Extreme Morning Research Articles

CHRONOBIOLOGICAL ASPECTS OF SLEEP DISORDERS UNDER ANXIETY DISORDERS

Modern research highlights the connection between the deterioration of sleep quality, sleep efficiency and daytime sleepiness with the disruption of the sleep-wake pattern due to circadian dysfunction. The aim of the study is to investigate the features of sleep disorders in patients with anxiety disorders of neurotic genesis, taking into account individual chronotype.
 91 patients, 48 women (52,7%) and 43 men (47,3%) with anxiety disorders of neurotic origin were examined at Regional Center of Psychiatric Care. The Horn-Ostberg Morningness-Eveningness Questionnaire was used to determine the chronotype of participants. The study was also conducted using the Hamilton anxiety scale, Pittsburgh sleep quality questionnaire, Insomnia severity index, Epworth sleepiness scale, and Fatigue severity scale. All patients, depending on the individual chronotype, were divided into 3 groups, representative by age and gender. The morning type group comprised 32 patients (35.2%), the intermediate type group consisted of 31 patients (34.1%), and the evening type group included 28 patients (30.7%).
 A significant difference has been established between groups of morning and evening type in terms of the total score of anxiety and its somatic component (p<0.05). There is no difference in the indicator of the mental component of anxiety. However, this indicator is higher in people with extreme evening type compared to extreme morning type (p=0.001). Differences in indicators of sleep disturbances have been found to depend on the individual chronotype. Representatives of the evening type compared to the intermediate and morning types have significantly higher indicators of sleep latency and daytime dysfunction according to PSQI, as well as daytime sleepiness and fatigue severity (p<0.001). People with an intermediate chronotype have better sleep duration (p<0.05) and lower insomnia severity index than people with a morning (p<0.05) and evening type (p<0.01).

Extreme morning sickness? Scientists finally pinpoint a possible cause

Extreme morning sickness? Scientists finally pinpoint a possible cause

Eveningness is associated with coronary artery calcification in a middle-aged Swedish population

Coronary artery calcification (CAC) is an established imaging biomarker of subclinical atherosclerosis, but its relationship to diurnal preference is not well studied. We investigated the association between chronotype and CAC in the Swedish CArdioPulmonary bioImage Study (SCAPIS) pilot cohort. Participants aged 50–64 years were randomly recruited and underwent extensive examination including imaging and accelerometry-assessed physical activity. 771 participants (47.3 % male, 57.6 ± 4.4 years) were included in this cross-sectional analysis. CAC was assessed by non-contrast computed tomography, and a CAC score > 10 was considered significant calcification. Self-assessed chronotype was classified as extreme morning, moderate morning, intermediate, moderate evening, or extreme evening. 10-year risk of first-onset cardiovascular disease was estimated by the Systemic Coronary Risk Evaluation 2 (SCORE2). Significant CAC was present in 29 % of the cohort. CAC prevalence increased from extreme morning to extreme evening type (22 %, 28 %, 29 %, 27 %, 41 % respectively, p = 0.018). In a multivariate logistic regression model controlling for confounders, extreme evening chronotype was independently associated with increased CAC prevalence compared to extreme morning type (OR 1.90, [95%CI 1.04–3.46], p = 0.037). When stratified by SCORE2 risk category (low: <5 %; moderate: 5 to <10 %; high: ≥10 %), significant CAC was most prevalent among extreme evening chronotypes in the low and moderate-risk groups, while chronotype seemed less important in the high-risk group (p = 0.011, p = 0.023, p = 0.86, respectively). Our findings suggest circadian factors may play an important role in atherosclerosis and should be considered in early cardiovascular prevention.

Effects of Chronotype and Social Jet-Lag on Neurocognitive Functioning

The chronotype, which reflects the circadian rhythm preferences of individuals in their daily activities and sleep-wake cycles, can be considered on a dimension of extreme morningism and extreme eveningism. Individuals with extreme morning and extreme evening chronotypes face many physical and psychological dangers due to accumulated sleep debt, short total sleep time and insufficient sleep efficiency. In extreme chronotypes, especially in extreme evening people, the social jet-lag effect due to the mismatch between social and circadian clocks is thought to exacerbate these dangers. More recent studies have suggested that social jet-lag and chronotype have many negative effects on cognitive functioning. The aim of this article is to review the impact of social jet-lag and chronotype on cognitive functioning.

