Circadian preference and mental health outcomes in youth: A systematic review and meta-analysis

Youth is a vulnerable developmental period associated with an increased preference for eveningness and risk for developing psychopathology. Growing evidence suggests a link between eveningness and poorer mental health outcomes, but the findings in the current literature are inconsistent, and a comprehensive synthesis of evidence in this area remains lacking. This meta-analysis aimed to 1) synthesise the existing evidence on the association between circadian preference and mental health outcomes in youths and 2) explore potential sleep-related factors that may moderate the relationship between circadian preference and mental health outcomes. A systematic search of five electronic databases resulted in 81 observational studies included in the review. Eveningness was found to be significantly associated with general mental health (r = 0.20), mood-related disturbances (r = 0.17), and anxiety problems (r = 0.13). The qualitative review also identified that eveningness was associated with greater risks for psychotic symptoms and maladaptive eating behaviours. These findings highlighted the need to consider circadian preference in the clinical management of youth mental health problems. Further research is needed to examine the efficacy of a circadian-focused intervention in the context of youth mental health.

Was there a significant difference in sleep shifts in the high school population due to the COVID-19 pandemic depending on chronotype? A nationwide cross-sectional study

The aim of this study was to detect whether the COVID-19 pandemic has caused changes in the sleep cycle (subjective sleep shifts) of high school students divided into a sample of young women - W (n = 1999, age = 17.65 ± 2.39 y) and young men - M (n = 1094, age = 17.49 ± 1.74 y) in Slovakia depending on circadian preference in comparison with the term before COVID-19. The present cross-sectional study employed a self-reported standardized questionnaire (Morningness-Eveningness Questionnaire) to study circadian preference, which was complemented by a question focused on subjective sleep shifts before and during the pandemic. The results revealed significant strong dependence between circadian preference and subjective sleep shift in both W (χ2(8) = 153.1, p < .01, Cramer's V = .20, p < .01) and M (χ2(8) = 98.3, p < .01, Cramer's V =.21, p < .01). The delay of the sleep cycle has mainly become apparent in the case of definite evening types (W: 75.7%; M: 71.8%) and moderate evening types (W: 83.1%; M: 70.3%). The delay also prevailed in the intermediate types (W: 61.9%; M: 53.8%). Subjective sleep shifts were not confirmed (W: 93.8%; M: 35.3%) in the definite morning type. The sleep cycle was changed to earlier hours of definite morning types (W: 6.3%; M: 52.9%). It is necessary to focus on definite and moderate evening types and regulate the unsuitable state to time shift of the sleep cycle.

Chronotype and sensory-processing sensitivity: A cross-sectional survey

Here we examined the possibility of a relationship of sensory processing sensitivity (SPS) with chronotype in a German-speaking sample of N = 1807 (1008 female, 799 male) with a mean age of 47.75 ± 14.41 y (range: 18-97 y). The data were collected using an anonymous online questionnaire (Chronotype: one item of the Morning-Evening-Questionnaire, as well as typical bedtimes on weekdays and weekends; SPS: German version of the three-factor model ; Big Five: NEO-FFI-30) between 21 and 27 April 2021. Results. We found morningness to correlate with the SPS facet low sensory threshold (LST), while eveningness correlated to aesthetic sensitivity (AES) and marginally significant to ease of excitation (EOE). Discussion: The results show that the correlations between chronotype and the Big Five personality traits are not consistent with the direction of the correlations between chronotype and the SPS facets. The reason for this could be different genes that are responsible for the individual traits influence each other differently depending on their expression.

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.

Evening chronotype predicts dropout of physical exercise: a prospective analysis

Purpose

Eveningness preference to sleep/wake and perform physical/cognitive activities has been associated with worse health outcomes, when compared to morningness preference. Physical activity is one potential mediator that could explain this relationship; however, most of these evidences come from cross-sectional design studies. Our goal was to assess whether chronotype could predict the risk of dropout of physical exercise programs.

