Gender differences in morningness–eveningness assessed by self-report questionnaires: A meta-analysis

Role of polygenic risk scores in the association between chronotype and health risk behaviors

BACKGROUND

This study explores the association between chronotypes and adolescent health risk behaviors (HRBs) by testing how genetic background moderates these associations and clarifies the influence of chronotypes and polygenic risk score (PRS) on adolescent HRBs.

METHODS

Using VOS-viewer software to select the corresponding data, this study used knowledge domain mapping to identify and develop the research direction with respect to adolescent risk factor type. Next, DNA samples from 264 students were collected for low-depth whole-genome sequencing. The sequencing detected HRB risk loci, 49 single nucleotide polymorphisms based to significant SNP. Subsequently, PRSs were assessed and divided into low, moderate, and high genetic risk according to the tertiles and chronotypes and interaction models were constructed to evaluate the association of interaction effect and clustering of adolescent HRBs. The chronotypes and the association between CLOCK-PRS and HRBs were examined to explore the association between chronotypes and mental health and circadian CLOCK-PRS and HRBs.

RESULTS

Four prominent areas were displayed by clustering information fields in network and density visualization modes in VOS-viewer. The total score of evening chronotypes correlated with high-level clustering of HRBs in adolescents, co-occurrence, and mental health, and the difference was statistically significant. After controlling covariates, the results remained consistent. Three-way interactions between chronotype, age, and mental health were observed, and the differences were statistically significant. CLOCK-PRS was constructed to identify genetic susceptibility to the clustering of HRBs. The interaction of evening chronotypes and high genetic risk CLOCK-PRS was positively correlated with high-level clustering of HRBs and HRB co-occurrence in adolescents, and the difference was statistically significant. The interaction between the sub-dimensions of evening chronotypes and the high genetic CLOCK-PRS risk correlated with the outcome of the clustering of HRBs and HRB co-occurrence.

CONCLUSIONS

The interaction of PRS and chronotype and the HRBs in adolescents appear to have an association, and the three-way interaction between the CLOCK-PRS, chronotype, and mental health plays important roles for HRBs in adolescents.

Shift work is associated with extensively disordered sleep, especially when working nights

Background

Shift work is generally associated with working and sleeping out of phase with the endogenous, circadian sleep-wake cycle. This exerts detrimental effects on sleep health. The present study aimed at evaluating the presence of short and long sleep as well as sleep disorders within a broad range of shift work schedules and elucidating the role of sociodemographic factors therein.

Methods

A large dataset containing information on sleep was collected through advertisement in a Belgium newspaper (De Standaard). Adult, working individuals were selected (n = 37,662) and categorized based on their work schedule (regular day, early morning, evening, night, and rotating shift). In this cross-sectional study, prevalence rates of short sleep (≤6 h), long sleep (≥9 h) and sleep disorders (screened with Holland Sleep Disorders Questionnaire), and associations between these sleep variables and sociodemographics (age, sex, education, living companion(s)) were analyzed using binominal logistic regression analyses.

Results

In the total sample all sociodemographic factors affected prevalences of short, long and disordered sleep, consistent with previous studies. Compared to day workers, shift workers more frequently reported short sleep, most prominently night workers (26 vs. 50%) (p < 0.001). Furthermore, all sleep disorders as well as sleep disorder comorbidity were more common in shift workers, again most pronounced in night workers (all p < 0.05). In night shift workers the level of education had the strongest associations with disturbed sleep with a two-fold higher prevalence of short and disordered sleep in low relative to academic educated groups (all p < 0.02).

Conclusion

Shift work is related not only to curtailed sleep and shift work disorder, but also to a plethora of sleep disorders, including insomnia, sleep-related breathing disorders and sleep-related movement disorders. Our findings imply that education on coping strategies may be especially important for young and/or lower educated shift workers.

Chronotype characteristics of professional athletes in China: a comprehensive descriptive study

BACKGROUND

Chronotype has gained recognition as a significant factor in enhancing athletic performance. This study aimed to deepen our understanding of athletes' sleep chronotypes and provide a foundation for developing evidence-based training and competition programs. By comprehensively describing and analyzing the chronotype characteristics of Chinese professional athletes, considering individual and sports factors, sleep quality and habits, and mental energy, this research aimed to contribute valuable insights to the field.

METHODS

A sample of 1069 professional athletes from sports teams in Shanghai completed the Athlete Sleep Screening Questionnaire and the Athlete Mental Energy Scale to assess chronotype, sleep quality, sleep-influencing habits, and mental energy.

RESULTS

Among athletes, sleep typology fell within the intermediate range, slightly leaning toward morningness. Male athletes and those who engaged in static sports displayed a greater propensity for morningness. Age correlated with a preference for eveningness. High-level athletes exhibited a stronger inclination toward eveningness. Sleep quality issues were associated with an inclination toward eveningness. Daily caffeine intake and the habit of using electronic devices before bedtime are also linked to eveningness. Chronotype demonstrated the ability to predict various dimensions of athletes' mental energy. It was the strongest predictor of vigor, but the loadings were smaller than those of sleep quality.

CONCLUSION

Chinese athletes' chronotypes primarily exhibit distinct characteristics related to individual factors such as gender, sports discipline, and ranking, as well as habits like caffeine consumption and electronic device use. Moreover, these sleep patterns demonstrate predictive capabilities across all dimensions of athletes' mental energy. This study sheds light on Chinese athletes' unique sleep chronotype attributes, enriching our understanding of sleep patterns among professional athletes under various systems. These insights offer an initial basis for enhancing the effectiveness of athlete scheduling and training management.

Rise and shine for eating right: the link between healthy nutrition and chronotype among young adults

Aim

Many studies have examined the relationship between chronotype and general health. Because healthy eating is the basis of health aim of this study is to evaluate the relationship between healthy nutrition attitudes and chronotype in young adults. Methods: This cross-sectional study was conducted with 1,400 young adults (936 females and 464 males). Chronotype was assessed by the Turkish version of the Morningness-Eveningness Questionnaire (MEQ) and the Attitude Scale for Healthy Nutrition (ASHN) was applied by face-to-face interview. Furthermore, 24-h dietary recall was collected. The scores of nutrient adequacy ratio (NAR) and mean adequacy ratio (MAR) were calculated. The anthropometric measurements including body weight and height were taken.

