New smartwatch technology allows researchers to study this clock without limiting subjects to a specific environment. Over a two-year period, we collected daily mood survey scores and Fitbit data from more than 2, first-year doctors. Citation: Shapiro B, Fang Y, Sen S, Forger D Unraveling the interplay of circadian rhythm and sleep deprivation on mood: A Real-World Study on first-year physicians.

PLOS Digit Health 3 1 : e Editor: Danilo Pani, University of Cagliari: Universita degli Studi Di Cagliari, ITALY. Received: April 30, ; Accepted: December 25, ; Published: January 31, Copyright: © Shapiro et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: SS, YF and DBF received funding and salary from NIMH R DBF also received salary from WNF, and NSF DMS grant The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Arcascope did not sponsor this research. Internal hour circadian biological clocks regulate many physiological processes in an organism such as metabolism, hormone secretion, and the sleep-wake cycle.

Circadian rhythms are any physiological process that follows a hour cycle and are primarily regulated by these biological, or circadian, clocks. Clock genes have been found to be expressed in cells throughout the body and these cells express an internal rhythm that in turn induce regulatory circadian rhythms on local tissue and organs [ 1 — 3 ].

The central clock within the human body resides in the suprachiasmatic nucleus of the brain and acts to synchronize all these peripheral clocks [ 4 ]. Circadian rhythms are distinct from sleep-wake cycles or sleep deprivation because of their primary regulation through biological clocks rather than environmental cues.

These rhythms endure even in the absence of external cues or environmental influences as they are inherently driven by internal mechanisms. In these individuals, circadian clocks measured through endogenous temperature and plasma melatonin levels do not always re-align to match the shift work schedule [ 5 , 6 ].

Circadian rhythms, sleep-wake cycles, and sleep deprivation all affect physiology. Misalignment of these rhythms can lead to adverse health outcomes such as psychiatric and metabolic disorders, cardiovascular disease, and cancer [ 7 , 8 ].

One important aspect of our physiology which is under the control of circadian timekeeping is mood. Mood is the constantly changing emotional lens which we see and interact with our environment.

Adverse mood can lead to many health challenges including cardiovascular disease, diabetes, and suicide [ 9 — 11 ]. Thus, a careful understanding of mood is important for optimal health. There has been much interest in connecting mood, circadian rhythms, and time awake in healthy individuals.

It has been shown that there is a diurnal variation in mood and that mood deteriorates with sleep deprivation [ 12 — 15 ]. Furthermore, it has been demonstrated that mood varies with circadian phase and that, depending on the phase, mood either improved or worsened based on time awake [ 16 ].

However, such studies were in controlled conditions, had smaller number of subjects, or may not have used recent statistical methods [ 12 , 17 — 20 ]. Additional evidence highlighting the close relationship between mood and the circadian pacemaker can be observed in individuals experiencing mental health conditions marked by mood disturbances.

In such cases, circadian rhythms have been found to be disrupted, with the type of this impact differing based on the specific disorder. In the case of depression, cortisol and temperature measurements have indicated a phase delay accompanied by a reduction in rhythmic amplitude [ 21 , 22 ].

Mood displays an alternative diurnal variation in these individuals. Instead of peaking in the late afternoon as seen in healthy individuals, it progressively rises throughout the evening [ 15 , 23 ]. Mania, which is marked by a significant decrease in sleep requirement along with an abnormally heightened mood, has been linked to a phase advance in the biological clock [ 24 ].

Recently, genetic risk factors for affective disorders have been identified. The a-kinase anchoring protein 11 AKAP11 gene emerged as a risk factor for bipolar disorder with this variant occurring 7 times higher in this population [ 25 ].

AKAP11 interacts with glycogen synthetic kinase 3 GSK3B which is a key component of the circadian clock that modulates neuronal excitability through the regulation of persistent sodium channels [ 26 ]. Studying circadian rhythms in humans has previously required invasive laboratory monitoring such as minute by minute rectal temperature measurements or frequent blood draws [ 27 ].

These measurements can require participants to be confined to a laboratory setting for days or even weeks. While some of the methods have been adapted to non-laboratory settings, they still require subjects to spend hours in darkness and costly and time-consuming biochemical assays.

Such methods can remove many social factors that could affect mood and circadian timekeeping. However, it is unclear how being removed from society could affect mood. Additionally, such biochemical assays cannot scale to understand population levels interactions between sleep, circadian rhythms and mood.

In the real-world, individuals encounter a myriad of daily social challenges that are absent in laboratory settings. Due to the numerous confounding factors, it remains uncertain whether a significant relationship between circadian rhythm, time awake, and mood can be established in everyday life.

Investigations into peripheral rhythms have shown a circadian rhythm of heart rate and heart rate variability [ 28 — 33 ]. Data collection in these studies required either a sleep laboratory or portable electrocardiograms placed with clinical supervision.

Advances in wearable technology have made continuous heart rate, sleep stage, and activity monitoring possible for the general population. Algorithms created by Bowman et al.

have further allowed extraction of circadian phase from wearable data without the need for invasive temperature or laboratory monitoring [ 34 ].

The ability to measure circadian rhythm noninvasively has provided an opportunity to investigate the relationship between the biological clock and mood amidst the unpredictable and tumultuous nature of daily life. Here, we study the relationship between circadian timekeeping, sleep and mood using this new mobile and wearable technology.

A key question is whether historical laboratory findings in clinical settings would generalize to real-world settings. This technology could help in the treatment of mood; if mood is unduly lowered by sleep deprivation or circadian timekeeping, simple circadian or sleep interventions would be appropriate.

