Crosstalk between environmental light and internal time in humans

Relationship between Circadian System Status, Child-Pugh Score, and Clinical Outcome in Cirrhotic Patients on Waiting Lists for Liver Transplantation

Background/Objectives: Many patients suffering from liver cirrhosis are eventually added to waiting lists for liver transplantation whose priority is established based on scales such as the Child-Pugh score. However, two marker rhythms of the circadian system, motor activity and distal temperature, are not evaluated. Methods: To determine the relationship between the functional status of the circadian system and the Child-Pugh scale in patients awaiting liver transplantation, distal temperature, motor activity, and light exposure rhythms were monitored for a full week using a wrist device (Kronowise 6.0) in 63 patients (17 women, 46 men) aged between 20 and 76 years. Results: Circadian parameters (amplitude, regularity, and fragmentation) of motor activity rhythms, distal temperature, and light exposure worsen in close association with liver disease severity as assessed by using the Child-Pugh score. Likewise, the worsening of rhythmic parameters and liver disease is associated with a deterioration in the markers of the red series: count, hemoglobin, and hematocrit. Conclusions: These results indicate the utility of ambulatory monitoring of marker rhythms to complement the clinical information provided by the Child-Pugh scale and to help establish nutrition, physical exercise, and sleep guidelines that promote better survival and quality of life in these patients.

Sleep problems and circadian rhythm functioning in autistic children, autism with co-occurring attention deficit hyperactivity disorder, and typically developing children: A comparative study

LAY ABSTRACT

Sleep problems are common in autism spectrum disorder (ASD) and different factors can contribute to its occurrence in this population. Misalignment of the biological clock (our circadian system) has been described as one possible explanation. While there is a body of research on sleep problems, relatively less is known about circadian functioning and the specific population of autistic children with co-occurring attention deficit hyperactivity disorder (ADHD). Using an ambulatory circadian monitoring (ACM) system, which resembles a common watch, we gathered sleep parameters and the different rhythms obtained from measuring motor activity, light exposure and distal temperature in 87 autistic children and adolescents, 27 of whom were diagnosed with co-occurring ADHD, and 30 neurotypical children and adolescents as a comparison group. Autistic children and, especially, those with co-occurring ADHD showed greater motor activity during sleep which would be worth studying in future projects which could better define this restless sleep. Of note, we observed an atypical pattern of wrist temperature, with higher values in neurotypical children, followed by autistic children and, ultimately, those with co-occurring ADHD. Temperature is one of the most valuable factors evaluated here as it is closely connected to sleep-wakefulness and the hormone melatonin. Its special pattern during day and nighttime would support the hypothesis of an atypical secretion of melatonin in autistic individuals which would also link with the higher presence of sleep problems in this neurodevelopmental condition.

Effect of Personalized Blue-Enriched White Light Intervention on Rest-Activity and Light Exposure Rhythms in Mild and Moderate Alzheimer's Disease

OBJECTIVE

We aimed to examine the effectiveness of personalized light intervention using a blue-enriched light-emitting-diodes device on rest-activity rhythm (RAR) and light exposure rhythm (LER) in patients with mild and moderate Alzheimer's disease (AD).

METHODS

AD patients with poor sleep quality and/or insomnia symptoms were assigned into either an experimental group (EG) or control group (CG) in a single-blind design. Personalized light intervention was given at 9-10 h after individual dim light melatonin onset, lasting for 1 h every day for two weeks in the EG (77.36±5.79 years, n=14) and CG (78.10±7.98 years, n=10). Each patient of CG wore blue-attenuating sunglasses during the intervention. Actigraphy recording at home for 5 days was done at baseline (T0), immediate postintervention (T1), and at four weeks after intervention (T2). The variables of RAR and LER were derived using nonparametric analysis.

RESULTS

We found a significant time effect on the intradaily variability (IV) of RAR at T2 with respect to T0 (p=0.039), indicating reduced IV of RAR at four weeks after personalized light intervention regardless of blue-enriched light intervention. There was a time effect on the IV of LER at T1 with respect to T0 (p=0.052), indicating a reduced tendency in the IV of LER immediately after intervention.

CONCLUSION

Our personalized light intervention, regardless of blue-enriched light source, could be useful in alleviating fragmentation of RAR and LER in AD patients.

NREM-REM alternation complicates transitions from napping to non-napping behavior in a three-state model of sleep-wake regulation

The temporal structure of human sleep changes across development as it consolidates from the polyphasic sleep of infants to the single nighttime sleep episode typical in adults. Experimental studies have shown that changes in the dynamics of sleep need may mediate this developmental transition in sleep patterning, however, it is unknown how sleep architecture interacts with these changes. We employ a physiologically-based mathematical model that generates wake, rapid eye movement (REM) and non-REM (NREM) sleep states to investigate how NREM-REM alternation affects the transition in sleep patterns as the dynamics of the homeostatic sleep drive are varied. To study the mechanisms producing these transitions, we analyze the bifurcations of numerically-computed circle maps that represent key dynamics of the full sleep-wake network model by tracking the evolution of sleep onsets across different circadian (∼ 24 h) phases. The maps are non-monotonic and discontinuous, being composed of branches that correspond to sleep-wake cycles containing distinct numbers of REM bouts. As the rates of accumulation and decay of the homeostatic sleep drive are varied, we identify the bifurcations that disrupt a period-adding-like behavior of sleep patterns in the transition between biphasic and monophasic sleep. These bifurcations include border collision and saddle-node bifurcations that initiate new sleep patterns, period-doubling bifurcations leading to higher-order patterns of NREM-REM alternation, and intervals of bistability of sleep patterns with different NREM-REM alternations. Furthermore, patterns of NREM-REM alternation exhibit variable behaviors in different regimes of constant sleep-wake patterns. Overall, the sequence of sleep-wake behaviors, and underlying bifurcations, in the transition from biphasic to monophasic sleep in this three-state model is more complex than behavior observed in models of sleep-wake regulation that do not consider the dynamics of NREM-REM alternation. These results suggest that interactions between the dynamics of the homeostatic sleep drive and the dynamics of NREM-REM alternation may contribute to the wide interindividual variation observed when young children transition from napping to non-napping behavior.

Chronodisruption and Ambulatory Circadian Monitoring in Cancer Patients: Beyond the Body Clock

Purpose of Review

Circadian rhythms impose daily rhythms a remarkable variety of metabolic and physiological functions, such as cell proliferation, inflammation, and DNA damage response. Accumulating epidemiological and genetic evidence indicates that circadian rhythms’ disruption may be linked to cancer. The integration of circadian biology into cancer research may offer new options for increasing cancer treatment effectiveness and would encompass the prevention, diagnosis, and treatment of this disease.

Recent Findings

In recent years, there has been a significant development and use of multi-modal sensors to monitor physical activity, sleep, and circadian rhythms, allowing, for the very first time, scaling accurate sleep monitoring to epidemiological research linking sleep patterns to disease, and wellness applications providing new potential applications.

Summary

This review highlights the role of circadian clock in tumorigenesis, cancer hallmarks and introduces the state-of-the-art in sleep-monitoring technologies, discussing the eventual application of insights in clinical settings and cancer research.

Sleep Problems and Circadian Functioning in Children and Adolescents With Autism Spectrum Disorder

BACKGROUND

Sleep problems are a prevalent comorbidity in autism spectrum disorder (ASD) with a multifactorial basis in which circadian misalignment has been described.

METHODS

A cross-sectional study was conducted including 52 children and adolescents with ASD (9.85 ± 3.07) and 27 children and adolescent controls with normal intellectual functioning (8.81 ± 2.14). They were matched for age, sex, and body mass index, and all were drug-naïve. An ambulatory circadian monitoring device was used to record temperature and motor, body position, sleep, and light intensity.

RESULTS

Individuals with ASD presented longer sleep-onset latency, lower sleep efficiency, and decreased total sleep time and tended to be more sedentary and have less exposure to light. They also showed lower amplitude, low interdaily stability, and a different pattern of wrist temperature across the day, with a midpoint of sleep that did not concur with sleep midpoint indicated by the rest of circadian parameters.

CONCLUSIONS

The sleep problems observed in this sample resemble those reported previously, with the exception of nocturnal awakenings which did not show differences. The ambulatory circadian monitoring device enabled measurement of circadian parameters such as temperature which, until now, were scarcely described in children with ASD and could be used to better understand sleep and circadian system in ASD.

