Rhythm Variables Research Articles

Competence to thrive: resilience as an indicator of positive health and positive welfare in animals

A capacity for an animal to maintain or regain healthy functioning in the face of environmental disturbances is recognised as resilience. For the individual animal, dynamic properties of the trajectory of performance traits (e.g. daily milk yield), periodicity of physiological and behavioural variables (e.g. body temperature) and complexity of biological functions (e.g. behavioural repertoire) can provide indicators of its resilience. These indicators provide a view of the individual’s attempts to cope physically (and emotionally) with its non-shared micro-environment. The concept of resilience is examined as a multifaceted attribute that is hidden from direct measurement. The challenges for establishing relationships between general resilience and context-specific resilience such as disease resilience are explored by comparison with the multifaceted construct of temperament (personality). Lower variance in deviations from performance trajectories and stronger periodicity in rhythmic physiological and behavioural variables are mostly heritable and favourably associated with health and longevity. In humans, wellbeing is associated with health outcomes, and biomarkers of health are more strongly associated with eudaimonic than hedonic wellbeing. The psychological state of eudaimonia is associated with the capacity to express agency, function well, fulfill biological potential and express environmental mastery. The need for indicators of eudaimonia in animals has been suggested previously. Links between environmental mastery and the capacity to develop and express physiological, immune, behavioural, cognitive and affective competencies are examined. It is suggested that longitudinal data on individual animals can provide a precision physical indicator of eudaimonic positive welfare. In this view, positive welfare entails both eudaimonic and hedonic aspects of wellbeing, neither of which is alone sufficient to describe or to maximise positive welfare. Cumulative scores of resilience may have utility for assessing the lifetime welfare experience of the individual and when summed at the farm level may provide a metric for benchmarking welfare performance. Breeding for resilience selects for normativity of biological functions assessed against the individual animal’s own baseline of inherited and developmentally acquired potential. This differs from current approaches to selection for production, which aim to maximise production or production efficiency benchmarked against the group mean. Biological costs and trade-offs for resilience require further research.

Chronbiologically-based sub-groups in bipolar I disorder: A latent profile analysis

BackgroundBipolar disorder presents with significant phenotypic heterogeneity. The aim of this study was to investigate whether bipolar disorder, type I (BDI) subjects could be meaningfully classified into homogeneous groups according to activity, sleep, and circadian characteristics using latent profile analysis (LPA). We hypothesized that distinct BDI sub-groups would be identified based primarily on circadian-associated markers. Materials and methods105 individuals with BDI were included in the study. Seventeen activity, sleep, and circadian characteristics were assessed via actigraphy and clinical assessments. LPA was conducted to stratify our sample into homogenous sub-groups. Differences between groups on demographic, clinical, activity, sleep, and circadian characteristics were explored. ResultsTwo distinct groups were identified, a High Chronobiological Disturbance group (HCD) (56%, N = 59) and a Low Chronobiological Disturbance group (LCD) (41%; N = 46). Circadian variables were the defining characteristics in sub-group determination. Large effect sizes and magnitudes of association were noted in circadian variables between HCD and LCD sub-groups. Several circadian rhythm variables accounted for a large percentage of the variance between HCD and LCD sub-groups. No differences were noted between sub-groups on demographic characteristics and the psychiatric medications currently in use. Mood state did not significantly impact sub-group differences. LimitationsThe protocol was cross-sectional in design. Longitudinal studies are required to determine the stability of the identified sub-groups. ConclusionLPA was able to identify sub-groups in BDI with circadian variables being the most distinguishing factors in determining sub-group class membership. Future research should explore the role that circadian characteristics can play in defining sub-phenotypes of bipolar disorder.

PyActigraphy: Open-source python package for actigraphy data visualization and analysis.

Over the past 40 years, actigraphy has been used to study rest-activity patterns in circadian rhythm and sleep research. Furthermore, considering its simplicity of use, there is a growing interest in the analysis of large population-based samples, using actigraphy. Here, we introduce pyActigraphy, a comprehensive toolbox for data visualization and analysis including multiple sleep detection algorithms and rest-activity rhythm variables. This open-source python package implements methods to read multiple data formats, quantify various properties of rest-activity rhythms, visualize sleep agendas, automatically detect rest periods and perform more advanced signal processing analyses. The development of this package aims to pave the way towards the establishment of a comprehensive open-source software suite, supported by a community of both developers and researchers, that would provide all the necessary tools for in-depth and large scale actigraphy data analyses.