Results

The chronotype distribution of participants according to the MEQ score and MAR score were not significantly different between females and males (p > 0.05). The percentage of participants with high healthy eating attitude was lowest in the evening chronotype and highest in the morning chronotype (49.7, 37.7 and 25.4% in morning-, intermediate-, evening-types, respectively; p = 0.000 for all groups according to the reciprocal comparisons). There was a positive correlation of the MEQ scores with the scores of ASHN (r = 0.282, p < 0.01). ASHN score was shown to be a predictor for MEQ score (β = 0.280, p = 0.000). Moreover, the score of "poor eating habits" was shown to be highest in the evening chronotype and lowest in the morning chronotype (14.9 ± 3.0 and 13.1 ± 3.0, respectively; p < 0.01).

Conclusion

The results of this study indicate that individuals with the evening chronotype are more deficient in terms of healthy nutrition attitudes. Further studies with larger populations will potentially guide the development of health promotion strategies to prevent and treat chronic diseases based on an individual's chronotype.

Beyond sleep: A multidimensional model of chronotype

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

Morningness-Eveningness and Problematic Online Activities

Online activities and problematic online behaviors have recently emerged as important research topics. However, only a few studies have explored the possible associations between these behaviors and morningness-eveningness. The authors examined whether eveningness predicts these distinct problematic online behaviors differently and directly or via mediators. The associations between eveningness and three different problematic online behaviors (problematic Internet use, problematic online gaming, and problematic social media use) were explored among a large sample of Hungarian young adults (N = 1729, 57.2% female, Mage = 22.01, SDage = 1.97) by using a self-report survey. Depression and the time spent engaging in online activities were assessed as possible mediators. The effects of age and sex were controlled for. Using structural equation modeling, the results supported the association between eveningness and the higher risk for all three problematic online behaviors and highlighted that these associations were mediated by depressive mood and time spent on the activities. In addition, eveningness also predicted PIU directly. Eveningness is a risk factor for problematic online behaviors not only because of the higher amount of time spent on the activities but also because of the worse mood associated with eveningness. The results highlight that it is important to examine the different types of online activity separately and explore the role of diverse risk factors, among them morningness-eveningness.

Factors that influence morningness-eveningness and daytime sleepiness: A cross-cultural comparison of Iranian and Brazilian adolescents

As adolescents get older, they become more evening oriented and, because they are usually expected to wake early to attend school, they often present daytime sleepiness, which is associated with negative outcomes. It is still unclear if this is similar cross-culturally. Here, we studied morningness-eveningness and daytime sleepiness in early adolescence from two different developing nations (Brazil and Iran). A total sample of 697 Iranian and Brazilian early adolescents (9- to 15-year-old; 358 boys) from Tehran, Iran, and São Paulo, Brazil, varying in age and parental schooling (a proxy of socioeconomic status: SES) completed the Morningness-Eveningness Scale for Children (MESC) and the Pediatric Daytime Sleepiness Scale (PDSS) and reported their total sleep time on school nights. They also filled in the Pubertal Developmental Scale to determine their pubertal status. A negligible cross-cultural difference in morningness-eveningness was found, indicating that Brazilians showed a slight circadian-phase delay compared with Iranians throughout all tested ages. There was also seen a very slight increase in phase delay as early adolescents aged, indicative of more eveningness. However, there were no country differences in daytime sleepiness once total sleep time during school nights was controlled for, which was the only factor that affects PDSS scores.

Subjective sleep alterations in healthy subjects worldwide during COVID-19 pandemic: A systematic review, meta-analysis and meta-regression

OBJECTIVE

We conducted a systematic review and meta-analysis to provide an update on sleep quality in different world areas and better characterize subjective sleep alterations during the COVID-19 pandemic. Considering gender distribution and specific pandemic-related parameters, we also intend to identify significant predictors of sleep problems.

METHODS

Six electronic databases were searched from December 2019 to November 2021 for studies investigating sleep during COVID-19 employing the Pittsburgh Sleep Quality Index, the Medical Outcomes Study Sleep, the Insomnia Severity Index or the Epworth Sleepiness Scale. Random-effects models were implemented to estimate the pooled raw means of subjective sleep alterations. Also, we considered the role of several pandemic-related parameters (i.e., days from the first COVID-19 case, government stringency index, new cases for a million people, new deaths for a million people) by means of meta-regression analyses.

RESULTS

A total of 139 studies were selected. The pooled mean of the global Pittsburgh Sleep Quality Index score (PSQI_gen) was 6.73 (95% CI, 6.61-6.85). The insomnia severity index score was reported from 50 studies with a pooled mean of 8.44 (95% CI, 7.53-9.26). Subgroup analyses confirmed that most subcategories had poor sleep quality and subclinical insomnia. Meta-regressions showed that PSQI_gen was predicted by days from the first COVID-19 case and government restrictions with a negative slope and by female gender with a positive slope. The government stringency index was positively correlated with the direct subjective evaluation of sleep quality.

CONCLUSIONS

We found an overall impaired sleep and widespread subthreshold insomnia during the COVID-19 pandemic. The female percentage seems to be the best predictor of impaired sleep quality, consistently to the available literature. Noteworthy, sleep alterations were inversely associated with governmental restrictions and decreased during the pandemic. Our results give a contribution to critically orienting further studies on sleep since COVID-19 pandemic.

Technological infrastructure, sleep, and rest-activity patterns in a Kaqchikel Maya community

Sleep duration, quality, and rest-activity pattern-a measure for inferring circadian rhythm-are influenced by multiple factors including access to electricity. Recent findings suggest that the safety and comfort afforded by technology may improve sleep but negatively impact rest-activity stability. According to the circadian entrainment hypothesis, increased access to electric lighting should lead to weaker and less uniform circadian rhythms, measured by stability of rest-activity patterns. Here, we investigate sleep in a Maya community in Guatemala who are in a transitional stage of industrialization. We predicted that (i) sleep will be shorter and less efficient in this population than in industrial settings, and that (ii) rest-activity patterns will be weaker and less stable than in contexts with greater exposure to the natural environment and stronger and more stable than in settings more buffered by technologic infrastructure. Our results were mixed. Compared to more industrialized settings, in our study population sleep was 4.87% less efficient (78.39% vs 83.26%). We found no significant difference in sleep duration. Rest-activity patterns were more uniform and less variable than in industrial settings (interdaily stability = 0.58 vs 0.43; intradaily variability = 0.53 vs 0.60). Our results suggest that industrialization does not inherently reduce characteristics of sleep quality; instead, the safety and comfort afforded by technological development may improve sleep, and an intermediate degree of environmental exposure and technological buffering may support circadian rhythm strength and stability.