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.

What Is the Difference between the Nature Eating Rhythm and the Actual Eating Behaviors in Malaysian Adults? A Cross-Sectional Study of Circadian Misalignment

ObjectivesEating behavior different from the natural eating rhythm increases the risk of metabolic syndrome. With simply adjusted eating behaviors to line up with the natural rhythms, it prevents the further development of metabolic disorder. To fill the gap in nutritional therapy in metabolic syndrome, this study aimed to determine the contrast between natural eating rhythm and actual eating behaviors in Malaysians.MethodsThe cross-sectional comprised of a total of 221 participants aged 20 to 63 years old, who completed online survey to collect their sociodemographic characteristics, eating rhythm, sleep patterns and eating behaviors. A validated chrononutrition questionnaire was used as indicator of eating rhythm and practices. Descriptive data showed the mean and standard deviation of the natural eating rhythm and actual eating behaviors in table, while the misalignment of chrononutrition was reported as frequencies on graph.ResultsThe majority of participants were female (67.0%) and graduated from university (76.5%). They were non-alcohol drinkers (96.8%) or had no smoking history (71.5%). Although the mean for the natural eating rhythm was 08:02 ± 01:26, participants tend to start their first eating occasion during free days (09:11 ± 01:26) later than during work or school days (08:08 ± 00:05). The overall mean eating occasion before bedtime was 23:30 ± 01:54, there were no difference between eating occasion before bedtime during work or school days (19:50 ± 01:10) and free days (19:59 ± 01:20). This study found that 17.6% and 13.1% of the participants had extreme morning latency misalignment during work or school days, and free days respectively. Approximately half of the participants had extreme evening latency misalignment during work or school days and free days, with 35.8% and 48.8% separately. A total mean of 701.48 ± 104.69 minutes spent eating window during work or school days and 646.67 ± 115.71 minutes used during free days.ConclusionsMalaysian adults had differed between their natural eating rhythm and actual eating practices. The results suggested to review circadian misalignment, typically eating behaviors in metabolic regulation in future studies.Funding SourcesThe researchers appreciated the Ministry of Higher Education of Malaysia for providing a support under the Fundamental Research Grant Scheme (FRGS/1/2021/SKK06/TARUC/02/1).

Eveningness is associated with sedentary behavior and increased 10-year risk of cardiovascular disease: the SCAPIS pilot cohort

Chronotype reflects individual preferences for timing activities throughout the day, determined by the circadian system, environment and behavior. The relationship between chronotype, physical activity, and cardiovascular health has not been established. We studied the association between chronotype, physical activity patterns, and an estimated 10-year risk of first-onset cardiovascular disease (CVD) in the Swedish CArdioPulmonary bioImage Study (SCAPIS) pilot cohort. A cross-sectional analysis was performed in a middle-aged population (n = 812, 48% male). Self-assessed chronotype was classified as extreme morning, moderate morning, intermediate, moderate evening, or extreme evening. Time spent sedentary (SED) and in moderate to vigorous physical activity (MVPA) were derived from hip accelerometer. The newly introduced Systematic COronary Risk Evaluation 2 (SCORE2) model was used to estimate CVD risk based on gender, age, smoking status, systolic blood pressure, and non-HDL cholesterol. Extreme evening chronotypes exhibited the most sedentary lifestyle and least MVPA (55.3 ± 10.2 and 5.3 ± 2.9% of wear-time, respectively), with a dose-dependent relationship between chronotype and SED/MVPA (p < 0.001 and p = 0.001, respectively). In a multivariate generalized linear regression model, extreme evening chronotype was associated with increased SCORE2 risk compared to extreme morning type independent of confounders (β = 0.45, SE = 0.21, p = 0.031). Mediation analysis indicated SED was a significant mediator of the relationship between chronotype and SCORE2. Evening chronotype is associated with unhealthier physical activity patterns and poorer cardiovascular health compared to morning chronotype. Chronotype should be considered in lifestyle counseling and primary prevention programs as a potential modifiable risk factor.

