The 24-hour variation of mood differs between morning- and evening-type individuals

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

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

Diurnal changes in differential sensitivity and temporal resolution in morning-type and evening-type individuals with normal hearing

The present study attempts to determine diurnal changes by testing the differential sensitivity and temporal resolution in morning-type, evening-type, and intermediate-type individuals with normal hearing. Thirty participants with normal hearing were divided into morning-type, evening-type, and intermediate-type using “Morningness–Eveningness Questionnaire”. The tests of differential sensitivity and temporal resolution were administered to all the participants in the morning and evening, respectively. The differences in the test results between different timing across all the three groups were analyzed. The results of the study showed that there was a significant diurnal effect on psychoacoustic tests as morning-type individuals performed better when tested in morning and evening-type performed better when they were tested in evening. However, there was no diurnal effect found in intermediate group. The lack of inhibitory control and poor cognitive load in off peak time could have lead to poor scores. Thus, the variable of diurnal effects should be considered in further studies on psychoacoustic tests, especially in young adults. Furthermore, studies could be performed to explore diurnal effects on objective audiological tests in a larger group of population in the future.

The role of chronotype, circadian misalignment, and tiredness in the substance use behaviors of gay and bisexual men

Although the potential of alcohol and drugs to detrimentally affect sleep has been established, the potential of tiredness to in turn influence substance use has received less attention. We contend that tiredness increases risk for substance use because tiredness impairs self-regulation and heightens the utility of substances to combat tiredness, albeit temporarily-and that these links are especially important because decision-making regarding use often occurs late at night when people are tired. Accordingly, we investigated chronotype, circadian misalignment, and perceived tiredness as risk factors in substance use among gay and bisexual men (GBM). We analyzed two online survey datasets-one of 3,696 GBM and one of 1,113 GBM-asking participants about their time for most frequently using alcohol or club/party drugs, their chronotype, whether they use substances to stay awake, and use severity. Alcohol use and club/party drug use most often occurred from 9pm onwards (for 51.3% and 75.1% of men, respectively), especially among younger men and evening types. Further, many men with a morning chronotype reported most often using alcohol (33.2%) and drugs (64.7%) from 9pm onwards, implicating circadian misalignment. Additionally, feeling tired was a motivator of alcohol use and drug use (for 53.1% and 26.9% of men, respectively), especially among younger men. Finally, those endorsing this motivation had greater use severity. These findings highlight the importance of chronotype, circadian misalignment, and tiredness in substance use, especially among younger men. We therefore recommend including substance use among the behaviors adversely affected by tiredness from circadian misalignment and inadequate/overdue sleep.

Associations of depression and seasonality with morning-evening preference: Comparison of contributions of its morning and evening components

Despite predominance of positive findings on associations of morning-evening preference with seasonality and depression, it remains to be clarified whether morning and evening components of this preference equally contribute to these associations and whether these associations persist after accounting for confounding variables. Data on retrospectively reported seasonal changes in well-being, mood, and behaviors were collected from 2398 residents of West Siberia, South and North Yakutia, Chukotka, Alaska, and Turkmenistan. Other self-reports included mental and physical health, sleep duration, and adaptabilities of the sleep-wake cycle. Depression was found to be linked to morning rather than evening component of morning-evening preference, i.e., morning lateness. Morning lateness was also linked to retrospectively reported degree of seasonal changes rather than to severity of problems associated with such changes. Variation in morning-evening preference explained not more than 2% and 4% of the total variation in depression and seasonality, respectively. The associations became even weaker but remained significant after accounting for other differences between respondents, such as their gender, age, physical health, and adaptability of their sleep-wake cycle. These results have practical relevance for understanding of the roles playing by morning earliness and insensitivity to seasonal changes in the environment to protection against different mood disorders.

