Early chronotype with advanced activity rhythms and dim light melatonin onset in a rural population

Late evening electric light exposure is associated with low sleep regularity in adolescents living in rural areas

In this study, we tested the prediction that sleep regularity would be lower in adolescents exposed to late evening electric light (LEEL) than in those without exposure to it. The Sleep Regularity Index was calculated based on actigraph recordings from adolescents living in rural communities in Argentina and Brazil that were either exposed to LEEL or not. The effect of the LEEL on sleep variables was tested using linear models considering sex and age, as well as accounting for the differences between countries. Sleep onset was delayed, sleep duration shortened, and Sleep Regularity Index was 4 [1-8] points lower in the group exposed to LEEL (p = .0176, eta2 =0.13). Our results show that beyond sleep phase and duration, which are known to be affected by LEEL in this age group, sleep irregularity should also be considered as an important outcome variable when assessing the adverse effects of evening light on adolescents.

Distribution of dim light melatonin offset (DLMOff) and phase relationship to waketime in healthy adults and associations with chronotype

OBJECTIVES

Dim light melatonin onset, or the rise in melatonin levels representing the beginning of the biological night, is the gold standard indicator of circadian phase. Considerably less is known about dim light melatonin offset, or the decrease in melatonin to low daytime levels representing the end of the biological night. In the context of insufficient sleep, morning circadian misalignment, or energy intake after waketime but before dim light melatonin offset, is linked to impaired insulin sensitivity, suggesting the need to characterize dim light melatonin offset and identify risk for morning circadian misalignment.

METHODS

We examined the distributions of dim light melatonin offset clock hour and the phase relationship between dim light melatonin offset and waketime, and associations between dim light melatonin offset, phase relationship, and chronotype in healthy adults (N = 62) who completed baseline protocols measuring components of the circadian melatonin rhythm and chronotype.

RESULTS

74.4% demonstrated dim light melatonin offset after waketime, indicating most healthy adults wake up before the end of biological night. Later chronotype (morningness-eveningness, mid-sleep on free days corrected, and average mid-sleep) was associated with later dim light melatonin offset clock hour. Later chronotype was also associated with a larger, positive phase relationship between dim light melatonin offset and waketime, except for morningness-eveningness.

CONCLUSIONS

These findings suggest morning circadian misalignment risk among healthy adults, which would not be detected if only dim light melatonin onset were assessed. Chronotype measured by sleep timing may better predict this risk in healthy adults keeping a consistent sleep schedule than morningness-eveningness preferences. Additional research is needed to develop circadian biomarkers to predict dim light melatonin offset and evaluate appropriate dim light melatonin offset timing to promote health.

Behavioural Parameters of Circadian Rhythm Are Not Correlated with Dim Light Melatonin Onset: An Observational Study on Healthy Volunteers

Dim light melatonin onset (DLMO) is considered the most reliable marker of the circadian rhythm phase in humans. DLMO may moderately correlate with sleep onset and sleep offset time. There are no sufficient data about the correlations between DLMO and clinical scales assessing sleep quality and daytime symptoms of poor night sleep. The aim of the study was to determine the association between DLMO and basic sleep parameters from actigraphy and sleep diaries, as well as the association between DLMO and the following insomnia clinical scales: the Athens Insomnia Scale (AIS), Insomnia Severity Index (ISI), Epworth Sleepiness Scale (ESS), and chronotype questionnaires: Morningness-Eveningness Questionnaire (MEQ) and Composite Scale of Morningness (CSM). Participants of the study were healthy volunteers. Sleep parameters were measured by sleep diaries and actigraphy, and the following clinical scales: the AIS, ISI, and ESS, and chronotype questionnaires: MEQ and CSM. DLMO was calculated based on plasma melatonin concentration. The blood samples were collected hourly at five time points between 20:00 and 00:00 during the session in dim red light (<50 lux). Melatonin concertation was determined by LC-MS/MS. Twenty-one volunteers participated in the study. DLMO was calculated in 12 participants. There was a significant correlation between DLMO and ISI (r = 0.60, p = 0.038) and ESS (r = 0.61, p = 0.034). The correlation coefficient between the DLMO and the AIS was also high, however insignificant (r = 0.57, p = 0.054). There were no significant correlations between DLMO and chronotype scales MEQ and CSM. DLMO did not correlate with sleep onset and sleep offset; however, DLMO correlated with the Sleep Fragmentation Index (SFI) (r = 0.67, p = 0.017). DLMO is associated with poorer sleep maintenance, a stronger feeling of insomnia, and sleepiness during the day. Simultaneously, chronotype pattern and circadian rhythm parameters do not correlate with DLMO. Biological circadian rhythm does not reflect the real-life sleep-wake rhythm, indicating that the lifestyle is more often disconnected from the biological clock.