Evening chronotype is associated with elevated biomarkers of cardiometabolic risk in the EpiHealth cohort: a cross-sectional study.

Study ObjectivesIndividuals with evening chronotype have a higher risk of cardiovascular and metabolic disorders, although the underlying mechanisms are not well understood. In a population-based cohort, we aimed to investigate the association between chronotype and 242 circulating proteins from three panels of established or candidate biomarkers of cardiometabolic processes.MethodsIn 2,471 participants (49.7% men, mean age 61.2 ± 8.4 SD years) from the EpiHealth cohort, circulating proteins were analyzed with a multiplex proximity extension technique. Participants self-reported their chronotype on a five-level scale from extreme morning to extreme evening chronotype. With the intermediate chronotype set as the reference, each protein was added as the dependent variable in a series of linear regression models adjusted for confounders. Next, the chronotype coefficients were jointly tested and the resulting p-values adjusted for multiple testing using a false discovery rate (5%). For the associations identified, we then analyzed the marginal effect of each chronotype category.ResultsWe identified 17 proteins associated with chronotype. Evening chronotype was positively associated with proteins previously linked to insulin resistance and cardiovascular risk, namely retinoic acid receptor protein 2, fatty acid-binding protein adipocyte, tissue-type plasminogen activator, and plasminogen activator inhibitor 1 (PAI-1). Additionally, PAI-1 was inversely associated with the extreme morning chronotype.ConclusionsIn this population-based study, proteins previously related to cardiometabolic risk were elevated in the evening chronotypes. These results may guide future research in the relation between chronotype and cardiometabolic disorders.

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

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

The influence of light exposure and chronotype on working memory in humans

Here we examine how exposure to blue (peaking at λ=470 nm), green (peaking at λ=505 nm) and red (peaking at λ=630 nm) light affects subsequent working memory performance measured with visual N-back tasks and associated functional brain responses in participants with extreme morning and extreme evening chronotype. We used within-subjects experimental manipulation on carefully selected samples and state of the art equipment for light exposure. The results show no differences between extreme morning-type and evening-type individuals in N-back task performance. We also did not replicate the alerting effect of exposure to blue wavelength light, supposedly enhancing performance on cognitive tasks. However, we found higher brain activity in the morning hours for extreme morning in comparison to extreme evening chronotype in several frontal areas of the precentral gyrus, middle and superior frontal gyri and in the occipital gyrus. This may indicate increased strategic or attentional recruitment of prefrontal areas, implicated in compensating working memory load in the morning type.

İyi Antrenmanlı Yarı-profesyonel Futbolcuların Koşuya Dayalı Anaerobik Sprint Test Performansında Diurnal Varyasyonlar

Objective: This study examined whether there were diurnal variations in the running-based anaerobic sprint test (RAST) performance of semi-professional, male soccer players. Material and Methods: Participants included 25 people whose ages ranged from 18- 36 years old, (mean=20 years); weight ranged from 52-110 kg (mean=72 kg); mean height was 176.92±6.17 cm; experience playing soccer ranged from 5-22 years (mean=8 years); and average weekly training duration was 3-22 h (mean=6 h). Chronotypes were estimated using the Turkish version of the Horn-Östberg Morningness-Eveningness Personality Questionnaire. They performed RAST in a randomized study design using the Newtest Powertimer 300-series photocells twice, on two separate days, one week apart, either in the morning (8.30-10.00 AM) or afternoon (5.00-6.00 PM). Before each of test session; the air temperature and humidity; along with their oral body temperature and 24 h food intake data were recorded. Resultsː Paired t-tests were used to analyze differences due to the time of day in the RAST variables. Maximum power (p>0.05), minimum power (p>0.05), mean power (p>0.05), fatigue index (p>0.05), air temperature (p>0.05), body temperature, and caloric intake (p>0.05) did not differ in the morning and afternoon. Conclusion: In contrast to previous research, RAST performance showed no diurnal variations. A possible explanation could be attributed to the participants' chronotypes conforming to neither the morning nor evening types. However, replicating this study with soccer players having an extreme morning or extreme evening chronotypes may lead to different results.