The Effect of Chronotype on Addictive Eating Behavior and BMI among University Students: A Cross-Sectional Study

The aim of this study was to examine the effect of chronotype on addictive eating behavior and BMI in university students. A questionnaire on their sociodemographic characteristics and eating habits, as well as the three-factor eating questionnaire (TFEQ) and the morningness-eveningness questionnaire (MEQ), were given to students at Üsküdar University. Data were analyzed with IBM SPSS 26.0. This study included a total of 850 students, 46.8% of whom were male and 53.2% were female. The mean BMI was 22.94 ± 3.30 kg/m2. As the BMI values of students increased, there was a decrease of 25.6% in the TFEQ scores, regardless of gender (s = −0.256; p < 0.001), and an increase of 10.6% in their chronotype scores, meaning that the students tended to be morning types (s = 0.106; p < 0.01). A significantly negative, very weak correlation was found between the students’ TFEQ and MEQ scores (s = −0.123; p < 0.001). The students’ BMI (p < 0.01) and TFEQ scores (p < 0.001) were affected by their MEQ scores in a statistically significant way. It was found that each 1-point increase in the MEQ score led to a 4.0% increase in the BMI score and a 15.8% decrease in the TFEQ score. It was observed that the morning-type students tended to be obese in terms of their BMI, and these students demonstrated fewer addictive eating behaviors.

Investigation of the relationship between chronotype, learning style and academic achievement of university students during distance education in the pandemic period

The purpose of this study was to investigate the relationship between chronotype, learning style, and academic achievement. The study sample consisted of 1884 volunteer undergraduate students from 58 different universities across Turkey. The data were collected online during distance education because of the Covid-19 pandemic. Turkish version of Morningness-Eveningness Questionnaire (MEQ) and Big16 Learning Modality Inventory were used for data collection. The correlation between chronotype and cumulative grade point average (CGPA) scores was analyzed using Spearman's rho, and differences among the chronotypes were analyzed with Kruskal-Wallis test. Chi-square tests with pairwise z-test were used to analyze the relationships between the participants' learning style preferences and chronotypes. Also, ANCOVA analyses were performed to evaluate the interactions of gender × chronotype and gender × learning style on CGPA scores. The results revealed that participants' preference for visual and auditory styles differed by chronotype. Visual learning style was more dominant among morning (M) types, while auditory style was more dominant among evening (E) types. However, the most preferred learning style was visual, followed by auditory and kinesthetic styles for all chronotypes. No relationship was found between chronotype and academic achievement. The CGPA scores of the participants with kinesthetic learning style were lower than the participants with auditory and visual learning styles. The female participants had higher CGPA score than males. However, the CGPA scores did not differ for both male and female participants with different chronotype and learning style preferences. From the results, we suggest that academic achievement can be enhanced by consideration of students' learning style preferences for all chronotypes.

Human chronotype: Comparison of questionnaires and wrist-worn actigraphy

In this work, we investigated the accuracy of chronotype estimation from actigraphy while evaluating the required recording length and stability over time. Chronotypes have an important role in chronobiological and sleep research. In outpatient studies, chronotypes are typically evaluated by questionnaires. Alternatively, actigraphy provides potential means for measuring chronotype characteristics objectively, which opens many applications in chronobiology research. However, studies providing objective, critical evaluation of agreement between questionnaire-based and actigraphy-based chronotypes are lacking. We recorded 3-months of actigraphy and collected Morningness-Eveningness Questionnaire (MEQ), and Munich Chronotype Questionnaire (MCTQ) results from 122 women. Regression models were applied to evaluate the questionnaire-based chronotypes scores using selected actigraphy features. Changes in predictive strength were evaluated based on actigraphy recordings of different duration. The actigraphy was significantly associated with the questionnaire-based chronotype, and the best single-feature-based models explained 37% of the variability (R²) for MEQ (p < .001), 47% for mid-sleep time MCTQ-MSFsc (p < .001), and 19% for social jetlag MCTQ-SJLrel (p < .001). Concerning stability in time, the Mid-sleep and Acrophase features showed high levels of stability (test-retest R ~ 0.8), and actigraphy-based MSFsc_acti and SJLrel_acti showed high temporal variability (test-retest R ~ 0.45). Concerning required recording length, features estimated from recordings with 3-week and longer observation periods had sufficient predictive power on unseen data. Additionally, our data showed that the subjectively reported extremes of the MEQ, MCTQ-MSFsc, and MCTQ-SJLrel are commonly overestimated compared to objective activity peak and middle of sleep differences measured by actigraphy. Such difference may be associated with chronotype time-variation. As actigraphy is considered accurate in sleep-wake cycle detection, we conclude that actigraphy-based chronotyping is appropriate for large-scale studies, especially where higher temporal variability in chronotype is expected.

Association between Chronotype and Nutritional, Clinical and Sociobehavioral Characteristics of Adults Assisted by a Public Health Care System in Brazil

Chronotype (CT) has been associated with predisposition to chronic noncommunicable diseases (CNCDs), such as diabetes mellitus and obesity. However, the effects of CT on individuals assisted by public health systems (PHSs) in middle-up economies are still poorly explored. The objective of this study was to evaluate the relationship between CT and clinical, sociobehavioral and nutritional aspects in adults assisted by a PHS in Brazil. This is a population-based cross-sectional study. The sample consisted of 380 individuals, selected through probabilistic sampling by clusters, in all health units in a city of approximately 100 thousand inhabitants. Data collection was performed during home visits, by means of general and nutritional interviews, anthropometric measurements and the Morningness-Eveningness Questionnaire (MEQ). Statistical analysis comprised chi-square test and principal component analysis (CPA) followed by Fisher's discriminant analysis to determine aspects associated with each CT (morning, evening or intermediate). With the aim of explaining the variation in the CT scores, the consumption of micronutrients (corrected to the total energy intake) and other individual and sociodemographic variables were used as explanatory factors in the adjustment of a linear regression model. The morning group was characterized by older men, with less than eight years of schooling, with low body mass index (BMI) and with low intake of omega-6, omega-3, sodium, zinc, thiamine, pyridoxine and niacin. The evening group, on the other hand, was composed of younger individuals, with a high consumption of these same nutrients, with high BMI and a higher frequency of heart diseases (p < 0.05). It was concluded that most morning CT individuals were elderly thin males with lower consumption of omega-6 and -3, sodium, zinc, thiamine, pyridoxine and niacin, whereas evening individuals were younger, had higher BMI and had higher consumption of the studied micronutrients. The identification of circadian and behavioral risk groups can help to provide preventive and multidisciplinary health promotion measures.