Methods

We followed 153 newly enrolled volunteers at three different gyms, from both sexes, aged between 18 and 65 years, during 12 weeks. The daily frequency of exercises in the programs was objectively measured (gym's electronic turnstiles). Using questionnaires, we collected data of variables related to demographic characteristics, health, physical activity, sleep, anthropometric and chronobiological parameters (Morningness-Eveningness Questionnaire-MEQ). Two multivariate models were created using Cox regression analysis to test the risk of dropout of physical exercise practice. Both models accounted for age, educational level, civil status, membership plan duration, physical exercise practice frequency during week 1 and chronotype (MEQ score and chronotypes).

Results

Model 1 results showed that higher MEQ score was associated with a lower chance of quitting the program (HR = 0.98; CI95% 0.95-1.00; p = 0.046). Considering the chronotypes, E-types showed the highest dropout risk compared to that of M-types (HR = 2.22; CI95% 1.09-4.52; p = 0.027).

Conclusion

Our results suggest that chronotype is another variable to be considered in future studies on promoting PAs in formal environments. Likewise, the practice frequency during week 1 and duration of membership plan also deserve more attention in additional studies.

The circadian preferences in the context of sociodemographic indicators and lifestyle

Circadian preferences are frequently used as a synonym for chronotype. Both terms are based on different principles and are measured by a variant questionnaire. We focused on circadian preferences, delimited as an individual preference for the timing of various activities, and their relationship to the selected sociodemographic factors. All participants (n = 2068) filled out online questionnaires including MEQ, MCTQ, and sociodemographic information (age, sex, place of residence, marital status, childcare, education, financial security, physical and mental health). Although the concept of chronotype and circadian preference differ, the mutual correlation was high. Our results of the observed variables are similar to other studies. We revealed evening preference is related to a higher probability of living in a big city, having a single life, a higher risk of smoking, worse health status, and worse financial security. We observed a higher social jet lag among them. Our research complies with previous studies, which found that in some areas, people with evening preferences evince worse results. Due to the evening preference, these people are at a disadvantage, and the society's setting for morning operations can lead to a deepening of these differences. We recommend further research, which would focus on the practical application of results to the everyday life of participants to create preventive programs aimed at reducing the negative impact of evening preferences on life.

Circadian preference in young adults: Associations with sleep and mental health outcomes from a national survey of Norwegian university students

Individual preferred timing of sleep and activity patterns, known as circadian preference, ranges from definitely morning types to definitely evening types. Being an evening type has been linked to adverse sleep and mental health outcomes. This study aimed to explore the associations between circadian preference and self-reported sleep, depression, anxiety, quality of life, loneliness, and self-harm/suicidal thoughts. Data stem from a national survey of students in higher education in Norway (the SHoT-study). All 169,572 students in Norway were invited to participate, and 59,554 students (66.5% women) accepted (response rate = 35.1%). Circadian preference was associated with sleep and mental health outcomes in a dose-response manner. For both genders, being an evening type (either definitely evening or more evening than morning) was associated with an increase in age-adjusted relative risk (RR-adjusted; range = 1.44 to 2.52 vs. 1.15 to 1.90, respectively) across all outcomes compared with definitely morning types. Overall, the present study provides further evidence that evening circadian preference is associated with adverse sleep and mental health outcomes in young adults. As such, future efforts to improve sleep and mental health in young adults should consider their circadian preferences.

Morning chronotype is associated with higher adherence to the Mediterranean diet in a sample of Italian adults

BACKGROUND AND AIMS

A growing body of evidence has associated subjects with an evening chronotype with worse eating behaviours and poorer diet quality. However, only few studies have investigated the relationship between chronotype and Mediterranean diet (MD). The aim of this study was to better understand the chronotype influence on dietary habits and MD adherence in a large sample of Italian adults.