Effect of a dynamic lighting intervention on circadian rest-activity disturbances in cognitively impaired, older adults living in a nursing home: A proof-of-concept study

Development of non-pharmacological interventions to improve disrupted rest-activity patterns and disturbed behavior in people with dementia is an important research goal. Here we report a proof-of-concept study which evaluates the effect and applicability of a dynamic light intervention to improve rest-activity patterns in cognitively impaired, institutionalized, older adults. The study was a randomized, open-label, proof-of-concept trial of limited sample size conducted at a nursing home for older adults in a non-metropolitan area in Denmark. Participants were 24 older nursing home residents with cognitive deficiencies. Equipment for delivery of a specialized dynamic light intervention was installed in the private apartments (within the nursing home) of the residents in the experimental group (N = 12). Study duration was four weeks. The control group (N = 12) was exposed to conventional lighting. We measured activity and rest using actigraphy, functional disability, behavioral disturbances, and time in bed We performed regression analyses to examine differences between the intervention groups. Participants in the experimental group partially improved on one of three diurnal rhythm variables, but otherwise no differences were observed between the two intervention groups. The improvement was found for the intradaily variability during the first part of the intervention period indicating a more stable and less fragmented 24-h rest-activity rhythm. However, availability of staff assistance in response to impaired physical mobility of the residents seemed to be a stronger determinant of activity level and pattern. The examined intervention showed promising results but did not consistently alter circadian rest-activity patterns in older nursing home residents given the current sample size. Future studies in the field need to consider real-life applicability of the experimental intervention and the interaction and importance of other important zeitgebers than light.

Parsing Neurodynamic Information Streams to Estimate the Frequency, Magnitude and Duration of Team Uncertainty.

Neurodynamic organizations are information-based abstractions, expressed in bits, of the structure of long duration EEG amplitude levels. Neurodynamic information (NI, the variable of neurodynamic organization) is thought to continually accumulate as EEG amplitudes cycle through periods of persistent activation and deactivation in response to the activities and uncertainties of teamwork. Here we show that (1) Neurodynamic information levels were a better predictor of uncertainty and novice and expert behaviors than were the EEG power levels from which NI was derived. (2) Spatial and temporal parsing of team NI from experienced submarine navigation and healthcare teams showed that it was composed of discrete peaks with durations up to 20–60 s, and identified the involvement of activated delta waves when precise motor control was needed. (3) The relationship between NI and EEG power was complex varying by brain regions, EEG frequencies, and global vs. local brain interactions. The presence of an organizational system of information that parallels the amplitude of EEG rhythms is important as it provides a greatly reduced data dimension while retaining the essential system features, i.e., linkages to higher scale behaviors that span temporal and spatial scales of teamwork. In this way the combinatorial explosion of EEG rhythmic variables at micro levels become compressed into an intermediate system of information and organization which links to macro-scale team and team member behaviors. These studies provide an avenue for understanding how complex organizations arise from the dynamics of underlying micro-scale variables. The study also has practical implications for how micro-scale variables might be better represented, both conceptually and in terms of parsimony, for training machines to recognize human behaviors that span scales of teams.

The Influence of Intensive Anaerobic Effort on the Rhythm of Movement.

To estimate the influence of global anaerobic fatigue on rhythm performance. Fifteen young males participated in the experiment. Anaerobic fatigue was induced with 2 consecutive running-based anaerobic sprint tests (RAST). The level of lactate was controlled before the first RAST and 3 minutes after each RAST. The rhythm performance was assessed by using Optojump Next (Microgate, Bolzano, Italy). The rhythm test was conducted 3 times, before fatigue and immediately after each RAST. Eight variables of the rhythm test were analyzed: the mean frequency of jumps for the assisted and unassisted phase (XfAP and XfUAP), SD of jump frequency for the assisted and unassisted phase (SDfAP and SDfUAP), and mean absolute error for the assisted and unassisted phases of the test (XERAP and XERUAP, respectively). One-way repeated-measures analysis of variance showed a significant main effect of anaerobic effort on rhythm variables only in the unassisted phase of the test. Statistically significant differences were observed in XfUAP between the first and third rhythm measurements (F2,28 = 4.98, P < .014, ηp2=26.23%), SD of jump frequency for the unassisted phase (SDfUAP; F2,28 = 3.48, P = .05, ηp2=19.9%), and mean absolute error for the unassisted phase (XERUAP; F2,28 = 3.36, P = .006, ηp2=19.43%). The results show that rhythm of movement may be negatively influenced after intensive anaerobic fatigue. The exact mechanism of this phenomenon is not precisely defined, but both central and peripheral fatigue are suspected to be involved.