It could also indicate abnormal mood patterns, even when sleep and circadian rhythms are accounted for, to inform psychiatric diagnosis, suicide prediction, and treatment decisions. The Intern Health Study is a multicenter study across the United States involving first year physicians [ 35 ].

Physician interns were recruited for this study through emails that were sent to both their medical school and upcoming place of internship. Recruitment lasted from April through June prior to the start of their internship. Interns recruited in years and were included in this study.

Participants downloaded a mobile application which would prompt them with daily ecological momentary assessments [ 37 ]. Users were sent a daily push notification at a user-specified time between 5pm and 10pm reminding them to complete the once daily assessment.

While users received a push notification at a designated time, they had the ability to complete the survey at any point in the day. S1 Fig displays the mood scale. In addition, minute by minute sleep, heart rate, and step counts were collected while they wore the provided Fitbit device [ 38 , 39 ].

A total of , surveys from 4, participants were collected. Of those, survey scores that did not contain at least 24 hours of abutting wearable data were removed.

Participants were included in the study if they had at least one survey score with wearable data. A total of , survey scores met these criteria across 2, participants. Demographic data of age, sex, and ethnicity were collected by self-reporting on enrollment and displayed in Table 1 for these participants.

The number of participants analyzed in this study was 2, Baseline characteristic proportions are rounded to nearest percentage. This raw data was automatically uploaded from participant Fitbit devices to a secure server at regular intervals during collection.

The data was analyzed post-hoc on these servers after collection was completed using MATLAB [ 35 ] and Python [ 40 ] scripts. This study was approved by the University of Michigan IRB and all subjects were provided informed consent after receiving a complete description of the study.

Bowman et. developed a model of heart rate informed by a comprehensive literature review that depicts heart rate as the combination of influences from physical activity, a hour rhythm, and a standardized model of error [ 34 ].

The model of heart rate at time t HR t is governed by six physiological parameters—basal heart rate a , amplitude of a hour circadian oscillation in heart rate b , time of the circadian heart rate minimum c , increase in heart rate per step d , and an autoregressive error function ε t.

The error function accounts for both the inaccuracies of the wearable device [ 41 ] and external factors such as cortisol and other hormones [ 42 ] which are driven by stimuli such as light, sleep cycles, stress levels, and meals [ 43 — 47 ].

To utilize Bowman et. The model was then fit using Goodman and Weare affine invariant Markov chain Monte Carlo algorithm [ 48 ] to two wake-sleep intervals at a time.

Circadian phase was then computed as the angle between the heart rate minimum and the time of survey completion. It is measured from 0° to ° with 0° representing the heart rate minimum. On someone habituated to normal day-night conditions entrained this minimum occurs at the midpoint of sleep.

A total of , survey scores were paired from 2, participants. For each score, a standardized mood z score was calculated.

To assess if mood changes based on circadian phase and time awake, linear mixed modeling was applied. Linear mixed modeling was chosen given the unbalanced study design and the serial mood measurements. Subjects were considered a random effect with fixed slope and random intercept.

Given the circular nature of circadian phase, e. For each subject, mood was then modeled as the sum of the fixed effects of circadian phase, time awake, age, sex, and ethnicity. Where i represents each survey nested to subject j.

γ is the coefficient for each fixed effect of the model with u denoting the random component of the intercept.

Using R packages lme4 and lmerTest [ 49 , 50 ], coefficients and their p-values were calculated. The model was compared to one without the fixed effects of age, sex, and ethnicity.

Using the R anova function, the fit of the model including demographic data was compared against one without. To help understand the nonlinear relationship of time awake and circadian phase on mood, survey scores were broken into 4 strata.

Strata were set at less than 6 hours, 6 to 12 hours, 12 to 18 hours, and 18 to 24 hours of time awake. Each stratum was then fit with its own model, however, now without the fixed effect of time awake. where i represents each survey nested to subject j. The coefficients and the associated p-values were calculated in each stratum.

Using only the fixed effect components of each model, we calculated the corresponding function amplitudes, minimums, and intercepts. We analyzed a total of , survey scores from 2, participants.

A comprehensive demographic breakdown is provided in Table 1 for further illustration. Each subject completed an average of A histogram of the number of surveys per participant is displayed in Fig 1. The mean of the median time difference between successive surveys per participant was 2.

Raw mood survey scores ranged from 1 to 10 with an overall mean of 7. Individual average mood scores spanned from 1. Average participant standardized mood scores were plotted against circadian phase in Fig 2A and against time awake in Fig 2B.

A Each mood score was paired with the circadian phase at time of submission. Bin edges were computed every 30° and the average standardized mood survey score was plotted against the midpoint of each bin. The median time of survey completion and interquartile range was calculated for each circadian phase bin and plotted beneath the x-axis.

Bin sizes were as follows: °°: , 15°°: , 45°°: , 75°°: , °°: , °°: , °°: , °°: , °°: , °°: , °°: , °°: B Each mood score was paired with the corresponding number of hours the participant has been awake at survey submission.

Bin edges were computed every 2 hours, and the average standardized mood survey score was plotted against the midpoint of each bin. Bin sizes were as follows: 0—2 hours: , 2—4 hours: , 4—6 hours: , 6—8 hours, 8—10 hours: , 10—12 hours: , 12—14 hours: , 14—16 hours: , 16—18 hours: , 18—20 hours: , 20—22 hours: , 22—24 hours: This model tests if participant mood scores are associated with circadian phase and time awake.

The association between circadian phase and mood was rhythmic. In the fitted model, mood peaked at °, or approximately 5 pm on an entrained clock, and a nadir at 18°, or approximately 5 am. A significant association was also found between time awake and mood, where mood deteriorates with increasing time awake.