Circadian preference and intelligence - an updated meta-analysis

A large number of previous studies reported a link between circadian preference and psychometric intelligence with mixed results and various hypotheses about the source of this correlation. In this study, we aimed to update a previous meta-analysis about the correlation between circadian preference and intelligence. Our literature search identified a large number of new studies, resulting in an increase of over 100% in the number of studies and over 400% in the number of involved participants (total k = 30, total N = 11160) over the previous meta-analysis, sampling a much wider age range from children to adults in late middle age. Our meta-analysis revealed no significant link between morningness and intelligence (r = -0.008) when the entire sample was studied, and no evidence for publication bias. This overall effect, however, obscured the moderating effect of age. The morningness-intelligence correlation decreased with mean sample age (R² = 54%), ranging from a non-significant positive trend in children and adolescents to a significant negative correlation after young adulthood. Eveningness was positively correlated with intelligence (r = 0.056), but this finding is based on a more age-restricted sample and only reached significance with some model specifications. We hypothesize that the age-moderated correlation between circadian preference and intelligence reflects social effects, where more intelligent individuals are more able to adjust their daily schedules to their natural circadian rhythm.

COVID-19 lockdown and poor sleep quality: Not the whole story

A growing body of evidence consistently describes the side‐effects of coronavirus disease 2019 lockdown on mental health and sleep quality. We conducted a longitudinal web‐based survey of 217 Italian participants at two time points: lockdown and subsequent follow‐up. To thoroughly investigate lockdown‐related changes in sleep quality, we first evaluated variations in overall sleep quality assessed by the Pittsburgh Sleep Quality Index. We then examined sleep changes in specific components of sleep quality. Results revealed a clear dissociation of sleep effects, as a function of the specific domain considered, with longer sleep latency, worse sleep efficiency, and massive sleep medication use during forced confinement. On the other hand, we simultaneously observed an increased sleep duration and better daytime functioning. Our present findings highlight the importance of an accurate examination of sleep quality during lockdown, as the effects were not uniform across populations and different sleep domains.

The nature of night eating syndrome: Using network analysis to understand unique symptomological relationships

OBJECTIVES

Despite the initial characterization of night eating syndrome (NES) in 1955, the definition and operationalization of its symptoms has varied considerably. To standardize the definition of NES and its symptoms, Allison et al. developed research diagnostic criteria. Even so, conceptualization and intervention of NES remains guided by medical models, which assume that pathology is driven by a distinct, underlying causal mechanism. Conversely, recent work on other eating disorders (EDs) has used network analysis to reconceptualize ED psychopathology and treatment by identifying (a) unique relationships between key symptoms, and (b) the symptoms most central to specific EDs. The present study examined NES symptoms through network analysis to identify the most central symptoms within the NES network.

METHOD

Regularized partial correlation networks were estimated using 144 individuals in a community sample diagnosed with NES. Participants completed semi-structured interviews, self-report measures, and food/sleep diaries to measure NES symptoms, nonspecific health domains (e.g., sleep disturbance, overall mood, stress, and circadian rhythm functioning), and transdiagnostic ED symptoms.

RESULTS

Depressed mood, poor sleep quality, and a strong urge to eat upon awakening at night were highly central to the psychopathology network for NES and were significantly more central than most other NES symptoms and nonspecific health domains.

DISCUSSION

This study provides insight on the unique symptomological relationships of NES and sets the stage for future work that can identify causal linkages among NES symptoms. These symptoms represent key elements of the core psychopathology of NES and should represent primary targets for intervention.

Chronotype patterns associated with job satisfaction of shift working healthcare providers

Job satisfaction of healthcare providers is important for their own health and also the quality of care provided to their patients. The aim of our study was to measure the chronotype patterns among healthcare providers and its association with their job satisfaction. Using stratified cluster random sampling, we recruited 210 healthcare providers working permanent morning or evening shifts for a cross-sectional study in Sari, Iran. By in-person interview, we collected data on demographic characteristics and assessed both chronotype, using the Horne-Östberg M-E Questionnaire, and job satisfaction, using the Danet's Job Satisfaction Questionnaire. We grouped job satisfaction scores into four ordinal categories and assessed correlations with study variables by ordinal multivariate logistic regression. The average age of the participants was 39.0 (SD 8.02) years. Most were younger than 45 years of age (74.27%), female (66.67%), married (62.24%), of high income (45.71%), and employed in permanent full-time healthcare work (56.67%). Overall, 63.4% of the participants had moderately high to high job satisfaction. Those who worked the morning shift who were moderate morning and high morning chronotypes, compared to those who were intermediate chronotype, had a statistically significant adjusted odd ratio (AOR), respectively, of 11.36 and 6.53 of higher job satisfaction. Likewise, those who worked the evening shift and were moderate evening and high evening chronotype, compared to intermediate chronotype, had a statistically higher AOR of job satisfaction, respectively, 3.44 and 32.63. We found the match between chronotype and work shift schedule to be linked with increased job satisfaction. If the findings are verified in other investigations, the relatively easy measure of chronotype should be considered to assign people to a work shift to improve job satisfaction of healthcare and perhaps other workers.

Relationship Between Big Five Personality Dimensions, Chronotype, and DSM-V Personality Disorders

Morningness-eveningness (M/E) is an important variable in individual differences and has an impact on many areas of life including general and mental health. In previous work eveningness has shown to correlate to personality disorders (PDs) and mental instability such as psychoticism, depression, and bipolar disorders. Therefore, a relationship between M/E and PDs can be assumed but has never been tested. The aim of this study was to assess a possible relationship between DSM-5-PDs and circadian timing (chronotype; M/E). We used the Morningness-Eveningness Stability Scale improved and clock time-based measurements, the PID-5 brief version, and the Big Five brief version. Sample: N = 630; mean age: 27.76 years, SD: 11.36 years; 137 male, 489 female, 4 diverse. In this short screening a relationship between eveningness and DSM-5-personality traits, (evening-oriented participants showing a higher PID-5 score: morningness -0.208/p < 0.001; eveningness: 0.153/p < 0.001) was found. Moreover, participants with high levels of distinctness (fluctuations of the perceived energy level during the day) are prone to PDs too, with distinctness being the best predictor for a high PID-5 score in this sample (0.299/p < 0.001). In the regression analysis, neuroticism, agreeableness, conscientiousness, and extraversion contributed significantly to the model with higher scores on extraversion, agreeableness and conscientiousness being related to lower scores on the PID-5. Neuroticism was positively related to PID-5 scores. Later midpoint of sleep (higher eveningness) was associated with higher PID-5 scores, as were higher fluctuations/amplitude during the day.