Retracted] A Study on the Application of Music Education to Improve College Students’ Mental Health in the Context of 5G

This paper provides an in‐depth study and analysis of music education to improve the mental health of college students in the context of 5G and for practical application. How to explore the ideas and methods of using music education to channel and resolve the psychological problems of this student group and then help them shape a healthy and upward psychological state, based on field research on the psychological and emotional health of contemporary higher education students, becomes an important issue that needs to be solved in front of most music educators. Musical emotions are not only related to the acoustic properties of music but also closely related to the age, gender, musical background, and social cognition of individuals. To explore the neural mechanisms by which musical rhythm affects emotional processing, it is necessary not only to achieve reasonable manipulation of rhythmic variables but also to effectively control for relevant additional variables, to clarify the relationship between rhythm and musical emotion from a theoretical perspective, and to provide operational guidance significance for bringing into play the mental health value of musical emotion. Discuss the commonalities and mutual assistance between the interactional music classroom and humanistic and positive psychology in terms of ideological connotations. Discuss the practical implications of humanistic psychology and its derivation of positive psychology in terms of self‐actualization, student‐centered view of education, associated integration and developmental educational values, psychological fluency experience, positive emotions, positive self, and positive motivation, which have common ideas with the philosophical theory of interaction, for the interactive music classroom. The characteristics and role of the music teacher in the interacting music classroom from a psychological perspective are described in terms of both teacher psychological construction and teaching attitudes. The enrichment of the ideas, psychological laws, and experiences in humanistic and positive psychology on the model of the interacting music classroom guided by the philosophical theory of interaction is discussed, divided into four subsections: suggestions for classroom goal setting, suggestions for teaching methods, teacher‐student evaluation, and teaching fragment design, aimed at making teachers and students interact easily and happily and live soberly and creatively.

An Optimal Time for Treatment-Predicting Circadian Time by Machine Learning and Mathematical Modelling.

Simple SummaryPersonalized cancer treatments show decreased side-effects and improved treatment success. One aspect of individualized treatment is the timing of medicine intake, which may be optimized based on the biological diurnal rhythm of the patient. The personal biological time can be assessed by a variety of tools not yet commonly included in diagnostics. We review these tools with a focus on their applicability in a clinical context. Using biological samples from the patient, most tools predict individual time using machine learning methodologies, often supported by rhythmicity analysis and mathematical core-clock models. We compare different approaches and discuss possible promising future directions.Tailoring medical interventions to a particular patient and pathology has been termed personalized medicine. The outcome of cancer treatments is improved when the intervention is timed in accordance with the patient’s internal time. Yet, one challenge of personalized medicine is how to consider the biological time of the patient. Prerequisite for this so-called chronotherapy is an accurate characterization of the internal circadian time of the patient. As an alternative to time-consuming measurements in a sleep-laboratory, recent studies in chronobiology predict circadian time by applying machine learning approaches and mathematical modelling to easier accessible observables such as gene expression. Embedding these results into the mathematical dynamics between clock and cancer in mammals, we review the precision of predictions and the potential usage with respect to cancer treatment and discuss whether the patient’s internal time and circadian observables, may provide an additional indication for individualized treatment timing. Besides the health improvement, timing treatment may imply financial advantages, by ameliorating side effects of treatments, thus reducing costs. Summarizing the advances of recent years, this review brings together the current clinical standard for measuring biological time, the general assessment of circadian rhythmicity, the usage of rhythmic variables to predict biological time and models of circadian rhythmicity.

Delayed sleep-onset and biological age: late sleep-onset is associated with shorter telomere length.