Mood scores were subsequently split into strata: 0—6, 6—12, 12—18, and 18—24 hours of time awake at survey completion. The strata had , , , and survey results respectively.

Fig 3 displays each fitted model plotted with the corresponding raw data binned by circadian phase. Each category was binned by circadian phase and edges computed using the Freedman Diaconis Estimator [ 70 ].

Bin resolution and average number of samples per bin for each graph are as follows: 6. The average mood z score for each bin was plotted against the bin midpoint. Linear mixed models were fit to each category.

Predictions using the fixed effects of each model were plotted. The median time of survey completion was calculated for each circadian phase bin. For 0—6 hours awake the median time of survey completion ranged from pm to pm, 6—12 hours ranged from pm to pm, 12—18 hours ranged from pm to pm, and 18—24 hours ranged from pm to pm.

The average mood standardized z scores, represented by model intercepts, were near 0 for the first two strata In the first three strata, the nadir of mood shifted later °, 3°, 16° respectively with increasing time awake.

A linear mixed model was fit to 4 different groups of survey data: 0—6 hours, 6—12 hours, 12—18 hours, and 18—24 hours of wake time. This model tests if participant mood scores are associated with circadian phase without assuming a linear relationship with time awake. Rigorous measures of circadian rhythms were previously restricted to laboratory settings.

These measures included tracking core body temperature, melatonin levels, or cortisol levels [ 27 ]. Collecting this data required frequent rectal temperature measurements or consecutive blood draws.

To obtain the serial measurements and avoid external environmental confounders, past studies often required participants to be confined in conditions far from what would be experienced in the natural environment.

These conditions would reduce biases by controlling environmental cues such as participant caloric intake, meal timing, and ambient lighting which all can affect these measures [ 45 , 51 , 52 ]. Outside the laboratory, measuring temperature trends is difficult to implement as one needs to measure core body temperature throughout the day and subsequently fit an individualized oscillatory model to the collected data [ 53 ].

Using cortisol to determine circadian rhythm poses similar constraints as temperature except frequent blood draws would be needed rather than core body temperatures [ 54 ].

Dim-light melatonin onset DLMO has been the most promising measurement of circadian rhythm that may be extended outside the laboratory setting. In this procedure, several consecutive saliva sample can be used to determine circadian rhythm.

Amplitude changes and phase shifts in temperature, cortisol, and melatonin have been utilized experimentally as markers of affective illness and treatment response [ 18 , 57 , 58 ]. However, the application in clinical practice has been limited due to both the inconvenience of these measurement tools and the concern that rhythmic changes can not accurately be measured in uncontrolled settings [ 59 ].

Chronotherapies have therefore been limited to broad based interventions that do not require knowledge of an individualized circadian rhythm such as total and partial sleep deprivation [ 60 ], interpersonal and social rhythms therapy for bipolar disorder which regularizes daily routines [ 61 ], and nighttime melatonin for insomnia [ 62 ].

In this study we analyzed minute by minute step, heart rate, and sleep data from 2, medical interns across a total of , days collected using Fitbits. From this real-world or non-laboratory data, we were able to calculate the daily circadian rhythm for each participant, information that previously would have required laboratory-based minute by minute rectal temperature monitoring or daily intravenous blood draws.

Despite using these new noninvasive measures and the uncontrolled and chaotic environment of participants, we extend historic laboratory findings that mood is dependent on cumulative wake time and circadian phase in a non-linear way.

We also show that measuring circadian rhythms via heart rate through wearables, or laboratory rectal temperature measurements yields similar results.

More work needs to better delineate these and other circadian markers. Our study demonstrates a clear circadian variation in mood, with peak mood occurring in the evening and troughing in the early morning.

As waking hours accumulate, there is a significant decrease in mood. There were several limitations to our study design. First, the mixed effects model serves as a generalized model of mood in medical interns. On an individual basis, the model only accounts for the differing variance and average mood of an individual.

The inter-individual variation of mood is more complex than this and is dependent on factors such as social dynamics, schedules, and temperaments [ 63 — 65 ]. Third, no validated emotional rating scales such as the Depression Anxiety Stress Scale or clinical screening tools were utilized in our analysis.

Emotional screening tools could help identify intra participant outliers and clinical screening tools would help account for potential confounding effects of affective and anxiety disorders.

Lastly, to aid in the simplicity of our model, we left out factors such as sleep time and variability which have been recently shown to affect mood [ 66 ]. Despite these limitations, the results of our study highlight the critical role played by the circadian pacemaker in regulating mood, even during the challenging and unpredictable nature of medical internship.

More so, our research shows that measuring the circadian influence on mood can be achieved noninvasively, without the need for stringent experimental conditions.

These findings have important implications in evaluating for psychopathology. This raises the question of whether multiple assessments throughout various times of day may be beneficial and highlights the potential for time-of-day biases in existing literature. The ability to measure circadian rhythm using wearable holds significant clinical promise.

Psychiatric patients can be provided with a Fitbit and their circadian rhythm tracked. Treating clinicians can monitor for circadian phase shifts as an indicator of the onset of a depressive or manic episode [ 67 , 68 ] and proactively begin treatment.

Furthermore, treatment response can be gauged by circadian re-alignment [ 24 ] in addition to more subjective patient reports currently utilized [ 69 ].

Further work can integrate our general model of mood into more personalized mathematical models of mood. Clinicians could use such a model to anticipate potential mood shifts and devise intervention strategies proactively. With the combination of technology and clinical insights, such a model can pave the way for a new era in mental health care, one that is predictive, personalized, and preemptive in its approach.