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.

Circadian Typology and Personality Dimensions of Croatian Students of Health-Related University Majors

The aim of this study was to determine the relationship between circadian preferences and personality dimensions among 712 students of three different majors from the Faculty of Medicine, Osijek: medical students (MD), nursing students (RN) and medical laboratory diagnostics students (MLD). For the measurement of personality dimensions, the IPIP50 Big-Five questionnaire was used. The circadian preference of students was assessed using the reduced morningness-eveningness questionnaire (rMEQ). Several significant results were observed and there was a significant difference in circadian preference among the three tested groups, with RN students scoring highest on the morningness scale and MLD students scoring the lowest. RN students scored significantly higher on agreeableness and conscientiousness than the other two groups. On the other hand, MD students scored higher on intellect than the MLD students. MLD students scored the lowest on emotional stability scales. Morning type students had higher conscientiousness and emotional stability scores. These results imply that circadian preference and personality traits are crucial elements of medical professionals' wellbeing. With this paper, we would like to raise awareness about common personality traits and adherence to certain circadian orientations in medical professionals as a motivation to introduce a more flexible view towards strict time and task divisions in everyday practice.

Composite Scale of Morningness: Psychometric properties, validity with Munich ChronoType Questionnaire and age/sex differences in Poland

The present study aimed at testing psychometric properties of the Composite Scale of Morningness (CSM) and validating it with mid sleep on free days (MSF) derived from the Munich ChronoType Questionnaire (MCTQ) in Poland, along with analyzing age and sex differences in the CSM and MSF. A sample of 952 Polish residents (62.6% females) aged between 13 and 46 was tested. Additionally, a sample of 33 university students were given MCTQ and filled in a sleep diary for 8 days. MSF derived from MCTQ was related to the one from sleep diary (r = .44). The study revealed good reliability of the CSM (α = .84) and its validity: greater morningness preference was associated with earlier MSF from MCTQ (r = –.52). CSM scores were distributed over its full range, with a mean of 34, and did not differ between sexes, although females were earlier than males by 23 minutes in MSF. Regarding age, eveningness estimated with both CSM and MSF was greatest in subjects aged 16–18 years, and a shift toward eveningness during puberty and a shift back toward morningness in older age was observed. The Polish version of the CSM consisted of two components of morningness. Cutoff scores were: for evening types (lower 10%) 24 or less, for morning types (upper 10%) 43 or more. The Polish CSM presents good psychometric properties, which are similar to those reported in other language versions, and also presents sex/age patterns similar to those found previously.

Associations between the Chronotypes and Eating Habits of Hong Kong School-Aged Children

Later chronotypes have been found to be associated with unhealthy diets in adolescents and adults, but no study has been conducted in children. The aim of this study was to investigate the associations between the chronotypes and dietary patterns of school-aged children. Children aged 7–11 and their parents were recruited from five mainstream schools in Hong Kong. The parents were told to complete questionnaires on the children’s circadian preferences, food frequency, and dietary behaviors. All of the questionnaires were distributed and collected by schoolteachers. No gender differences in chronotype were observed (all p > 0.05). The evening-type was associated with significantly greater odds of viewing television (TV) during meals (adjusted odds ratios (OR) = 5.62 in boys and 5.39 in girls). Evening-oriented boys were prone to skipping breakfast (adjusted OR = 14.78), whereas evening-oriented girls were at risk of consuming fast food (adjusted OR = 7.74). There are indications of some gender differences in chronotype-related eating patterns. Sleep duration and screen time significantly mediated the associations between later chronotypes and unhealthy eating habits. Individualized dietary recommendations in accordance with circadian preferences may be effective at promoting healthy and nutritious diets for school-aged children.

Chronotype, Social Jet Lag, and Cardiometabolic Risk Factors in Early Adolescence

IMPORTANCE

Inadequate sleep duration and quality increase the risk of obesity. Sleep timing, while less studied, is important in adolescents because increasing evening preferences (chronotypes), early school start times, and irregular sleep schedules may cause circadian misalignment.

OBJECTIVE

To investigate associations of chronotype and social jet lag with adiposity and cardiometabolic risk in young adolescents.

DESIGN, SETTING, AND PARTICIPANTS

Starting in 1999, Project Viva recruited pregnant women from eastern Massachusetts. Mother-child in-person visits occurred throughout childhood. From January 23, 2012, to October 16, 2016, 804 adolescents aged 12 to 17 years completed 5 days or more of wrist actigraphy, questionnaires, and anthropometric measurements. A cross-sectional analysis using these data was conducted from April 31, 2018, to May 1, 2019.

EXPOSURES

Chronotype, measured via a continuous scale with higher scores indicating greater evening preferences, and social jet lag, measured as the continuous difference in actigraphy sleep midpoint in hours from midnight on weekends vs weekdays, with higher values representing more delayed sleep timing on weekends.

MAIN OUTCOMES AND MEASURES

Adiposity, measured via anthropometry and dual-energy x-ray absorptiometry. For a subset of 479 adolescents with blood samples, cardiometabolic risk scores were computed as the mean of 5 sex- and cohort-specific z scores for waist circumference, systolic blood pressure, inversely scaled high-density lipoprotein cholesterol, and log-transformed triglycerides and homeostatic model of insulin resistance.

RESULTS

Among the 804 adolescents in the study, 418 were girls and 386 were boys, with a mean (SD) age of 13.2 (0.9) years. In multivariable models adjusted for age, puberty, season, and sociodemographics, associations of chronotype and social jet lag with adiposity varied by sex. For girls, greater evening preference was associated with a 0.58-cm (95% CI, 0.12-1.03 cm; P = .04 for interaction) higher waist circumference and 0.16 kg/m2 (95% CI, 0.01-0.31 kg/m2; P = .03 for interaction) higher fat mass index as measured by dual-energy x-ray absorptiometry; each hour of social jet lag was associated with a 1.19-cm (95% CI, 0.04-2.35 cm; P = .21 for interaction) higher waist circumference and 0.45 kg/m2 (95% CI, 0.09-0.82 kg/m2; P = .01 for interaction) higher fat mass index as measured by dual-energy x-ray absorptiometry. Associations of social jet lag and evening chronotypes persisted for many measures of adiposity after adjustment for sleep duration and other lifestyle behaviors. By contrast, no associations were observed in boys. There were no associations with the cardiometabolic risk score for either sex, although statistical power was low for this outcome.