We evaluated the relationship between leukocyte telomere length (LTL) and sleep duration, insomnia symptoms, and circadian rhythm, to test whether sleep and chronobiological dysregulations are associated with cellular aging. Data from the Netherlands Study of Depression and Anxiety (N = 2,936) were used at two waves 6 years apart, to measure LTL. Telomeres shorten during the life span and are important biomarkers for cellular aging. LTL was assessed by qualitative polymerase chain reaction and converted into base pair number. Sleep parameters were: sleep duration and insomnia symptoms from the Insomnia Rating Scale. Circadian rhythm variables were: indication of Delayed Sleep Phase Syndrome (DSPS), mid-sleep corrected for sleep debt on free days (MSFsc), sleep-onset time, and self-reported chronotype, from the Munich Chronotype Questionnaire. Generalized estimating equations analyzed the associations between LTL, sleep, and chronobiological factors, adjusted for baseline age, sex, North European ancestry, and additionally for current smoking, depression severity, obesity, and childhood trauma. Indicators of delayed circadian rhythm showed a strong and consistent effect on LTL, after adjustment for sociodemographic and health indicators. Late MSFsc (B = -49.9, p = .004), late sleep-onset time (B = -32.4, p = .001), indication of DSPS (B = -73.8, p = .036), and moderately late chronotype in adulthood (B = -71.6, p = .003) were associated with significantly shorter LTL across both waves; whereas sleep duration and insomnia symptoms were not. Extremely early chronotype showed significantly less LTL shortening than intermediate chronotype (B = 161.40, p = .037). No predictors showed accelerated LTL attrition over 6 years. Individuals with delayed circadian rhythm have significantly shorter LTL, but not faster LTL attrition rates.

Ring states in swarmalator systems

Synchronization is a universal phenomenon, occurring in systems as disparate as Japanese tree frogs and Josephson junctions. Typically, the elements of synchronizing systems adjust the phases of their oscillations, but not their positions in space. The reverse scenario is found in swarming systems, such as schools of fish or flocks of birds; now the elements adjust their positions in space, but without (noticeably) changing their internal states. Systems capable of both swarming and synchronizing, dubbed swarmalators, have recently been proposed, and analyzed in the continuum limit. Here, we extend this work by studying finite populations of swarmalators, whose phase similarity affects both their spatial attraction and repulsion. We find ring states, and compute criteria for their existence and stability. Larger populations can form annular distributions, whose density we calculate explicitly. These states may be observable in groups of Japanese tree frogs, ferromagnetic colloids, and other systems with an interplay between swarming and synchronization.

Circadian rhythm abnormalities and autonomic dysfunction in patients with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis.

Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) patients frequently show autonomic symptoms which may be associated with a hypothalamic dysfunction. This study aimed to explore circadian rhythm patterns in rest and activity and distal skin temperature (DST) and their association with self-reported outcome measures, in CFS/ME patients and healthy controls at two different times of year. Ten women who met both the 1994 CDC/Fukuda definition and 2003 Canadian criteria for CFS/ME were included in the study, along with ten healthy controls matched for age, sex and body mass index. Self-reported measures were used to assess fatigue, sleep quality, anxiety and depression, autonomic function and health-related quality of life. The ActTrust actigraph was used to record activity, DST and light intensity, with data intervals of one minute over seven consecutive days. Sleep variables were obtained through actigraphic analysis and from subjective sleep diary. The circadian variables and the spectral analysis of the rhythms were calculated. Linear regression analysis was used to evaluate the relationship between the rhythmic variables and clinical features. Recordings were taken in the same subjects in winter and summer. Results showed no differences in rhythm stability, sleep latency or number of awakenings between groups as measured with the actigraph. However, daily activity, the relative amplitude and the stability of the activity rhythm were lower in CFS/ME patients than in controls. DST was sensitive to environmental temperature and showed lower nocturnal values in CFS/ME patients than controls only in winter. A spectral analysis showed no differences in phase or amplitude of the 24h rhythm, but the power of the second harmonic (12h), revealed differences between groups (controls showed a post-lunch dip in activity and peak in DST, while CFS/ME patients did not) and correlated with clinical features. These findings suggest that circadian regulation and skin vasodilator responses may play a role in CFS/ME.

Associations between the prognostic indicators rest/activity rhythm and diurnal cortisol profiles in patients with lung cancer