Article Authors Metrics Comments Media Coverage Reader Comments Figures. Abstract The interplay between circadian rhythms, time awake, and mood remains poorly understood in the real-world.

Author summary Our body has an internal clock that controls much of our physiology. Introduction Internal hour circadian biological clocks regulate many physiological processes in an organism such as metabolism, hormone secretion, and the sleep-wake cycle.

Methods Participants The Intern Health Study is a multicenter study across the United States involving first year physicians [ 35 ].

Download: PPT. Statistical analysis Bowman et. Results We analyzed a total of , survey scores from 2, participants. Fig 1. Distribution of Surveys Completed per Participant, showcasing the number of surveys each participant completed that were used in the statistical analysis of this study.

Table 2. Coefficients Fit to the Aggregate Linear Mixed Effects Model. Fig 3. Variation in Mood with Circadian Phase Stratified by Time Awake. Discussion Rigorous measures of circadian rhythms were previously restricted to laboratory settings.

Supporting information. S1 Fig. Mood survey prompt. s DOCX. References 1. Hastings MH, Reddy AB, Maywood ES. A clockwork web: circadian timing in brain and periphery, in health and disease.

Nat Rev Neurosci. Shift work results in a sleep disorder when your nighttime work shifts affect your ability to fall asleep and stay asleep, causing you to have excessive sleepiness during the day that in turn results in distress and affects your ability to function normally.

Nurses with shift work disorder have increased anxiety scores on questionnaires. In a study on jet lag , in which travel changes the time of the external environment so that it is no longer synchronized with the internal clock and disrupts sleep, travelers had elevated anxiety and depression scores.

In seasonal affective disorder, people feel down and depressed in the winter months. Researchers believe this is due to changes in circadian rhythms as a result of seasonal changes in the length of daylight.

People with seasonal affective disorder feel better using artificial morning light to realign their circadian rhythm with their sleep-wake cycle. There is no way to change your circadian type since it is genetically determined, though there is some natural change that occurs during your lifespan.

For example, our circadian sleep phase tends to shift later during adolescence more owls and advances earlier as we age more like the lark.

If you find that your circadian sleep phase is out of sync with your desired schedule, you can either shift your social life to match your circadian rhythm, or try to shift your circadian rhythm to match your social life.

It may be easier to try to shift your work and social life to your circadian rhythm: an example would be a person who has a delayed circadian rhythm and likes to sleep late and wake up late switching from a job with a 7 AM start time to a job which allows him or her to start working later — around 10 AM.

The other option would be talking to a sleep physician and doing ongoing work to try to shift your circadian rhythm to match your work and social life to an earlier wakeup time.

Exposure to light in the morning helps synchronize the clock. Exposure to bright light at night, including bright artificial lights and screen time on laptops, tablets, and phones, can cause disruption in circadian rhythm and may contribute to worsening mood and negative consequences for health.

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Studies are needed to examine the most effective circadian times for exercising and how much exercise is needed for shift workers to maintain their metabolic health.

Studies should examine whether obesity, independent of sleep disorders, causes poor sleep and should identify the underlying mechanisms. Additional investigations are needed into how diet content and quality affect circadian rhythmicity and sleep health.

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Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation during a repeating pattern of insufficient sleep and weekend recovery sleep. Sleep restriction leads to increased activation of brain regions sensitive to food stimuli.

The findings of this study link restricted sleep and susceptibility to food stimuli and are consistent with the notion that reduced sleep could lead to an increased propensity to overeat. Benedict, C.

Greer, S. The impact of sleep deprivation on food desire in the human brain. Sleep restriction increases the neuronal response to unhealthy food in normal-weight individuals. Dashti, H. Short sleep duration and dietary intake: epidemiologic evidence, mechanisms, and health implications.

Short sleep duration is associated with greater alcohol consumption in adults. Appetite 59 , — Sampasa-Kanyinga, H. Sleep duration and consumption of sugar-sweetened beverages and energy drinks among adolescents. Nutrition 48 , 77—81 Effects of experimental sleep restriction on weight gain, caloric intake, and meal timing in healthy adults.

Sleep 36 , — This is the largest experimental study to date to show that sleep restriction promotes weight gain in healthy adults. Hanlon, E.

Sleep restriction enhances the daily rhythm of circulating levels of endocannabinoid 2-arachidonoylglycerol. Sleep 39 , — De Luca, M. Cannabinoid facilitation of behavioral and biochemical hedonic taste responses. Neuropharmacology 63 , — Kirkham, T.

Endocannabinoid levels in rat limbic forebrain and hypothalamus in relation to fasting, feeding and satiation: stimulation of eating by 2-arachidonoyl glycerol. Melanson, E. Daytime bright light exposure, metabolism, and individual differences in wake and sleep energy expenditure during circadian entrainment and misalignment.

Sleep Circadian Rhythm. Phenotypic vulnerability of energy balance responses to sleep loss in healthy adults. McNeil, J. Increased energy intake following sleep restriction in men and women: a one-size-fits-all conclusion? Obesity 25 , — Dennis, L.

Phenotypic stability of energy balance responses to experimental total sleep deprivation and sleep restriction in healthy adults.

Nutrients 8 , E The role of sleep duration in the regulation of energy balance: effects on energy intakes and expenditure. Gender differences in the association between sleep duration and body composition: the Cardia Study. Yeom, H.

Sex differences in the influence of sleep on body mass index and risk of metabolic syndrome in middle-aged adults. Healthcare 8 , E Fan, Y. Gender differences in the association between sleep duration and body mass index, percentage of body fat and visceral fat area among chinese adults: a cross-sectional study.

