Association Of Chronotype Research Articles

The association of chronotype, sleep duration and trajectories of health-risk behaviors among college students: a cohort study

PurposeTo describe the trajectories of health-risk behaviors (HRBs) among college students through four consecutive surveys and explore the relationship between chronotype, sleep duration and different trajectories of HRBs.MethodsWe used a data sample of 1,042 college students from the College Student Behavior and Health Cohort Study. Students reported sleep parameters, including chronotype (Morningness-Eveningness Questionnaire-5, MEQ-5) and sleep duration. The behavior scale was used to evaluate four HRBs (smoking, alcohol use, low physical activity, smartphone addiction). The latent class growth analysis (LCGA) was used to estimate the trajectory of self-reported HRBs. Multivariate logistic regression models were used to study whether sleep parameters (chronotype and sleep duration) correlated with HRBs’ trajectories.ResultsFour unique trajectories of behaviors were identified: unhealthy group (7.4%), increasing group (21.3%), decreasing group (10.3%) and healthy group (61.0%). Compared with the normal sleep, results from logistic regression analyses indicated that long sleep (> 9 h) was associated with the decreasing group and the unhealthy group (P < 0.05), while short sleep (< 7 h) was associated with the increasing group and the unhealthy group (P < 0.05). Compared with the M-type, the E-type were positively correlated with the unhealthy group, the increasing group, and the decreasing group (P < 0.05).ConclusionE-type, short sleep duration and long sleep duration were significantly associated with the trajectory of HRBs. Findings underscore the need for targeted screening and prevention of modifiable sleep behaviors with the aim of improving HRBs in college students.

Association of chronotype and timing of interferon injection with severity of IFNβ-induced flu-like syndrome in Multiple sclerosis (MS) patients

BackgroundAlthough Interferon-beta (IFNβ) has long been approved as a disease-modifying therapy (DMT) for Multiple sclerosis (MS), flu-like syndrome (FLS) persists as a common adverse effect of interferon therapy. Given the importance of circadian rhythm in regulating physiological processes, we aimed to assess the relationship between patient’s chronotype and time of interferon injection with FLS score in MS patients receiving IFNβ. MethodsA cross-sectional study was conducted on 118 MS patients who were referred to the clinic of neurology of Zanjan Vali-e-Asr Hospital for interferon injection. The included were invited to complete a morningness-eveningness questionnaire (MEQ) assessing patients’ chronotype. The following data were extracted from patients’ record: age, gender, duration of interferon treatment, type of interferon taken, time of interferon injection (morning/evening), FLS score, MS subtype, and usage of pain killers. All data found were imported and statistically analyzed in SPSS ver.26. ResultsAccording to the patients’ record, 114 (96.6%) patients had experienced post-interferon injection FLS with different severities. Statistical analysis revealed no significant relationship between the patient’s chronotype and FLS score. Nevertheless, the FLS score was significantly higher in those who had evening injections. ConclusionsTime of interferon injection was significantly associated with FLS score, with higher FLS score following evening injection. However, no significant relationship was found between the FLS score and the patient’s chronotype. It is recommended that further studies assessing circadian rhythm using laboratory tests such as melatonin measurement need to be undertaken to investigate the association of circadian rhythm with post-interferon injection FLS.

Association of chronotype with language and episodic memory processing in children: implications for brain structure.

Chronotype refers to individual preference in circadian cycles and is associated with psychiatric problems. It is mainly classified into early (those who prefer to be active in the morning and sleep and wake up early) and late (those who prefer to be active in the evening and sleep and wake up late) chronotypes. Although previous research has demonstrated associations between chronotype and cognitive function and brain structure in adults, little is known regarding these associations in children. Here, we aimed to investigate the relationship between chronotype and cognitive function in children. Moreover, based on the significant association between chronotype and specific cognitive functions, we extracted regions-of-interest (ROI) and examined the association between chronotype and ROI volumes. Data from 4,493 children (mean age of 143.06 months) from the Adolescent Brain Cognitive Development Study were obtained, wherein chronotype (mid-sleep time on free days corrected for sleep debt on school days) was assessed by the Munich Chronotype Questionnaire. Subsequently, the associations between chronotype, cognitive function, and ROI volumes were evaluated using linear mixed-effects models. Behaviorally, chronotype was negatively associated with vocabulary knowledge, reading skills, and episodic memory performance. Based on these associations, the ROI analysis focused on language-related and episodic memory-related areas revealed a negative association between chronotype and left precentral gyrus and right posterior cingulate cortex volumes. Furthermore, the precentral gyrus volume was positively associated with vocabulary knowledge and reading skills, while the posterior cingulate cortex volume was positively associated with episodic memory performance. These results suggest that children with late chronotype have lower language comprehension and episodic memory and smaller brain volumes in the left precentral gyrus and right posterior cingulate cortex associated with these cognitive functions.

