Scores on morningness-eveningness and sleep habits of Korean students, Japanese students, and Japanese workers

The Japanese version of the reduced morningness-eveningness questionnaire

Circadian typology, or "morningness" and "eveningness," is generally assessed using the Morningness-Eveningness Questionnaire (MEQ), a 19-item scale that could be burdensome in large-scale surveys. To overcome this, a 5-item version known as the reduced morningness-eveningness questionnaire (rMEQ), which is sensitive to the assessment of circadian typology, was developed; however, a validated Japanese version of the rMEQ is yet to be established. This study aimed to develop and validate the Japanese version of the rMEQ. Five essential items for the rMEQ were selected from existing Japanese MEQ data (N = 2,213), and the rMEQ was compiled. We conducted a confirmatory factor analysis for the psychometric properties of the rMEQ and confirmed its robust one-factor structure for evaluating morningness-eveningness (GFI = 0.984, AGFI = 0.951, CFI = 0.935, and RMSEA = 0.091). Reliability was evaluated via internal consistency of rMEQ items using Cronbach's α and McDonald's ω, and the values were 0.618 and 0.654, respectively. The rMEQ scores strongly correlated with MEQ (ρ = 0.883, p < 0.001), and classification agreement (Morning, Neither, and Evening types) between rMEQ and MEQ was 77.6% (Cramer's V = 0.643, Weighted Cohen's κ = 0.72), confirming the validity. The Japanese rMEQ may be a valuable tool for the efficient assessment of circadian typologies.

Association between sleep hours and changes in cognitive function according to the morningness-eveningness type: A population-based study

OBJECTIVE

The aim of this study was to investigate proper sleep hours to reduce the risk of cognitive decrease considering morningness-eveningness type.

METHODS

The Korean Community Health Survey was used, which includes adults aged over 19 years old. These data were obtained from a cross-sectional study and assessed sleep hours using questionnaire of Pittsburgh Sleep Quality Index. Based on the wake-up time of each participant, they were classified into the morningness, intermediate, eveningness, and none groups. The change in cognitive function was determined by a single question about memory loss experience.

RESULTS

A total of 224,714 participants were included in the analysis. Of the participants, 55.6 % and 5.0 % of whom had morningness and eveningness, respectively. The risk of cognitive decline was significantly different by sleep hours and morningness-eveningness type. Without considering sleep quality, the intermediate and eveningness groups showed a higher risk of cognitive decline than the morningness group, and the risk was lowest in those with 7-9 sleep hours. However, when sleep quality showing significant effect was included in the analysis, sleep hours showing the lowest risk were different among morningness, intermediate, eveningness groups, and it was the shortest in the morningness type at 5-6 h and the longest in the eveningness type at 7-8 h.

CONCLUSION

Proper sleep hours to decrease the risk of cognitive decline may be different by morningness-eveningness types. However, when considering sleep quality, sleep duration had little influence on cognitive decline. Future studies investigating healthy sleep hours need to consider sleep quality as well as the habitual sleep schedules.

LIMITATIONS

The morningness-eveningness types were classified based on wake-up time not morningness-eveningness types. The morningness-eveningness types in this study would be interpreted as habitual sleep schedule rather than chronotype.

The impact of social networks on sleep among a cohort of college students

Background

Sleep duration and quality are associated with physical and mental wellbeing. This paper examines social network effects on individual level change in the sleep quantity and quality from late adolescence to emerging adulthood and its associated factors, including the influence of peers on sleep behavior and the impact of changes in network size.

Methods

We use sleep data from 619 undergraduates at the University of Notre Dame obtained via Fitbit devices as part of the NetHealth project. The data were collected between August 16, 2015 and May 13, 2017. We model trends in sleep behaviors using latent growth-curve models.

Results

Controlling for the many factors known to impact sleep quantity and quality, we find two social network effects: increasing network size is associated with less sleep and a student's sleep levels are influenced by his or her peers. While we do not find any consistent decline in sleep quantity over the 637 days, daily fluctuations in sleep quantity are associated with changes in network size and the composition of a student's network. As a student's network gets bigger, s/he sleeps less, and when a student's contacts sleep more (or less) than s/he does, the student becomes more like his or her contacts and sleeps more (or less).