Functional links between thermoregulation and sleep in children with neurodevelopmental and chronic health conditions

The bi-directional relationship between sleep and wake is recognized as important for all children. It is particularly consequential for children who have neurodevelopmental disorders (NDDs) or health conditions which challenge their sleep and biological rhythms, and their ability to maintain rhythms of participation in everyday activities. There are many studies which report the diverse reasons for disruption to sleep in these populations. Predominantly, there is focus on respiratory, pharmaceutical, and behavioral approaches to management. There is, however, little exploration and explanation of the important effects of body thermoregulation on children's sleep-wake patterns, and associated behaviors. Circadian patterns of sleep-wake are dependent on patterns of body temperature change, large enough to induce sleep preparedness but remaining within a range to avoid sleep disturbances when active thermoregulatory responses against heat or cold are elicited (to maintain thermoneutrality). Additionally, the subjective notion of thermal comfort (which coincides with the objective concept of thermoneutrality) is of interest as part of general comfort and associated behavioral responses for sleep onset and maintenance. Children's thermoregulation and thermal comfort are affected by diverse biological functions, as well as their participation in everyday activities, within their everyday environments. Hence, the aforementioned populations are additionally vulnerable to disruption of their thermoregulatory system and their capacity for balance of sleep and wakefulness. The purpose of this paper is to present hitherto overlooked information, for consideration by researchers and clinicians toward determining assessment and intervention approaches to support children's thermoregulation functions and promote their subjective thermal comfort, for improved regulation of their sleep and wake functions.

Are we still in the dark? A systematic review on personal daily light exposure, sleep-wake rhythm, and mood in healthy adults from the general population

Insufficient light exposure is assumed to be related to a wide array of health problems, though few studies focus on the role of whole-day light exposure in the habitual setting in the development of these health problems. The current review aims to describe the association between personal light exposure in the habitual setting and sleep-wake rhythm and mood in healthy adults from the general population. Five databases (Embase, Medline Epub, Web of Science, PsycINFO, and Google Scholar) were searched in June 2019. The inclusion criteria included: assessment directly of light exposure on the participants for at least one full day; reporting on both individual personal light exposure and outcomes. The quality of the papers was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies of the National Heart, Lung and Blood Institute. The current review followed the PRISMA guidelines. In total, 8140 papers were identified in the database search. Twenty-five papers were eventually included in this review. All included studies were cross-sectional, and individual light exposure was usually measured with a wrist-worn device. Five studies received a "good" quality rating, 16 received a "fair" rating, and the remaining 4 a "poor" quality rating. The overall quality of the included studies was considered low because of the lack of intervention studies and the fact that light exposure was measured on the wrist. Given the low quality of the included studies, the current review can only provide a first exploration on the association between light exposure and sleep-wake rhythm and mood in healthy adults from the general population. Limited evidence is presented for a positive relationship between the amount and timing of light exposure on the one hand and rest-activity rhythm and some estimates of sleep architecture on the other. The evidence on an association between light exposure and circadian phase, sleep estimates, sleep quality, and mood is conflicting. Data from intervention studies are needed to gain insight into the causal mechanism of the relationship between light exposure and sleep-wake rhythm and mood.

The effects of seasons and weather on sleep patterns measured through longitudinal multimodal sensing

Previous studies of seasonal effects on sleep have yielded unclear results, likely due to methodological differences and limitations in data size and/or quality. We measured the sleep habits of 216 individuals across the U.S. over four seasons for slightly over a year using objective, continuous, and unobtrusive measures of sleep and local weather. In addition, we controlled for demographics and trait-like constructs previously identified to correlate with sleep behavior. We investigated seasonal and weather effects of sleep duration, bedtime, and wake time. We found several small but statistically significant effects of seasonal and weather effects on sleep patterns. We observe the strongest seasonal effects for wake time and sleep duration, especially during the spring season: wake times are earlier, and sleep duration decreases (compared to the reference season winter). Sleep duration also modestly decreases when day lengths get longer (between the winter and summer solstice). Bedtimes and wake times tend to be slightly later as outdoor temperature increases.

Impact of an intermittent and localized cooling intervention on skin temperature, sleep quality and energy expenditure in free-living, young, healthy adults

Where people live and work together it is not always possible to modify the ambient temperature; ways must therefore be found that allow individuals to feel thermally comfortable in such settings. The Embr Wave® is a wrist-worn device marketed as a 'personal thermostat' that can apply a local cooling stimulus to the skin. The aim of the present study was to determine the effect of an intermittent mild cold stimulus of 25 °C for 15-20 s every 5 min over 3.5 days under free-living conditions on 1) skin temperature, 2) perception of skin temperature, 3) sleep quality and 4) resting energy expenditure (REE) in young, healthy adults. Ten subjects wore the device for 3.5 consecutive days. This intervention reduced distal skin temperature after correcting for personal ambient temperature (P < 0.05), but did not affect the subjects' the perception of skin temperature, sleep quality or REE (all P ≥ 0.051). Thus, this intermittent mild cold regime can reduce distal skin temperature, and wearing it under free-living conditions for 3.5 days does not seem to impair the perception of skin temperature and sleep quality or modify REE.

Chronotype, Sleep, and Depressive Symptoms Among Chinese College Students: A Cross-Sectional Study

Objective: To describe the prevalence of chronotype and depressive symptoms among Chinese college students and to examine the association between chronotype and depressive symptoms.

Methods: From April to May 2019, a cross-sectional survey was conducted among 1,179 Chinese college students from 2 universities in Anhui and Jiangxi provinces. A total of 1,135 valid questionnaires were collected, the valid response rate was 98.6%. The questionnaire investigated age, gender, major, height, weight, only child status, living place, self-reported family economy, and self-reported study burden. The chronotype was assessed by the Morning and Evening Questionnaire (MEQ). Depressive symptoms and sleep quality were evaluated by the Patient Health Questionnaire 9 (PHQ-9) and the Pittsburgh Sleep Quality Index (PSQI), respectively. A Chi-square test was used to examine the proportion of depressive symptoms among Chinese college students with different demographic characteristics. The generalized linear model was used to analyze the relationships between chronotype and depressive symptoms.

Results: The proportion of morning types (M-types), neutral types (N-types), and evening types (E-types) of college students were 18.4, 71.1, and 10.5%, respectively. The proportion of mild depression, moderate depression, and moderate to severe depression of participants were 32.4, 6.0, and 4.2%, respectively. Compared to the M-types, after controlled for age, gender, major, sleep quality, self-reported study burden, father's education level, and self-reported family economy, depressive symptoms were positively correlated with E-types (OR = 2.36, 95% CI: 1.49–3.73).

Conclusions: There was a significant association between chronotype and depressive symptoms among Chinese college students. Further longitudinal studies were needed to clarify the causal relationship between chronotype and depressive symptoms.

Electrochromic selective filtering of chronodisruptive visible wavelengths

We present evidence of pupil response modification, as well as differential theoretical melatonin suppression through selective and dynamic electrochromic filtering of visible light in the 400-500 nm range to minimize chronodisruptive nocturnal blue light exposure. A lower activation of intrinsically photosensitive retinal ganglion cells (ipRGCs), the first step for light to reach a human's internal clock, is related to melatonin secretion therefore avoiding detrimental effects of excessive blue light exposure. Pupillary Light Reflex and Color Naming were experimentally assessed under light filtered by two different coloration states (transmissive and absorptive) of these novel dynamic filters, plus an uncoated test device, in 16 volunteers. Also, different commercial light sources at illuminances ranging from 1 to 1000 lux were differentially filtered and compared in terms of theoretical melatonin suppression. Representative parameters of the pupil responses reflected lower pupil constriction when the electrochromic filters (ECFs) were switched on (absorptive state, blue light is absorbed by the filter) compared to uncoated filters (control sample), but failed to do so under transmissive state (blue light passes through the filter) indicating less activation of ipRGCs under absorptive state (although no significant differences between states was found). Out of eight colors tested, just one showed significant differences in naming between both filter states. Thus, the ECF would have some protecting effect on ipRGC activation with very limited changes in color perception. While there are some limitations of the theoretical model used, the absorptive state yielded significantly lower theoretical melatonin suppression in all those light sources containing blue wavelengths across the illuminance range tested. This would open the way for further research on biological applications of electrochromic devices.

Evening types have social jet lag and metabolic alterations in school-age children

Chronotype has been mostly assessed with subjective scales. Objective assessment has been undertaken with actigraphy, although problems may occur in classifying chronotype. The aims of the study were to assess chronotype in school-age children using a novel integrative measurement (TAP) derived from non-invasive assessments of wrist temperature (T) physical activity (A) and body position (P) and to explore associations between chronotype, sleep disturbances, and metabolic components. Four-hundred-thirty-two children of 8-12 years were recruited from a Mediterranean area of Spain. Measurements were: (a) Chronotype objectively (7-day-rhythms of TAP) and subjectively measured (Munich-chronotype-self-reported questionnaire); (b) sleep rhythms and light exposition; (c) 7-day-diaries of food intake; (d) anthropometry and metabolic parameters; (e) academic scores. TAP acrophase was able to assess eveningness. As compared to more morning-types, more evening-types displayed lower amplitude in temperature rhythms, increased physical activity in the evening, delayed sleep and midpoint of intake and had more frequent social jet lag (P < 0.05). More evening-types had higher light intensity at 2 h before sleep and lower melatonin values (01:00 h). Eveningness associated with higher BMI and metabolic risk (higher values of insulin, glucose, triglycerides and cholesterol). Evening-types presented better grades in art. In conclusion, more evening-types, as objectively assessed, presented sleep alterations, social jet lag, obesity and higher metabolic risk.