Association of Chronotype and Shiftwork With COVID-19 Infection.

This study assesses whether chronotype is related to COVID-19 infection and whether there is an interaction with shift work. Methods: This study used a cross-sectional survey of 19,821 U.S. adults. Results: COVID-19 infection occurred in 40% of participants, 32.6% morning and 17.2% evening chronotypes. After adjusting for demographic and socioeconomic factors, shift/remote work, sleep duration, and comorbidities, morning chronotype was associated with a higher (adjusted odds ratio [aOR]: 1.15, 95% CI: 1.10-1.21) and evening chronotype with a lower (aOR: 0.82, 95% CI: 0.78-0.87) prevalence of COVID-19 infection in comparison to an intermediate chronotype. Working exclusively night shifts was not associated with higher prevalence of COVID-19. Morning chronotype and working some evening shifts was associated with the highest prevalence of previous COVID-19 infection (aOR: 1.87, 95% CI: 1.28-2.74). Conclusion: Morning chronotype and working a mixture of shifts increase risk of COVID-19 infection.

Abstract 27: Chronotype, Life’s Essential 8, and Risk of Cardiovascular Disease: A Prospective Cohort Study in UK Biobank

Introduction: Individuals with evening chronotype often experience circadian misalignment, which may disrupt health behaviors and circadian regulation of cardiometabolic functions such as blood pressure and heart rate. However, the association of chronotype with cardiovascular disease (CVD) and the interplay with other CVD risk factors are not fully understood. Hypothesis: We assessed the hypothesis that individuals with an evening chronotype, compared to those with a morning chronotype, have a poorer cardiovascular health as measured by the Life’s Essential 8 (LE8), and consequently an increased CVD risk. We further explored if the associations differed by sex. Methods: We conducted a prospective study in the UK Biobank among 477,878 adults aged 39-74 years and free of CVD at baseline in 2006-2010. Chronotype was self-reported using a single representative question from the Morningness-Eveningness Questionnaire. The LE8 score was calculated based on 8 modifiable CVD risk factors, and ranged from 0 to 100 with higher scores indicating better cardiovascular health. Incident CVD was defined as first myocardial infarction (MI) or stroke leading to hospitalization or death, identified via validated algorithms that mapped national medical records and death certificates to ICD-10 codes until May 2022. We used Cox proportional hazards models to estimate the association between chronotype and CVD risk. Models were adjusted for demographics, shift work, and family history of CVD. We applied causal mediation framework to decompose the total chronotype-CVD effect into estimated natural direct effect (i.e., independent of LE8) and natural indirect effect (i.e., mediated by LE8; NIE). Results: Participants with a “definite evening” chronotype were 75% more likely to have a low LE8 score (&lt;50) compared to “intermediate” type (prevalence ratio 95% CI: 1.67, 1.84). This association was notably stronger among women ( P -interaction: 0.0001). Over 12.7 years of follow-up, there were 27,346 documented incident CVD events (17,180 MI; 11,329 stroke). The hazard ratio (HR) for total CVD was 1.03 (95% CI: 1.00, 1.06) for the “definite morning” and 1.15 (95% CI: 1.10, 1.20) for “definite evening” compared with “intermediate” chronotype ( P -trend: 0.06). This association was stronger in women ( P -interaction: 0.05), and similar for MI and stroke. The NIE of the chronotype-CVD association comparing “definite evening” to “intermediate” was 1.11 (95% CI: 1.09, 1.13), equivalent to 95% of the association being mediated by LE8. Conclusions: Evening chronotype was associated with a modest increase in CVD risk, compared to intermediate chronotype, which appeared to be mainly explained by overall poor cardiovascular health. Our results suggest potential benefits of targeted interventions in evening chronotype for CVD prevention. Ongoing work is exploring potential effect modification by night shift work.

Is the association of chronotype with adolescent behavior problems mediated through social jetlag?