Individual light history matters to deal with the Antarctic summer

The effect of light, main zeitgeber of the circadian system, depends on the time of day it is received. A brief trip to the Antarctic summer (ANT) allowed us to explore the impact of a sudden and synchronized increase in light exposure on activity-rest rhythms and sleep patterns of 11 Uruguayan university students, and to assess the significance of light history in determining individual circadian phase shift. Measurements collected in the peri-equinox in Montevideo, Uruguay (baseline situation, MVD) and in ANT, included sleep logs, actigraphy, and salivary melatonin to determine dim-light melatonin onset (DLMO), the most reliable marker of circadian phase. The increase in light exposure in ANT with respect to MVD (affecting both light-sensitive windows with opposite effects on the circadian phase) resulted in no net change in DLMO among participants as some participants advanced their DLMO and some others delayed it. The ultimate cause of each participant's distinctive circadian phase shift relied on the unique change in light exposure each individual was subjected to between their MVD and ANT. This study shows an association between the individual light history and the circadian phase shift.

Associations between sleep characteristics, chronotype and body mass index among Chinese college freshmen

Research indicates that sleep problem is a behavioral risk factor of obesity. However, few research have applied a multi-dimensional approach to investigate the relationship between sleep health and adiposity. Therefore, the current study aimed to examine the associations of sleep characteristics (duration, quality) and chronotype with overweight/obesity as measured by body mass index. Data were obtained from 2014 college students from the Dali University in the Yunnan province of China in the year 2021. Sleep characteristics and chronotype were measured using self-reported questionnaires. The presence of overweight/obesity was assessed by anthropometric measurements. Multiple logistic regression models and restricted cubic spline hazard models were established to examine associations between sleep characteristics, chronotype and adiposity. After adjusting for demographic characteristics and other obesity-related behavioral risk factors, evening type was positively associated with overweight/obesity, and an L-shaped dose-effect relationship was observed between chronotype scores and the presence of overweight/obesity. However, sleep duration and quality were not associated with the presence of overweight/obesity in the logistic regression models and restrictive cubic splines models. This study indicated that Chinese college students who had the evening chronotype were more likely to be affected by overweight/obesity. Chronotype as an important dimension of sleep health should be incorporated in obesity intervention programs.

Evening types as determined by subjective and objective measures are more emotional eaters

OBJECTIVE

This study aimed to determine the association between being an evening type (ET; defined subjectively by the Morning-Evening Questionnaire or objectively by the dim-light melatonin onset [DLMO] timing) and reporting emotional eating (EE) behaviors.

METHODS

Cross-sectional analyses were conducted in 3964 participants (four international cohorts: ONTIME and ONTIME-MT [both Spain], SHIFT [the US], and DICACEM [Mexico]), in which chronotype (Morning-Evening Questionnaire), EE behaviors (Emotional Eating Questionnaire), and dietary habits (dietary records or food-frequency questionnaire) were assessed. Among 162 participants (ONTIME-MT subsample), additional measures of DLMO (physiological gold standard of circadian phase) were available.

RESULTS

In three populations, ETs presented with a higher EE score than morning types (p < 0.02); and they made up a higher proportion of emotional eaters (p < 0.01). ETs presented with higher scores on disinhibition/overeating as well as food craving factors and experienced these behaviors more frequently than morning types (p < 0.05). Furthermore, a meta-analysis showed that being an ET was associated with a higher EE score by 1.52 points of a total of 30 points (95% CI: 0.89-2.14). The timing of DLMO in the early, intermediate, and late objective chronotypes occurred at 21:02 h, 22:12 h, and 23:37 h, with late types showing a higher EE score (p = 0.043).

CONCLUSIONS

Eveningness associated with EE in populations with different cultural, environmental, and genetic backgrounds. Individuals with late DLMO also showed more EE.