METHODS AND RESULTS

A total of 1247 participants (66.7% women) with a mean age of 36.1 ± 14.6 years were included in the analysis. Chronotype was classified as morning in 35.6% of subjects, intermediate in 56.7%, and evening in 7.1%. Regarding meal frequency, evening subjects showed a significantly (p < 0.05) greater tendency to skip breakfast (20.5%) than morning (6.9%) and intermediate (12%) subjects. Similarly, evening subjects were found to skip mid-morning snack more often than morning subjects (59.1% vs. 47.1%; p = 0.04), and lunch more often than intermediate subjects (8% vs. 2.8%; p = 0.01). In addition, all meals were eaten by evening subjects at a significantly delayed time, except for lunch. As to MD adherence a significant (p < 0.001) higher adherence in morning subjects (10.1 ± 2.2) compared to intermediate (9.5 ± 2.1) and evening (9.5 ± 2.2) subjects was observed. At a logistic regression analysis adjusted for possible confounding factors, morning subjects showed an increased probability (OR 1.54, 95%CI 1.19-1.99; p < 0.001) of being in the highest MD adherence tertile.

CONCLUSION

Chronotype was associated with MD adherence. In particular, morning subjects showed higher MD adherence than intermediate and evening subjects.

[Personal factors influencing daytime sleepiness]

Hintergrund und Zielsetzung

Während der ersten Coronawelle kam das öffentliche Leben weitgehend zum Erliegen. Viele Beschäftigte haben zum Schutz vor Ansteckung im Homeoffice gearbeitet. Mit der vorliegenden Befragung wurden Veränderungen im Schlafverhalten und der Tagesmüdigkeit bei Personen untersucht, die coronabedingt ins Homeoffice gewechselt hatten.

Methode

Büroangestellte wurden online zu ihrem Chronotyp, ihren üblichen Schlafenszeiten und dem Auftreten von Tagesmüdigkeit befragt. Die Datenerhebung fand zwischen dem 15.07. und 07.08.2020 statt. Zur Chronotypermittlung wurde die Composite Scale of Morningness (CSM) in der deutschsprachigen Version verwendet. Der Zusammenhang von Alter, Geschlecht, Chronotyp, Schlafqualität und Schlafdauer mit der selbst eingeschätzten Tagesmüdigkeit wurde mittels multivariabler logistischer Regression untersucht.

Ergebnisse

Die Daten von n = 228 Personen konnten ausgewertet werden. Unter Homeoffice-Bedingungen verlängerte sich die Schlafdauer. Der Anteil an Personen mit einer „Zeit-im-Bett“ von weniger als 7,5 h verringerte sich von 57 % auf 33 %, und der Anteil mit mehr als 8 h „Zeit-im-Bett“ erhöhte sich von 43 % vor Pandemiebeginn auf 67 % beim Arbeiten im Homeoffice. Der Anteil an Personen, die sich bei der Arbeit immer oder häufig müde fühlten, verringerte sich von 47 % vor Pandemiebeginn mit Präsenzpflicht im Büro auf 15 % unter Lockdown-Bedingungen beim Arbeiten im Homeoffice. Der Chronotyp zeigte einen signifikanten Einfluss auf die Tagesmüdigkeit an Büroarbeitstagen, nicht aber beim Arbeiten im Homeoffice unter Lockdownbedingungen.

Diskussion

Die längere Schlafdauer und die höhere Zufriedenheit mit der eigenen Schlafqualität könnten die Verringerung im Auftreten von Tagesmüdigkeit erklären. Späte Chronotypen scheinen besonders vom Arbeiten im Homeoffice zu profitieren. Ein flexibler Arbeitsbeginn unter Einbeziehung des Chronotyps sowie Maßnahmen für gesundheitsförderlichen Schlaf könnten die Tagesmüdigkeit verringern und dadurch die Gesundheit und Arbeitssicherheit verbessern.