ABSTRACT We examined the associations of chronotype with behavior problems in a cross-sectional study of 957 Colombian adolescents (mean age, 14.6 years; 56% female), in addition to the mediating role of social jetlag. The midpoint of bedtime and waketime on free days, corrected for sleep debt accumulated during school week (MSFsc), was estimated from parent reports and used to assess chronotype. Behavior problems were evaluated through the Youth Self-Report (YSR) and the parent-completed Child Behavior Checklist (CBCL) questionnaires. We estimated adjusted mean differences with 95% CI in externalizing, internalizing, attention, social, and thought problem scores per one hour difference in chronotype using linear regression. Later chronotype was related to internalizing and externalizing behavior problems. Eveningness was associated with higher adjusted mean YSR scores (unit difference per hour) in externalizing behavior (1.0; 95% CI: 0.6, 1.5), internalizing behavior (0.6; 95% CI: 0.2, 1.1), attention problems (0.2; 95% CI: 0.0, 0.3), social problems (0.4; 95% CI: 0.1, 0.8), and thought problems (0.3; 95% CI: 0.1, 0.6). Similar patterns were observed with the CBCL. The associations of chronotype with somatic complaints and social problems were stronger in boys than they were in girls. Later chronotype was related to social jetlag but social jetlag was only associated with somatic complaints and attention problems, and mediated 16% and 26% of their corresponding associations with chronotype. In conclusion, later chronotype is associated with behavior problems in adolescence. Social jetlag does not substantially mediate these associations.

The association of chronotype and social jet lag with body composition in German students: The role of physical activity behaviour and the impact of the pandemic lockdown.

Young adults with a later chronotype are vulnerable for a discrepancy in sleep rhythm between work- and free days, called social jet lag (SJL). This study analysed (i) chronotype/SJL association with visceral fat/skeletal muscle mass, (ii) the attribution to physical activity behaviour, and (iii) chronotype-specific changes in physical activity behaviour in young adults during the Covid-19 pandemic lockdown. Chronotype and SJL were derived from the Munich-Chrono-Type-Questionnaire in 320 German students (age 18-25 years) from September 2019 to January 2020, 156 of these participated in an online follow-up survey in June 2020. Body composition was assessed by bioimpedance analysis at baseline. Multivariable linear regression analyses were used to relate chronotype/SJL to body composition; the contribution of self-reported physical activity was tested by mediation analysis. At baseline, a later chronotype and a larger SJL were associated with a higher visceral fat mass (P<0.05), this relation was notably mediated by the attention to physical activity (P<0.05). Chronotype (P = 0.02) but not SJL (P = 0.87) was inversely associated with skeletal muscle mass. During the pandemic lockdown, chronotype hardly changed, but SJL was reduced. Timing and physical activity behaviour remained in most participants and changes were unrelated to chronotype (all P>0.07). A later chronotype/higher SJL may increase the risk of a higher visceral fat mass even in this relatively healthy sample, which may be partly due to their physical activity behaviour. Despite a reduction in SJL during the pandemic lockdown, later chronotypes did not change their physical activity behaviour more than earlier chronotypes.

Morningness-eveningness Preferences among Medical Students: A Cross-sectional Study

Introduction: Morningness and eveningness is a phenomenon which looks at the differences among the individuals regarding their diurnal preferences, sleep-wake pattern of activity and alertness in evening or morning. Morning chronotypes are individuals who exhibit morning tendencies like rising early in the morning while evening chronotypes prefer to get up later in the morning and stay awake later at night time and also perform their best during late afternoon or evening. Morning chronotypes are known to exhibit better physical and mental health, greater self-esteem and academic performance. Aim: To estimate the prevalence of morningness and eveningness among medical students. Association of chronotype with academic performance was also determined. Materials and Methods: The present cross-sectional study was conducted on 110 apparently healthy medical students at Shaheed Hasan Khan Mewati Government Medical College, Nalhar, Haryana, India from October 2021 to January 2022. All the participants were sent a validated Morningness-Eveningness self-assessment Questionnaire (MEQ). Data of chronotypic preferences expressed as frequencies of participants (%) and association determined using Pearson’s Chi-square test and p-value &lt;0.05 was considered statistically significant. Results: Study revealed that 67 (61%) students belonged to the Intermediate (I) chronotype, around one-fourth {n=26 (24%)} were Morning (M) type while 17 (15%) were Evening (E) type. Morningness was more frequently reported by females as compared to males in n=8 (28%) vs. n=18 (22%) respectively. Higher scores (≥50%) were more prevalent among M types as compared E types in n=10 (38%) vs. n=3 (18%) respectively}; however, association between chronotype and academic performance could not reach significant level (p-value=0.15). Conclusion: The distribution of chronotypes in study sample provided the evidence that majority of students could be classified as intermediate type. Morningness was more frequent in females as compared to males. Further studies with large sample size are needed to explore the influence of chronotype on academic performance.