Two measures of host rhythmicity, rest/activity and diurnal cortisol secretion rhythms, have demonstrated prognostic significance across several cancer types. We previously reported a significant correlation between these two parameters among presurgical breast cancer patients. The association between rest/activity and cortisol rhythms has not been reported among patients with lung cancer. Patients diagnosed within the past five years collected salivary cortisol twice a day and wore actigraphy devices for 10 consecutive days. Most of the 65 patients (67%) were female, non-Hispanic white (78%), averaging 23 months post diagnosis and diagnosed with advanced (41%, n = 27) or metastatic (24%, n = 16) disease. Clinical characteristics were not associated with rhythm variables. Spearman correlations tested hypotheses. Rest/activity rhythm was associated with steeper diurnal slope (rho = −0.301, p = 0.024). Nighttime restfulness was associated with lower mean (rho = −0.312, p = 0.018) and bedtime cortisol (rho = −0.347, p = 0.008), while daytime sedentary behavior was associated with higher diurnal mean (rho = 0.368, p = 0.005) and bedtime cortisol (rho = 0.355, p = 0.007). These measures offer insight into distinct host rhythms (behavioral and endocrine). While factors contributing to the disruption of these rhythms have not been identified in human cancer studies, their significant associations imply a shared variance that may reflect endogenous circadian phase. These and other rhythm metrics may have the combined potential to robustly measure host circadian disruption and help determine if it is a cause, correlate or marker of lung cancer progression.

Rhythmic characteristics in aging: A study on Zurich German

Age-related changes in speech production influence both speech segmental and suprasegmental characteristics. Previous research focussed on changes in voice quality, vowel formant patterns, f0 and speech rate due to aging but only little attention has been paid on speech rhythm (durational and dynamic). In this study we analyzed the segmental durational variability as well as the syllabic intensity variability between 60 Zurich German speakers ranging in age between 20 and 81 years. Speakers read 90 sentences in Zurich German. Between-speaker durational variability across age was quantified through a variety of different rhythmic variables (%V, ΔCLn, ΔVLn, rPVI-C, nPVI-V, %VO, varcoVO, nPVI-VO, ΔPeak, varcoPeak, and nPVI-Peak). Intensity variability was computed by taking the standard deviations, variation coefficients and PVIs of average syllable intensity and syllable peak intensity values across sentences. Results based on durational measurements show that with aging there is an increase in %V and r-PVI-C. Aged voices also present lower variability in the consonantal and especially in the vocalic intervals (nPVI-V and ΔVLn). We argue that changes in the physical characteristics as well as in the neural control mechanisms of the articulators might play a significant role in age-related rhythmic changes.

0701 CIRCADIAN TAU DIFFERENCES IN BIOLOGICAL, BEHAVIOURAL AND SLEEPINESS RHYTHMS IN DELAYED SLEEP-WAKE PHASE DISORDER AND NON-24-HOUR SLEEP-WAKE RHYTHM DISORDER PATIENTS

In this study we investigated biological, sleepiness and behavioural rhythm period lengths (i.e., taus) of Delayed Sleep-Wake Phase Disorder (DSWPD), Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD) patients and healthy control sleepers. We also ran cross-correlation analyses between different rhythm variables to examine phase angle of entrainment. The aim was to explore if behavioural rhythms, in addition to the biological circadian rhythms contribute to misalignments of sleep timing symptomatic of DSWPD and N24SWD. Twenty-six DSWPD participants who met diagnostic criteria (17m, 9f, age: 21.85 ± 4.97 years) and 18 controls (10m, 8f, age: 23.72 ± 5.10 years) participated in an 80-hour modified constant routine. Additionally, 4 full-sighted patients (3m, 1f, age: 25.75 ± 4.99 years) were diagnosed with N24SWD and included as a discrete study group. A forced-desynchrony ultradian protocol of 1-hour ‘days’ in dim light, controlled conditions alternated 20-minute sleep opportunities with 40-minute enforced wakefulness. Subjective sleepiness ratings were recorded prior to every sleep opportunity and median reaction time (vigilance) was measured hourly. Amount of sleep obtained (sleep propensity) was derived from 20-minute sleep opportunities to quantify hourly objective sleepiness. Hourly core body temperature was recorded and salivary melatonin assayed to measure endogenous circadian rhythms. Rhythm data were curved using the 2-component cosine model. DSWPD and N24SWD patients had significantly longer melatonin and temperature taus compared to controls. There were no significant tau differences between groups as measured by subjective sleepiness, sleep propensity and vigilance rhythms. However, DSWPD patients showed a greater interval between maximum sleep propensity and minimum core body temperature. Their sleep propensity rhythms lagged core temperature rhythms by an hour more compared to controls’ sleep propensity and core temperature rhythms. The findings provide further evidence that delayed circadian rhythms in DSWPD may result from larger phase angles between core body temperature and sleep propensity. This interval may result in later sleep timing in DSWPD patients relative to their circadian timing thus masking their light exposure during a time that is critical to phase-advancing the circadian system. This project was funded by the Australian Research Council.