CONCLUSIONS AND RELEVANCE

Evening chronotypes and social jet lag were associated with greater adiposity in adolescent girls but not adolescent boys. Interventions aimed at improving sleep schedules may be useful for obesity prevention, especially in girls.

Eveningness is associated with greater subjective cognitive impairment in individuals with self-reported symptoms of unipolar depression

BACKGROUND

Eveningness is associated with depression diagnosis and increased depressive symptom severity. Time-of-day preference has been linked with differences in cognitive function in the general population, with cognitive difficulties being a major factor in psychosocial impairment in depression. We therefore investigated the impact of time-of-day preference and self-reported depressed state on subjective cognitive function.

METHODS

Participants over the age of 18 with a self-reported history of depression completed an online questionnaire. They provided demographic and mental health information, and completed self-report scales assessing depression symptoms, time-of-day preference, and cognition. Participants were classified as "currently" or "previously depressed" based on self-reported symptoms, and as having a morning, neither, or evening time-of-day preference.

RESULTS

A total of 804 participants reporting a history of unipolar depression were included. Currently-depressed participants reported more cognitive difficulties in all areas measured. Evening types reported more complex attentional and retrospective memory difficulties than neither types, and reported more executive and prospective memory difficulties than both neither and morning types. There was an additive effect of mood state and time-of-day preference, with self-reported depressed evening types reporting the most cognitive problems.

LIMITATIONS

Depression history, time-of-day preference, and cognitive function were assessed using unsupervised self-report measures. Time-of-day preference does not necessarily reflect the physiological circadian system.

CONCLUSIONS

Both depressed state and evening preference were individually associated with subjective cognitive complaints in people with a self-reported history of unipolar depression. The additive effect of poor mood and eveningness is important given the high prevalence of eveningness in depression. Assessment of time-of-day preference could help to identify those susceptible to cognitive symptoms, and inform treatment.

Validity and reliability of the Slovene version of the Morningness-Eveningness Questionnaire

Morningness-eveningness (ME) can be defined as individual differences in sleep-wake patterns, and the time of day people feel and perform best. Various self-report instruments that measure ME have been developed. The Horne and Östberg Morningness-Eveningness Questionnaire (MEQ) has most frequently been used for classifying ME types. The aim of this study was to investigate the validity and reliability of the Slovene version of the MEQ (Slovene MEQ). Two hundred and sixty-five participants (65.3% women, 34,7% men, mean age 38,1 years, range 19-67) took the Slovene MEQ twice, 2 weeks apart (MEQ test and retest). Internal consistency of the Slovene MEQ items was high, with Cronbach's Alpha coefficients of 0.86. The test-retest reliability was also high, with intraclass correlation coefficient (ICC) of 0.96. The classification of chronotypes on middle-aged population offered a more balanced representation of the five chronotypes than those proposed by the authors Horne and Östberg . Age changes in chronotype could be confirmed in this study in the supposed direction with older adults being more morning-oriented. The criterion validity of the Slovene MEQ through the relationship of morningness and basic personality traits showed that conscientiousness and agreeableness demonstrated positive and significant correlations with morningness. A low negative correlation was observed between openness and morningness, with higher eveningness among more open participants.

An epidemiological study of sleep-wake timings in school children from 4 to 11 years old: insights on the sleep phase shift and implications for the school starting times' debate

OBJECTIVE

It has been assumed that during adolescence there is a strong shift toward eveningness chronotype, whereas children's sleep is relatively stable. Several studies have focused on the conflict between school start times and adolescents' circadian rhythms; however, fewer studies have been conducted in younger children. The aim of this study was to examine sleep durations, schedules, and sleep phase shift in preschool- and school-aged children.

METHODS

Data for sleep patterns on school days and free days (ie, days when children's sleep-wake patterns were free from any influence of individual or family activities) was obtained by means of questionnaires (Children ChronoType Questionnaire) for 3155 Portuguese children 4-11 years of age.

RESULTS

As children grew older and school grade level increases, we found later bedtimes and sleep onsets on both school days and free days; and later wake times only on free days. By contrast, wake times were progressively earlier, imposed by school start times. There was a progressive reduction in the amount of sleep on school nights as grade level increased. Greater social jetlag, later midpoint of sleep, and higher restriction-extension patterns were found across age groups.

CONCLUSION

The displacement of bed and wake times for later hours on free days starts at an early age. Changing early school start times could adjust social demands to the biological rhythm of children.

Reproductive Success, Relationship Orientation, and Sexual Behavior in Heterosexuals: Relationship With Chronotype, Sleep, and Sex

Following previous studies, chronotype was related to sexual attitudes and behavior. Evening people tend to be more promiscuous and follow short-term mating strategies and extra-pair matings (EPM), which might lead to a higher reproductive success. In this study, one aim was to assess reproductive success directly by asking for children, and, second, to obtain a higher sample size for the analysis of sexual behavior and chronotype than in previous studies. N = 1,843 heterosexual persons (551 men, 1,288 women, 4 without data) responded to our online survey. Five hundred fifty-nine persons were single and 1,281 in a relationship; 203 reported having children (1.9 ± 0.81). Age was positively related and age at first intercourse was negatively related to the number of children. People being later chronotypes had fewer children, and shorter sleep duration was linked with more children. Extroversion was correlated with number of children, as was the long-term relationship orientation. Sociosexual orientation and EPM were unrelated to number of children. Age at first intercourse was earlier in evening people, and unrestricted sociosexuality was higher in late chronotypes. Morning orientation correlated with long-term relationship orientation and eveningness with short-term relationship orientation. Number of sexual partners was lower in morning people. Men were more evening oriented, later chronotypes, and slept shorter. There were no differences in sociosexual behavior, but men were less restricted in attitude and desire. Men scored higher on short-term relationship orientation and women higher on long-term relationship orientation. This study confirmed previous results about chronotype and sexual behavior but provided the first evidence that morningness was related to higher reproductive success.