Conclusions

Social networks can and do impact sleep, especially sleep quantity. In contexts where students want to have larger networks, the difficulties of increasing network size and maintaining larger networks negatively impact sleep. Because of peer influence, the effectiveness of interventions designed to improve sleep practices could be increased by leveraging student social networks to help diffuse better sleep habits.

•

The sleep habits of 619 undergraduates were traced with Fitbit devices for 637 days.

•

Their sleep quantity measures were relatively stable but affect by peers.

•

Their sleep quality was slightly getting worse but not affected by peers.

Subjective sleep quality, quantitative sleep features, and their associations dependent on demographic characteristics, habitual sleep–wake patterns, and distinction of weekdays/weekends

Generally applicable qualifications of sleep and principles for achieving better sleep are difficult to design, because sleep quality can depend on individual demographic characteristics and lifestyles. In this study, the static and dynamic features of sleep–wake patterns were analyzed in association with quantitative sleep-related parameters and self-rated sleep quality to serve as a practical selection of sleep–wake patterns fitted to individual conditions. Data obtained over a 2-week period by actigraphy from university students and information technology workers were measured to obtain a daily subjective rating of sleep quality using the Oguri–Shirakawa–Azumi (OSA) sleep inventory. Qualitative sleep quality in terms of OSA score and quantitative sleep-related and chronobiological features were analyzed with regard to their dependency on the demographic characteristics, habitual sleep–wake patterns (HSWP), and distinction of weekdays/weekends. Multi-factor ANOVA was used to further investigate their dependencies regarding multiple ways of interactions between the demographic characteristics, HSWP, and distinction of weekdays/weekends. Subjective sleep quality and quantitative sleep-related parameters depended on the demographic characteristics, and so did their associations. The classification of day-to-day variations in HSWP showed four clusters that were effective factors for understanding their dependencies. Multi-factor analysis revealed demographic characteristics, HSWP, distinction of weekdays/weekends, and their multi-way interactions up to 3rd order as significant effectors of qualitative and quantitative quality of sleep. This study clarified how quantitative sleep-related parameters, subjective sleep quality, and their associations depended on demographic characteristics. Furthermore, their dependency was understood as a combination of multi-way interactions between the demographic characteristics, HSWP, and the distinction of weekdays/weekends. Our findings could provide a basis for the design of individually matched sleep–wake patterns.

Circadian preferences and personality traits: A meta‐analysis

In this study we report results of a meta‐analysis of studies linking personality to circadian rhythms. A total of 35 independent samples, 96 correlations and 8589 participants were included. Results showed that conscientiousness is the personality dimension that mostly related to morningness (r = .29). Agreeableness was also related to morningness although to a lesser degree (r = .13). Openness to experience, extraversion and neuroticism, contribute to a very small degree (i.e. −.09, −.06 and −.07, respectively). Furthermore, moderation analyses suggested effects of personality measure (big five vs. other) and sample (students vs. workers). Average age of participants had no significant impact on the relationship between morningness and personality, apart from a very trivial influence on openness to experience. Copyright © 2010 John Wiley & Sons, Ltd.

Gender differences in sleep habits and quality and daytime sleepiness in elementary and high school teachers

The extensive workload of teachers inside and outside the classroom may contribute to sleep problems. Such problems may occur more frequently in women due to the combination of professional demands, domestic tasks, and their relatively greater sleep needs compared to men. The objective of this cross-sectional study was to evaluate the influence of gender on sleep habits and quality, and daytime sleepiness in a sample of 243 teachers (77 men and 166 women) using questionnaires. Linear regression models were used to examine the effect of gender on sleep measures; the unadjusted model considered only gender and the adjusted model considered chronotype and work characteristics as potential confounders. Bedtimes of women were significantly earlier than men during the week, but not on weekends, in the unadjusted and adjusted models. Time in bed was longer for women throughout the week and weekend in the unadjusted model. However, in the adjusted model, this statistical significance disappeared, and longer time in bed during the week was associated with teaching in one shift and for both levels of education. In addition, the female gender was associated with higher sleepiness scores compared to males in both models, and worse sleep quality in the adjusted model. Also, sleep quality was worse in subjects working in three shifts and in both types of schools (public and private). The tendency to eveningness was associated with later bedtimes and wake up times during both week days and weekends, higher irregularity of bedtimes and wake up times, and higher sleepiness scores in the adjusted model. Therefore, we suggest that female teachers do not fulfill their sleep needs and show higher levels of diurnal sleepiness and poor sleep quality that can be modulated by chronotype and some work characteristics. More studies are needed to evaluate the role of double workload on this pattern.