Validation of the Munich Chronotype Questionnaire (MCTQ) in Chinese college freshmen based on questionnaires and actigraphy

The Munich Chronotype Questionnaire (MCTQ) was developed to determine an individual's chronotype, and it provides information about sleep and wake times separately for work and free days. However, the MCTQ has not been effectively verified using a large sample based on multiple questionnaires and actigraphy measures. Three sequential studies were conducted. Study 1 used a large sample (n = 1066) to investigate the chronotype of Chinese college freshmen and assess the validity of the MCTQ compared with the reduced Morningness-Eveningness Questionnaire (rMEQ), actigraphy, and other related questionnaires. Study 2 verified the MCTQ compared with a sleep diary. Study 3 examined the test-retest reliability of the MCTQ at the 2-year follow-up. The results showed that MCTQ parameters were significantly associated with rMEQ scores, the actigraphy-based mid-point of sleep, sleep quality, depression, and trait anxiety. In addition, all MCTQ variables were significantly related to the diary-based sleep mid-point. The test-retest reliability of the mid-point of sleep adjusted for sleep debt (MSFsc) and mid-point of sleep on free days (MSF) was acceptable. These results indicate that the MCTQ is a practical and efficient tool with good reliability. Its further development is important for the accurate assessment of chronotypes and clinical diagnoses of sleep.

Validation of the Self-Rating of Biological Rhythm Disorder for Adolescents (SBRDA) Scale by Dim Light Melatonin Onset in Healthy Young Adults

Understanding the biological rhythms that influence young adult health is vital because the combination of biological changes and a circadian phase delay lead to young adults being at high risk of circadian misalignment. We have previously established a self-rating of biological rhythm disorder for adolescents (SBRDA). However, we did not externally validate the SBRDA against objective measures of biological rhythms such as dim light melatonin onset (DLMO)-the gold standard of the endogenous circadian phase. The purpose of this study was to verify the effectiveness of SBRDA in identifying individuals with biological rhythm disorders. Our participants were 42 (47.2%) boys and 47 (52.8%) girls with an average age of 18.5 ± 1.2 years. Saliva samples were collected from 4 h before bed time to 2 h after sleep every 60 min in a dim-light (<50 lx) laboratory environment. Biological rhythm parameters were assessed using questionnaires, including SBRDA, MEQ, and MCTQ. The mean DLMO time (h) was 22.2 ± 1.9. The DLMO correlated significantly with the SBRDA score (r = 0.33, p < 0.001), MEQ score (r = -0.24, p < 0.05), and MSFsc (r = 0.26, p < 0.05). ROC curve analysis showed that SBRDA was of diagnostic value for biological rhythm disorder (p < 0.05). Our observations demonstrate that SBRDA, which is consistent with MEQ and MCTQ, can be used to reflect endogenous circadian rhythm disorders in young adults. Exposure to dim light may activate melatonin secretion and lead to an earlier peak in young adults with biological rhythm disorder.

Delayed circadian rhythms in older Africans living with human immunodeficiency virus (HIV)

The increasing number of people living with human immunodeficiency virus, HIV, (PLWH) have an elevated incidence of risk for noncommunicable comorbidities, the aetiology of which remains incompletely understood. While sleep disturbances are often reported in PLWH, it is unknown to what extent they relate to changes in the circadian and/or sleep homeostatic processes. We studied the relationship between sleep characteristics, circadian phase, and HIV status in older adults from the HAALSI (Health and Ageing in Africa: a Longitudinal Study of an INDEPTH Community in South Africa) subsample of the Agincourt Health and Demographic Surveillance System in South Africa (n = 187, 36 human immunodeficiency virus positive [HIV+], age: 66.7 ± 11.5 years, range 45-93 years), where HIV prevalence is high and (in contrast to the global north) does not associate significantly with potentially confounding behavioural differences. In participants with valid actigraphy data (n = 172), regression analyses adjusted for age and sex indicated that HIV+ participants had slightly later sleep onset (β = .16, p = .039), earlier sleep offset times (β = -.16, p = .049) and shorter total sleep times (β = -.20, p = .009) compared to the HIV negative (HIV-) participants. In a subset of participants (n = 51, 11 HIV+), we observed a later dim light melatonin onset (DLMO) in HIV+ (21:16 ± 01:47) than in HIV- (20:06 ± 00:58) participants (p = .006). This substantial difference remained when adjusted for age and sex (β = 1.21; p = .006). In 36 participants (6 HIV+) with DLMO and actigraphy data, median phase angle of entrainment was -6 min in the HIV+ group and +1 h 25 min in the HIV- group. DLMO time correlated with sleep offset (ρ = 0.47, p = .005) but not sleep onset (ρ = -0.086, p = .623). Collectively, our data suggest that the sleep phase occurred earlier than what would be biologically optimal among the HIV+ participants. This is the first report of a mistimed circadian phase in PLWH, which has important potential implications for their health and well-being, especially given the well-established relationships between circadian asynchrony and sleep deprivation with poorer health outcomes.