The effect of chronotype and time of assessment on cognitive performance

ABSTRACT Standard cognitive measures are often applied at various times of the day to assess cognitive deficits in patients with neuropsychiatric and neurodegenerative disorders, irrespective of their chronotype. In this study, we aimed to determine whether the subjectively nonpreferred time of an assessment might be a crucial factor in persons with extreme chronotypes. We compared morning (08:00) and evening (20:00) cognitive performance in extreme morning, extreme evening, and intermediate chronotypes determined by the Morningness-Eveningness Questionnaire, supported by actigraphy and peripheral temperature measurement. The assessment sessions were performed in pseudorandom order over two consecutive weekend days. We administered the commonly used test battery for neurocognitive assessment comprised of tasks aimed mainly at attention, processing speed, working memory, and declarative memory. The time of assessment influenced the declarative memory measures, whereas the chronotype-specific differences occurred only in the Stroop colour-naming subtest aimed at processing speed. The observed effects should be considered in routine clinical practice because they might cause misrepresentation of the results obtained during improperly timed cognitive assessment. Our results also point towards similarity of doves and owls in contrast to larks in cognitive performance, suggesting that early morning assessments should also be considered in cases of intermediate chronotypes.

Beyond the Low Frequency Fluctuations: Morning and Evening Differences in Human Brain.

Human performance, alertness, and most biological functions express rhythmic fluctuations across a 24-h-period. This phenomenon is believed to originate from differences in both circadian and homeostatic sleep-wake regulatory processes. Interactions between these processes result in time-of-day modulations of behavioral performance as well as brain activity patterns. Although the basic mechanism of the 24-h clock is conserved across evolution, there are interindividual differences in the timing of sleep-wake cycles, subjective alertness and functioning throughout the day. The study of circadian typology differences has increased during the last few years, especially research on extreme chronotypes, which provide a unique way to investigate the effects of sleep-wake regulation on cerebral mechanisms. Using functional magnetic resonance imaging (fMRI), we assessed the influence of chronotype and time-of-day on resting-state functional connectivity. Twenty-nine extreme morning- and 34 evening-type participants underwent two fMRI sessions: about 1 h after wake-up time (morning) and about 10 h after wake-up time (evening), scheduled according to their declared habitual sleep-wake pattern on a regular working day. Analysis of obtained neuroimaging data disclosed only an effect of time of day on resting-state functional connectivity; there were different patterns of functional connectivity between morning (MS) and evening (ES) sessions. The results of our study showed no differences between extreme morning-type and evening-type individuals. We demonstrate that circadian and homeostatic influences on the resting-state functional connectivity have a universal character, unaffected by circadian typology.

Extreme morning chronotypes are often familial and not exceedingly rare: the estimated prevalence of advanced sleep phase, familial advanced sleep phase, and advanced sleep-wake phase disorder in a sleep clinic population.

Report the first prevalence estimates of advanced sleep phase (ASP), familial advanced sleep phase (FASP), and advanced sleep-wake phase disorder (ASWPD). This can guide clinicians on the utility of screening for extreme chronotypes both for clinical decision-making and to flag prospective participants in the study of the genetics and biology of FASP. Data on morning or evening sleep schedule preference (chronotype) were collected from 2422 new patients presenting to a North American sleep center over 9.8 years. FASP was determined using a severity criterion that has previously identified dominant circadian mutations in humans. All patients were personally seen and evaluated by one of the authors (C.R.J.). Our results demonstrate an ASP prevalence of 0.33%, an FASP prevalence of 0.21%, and an ASWPD prevalence of at least 0.04%. Most cases of young-onset ASP were familial. Among patients presenting to a sleep clinic, conservatively 1 out of every 300 patients will have ASP, 1 out of every 475 will have FASP, and 1 out of every 2500 will have ASWPD. This supports obtaining a routine circadian history and, for those with extreme chronotypes, obtaining a family history of circadian preference. This can optimize treatment for evening sleepiness and early morning awakening and lead to additional circadian gene discovery. We hope these findings will lead to improved treatment options for a wide range of sleep and medical disorders in the future.