Compare the educational achievement of medical students with different circadian rhythms in difficult courses of basic sciences

BACKGROUND

Advantageous times for different people are different to some extent, considering the effective physiological changes during the circadian rhythm, in terms of the peak time of physiological activities. The goal of this study is to compare the educational achievement of students, with different morning-evening habits, in completing difficult and easy courses.

MATERIALS AND METHODS

This research is a retrospective descriptive-analytical study, which has been conducted on students of the fifth semester of General Medicine in the Faculty of Medicine, Isfahan University of Medical Sciences. The morning-evening habits of the students were determined by the Horne-Strauss 19-item questionnaire. The students were asked to determine the courses that were 'difficult' and 'easy,' using a researcher-made questionnaire. The students' scores in the considered courses during the five semesters were obtained from the Education Department of the Faculty and analyzed using the descriptive t-test, analysis of variance (ANOVA), and the multivariate regression test in the SPSS software.

RESULTS

Sixty-three students (67% girls and 33% boys) participated in this study, of whom 11, 60, and 29% were morning, morning-evening, and evening students, respectively. The mean scores of the difficult courses in all five semesters were reduced in the evening pattern compared to the morning and morning-evening patterns. Reduction of the mean score in the difficult courses, in the evening group, compared with the morning-evening and morning groups was observed in all five semesters among girls, but in three semesters among boys.

CONCLUSION

This study showed that evening students experienced academic failure in difficult courses, which required a more cognitive performance. It is recommended that difficult specialized courses be presented at hours when all student groups have a better cognitive performance.

Chronotypes in patients with nonseasonal depressive disorder: Distribution, stability and association with clinical variables

The individual's chronotype is regarded as rather stable trait with substantial heritability and normal distribution of the "morningness-eveningness" dimension in the general population. Eveningness has been related to the risk of developing affective, particularly depressive, disorders. However, age and other sociobiological factors may influence chronotypes. The present study investigated the distribution, stability, and clinical correlates of chronotype and morningness-eveningness in hospitalized patients with affective disorder. Chronotype was assessed with the morningness-eveningness questionnaire (MEQ) in 93 patients with nonseasonal depressive syndrome (85% major depression; 15% depressive adjustment disorder) after admission, and in 19 patients again before discharge. Distribution, stability and correlations of MEQ scores with clinical variables were calculated. Additionally, a literature analysis of chronotype distributions in samples of nondepressed persons and patients with nonseasonal depression was carried out. MEQ scores (mean 49 ± 11, range 23-75, higher scores indicate morningness) in 93 acutely depressed inpatients (age 41 ± 14 years, range 18-75 years; 63% women; hospitalization 48 ± 22 days; BDI-II 32 ± 11) were normally distributed (Shapiro-Wilk test; W = 0.993, p = 0.920) with 59.1% intermediate types, 19.4% evening types, and 21.5% morning types. MEQ change scores from admission to discharge were nonsignificant (-1.3 ± 5.0; paired t-test, t18 = -1.09; p = 0.29) despite significantly improved depression scores (-19.4 ± 7.6; paired t-test, t18 = 11.2, p < 0.001). Age (r = 0.24), and depression scores (r = -0.21) correlated significantly (p < 0.05) with MEQ scores; associations with sex and hospitalization duration were nonsignificant. The present study and literature findings revealed that the frequency of evening types is not clearly elevated in depression, but morning types are less frequent compared to healthy samples (p < 0.001). Morningness-eveningness scores were normally distributed and stable in depressive inpatients. In line with previous findings, but contrary to theoretical assumptions, evening types were not overrepresented in depressed patients. Additionally, relatively less morning types and more intermediate types were found in depressed patients. Future studies should focus on transitions from morning to intermediate types as a tentative risk or correlate of emerging depression.