BMC Endocr. Mercy, U. Sex differences in the association between short sleep duration and obesity among US adults: findings from NHANES, Circadian timing of food intake contributes to weight gain.

Obesity 17 , This study focused on the role of the circadian phase of food consumption and showed that nocturnal mice fed a high-fat diet only during the h light phase gained more weight than mice fed only during the h dark phase. Gill, S. A smartphone app reveals erratic diurnal eating patterns in humans that can be modulated for health benefits.

Cell Metab. Baron, K. Contribution of evening macronutrient intake to total caloric intake and body mass index. Appetite 60 , — Garaulet, M. Timing of food intake predicts weight loss effectiveness. Obesity 23 , Impact of circadian misalignment on energy metabolism during simulated nightshift work.

Later circadian timing of food intake is associated with increased body fat. Insufficient sleep undermines dietary efforts to reduce adiposity. This study shows that lack of sufficient sleep might compromise the efficacy of typical dietary interventions for weight loss and related metabolic risk reduction.

Change in sleep duration and visceral fat accumulation over 6 years in adults. Obesity 22 , E9—E12 Creasy, S. Higher amounts of sedentary time are associated with short sleep duration and poor sleep quality in postmenopausal women.

Sleep 42 , zsz Thosar, S. Shorter sleep predicts longer subsequent day sedentary duration in healthy midlife adults, but not in those with sleep apnea. Living a healthy, active lifestyle that promotes proper rest will help you maintain this important component of your body. See a doctor if you experience prolonged difficulties sleeping or extreme fatigue during the day to find out how you can realign with your circadian rhythm and get proper rest.

Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available. Sleep deprivation not only affects how you feel the next day, it can also impact your entire body. Here's all you need to know. Getting quality sleep is one of the best things you can do for your health.

Here are 10 evidence-based reasons why good sleep is important. You can ensure this happens by going to bed and waking up….

Researchers have found that this sleep disorder called idiopathic hypersomnia may actually be much more common than previously realized.

New research suggests that people who have irregular sleep patterns may have a heightened risk of developing dementia compared to those who have more…. The end of daylight saving time can result in numerous health changes, most notably disruptions in sleep and mood.

A Quiz for Teens Are You a Workaholic? How Well Do You Sleep? Health Conditions Discover Plan Connect. Everything to Know About Your Circadian Rhythm. Medically reviewed by Nick Villalobos, MD — By Natalie Silver — Updated on March 30, How it works In babies In teens In adults Out of sync How to reset Sleep disorders Health effects When to talk with a doctor Takeaway What are circadian rhythms?

How do circadian rhythms work? Circadian rhythm in babies. Circadian rhythm in teens. Circadian rhythm in adults. What factors can change circadian rhythms? How to reset your circadian rhythm. Sleep disorders. How do circadian rhythms affect health? When to contact a doctor.

The bottom line. How we reviewed this article: Sources. Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations.

We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy. Mar 30, Written By Natalie Silver.

Jul 13, Written By Natalie Silver. Share this article. Read this next. Exposure to bright light at night, including bright artificial lights and screen time on laptops, tablets, and phones, can cause disruption in circadian rhythm and may contribute to worsening mood and negative consequences for health.

Lawrence Epstein, MD , Contributor. Syed Moin Hassan, MD , Contributor. As a service to our readers, Harvard Health Publishing provides access to our library of archived content.

Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician. When you wake up in the morning, are you refreshed and ready to go, or groggy and grumpy?

For many people, the second scenario is all too common. Improving Sleep: A guide to a good night's rest describes the latest in sleep research, including information about the numerous health conditions and medications that can interfere with normal sleep, as well as prescription and over-the-counter medications used to treat sleep disorders.

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How well do you score on brain health? Shining light on night blindness.

A recent study suggested that the night-owl type might have a greater predisposition to psychological disturbances. The authors found that the different circadian types were likely to have different coping styles to emotional stressors, and the ones adopted by the morning larks seemed to result in better outcomes and fewer psychological problems.

Most of the evidence on the relationship between mood problems and circadian rhythm comes from studies of shift workers, whose sleep periods are out of sync with their circadian rhythm.

Multiple studies show an increased prevalence of depression in night-shift workers. Conversely, circadian rhythm disturbances are common in people with depression, who often have changes in the pattern of their sleep, their hormone rhythms, and body temperature rhythms.

Symptoms of depression may also have a circadian rhythm, as some people experience more severe symptoms in the morning. Many successful treatments of depression, including bright light therapy, wake therapy , and interpersonal and social rhythm therapy , also directly affect circadian rhythms.

For the impact of circadian rhythm on the occurrence and treatment of depression related to bipolar disorder, please see this blog post on light therapy for bipolar disorder. Misalignment of the circadian rhythm may also provoke anxiety. Shift work results in a sleep disorder when your nighttime work shifts affect your ability to fall asleep and stay asleep, causing you to have excessive sleepiness during the day that in turn results in distress and affects your ability to function normally.

Nurses with shift work disorder have increased anxiety scores on questionnaires. In a study on jet lag , in which travel changes the time of the external environment so that it is no longer synchronized with the internal clock and disrupts sleep, travelers had elevated anxiety and depression scores.

In seasonal affective disorder, people feel down and depressed in the winter months. Researchers believe this is due to changes in circadian rhythms as a result of seasonal changes in the length of daylight. People with seasonal affective disorder feel better using artificial morning light to realign their circadian rhythm with their sleep-wake cycle.

There is no way to change your circadian type since it is genetically determined, though there is some natural change that occurs during your lifespan. For example, our circadian sleep phase tends to shift later during adolescence more owls and advances earlier as we age more like the lark.

