is not well understood. Therefore, the aim of this study was to identify the effect of player chronotype on in-game basketball performance during evening games. Professional male basketball players (n = 11) completed a morningness-eveningness questionnaire and were categorized according to chronotype (morning-type: n = 4; neither-type: n = 6; evening-type: n = 1). Box score data from the 2019/20 season were utilized to determine individual in-game performance during evening games played after 18:00 h. Composite metrics (i.e., effective field goal percentage, offensive rating, defensive rating, and player efficiency) were used as indicators of player performance. Non-significant (p ≥ 0.21) differences were evident between M-types and N-types for most performance measures. Small to very large effects were observed in the number of rebounds favoring M-types, and three-point shots attempted and made, assists, and steals favored N-types. In-game performance appeared to not be affected by chronotype (i.e., M-type vs. N-type) in evening games among professional male basketball players. The lack of observed effect between chronotype and in-game performance suggest coaching staff may not need to consider player chronotype when developing a match strategy or assigning player roles if largely dealing with M-types and N-types. However, to ensure the greatest specificity, coaching staff may endeavor to schedule habitual training times in line with that of competition in an effort to align player circadian rhythms to games.

Metabolic health measurements of shift workers in a national cross-sectional study: Results from the Canadian Health Measures Survey

BACKGROUND

Shift work exposure may be a concern for a range of health effects, including metabolic health outcomes such as insulin resistance, high body weight, and abdominal obesity.

METHODS

We analyzed shift work and indicators of metabolic health (overweight/obesity defined by body mass index, self-reported changes in body mass index (BMI) in previous 1 and 10 years, waist circumference, waist-to-hip ratio, and insulin resistance assessed by the homeostasis model assessment 2 (HOMA-2-IR)) in the cross-sectional Canadian Health Measures Survey (CHMS). We analyzed descriptive characteristics of shift workers (regular night, evening, and rotating shift) and used multivariable linear regression to examine the association between two definitions of shift work exposure and measures of metabolic health, adjusted for age, sex, daily energy expenditure, sleep, and poor dietary quality.

RESULTS

5470 anthropometry (2637 fasting) participants in CHMS Cycles 1 and 2 were included, of whom 16.5% worked regular evening, night, or rotating shifts. Shift workers were younger and slept longer hours than non-shift workers. Bivariate associations showed inverse relationships between shift work and BMI, waist circumference, waist-to-hip ratio, and HOMA-2-IR. In adjusted analyses, BMI was inversely related to shift work, and other metabolic health outcomes showed no significant associations.

CONCLUSIONS

Healthy worker effects (including self-selection of exposure) could explain inverse relationships, particularly as the cross-sectional design only allowed assessment of current exposure. Key strengths include the population-based design and measurement of metabolic health indicators. Results underscore the importance of consideration of the health of shift workers following departure from the exposed population.

Chronotype in individuals with schizophrenia: A meta-analysis

OBJECTIVE

Emerging evidence shows that evening chronotype is associated with mental health problems, especially mood disorders, but few studies have investigated its association with schizophrenia. Based on meta-analytic methods, we aimed to test whether eveningness is greater in individuals with schizophrenia compared with healthy controls and patients with bipolar I disorder.

METHOD

Medline/Pubmed, Google Scholar, and EBSCO databases were searched up to April 2021 for articles investigating chronotype in individuals with schizophrenia. Two meta-analyses were conducted: individuals with schizophrenia compared with healthy controls and individuals with bipolar I disorder. These meta-analyses were followed by a meta-regression controlling for potential confounders.

RESULTS

Five studies comprising 386 individuals with schizophrenia (age 32.73 years; 67.4% male), 320 with bipolar I disorder (age 31.26 years; 38.3% male) and 638 healthy controls (age 32.19 years; 50.6% male) were included. Participants with schizophrenia were moderately higher on eveningness than healthy controls but they did not differ from those with bipolar I disorder. The difference was not affected by gender, age, and the type of scale used for assessing chronotype.

CONCLUSIONS

Individuals with schizophrenia are more evening oriented than healthy controls and have a similar chronotype to those with bipolar I disorder. The results supported the hypothesis that evening chronotype might be a marker of, or a risk factor for, mental health problems in general and not just limited to affective disorders.