Daily activity patterns of 2316 men and women from five countries differing in socioeconomic development

Daily rhythmicity in the locomotor activity of laboratory animals has been studied in great detail for many decades, but the daily pattern of locomotor activity has not received as much attention in humans. We collected waist-worn accelerometer data from more than 2000 individuals from five countries differing in socioeconomic development and conducted a detailed analysis of human locomotor activity. Body mass index (BMI) was computed from height and weight. Individual activity records lasting 7 days were subjected to cosinor analysis to determine the parameters of the daily activity rhythm: mesor (mean level), amplitude (half the range of excursion), acrophase (time of the peak) and robustness (rhythm strength). The activity records of all individual participants exhibited statistically significant 24-h rhythmicity, with activity increasing noticeably a few hours after sunrise and dropping off around the time of sunset, with a peak at 1:42 pm on average. The acrophase of the daily rhythm was comparable in men and women in each country but varied by as much as 3 h from country to country. Quantification of the socioeconomic stages of the five countries yielded suggestive evidence that more developed countries have more obese residents, who are less active, and who are active later in the day than residents from less developed countries. These results provide a detailed characterization of the daily activity pattern of individual human beings and reveal similarities and differences among people from five countries differing in socioeconomic development.

Validity of the Japanese version of the Munich ChronoType Questionnaire

To assess circadian preference with a score, the Morningness-Eveningness Questionnaire (MEQ) has been used for more than 3 decades now. More recently, the Munich ChronoType Questionnaire (MCTQ) was developed: it asks for sleep-wake behavior on work and free days and uses the midpoint of sleep on free days (MSF), corrected for sleep debt accumulated during the work week as an indicator of chronotype (MSFsc). In this study, we developed a Japanese version of the MCTQ by using a translation/back-translation approach including an examination of its semantic validity. In a subsequent questionnaire survey, 450 adult men and women completed the Japanese versions of the MCTQ and MEQ. Results showed that MEQ scores were significantly negatively correlated with mid-sleep parameters assessed by the MCTQ, on both, work and free days, as well as with the chronotype measure MSFsc (r = -0.580 to -0.652, all p < 0.001). As in the original German version, the strongest correlation was observed between MEQ score and MSF. A physiological validation study using dim light melatonin onset as a circadian phase marker (N = 37) showed a high correlation between chronotype as assessed with the MSFsc (r = 0.542, p < 0.001), and less so for MEQ score (r = -0.402, p = 0.055). These results demonstrate the validity of the Japanese MCTQ and provide further support of the adequacy of the MCTQ as a chronotype measure.

Personality, cognitive styles and Morningness-Eveningness disposition in a sample of Yoga trainees

Background

Yoga is a psychophysical, spiritual science of holistic living, aiming towards body and mind development; it can influence well-being, cognitive processes, personality (Gunas), psychophysiological parameters, and human health. Since it has been observed that Morningness-Eveningness disposition is associated with personality, and that personality can characterize people practicing Yoga, in this exploratory study we posited that Morningness-Eveningness might be associated with personality in Yoga trainees. Since Yoga can have influences over cognitive perspectives, and since it has been observed that Morningness-Eveningness disposition can associate with cognitive processes, we investigated a sample of Yoga trainees with reference to relationship with styles of learning and thinking (relevant aspects of cognitive functioning) and also with Morningness-Eveningness disposition.

Material/Method

We tested 184 Yoga trainees using the following questionnaires: Styles of Learning and Thinking (Torrance), Big Five Questionnaire (Caprara, Barbaranelli, Borgogni), and reduced Morningness-Eveningness Questionnaire (Natale).