Sleep Loss and Affective Functioning: More Than Just Mood

Empirical evidence supports an intimate link between sleep and affective functioning. While the bidirectional relationship between sleep duration and mood is well documented, limited research targets other aspects of affective functioning, such as emotion and emotion regulation, or considers their interrelationships. The present review summarizes research examining the relationship between sleep and emotion, emotion regulation, and mood, and presents a theoretical model representing the relationships between these constructs. Disruptions to sleep and mood may trigger and maintain a negative cascade, leading to more entrenched sleep problems and psychopathology. Given that insufficient sleep is a widespread phenomenon, understanding the interrelationships between sleep and affective functioning has implications for both public health and clinical practice.

Inter-Individual Differences in Neurobehavioural Impairment following Sleep Restriction Are Associated with Circadian Rhythm Phase

Although sleep restriction is associated with decrements in daytime alertness and neurobehavioural performance, there are considerable inter-individual differences in the degree of impairment. This study examined the effects of short-term sleep restriction on neurobehavioural performance and sleepiness, and the associations between individual differences in impairments and circadian rhythm phase. Healthy adults (n = 43; 22 M) aged 22.5 ± 3.1 (mean ± SD) years maintained a regular 8:16 h sleep:wake routine for at least three weeks prior to laboratory admission. Sleep opportunity was restricted to 5 hours time-in-bed at home the night before admission and 3 hours time-in-bed in the laboratory, aligned by wake time. Hourly saliva samples were collected from 5.5 h before until 5 h after the pre-laboratory scheduled bedtime to assess dim light melatonin onset (DLMO) as a marker of circadian phase. Participants completed a 10-min auditory Psychomotor Vigilance Task (PVT), the Karolinska Sleepiness Scale (KSS) and had slow eye movements (SEM) measured by electrooculography two hours after waking. We observed substantial inter-individual variability in neurobehavioural performance, particularly in the number of PVT lapses. Increased PVT lapses (r = -0.468, p < 0.01), greater sleepiness (r = 0.510, p < 0.0001), and more slow eye movements (r = 0.375, p = 0.022) were significantly associated with later DLMO, consistent with participants waking at an earlier circadian phase. When the difference between DLMO and sleep onset was less than 2 hours, individuals were significantly more likely to have at least three attentional lapses the following morning. This study demonstrates that the phase of an individual’s circadian system is an important variable in predicting the degree of neurobehavioural performance impairment in the hours after waking following sleep restriction, and confirms that other factors influencing performance decrements require further investigation.

Factors to consider when assessing diurnal variation in sports performance: the influence of chronotype and habitual training time-of-day

PURPOSE

The aim of this study was to compare morning and evening time-trial performance, RPE and mood state of trained swimmers, taking into account chronotype, habitual training time-of-day and PERIOD3 (PER3) variable number tandem repeat genotype.

METHODS

Twenty-six swimmers (18 males, age: 32.6 ± 5.7 years) swam 200 m time trials (TT) at 06h30 and 18h30 in a randomised order.

RESULTS

There was no difference between morning and evening performance when the swimmers were considered as a single group (06h30: 158.8 ± 22.7 s, 18h30: 158.5 ± 22.0 s, p = 0.611). However, grouping swimmers by chronotype and habitual training time-of-day allowed us to detect significant diurnal variation in performance, such that morning-type swimmers and those who habitually train in the morning were faster in the 06h30 TT (p = 0.036 and p = 0.011, respectively). This was accompanied by lower ratings of perceived exertion (RPE) scores post-warm-up, higher vigour and lower fatigues scores prior to the 06h30 TT in morning-type swimmers or those who trained in the morning. Similarly, neither types and those who trained in the evenings had lower fatigue and higher vigour prior to the 18h30 TT.

CONCLUSIONS

It appears that both chronotype and habitual training time-of-day need to be considered when assessing diurnal variation in performance. From a practical point of view, athletes and coaches should be aware of the potentially powerful effect of training time on shifting time-of-day variation in performance.