Diurnal and seasonal differences in cardiopulmonary response to exercise in morning and evening chronotypes

Circadian clocks regulate multiple physiological domains from molecular to behavioral levels and adjust bodily physiology to seasonal changes in day length. Circadian regulation of cellular bioenergy and immunity in the cardiovascular and muscle systems may underpin the individual diurnal differences in performance capacity during exercise. Several studies have shown diurnal differences in cardiopulmonary parameters at maximal and submaximal workloads in morning and evening circadian human phenotypes. However, the effect of seasons on these changes was not elucidated. In this study, we recruited subjects with Morningness-Eveningness Questionnaire scores corresponding to morning and evening types. Subjects underwent morning (7:00-9:00) and evening (20:00-22:00) maximal workload spiroergometry in both winter and summer seasons. We analyzed their performance time, anaerobic threshold, heart rate, and respiratory parameters. Our results suggest that evening types manifest diurnal variations in physical performance, particularly in winter. They also have slower heart rate recovery than morning types, irrespective of the time of day or season. Compared to winter, the chronotype effect on the magnitude of morning-evening differences in performance time, maximal heart rate, and anaerobic threshold onset was more significant in summer. Our data are in concordance with previous observations and confirm the difference between morning and evening types in the timing of maximum performance capacity.

Differential effects of COVID-19 lockdowns on well-being: interaction between age, gender and chronotype

The unprecedented restrictions imposed due to the COVID-19 pandemic altered our daily habits and severely affected our well-being and physiology. The effect of these changes is yet to be fully understood. Here, we analysed highly detailed data on 169 participants for two to six months, before and during the second COVID-19 lockdown in Israel. We extracted 12 well-being indicators from sensory data of smartwatches and from self-reported questionnaires, filled daily using a designated mobile application. We found that, in general, lockdowns resulted in significant changes in mood, sleep duration, sport duration, social encounters, resting heart rate and number of steps. Examining subpopulations, we found that younger participants (aged 20-40 years) suffered from a greater decline in mood and number of steps than older participants (aged 60-80 years). Likewise, women suffered from a higher increase in stress and reduction in social encounters than men. Younger early chronotypes did not increase their sleep duration and exhibited the highest drop in mood. Our findings underscore that while lockdowns severely impacted our well-being and physiology in general, greater damage has been identified in certain subpopulations. Accordingly, special attention should be given to younger people, who are usually not in the focus of social support, and to women.

The relationship between house height and mosquito house entry: an experimental study in rural Gambia

Most malaria infections in sub-Saharan Africa are acquired indoors, thus finding effective ways of preventing mosquito house entry should reduce transmission. Since most malaria mosquitoes fly less than 1 m from the ground, we tested whether raising buildings off the ground would prevent the entry of Anopheles gambiae, the principal African malaria vector, in rural Gambia. Nightly collections of mosquitoes were made using light traps from four inhabited experimental huts, each of which could be moved up or down. Mosquito house entry declined with increasing height, with a hut at 3 m reducing An. gambiae house entry by 84% when compared with huts on the ground. A propensity for malaria vectors to fly close to the ground and reduced levels of carbon dioxide, a major mosquito attractant, in elevated huts, may explain our findings. Raised buildings may help reduce malaria transmission in Africa.

Evening Chronotype Is Associated with Poorer Habitual Diet in US Women, with Dietary Energy Density Mediating a Relation of Chronotype with Cardiovascular Health

BACKGROUND

An innate preference for later timing of sleep and activity, termed evening chronotype, is linked to poorer cardiovascular health (CVH). However, associations of chronotype with specific health behaviors in US women are not well characterized. Of particular interest is habitual diet, because <1% of US adults meet recommendations for a healthful diet.

OBJECTIVES

We aimed to evaluate cross-sectional and prospective associations of chronotype with diet quantity and quality in US women, and to assess whether dietary energy density (ED), a robust predictor of cardiometabolic outcomes, mediates an established chronotype-CVH relation.