Circadian preference is associated with multiple domains of trait and state level impulsivity

Impulsivity is a multidimensional construct with well-documented risk for substance use problems at both the trait- and state levels. A circadian preference towards eveningness has been linked to trait-level, global impulsivity, but whether this association holds true across multiple dimensions of impulsivity and whether actual sleep timing shows parallel associations with impulsivity remain unclear. Here, we extend existing literature by investigating whether eveningness is associated with multiple facets of both trait- and state-level impulsivity. We also examined these associations utilizing daily measures of sleep timing and duration and explored whether they differed by sex and/or race. All participants were moderate-to-heavy social drinkers aged 21-35. Primary analyses included 78 participants (100% White male participants: Sample 1) with circadian preference data (Composite Scale of Morningness: CSM) and sleep timing (midsleep) and duration assessed via daily self-report over 10 days. Five facets of impulsivity were assessed via the UPPS-P, both at baseline (full scale; trait-level) and up to 6 times per day over 10 days (reduced scale; state-level). Linear regression and mixed-effects models were used to examine between- and within-person associations of impulsivity with measures of circadian preference, timing, and duration, accounting for covariates. Exploratory analyses combined Sample 1 with an additional more diverse sample (Sample 2), resulting in a total of 182 participants (29.1% self-identified as Black, 29.7% as female) with daily self-report sleep timing and duration only (no circadian preference). Primary between-person models found that eveningness was associated with multiple facets of impulsivity, at trait (lack of perseverance) and state levels (negative and positive urgency, lack of perseverance, and lack of premeditation), while average midsleep and duration were generally unrelated to impulsivity. Primary within-person models largely paralleled the between-person findings. Exploratory analyses in the larger combined Samples 1 and 2 (without circadian preference) found that later midsleep timing was associated with greater mean state-level impulsivity across multiple facets, associations that may differ by race and sex. In a sample of White male participants, circadian preference for eveningness was strongly associated with multiple facets of impulsivity, at both trait- and state-levels, which may contribute to risk for substance use. Preliminary findings suggest sex and race differences in sleep-impulsivity associations, but future research with objective sleep/circadian measures in larger, more diverse samples will be important to clarify implications for sleep-focused prevention and/or treatment of substance use.

Evidence for the Association between Chronotype and Lifelong Premature Ejaculation

PURPOSE

This study aimed to investigate the relationships between intravaginal ejaculatory latency time (IELT), severity of disease, and chronotype in lifelong premature ejaculation (PE).

MATERIALS AND METHODS

Evaluation was made of 114 males with PE and 103 healthy individuals, and comparisons were made of self-estimated IELT, Arabic Index of Premature Ejaculation (AIPE), Pittsburg Sleep Quality Index (PSQI), and Morningness-Eveningness Questionnaire (MEQ).

RESULTS

The frequency of morningness chronotype (78.1%) was significantly higher, and Morningness-Eveningness Questionnaire (MEQ) scores were negatively correlated with both IELT (r = -0.490, p < 0.001) and Arabic Index of Premature Ejaculation (AIPE) scores (r = -0.639, p < 0.001) in the PE group. MEQ scores significantly predicted IELT (t = -2.465, p = 0.015) and AIPE scores (t = -4.003, p = 0.000) in the PE group but not in the control group.

CONCLUSION

It can be asserted that morningness chronotype is more common, and ejaculatory latency time and PE severity are associated with chronotype in males with PE.

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.

Circadian preference and academic achievement in school-aged students: a systematic review and a longitudinal investigation of reciprocal relations

We provide a systematic review of findings on the relation between circadian preference and school achievement published after the last comprehensive review in 2015. We further test this relation in a longitudinal study. Our review of 26 studies revealed a positive relation between morningness and students' school achievement, and a negative relation between eveningness and school achievement. In most studies, these relations were not affected by students' age, sex, or intelligence, but were significantly mediated by students' conscientiousness, motivation, and sleep behavior. Furthermore, circadian preference and school achievement showed no significant relation when school started in the afternoon. All studies were cross-sectional. Therefore, the direction of the relations between circadian preference, school achievement, and potential mediating variables like conscientiousness and motivation could not be investigated. In our longitudinal study, we tested the direction of the relations between circadian preference, academic achievement, conscientiousness, self-efficacy, and attitude toward school over time in a sample of 764 German high school students who were tested in the first (T1) and third (T2) year of high school. Findings from confirmatory cross-lagged models indicated reciprocal relations between circadian preference and school achievement: T1 morningness positively predicted change in grade point average over time while T1 grade point average positively predicted change in morningness and negatively predicted change in eveningness. Furthermore, T1 conscientiousness and T1 attitude toward school both positively predicted change in morningness, whereas T1 morningness and T1 eveningness did not significantly predict change in these variables.