If you find that your circadian sleep phase is out of sync with your desired schedule, you can either shift your social life to match your circadian rhythm, or try to shift your circadian rhythm to match your social life.

It may be easier to try to shift your work and social life to your circadian rhythm: an example would be a person who has a delayed circadian rhythm and likes to sleep late and wake up late switching from a job with a 7 AM start time to a job which allows him or her to start working later — around 10 AM.

The other option would be talking to a sleep physician and doing ongoing work to try to shift your circadian rhythm to match your work and social life to an earlier wakeup time.

Exposure to light in the morning helps synchronize the clock. Exposure to bright light at night, including bright artificial lights and screen time on laptops, tablets, and phones, can cause disruption in circadian rhythm and may contribute to worsening mood and negative consequences for health.

Lawrence Epstein, MD , Contributor. Syed Moin Hassan, MD , Contributor. As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Sleep is involved in regulation of blood pressure , cholesterol and blood sugar levels.

Sleep can also impact our diet and physical activity levels. We also experience fatigue and sleepiness during the day which can reduce our motivation to exercise and impair our performance when we do exercise. Sleep deprivation is associated with increased risk of cardiometabolic conditions including obesity , hypercholesterolaemia high cholesterol levels , diabetes and hypertension.

Having short sleep durations, particularly less than 7 hours per night is associated with increased risk of cardiovascular disease morbidity and mortality. Sleep and the immune system are closely connected.

During sleep there is an increase in important proteins involved in immune function and inflammation e. Immune regulation during sleep may help with recovery and repair of wounds or fight off an infection.

Consistent sleep can strengthen the immune response supporting a well-balanced immune defence system. This means that good sleep supports a more efficient response to vaccines and less server allergic reactions.

Long-term sleep deprivation can negatively impact your immune response can enhance susceptibility to infections and a reduced immune response to vaccination. Sleep deprivation is thought to lead to a persistent low-grade inflammation, and also produce immunodeficiency, which both have detrimental effects on health.

When you feel that you are not getting the sleep that you need, there are some things that you can do to improve your sleep. For further healthy sleep recommendations refer to the Sleep Health Foundation External Link website.

This page has been produced in consultation with and approved by:. Content on this website is provided for information purposes only. Information about a therapy, service, product or treatment does not in any way endorse or support such therapy, service, product or treatment and is not intended to replace advice from your doctor or other registered health professional.

The information and materials contained on this website are not intended to constitute a comprehensive guide concerning all aspects of the therapy, product or treatment described on the website. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions and to ascertain whether the particular therapy, service, product or treatment described on the website is suitable in their circumstances.

The gold standard protocol for assessing the circadian contribution to a physiological or behavioural outcome is the constant routine.

The constant routine protocol controls for factors that might affect the outcome of interest by eliminating, holding constant or equally distributing such factors across at least one h circadian cycle. In this protocol, participants are maintained in constant environmental conditions of dim light and thermoneutral ambient temperature.

Energy intake can be equally distributed in small hourly snacks or constantly maintained using a continuous infusion. Canonical circadian markers of biological time, such as melatonin, cortisol or core body temperature, are typically measured to facilitate the interpretation of findings; that is, how outcomes of interest vary relative to central circadian rhythms.

Circadian rhythms in the outcomes of interest can then be compared with patterns observed in other non-constant conditions, for example, whether they are influenced by factors such as wakefulness—sleep, energy intake—fasting, activity—inactivity or light—dark cycles.

Understanding the distinct contributions of circadian versus diurnal rhythms in the regulation of physiological processes could inform how these mechanisms are dysregulated as well as how they can be targeted for obesity prevention and treatment 67 , 86 , To examine the role of sleep and circadian disruption in obesity development, this section primarily focuses on findings from studies that examined h patterns in energy expenditure and the appetite-regulating hormones ghrelin, leptin and peptide-YY PYY that feed back to energy intake regulatory centres in the hypothalamus 88 , 89 , Compared with fasting values, h patterns in these parameters are more relevant to understanding weight gain and metabolic dysregulation and have been repeatedly studied under conditions of insufficient sleep and circadian misalignment Box 2.

We also briefly examine the limited existing data on the effect of insufficient sleep and circadian misalignment on the h or daytime patterns in the gut hormones glucagon-like peptide 1 GLP1 and pancreatic polypeptide.

Other potentially relevant hormones, such as gastric inhibitory polypeptide, cholecystokinin and amylin, are not discussed here as data are not currently available. The h pattern of energy expenditure has been measured under controlled energy intake, controlled activity and bed rest conditions Fig.

Increases in energy expenditure occur in response to meals referred to as the thermic effect of food or diet-induced thermogenesis and sleep induces a decrease in energy expenditure that is absent when wakefulness is maintained.

Under constant routine conditions, the circadian variation in energy expenditure decreases across the biological day and increases across the biological night Fig.

However, the circadian rhythm in energy expenditure is of much smaller magnitude than the sleep—wake modulation of energy expenditure. In addition, wakefulness—sleep, energy intake—fasting and circadian rhythms are observed in the thermic effects of energy intake and in levels of hunger in healthy young adults and healthy middle-aged aged 38—69 years adults 77 , 80 , Sleep and circadian rhythms influence the levels of appetite hormones Figs.

In healthy adults, a h pattern occurs in circulating levels of ghrelin under conditions of energy balance, such that ghrelin levels increase between meals, decrease after meals, increase before and during the first few hours of sleep, and decrease during the second half of the sleep episode 76 , 84 Fig.