Diet, Physical Activity, and Daylight Exposure Patterns in Night-Shift Workers and Day Workers

Background

Night-shift work has been reported to have an impact on nutrition, daylight exposure, and physical activity, which might play a role in observed health effects. Because these exposures show diurnal variation, and shift work has been related with disturbances in the circadian rhythm, the timing of assessment of these factors requires careful consideration. Our aim was to describe the changes in patterns of diet, physical activity, and daylight exposure associated with night-shift work.

Methods

We conducted an observational study among female healthcare workers either regularly working night shifts or not working night shifts. We assessed physical activity and daylight exposure using continuous monitoring devices for 48 h. We logged dietary patterns (24 h) and other health- and work-associated characteristics. Two measurement sessions were conducted when participants did 'not' work night shifts, and one session was conducted during a night-shift period.

Results

Our study included 69 night-shift workers and 21 day workers. On days in which they conduct work but no night work, night-shift workers had similar physical activity and 24-h caloric intake, yet higher overall daylight exposures than day workers and were more often exposed around noon instead of mainly around 1800h. Night-shift workers were less exposed to daylight during the night-shift session compared to the non-night-shift session. Total caloric intakes did not significantly differ between sessions, but we did observe a shorter maximum fasting interval, more eating moments, and a higher percentage of fat intake during the night-shift session.

Conclusion

Observed differences in diet, physical activity, and exposure to daylight primarily manifested themselves through changes in exposure patterns, highlighting the importance of time-resolved measurements in night-shift-work research. Patterns in daylight exposure were primarily related to time of waking up and working schedule, whereas timing of dinner seemed primarily governed by social conventions.

Application of Machine Learning Methods to Ambulatory Circadian Monitoring (ACM) for Discriminating Sleep and Circadian Disorders

The present study proposes a classification model for the differential diagnosis of primary insomnia (PI) and delayed sleep phase disorder (DSPD), applying machine learning methods to circadian parameters obtained from ambulatory circadian monitoring (ACM). Nineteen healthy controls and 242 patients (PI = 184; DSPD = 58) were selected for a retrospective and non-interventional study from an anonymized Circadian Health Database (https://kronowizard.um.es/). ACM records wrist temperature (T), motor activity (A), body position (P), and environmental light exposure (L) rhythms during a whole week. Sleep was inferred from the integrated variable TAP (from temperature, activity, and position). Non-parametric analyses of TAP and estimated sleep yielded indexes of interdaily stability (IS), intradaily variability (IV), relative amplitude (RA), and a global circadian function index (CFI). Mid-sleep and mid-wake times were estimated from the central time of TAP-L5 (five consecutive hours of lowest values) and TAP-M10 (10 consecutive hours of maximum values), respectively. The most discriminative parameters, determined by ANOVA, Chi-squared, and information gain criteria analysis, were employed to build a decision tree, using machine learning. This model differentiated between healthy controls, DSPD and three insomnia subgroups (compatible with onset, maintenance and mild insomnia), with accuracy, sensitivity, and AUC >85%. In conclusion, circadian parameters can be reliably and objectively used to discriminate and characterize different sleep and circadian disorders, such as DSPD and OI, which are commonly confounded, and between different subtypes of PI. Our findings highlight the importance of considering circadian rhythm assessment in sleep medicine.

Association of rest-activity and light exposure rhythms with sleep quality in insomnia patients

The relevance of altered rest-activity rhythm (RAR) and light exposure rhythm (LER) in insomnia patients under natural conditions remains unclear. The aim of this study was to compare the parametric and nonparametric circadian variables of RAR and those of LER under natural conditions between insomnia patients and normal controls (NC) in a community-dwelling setting. The relationship of the nonparametric variables with sleep quality was also explored in both groups. Participants above 18 years old were recruited from three Public Health Centers in a rural area of Korea. Actigraphy (Actiwatch 2; Philips Respironics, Murrysville PA, USA) recording was conducted for 7 days. Subjects were eligible for our study if they had an insomnia disorder (ID) for at least 1 month. Actigraphy data of 78 normal control (NC) subjects (Age, 55.95 ± 13.22 years) and 104 patients with insomnia disorder (ID) (Age, 62.14 ± 12.34 years) were included for the analysis. Acrophases and amplitudes of RAR and LER were estimated using cosinor analysis. Interdaily stability (IS), intradaily variability (IV), and relative amplitude (RA) of these rhythms were determined using nonparametric methods. Parametric cosinor and nonparametric variables of RAR and LER were compared between the NC and ID groups. Generalized linear models (GLMs) were applied to evaluate the main effects of group and each nonparametric variable as well as a group by each variable interaction on the sleep onset latency (SOL), sleep efficiency (SE), and wake after sleep onset (WASO) reflecting sleep quality. Among sleep parameters, the ID group showed significantly lower SE and greater WASO than the NC group. There were no significant differences in the acrophase and amplitude of RAR and LER between the two groups. There were no significant differences in IV, IS, and RA of RAR and LER between the two groups either. GLMs for RAR revealed a significant interaction between the group and IS on the SOL (β = -46.39, p < 0.01), indicating a negative relationship of the IS with SOL in ID unlike its positive relationship in NC. There were no significant main effects of IV on the SOL, SE, and WASO, but significant main effects of RA on the SE and WASO (β = 63.65 and β = -221.43, respectively, p < 0.01). GLMs for LER revealed no significant main effects of IS, IV or RA on the SOL, SE, and WASO, but significant interactions between group and RA on the SE and WASO (β = 56.17 and β = -171.93, respectively, p < 0.05), indicating a stronger positive relationship of the RA with SE in ID compared to NC, and a negative relationship of the RA with WASO in ID, unlike its positive relationship in NC. Although our study did not reveal group differences in circadian variables of RAR and LER, it suggested that the regularity of RAR could be positively associated with sleep initiation, while the robustness of LER could be positively associated with sleep maintenance in insomnia patients.

Assessing Chronotypes by Ambulatory Circadian Monitoring

In order to develop objective indexes for chronotype identification by means of direct measurement of circadian rhythms, 159 undergraduate students were recruited as volunteers and instructed to wear ambulatory circadian monitoring (ACM) sensors that continuously gathered information on the individual's environmental light and temperature exposure, wrist temperature, body position, activity, and the integrated TAP (temperature, activity, and position) variable for 7 consecutive days under regular free-living conditions. Among all the proposed indexes, the night phase marker (NPM) of the TAP variable was the best suited to discriminate among chronotypes, due to its relationship with the Munich ChronoType Questionnaire (β = 0.531; p < 0.001). The NPM of TAP allowed subjects to be classified as early- (E-type, 20%), neither- (N-type, 60%), and late-types (L-type, 20%), each of which had its own characteristics. In terms of light exposure, while all subjects had short exposure times to bright light (>100 lux), with a daily average of 93.84 ± 5.72 min, the earlier chronotypes were exposed to brighter days and darker nights compared to the later chronotypes. Furthermore, the earlier chronotypes were associated with higher stability and day-night contrast, along with an earlier phase, which could be the cause or consequence of the light exposure habits. Overall, these data support the use of ACM for chronotype identification and for evaluation under free living conditions, using objective markers.

Evaluation of agomelatine for the treatment of sleep problems in adults with autism spectrum disorder and co-morbid intellectual disability

PURPOSE

Intellectual disability (ID) and autism spectrum disorder (ASD) are common, co-occurring developmental disorders and are frequently associated with sleep problems. This study aimed to assess the effectiveness and tolerability of agomelatine as a pharmacotherapy for sleep problems in ASD adults with ID.

METHOD

A randomised, crossover, triple-blind, placebo-controlled clinical trial, with two three-month periods of treatment starting with either agomelatine or placebo and a washout period of two weeks. Ambulatory circadian monitoring (24 hours/7 days) evaluated total sleep time (TST) as the primary outcome variable.

RESULTS

Participants (N=23; 35±12 years old; 83% male) had a median of three (interquartile range (IQR) 1-4) co-morbidities and were taking a median of five (IQR 2-7) prescribed drugs. Before agomelatine or placebo treatment, all subjects presented with insomnia symptoms, including sleep latency (100% abnormal, 55±23 minutes) or TST (55% abnormal, 449±177 minutes), and 66% had circadian rhythm sleep-wake abnormalities with rhythm phase advancements according to the M5 sleep phase marker values. During the three-month agomelatine treatment, night TST significantly increased by a mean of 83 minutes (16% abnormal, 532±121 minutes), together with a phase correction (M5 1:45±2:28 hours vs. 3:15±2:20 hours), improving sleep stability in wrist temperature rhythm (0.43±0.29 vs. 0.52±0.18 AU). Adverse events were mild and transient.