Polymorphisms in the circadian expressed genes PER3 and ARNTL2 are associated with diurnal preference and GNβ3 with sleep measures

Sleep and circadian rhythms are intrinsically linked, with several sleep traits, including sleep timing and duration, influenced by both sleep homeostasis and the circadian phase. Genetic variation in several circadian genes has been associated with diurnal preference (preference in timing of sleep), although there has been limited research on whether they are associated with other sleep measurements. We investigated whether these genetic variations were associated with diurnal preference (Morningness-Eveningness Questionnaire) and various sleep measures, including: the global Pittsburgh Sleep Quality index score; sleep duration; and sleep latency and sleep quality. We genotyped 10 polymorphisms in genes with circadian expression in participants from the G1219 sample (n = 966), a British longitudinal population sample of young adults. We conducted linear regressions using dominant, additive and recessive models of inheritance to test for associations between these polymorphisms and the sleep measures. We found a significant association between diurnal preference and a polymorphism in period homologue 3 (PER3) (P < 0.005, recessive model) and a novel nominally significant association between diurnal preference and a polymorphism in aryl hydrocarbon receptor nuclear translocator-like 2 (ARNTL2) (P < 0.05, additive model). We found that a polymorphism in guanine nucleotide binding protein beta 3 (GNβ3) was associated significantly with global sleep quality (P < 0.005, recessive model), and that a rare polymorphism in period homologue 2 (PER2) was associated significantly with both sleep duration and quality (P < 0.0005, recessive model). These findings suggest that genes with circadian expression may play a role in regulating both the circadian clock and sleep homeostasis, and highlight the importance of further studies aimed at dissecting the specific roles that circadian genes play in these two interrelated but unique behaviours.

Delayed sleep onset in depressed young people

BACKGROUND

The circadian abnormality of delayed sleep phase has been suggested to characterise a subgroup of depressed young adults with different risk factors and course of illness. We aim to assess the prevalence and factors, particularly substance use, associated with such delay in a large help-seeking cohort of young people with mental health problems.

METHODS

From a consecutively recruited sample of 802 help-seeking young people, 305 (38%) had at least moderate depressive symptoms (QIDS-C16 >10), sleep data and did not have a chronic severe mental illness. Demographic and clinical characteristics were evaluated through self report and clinical interview. Delayed sleep phase was defined as a sleep onset between the hours of 02:00 a.m. - 06:00 a.m. and the characteristics of this group were compared to normal phase sleepers.

RESULTS

Delayed sleep onset was reported amongst 18% (n = 56/305) of the depressed group compared to 11% of the non-depressed young people. Amongst the depressed group, delayed sleep onset was associated with tobacco, alcohol and cannabis misuse and short sleep duration (x̅: 5.8 hrs vs. x̅: 7.8 hrs). There were no differences in demographic factors, personality traits or symptoms. Tobacco smoking was very common: In logistic regression analyses only tobacco use (OR 2.28, 95% CI: 1.04 - 5.01) was associated with delayed sleep onset. There was no interaction with age.

CONCLUSIONS

Delayed sleep onset was twice as common in depressed young people as the general population and young people with other mental health problems, and is a potential marker for a subgroup of mood disorders. Those with delayed sleep onset were not more severely depressed but had short sleep duration, a risk for chronic psychological ill health, and higher levels of tobacco use. Nicotine use was common in this group, has biological evidence as a sleep disrupter, and requires specifically addressing in this population.

Association between sleep disturbances and abdominal symptoms

OBJECTIVE

Although gastroesophageal reflux disease (GERD) is known to cause sleep disturbances, the relationships between other abdominal symptoms and sleep disorders have not been clarified. In the present study, we examined the relationships between daytime sleepiness and various abdominal symptoms in a non-clinical population.

METHODS

We enrolled 2,936 subjects who visited Matsue Red Cross Hospital for an annual health check examination during a 10-month consecutive period after excluding those with organic gastrointestinal diseases. The Izumo scale abdominal symptom and Epworth Sleepiness Scale (ESS) questionnaires were employed to evaluate the presence of abdominal symptoms and daytime sleepiness.

RESULTS

Among the 2,936 subjects, 233 (7.9%), 254 (8.6%) and 528 (18%) had GERD-like, functional dyspepsia (FD)-like and irritable bowel syndrome (IBS)-like symptoms, respectively. The ESS scores in the subjects with GERD-, FD- and IBS-like symptoms were significantly higher than those observed in the asymptomatic subjects. The subjects with multiple abdominal symptoms tended to have higher ESS scores than those with single symptoms. A multiple logistic regression analysis revealed a younger age and the presence of FD- and IBS-like symptoms to be significant influencing factors for sleep disturbances.