Association of chronotype, social jetlag, sleep duration and depressive symptoms in Chinese college students

ObjectivesTo describe the prevalence of depressive symptoms among Chinese college students and examine the relationship between sleep and circadian rhythm disruption (SCRD) indicators (chronotype, social jetlag, sleep duration) and depressive symptoms. MethodsFrom April to May 2019, the College Student Behavior and Health Cohort Study was conducted among Chinese college students from 2 universities in Anhui and Jiangxi provinces. The current study used data from the third follow-up study. Questionnaire content includes socio-demographic and lifestyle information. Social jetlag and sleep duration were calculated by answering the question about sleep time. Chronotype was assessed by the Morning and Evening Questionnaire (MEQ-5). Depressive symptoms were evaluated by the Patient Health Questionnaire 9 (PHQ-9). A Chi-square test was used to examine the proportion depressive symptoms. Multinomial logistic regression model were used to explore the associations of circadian rhythm indicators with depressive symptoms. ResultsThe prevalence of mild depression, moderate and above depression was 18.8 % and 6.9 %. Evening types (E-types) and short sleep duration were significantly associated with depression. Stratified analysis indicated that E-types and social jetlag≥2 h were associated with mild depression (OR = 5.67, 95 % CI: 1.83–17.51), as well as stratified analysis indicated that E-types and sleep duration<8 h were associated with mild depression (OR = 5.10, 95 % CI: 1.88–13.87). ConclusionsThe findings suggest that depressive symptoms are more severe when multiple SCRD indicators are out of whack. The intervention programs of depressive symptoms should consider the context of the multidimensional aspects of Chinese college student sleep.

Association of chronotype with eating habits and anthropometric measures in a sample of Iranian adults.

There is a lack of consistency in the literature that shows a relationship between chronotype, habits of eating and obesity in Iranian adults. This cross-sectional study was conducted on 850 individuals aged ≥ 18 years, selected from health houses of Tehran, Iran. Chronotype was assessed by Horne and Ostberg morningness-eveningness questionnaire. Specific eating habits, including breakfast skipping, intakes of fruits and vegetables, fast food, processed meats, soft drinks, coffee and tea, were assessed by dietary recalls. Weight, height, BMI, waist circumference, waist to hip ratio, waist to height ratio, visceral adiposity index, body roundness index and body adiposity index were based on measured values. We used logistic regression to investigate the association between chronotypes and anthropometric measures as well as eating habits. Morning- and intermediate/evening-type chronotypes accounted for 51·4 and 48·6 % of the total individuals, respectively. Moreover, intermediate/evening-type chronotypes were shown to have a lower education of diploma (53 %), employed (49·9 %) and smokers (11·6 %) compared with morning types (both sexes). We found that intermediate/evening-type chronotypes might not be significantly related to higher anthropometric measures and following unhealthy eating habits after controlling for confounders in men and women (all P > 0·05). Overall, both anthropometric measures and specific eating habits were not related to chronotype among Iranian adults. Further studies are needed to clarify these relations and to consider sleep disturbances.