CONCLUSIONS

Agomelatine was effective and well tolerated for treating insomnia and circadian rhythm sleep problems present in adults with ASD and ID.

Relationship between the Daily Rhythm of Distal Skin Temperature and Brown Adipose Tissue 18F-FDG Uptake in Young Sedentary Adults

The present study examines whether the daily rhythm of distal skin temperature (DST) is associated with brown adipose tissue (BAT) metabolism as determined by ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake in young adults. Using a wireless thermometer (iButton) worn on the nondominant wrist, DST was measured in 77 subjects (26% male; age 22 ± 2 years; body mass index 25.2 ± 4.8 kg/m²) for 7 consecutive days. The temperatures to which they were habitually exposed over the day were also recorded. The interday stability of DST was calculated from the collected data, along with the intraday variability and relative amplitude; the mean temperature of the 5 and 10 consecutive hours with the maximum and minimum DST values, respectively; and when these hours occurred. Following exposure to cold, BAT volume and mean and peak standardized ¹⁸F-FDG uptake (SUV_mean and SUV_peak) were determined for each subject via static ¹⁸F-FDG positron emission tomography/computed tomography scanning. Relative amplitude and the time at which the 10 consecutive hours of minimum DST values occurred were positively associated with BAT volume, SUV_mean, and SUV_peak (p ≤ 0.02), whereas the mean DST of that period was inversely associated with the latter BAT variables (p ≤ 0.01). The interday stability and intraday variability of the DST were also associated (directly and inversely, respectively) with BAT SUV_peak (p ≤ 0.02 for both). All of these associations disappeared, however, when the analyses were adjusted for the ambient temperature to which the subjects were habitually exposed. Thus, the relationship between the daily rhythm of DST and BAT activity estimated by ¹⁸F-FDG uptake is masked by environmental and likely behavioral factors. Of note is that those participants exposed to the lowest ambient temperature showed 3 to 5 times more BAT volume and activity compared with subjects who were exposed to a warmer ambient temperature.

A systematic review of the amount and timing of light in association with objective and subjective sleep outcomes in community-dwelling adults

Light is considered the dominant environmental cue, or zeitgeber, influencing the sleep-wake cycle. Despite recognizing the importance of light for our well-being, less is known about the specific conditions under which light is optimally associated with better sleep. Therefore, a systematic review was conducted to examine the association between the amount and timing of light exposure in relation to sleep outcomes in healthy, community-dwelling adults. A systematic search was conducted of four databases from database inception to June 2016. In total, 45 studies met the review eligibility criteria with generally high study quality excepting for the specification of eligibility criteria and the justification of sample size. The majority of studies involved experimental manipulation of light (n = 32) vs observational designs (n = 13). Broad trends emerged suggesting that (1) bright light (>1000 lux) has positive implications for objectively assessed sleep outcomes compared to dim (<100 lux) and moderate light (100-1000 lux) and (2) bright light (>1000 lux) has positive implications for subjectively assessed sleep outcomes compared to moderate light (100-1000 lux). Effects due to the amount of light are moderated by the timing of light exposure such that, for objectively assessed sleep outcomes, brighter morning and evening light exposure are consistent with a shift in the timing of the sleep period to earlier and later in the day, respectively. For subjectively assessed sleep outcomes, brighter light delivered in the morning was associated with self-reported sleep improvements and brighter evening light exposure was associated with worse self-reported sleep.

Circadian monitoring as an aging predictor

The ageing process is associated with sleep and circadian rhythm (SCR) frailty, as well as greater sensitivity to chronodisruption. This is essentially due to reduced day/night contrast, decreased sensitivity to light, napping and a more sedentary lifestyle. Thus, the aim of this study is to develop an algorithm to identify a SCR phenotype as belonging to young or aged subjects. To do this, 44 young and 44 aged subjects were recruited, and their distal skin temperature (DST), activity, body position, light, environmental temperature and the integrated variable TAP rhythms were recorded under free-living conditions for five consecutive workdays. Each variable yielded an individual decision tree to differentiate between young and elderly subjects (DST, activity, position, light, environmental temperature and TAP), with agreement rates of between 76.1% (light) and 92% (TAP). These decision trees were combined into a unique decision tree that reached an agreement rate of 95.3% (4 errors out of 88, all of them around the cut-off point). Age-related SCR changes were very significant, thus allowing to discriminate accurately between young and aged people when implemented in decision trees. This is useful to identify chronodisrupted populations that could benefit from chronoenhancement strategies.

Sleep problems in adults with autism spectrum disorder and intellectual disability

Sleep problems (SP) are recognized as a common comorbid condition in autism spectrum disorder (ASD) and can influence core autism symptoms and mental and physical health. SPs can be lifelong and have been reported that adults on the autistic spectrum with and without intellectual disability (ID) present SPs (longer sleep latency, frequent night awakenings, and circadian rhythm sleep-wake disorders). A prospective, objective sleep study was conducted in 41 adults with ASD (33 ± 6 years old) and ID and 51 typically developing adults (33 ± 5 years old) using ambulatory circadian monitoring (ACM) recording wrist temperature, motor activity, body position, sleep, and light intensity. The findings indicated that individuals with ASD presented sleep difficulties including low sleep efficiency, prolonged sleep latency and increased number and length of night awakenings, together with daily sedentary behavior, and increased nocturnal activity. Furthermore, indications of an advanced sleep-wake phase disorder were found in these autistic adults. Examining sleep and markers of the circadian system showed significant differences between adults with ASD and ID and an age-matched, healthy adult population. The sleep disturbances described for this sample of adults with ASD and ID are similar to those of already described for adults with ASD without ID; their relationship with intellectual ability should be further studied. Improving knowledge of sleep patterns in ASD adults with ID might help to designed targeted interventions to improve their functioning and reduce family stress. Autism Research 2019, 12: 66-79. © 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: SPs are very frequent in autism from childhood to adulthood. We recorded sleep with a watch-like device in adults with autism and ID and compared sleep patterns with nonautistic volunteers. Results showed poorer sleep conditions in adults with autism (increased sleep latency and number/length of night awakenings) that resulted in decreased sleep efficiency. Increasing knowledge of the SPs in adults on the autism spectrum will allow to improve their and their families' quality of life.

Impact of a shift work-like lighting schedule on the functioning of the circadian system in the short-lived fish Nothobranchius furzeri

Adult Nothobranchius furzeri of the MZM-04/10 strain were individually kept and subjected to a "5 + 2" shifting lighting schedule (SHIFT) for 8 weeks in order to evaluate the desynchronizing effects of a simulated human-like shift-work schedule on the functioning of the circadian system (CS). With this aim, sixteen 21-week-old N. furzeri were placed into a Morning, Night and Evening schedule (lights on from 08:00 to 16:00, 00:00 to 08:00 and 16:00 to 00:00 h, respectively) and fed once a day in the middle of the corresponding photophase (12:00, 04:00 and 20:00 h, respectively). Then, in the weekends (2 days), fish were always returned to the Morning shift. As controls, 16 fish were maintained under a non-shifting LD cycle condition (CONTROL) throughout the whole experiment, with lights on from 08:00 to 16:00 h. Rest-activity rhythm (RAR) of fish subjected to SHIFT showed several symptoms of chronodisruption, such as a decrease in the percentage of diurnal activity and a reduction of the relative amplitude and the circadian function index with time. When a periodogram analysis was performed, RAR of N. furzeri under SHIFT conditions showed up to three separate circadian components: one longer than 24 h (26.5 h) that followed the weekly 8 h delays; a short-period component (~23 h) that was related to the weekend's phase advances, and finally, a 24 h component. The shifting LD schedule also affected fish CS at a molecular level, with several significant differences in the expression of core genes of the molecular clock (bmal1, clock, rorα, rev-erbα) between SHIFT and CONTROL animals. RAR impairment along with changes in clock gene expression could be associated with high stress and accelerated aging in these fish.

Caffeinated Drinks Intake, Late Chronotype, and Increased Body Mass Index among Medical Students in Chongqing, China: A Multiple Mediation Model

Background: This paper investigates the problems regarding caffeinated drinks intake, late chronotype, and increased body mass index (BMI) among medical students at a Chinese university. Methods: This cross-sectional study was conducted in 2018 with 616 medical students from Chongqing Medical University in Chongqing, China, whose information were collected by a self-reported questionnaire that included four sections: Demographic characteristics; Caffeinated drinks intake and physical state; Morningness-Eveningness Questionnaire; Depression Anxiety Stress Scale 21. Multiple mediation analyses were conducted to test the impact of late chronotype on increased BMI through caffeinated drinks consumption through two models. Results: The significantly mediated effect of caffeinated drinks consumption was revealed (estimate: -0.01, SE = 0.01, 95% CI [-0.02, -0.01]), and which played a positive role in linking late chronotype (B = -0.01, SE = 0.01, p < 0.001) and increased BMI (B = 1.37, SE = 0.21, p < 0.01), but their significant association did not be found in reversed model. In addition, physical activity and inactivity times demonstrated significant indirect effects in the two models. Conclusions: Interventions should focus on reducing caffeinated drinks intake and sedentary behavior time, enhancing physical activity among medical students.

