Association of intrinsic circadian period with morningness–eveningness, usual wake time, and circadian phase.

2001 ◽  
Vol 115 (4) ◽  
pp. 895-899 ◽  
Author(s):  
Jeanne F. Duffy ◽  
David W. Rimmer ◽  
Charles A. Czeisler
Keyword(s):  
Circadian Period ◽  
Wake Time ◽  
Circadian Phase

scholarly journals 0433 Targeting Light Sensitivity Parameters to Optimize Circadian Phase Predictions

SLEEP ◽  
2020 ◽  
Vol 43 (Supplement_1) ◽  
pp. A166-A166
Author(s):  
J E Stone ◽  
E M McGlashan ◽  
S W Cain ◽  
A J Phillips
Keyword(s):  
Sensitivity Analysis ◽  
Circadian Clock ◽  
Mean Absolute Error ◽  
Light Response ◽  
Absolute Error ◽  
Light Sensitivity ◽  
Model Parameters ◽  
Circadian Period ◽  
Individual Level ◽  
Circadian Phase

Abstract Introduction Existing models of the human circadian clock accurately predict phase at group-level but not at individual-level. Interindividual variability in light sensitivity is not currently accounted for in these models and may be a practical approach to improving individual-level predictions. Using the gold-standard predictive model, we (i) identified whether varying light sensitivity parameters produces meaningful changes in predicted phase in field conditions; and (ii) tested whether optimizing parameters can significantly improve accuracy of circadian phase prediction. Methods Healthy participants (n=12, 7 women, aged 18-26) underwent continuous light and activity monitoring for 3 weeks (Actiwatch Spectrum). Salivary dim light melatonin onset (DLMO) was measured each week. A model of the human circadian clock and its response to light was used to predict the three weekly DLMO times using the individual’s light data. A sensitivity analysis was performed varying three model parameters within physiological ranges: (i) amplitude of the light response [p]; (ii) advance vs. delay bias of the light response [K]; and (iii) intrinsic circadian period [tau]. These parameters were then fitted using least squares estimation to obtain optimal predictions of DLMO for each individual. Accuracy was compared between optimized parameters and default parameters. Results The default model predicted DLMO with mean absolute error of 1.02h. Sensitivity analysis showed the average range of variation in predicted DLMOs across participants was 0.65h for p, 4.28h for K and 3.26h for tau. Fitting parameters independently, we found mean absolute error of 0.85h for p, 0.71h for K and 0.75h for tau. Fitting p and K together reduced mean absolute error to 0.57h. Conclusion Light sensitivity parameters capture similar or greater variability in phase as intrinsic circadian period, indicating they are a viable option for individualising circadian phase predictions. Future prospective work is needed using measures of light sensitivity to validate this approach. Support N/A

scholarly journals Circadian phase, circadian period and chronotype are reproducible over months

2017 ◽  
Vol 35 (2) ◽  
pp. 280-288 ◽  
Author(s):  
Thomas Kantermann ◽  
Charmane I Eastman
Keyword(s):  
Circadian Period ◽  
Circadian Phase

scholarly journals Mutations in EID1 and LNK2 caused light-conditional clock deceleration during tomato domestication

2018 ◽  
Vol 115 (27) ◽  
pp. 7135-7140 ◽  
Author(s):  
Niels A. Müller ◽  
Lei Zhang ◽  
Maarten Koornneef ◽  
José M. Jiménez-Gómez
Keyword(s):  
Clock Gene ◽  
Genetic Basis ◽  
Allelic Variation ◽  
Genomic Region ◽  
Circadian Period ◽  
Circadian Phase ◽  
Signatures Of Selection ◽  
Period Lengthening ◽  
Phytochrome B1 ◽  
Light Input