METHODS

Data were collected from participants in the AHA Go Red for Women Strategically Focused Research Network cohort (aged 20-76 y; 61% racial/ethnic minority) at baseline (n = 487) and 1-y follow-up (n = 432). Chronotype (evening compared with morning/intermediate) and habitual diet were ascertained from the Morningness-Eveningness Questionnaire and an FFQ, respectively. Multivariable-adjusted linear regression models evaluated cross-sectional and prospective associations of chronotype with diet. Causal mediation analyses assessed whether dietary ED mediated a relation between chronotype and CVH, quantified using AHA Life's Simple 7 score, derived from clinical measurements and validated assessments of CVH components.

RESULTS

Evening compared with morning/intermediate chronotype was associated with poorer diet quality, including lower intakes of plant protein (cross-sectional: β = -0.63 ± 0.24, P < 0.01; prospective: β = -0.62 ± 0.26, P = 0.01), fiber (cross-sectional: β = -2.19 ± 0.65, P < 0.001; prospective: β = -2.39 ± 0.66, P < 0.001), and fruits and vegetables (cross-sectional: β = -1.24 ± 0.33, P < 0.001; prospective: β = -1.15 ± 0.36, P = 0.001). Evening chronotype was also associated with higher dietary ED at baseline (β = 0.20 ± 0.05, P = 0.001) and 1 y (β = 0.19 ± 0.06, P = 0.001). Dietary ED was a partial mediator of the association between evening chronotype and poorer CVH (24.6 ± 9.1%, P < 0.01).

CONCLUSIONS

Evening chronotype could contribute to unhealthful dietary patterns in US women, with higher dietary ED partially mediating the relation between eveningness and poorer CVH. Behavioral interventions to reduce dietary ED might mitigate cardiovascular disease risk in women with evening chronotype.

Does the chronotype distribution vary between different level football leagues? Insights gained from Czech elite football players

Chronotype refer to individuals' time-of-day preferences for activities, which can be classified as "morning types = (M-types)", "evening types = (E-types)", and "neither types (N-types)". The primary aim of this study was to compare the chronotype distribution of Czech First League (1L) and Czech National Football League (2L) male elite football players, which was divided into two secondary aims: (i) statistically identify and compare the number (presence) of particular chronotypes in 1L, and (ii) statistically identify and compare the number (presence) of particular chronotypes in 2L. The present cross-sectional study employed a self-reported standardized questionnaire, the Composite Scale of Morningness, to study the chronotype distribution among the male elite football players. The chronotype distribution of 139 (85 from 1L with mean age ± S.D. = 25.5 ± 3.7 years and 54 from 2L age = 24.4 ± 4.5 years) players was assessed. Overall, 61 (71.8%) of the participants from 1L were mainly N-types, followed by M- and E-types. Similarly, 40 (74.1%) participants from 2L were mainly N-types, followed by M- and E-types. The statistical analysis of the 1L players showed a significantly higher presence of N-types compared to M- and E-types (χ²₍₂₎ = 57.62, p < .05, V = .58). The same results were detected in 2L, where the N-type was identified in the majority of football players (χ²₍₂₎ = 57.62, p < .05, V = .58). The statistical comparison of the number of presented chronotypes did not show a significant difference (F = 3.29, p > .05, V = .16) between players of the 1L and 2L. Thus, N-types are dominant among Czech elite football players, and the chronotype distribution of male elite football players from the Czech First League and the Czech National Football League does not vary.

Biological Rhythm and Chronotype: New Perspectives in Health

The circadian rhythm plays a fundamental role in regulating biological functions, including sleep–wake preference, body temperature, hormonal secretion, food intake, and cognitive and physical performance. Alterations in circadian rhythm can lead to chronic disease and impaired sleep. The circadian rhythmicity in human beings is represented by a complex phenotype. Indeed, over a 24-h period, a person’s preferred time to be more active or to sleep can be expressed in the concept of morningness–eveningness. Three chronotypes are distinguished: Morning, Neither, and Evening-types. Interindividual differences in chronotypes need to be considered to reduce the negative effects of circadian disruptions on health. In the present review, we examine the bi-directional influences of the rest–activity circadian rhythm and sleep–wake cycle in chronic pathologies and disorders. We analyze the concept and the main characteristics of the three chronotypes.