Sleep habits and circadian preferences in school-aged children attending a Mexican double-shift school system

OBJECTIVE

To determine the differences between sleep habits and circadian preference in school-aged children attending a Mexican double-shift school system.

METHODS

This cross-sectional study consisted of 400 elementary public-school children (mean age = 10.77, SD = 0.70 y, from fourth, fifth and sixth grades) in Reynosa, Tamaulipas, in northeastern Mexico. Attending a double-shift school system: 200 from the morning shift and 200 in the afternoon shift. Specific questions regarding sleep habits were collected and for circadian preference, the Morningness-Eveningness Scale for Children (MESC) was used.

RESULTS

Multivariate analysis reported no sex differences. Children attending at the morning shift during weekdays rose earlier, reported shorter time in bed and earlier midpoint of sleep than those in the afternoon shift. On weekends, morning shift children went to bed later than afternoon shift. Morning shift reported greater social jetlag, shorter average sleep length and more sleep deficit than afternoon shift. During weekdays and weekends evening type children went to bed later, rose later and reported later midpoint of sleep. Also, evening type reported more social jetlag than morning types.

CONCLUSION

This study suggests that early school start times can have a detrimental effect on Mexican children. Moreover, the morning shift children may be at more risk of poor health due to the higher social jetlag, as well as a higher tendency to be sleep deprived. On the other hand, the afternoon shift represents an important social environment that allows children to follow their natural physiological needs and a more optimal sleep health.

Changes in sleep schedule and chronotype due to COVID-19 restrictions and home office

Background and objective

In this study, we researched the effects of the COVID-19 restriction measures on the sleep health of N = 681 German residents (mean age: 28.63 years, SD: 10.49 years).

Methods

The data were collected with an anonymous online survey composed of validated questionnaires and additional questions to quantify changed circumstances during the pandemic. Data were collected from May 18 to June 17, 2020, while governmental restrictions were imposed in Germany. We exclusively analysed participants working in home office during this time.

Results

Participants woke up about 1 hour later during the COVID-19 restriction phase, while going to bed at almost the same time as before. During the week, participants slept about an hour longer, while sleep at weekends did not differ significantly. Social jetlag decreased from 1:39 ± 1:00 to 0:49 ± 0:42 min in our sample. The number of children in the household was a significant factor predicting sleep timing. Participants with children living in the same household slept longer and sleep onset was later.

Conclusion

In terms of sleep behaviour and, consequently, sleep health, participants benefited from the transition to home office. They were able to adapt their waking and working hours better to their biological rhythm, which reduced social jetlag.

The influence of intensity and timing of daily light exposure on subjective and objective sleep in adolescents with an evening circadian preference

STUDY OBJECTIVES

The aim of the present study is to examine the relationship between light and sleep, in adolescents with an evening circadian preference.

METHODS

For a period of seven days, ninety-nine adolescents wore a wrist actigraph to assess light exposure and objective sleep and completed a sleep diary to assess subjective sleep.

RESULTS

Lower average light intensity across the preceding 24 h was associated with a later sleep onset (p < 0.01) and a later next-day sleep offset (p < 0.05). A later time of last exposure to more than 10 lux was associated with a later sleep onset (p < 0.001) and a shorter objective total sleep time (p < 0.001), as well as a later bedtime (p < 0.001) and a shorter subjective total sleep time (p < 0.001). Furthermore, exploratory analyses found that lower average early morning light exposure (between 4 and 9 AM) was associated with later sleep onset (p < 0.05), a later next-day sleep offset (p < 0.05), and a later next-day waketime (p < 0.01), lower average afternoon light exposure (between 2 and 7 PM) was associated with a later next-day sleep offset (p < 0.05), and lower average evening light exposure (between 7 PM and 12 AM) was associated with longer subjective total sleep time (p < 0.01).