Circadian period and phase of cultivated tomato (Solanum lycopersicum) were changed during domestication, likely adapting the species to its new agricultural environments. Whereas the delayed circadian phase is mainly caused by allelic variation of EID1, the genetic basis of the long circadian period has remained elusive. Here we show that a partial deletion of the clock gene LNK2 is responsible for the period lengthening in cultivated tomatoes. We use resequencing data to phylogenetically classify hundreds of tomato accessions and investigate the evolution of the eid1 and lnk2 mutations along successive domestication steps. We reveal signatures of selection across the genomic region of LNK2 and different patterns of fixation of the mutant alleles. Strikingly, LNK2 and EID1 are both involved in light input to the circadian clock, indicating that domestication specifically targeted this input pathway. In line with this, we show that the clock deceleration in the cultivated tomato is light-dependent and requires the phytochrome B1 photoreceptor. Such conditional variation in circadian rhythms may be key for latitudinal adaptation in a variety of species, including crop plants and livestock.

Circadian sleep-wake cycle organization in squirrel monkeys

1985 ◽  
Vol 248 (3) ◽  
pp. R353-R362 ◽  
Author(s):  
D. B. Wexler ◽  
M. C. Moore-Ede
Keyword(s):  
Sleep Onset ◽  
Nrem Sleep ◽  
Squirrel Monkeys ◽  
Circadian Cycle ◽  
Circadian Period ◽  
Constant Illumination ◽  
Circadian Phase ◽  
Internal Phase ◽  
The Difference ◽  
The Relationship

To investigate the relationship between circadian rhythms of body temperature and sleep-wake stages, four squirrel monkeys were prepared for unrestrained monitoring of temperature, locomotor activity, electroencephalogram, electroculogram, and electromyogram. Continuous records for each animal were made for several 12-h light-dark (LD) cycles and then after a few days in constant illumination (LL). All animals maintained consolidated sleep-wake cycles and had a longer circadian period (mean 24.7 h) in LL than in LD (mean 24.1 h). The increased period reflected greater time per circadian cycle spent awake in LL (mean 14.0 h) than in LD (mean 12.8 h). Total night NREM sleep was less in LL (mean 6.5 h) than in LD (mean 8.2 h). Sleep onset occurred at later phases in LL (187 +/- 6 degrees) than in LD (170 +/- 2 degrees). Because the circadian phase measure of NREM sleep was unchanged between LD and LL conditions, the difference in sleep onsets reflected balanced changes in NREM circadian waveforms. Wake-up phases were the same in both conditions (mean 342 degrees). In summary, during free run squirrel monkeys maintain a stable consolidated circadian sleep-wake cycle with a period greater than 24 h, but they exhibit only minimal internal phase restructuring.

scholarly journals A functional context for heterogeneity of the circadian clock in cells

PLoS Biology ◽  
2020 ◽  
Vol 18 (10) ◽  
pp. e3000927
Author(s):  
Martha Merrow ◽  
Mary Harrington
Keyword(s):  
Circadian Clock ◽  
Building Blocks ◽  
Circadian Period ◽  
Top Down ◽  
Bottom Up ◽  
Stochastic Generation ◽  
Circadian Phase ◽  
Functional Context ◽  
Definition Of

Characterization of circadian systems at the organism level—a top-down approach—has led to definition of unifying properties, a hallmark of the science of chronobiology. The next challenge is to use a bottom-up approach to show how the molecular workings of the cellular circadian clock work as building blocks of those properties. We review new studies, including a recently published PLOS Biology paper by Nikhil and colleagues, that show how programmed but also stochastic generation of variation in cellular circadian period explain important adaptive features of entrained circadian phase.

scholarly journals Prediction Of Shiftworker Alertness, Sleep, And Circadian Phase Using A Model Of Arousal Dynamics Constrained By Shift Schedules And Light Exposure

SLEEP ◽  
2021 ◽  
Author(s):  
Stuart A Knock ◽  
Michelle Magee ◽  
Julia E Stone ◽  
Saranea Ganesan ◽  
Megan D Mulhall ◽  
...  
Keyword(s):  
Light Exposure ◽  
Night Shift ◽  
Vigilance Task ◽  
Study Data ◽  
Accurate Prediction ◽  
Environmental Constraints ◽  
Wake Time ◽  
Circadian Phase ◽  
Shift Schedules ◽  
And Performance