Chronic Low Quality Sleep Impairs Postural Control in Healthy Adults

The lack of sleep, both in quality and quantity, is an increasing problem in modern society, often related to workload and stress. A number of studies have addressed the effects of acute (total) sleep deprivation on postural control. However, up to date, the effects of chronic sleep deficits, either in quantity or quality, have not been analyzed. Thirty healthy adults participated in the study that consisted of registering activity with a wrist actigraph for more than a week before performing a series of postural control tests. Sleep and circadian rhythm variables were correlated and the sum of activity of the least active 5-h period, L5, a rhythm variable, obtained the greater coefficient value with sleep quality variables (wake after sleep onset WASO and efficiency sleep). Cluster analysis was performed to classify subjects into two groups based on L5 (low and high). The balance tests scores used to asses postural control were measured using Biodex Balance System and were compared between the two groups with different sleep quality. The postural tests were divided into dynamic (platform tilt with eyes open, closed and cursor) and static (clinical test of sensory integration). The results showed that during the tests with eyes closed, the group with worse sleep quality had also worse postural control performance. Lack of vision impairs postural balance more deeply in subjects with chronic sleep inefficiency. Chronic poor sleep quality impairs postural control similarly to total sleep deprivation.

Daily and seasonal rhythms in immune responses of splenocytes in the freshwater snake, Natrix piscator.

Present study was designed to examine daily and seasonal variability in the innate immune responses of splenocytes in the fresh water snake, Natrix piscator. Animals were mildly anesthetized and spleen was aseptically isolated and processed for macrophage phagocytosis, NBT reduction, nitrite production, splenocyte proliferation and serum lysozyme activity. Samples were collected at seven time points, viz., 0000, 0400, 0800, 1200, 1600, 2000 and 0000 h during three different seasons, namely summer, winter and spring. Cosinor analysis revealed that percent phagocytosis had a significant 24-h rhythm during summer and spring seasons. The peaks of rhythms in NBT reduction and nitrite release occurred in the morning hours at 10.88 h and 8.31 h, respectively, in winter. A significant 24-h rhythm was also observed in lysozyme concentration and splenocyte proliferation (both Basal and Concanavalin A stimulated) in all three seasons. A significant phase shift in splenocyte proliferation was obtained with a trend of delayed phase shift from winter to spring and from spring to summer. Of the nine variables, significant annual (seasonal) rhythms were detected in almost all variables, excluding phagocytic and splenosomatic indices. All rhythmic variables, except spleen cellularity, exhibited tightly synchronized peaks coinciding with the progressive and recrudescence phases of annual reproductive cycle. It is concluded that the snake synchronizes its daily and seasonal immune activity with the corresponding external time cues. The enhancement of immune function coinciding with one of its crucial reproductive phases might be helping it to cope with the seasonal stressors, including abundance of pathogens, which would otherwise jeopardize the successful reproduction and eventual survival of the species.

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

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. 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. 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. 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.