Actigraphic and melatonin alignment in older adults with varying dementia risk

Circadian rhythms alter with ageing and may be aetiologically linked to neurodegeneration. This study explored the association between clinical markers and 1) dim light melatonin onset (DLMO) time and 2) phase angle derived from sleep midpoint, in older adults with varying dementia risks. Participants completed 14 days of actigraphy followed by in-lab measurement of salivary melatonin, from which DLMO time and phase angle were computed. Eighty participants (age = 65.5, SD = 9.6), 44 males (55%), MMSE (28.6, SD = 1.5) were included in the analysis. Sex (t = 2.15, p = .04), sleep onset (r = 0.49, p < .001) and midpoint (r = 0.44, p < .001) also correlated with DLMO time. Multiple linear regression showed chronotype, average actigraphy-derived light exposure during the DLMO window (window 2 h prior to DLMO to 2 h post), early biological day (6-10 h post DLMO time) and late biological day (10-14 h post DLMO time) were predictive of DLMO time (adjusted R² = 0.75). Sleep offset, depression severity, average light exposure during the early biological night and early and late biological day were shown to be predictive variables in the estimation of phase angle (adjusted R² = 0.78). The current study highlights the potential use of clinical variables, such as actigraphy-derived light, as circadian markers in ageing which could be easily implemented into existing clinical practice and could yield potential targets focusing on chronotherapeutic interventions.

Circadian Regulation of Hormonal Timing and the Pathophysiology of Circadian Dysregulation

Circadian rhythms are endogenously generated, daily patterns of behavior and physiology that are essential for optimal health and disease prevention. Disruptions to circadian timing are associated with a host of maladies, including metabolic disease and obesity, diabetes, heart disease, cancer, and mental health disturbances. The circadian timing system is hierarchically organized, with a master circadian clock located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus and subordinate clocks throughout the CNS and periphery. The SCN receives light information via a direct retinal pathway, synchronizing the master clock to environmental time. At the cellular level, circadian rhythms are ubiquitous, with rhythms generated by interlocking, autoregulatory transcription-translation feedback loops. At the level of the SCN, tight cellular coupling maintains rhythms even in the absence of environmental input. The SCN, in turn, communicates timing information via the autonomic nervous system and hormonal signaling. This signaling couples individual cellular oscillators at the tissue level in extra-SCN brain loci and the periphery and synchronizes subordinate clocks to external time. In the modern world, circadian disruption is widespread due to limited exposure to sunlight during the day, exposure to artificial light at night, and widespread use of light-emitting electronic devices, likely contributing to an increase in the prevalence, and the progression, of a host of disease states. The present overview focuses on the circadian control of endocrine secretions, the significance of rhythms within key endocrine axes for typical, homeostatic functioning, and implications for health and disease when dysregulated. © 2022 American Physiological Society. Compr Physiol 12: 1-30, 2022.

Sleep quality and neurohormonal and psychophysiological accompanying factors in adolescents with depressive disorders: study protocol

BACKGROUND

Depressive disorders are common mental health problems during adolescence. Many adolescents with depression describe difficulties with sleeping. Findings of previous studies regarding changes in objective sleep quality in adolescents with depressive disorders are heterogeneous.

AIMS

This study aims to investigate differences in objective and subjective sleep quality between adolescents with depressive disorders and healthy peers, and to evaluate if potential changes in sleep occur concurrently with changes in the release of cortisol and alpha-amylase after awakening.