P124 Chronotype and OSA combine to modify risk of hypertension

Abstract Introduction There are limited data on the association of chronotype and hypertension and on their interaction on hypertension. This study aimed to investigate the independent and combined effects of chronotype and OSA on risk for prevalent hypertension in a middle-aged community population. Methods Baseline data on adult participants (n=1098, female=58%; age mean [range]=56.7[40.8–80.6] years) from an Australian community cohort study were analysed. Shift workers and individuals with incomplete data were excluded. Prevalent hypertension was defined as ‘doctor diagnosed’ and/or an elevated average systolic blood pressure (BP; ≥140mmHg) or diastolic BP (≥90mmHg). OSA was diagnosed when apnoea hypopnoea index (AHI) ≥10 events/hour from in-laboratory polysomnography. Chronotype was determined from actigraphy mid-sleep time on work free days. Tertiles of mid-sleep time were used to categorise morning, intermediate and evening chronotypes. Logistic regression (adjusted for sex, body mass index, age, alcohol consumption and sleep duration) were used to assess the cross-sectional relationship between chronotype, OSA and hypertension. Results After applying exclusion criteria 496 participants were analysed (female=58%; age mean[range]=57.0[42.1–81.6] years). All those with OSA had greater odds of hypertension than those without and there was no difference in risk of hypertension according to chronotype. Compared to morning chronotypes with no OSA (n=84), evening chronotypes with OSA (n=79) had non-significantly increased odds (OR 2.15, 95% CI 1.00–4.76; P=0.054) for hypertension while morning chronotypes with OSA (n=82) had significantly increased odds (OR 3.02, 95% CI 1.44–6.58; P=0.004). Discussion Morning chronotypes with OSA might be at increased risk of hypertension compared to evening chronotypes with OSA.

Association of chronotype and pain at baseline in ovarian cancer survivors participating in a lifestyle intervention (NRG/GOG 0225).

6018 Background: Chronotype is defined as an individual’s propensity to sleep at a specific time in a 24-hour cycle with late chronotype associated with poorer health outcomes including cancer. Chronotype remains relatively undefined in ovarian cancer. The Lifestyle Intervention for oVarian cancer Enhanced Survival (LIVES) study is testing whether 1205 women randomized to a diet and physical activity intervention for 24-months will have longer progression-free survival versus an attention control. Here we determine the association of late and early vs mid chronotypes and patient reported outcomes (PROs), lifestyle behaviors and biomarkers of metabolic health and inflammation in ovarian cancer survivors post-treatment (≤ 6.5 months). Methods: Chronotype was determined using self-reported time to bed (early &lt; 9 pm; mid ≥ 9 pm - ≤12 am; late &gt; 12 am) captured through the Pittsburg Sleep Quality Index and PROs were measured using subscales of the Rand-36 questionnaire. Validated questionnaires for diet and physical activity were used and biomarkers were collected at routine clinic visits. A total subsample of 438 ovarian cancer survivors enrolled in NRG/GOG 0225- LIVES study with all available baseline measures were included in analyses. Descriptive statistics, general linear mixed models, and Pearson correlations were performed. Results: Reported pain was significantly higher in late chronotypes (P &lt; 0.05) when compared to early and mid-chronotypes. Total sleep duration was significant between the 3 chronotypes (P &lt; 0.05) with late chronotype experiencing less sleep (6.77 ± 1.67 hrs) than mid chronotype (7.04 ± 1.31 hrs) and early chronotype (7.56 ± 1.33 hrs). Higher reported pain was significantly correlated to poorer CRP levels (r = -0.198, P &lt; 0.001) suggesting higher systemic inflammation and poorer blood insulin levels (r = -0.116, P &lt; 0.05) independent of chronotype classification. All other subscales of the RAND 36 and physical activity were not associated with chronotype. Diet quality trended towards significance with a positive association observed in early and an inverse association in late chronotypes (P = 0.06). Conclusions: Late chronotypes reported higher levels of pain which was associated with poorer sleep and diet quality and higher levels of inflammation and insulin. More robust data, including actigraphy, are being analyzed and will provide additional insight of the role of circadian rhythm and phenotype on pain and key biomarkers in ovarian cancer survivors. Clinical trial information: NCT00719303.

Abstract MP29: Chronotype is Associated With Diet Quality and Energy Intake, and Dietary Energy Density Mediates a Relation of Chronotype With Cardiovascular Health in a Diverse Sample of US Women