Circadian health differs between boys and girls as assessed by non-invasive tools in school-aged children

BACKGROUND & AIMS

Assessment of circadian health is confined to adults. However, understanding circadian status of school-aged children is necessary due to its health implications. The aim was to develop 1) a protocol to assess circadian function in school-aged children by combining the best non-invasive tools previously validated in adults; 2) a score to capture circadian function in children including food timing. This protocol will allow to explore gender differences and to compare the circadian function of school-aged children with adults from the same Mediterranean area.

METHODS

Healthy children (8-12 y) from 3 schools in a Mediterranean area of Spain were recruited (n = 248; 125 males and 123 females). Several non-invasive tools were used: a) 7-day-diaries of food timing and food intake, physical-activity and sleep, b) Munich-chronotype-self-reported-questionnaire; c) cortisol and melatonin saliva determinations; d) 7-day-rhythms of wrist temperature (T), activity (A), position (P) and the integrative variable TAP e) 7-day-light exposure.

RESULTS

We have constructed the first school-aged children population for the assessment of circadian function (ONTIME-Jr) and a new circadian score has been developed. Among circadian-related measures, TAP was the most suitable and reliable to determine circadian system characteristics. Circadian function was better in girls than in boys [circadian score (AU) Mean ± SD (girls, 1216 ± 153 vs. 1159 ± 173 boys, P = 0.012)], and also in school-aged children than in adults from the same Mediterranean area (Circadian-Function-Index: children 0.47 ± 0.06 vs. adults 0.45 ± 0.06 P = 0.001).

CONCLUSIONS

A new protocol, including TAP and food timing, demonstrated to be reliable in assessing circadian function in children. These non-invasive techniques provide the wherewithal for paediatricians to assess circadian function in clinical practice.

TRIAL REGISTRATION

Chronobiology and childhood obesity (ONTIME-Jr: Obesity, Nutrigenetics, Timing and Mediterranean, Junior). ClinicalTrials.gov ID: NCT02895282, October 2014.

Circadian Impairment of Distal Skin Temperature Rhythm in Patients With Sleep-Disordered Breathing: The Effect of CPAP

Study objectives

Our aim was to evaluate the circadian rhythm of distal skin temperature (DST) in sleep-disordered breathing (SDB), its relation to excessive daytime sleepiness and the effect of continuous positive airway pressure (CPAP) on DST.

Methods

Eighty SDB patients (53.1 ± 1.2 years old, 27.6% women) and 67 healthy participants (52.3 ± 1.6 years old, 26.9% women) wore a temperature data logger for 1 week. On the last day of that week, SDB patients underwent a polysomnography followed by a Maintenance of Wakefulness Test (MWT), Multiple Sleep Latency Test, and Sustained Attention to Response Task protocol to objectively quantify daytime sleepiness. A subset of 21 moderate to severe SDB patients were treated with CPAP during at least 3 months and revaluated with the same procedure. A nonparametric analysis was performed to characterize DST to assess differences between groups and associations among DST, polysomnography, and daytime sleepiness measures.

Results

SDB patients showed an unstable, fragmented, flattened, phase-advanced, and less robust DST rhythm as compared to healthy participants. The more severe the SDB, the worse the DST pattern was, as indicated by the correlation coefficient. Sleepiness, according to MWT sleep latencies, was also associated with the higher fragmentation, lower amplitude, and less robustness of the DST rhythm. Treatment with CPAP improved DST pattern regularity and robustness.

Conclusion

DST is altered in SDB, exhibiting a direct relationship to the severity of this condition, and improves with CPAP treatment. DST independently correlates with sleepiness, thus, its measurement may contribute to the understanding of the pathophysiology of sleepiness in these patients.

Circadian Rhythmic Characteristics in Men With Substance Use Disorder Under Treatment. Influence of Age of Onset of Substance Use and Duration of Abstinence

There is evidence of the reciprocal influence between the alteration of circadian rhythms and Substance Use Disorders (SUD), and part of the success of the SUD treatment lays in the patient's rhythmic recovery. We aim to elucidate the effect of the SUD treatment in circadian rhythmicity considering, for the first time, the age of onset of substance use (OSU) and duration of abstinence. We registered the sleep-wake schedules, the chronotype and the distal skin temperature of 114 SUD patients with at least 3 months of abstinence, considering whether they had begun consumption at age 16 or earlier (OSU ≤ 16, n = 56) or at 17 or later (OSU ≥ 17, n = 58), and duration of abstinence as short (SA: 3 to 5 months, n = 38), medium (MA: 6 to 9 months, n = 35) or long (LA: more than 9 months, n = 41). Moreover, we compared the patients' distal skin temperature pattern with a similar sample of healthy controls (HC, n = 103). SUD patients showed a morningness tendency and higher night values, amplitude and stability, a better adjustment to the cosine model and lower minimum temperature and circadianity index in the distal skin temperature rhythm, in contrast to the HC group. The OSU ≥ 17 and LA groups showed a more robust distal skin temperature pattern, as well as milder clinical characteristics when compared to the OSU ≤ 16 and SA groups, respectively. The circadian disturbances associated to substance consumption seem to improve with treatment, although the age of OSU and the duration of abstinence are modulating variables. Our results highlight the need to include chronobiological strategies that boost circadian rhythmicity both in SUD prevention and rehabilitation programs. The measurement of distal skin temperature rhythm, a simple and reliable procedure, could be considered an indicator of response to treatment in SUD patients.

Light color importance for circadian entrainment in a diurnal (Octodon degus) and a nocturnal (Rattus norvegicus) rodent

The central circadian pacemaker (Suprachiasmatic Nuclei, SCN) maintains the phase relationship with the external world thanks to the light/dark cycle. Light intensity, spectra, and timing are important for SCN synchronisation. Exposure to blue-light at night leads to circadian misalignment that could be avoided by using less circadian-disruptive wavelengths. This study tests the capacity of a diurnal Octodon degus and nocturnal Rattus norvegicus to synchronise to different nocturnal lights. Animals were subjected to combined red-green-blue lights (RGB) during the day and to: darkness; red light (R); combined red-green LED (RG) lights; and combined red-green-violet LED (RGV) lights during the night. Activity rhythms free-ran in rats under a RGB:RG cycle and became arrhythmic under RGB:RGV. Degus remained synchronised, despite the fact that day and night-time lighting systems differed only in spectra, but not in intensity. For degus SCN c-Fos activation by light was stronger with RGB-light than with RGV. This could be relevant for developing lighting that reduces the disruptive effects of nocturnal light in humans, without compromising chromaticity.

The clock is ticking. Ageing of the circadian system: From physiology to cell cycle

The circadian system is the responsible to organise the internal temporal order in relation to the environment of every process of the organisms producing the circadian rhythms. These rhythms have a fixed phase relationship among them and with the environment in order to optimise the available energy and resources. From a cellular level, circadian rhythms are controlled by genetic positive and negative auto-regulated transcriptional and translational feedback loops, which generate 24h rhythms in mRNA and protein levels of the clock components. It has been described about 10% of the genome is controlled by clock genes, with special relevance, due to its implications, to the cell cycle. Ageing is a deleterious process which affects all the organisms' structures including circadian system. The circadian system's ageing may produce a disorganisation among the circadian rhythms, arrhythmicity and, even, disconnection from the environment, resulting in a detrimental situation to the organism. In addition, some environmental conditions can produce circadian disruption, also called chronodisruption, which may produce many pathologies including accelerated ageing. Finally, some strategies to prevent, palliate or counteract chronodisruption effects have been proposed to enhance the circadian system, also called chronoenhancement. This review tries to gather recent advances in the chronobiology of the ageing process, including cell cycle, neurogenesis process and physiology.

Late dinner impairs glucose tolerance in MTNR1B risk allele carriers: A randomized, cross-over study

BACKGROUND & AIMS

Late-night dinner eating is associated with increased risk for type-2 diabetes. The underlying mechanism is unclear. One explanatory hypothesis is that the concurrence of elevated circulating melatonin and high glucose concentrations (characterizing late eating) leads to impaired glucose tolerance. However, to date no study has tested the influence of physiological melatonin concentrations on glucose-tolerance. The discovery of melatonin receptor MTNR1B as a diabetes risk gene provides evidence for a role of physiological levels of melatonin in glucose control. The aim of our study was to test the hypothesis that elevated endogenous melatonin concentrations worsen glucose control when eating late. Registered under ClinicalTrials.gov Identifier no. NCT03003936.