CONCLUSION

The presence of FD and IBS symptoms in addition to GERD symptoms exhibits a strong relationship with sleep disturbances from the viewpoint of daytime sleepiness.

Selected neurophysiological, psychological, and behavioral influences on subjective sleep quality in nurses: a structure equation model

Few studies have examined relationships among neurophysiological, psychological, and behavioral factors with regard to their effects on sleep quality. We used a structure equation model to investigate behavioral and psychological factors that influence neurophysiological regulation of sleep in shift workers. Using a cross-sectional study design, we tested the model with a sample of 338 female nurses working rotating shifts at an urban regional hospital. The Morningness-Eveningness Questionnaire (MEQ) and short-form Menstrual Distress Questionnaire (MDQ) were used to measure neurophysiological factors involved in morningness-eveningness and menstrual distress. The Sleep Hygiene Awareness and Practice Scale (SHAPS) and Profile of Mood States Short Form (POMS-SF) were completed to measure behavioral factors of sleep hygiene practices and psychological factors of mood states. In addition, the Pittsburgh Sleep Quality Index (PSQI) measured participant's self-reported sleep quality. The results revealed that sleep hygiene practices and mood states mediated the effects of morningness-eveningness and menstrual distress on sleep quality. Our findings provide support for developing interventions to enhance sleep hygiene and maintain positive mood states to reduce the influence of neurophysiological factors on sleep quality among shift workers.

In vitro circadian period is associated with circadian/sleep preference

Evaluation of circadian phenotypes is crucial for understanding the pathophysiology of diseases associated with disturbed biological rhythms such as circadian rhythm sleep disorders (CRSDs). We measured clock gene expression in fibroblasts from individual subjects and observed circadian rhythms in the cells (in vitro rhythms). Period length of the in vitro rhythm (in vitro period) was compared with the intrinsic circadian period, τ, measured under a forced desynchrony protocol (in vivo period) and circadian/sleep parameters evaluated by questionnaires, sleep log, and actigraphy. Although no significant correlation was observed between the in vitro and in vivo periods, the in vitro period was correlated with chronotype, habitual sleep time, and preferred sleep time. Our data demonstrate that the in vitro period is significantly correlated with circadian/sleep preference. The findings suggest that fibroblasts from individual patients can be utilized for in vitro screening of therapeutic agents to provide personalized therapeutic regimens for CRSD patients.

Individual traits and environmental factors influencing sleep timing: a study of 225 Japanese couples

Behavioral and physiological processes, such as sleep-wakefulness, thermoregulation, and hormone secretion, exhibit 24-h rhythms in most organisms. These biological rhythms are driven by the circadian clock system and are entrained by the external environment, which in the case of humans includes social time schedules. Couples might be ideal experimental subjects to discriminate between individual traits and environmental factors, as they share lifestyle habits but not genetic backgrounds. In this study, sleep timing was compared between married Japanese couples (n = 225) who had lived together for 1 yr or more (mean 17 yrs). Additionally, the authors evaluated the influence of individual traits and environmental factors on an individual's sleep timing per each couple. The results reveal that the sleep timings of a couple are mainly associated with the chronotypes of the husband and wife, whereas the sleep timings are significantly influenced by certain environmental factors. The findings suggest that chronotype remains one of the major determinants of an individual's sleep onset and wake times. Understanding an individual's chronotype may help improve the quality of life issues surrounding sleep.