Bimodal chronotype in night-shift workers

Introduction. Typology of diurnal (circadian) human rhythms is actively studied in occupational medicine, from the viewpoint of adaptation to various work conditions including those with shift working schedule. In recent years, evidences outline bimodal chronotype characterized by simultaneously present signs of extreme morning and extreme evening types without dominating one of them. Studies did not cover bimodal chronotype in night-shift workers.Objective is to evaluate presence of bimodal chronotype in night-shift workers if compared to day-shift schedule.Materials and methods. Chronotype outlining covered 95 workers divided into 2 groups: first — 55 night-shift workers, second — 40 workers on day schedule. Bimodal chronotype was diagnosed via algorithm based on questionnaire Morningness Eveningness Questionnaire (MEQ) by B.J. Martynhak et al.Results. Findings are that 7.3% of night-shift workers and 5.0% of workers with day schedule demonstrate bimodal chronotype. Changed chronotype classification leads to smaller share of workers with intermediate chronotype, but quota of morning and evening chronotypes does not change. Possibility of bimodal chronotype should be respected in examination of workers for designing health programs with consideration of chronotype-associated diseases and for better performance due to rational management of working time.Conclusions. Diagnosis of individual chronotype is a serious part in health programs formation in able-bodied population. Chronotype knowledge helps to minimize possible decrease and losses of performance due to rational working time management and preventive programs aimed to diagnose chronotype-associated health disorders.

Sleep and headaches: Relationships between migraine and non‐migraine headaches and sleep duration, sleep quality, chronotype, and obstructive sleep apnoea risk

ObjectivesPrimary headache disorders affect a large proportion of the world's population, and sleep factors have been increasingly implicated in their aetiology. This study aimed to assess the relationships between a number of sleep factors, sleep duration, sleep quality, and chronotype, and migraine and non‐migraine headache. The approach was multifaceted which included assessing correlations with headache frequency, mediation effects of headache triggers, and diagnostic prediction modelling.MethodA total of 378 participants retained in the dataset (85.2% female) completed a battery of online self‐report tests measuring headache diagnosis and triggers, sleep factors, psychological distress, and demographic factors.ResultsPoor sleep quality was the strongest correlate of both migraine and non‐migraine headache. Poor sleep quality also was found to mediate the effect of sensitivity to headaches triggered by lack of sleep, in the order of 10% of the effect. The predictive modelling showed that morning chronotype was a significant predictor of chronic migraine, and that evening chronotype and anxiety significantly predicted chronic non‐migraine headache diagnosis.ConclusionsThe results indicate the importance of sleep quality in the headache relationship, and how it may impact on headaches triggered by other sleep factors, namely, lack of sleep. Further investigation into the role of chronotype in headache aetiology is needed, particularly, based on two theories. The first being the Trigger Avoidance Model of Headaches, and the second being a stress‐based model related to social and occupational incompatibilities with the rhythms of more extreme morning or evening chronotypes.

Diurnal variations of hormonal secretion, alertness and cognition in extreme chronotypes under different lighting conditions

Circadian rhythms in physiology and behavior are modulated by external factors such as light or temperature. We studied whether self-selected office lighting during the habitual waking period had a different impact on alertness, cognitive performance and hormonal secretion in extreme morning and evening chronotypes (N = 32), whose preferred bed- and wake-up times differed by several hours. The self-selected lighting condition was compared with constant bright light and a control condition in dim light. Saliva samples for hormonal analyses, subjective ratings of alertness, wellbeing, visual comfort and cognitive performance were regularly collected. Between the self-selected and the bright, but not the dim lighting condition, the onset of melatonin secretion in the evening (as marker for circadian phase) was significantly different for both chronotypes. Morning chronotypes reported a faster increase in sleepiness during the day than evening chronotypes, which was associated with higher cortisol secretion. Wellbeing, mood and performance in more difficult cognitive tasks were better in bright and self-selected lighting than in dim light for both chronotypes, whereas visual comfort was best in the self-selected lighting. To conclude, self-selection of lighting at work might positively influence biological and cognitive functions, and allow for inter-individual differences.

Pushing the Limits: Chronotype and Time of Day Modulate Working Memory-Dependent Cerebral Activity.