METHODS

We performed a randomized, cross-over trial to compare glucose tolerance in the presence (late dinner) or absence (early dinner) of elevated physiological melatonin concentrations and we compared the results between homozygous carriers and non-carriers of the MTNR1B risk allele.

RESULTS

The concurrence of meal timing with elevated endogenous melatonin concentrations resulted in impaired glucose tolerance. This effect was stronger in MTNR1B risk-carriers than in non-carriers. Furthermore, eating late significantly impaired glucose tolerance only in risk-carriers and not in the non-risk carriers.

CONCLUSIONS

The interaction of dinner timing with MTNR1B supports a causal role of endogenous melatonin in the impairment of glucose tolerance. These results suggest that moving the dinner to an earlier time may result in better glucose tolerance specially in MTNR1B carriers.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT03003936.

Functional Somatic Syndromes: Skin Temperatures and Activity Measurements Under Ambulatory Conditions

Functional somatic syndromes are mostly associated with pain and emotional distress. As one marker for the autonomic stress response, the distal skin temperature decreases during psychological stress. In patients with functional somatic syndromes, the distal skin temperature under baseline conditions (without stress induction) is usually lower than in healthy subjects, which could be due to the sustained presence of pain-related stress in such patients. The aim of our study was to investigate whether patients with functional somatic syndromes show altered skin temperatures also under everyday life conditions. 14 patients with functional somatic syndromes and 14 matched healthy control subjects were investigated under ambulatory conditions over six consecutive days. During this time, distal and proximal skin temperatures were continuously recorded and sleep-wake cycles were monitored by actimetry and sleep-wake diaries. Unexpectedly, the patients showed higher distal skin temperatures than control subjects in the afternoon. The objective temperature data did not match the patients' subjective experience: ratings of thermal comfort did not vary between the two groups. Moreover, similar levels of daytime activity were recorded in the two samples, even though patients reported more tiredness and more body tension than controls. We interpret the observed dissociation between objective skin temperature measurements and subjective ratings of the bodily thermal comfort as support for the notion of an alexisomia account (reduced bodily awareness) for functional somatic syndromes. Moreover, findings indicate that subjective complaints of tiredness and tension do not necessarily result in physical avoidance behaviour.

Relevance of internal time and circadian robustness for cancer patients

BACKGROUND

Adequate circadian timing of cancer treatment schedules (chronotherapy) can enhance tolerance and efficacy several-fold in experimental and clinical situations. However, the optimal timing varies according to sex, genetic background and lifestyle. Here, we compute the individual phase of the Circadian Timing System to decipher the internal timing of each patient and find the optimal treatment timing.

METHODS

Twenty-four patients (11 male; 13 female), aged 36 to 77 years, with advanced or metastatic gastro-intestinal cancer were recruited. Inner wrist surface Temperature, arm Activity and Position (TAP) were recorded every 10 min for 12 days, divided into three 4-day spans before, during and after a course of a set chronotherapy schedule. Pertinent indexes, I < O and a new biomarker, DI (degree of temporal internal order maintenance), were computed for each patient and period.

RESULTS

Three circadian rhythms and the TAP rhythm grew less stable and more fragmented in response to treatment. Furthermore, large inter- and intra-individual changes were found for T, A, P and TAP patterns, with phase differences of up to 12 hours among patients. A moderate perturbation of temporal internal order was observed, but the administration of fixed chronomodulated chemotherapy partially resynchronized temperature and activity rhythms by the end of the study.

CONCLUSIONS

The integrated variable TAP, together with the asynchrony among rhythms revealed by the new biomarker DI, would help in the personalization of cancer chronotherapy, taking into account individual circadian phase markers.

Natural light exposure, sleep and depression among day workers and shiftworkers at arctic and equatorial latitudes

OBJECTIVES

This study aimed to investigate the relationship between individual natural light exposure, sleep need, and depression at two latitudes, one extreme with a few hours of light per day during winter, and the other with equal hours of light and darkness throughout the year.

METHODS

This cross-sectional study included a sample of Brazilian workers (Equatorial, n = 488 workers) and a Swedish sample (Arctic, n = 1,273).

RESULTS

The reported mean total natural light exposure per 4-week cycle differed significantly between the Equatorial and Arctic regions. However, shiftworkers from both sites reported similar hours of natural light exposure. Short light exposure was a predictor for insufficient sleep.

CONCLUSION

Reduced exposure to natural light appears to increase the perception of obtaining insufficient sleep. Arctic workers were more prone to develop depression than Equatorial workers.

Natural light exposure, sleep and depression among day workers and shiftworkers at arctic and equatorial latitudes

OBJECTIVES

This study aimed to investigate the relationship between individual natural light exposure, sleep need, and depression at two latitudes, one extreme with a few hours of light per day during winter, and the other with equal hours of light and darkness throughout the year.

METHODS

This cross-sectional study included a sample of Brazilian workers (Equatorial, n = 488 workers) and a Swedish sample (Arctic, n = 1,273).

RESULTS

The reported mean total natural light exposure per 4-week cycle differed significantly between the Equatorial and Arctic regions. However, shiftworkers from both sites reported similar hours of natural light exposure. Short light exposure was a predictor for insufficient sleep.

CONCLUSION

Reduced exposure to natural light appears to increase the perception of obtaining insufficient sleep. Arctic workers were more prone to develop depression than Equatorial workers.

Protecting the melatonin rhythm through circadian healthy light exposure

Currently, in developed countries, nights are excessively illuminated (light at night), whereas daytime is mainly spent indoors, and thus people are exposed to much lower light intensities than under natural conditions. In spite of the positive impact of artificial light, we pay a price for the easy access to light during the night: disorganization of our circadian system or chronodisruption (CD), including perturbations in melatonin rhythm. Epidemiological studies show that CD is associated with an increased incidence of diabetes, obesity, heart disease, cognitive and affective impairment, premature aging and some types of cancer. Knowledge of retinal photoreceptors and the discovery of melanopsin in some ganglion cells demonstrate that light intensity, timing and spectrum must be considered to keep the biological clock properly entrained. Importantly, not all wavelengths of light are equally chronodisrupting. Blue light, which is particularly beneficial during the daytime, seems to be more disruptive at night, and induces the strongest melatonin inhibition. Nocturnal blue light exposure is currently increasing, due to the proliferation of energy-efficient lighting (LEDs) and electronic devices. Thus, the development of lighting systems that preserve the melatonin rhythm could reduce the health risks induced by chronodisruption. This review addresses the state of the art regarding the crosstalk between light and the circadian system.

The midpoint of sleep on working days: a measure for chronodisruption and its association to individuals' well-being

There is consistent evidence suggesting a relationship between individuals' sleep-wake rhythms and well-being. The indiscriminate demands from daily working routines, which do not respect this individual physiological rhythm, might be mediating this phenomenon. The aim of the present study was to evaluate the relationship between the characteristics of sleep routines during working days and psychological well-being. This was a cross-sectional study on 825 individuals from rural communities from southern Brazil. The study protocol included a questionnaire on demographic characteristics, working routines, health complaints, and habits; the Munich Chronotype Questionnaire for sleep-wake rhythm and; the WHO-Five well-being index. Since sex has been shown to affect sleep circadian rhythm and well-being, analysis was performed on men and women separately. In the proposed hierarchical regression models, different factors contributed to well-being according to sex. Among men, sleep-wake and work-related variables did not predict well-being scores. Among women, later midpoints of sleep on working days (B = -1.243, SE B = 0.315, β = -0.220), working more days per week (B = -1.507, SE B = 0.494, β = 0.150), having longer working journeys (B = -0.293, SE B = 0.105, β = -0.166), earlier working journey midpoints (B = 0.465, SE B = 0.222, β = 0.115), and being exposed to less sunlight (B = 0.140, SE B = 0.064, β = 0.103) predicted worse well-being. For the subgroup of women with days free from work, we have found a correlation between later midpoints of sleep during the week with worse well-being (Pearson's r = -0.159, p = 0.045) while the same relationship was not significantly observed with the midpoint of sleep on non-working days (Pearson's r = -0.153, p = 0.054). Considering WHO-Five as categorical, based on proposed clinical cut-offs, among women working 7-d/week, those with worst well-being (WHO-Five < 13) had the latest midpoint of sleep (F = 4.514, p = 0.012). Thus, the midpoint of sleep on working days represents the interaction between individuals' sleep-wake behavior and working routines. It plays an important role as a stress factor and may be a useful alternative variable related to chronodisruption.