Morningness-eveningness, chronotypes and health-impairing behaviors in adolescents

The impact of diurnal preferences on health-related behaviors is acknowledged but relatively understudied. The aim of this study was threefold: (1) testing the measurement model of the Hungarian version of the reduced Horne-Östberg Morningness-Eveningness Questionnaire (Hungarian Version of the rMEQ); (2) estimating chronotypes and their prevalence; and (3) analyzing the relationship between morningness-eveningness/chronotypes and health-impairing behaviors, including smoking, alcohol use, and physical inactivity in adolescents. Self-reported data on the Hungarian version of the rMEQ, smoking, alcohol use, and physical inactivity obtained from Hungarian high-school students (ninth grade, N = 2565) were analyzed with confirmatory factor analysis (CFA), latent profile analysis (LPA), structural equation modeling, and analysis of variance (ANOVA). A one-factor model of morningness was supported, which included rising time, peak time, retiring time, and self-evaluation of chronotype. Morningness was significantly associated with a lower likelihood of smoking and alcohol use, and also with a lower level of physical inactivity. Using LPA, the authors identified three chronotypes: intermediate type (50.7%), morning type (30.5%), and evening type (18.8%). Compared to the evening-type participants, intermediate- and morning-type participants were significantly less likely to experiment with smoking, to smoke nondaily, and to smoke daily. Moreover, both intermediate- and morning-type students reported less lifetime alcohol use and less physical inactivity than evening-type students. Chronopsychological research can help to understand the relatively unexplored determinants of health-impairing behaviors in adolescents associated with chronotype.

Morningness-eveningness and depression: preliminary evidence for the role of the behavioral activation system and positive affect

There is considerable evidence of circadian rhythm abnormalities in mood disorders. Morningness-eveningness, the degree to which people prefer organizing their activity and sleep patterns toward the morning or evening, is related to circadian phase and is associated with mood, with relatively greater psychological distress among evening types. Given that circadian rhythms may also relate to the Behavioral Activation System (BAS) and positive affect (PA), but not to the Behavioral Inhibition System (BIS) or negative affect (NA), it was hypothesized that individual differences in BAS sensitivity and levels of PA, but not BIS and NA, would explain the association between morningness-eveningness and depression in a sample of 208 individuals with a range of depressive symptomatology. As predicted, increasing eveningness was associated with greater depression, lower BAS, and lower PA, but not directly associated with NA. Path analyses supported a model wherein morningness-eveningness is associated with depression via multi-step indirect paths including BAS-Reward Responsiveness, PA, and NA. A path between BIS and depression was distinct from the one involving morningness-eveningness. A variety of alternative path models all provided a weaker fit to the data. Thus, results were consistent with the BAS and PA mediating the effects of morningness-eveningness on depression.

Validity of the Morningness‐Eveningness Scale for Children among Spanish Adolescents

Adolescents tend to be much later chronotypes than other age groups. This circadian phase delay is attributed as much to biological as psychosocial factors. Because the consequences of this change on performance and health have been documented, questionnaires to identify morning and evening-type adolescents are necessary. The aim of the present study was to validate a Spanish version of the Morningness-Eveningness Scale for Children (MESC) by means of several relevant psychological variables as external criteria. A sample of 623 urban high school students completed the MESC and self-reported measures of sleep behaviors, subjective alertness, physical performance, and mood. On the whole, results indicate a good validity of MESC. Significant differences in the self-reported ratings between morning and evening types were obtained by time-of-day. These results provide preliminary support for the Spanish version of MESC.

A Psychometric Evaluation and Validation of the Preferences Scale

The Preferences Scale (PS) is a new measure of morningness and therefore requires intensive investigation to establish its measurement properties and validity. A confirmatory factor analysis (CFA) of Smith and colleagues (2002) posited model structure was not optimal in both a student (n = 731) and working sample (n = 218). However, significant differences (p < 0.01) were found for times to sleep and wake between morning and evening types. Principal components and reliability analyses were used to develop a 6-item model comprising 2 factors using a student sample (n = 368). Cronbach's alpha for the PS was 0.73 and the factors explained 61% of the variance. The revised model was replicated via CFA in a separate student sample (n = 363). A subsequent CFA confirmed the model structure in the working sample. Cronbach's alpha was 0.74 and the factors explained 64% of the variance. Significant differences (p < 0.01) in self-reported alertness ratings between morning and evening types were obtained by time-of-day. These results provide preliminary support for the PS. The predictive efficacy of the PS requires further validation against a number of health and work-related variables.

Daytime sleepiness during transition into daylight saving time in adolescents: Are owls higher at risk?