Morning-type individuals experience more difficulties to maintain optimal attentional performance throughout a normal waking day than evening types. However, time-of-day modulations may differ across cognitive domains. Using functional magnetic resonance imaging (fMRI), we investigated how chronotype and time of day interact with working memory at different levels of cognitive load/complexity in a N-back paradigm (N0-, N2-, and N3-back levels). Extreme morning- and evening-type individuals underwent two fMRI sessions during N-back performance, one 1.5 h (morning) and one 10.5 h (evening) after wake-up time scheduled according to their habitual sleep–wake preference. At the behavioral level, increasing working memory load resulted in lower accuracy while chronotype and time of day only exerted a marginal impact on performance. Analyses of neuroimaging data disclosed an interaction between chronotype, time of day, and the modulation of cerebral activity by working memory load in the thalamus and in the middle frontal cortex. In the subjective evening hours, evening types exhibited higher thalamic activity than morning types at the highest working memory load condition only (N3-back). Conversely, morning-type individuals exhibited higher activity than evening-type participants in the middle frontal gyrus during the morning session in the N3-back condition. Our data emphasize interindividual differences in time-of-day preferences and underlying cerebral activity, which should be taken into account when investigating vigilance state effects in task-related brain activity. These results support the hypothesis that higher task complexity leads to a chronotype-dependent increase in thalamic and frontal brain activity, permitting stabilization of working memory performance across the day.

Seasonal variation of the pupil light reflex

PurposeVariation of retinal light sensitivity between winter and summer seasons may be a marker for seasonal affective disorder and the basis for response to phototherapy. As the pupil is a marker of retinal light sensitivity and shows a 24‐hour variation that reflects circadian rhythm, we used the pupil as proxy to assess light sensitivity of rods, cones and melanopsin as a function of seasonal light in healthy adults.Methods37 adults were tested during the short (January‐February) and long (July‐August) annual photoperiods. All subjects completed standardized questionnaires of seasonality and sleep. Pupil responses to blue (470 nm) and red (622 nm) light were recorded under dark and light adapted conditions using an automated pupillometer. Main outcome parameters were maximal contraction amplitude and post‐stimulus contraction amplitude.ResultsAll but two subjects reported good sleep quality. One subject was an extreme morning type. Twelve subjects reported a global seasonal variation in sleep, mood and appetite but without dysfunction or disability. Baseline pupil size of light adapted eyes was greater in summer compared to winter. Maximal contraction amplitudes to scotopic and photopic light stimuli were greater in summer. The post‐stimulus pupil contraction was also greater in summer, but only after light adaptation.ConclusionsBaseline pupil size and pupil responses derived from rods, cones and melanopsin photoreception were greater in summer in healthy adults. This seemingly greater retinal sensitivity to light when the photoperiod (daylength) is long suggests a more central basis for seasonal regulation of the pupil light reflex.

Diurnal Preference Predicts Phase Differences in Expression of Human Peripheral Circadian Clock Genes.

Background: Circadian rhythms play an integral role in human behavior, physiology and health. Individual differences in daily rhythms (chronotypes) can affect individual sleep-wake cycles, activity patterns and behavioral choices. Diurnal preference, the tendency towards morningness or eveningness among individuals, has been associated with interpersonal variation in circadian clock-related output measures, including body temperature, melatonin levels and clock gene mRNA in blood, oral mucosa, and dermal fibroblast cell cultures.Methods: Here we report gene expression data from two principal clock genes sampled from hair follicle cells, a peripheral circadian clock. Hair follicle cells from fourteen individuals of extreme morning or evening chronotype were sampled at three time points. RNA was extracted and quantitative PCR assays were used to measure mRNA expression patterns of two clock genes, Per3 and Nr1d2.Results: We found significant differences in clock gene expression over time between chronotype groups, independent of gender or age of participants. Extreme evening chronotypes have a delay in phase of circadian clock gene oscillation relative to extreme morning types. Variation in the molecular clockwork of chronotype groups represents nearly three-hour phase differences (Per3: 2.61 hours; Nr1d2: 3.08 hours, both: 2.86) in circadian oscillations of these clock genes.Conclusions: The measurement of gene expression from hair follicles at three time points allows for a direct, efficient method of estimating phase shifts of a peripheral circadian clock in real-life conditions. The robust phase differences in temporal expression of clock genes associated with diurnal preferences provide the framework for further studies of the molecular mechanisms and gene-by-environment interactions underlying chronotype-specific behavioral phenomena, including social jetlag.