Midpoint of sleep on school days is associated with depression among adolescents

Depression is a serious and prevalent disease among adolescents. Identifying possible factors involved with its genesis and presentation is an important task for researchers and clinical practitioners. The individual’s chronotype and social jetlag have been associated with depression in different populations. However, information on this is lacking among adolescents. The objective of this cross-sectional study was to examine the relationship between chronotype (midpoint of sleep) and social jetlag with the presence of depression symptoms in young students. We assessed 351 students aged 12–21 years old. They answered a questionnaire on demographic characteristics, the Munich Chronotype Questionnaire (MCTQ) and the Beck Depression Inventory (BDI). Demographic characteristics (age, sex and classes’ schedule) and circadian rhythmic variables for school and free days (sunlight exposure, sleep duration, midpoint of sleep and social jetlag) were taken as factors and the presence of at least mild depression symptoms as outcome. In univariate analysis, girls (χ2 = 5.01, p ≤ 0.05) and evening students (χ2 = 6.63, p ≤ 0.05) were more frequently present among the depressed. Also, the depression group was significantly delayed for both midpoints of sleep during school (t = 2.84, p ≤ 0.01) and free days (t = 2.20, p ≤ 0.05). The two groups did not differ in relation to their social jetlag hours (t = −0.68, p = 0.501) neither subjects with two or more hours of social jetlag were more frequent among the depressed (χ2 = 1.00, p = 0.317). In multivariate analysis, the model that best explained our outcome (R2 = 0.058, F = 2.318, p ≤ 0.05) included sex (β = −0.12, p ≤ 0.05) and the midpoint of sleep on school days (β = −0.21, p ≤ 0.001) as significant predictor variables. A sleep phase delay (later midpoints of sleep for school and free days) was associated with higher levels of depression. However, we were not able to detect similar relationship with the social jetlag hours. This could be attributed to the fact that our sample showed a smaller amount of social jetlag, possibly because even during free days a social routine, this time parents’ rules, limited the observation from what could be a natural tendency to sleep later and over. Yet, even when considering the group with more social jetlag, we did not find an association. Perhaps, this variable will only manifest its effect if it is maintained for longer periods throughout life. Additionally, when considering all the variables together, the midpoint of sleep on school days was pointed as the predictor of greatest weight for depression, together with the factor sex. Young girls, possibly earlier types, who are required to study in the evening have more chances of presenting depression symptoms. This study explicit some peculiar characteristics of the assessment of chronobiological variables in the young, such as the presence of an imposed social routine also during free days. Therefore, the expression of chronotype under the influence of the weekly social schedule (midpoint of sleep on school days) could be a more useful marker to measure the stress produced from the mismatch between external and inner rhythms rather than social jetlag. This also reinforces the importance of reconsidering the weekly routine imposed on young people.

Relations between social rhythm, sleep phase, and minor psychiatric symptoms in healthy workers

The objective of this study was to determine the correlation of social rhythm, sleep phase, and exposure to light with in healthy workers exhibiting minor psychiatric symptoms. This was a cross-sectional study that included 143 healthy workers. Minor psychiatric symptoms, evaluated by SRQ-20; social rhythm by the SRM Scale; exposure to light and sleep variables, by MCTQ; correlations, analyzed by Pearson's correlation coefficient, and multivariate regression analysis utilized. Quantity of activities correlated with schooling and mean duration of sleep and, inversely, Mid-Sleep-on Free Days (MSF) and minor psychiatric symptoms; daily regularity correlated with age, minor psychiatric symptoms, and number of days worked; minor psychiatric symptoms correlated inversely with quantity of activities and regularity. Social rhythm variables had an inverse correlation with minor psychiatric symptoms. Minor psychiatric symptoms were explained by low levels of activity rather than by low regularity of social rhythm. Age, number of days worked per week, and minor psychiatric symptoms interfere with the regularity of social rhythm.

Depressive Symptoms and Circadian Activity Rhythm Disturbances in Community-Dwelling Older Women

Aging is associated with changes in circadian rhythms. Current evidence supports a role for circadian rhythms in the pathophysiology of depression. However, little is known about the relationship between depressive symptoms and circadian activity rhythms in older adults. We examined this association in community-dwelling older women. We performed a cross-sectional analysis of 3,020 women (mean age: 83.55 ± 3.79 years) enrolled in the Study of Osteoporotic Fractures. Depressive symptoms were assessed with the Geriatric Depression Scale categorizing participants as "normal" (0-2; referent group, N= 1,961), "some depressive symptoms" (3-5, N= 704), or "depressed" (≥6, N= 355). Circadian activity rhythm variables were measured using wrist actigraphy. In age-adjusted and Study of Osteoporotic Fractures site-adjusted models, greater levels of depressive symptoms were associated with decreased amplitude (height; df= 3,014, t=-11.31, p for linear trend<0.001), pseudo F-statistic (robustness; df= 3,014, t=-8.07, p for linear trend<0.001), and mesor (mean modeled activity; df=3014, t=-10.36, p for linear trend<0.001) of circadian activity rhythms. Greater levels of depressive symptoms were also associated with increased odds of being in the lowest quartile for amplitude (df= 1, χ(2)= 9240, p for linear trend<0.001), pseudo F-statistic (df= 1, χ(2)= 49.73, p for linear trend<0.001), and mesor (df= 1, χ(2)= 81.12, pfor linear trend<0.001). These associations remained significant in multivariate models. Post-hoc analyses comparing mean amplitude, mesor, and pseudo F-statistic values pair-wise between depression-level groups revealed significant differences between women with "some depressive symptoms" and the "normal" group. These data suggest a graded association between greater levels of depressive symptoms and more desynchronization of circadian activity rhythms in community-dwelling older women. This association was observed even for women endorsing subthreshold levels of depressive symptoms.