BACKGROUND

Individuals differ in their biological rhythms and preferences for time of day. Here, we looked at the transition into daylight saving time (DST) in adolescents. As adolescents tend to be evening types, one may expect that they suffer from a transition into DST.

METHODS

To assess these changes, we measured daytime sleepiness and morningness-eveningness preference (CSM score) in adolescents.

RESULTS

Daytime sleepiness correlated with age and CSM score. Older pupils and evening types showed a higher sleepiness. Daytime sleepiness was higher after the transition until the third week after. Older pupils and pupils scoring higher on eveningness reported higher daytime sleepiness after the transition, suggesting that these pupils suffer most from the change. Using cut-off scores for larks and owls, we found that owls showed higher sleepiness than larks.

CONCLUSION

As one consequence, class and school performance tests should not take place in the first week(s) after the transition into DST.

Morningness-eveningness comparison in adolescents from different countries around the world

Very few studies have focused on differences in chronotype around the globe. In this study, morningness-eveningness was measured using the Composite Scale of Morningness and the midpoint of sleep on free days (corrected for sleep debt, MSF(sc)) in adolescents of sixteen German schools abroad, dispersed all over the world, and for comparison pupils attending German schools. There was no influence of duration of residence in the respective locality, and sex differences were weak. Age correlated negatively with morningness. A significant influence of climate zone (temperate, subtropics, tropics) was found, with adolescents in the subtropics being the latest chronotypes, and an interaction of agexclimate zone was identified. Significant associations between chronotype and longitude and latitude were identified within the time zone of central Europe. Adolescents were found to be more morning oriented both toward the East and North. The results indicate that climate, longitude, and latitude contribute to chronotype.

Morningness-Eveningness Among German and Spanish Adolescents 12–18 Years

Individual differences in human biological rhythms and diurnal preference (morningness-eveningness) are often based on self-report scales. Here, we compare Spanish (N = 771) and German (N = 1,182) adolescents (12–18 years) using the Composite Scale of Morningness (CSM). A 3-factorial solution of the CSM was supported in both countries, morningness, activity planning, and alertness factors, and the last two factors were invariant across countries. Morningness decreased with age, and higher morningness was found in German pupils. Gender differences were not significant concerning the alertness factor but existed in the activity-planning factor with girls scoring higher, and in the morningness factor with boys scoring higher. Interactions suggest that the linear trend toward eveningness is less pronounced in Spanish adolescents, whereas German boys showed the steepest linear decline in their over time compared to German girls and to Spanish boys who showed a U-shaped tendency.

Circadian rhythm sleep disorders: characteristics and entrainment pathology in delayed sleep phase and non-24-h sleep-wake syndrome

This paper presents a clinical review of delayed sleep phase syndrome (DSPS) and non-24-h sleep-wake syndrome (non-24). These syndromes seem to be common and under-recognized in society, not only in the blind, but also typically emerging during adolescence. Both types of syndrome can appear alternatively or intermittently in an individual patient. Psychiatric problems are also common in both syndromes. DSPS and non-24 could share a common circadian rhythm pathology in terms of clinical process and biological evidence. The biological basis is characterized by a longer sleep period, a prolonged interval from the body temperature nadir-to-sleep offset, a relatively advanced temperature rhythm, lower sleep propensity after total sleep deprivation, and higher sensitivity to light than in normal controls. There are multiple lines of evidence suggesting dysfunctions at the behavioral, physiological and genetic levels. Treatment procedures and prevention of the syndromes require further attention using behavioral, environmental, and psychiatric approaches, since an increasing number of patients in modern society suffer from these disorders.