Background: An individual’s chronotype, the innate preference for the timing of behaviors such as eating and sleeping, has been linked to various health outcomes. Indeed, we recently demonstrated that evening chronotype was related to poorer cardiovascular health (CVH) in US women. However, the associations of chronotype with specific health behaviors are not well characterized in this population. This is particularly true for diet, the CVH metric for which recommendations are least likely to be met. Therefore, the current study examined the association of chronotype with diet and the role of diet in the chronotype-CVH relation in a diverse sample of women. Hypotheses: Evening chronotype will be associated with higher energy intake and poorer diet quality, including higher dietary energy density (ED), the total kcal per weight of food consumed and an index of the types and amounts of food eaten; these diet factors will mediate an association of chronotype with CVH. Methods: Baseline data from 506 participants enrolled in the AHA Go Red for Women SFRN were examined. Women were 20-76 y of age (mean±SD: 37±16 y); 49% had overweight/obesity and 61% were racial/ethnic minority. Women were categorized as either morning/intermediate or evening chronotype based on their Morningness/Eveningness Questionnaire scores. Dietary ED and daily intakes of food [by weight (g) and energy (kcal)], nutrients (g/1000 kcal), and fruits and vegetables [FV (servings/1000 kcal)] were assessed using the validated Block Brief Food Frequency Questionnaire. Linear regression models were used to examine associations of chronotype with diet. Causal mediation analyses tested whether dietary ED or energy intake mediated a relation between chronotype and CVH (AHA Life’s Simple 7 score). Models were adjusted for age, BMI, race/ethnicity, education, and health insurance. Results: On average, women consumed 1433±862 kcal with a dietary ED of 1.44±0.40 kcal/g. Evening (n=64) vs. morning/intermediate (n=442) chronotype was associated with higher dietary ED (β=0.21, P=0.0001), energy intake (β=448, P=0.0001), and weight of food consumed (β=129.3, P=0.06). Evening chronotype was also related to greater consumption of animal protein (β=1.1, P=0.04) and lower intakes of plant protein (β=-0.66, P=0.006), fiber (β=-2.2, P=0.0005), and FV (β=-1.3, P&lt;0.0001). Dietary ED was a significant partial mediator of the association between chronotype and CVH (percent mediated: 28%, P=0.01). Results were similar when chronotype was analyzed on the continuous scale. Conclusions: In a diverse sample of women, evening chronotype was associated with a less heart-healthy diet, including greater energy intake and poorer diet quality. Moreover, that dietary ED partially mediated the relation between evening chronotype and poor CVH suggests that behavioral interventions to reduce dietary ED may improve CVH in women with evening chronotype.

Association of Chronotype, Road Traffic Accidents, and Polymorphisms in Genes Linked with the Biological Clock and the Dopaminergic System

Objective. To study the association between single-nucleotide polymorphisms (SNP) of the RORA (rs1159814), CLOCK (rs12649507), PER3 (rs2640909), NPSR1 (rs324981), NPAS2 (rs4851377), DRD3 (rs6280), SLC6A3 (rs6347), and DBH (rs1611125) genes, chronotype parameters, and road traffic accident (RTA) driver statistics. Materials and methods. The study included 303 drivers of Moscow inter-city buses working rolling shifts. The study addressed associations between genotyping results for SNP and the Munich Chronotype Questionnaire (MCTQ) and the Shortened Sleep-Wake Pattern Assessment Questionnaire (SWPAQ), and official RTA statistics. Results and conclusions. The cohort was dominated by the mixed chronotype, with a tendency to go to bed late and able to get up early; there was a marked shift between sleep patterns between working days and rest days. The SNP of the PER3 gene showed an association with parameters of morning activity. The SNP of the CLOCK gene was associated with a change in the pattern and the risk of causing RTA, while the minor alleles of the NPSR1 and SLC6A3 genes were associated with a later chronotype and an increase in RTA risk. It is suggested that these polymorphism may be among the genetic factors linking the chronotype to the ability to work.

Time to rethink sleep quality: PSQI scores reflect sleep quality on workdays.

The Pittsburgh Sleep Quality Index (PSQI) is the most common measure of sleep quality. Its questions refer to "usual" sleep habits during the last month. Considering how different sleep-wake behavior can be between workdays and work-free days, we hypothesized that sleep quality should show similar differences. We investigated these potential differences in a cross-sectional online study using the original and two adapted versions of the PSQI that replaced "usual" by explicitly referring to sleep on workdays or work-free days. Additionally, we investigated how these scores relate to chronotype and social jetlag assessed by the Munich ChronoType Questionnaire. Participants were recruited online, they had to be older than 18 years, following regular weekly work schedules, and they should not be shift workers. Repeated-measures analysis of variance was used to compare the three different versions of the PSQI (usual, work, and work-free). To find out whether PSQI score differences could be predicted by chronotype and/or social jetlag a mediation analysis was carried out. Workday PSQI scores were similar to the original "usual" scores, two points higher than the PSQI score on work-free days and above the cutoff designating poor sleep quality. PSQI components and time variables also differed between workdays and work-free days. Chronotype correlated with the difference between PSQI scores on workdays and on work-free days, an association mediated by social jetlag. Our results suggest that the original PSQI predominantly reports sleep quality on workdays and that work schedules may affect sleep quality. The mediation of social jetlag on the association of chronotype and PSQI score differences could mean that not chronotype per se, but rather the collision of an individuals' chronotype with fixed work schedules explains the differences between sleep on workdays and work-free days. Understanding how sleep quality differs between workdays and work-free days, how this difference can adequately be assessed through directing participants to focus on their sleep specifically on workdays vs. work-free days, and how circadian factors modulate this difference, is crucial to improve sleep quality.