Results

We found that Morning types score significantly higher than Evening types on Conscientiousness, Friendliness, Scrupulousness, Openness to Culture, emotional Stability, emotion Control, they score higher than intermediate types on Conscientiousness, Friendliness, Scrupulousness. Moreover, data showed that the high majority of subjects, also with reference to Morningness-Eveningness disposition, have right-sided styles of learning and thinking, pointing out a tendency towards right-sided cognitive precessing in the whole sample. Personality traits of the Yoga trainees were also investigated.

Conclusions

Data are discussed with reference to existing literature, psychological and neuroscientific perspectives are suggested, previous studies about Yoga published on Medical Science Monitor are also considered.

Integration of biological clocks and rhythms

Animals, plants, and microorganisms exhibit numerous biological rhythms that are generated by numerous biological clocks. This article summarizes experimental data pertinent to the often-ignored issue of integration of multiple rhythms. Five contexts of integration are discussed: (i) integration of circadian rhythms of multiple processes within an individual organism, (ii) integration of biological rhythms operating in different time scales (such as tidal, daily, and seasonal), (iii) integration of rhythms across multiple species, (iv) integration of rhythms of different members of a species, and (v) integration of rhythmicity and physiological homeostasis. Understanding of these multiple rhythmic interactions is an important first step in the eventual thorough understanding of how organisms arrange their vital functions temporally within and without their bodies.

Evening preference is related to the incidence of depressive states independent of sleep-wake conditions

Although evening preference has recently been identified as a risk factor for depression, it has not been substantiated whether evening preference is a direct risk factor for depressive states, or if it is associated secondarily through other factors, such as delayed sleep timing and shortened sleep duration. The objective of this study is to investigate associations in Japanese adult subjects between evening preference and incidence of depressive states, adjusting for various sleep parameters related to depressive states. The Morningness-Eveningness Questionnaire (MEQ), the Pittsburgh Sleep Quality Index (PSQI), and the Center for Epidemiologic Studies Depression Scale (CES-D) were administered to 1170 individuals (493 males/677 females; mean and range 38.5 and 20-59 yrs) to assess their diurnal preferences, sleeping states, and presence of depression symptoms. Subjects were classified into five chronotypes based on MEQ scores. Evening preference was associated with delayed sleep timing, shortened sleep duration, deteriorated subjective sleep quality, and worsened daytime sleepiness. Logistic regression analysis demonstrated that the extreme evening type (odds ratio [OR] = 1.926, p = .018) was associated with increased incidence of depressive states and that the extreme morning type (OR = 0.342, p = .038) was associated with the decreased incidence of depressive states, independent of sleep parameters, such as nocturnal awakening (OR = 1.844, p < .001), subjective sleep quality (OR = 2.471, p < .001), and daytime sleepiness (OR = 1.895, p = .001). However, no significant associations were observed between the incidence of depressive states and sleep duration, sleep timing, and sleep debt (levels of insufficient sleep). Although the findings of this study do not demonstrate a causative relationship between evening preference and depression, they do suggest the presence of functional associations between mood adjustment and biological clock systems that regulate diurnal preference. They also suggest that evening preference might increase susceptibility to the induction of mood disorders.

Depressive symptomatology is influenced by chronotypes

BACKGROUND

Rhythm disturbances are a frequent clinical manifestation of depression. In recent years a possible relationship between depression and chronotypes has emerged. Specifically eveningness has been proposed as vulnerability factor. The aim of this study was to describe sleep features of depressed patients according to chronotypes and to explore possible associations with the clinical features of depressive episodes.

METHODS

100 patients diagnosed with Major Depressive Disorder according to the Mini International Neuropsychiatric Interview (MINI) were included (age: 34+/-11.74, range: 18-60 years; female/male:79/21). At admission the Hamilton Rating Scale for Depression (HRSD) was administered. Patients were also administered the Morningness-Eveningness Questionnaire (MEQ), the Epworth Sleepiness Scale, the Athens Insomnia Scale and the Pittsburgh Sleep Quality Index.