CONCLUSION

This study highlights the importance of light exposure, particularly the timing of light exposure, for establishing healthy patterns of sleep among adolescents with a propensity for a delayed bedtime and waketime. These findings provide additional evidence for targeting light exposure when designing interventions to improve adolescent sleep.

Circadian preferences of birdwatchers in Poland: do "owls" prefer watching night birds, and "larks" prefer daytime ones?

Birdwatching is a very popular and increasing leisure activity, and the study and observation of birds is more popular in the morning due to the greater activity among birds at that time of day. The aim of our study was to find out whether there was a relationship between the circadian preference of observers and their favourite bird species and whether it was influenced by such factors as professional status, age and gender. In an e-mail survey we asked a total of 433 Polish ornithologists (professionals) or birdwatchers (non-professionals) for their morningness–eveningness preferences (four categories) and favourite (open choice) bird species and received 143 responses. The temporal (circadian) preferences of respondents declined from early morning (35.7%) to evening/nighttime (11.4%). Circadian preference categories differed significantly by age, with early morning respondents significantly older. These preference categories did not differ significantly in terms of response time to the survey invitation or in the percentage of their favourite birds that were categorised as daytime birds. A total of 204 species were identified as favourite birds of which 34 species were mentioned by five or more respondents, with only two, the common crane Grus grus and the Eurasian pygmy owl Glaucidium passerinum mentioned by more than 10% of respondents. The white stork Ciconia ciconia was more popular with professionals than non-professionals and the swift Apus apus less popular. A significant gender × circadian preference interaction was detected for the percentage of favourite birds categorised as daytime birds, with fewer daytime birds among early morning female recorders. The presented results are obviously of a correlative nature, but open the door for further, more advanced study and suggest there may be a need to investigate temporal biases when analysing citizen-based data.

Time-of-day effects on prospective memory

Cognitive performance fluctuates during the course of a day. Different cognitive functions show optimal performance at different times of the day, known as the 'time-of-day effect'. While this effect has been observed for a number of cognitive domains including declarative memory, it is presently unclear whether performance fluctuations are also seen in prospective memory, i.e. memory for intentions to be realized in the future. The present study examined time-of-day effects in four different prospective memory tasks with varying degrees of complexity, taking into account circadian preference (i.e. morningness-eveningness/chronotype) and attentional resources (in one of the tasks). In a pilot study (n = 48) and a main experiment (n = 39), prospective memory was compared between morning groups (˜09:00) and evening groups (˜21:00) of young adults. We found time-of-day effects, with better performance in the evening than in the morning, in a simple one-item prospective memory task (Red Pencil Task, p = .02), a classical event-based prospective memory task including the detection of cue syllables in a lexical decision ongoing task (Syllable Detection Task, p < .048), and a rather naturalistic complex planning task for breakfast preparation (Dresden Breakfast Task, including time-based prospective memory (p = .026) and event-based prospective memory (p = .054)). These time-of-day effects were neither modulated by circadian preference nor by attentional resources. Another simple one-item prospective memory task was not affected by time of day (Color Task, p = .14). Ongoing task performance in the Syllable Detection Task and the Dresden Breakfast Task, overall, did not differ significantly between morning and evening groups. These findings provide tentative evidence for time-of-day effects in prospective memory of young adults, with better performance in the evening hours.

Association between circadian preference and blood lipid levels using a 1:1:1 propensity score matching analysis

BACKGROUND

Previous studies indicate that circadian preference is associated with various energy metabolism and metabolic disorders. However, little is known about the associations between a circadian rhythm and blood lipid levels, especially in humans.

OBJECTIVE

The aim of the study was to investigate whether the circadian rhythm affects serum lipid levels in Korean adults.