Under constant routine conditions, the circadian rhythm of ghrelin increases across the biological daytime and decreases across the biological night 80 Fig. Furthermore, hypocaloric diets that induce moderate weight loss are not necessarily associated with elevated ghrelin Together, these reports suggest that increased levels of ghrelin are not required to increase appetite.

Leptin is produced by white adipocytes and is a hormone that decreases appetite. Circulating levels of leptin are positively associated with adiposity and are considered representative of energy storage.

In healthy adults, a h pattern of levels of leptin can be observed under conditions of energy balance, with relatively lower levels most of the waking day and higher levels at night 76 , 94 Fig.

Like ghrelin, leptin levels peak in the first few hours of the habitual sleep episode and decrease across the remainder of the sleep episode.

Under constant routine conditions, a very small amplitude circadian rhythm occurs in leptin, which increases across the biological daytime and decreases across the biological night 80 Fig. PYY is produced by L cells of the small intestine and is a hormone that decreases appetite.

In healthy adults, the h pattern of circulating levels of PYY under conditions of energy balance shows higher levels during the daytime and lower levels at night 76 Fig.

Under constant routine conditions, the circadian rhythm of PYY shows decreased levels across the biological daytime and increased levels across the biological night 80 Fig.

Thus, h patterns of the appetite hormones ghrelin, leptin and PYY are modulated by circadian rhythms and by wakefulness—sleep, activity—inactivity and energy intake—fasting processes. GLP1 is produced by L cells of the intestine and is a hormone that reduces appetite.

In healthy adults, the h pattern of GLP1 shows that higher levels of GLP1 are observed in the afternoon after food intake than at other times Whether a circadian rhythm of GLP1 occurs is unknown.

Pancreatic polypeptide is produced by PP cells of the pancreas and is a hormone that reduces appetite In healthy adults, the h pattern of circulating levels of pancreatic polypeptide shows higher levels during the daytime with food intake and lower levels at night 97 , 98 , Whether a circadian rhythm of pancreatic polypeptide occurs is unknown.

Under a h fast in healthy adults, a diurnal rhythm was observed, with highest levels occurring during the early evening and night and low levels in the second half of the night Such increases in h energy expenditure occur regardless of whether energy intake is maintained at levels that are sufficient for energy balance during adequate sleep conditions or whether energy intake is permitted ad libitum.

Furthermore, increased energy expenditure during insufficient sleep occurs rapidly and is sustained across many days in both healthy young men and women In lean individuals, measuring energy expenditure using doubly labelled water a less sensitive and more variable technique than whole-room calorimeter techniques does not detect these small but physiologically meaningful changes in response to insufficient sleep , However, the doubly labelled water technique can be more readily employed in free-living studies and when large changes in energy balance are predicted.

When energy intake is controlled during insufficient sleep and not increased to account for the increased energy expenditure, a negative energy balance occurs. This negative energy balance and changes in the levels of appetite hormones namely increased ghrelin and reduced leptin are associated with increased hunger ratings across days of insufficient sleep in healthy populations 94 , , , ; however, not all appetite hormones for example, T 3 , T 4 or adiponectin were altered in these studies.

Furthermore, PYY has not been assessed under insufficient sleep with controlled energy intake conditions. Energy intake during adequate habitual sleep in healthy lean adults was isocaloric; thus, the h pattern of leptin, ghrelin and PYY during adequate sleep was under assumed conditions of energy balance 76 , By contrast, during insufficient sleep in healthy lean adults, if energy intake is not increased to meet the increased energy expenditure during insufficient sleep, the h pattern of these same appetite hormones can be assumed to reflect conditions of negative energy balance Fig.

Findings on the effect of insufficient sleep on the h pattern in gut hormones associated with satiety, such as GLP1 and pancreatic polypeptide, are mixed and potentially dependent on sex or context.

For example, afternoon blood levels of GLP1 were reduced during experimental sleep restriction under conditions of controlled energy intake negative energy balance in young women compared with adequate sleep , whereas circulating levels of GLP1 across the h day did not notably change under the same conditions in young men However, afternoon levels of GLP1 were decreased during sleep fragmentation in young men tested under energy balance conditions Of note, in young men, circulating levels of pancreatic polypeptide across the h day during experimental sleep restriction did not notably change but after-dinner levels were reduced compared with adequate sleep conditions When energy intake is uncontrolled in lean adults during periods of insufficient sleep, an increase in energy intake occurs that is larger than the increase in energy expenditure, which results in a positive h energy balance and weight gain 76 Fig.

Importantly, this excess in h energy intake in healthy adults occurs 5 , , , even with changes in appetite hormones that should reduce levels of hunger reduced ghrelin, increased leptin and increased PYY 76 , Although changes in ghrelin, leptin and PYY might initially promote energy intake during acute sleep restriction, mechanisms other than changes in these appetite hormones are probably involved in the continued excess energy intake and obesogenic effects of chronic insufficient sleep 76 , During experimental conditions of insufficient sleep in healthy adults, when energy intake is designed to meet the energy balance demands for a typical day with adequate sleep at baseline, there is an increase in energy expenditure due to the increased wakefulness and a negative energy balance that is, energy expended is greater than energy consumed.

Concurrently, hunger will increase owing to changes in appetite hormones. However, if sleep is restricted and food is provided ad libitum, participants will eat far more calories than expended during the additional wakefulness despite changes in appetite hormones that would promote satiety.

These extra calories put participants into a positive energy balance and weight gain if maintained over time. Moreover, the increase in calories occurs predominately in after-dinner snacks, a time in which the energetic response to energy intake is decreased, further promoting a positive energy balance and weight gain.