Social Jetlag and Chronotypes in the Chinese Population: Analysis of Data Recorded by Wearable Devices

Background

Chronotype is the propensity for a person to sleep at a particular time during 24 hours. It is largely regulated by the circadian clock but constrained by work obligations to a specific sleep schedule. The discrepancy between biological and social time can be described as social jetlag (SJL), which is highly prevalent in modern society and associated with health problems. SJL and chronotypes have been widely studied in Western countries but have never been described in China.

Objective

We characterized the chronotypes and SJL in mainland China objectively by analyzing a database of Chinese sleep-wake pattern recorded by up-to-date wearable devices.

Methods

We analyzed 71,176 anonymous Chinese people who were continuously recorded by wearable devices for at least one week between April and July in 2017. Chronotypes were assessed (N=49,573) by the adjusted mid-point of sleep on free days (MSFsc). Early, intermediate, and late chronotypes were defined by arbitrary cut-offs of MSFsc <3 hours, between 3-5 hours, and >5 hours. In all subjects, SJL was calculated as the difference between mid-points of sleep on free days and work days. The correlations between SJL and age/body mass index/MSFsc were assessed by Pearson correlation. Random forest was used to characterize which factors (ie, age, body mass index, sex, nocturnal and daytime sleep durations, and exercise) mostly contribute to SJL and MSFsc.

Results

The mean total sleep duration of this Chinese sample is about 7 hours, with females sleeping on average 17 minutes longer than males. People taking longer naps sleep less during the night, but they have longer total 24-hour sleep durations. MSFsc follows a normal distribution, and the percentages of early, intermediate, and late chronotypes are approximately 26.76% (13,266/49,573), 58.59% (29,045/49,573), and 14.64% (7257/49,573). Adolescents are later types compared to adults. Age is the most important predictor of MSFsc suggested by our random forest model (relative feature importance: 0.772). No gender differences are found in chronotypes. We found that SJL follows a normal distribution and 17.07% (12,151/71,176) of Chinese have SJL longer than 1 hour. Nearly a third (22,442/71,176, 31.53%) of Chinese have SJL<0. The results showed that 53.72% (7127/13,266), 25.46% (7396/29,045), and 12.71% (922/7257) of the early, intermediate, and late chronotypes have SJL<0, respectively. SJL correlates with MSFsc (r=0.54, P<.001) but not with body mass index (r=0.004, P=.30). Random forest model suggests that age, nocturnal sleep, and daytime nap durations are the features contributing to SJL (their relative feature importance is 0.441, 0.349, and 0.204, respectively).

Conclusions

Our data suggest a higher proportion of early compared to late chronotypes in Chinese. Chinese have less SJL than the results reported in European populations, and more than half of the early chronotypes have negative SJL. In the Chinese population, SJL is not associated with body mass index. People of later chronotypes and long sleepers suffer more from SJL.

Gender differences in chronotype diminish with age: a meta-analysis based on morningness/chronotype questionnaires

Chronotype is an individual difference trait that is closely linked to biological variables. Usually, men and women differ in their chronotype with men being more evening oriented than women. The aim of the study was to assess gender differences in chronotype based on a systematic review and meta-analysis. In addition, many recent studies do not report gender differences any more although researchers collected data on men and women. This motivated us to contact many researchers directly to obtain and use these additional data. We included 164 studies giving 201 effect size measures in a data set, which only included the most commonly used questionnaires (MEQ, rMEQ and CSM) totaling 186,289 participants in total, of which 75,622 were men and 110,667 were women. We calculated an effect size of the standardized mean difference of -0.072 (95% CI from -0.062 to -0.082) in the fixed effects and of -0.066 (95% CI from -0.043 to- 0.089) in the random effects model. Men were on average more evening oriented than women. Type of questionnaire did not influence the standardized mean difference in chronotype between genders. Mean age, standard deviation of age and publication year (p ≤ 0.05) were found to have significant effects on the standardized mean difference in chronotype between genders. The standardized mean difference in chronotype between genders is predicted to change from negative to positive with increasing mean age (young women were more morning orientated than young men, but older women were less morning orientated than older men). This suggests that the differences between men and women diminish with time. The standardized mean difference in chronotype between genders is decreasing with increasing publication year, as well as with high variation in age of the samples. Abbreviations: CSM: Composite Scale of Morningness (Smith et al. 1989); MEQ: Morningness-Eveningness Questionnaire (Horne and Ostberg, 1976); rMEQ: reduced Morningness-Eveningness Questionnaire (Adan & Almiral, 1991); SMD: standardized mean difference (measure of effect size).

Working Time Society consensus statements: Individual differences in shift work tolerance and recommendations for research and practice

There is no standard definition of shift work universally, and no validated report of complete biological adjustment to shift work in workers. Similarly, the evidence for shift work tolerance is limited due to a small number of studies and a narrow range of outcome measures. This paper discusses evidence to date regarding individual differences in shift work tolerance and highlights areas for future research and recommendations for workplace practice. The few factors that are consistently associated with perceived or actual shift work tolerance are young age, low scores of morningness or being a late chronotype, low scores of languidity and neuroticism, high scores on extraversion, internal locus of control and flexibility and male sex. An important first step is to differentiate between factors that are potentially modifiable, such as those that are determined by lifestyle choices, and those factors specific to the working time arrangement. Identifying determinants of shift work tolerance and the ability to adjust to shift work, whether they are innate and/or acquired mechanisms, is important so workers who are less likely to tolerate shift work well can be self-identified and supported with appropriate harm/risk minimization strategies. This paper also identifies important areas for future research with the goal of increasing the evidence base on which we can develop evidence-based harm mitigation strategies for shift workers.