RESULTS

According to MEQ scores patients were classified in three groups: a) eveningness (n=18), b) neither (n=61) and c) morningness type (n=21). The age was different among chronotypes, being morningness-type patients older. The eveningness-type group showed higher scores in suicidal thoughts, more impaired work and activities, higher paranoid symptoms, higher scores on the anxiety cluster (HRSD), while the morningness-type group showed lower proportion of melancholic symptoms (MINI). We did not find association between sleep parameters and specific chronotypes.

LIMITATIONS

The relatively small sample size and the concurrent assessment of chronotypes and depression may have biased our findings.

CONCLUSIONS

Our data suggest the idea that chronotypes have an impact on depressive episodes features, with higher severity for the eveningness-type.

Correlates for poor sleepers in a Los Angeles high school

BACKGROUND AND PURPOSE

We explored sleep patterns including morning-evening preference and their associations with other lifestyle determinants among high school students.

PARTICIPANTS AND METHODS

We conducted a cross-sectional survey of students grades 9-12 from a private high school in the United States. One hundred and thirty-one students completed an online survey comprising 23 original, investigator-created questions, a mood scale, the Pittsburgh Sleep Quality Index (PSQI), and the Horne-Ostberg Morningness-Eveningness Questionnaire (MEQ).

RESULTS

We found that 80% of students reported a sleep deficit. As defined by the PSQI, 69% of girls and 58% of boys in this sample were poor sleepers. Eveningness was a strong predictor of poor sleep, particularly among students aged 15 years (odds ratio [OR] 9.92; 95% confidence interval [CI], 1.52-64.8), among whom poor sleep quality was also associated with a higher body mass index (BMI) (OR, 6.97; 95% CI, 1.01-48.2).

CONCLUSIONS

Our pilot study suggests that morningness-eveningness is a strong predictor of sleep quality among high school students.

Morning and evening personality characteristics in a sample of young Italians

The goal of this study was to investigate associations of morning and evening personality types with personality dimensions in a convenient sample of 60 men and 60 women, ages 18 to 29 years. A short form of the Morningness-Eveningness Questionnaire and a personality questionnaire Come mi vedo (How I see myself), based on the 5-factor model of personality, were given. Several personality dimensions appear to be significantly correlated with Morningness scores: Conscientiousness (positively) and Openmindedness (negatively). The analysis indicated morning types tend to reach their goals resolutely and to plan their steps, they prefer to be precise, tidy, punctual, trustworthy; they have a sense of duty and responsibility; they are also less original and less open to culture and novelties, less curious, conformist, traditionalist, and less well-informed, hardworking, steady, tenacious, and diligent, on the Come mi vedo.

[Sleep patterns of first-year nursing students]

This exploratory and descriptive study aimed at describing sleep patterns of first-year university students at the beginning of their course. The study was conducted at Campinas State University, Brazil. Data were collected in two points of time using Pittsburgh Sleep Quality Index. Results showed that students report sleep of better quality and increased length during vacations, when they kept sleep habits in conformity to chronotype. After classes started a greater number of subjects reported poor sleep quality and daytime lack of enthusiasm. Those changes could be due to the submission of subjects to schedules imposed by the university or to the irregularity of sleep habits assumed. Possible relationship between those sleep-changes and academic performance stresses the importance of ongoing studies on this issue.

Time for sex: nycthemeral distribution of human sexual behavior

Background

Nycthemeral (daily) oscillation has been documented in a variety of physiological and behavioral processes. The present study was carried out to evaluate the existence of a nycthemeral rhythm of human sexual behavior and to identify environmental factors responsible for the rhythmic pattern.

Methods

Non-traditional university students (ages 18 to 51 years) recorded the times of day when they went to sleep, when they woke up, and when they had sex for 3 consecutive weeks. They also answered a questionnaire designed to identify the causes of their selection of time for sex.

Results

The majority of sexual encounters took place at bedtime (11 pm to 1 am). The most common explanations for this temporal pattern were the rigidity of the professional work schedule and family obligations and the availability of the partner, which reduced the opportunity for sexual encounters at other times of the day.

Conclusion

Most sexual encounters take place around bedtime. Although the presence of an endogenous component responsible for this temporal pattern cannot be excluded, the evidence indicates strong environmental forcing, particularly from the work/family schedule of the individuals and from partner availability.