Yawning in morning and evening types

Yawning occurs more frequently in the early morning and in the late evening, close to sleep onset and after the awakening, and it might be linked to sleep propensity. We aimed to study yawning and its temporal distribution in morning and evening subjects who display different sleep-wake and sleepiness rhythms. Sixteen healthy young adults (8 evening-types and 8 morning-types, matched for age and gender) have been selected and instructed to keep their habitual sleep schedules and to signal every yawning occurrence for three consecutive days. Results show that evening-types yawn more frequently than morning-types, particularly during morning hours. Yawning frequency decreases across daytime in evening-types reaching its lowest level in the early evening and increases thereafter. Instead, in morning-types, yawning frequency remains quite low during daytime and increases in the evening. Moreover, both morning and evening types show a progressive increase of yawning frequency in the hours preceding sleep onset, whereas they differ after the awakening. Evening-types show a higher yawning frequency that remains quite stable in the hours following the awakening, while morning-types display a decline in yawning frequency. Our findings show that the temporal distribution of yawning frequency differs between chronotypes, supporting the hypothesis that differences in sleep-wake rhythm affect yawning, which could represent a behavioural sign of sleep propensity.

Diurnal Changes of ERP Response to Sound Stimuli of Varying Frequency in Morning-type and Evening-type Subjects

In order to study the cognitive function rhythm related to the auditory frequency system for people who prefer to be active in the morning and at night, we conducted an experiment during morning (09:00), evening (17:00) and late-night (01:00) periods. On the basis of a morningness/eveningness questionnaire, six moderately morning-type subjects (M-types) and seven evening-type subjects (E-types) were selected. Diurnal variation of event-related potential (ERP) were assessed under low-frequency (250/500 Hz) and high-frequency (1000/2000 Hz) condition using an oddball task. M-types were tested during the morning (09:00) and evening (17:00) periods, and E-types were tested during the evening (17:00) and midnight (01:00) periods. Subjects were asked to press a button when the target stimulus was detected. We found that the P300 amplitude at 09:00 was significantly greater than that at 17:00 for M-types, was significantly greater at 17:00 than that at 01:00 for E-types. A significant difference of P300 latency and P300 amplitude was observed at 17:00 between M-types and E-types. The P300 amplitude obtained after a low-frequency stimulus was significantly greater than that after a high-frequency stimulus at 09:00 for M-types, and at 01:00 for E-types. These results revealed that stimulus frequency had effects on the diurnal changes of human cognitive function, and circadian typology had a direct effect on the diurnal change of human cognitive function. This study has extended the previous findings of auditory P300 studies on diurnal variations in terms of circadian typology and stimulus parameter.

Acute HPA axis responses, heart rate, and mood changes to psychosocial stress (TSST) in humans at different times of day

There is evidence showing that HPA axis responses to pharmacological provocation depend on time of day with larger cortisol responses in the afternoon and evening compared to the morning hours. However, it is still unknown whether HPA axis responses to psychological stress are affected by time of day and whether they can be assessed with equal reliability in the morning and afternoon, respectively. The present reanalysis is based on five independent studies conducted in the same laboratory by and. All subjects were confronted with the Trier Social Stress Test (TSST) either in the morning or in the afternoon. The total sample consisted of 180 adults with 115 younger (49 females, 66 males) and 65 older adults (32 females, 33 males). All ANCOVA results controlled for possible age and gender effects. Stress-related free salivary cortisol, total plasma cortisol and ACTH net increases did not differ according to time of day (all p = n.s.). However, as expected pre-stress free salivary and total plasma cortisol levels differed significantly between the morning and afternoon group (both p < 0.005), leading to a significantly higher free cortisol area under the curve (AUC) in the morning (p = 0.02). Taken together, these observations suggest that the adrenal glands may be more sensitive to ACTH in the morning. Additionally, higher basal salivary cortisol levels were related to a lower stress-related net increase in salivary cortisol (p = 0.02), total plasma cortisol (p < 0.0001), and marginally ACTH (p = 0.09). Stress-related heart rate increases did not differ between groups (p = n.s.). The finding that the TSST-induced mood change was differentially affected by time of day requires further exploration. We conclude that comparable HPA axis and heart rate stress responses to psychosocial stress can be measured in the morning and afternoon.