METHOD

This non-interventional parallel study examines correlations between depressive disorders, sleep quality and release of stress hormones. Sleep quality in the past 2 weeks, severity of depressive symptoms, psychiatric comorbidities and stress response of 30 adolescents with depressive disorders and 30 healthy controls (N = 60) are assessed via questionnaires. In participants' home environments, the objective sleep quality of seven consecutive nights is measured by sleep accelerometry. After awakening, participants answer sleep questionnaires to examine the subjective sleep quality of those nights. Furthermore, salivary cortisol and alpha-amylase are measured three times after awakening (+0 min, +30 min and +45 min after awakening).

CONCLUSIONS

Sleep is an important factor for prognosis and well-being in adolescents with depression. The results of this study can be highly valuable to integrate a more detailed examination of sleep quality and sleeping impairments in the treatment of adolescent depressive disorders.

Validation of the Chinese version of the Munich Chronotype Questionnaire (MCTQHK) in Hong Kong Chinese youths

Chronotype, referred to as an individual's diurnal preference of timing for rest and activity, can be subjectively measured using the Munich Chronotype Questionnaire (MCTQ). However, the validity of MCTQ has yet to be tested in the youth population. In addition, it remains uncertain if MCTQ is a good measure of chronotype in individuals with insomnia. The current study aimed to validate the Chinese version of MCTQ (MCTQ^HK) in the youth population and to explore the utility of MCTQ^HK in individuals with insomnia. The original MCTQ was translated into Chinese language using the translation-back-translation method. Part one of this study included 988 youths who completed a battery of self-report questionnaires online consisting of the MCTQ^HK and the morningness-eveningness questionnaire (MEQ) for the measures of circadian preference, Insomnia Severity Index (ISI) to assess insomnia symptoms, and Patient Health Questionnaire (PHQ-9) to measure depressive symptoms. Test-retest reliability was examined in 442 participants at one-month follow-up. Of the overall sample, 69 participants were randomly drawn to complete the second part of the study, which included prospective 7-day actigraphy monitoring and a further subset (n = 40) additionally completed a laboratory-based assessment of dim-light melatonin onset (DLMO) as a circadian phase marker. A total of 659 participants with valid responses were finally included in the analyses of the data collected from part one of the study (female = 67.7%; mean age: 20.7 ± 2.02). Results showed that MCTQ parameters, namely the midpoint of sleep on free days (MSF), midpoint of sleep on workdays (MSW), and midpoint of sleep adjusted for sleep debt (MSFsc), were significantly correlated with MEQ score (r = -.514 to -.650, p < .01). Test-retest reliability for MCTQ^HK was good (intraclass correlation = 0.75 to 0.84). Later MSFsc was significantly associated with greater insomnia and depressive symptoms after controlling for age and sex. All MCTQ parameters showed significant correlations with actigraphy-based midpoint of sleep and circadian rhythm parameters, i.e., acrophase and L5 onset (r = .362 to .619, p < .01), as well as DLMO (r = .393 to .517, p < .05). The associations remained significant after controlling for age. MSFsc derived from MCTQ was significantly correlated with MEQ score in both the healthy sleepers and participants with insomnia (as defined by ISI > 14), r = -.600, p < .001 and r = -.543, p < .001, respectively. The present study demonstrated that MCTQ^HK is suitable for assessing chronotype with good reliability and validity in Chinese youths and supported the utility of MCTQ^HK in individuals with insomnia.

Sleep Under Preindustrial Conditions: What We Can Learn from It

Human sleep is regulated by light in two fundamental ways: The light-dark (LD) cycle entrains a circadian clock that in turn regulates sleep timing, and light per se can acutely inhibit sleep. Throughout evolution, these sleep regulatory systems became highly sensitive to the effects of light and they can be affected by the relatively low light intensities that are used indoors. Thus, postindustrial living conditions have created built environments that have isolated humans from the natural LD cycle and exposed them to an artificial one that can affect daily sleep timing. Studying indigenous communities that have differential access to electricity, as well as communities living in highly urbanized areas, we and others have shown that human access to artificial light has delayed the daily onset of sleep but has had a smaller effect on its offset, leading to an overall reduction in sleep duration that is pervasive in modern societies. In this chapter we discuss these studies, highlight their main findings, and point to their limitations.