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.

Genetic analysis of morningness and eveningness

We studied the influence of genetic factors on individual differences in morningness-eveningness in a sample of Dutch twin families. Data were collected from adolescent twins (mean age 17.8 yr) and their parents (mean age of fathers 48.0 yr and of mothers 46.0 yr) and a sample of older twins (mean age 46.5 yr). Scores on morningness-eveningness were rated on a 5-point scale. Parents were more morning oriented than their children, and women were more morning oriented than men. With a twin-family study, separation of genetic and environmental influences on variation in morningness-eveningness is possible. Including parents and older twins in the study makes it possible to explore generation differences in these effects. The correlation between monozygotic twins was more than twice the correlation between dizygotic twins. This indicates that genetic effects may not operate in an additive manner. Therefore, a model that included genetic dominance was explored. Biometrical model fitting showed no sex differences for the magnitude of genetic and environmental factors. The total heritability--the sum of additive and nonadditive genetic influences--for morningness-eveningness was 44% for the younger generation and 47% for the older generation. However, the genetic correlation between the generations turned out to be lower than 0.5, suggesting that different genes for morningness-eveningness are expressed in both generations.

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.

Sleep and chronotype for children in Japan

To investigate the change in sleep-wake habits, Morningness-Eveningness preference, and sleep status by grade, 512 students aged from 6 to 18 years, were tested using the Morningness-Eveningness Questionnaire and Sleep Questionnaire. The habitual waking time showed no difference by grade, but the students above Grade 7 reported a significantly later habitual bedtime and had a shorter length of sleep on weekdays than the students below Grade 6. The students above Grade 7 reported a significant difference between habitual and preferred waking times but did not show a difference between habitual and preferred bedtimes. Although the sleep length during weekends became shorter from Grade 1, the sleep length of students above Grade 8 showed a significant difference between the weekdays and weekends; they had more than nine hours of sleep on the weekends. The percentage of students taking a nap during a school lesson significantly increased across Grades 8 to 12. The mean score on the questionnaire decreased across grades and the decrease was significant at Grade 7. Both the habitual and preferred bedtimes and waking times were later from the Morning, Intermediate, to the Evening types across grades. The difference by chronotype in preferred waking time increased for groups from the primary, junior high, to the high school. Also, the sleep lengths both weekdays and weekends decreased from the Morning, Intermediate, to the Evening type for all grades. We suggested that the delay of sleep phase, reduction of sleep length, increased daytime napping, and transition to Evening type were remarkably represented around Grade 7.

Sleep in relation to age, sex, and chronotype in Japanese workers

The Morningness-Eveningness Questionnaire and Life Habits Inventory were administered to 622 Japanese workers matched for sex and age. We investigated the distributions of the scores on the Morningness-Eveningness Questionnaire and sleep-wake habits by age and sex. Subjects were classified into five age groups and three chronotypes. The distributions and mean scores on the questionnaire advanced slightly toward the Morning type from the young to the aged group. The habitual bedtimes and waking times were significantly earlier in all the chronotypes from the young to the aged group, and the preferred bedtimes and waking times were also clearly earlier from the young to the aged group. The length of sleep was shorter for the Evening than the Morning types, especially in the group below 24 yr. The differences in habitual and preferred sleep length were greater than 1 hour for all age groups, especially the two groups under 34 yr. The number of awakenings during night sleep increased from the young to the aged group for all chronotypes. The older Evening type tended more toward frequent napping and longer naptime. The variabilities of bedtime and sleep length were larger for the young and Evening type than for the old group and Morning types. Further, the mood upon waking and satisfaction with sleep length were better in the aged Evening type than the young Morning type. The women under 44 yr. woke up earlier than the men of the same age, and the women of the 35-54 yr. groups had a shorter length of sleep than others. These may be related to childcare and housework. These results indicated that the phase of circadian rhythms had moved forward from the young to the aged group, and the individual's rhythm, of those that were aged Morning types, showed better agreement with sleep-wake rhythms than did others.