Association of chronotype and social jetlag with human non-verbal intelligence

ABSTRACTThe aim of this study was to evaluate the effects of chronotype and social jetlag (SJL) on intelligence. Subjects were aged 14–25 years (n = 1008). A significant effect of intelligence on academic performance, as measured by the Raven’s Standard Progressive Matrices test, was found (F2,917 = 11.75, P < 0.0001, η2 = 0.03). When SJL was less than 2 hours, the intelligence of people with late chronotype was found to be higher than that of subjects with early and intermediate chronotypes (F2,305 = 3.12, P < 0.05, η2 = 0.02). A negative effect of SJL on the results of intelligence testing was noted only in subjects with late chronotype (F2,536 = 2.61, P < 0.05, η2 = 0.02). Our data suggest that people with late chronotype have a higher level of intelligence, but these advantages disappear when SJL ≥2 hours.

An assessment of chronotype and social jetlag among Filipinos

Chronotype is a measure of an individual's timing of sleep and wakefulness. It describes the relationship between an external time and a person's internal biological time. The chronotype has been used to characterize human circadian trait. Differences in chronotypes are believed to be related to genetic variation, location, geographic and cultural factors. Determination of chronotype using quantitative approaches has been done in Europe for more than a decade now through the Munich Chronotype Questionnaire (MCTQ). In this approach, the chronotype is quantified by the midpoint time between the start and end of sleep during free days, corrected for sleep duration on work days. The calculated time classifies whether an individual has an early or late chronotype. In the Philippines, there is no existing data for chronotypes as well as social jetlag - the discrepancy between an individual's internal time and social clock. In this study, we provide a quantitative description of chronotypes and social jetlag among Filipinos. We present preliminary results based on the 895 non-shift worker respondents of the PhilMCTQ, a language variant of the MCTQ for the Philippine population. Using this set of data, we determined the association of chronotype and social jetlag against certain factors, i.e., age, gender, self- assessed exposure to natural light, type of location (whether living in the urban or rural area), travel time to/from work, sleep duration, and body mass index. Observations concerning the relationship of chronotype and gender, age and social jetlag that have been previously reported in other populations are also seen in our data. Increased social jetlag has been observed among people with late chronotypes among our respondents. There were also some differences in chronotypes between genders, age groups, dwelling locations and consumers of stimulants (i.e., beer, liquor and cigarettes). Both Metro City and Non-Metro City residents similarly experience social jetlag. The data show that as commuting time becomes longer, social jetlag slightly increases. Differences in social jetlag have been observed between age groups and certain stimulants (e.g., smoking, coffee drinking) have been shown to be associated with social jetlag. Other factors such as gender, dwelling location, time spent outdoors and body mass index did not show sufficient evidence of association or correlation with social jetlag among the study participants.

The role of sleep in understanding individual differences among chronotypes

Studies have shown that chronotypes differ not only in their preferred bed- and rising times, but also in sleep quality, problems falling asleep or daytime sleepiness. Due to their delayed circadian phase position, evening-types appear to be at higher risk of suffering from impaired sleep. We investigated the role of sleep-related parameters in the association of chronotype and psychological outcome measures, namely perceived stress, health-related quality of life (HRQoL) and achievement motivation in adolescents and young adults. Eveningness and higher subjectively perceived stress was mediated by sleep quality. Insomnia symptoms and sleep-related cognitions play a decisive role in explaining reduced HRQoL in evening-types. Learning motivation was affected by chronotype, but this relationship was mediated by daytime sleepiness. Symptoms of disturbed sleep act as intermediary in the association of eveningness and reduced psychosocial functioning. Improving sleep by psychotherapeutic interventions might help to reduce the psychological strain in young evening-types.