The characterization of biological rhythms in mild cognitive impairment

Introduction. Patients with dementia, especially Alzheimer's disease, present several circadian impairments related to an accelerated perturbation of their biological clock that is caused by the illness itself and not merely age-related. Thus, the objective of this work was to elucidate whether these circadian system alterations were already present in patients with mild cognitive impairment (MCI), as compared to healthy age-matched subjects. Methods. 40 subjects (21 patients diagnosed with MCI, 74.1 ± 1.5 y.o., and 19 healthy subjects, 71.7 ± 1.4 y.o.) were subjected to ambulatory monitoring, recording wrist skin temperature, motor activity, body position, and the integrated variable TAP (including temperature, activity, and position) for one week. Nonparametrical analyses were then applied. Results. MCI patients exhibited a significant phase advance with respect to the healthy group for the following phase markers: temperature M5 (mean ± SEM: 04:20 ± 00:21 versus 02:52 ± 00:21) and L10 (14:35 ± 00:27 versus 13:24 ± 00:16) and TAP L5 (04:18 ± 00:14 versus 02:55 ± 00:30) and M10 (14:30 ± 00:18 versus 13:28 ± 00:23). Conclusions. These results suggest that significant advances in the biological clock begin to occur in MCI patients, evidenced by an accelerated aging of the circadian clock, as compared to a healthy population of the same age.

The circadian timing system in clinical oncology

The circadian timing system (CTS) controls several critical molecular pathways for cancer processes and treatment effects over the 24 hours, including drug metabolism, cell cycle, apoptosis, and DNA damage repair mechanisms. This results in the circadian time dependency of whole-body and cellular pharmacokinetics and pharmacodynamics of anticancer agents. However, CTS robustness and phase varies among cancer patients, based on circadian monitoring of rest- activity, body temperature, sleep, and/or hormonal secretion rhythms. Circadian disruption has been further found in up to 50% of patients with metastatic cancer. Such disruption was associated with poor outcomes, including fatigue, anorexia, sleep disorders, and short progression-free and overall survival. Novel, minimally invasive devices have enabled continuous CTS assessment in non-hospitalized cancer patients. They revealed up to 12-hour differences in individual circadian phase. Taken together, the data support the personalization of chronotherapy. This treatment method aims at the adjustment of cancer treatment delivery according to circadian rhythms, using programmable-in-time pumps or novel release formulations, in order to increase both efficacy and tolerability. A fixed oxaliplatin, 5-fluorouracil and leucovorin chronotherapy protocol prolonged median overall survival in men with metastatic colorectal cancer by 3.3 months as compared to conventional delivery, according to a meta-analysis (P=0.009). Further analyses revealed the need for the prevention of circadian disruption or the restoration of robust circadian function in patients on chronotherapy, in order to further optimize treatment effects. The strengthening of external synchronizers could meet such a goal, through programmed exercise, meal timing, light exposure, improved social support, sleep scheduling, and the properly timed administration of drugs that target circadian clocks. Chrono-rehabilitation warrants clinical testing for improving quality of life and survival in cancer patients.

Toward a chronobiological characterization of obesity and metabolic syndrome in clinical practice

BACKGROUND & AIMS

To test several circadian rhythm variables in a female population to identify the best tool to assess chronodisruption in obesity and metabolic syndrome (MetS) to define a score to be used for chronodisruption characterization in clinical practice.

METHODS

Anthropometric measurements and markers of circadian rhythms, such as sleep and feeding diary, Horne-Ostberg questionnaire, melatonin and cortisol measurements, and wrist temperature measurements, were determined. MetS variables were also analyzed. Study was conducted in 70 women. Data were subjected to factor analysis. Receiver operating characteristic curves were used as predictors of chronodisruption risk, and a score was calculated to classify the subjects of risk.

RESULTS

Factor analysis showed that the first-factor grouped variables were related to the skin temperature measurement. Second factor consisted of variables related to salivary cortisol levels and obesity-related measurements. Third factor included variables related to sleep-wake cycle. Fourth factor referred to peripheral temperature variables and included the classification of subjects according to the Horne-Ostberg questionnaire. To obtain a final punctuation we performed the weighted mean of the first four factors. The final range was from 27 to 57, mean value of 42. Punctuation was defined as the "chronodisruption score." Women displaying higher chronodisruption scores had higher MetS risk.

CONCLUSION

The study demonstrates that wrist temperature recordings, together with two questions of sleep onset and offset, and one morning salivary cortisol determination could be enough to characterize the chronobiology of obesity and MetS, a new chronodisruption score was developed.

Day-night contrast as source of health for the human circadian system

Modern societies are characterized by a 24/7 lifestyle (LS) with no environmental differences between day and night, resulting in weak zeitgebers (weak day light, absence of darkness during night, constant environmental temperature, sedentary LS and frequent snacking), and as a consequence, in an impaired circadian system (CS) through a process known as chronodisruption. Both weak zeitgebers and CS impairment are related to human pathologies (certain cancers, metabolic syndrome and affective and cognitive disorders), but little is known about how to chronoenhance the CS. The aim of this work is to propose practical strategies for chronoenhancement, based on accentuating the day/night contrast. For this, 131 young subjects were recruited, and their wrist temperature (WT), activity, body position, light exposure, environmental temperature and sleep were recorded under free-living conditions for 1 week. Subjects with high contrast (HC) and low contrast (LC) for each variable were selected to analyze the HC effect in activity, body position, environmental temperature, light exposure and sleep would have on WT. We found that HC showed better rhythms than LC for every variable except sleep. Subjects with HC and LC for WT also demonstrated differences in LS, where HC subjects had a slightly advanced night phase onset and a general increase in day/night contrast. In addition, theoretical high day/night contrast calculated using mathematical models suggests an improvement by means of LS contrast. Finally, some individuals classified as belonging to the HC group in terms of WT when they are exposed to the LS characteristic of the LC group, while others exhibit WT arrhythmicity despite their good LS habits, revealing two different WT components: an exogenous component modified by LS and another endogenous component that is refractory to it. Therefore, intensifying day/night contrast in subject's LS has proven to be a feasible measure to chronoenhance the CS.

Evening physical activity alters wrist temperature circadian rhythmicity

The adequate time to perform physical activity (PA) to maintain optimal circadian system health has not been defined. We studied the influence of morning and evening PA on circadian rhythmicity in 16 women with wrist temperature (WT). Participants performed controlled PA (45 min continuous-running) during 7 days in the morning (MPA) and evening (EPA) and results were compared with a no-exercise-week (C). EPA was characterized by a lower amplitude (evening: 0.028 ± 0.01 °C versus control: 0.038 ± 0.016 °C; p < 0.05) less pronounced second-harmonic (power) (evening: 0.41 ± 0.47 versus morning: 1.04 ± 0.59); and achrophase delay (evening: 06:35 ± 02:14 h versus morning: 04:51 ± 01:11 h; p < 0.05) as compared to MPA and C. Performing PA in the late evening might not be as beneficial as in the morning.

Circadian phase assessment by ambulatory monitoring in humans: correlation with dim light melatonin onset

The increased prevalence of circadian disruptions due to abnormal coupling between internal and external time makes the detection of circadian phase in humans by ambulatory recordings a compelling need. Here, we propose an accurate practical procedure to estimate circadian phase with the least possible burden for the subject, that is, without the restraints of a constant routine protocol or laboratory techniques such as melatonin quantification, both of which are standard procedures. In this validation study, subjects (N = 13) wore ambulatory monitoring devices, kept daily sleep diaries and went about their daily routine for 10 days. The devices measured skin temperature at wrist level (WT), motor activity and body position on the arm, and light exposure by means of a sensor placed on the chest. Dim light melatonin onset (DLMO) was used to compare and evaluate the accuracy of the ambulatory variables in assessing circadian phase. An evening increase in WT: WTOnset (WTOn) and "WT increase onset" (WTiO) was found to anticipate the evening increase in melatonin, while decreases in motor activity (Activity Offset or AcOff), body position (Position Offset (POff)), integrative TAP (a combination of WT, activity and body position) (TAPOffset or TAPOff) and an increase in declared sleep propensity were phase delayed with respect to DLMO. The phase markers obtained from subjective sleep (R = 0.811), WT (R = 0.756) and the composite variable TAP (R = 0.720) were highly and significantly correlated with DLMO. The findings strongly support a new method to calculate circadian phase based on WT (WTiO) that accurately predicts and shows a temporal association with DLMO. WTiO is especially recommended due to its simplicity and applicability to clinical use under conditions where knowing endogenous circadian phase is important, such as in cancer chronotherapy and light therapy.