METHODS

We designed a cross-sectional study to evaluate the associations between circadian preference and blood lipid levels in Korean adults. A total of 1984 participants (range of age 19-81 years) were included in this study. Propensity scores were calculated using logistic regression with age, sex, and body mass index. A total of 435 subjects were evaluated by propensity score matching analysis, equally distributed into morningness, intermediate, and eveningness groups, each with 145 subjects. Circadian preference was evaluated by the Morningness-Eveningness Questionnaire.

RESULTS

Participants with the evening preference had significantly higher levels of total cholesterol, triglyceride, low-density lipoprotein cholesterol, and non-high-density lipoprotein cholesterol (non-HDL-C) when compared with those with morning or intermediate preference, after adjusting for confounding variables. Regarding other lipid parameters, both total cholesterol/HDL-C and low-density lipoprotein cholesterol/HDL-C in the evening preference are significantly higher than those of other circadian preferences. Evening preference was also significantly associated with a higher atherogenic index of plasma.

CONCLUSION

Our study demonstrates that there is a significant association between circadian preference and blood lipid levels. Our findings suggest that individuals with evening preference could have a greater risk of atherosclerotic cardiovascular diseases.

Salivary Pubertal Hormones, Sleep Disturbance, and an Evening Circadian Preference in Adolescents: Risk Across Health Domains

PURPOSE

Puberty influences biological and psychological development during adolescence. This includes a shift toward an evening circadian preference, which is characterized by greater physical and mental activity at night compared to the morning. This study examines how pubertal hormones are related to risk across key health domains among adolescents with an evening circadian preference.

METHODS

Participants were adolescents with an evening circadian preference (n = 165, 96 female and 69 male, mean age = 14.8) from an NICHD-funded study. Hormones included testosterone, dehydroepiandrosterone (DHEA), and estradiol (females only). Sleep measures included weeknight total sleep time and weeknight bedtime. Circadian preference was assessed with the Children's Morningness-Eveningness Preferences Scale. Health domains included emotional, cognitive, behavioral, social, and physical health.

RESULTS

For female adolescents, estradiol was related to higher risk in the emotional domain. Among female adolescents with later bedtimes, higher estradiol was associated with higher behavioral domain risk (specifically alcohol and substance use). For male adolescents with a more extreme evening circadian preference, higher DHEA and testosterone were associated with higher behavioral domain risk, specifically greater alcohol and substance use or sensation seeking (DHEA only). Among female adolescents with a more extreme evening circadian preference, higher DHEA was associated with greater physical health risk.

CONCLUSIONS

Pubertal hormones may be associated with heightened risk across select health domains. Specifically, higher levels of hormones may contribute to increased risk for alcohol and substance use as well as sensation seeking in the context of an evening circadian preference.

What predicts inattention in adolescents? An experience-sampling study comparing chronotype, subjective, and objective sleep parameters

OBJECTIVE

Many adolescents sleep insufficiently, which may negatively affect their functioning during the day. To improve sleep interventions, we need a better understanding of the specific sleep-related parameters that predict poor functioning. We investigated to which extent subjective and objective parameters of sleep in the preceding night (state parameters) and the trait variable chronotype predict daytime inattention as an indicator of poor functioning.

METHODS

We conducted an experience-sampling study over one week with 61 adolescents (30 girls, 31 boys; mean age = 15.5 years, standard deviation = 1.1 years). Participants rated their inattention two times each day (morning, afternoon) on a smartphone. Subjective sleep parameters (feeling rested, positive affect upon awakening) were assessed each morning on the smartphone. Objective sleep parameters (total sleep time, sleep efficiency, wake after sleep onset) were assessed with a permanently worn actigraph. Chronotype was assessed with a self-rated questionnaire at baseline. We tested the effect of subjective and objective state parameters of sleep on daytime inattention, using multilevel multiple regressions. Then, we tested whether the putative effect of the trait parameter chronotype on inattention is mediated through state sleep parameters, again using multilevel regressions.