Abstract Study Objectives The study aimed to, for the first time, (i) compare sleep, circadian phase, and alertness of Intensive Care Unit (ICU) nurses working rotating shifts with those predicted by a model of arousal dynamics; and (ii) investigate how different environmental constraints affect predictions and agreement with data. Methods The model was used to simulate individual sleep-wake cycles, urinary 6-sulphatoxymelatonin (aMT6s) profiles, subjective sleepiness on the Karolinska Sleepiness Scale (KSS), and performance on a Psychomotor Vigilance Task (PVT) of 21 ICU nurses working day, evening, and night shifts. Combinations of individual shift schedules, forced wake time before/after work and lighting, were used as inputs to the model. Predictions were compared to empirical data. Simulations with self-reported sleep as an input were performed for comparison. Results All input constraints produced similar prediction for KSS, with 56-60% of KSS scores predicted within ±1 on a day and 48-52% on a night shift. Accurate prediction of an individual’s circadian phase required individualised light input. Combinations including light information predicted aMT6s acrophase within ±1 h of the study data for 65% and 35-47% of nurses on diurnal and nocturnal schedules. Minute-by-minute sleep-wake state overlap between the model and the data was between 81±6% and 87±5% depending on choice of input constraint. Conclusions The use of individualised environmental constraints in the model of arousal dynamics allowed for accurate prediction of alertness, circadian phase and sleep for more than half of the nurses. Individual differences in physiological parameters will need to be accounted for in the future to further improve predictions.

841 PAP Therapy Data Provides Clues To Comorbid Sleep Disorders

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A327-A328
Author(s):  
Bethany Bartley ◽  
Alice Cai ◽  
Lawrence Epstein
Keyword(s):  
Sleep Disorders ◽  
Behavioral Treatment ◽  
Treatment Guidelines ◽  
Good Compliance ◽  
Wake Time ◽  
Sleep Inertia ◽  
Circadian Phase ◽  
Obstructive Sleep ◽  
Disease Case ◽  
Timing Data

Abstract Introduction Obstructive sleep apnea (OSA) is a common condition and positive airway pressure (PAP) therapy is the treatment of choice. Treatment guidelines recommend monitoring objective PAP usage data to track treatment efficacy. A typical report includes the percentage of days/month and cumulative hours/day a PAP device was used. In addition, PAP therapy timing can be graphically viewed with use plotted by time/day. This latter presentation reveals patterns of usage that can identify comorbid sleep disorders. Report of case(s) Case 1: A 65-year-old male with OSA presented with sleep inertia despite compliance with PAP therapy. Therapy timing data revealed a delayed circadian phase, with bedtime of 4 am and wake time of 1 pm. Circadian phase advancement therapy was added. Case 2: An 86-year-old male with OSA presented with daytime sleepiness after years of excellent PAP usage. Two years earlier, he was diagnosed with Parkinson’s disease and developed increasing afternoon sleepiness. Compliance data showed a mild reduction in PAP usage. However, therapy timing data revealed an irregular sleep-wake rhythm disorder with sleep scattered around the clock, consistent with neurodegenerative disease. Case 3: A 70 year-old-female with PTSD and OSA presented with persistent tiredness and difficulty initiating and maintaining sleep despite good compliance with PAP therapy. Her timing data showed irregular sleep times with long gaps in usage suggestive of sleep maintenance insomnia. After starting a behavioral treatment regimen her pattern regularized and awakenings reduced, seen by consistent PAP use. Case 4: An 80-year-old female with OSA complained of early morning awakenings despite PAP use with good compliance. Review of PAP therapy timing revealed a pattern suggestive of advanced sleep-wake phase disorder. Circadian phase delay therapy was started. Conclusion Patients with OSA on PAP therapy may have comorbid sleep disorders impacting sleep quality. PAP therapy data can provide information on sleep-wake behavior similar to actigraphy to help diagnose these conditions and track treatment response. Support (if any) None

scholarly journals Separate and interacting effects of the endogenous circadian system and behaviors on plasma aldosterone in humans