Diurnal and menstrual cycles in body temperature are regulated differently: a 28-day ambulatory study in healthy women with thermal discomfort of cold extremities and controls

Diurnal cycle variations in body-heat loss and heat production, and their resulting core body temperature (CBT), are relatively well investigated; however, little is known about their variations across the menstrual cycle under ambulatory conditions. The main purpose of this study was to determine whether menstrual cycle variations in distal and proximal skin temperatures exhibit similar patterns to those of diurnal variations, with lower internal heat conductance when CBT is high, i.e. during the luteal phase. Furthermore, we tested these relationships in two groups of women, with and without thermal discomfort of cold extremities (TDCE). In total, 19 healthy eumenorrheic women with regular menstrual cycles (28-32 days), 9 with habitual TDCE (ages 29 ± 1.5 year; BMI 20.1 ± 0.4) and 10 controls without these symptoms (CON: aged 27 ± 0.8 year; BMI 22.7 ± 0.6; p < 0.004 different to TDCE) took part in the study. Twenty-eight days continuous ambulatory skin temperature measurements of distal (mean of hands and feet) and proximal (mean of sternum and infraclavicular regions) skin regions, thighs, and calves were carried out under real-life, ambulatory conditions (i-Buttons® skin probes, sampling rate: 2.5 min). The distal minus proximal skin temperature gradient (DPG) provided a valuable measure for heat redistribution from the core to the shell, and, hence, for internal heat conduction. Additionally, basal body temperature was measured sublingually directly after waking up in bed. Mean diurnal amplitudes in skin temperatures increased from proximal to distal skin regions and the 24-h mean values were inversely related. TDCE compared to CON showed significantly lower hand skin temperatures and DPG during daytime. However, menstrual cycle phase did not modify these diurnal patterns, indicating that menstrual and diurnal cycle variations in skin temperatures reveal additive effects. Most striking was the finding that all measured skin temperatures, together with basal body temperature, revealed a similar menstrual cycle variation (independent of BMI), with highest and lowest values during the luteal and follicular phases, respectively. These findings lead to the conclusion that in contrast to diurnal cycle, variations in CBT variation across the menstrual cycle cannot be explained by changes in internal heat conduction under ambulatory conditions. Although no measurements of metabolic heat production were carried out increased metabolic heat generation during the luteal phase seems to be the most plausible explanation for similar body temperature increases.

Uncovering different masking factors on wrist skin temperature rhythm in free-living subjects

Most circadian rhythms are controlled by a major pacemaker located in the hypothalamic suprachiasmatic nucleus. Some of these rhythms, called marker rhythms, serve to characterize the timing of the internal temporal order. However, these variables are susceptible to masking effects as the result of activity, body position, light exposure, environmental temperature and sleep. Recently, wrist skin temperature (WT) has been proposed as a new index for evaluating circadian system status. In light of previous evidence suggesting the important relationship between WT and core body temperature regulation, the aim of this work was to purify the WT pattern in order to obtain its endogenous rhythm with the application of multiple demasking procedures. To this end, 103 subjects (18–24 years old) were recruited and their WT, activity, body position, light exposure, environmental temperature and sleep were recorded under free-living conditions for 1 week. WT demasking by categories or intercepts was applied to simulate a “constant routine” protocol (awakening, dim light, recumbent position, low activity and warm environmental temperature). Although the overall circadian pattern of WT was similar regardless of the masking effects, its amplitude was the rhythmic parameter most affected by environmental conditions. The acrophase and mesor were determined to be the most robust parameters for characterizing this rhythm. In addition, a circadian modulation of the masking effect was found for each masking variable. WT rhythm exhibits a strong endogenous component, despite the existence of multiple external influences. This was evidenced by simultaneously eliminating the influence of activity, body position, light exposure, environmental temperature and sleep. We therefore propose that it could be considered a valuable and minimally-invasive means of recording circadian physiology in ambulatory conditions.

A new chronobiological approach to discriminate between acute and chronic depression using peripheral temperature, rest-activity, and light exposure parameters

BACKGROUND

Circadian theories for major depressive disorder have suggested that the rhythm of the circadian pacemaker is misaligned. Stable phase relationships between internal rhythms, such as temperature and rest/activity, and the external day-night cycle, are considered to be crucial for adapting to life in the external environmental. Therefore, the relationship and possible alterations among (i) light exposure, (ii) activity rhythm, and (iii) temperature rhythm could be important factors in clinical depression. This study aimed to investigate the rhythmic alterations in depression and evaluate the ability of chronobiological parameters to discriminate between healthy subjects and depressed patients.

METHODS

Thirty female subjects, including healthy subjects, depressed patients in the first episode, and major recurrent depression patients. Symptoms were assessed using Hamilton Depression Scale, Beck Depression Inventory and Montgomery-Äsberg Scale. Motor activity, temperature, and light values were determined for 7 days by actigraph, and circadian rhythms were calculated.

RESULTS

Depressed groups showed a lower amplitude in the circadian rhythm of activity and light exposure, but a higher amplitude in the rhythm of peripheral temperature. The correlation between temperature and activity values was different in the day and night among the control and depressed groups. For the same level of activity, depressed patients had lowest temperature values during the day. The amplitudes of temperature and activity were the highest discriminant parameters.

CONCLUSIONS

These results indicate that the study of rhythms is useful for diagnosis and therapy for depressive mood disorders.

Dipper and non-dipper blood pressure 24-hour patterns: circadian rhythm-dependent physiologic and pathophysiologic mechanisms

Neuroendocrine mechanisms are major determinants of the normal 24-h blood pressure (BP) pattern. At the central level, integration of the major driving factors of this temporal variability is mediated by circadian rhythms of monoaminergic systems in conjunction with those of the hypothalamic-pituitary-adrenal, hypothalamic-pituitary-thyroid, opioid, renin-angiotensin-aldosterone, plus endothelial systems and specific vasoactive peptides. Humoral secretions are typically episodic, coupled either to sleep and/or the circadian endogenous (suprachiasmatic nucleus) central pacemaker clock, but exhibiting also weekly, monthly, seasonal, and annual periodicities. Sleep induction and arousal are influenced also by many hormones and chemical substances that exhibit 24-h variation, e.g., arginine vasopressin, vasoactive intestinal peptide, melatonin, somatotropin, insulin, steroids, serotonin, corticotropin-releasing factor, adrenocorticotropic hormone, thyrotropin-releasing hormone, endogenous opioids, and prostaglandin E2, all with established effects on the cardiovascular system. As a consequence, physical, mental, and pathologic stimuli that activate or inhibit neuroendocrine effectors of biological rhythmicity may also interfere with, or modify, the temporal BP structure. Moreover, immediate adjustment to exogenous components/environment demands by BP rhythms is modulated by the circadian-time-dependent responsiveness of biological oscillators and their neuroendocrine effectors. This knowledge contributes to a better understanding of the pathophysiology of abnormalities of the 24-h BP pattern and level and their correction through circadian rhythm-based chronotherapeutic strategies.

Relationship of chronotype to sleep, light exposure, and work-related fatigue in student workers

Students who work during the school year face the potential of sleep deprivation and its effects, since they have to juggle between school and work responsibilities along with social life. This may leave them with less time left for sleep than their nonworking counterparts. Chronotype is a factor that may exert an influence on the sleep of student workers. Also, light and social zeitgebers may have an impact on the sleep-related problems of this population. This study aimed to document sleep, light exposure patterns, social rhythms, and work-related fatigue of student workers aged 19-21 yrs and explore possible associations with chronotype. A total of 88 student workers (mean ± SD: 20.18 ± .44 yrs of age; 36 males/52 females) wore an actigraph (Actiwatch-L; Mini-Mitter/Respironics,Bend, OR) and filled out the Social Rhythm Metric for two consecutive weeks during the school year. Also, they completed the Morningness-Eveningness Questionnaire (MEQ), Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), and Occupational Fatigue Exhaustion/Recovery Scale (OFER). Repeated and one-way analyses of variance (ANOVAs), Pearson's chi-square tests, and correlation coefficients were used for statistical comparisons. Subjects slept an average of 06:28 h/night. Actigraphic sleep parameters, such as sleep duration, sleep efficiency, wake after sleep onset, and sleep latency, did not differ between chronotypes. Results also show that evening types (n = 17) presented lower subjective sleep quality than intermediate types (n = 58) and morning types (n = 13). Moreover, evening types reported higher levels of chronic work-related fatigue, exhibited less regular social rhythms, and were exposed to lower levels of light during their waking hours (between 2 and 11 h after wake time) as compared to intermediate types and morning types. In addition, exposure to light intensities between 100 and 500 lux was lower in evening types than in intermediate types and morning types. However, bright light exposure (≥ 1000 lux) did not differ between chronotypes. In conclusion, results suggest that student workers may constitute a high-risk population for sleep deprivation. Evening types seemed to cope less well with sleep deprivation, reporting poorer sleep quality and higher levels of work-related fatigue than intermediate types and morning types. The higher chronic work-related fatigue of evening types may be linked to their attenuated level of light exposure and weaker social zeitgebers. These results add credence to the hypothesis that eveningness entails a higher risk of health-impairing behaviors.