Factorial Structure of the Morningness-Eveningness-Stability-Scale (MESSi) and Sex and Age Invariance

Assessing morningness-eveningness preferences (chronotype), an individual characteristic that is mirrored in daily mental and physiological fluctuations, is crucial given their overarching influence in a variety of domains. The current work aimed to investigate the best factor structure of an instrument recently presented to asses this characteristic: the Morningness-Eveningness-Stability-Scale improved (MESSi). For the first time, the originally proposed three-factor structure was pitched against a uni- and a two-factor solution. Another novelty was to establish that the best-fitting model would be invariant in relation to sex and age, two variables that influence chronotype. A Confirmatory Factor Analyses on the data obtained from a sample of 2096 German adults (age: 18–76; M = 25.5, SD = 7.64) revealed that the originally proposed three-factor structure of the MESSi – Morning Affect, Eveningness, and Distinctness – was the only one to achieve acceptable fit indicators. Furthermore, each scale obtained good internal consistency. In order to assess age invariance, following the literature on development and chronotype, our sample was divided into three age groups: 18–21 years, 22–31 years, and 32 years or older. Full measurement invariance of the three-factor model was found for sex and age. Regarding differences between sexes, females did not differ significantly from males in Morning Affect, but scored significantly lower on Eveningness and higher on Distinctness; this last result has been consistent across validation studies of the MESSi. With respect to age differences, the oldest group scored lower on Eveningness and Distinctness in comparison with the other two age-groups; the intermediate group (age: 22–31) scored lower on Morning Affect when compared to both the younger and older age groups. Additionally, both Eveningness and Distinctness were negatively correlated with age. This latter relation has been consistently reported in other validation studies. Our results reinforce the idea that the MESSi assesses three different components of chronotype in a reliable manner and that this instrument can be used to explore sex and age differences.

Psychometric properties of a Japanese version of Composite Scale of Morningness

This study aimed to assess the factor structure and validity of the Composite Scale of Morningness (CSM) in Japanese samples. A sample of 348 Japanese university students (196 men, 152 women) and 170 adults from the community (50 men, 120 women) completed a questionnaire including the CSM, the Diurnal Type Scale (DTS) and questions regarding sleeping and waking times. Four measurement models were compared, and a two-factor measurement model with Morningness/Time of day preference (α = 0.78) and Morning Affect/Alertness (α = 0.80) factors yielded the closest fit. Both Morningness/Time of day preference and Morning Affect/Alertness were positively correlated with DTS score. Morningness/Ttime of day preference was negatively correlated with the midpoint of sleep on weekdays and free days. The measurement model was invariant across the university and community groups. The community group, which was older, was characterized by greater morningness. The results provide evidence of the validity of the Japanese CSM, thus opening up the possibility of including Japanese samples in cross-cultural research on morningness.

Is Santa Claus an evening owl?

Case studies have a long tradition in biomedical research. Here, I will analyze an important person from a chronobiological aspect, Santa Claus. Although it might be dangerous for researchers to publish analyses about Santa Claus, because, given the possibility that he may be unsatisfied with my analysis, this could lead to an embargo of parcels for my whole family. Nevertheless, some intrepid researches already diagnosed Santa Claus, ending up in some important research results. A search in Web of Science revealed only N = 224 publications about Santa Claus, which is really low. The question, I am addressing here is, whether Santa Claus is an "evening owl" or a night chronotype. In this report, I summarize the facts known about Santa Claus on the one side and about evening chronotypes on the other and sum up these results in a "vote counting" manner as pros and cons. The results are summarized in Table 1. In total, there is 12 times support for the hypothesis, 2 times against and 1 equivocal (Table 1). This result is significant (binomial test, p = 0.013). Therefore, the conclusion is "Santa Claus is an evening type".

Exercise as a reward: Self-paced exercise perception and delay discounting in comparison with food and money

Exercise is an important health behavior. Expressed reasons for participation are often delayed outcomes i.e. health threats and benefits, but also enjoyment. However, we do not know how people evaluate exercise as a reward. The value of rewards diminish the longer we have to wait for them and the discounting effect can undermine decision-making. Here, we investigated delay-discounting of exercise perception and its valuation with time delays; we conducted self-paced exercise sessions on treadmill and compared the discounting rates of exercise (k_ex) with those of established rewards of food (k_fo) and money (k_m). Outcomes show, that young, moderately active participants (n = 70) preferred walking/running intensity with low to moderate cardiovascular strain and light perceived exertion. Delay discounting rates (k) indicated that exercise was discounted like other consumable rewards at the same rate as food and more rapidly than monetary rewards. Significant associations were detected of k_ex with preferred speed and with extrinsic exercise motivation. Exercise training (n = 16) reduced k_ex specifically, not affecting k_fo. Our studies show, that participants perceived and discounted self-paced walking/running like a consumable reward. Exercise discounting was quicker in individuals who preferred lower speeds being less physically active and exercise training reduced the decay rate of exercise specifically.

How Young “Early Birds” Prefer Preservation, Appreciation and Utilization of Nature

Since the 1990s, the Two Major Environmental Value model (2-MEV) has been applied to measure adolescent environmental attitudes by covering two higher order factors: (i) Preservation of Nature (PRE) which measures protection preferences and (ii) Utilization of Nature (UTL) which quantifies preferences towards exploitation of nature. In addition to the 2-MEV scale, we monitored the Appreciation of Nature (APR) which, in contrast to the UTL, monitors the enjoyable utilization of nature. Finally, we employed the Morningness–Eveningness Scale for Children (MESC) which monitors the diurnal preferences and associates with personality and behavioral traits. In this study, we analyzed data from 429 Irish students (14.65 years; ±1.89 SD) with the aim of reconfirming the factor structure of the 2-MEV+APR and monitoring the relationship between the MESC and the environmental values (PRE, UTL, APR). Our findings identified a significant association between PRE and APR with MESC. In addition, we observed a gender difference. Our results suggest that morningness preference students are more likely to be protective of and appreciative towards nature. Recommendations for outreach programs as well as conclusions for environmental education initiatives in general are discussed.

Similarity in Chronotype and Preferred Time for Sex and Its Role in Relationship Quality and Sexual Satisfaction

Recently, the issue of diurnal preferences has been increasingly studied within the context of romantic relationships and sexual functioning. In the present paper we apply a dyadic design to investigate the role of romantic partners' diurnal preferences in determining a variety of relationship outcomes. A sample of 91 heterosexual couples completed a set of questionnaires measuring relationship satisfaction, sexual satisfaction, and morningness-eveningness, and answered questions regarding their actual and preferred time for sexual activity. Conducted analyses revealed that similarity in chronotype between partners and female morningness fostered relationship satisfaction in females, but not in males. Furthermore, morningness-eveningness was associated with preferred time for sex in males, but not in females, who in principle preferred evening hours. Although actual time for sex was up to the female preference, sexual satisfaction in both genders was associated with lower discrepancy in their preferred time for sex and greater frequency of intercourse. In sum, these results indicate that chronotype and time for sex are important factors affecting sexual and relationships satisfaction in heterosexual couples.