2019 ◽  
Vol 316 (2) ◽  
pp. R157-R164 ◽  
Author(s):  
Saurabh S. Thosar ◽  
Jose F. Rueda ◽  
Alec M. Berman ◽  
Michael R. Lasarev ◽  
Maya X. Herzig ◽  
...  
Keyword(s):  
Circadian System ◽  
Plasma Aldosterone ◽  
Jet Lag ◽  
Circadian Cycle ◽  
Circadian Period ◽  
Nocturnal Sleep ◽  
Circadian Phase ◽  
Dim Light ◽  
And Behaviors ◽  
Healthy Participants

Measurements of aldosterone for diagnosis of primary aldosteronism are usually made from blood sampled in the morning when aldosterone typically peaks. We tested the relative contributions and interacting influences of the circadian system, ongoing behaviors, and prior sleep to this morning peak in aldosterone. To determine circadian rhythmicity and separate effects of behaviors on aldosterone, 16 healthy participants completed a 5-day protocol in dim light while all behaviors ranging from sleep to exercise were standardized and scheduled evenly across the 24-h circadian period. In another experiment, to test the separate effects of prior nocturnal sleep or the inactivity that accompanies sleep on aldosterone, 10 healthy participants were studied across 2 nights: 1 with sleep and 1 with maintained wakefulness (randomized order). Plasma aldosterone was measured repeatedly in each experiment. Aldosterone had a significant endogenous rhythm ( P < 0.001), rising across the circadian night and peaking in the morning (~8 AM). Activity, including exercise, increased aldosterone, and different behaviors modulated aldosterone differently across the circadian cycle (circadian phase × behavior interaction; P < 0.001). In the second experiment, prior nocturnal sleep and prior rested wakefulness both increased plasma aldosterone ( P < 0.001) in the morning, to the same extent as the change in circadian phases between evening and morning. The morning increase in aldosterone is due to effects of the circadian system plus increased morning activities and not prior sleep or the inactivity accompanying sleep. These findings have implications for the time of and behaviors preceding measurement of aldosterone, especially under conditions of shift work and jet lag.

Later endogenous circadian temperature nadir relative to an earlier wake time in older people

1998 ◽  
Vol 275 (5) ◽  
pp. R1478-R1487 ◽  
Author(s):  
Jeanne F. Duffy ◽  
Derk-Jan Dijk ◽  
Elizabeth B. Klerman ◽  
Charles A. Czeisler
Keyword(s):  
Older People ◽  
Light Exposure ◽  
Young Men ◽  
Early Morning ◽  
Wake Time ◽  
Circadian Phase ◽  
Age Related ◽  
High Prevalence ◽  
Circadian Timing System ◽  
Older Subjects

The contribution of the circadian timing system to the age-related advance of sleep-wake timing was investigated in two experiments. In a constant routine protocol, we found that the average wake time and endogenous circadian phase of 44 older subjects were earlier than that of 101 young men. However, the earlier circadian phase of the older subjects actually occurred later relative to their habitual wake time than it did in young men. These results indicate that an age-related advance of circadian phase cannot fully account for the high prevalence of early morning awakening in healthy older people. In a second study, 13 older subjects and 10 young men were scheduled to a 28-h day, such that they were scheduled to sleep at many circadian phases. Self-reported awakening from scheduled sleep episodes and cognitive throughput during the second half of the wake episode varied markedly as a function of circadian phase in both groups. The rising phase of both rhythms was advanced in the older subjects, suggesting an age-related change in the circadian regulation of sleep-wake propensity. We hypothesize that under entrained conditions, these age-related changes in the relationship between circadian phase and wake time are likely associated with self-selected light exposure at an earlier circadian phase. This earlier exposure to light could account for the earlier clock hour to which the endogenous circadian pacemaker is entrained in older people and thereby further increase their propensity to awaken at an even earlier time.

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