Evaluation of behavioral states among morning and evening active healthy individuals

The Horne-Ostberg questionnaire partly covers some factors that may be important determinants of peak time and characterize patterns of behavior. We conducted a study for the evaluation of self-reported behavioral states (hunger sensation, availability for study, physical exercise, solving daily problems, and time preferences) as expressions of underlying cyclic activity. Three hundred and eighteen community subjects without history of medical, psychiatric, or sleep disorders were evaluated in a cross-sectional design. A self-report about daily highest level of activity was used to categorize individuals into morning, evening, and indifferently active. Time-related behavioral states were evaluated with 23 visual analog questions. The responses to most analogic questions were significantly different between morning and evening active subjects. Logistic regression analysis identified a group of behaviors more strongly associated with the self-reported activity pattern (common wake up time, highest subjective fatigue, as well as wake up, bedtime, exercise and study preferences). These findings suggested that the patterns of activity presented by normal adults were related to specific common behavioral characteristics that may contribute to peak time.

Gender differences in morningness-eveningness preference

Morningness-eveningness preference (morning-, intermediate-, evening-type) or circadian typology is the individual difference that most clearly explains the variations in the rhythmic expression of biological or behavioral patterns. The aim of this study was to analyze gender difference in morningness-eveningness preference using the Horne and Ostberg questionnaire in the largest university student population selected so far (N = 2135), with an age range 18-30 yr. Morningness-eveningness questionnaire (MEQ) score distribution closely correlated to the normal curve (range 17-78, mean = 48.25; SD = 10.11), with 338 (15.84%) morning-types, 1273 (59.62%) intermediate-types, and 524 (24.54%) evening-types. The men and women differed significantly in their mean scores (p < 0.0001) and distribution per circadian typology (p < 0.00001), with the men presenting a more pronounced eveningness preference. Three factors were identified by factor analysis: time of greatest efficiency (I), sleep time/sleep phase (II), awakening time/sleep inertia (III). The MEQ items sensitive to gender differences were essentially those included in factor I and factor II. The results are discussed in relation to recent models of circadian regulation of the sleep-wake cycle.

Gender differences in diurnal variations of subjective activation and mood

This article evaluates the influence of gender on diurnal and postlunch period variations in subjective activation and mood. This topic is not often addressed in the literature; particularly, little attention has been paid to how biological rhythms might bias research results. We studied 40 university student volunteers (20 men, 20 women) aged 18 to 23 years old (X = 20.23, SD = 1.03); they responded to questions on eight unipolar visual analog scales every hour from 08:00 to 21:00. Gender differences were observed in both diurnal and postlunch variations for scales of positive activation (alertness, vigor); sleepiness, however, was only sensitive to diurnal variation, and weariness was sensitive only to a postlunch effect. Women displayed a morning-type pattern, with their optimal moment (11:00) coming 2h earlier than for men, and their activation ratings ranged more widely. The only mood scale that showed differences related to gender was that of happiness, for which women had a higher diurnal mean, a diurnal peak 2h earlier, and a less-intense postlunch effect. Endogenous control of rhythmic pattern appears to be less intense in women, probably due to the coexistence of circamensual rhythmicity, although environmental or sociocultural influences may play a modulating role. Chronopsychological gender differences in affective states should be studied further given the implication they have for the prevention and treatment of mood disorders.

Owls, larks and the significance of morningness/eveningness rhythm propensity in psychiatric-mental health nursing

In the last decade there has been an upsurge in the research focusing on the interplay between the human circadian timing system and behavioral patterns in health and illness. Of particular interest in this area of inquiry is the overlay of what has been termed chronotype. What this refers to is the propensity of biological rhythms to express themselves in certain patterns of behavior. Commonly, these patterns have received names such as owl (evening chronotype) or lark (morning chronotype). Many people are neither a strong morning nor evening chronotype. If illness represents a change in the way a person's body functions within a given environment, then it is reasonable to believe that an "owl's" symptom presentation may vary significantly from the patterns of a "lark" who becomes ill. Recognizing that psychiatric nurses at both the generalist and the advanced practice levels have a strong interest in patterns of behavior, it stands to reason that using a lens that incorporates notions of the body's clock becomes essential. The interplay between the body's timing system and the thousands of other psychobiological rhythmic functions occurring everyday and within every human being is referred to as chronobiology. This article provides a primer for psychiatric nurses on issues of chronobiology related to morningness and eveningness rhythm propensity.