RESULTS

We found that short sleep time, but no other state sleep parameter, predicted inattention to a small effect. As expected, the trait parameter chronotype also predicted inattention: morningness was associated with less inattention. However, this association was not mediated by state sleep parameters.

CONCLUSIONS

Our results indicate that short sleep time causes inattention in adolescents. Extended sleep time might thus alleviate inattention to some extent. However, it cannot alleviate the effect of being an 'owl'.

Eveningness among late adolescent males predicts neural reactivity to reward and alcohol dependence 2 years later

Eveningness, a preference for later sleep-wake timing, is linked to altered reward function, which may explain a consistent association with substance abuse. Notably, the extant literature rests largely on cross-sectional data, yet both eveningness and reward function show developmental changes. We examined whether circadian preference during late adolescence predicted the neural response to reward 2 years later. A sample of 93 males reported circadian preference and completed a monetary reward fMRI paradigm at ages 20 and 22. Primary analyses examined longitudinal paths from circadian preference to medial prefrontal cortex (mPFC) and ventral striatal (VS) reward responses. We also explored whether reward responses mediated longitudinal associations between circadian preference and alcohol dependence, frequency of alcohol use, and/or frequency of cannabis use. Age 20 eveningness was positively associated with age 22 mPFC and VS responses to win, but not associated with age 22 reactivity to reward anticipation. Age 20 eveningness was indirectly related to age 22 alcohol dependence via age 22 mPFC response to win. Our findings provide novel evidence that altered reward-related brain function could underlie associations between eveningness and alcohol use problems. Eveningness may be an under-recognized but modifiable risk factor for reward-related problems such as mood and substance use disorders.

The Impact of Early Bedtimes on Adolescent Caloric Intake Varies by Chronotype

PURPOSE

Adolescent sleep restriction is common and can lead to overeating. Here, we test whether lengthening sleep via early bedtimes affects dietary intake differently for adolescents accustomed to a later sleep phase ("night owls") versus an earlier sleep phase ("morning larks").

METHODS

Using a randomized cross-over design, 67 adolescents changed bedtimes to create five-night periods of sleep restriction (6.5 hours in bed) versus healthy sleep (10 hours in bed). Caloric intake was measured via validated interviews. Phase preference was based on participants' premanipulation sleep.

RESULTS

Actigraphy verified that the manipulation altered sleep regardless of phase preference. Phase preference moderated the effect of the manipulation on cumulative caloric intake (p = .01-.03). Night owls showed little effect, but morning larks reduced their evening intake during healthy sleep.

CONCLUSIONS

An "early to bed" approach confers little dietary benefit for night owls but may have a protective effect for adolescents who gravitate toward earlier bedtimes.

Circadian preference and trait impulsivity, sensation-seeking and response inhibition in healthy young adults

Circadian preference has been considered related with impulsivity. The purpose of the present study was to evaluate the relationship between circadian typology and impulsivity measured by the Barratt Impulsivity Scale (BIS), sensation-seeking measured by the Sensation Seeking Scale - Form V (SSS-V) and response inhibition elicited by the GO/NO-GO paradigm. A total of 503 Korean healthy college students (288 males and 215 females) completed the Composite Scale of Morningness (CSM) for circadian typology and the BIS and SSS-V for impulsivity and risk taking, respectively. A subset of 142 subjects additionally performed the computerized GO/NO-GO task for motor response inhibition. A significant association was found between the circadian typology of the CSM and impulsivity of the BIS and disinhibition of SSS-V. In addition, there was a difference in trend level between the circadian typology and response inhibition elicited by the GO/NO-GO test. Regarding circadian preference, evening types were significantly associated with higher impulsivity on the BIS, disinhibition on the SSS-V and lower rate of successful inhibition on the GO/NO-GO task compared to morning types. The present results showed significant relationships between circadian preference and impulsivity and sensation-seeking personality traits. In particular, our findings suggest that high impulsivity, disinhibition and impaired response inhibition are more related to evening types. Circadian preference might be associated with psychiatric problems interacting with some aspects of personality traits such as inhibitory control.