Compared Heritability of Chronotype Instruments in a Single Population Sample

It is well established that the oldest chronotype questionnaire, the morningness-eveningness questionnaire (MEQ), has significant heritability, and several associations have been reported between MEQ score and polymorphisms in candidate clock genes, a number of them reproducibly across populations. By contrast, there are no reports of heritability and genetic associations for the Munich chronotype questionnaire (MCTQ). Recent genome-wide association studies (GWAS) from large cohorts have reported multiple associations with chronotype as assessed by a single self-evaluation question. We have taken advantage of the availability of data from all these instruments from a single sample of 597 participants from the Brazilian Baependi Heart Study. The family-based design of the cohort allowed us to calculate the heritability (h²) for these measures. Heritability values for the best-fitted models were 0.37 for MEQ, 0.32 for MCTQ, and 0.28 for single-question chronotype (MEQ Question 19). We also calculated the heritability for the two major factors recently derived from MEQ, “Dissipation of sleep pressure” (0.32) and “Build-up of sleep pressure” (0.28). This first heritability comparison of the major chronotype instruments in current use provides the first quantification of the genetic component of MCTQ score, supporting its future use in genetic analysis. Our findings also suggest that the single chronotype question that has been used for large GWAS analyses captures a larger proportion of the dimensions of chronotype than previously thought.

Evening preference correlates with regional brain volumes in the anterior occipital lobe

Chronotype or diurnal preference is a questionnaire-based measure influenced both by circadian period and by the sleep homeostat. In order to further characterize the biological determinants of these measures, we used a hypothesis-free approach to investigate the association between the score of the morningness-eveningness questionnaire (MEQ) and the Munich chronotype questionnaire (MCTQ), as continuous variables, and volumetric measures of brain regions acquired by magnetic resonance imaging (MRI). Data were collected from the Baependi Heart Study cohort, based in a rural town in South-Eastern Brazil. MEQ and anatomical 1.5-T MRI scan data were available from 410 individuals, and MCTQ scores were available from a subset of 198 of them. The average MEQ (62.2 ± 10.6) and MCTQ (average MSFsc 201 ± 85 min) scores were suggestive of a previously reported strong general tendency toward morningness in this community. Setting the significance threshold at P > .002 to account for multiple comparisons, we observed a significant association between lower MEQ score (eveningness) and greater volume of the left anterior occipital sulcus (β = -0.163, p = .001) of the occipital lobe. No significant associations were observed for MCTQ. This may reflect the smaller dataset for MCTQ, and/or the fact that MEQ, which asks questions about preferred timings, is more trait-like than the MCTQ, which asks questions about actual timings. The association between MEQ and a brain region dedicated to visual information processing is suggestive of the increasingly recognized fluidity in the interaction between visual and nonvisual photoreception and the circadian system, and the possibility that chronotype includes an element of masking.

Weekly, seasonal, and chronotype-dependent variation of dim-light melatonin onset

In humans, the most important zeitgeber for entrainment is light. Laboratory studies have shown that meaningful changes in light exposure lead to phase shifts in markers of the circadian clock. In natural settings, light is a complex signal varying with external conditions and individual behaviors; nonetheless, phase of entrainment is assumed to be fairly stable. Here, we investigated the influence of season and weekly schedule (as indicators of variation in light landscapes) on phase of entrainment. Using a within-subjects design (N = 33), we assessed dim-light melatonin onset (DLMO) as a circadian phase marker in humans, on workdays and work-free days, in summer (under daylight saving time) and in winter, while also estimating sleep times from actimetry. Our mixed-model regressions show that both season and weekly structure are linked with changes in phase of entrainment and sleep. In summer, both DLMO and sleep times were about 1 hour earlier compared to winter, and sleep duration was shorter. On work-free days, DLMO and sleep times were later, and their phase relationship differed more relative to workdays. All these effects were stronger in later chronotypes (those who habitually sleep late). Our results confirm that phase of entrainment is earlier when stronger zeitgebers are present (summer) and show that it relates to midday or midnight rather than sunrise or sunset. Additionally, they suggest that late chronotypes are capable of rapid phase shifts each week as they move between workdays and work-free days, stimulating interesting questions about the stability of circadian phase under natural conditions.