Potential explanations for increased energy intake during sleep restriction beyond appetite hormones include increased energy expenditure that does not seem to adapt to continued insufficient sleep and the activation of brain regions associated with changes in hunger and food choices. For example, healthy volunteers underwent restricted sleep in a laboratory setting under conditions of either controlled energy intake or ad libitum energy intake.

Brain areas associated with reward following sleep restriction include the putamen, nucleus accumbens, thalamus, insula and prefrontal cortex. Behavioural observations support these brain imaging findings as insufficient sleep is associated with poor dietary choices and altered dietary patterns Specifically, insufficient sleep was reported to increase the consumption of high-carbohydrate foods, fats, sugar-sweetened beverages and alcohol , , , , in addition to inducing an increased drive for hedonic eating.

One potential mechanism for an elevated drive for hedonic eating during insufficient sleep is increased activation of the endocannabinoid system , an important part of the hedonic food pathway , Large inter-individual and sex differences are observed in the amount of increased energy intake and energy expenditure occurring during insufficient sleep , , , , , In general, inter-individual differences are consistent and robust Furthermore, men consistently show higher energy intake, energy expenditure and larger positive energy balance than women during insufficient sleep 76 , Such inter-individual differences contribute to inconsistencies in some findings.

For example, in highly controlled crossover research designs, where each participant serves as their own control, robust and meaningful differences in energy intake and expenditure are seen between conditions of insufficient sleep and of adequate sleep However, inter-individual designs are limited by large variability between individuals Another important consideration in studies of insufficient sleep is the timing of food intake as when we eat has been demonstrated as an important determinant of metabolic health and disease risk , , , In many individuals, insufficient sleep changes the biological timing of food intake.

For example, insufficient sleep increases food intake later in the day 76 , , and later timing of food intake closer to the biological night is associated with a reduced thermic effect of food the energetic response to a meal , and with weight gain and obesity Of note, people who consume a larger proportion of their food intake later in the day show reduced weight loss during caloric restriction compared with those who eat a larger proportion of their food intake earlier in the day In adults with overweight, weight loss in response to caloric restriction under conditions of insufficient sleep leads to loss of muscle mass in lieu of adipose tissue mass compared with caloric restriction under conditions of adequate sleep Importantly, under experimental insufficient sleep conditions, switching to an adequate sleep schedule reduces food intake in lean adults 75 , 76 , and leads to weight loss over time in adults with obesity Whether insufficient sleep reduces physical activity — an effect that would further contribute to a positive energy balance and weight gain — is unclear.

Some individuals who are sleep restricted move less than those who have adequate sleep owing to increased tiredness, whereas others do not change their activity behaviours, thereby reflecting large inter-individual variability Decreased sleep duration in middle-aged adults was associated with increased sedentary activity such as screen time , , including next-day sedentary activity Such increased sedentary time could contribute to reduced energy expenditure and increased risk for obesity and metabolic dysfunction.

Many aspects of h energy metabolism are influenced by circadian processes. Circadian misalignment, from a metabolic perspective, is defined as energy intake, activity and wakefulness occurring during the biological night 73 , , , Box 2.

Circadian misalignment also disturbs sleep and thus insufficient sleep probably contributes to the alterations in metabolism observed during circadian misalignment.

Furthermore, sleeping during the biological daytime probably also contributes to alterations in h rhythms of metabolites and proteins 65 , Moreover, internal circadian desynchrony can occur between the central circadian clock and peripheral clocks when animals such as mice are awake, active and consuming energy during their inactive phase , although data for such internal circadian desynchrony in humans is limited.

Examination of the human proteome during a simulated shift-work protocol in healthy lean individuals has provided some initial mechanistic insight into these changes. For example, decreased levels of fibroblast growth factor 19 a protein that increases energy expenditure were found to be associated with a reduction in energy expenditure Working during the biological night is also associated with increased rates of obesity and related metabolic diseases , However, findings regarding energy intake during circadian misalignment induced by shift work are mixed.

For example, a meta-analysis published in found no difference in energy intake between shift workers and non-shift workers Another mechanism by which circadian misalignment could increase obesity risk is by alterations in food intake. For example, food choices made during circadian misalignment might be less healthy than those made during day work conditions for example, less vegetables and more sweets and saturated fats ; this effect has been observed in both lean individuals and individuals with overweight or obesity who are shift workers , Circadian misalignment could also contribute to weight gain by inducing a reduction in physical activity in lean men and women If sustained, reduced h energy expenditure during circadian misalignment, even without a change in energy intake, could result in weight gain over time.

Indeed, when food intake is restricted to the time of day typically reserved for sleep, mice show higher weight gain than when their food intake is restricted to the time of typical wakefulness. This finding occurs despite similar amounts of caloric intake and activity levels , In conjunction with a circadian variation in the thermic effect of food in humans, these findings indicate that a calorie is not a calorie per se and that the timing of calorie intake has importance for metabolic health.

Under conditions of controlled energy intake or energy balance in healthy adults, circadian misalignment has been reported to have minimal influence on total circulating levels of ghrelin However, under these same conditions, circadian misalignment increases postprandial levels of active acylated ghrelin and reduces levels of leptin , , and PYY Fig.

Findings for hunger during circadian misalignment are mixed, with overall decreases or postprandial increases Moreover, there is a paucity of evidence for changes in h patterns of other gut satiety hormones for example, GLP1 or pancreatic polypeptide in humans during circadian misalignment.

Other factors in addition to appetite hormones might contribute to hunger during circadian misalignment for example, reduced h energy expenditure and reduced circadian drive for hunger; mechanisms are summarized in ref. Additional research is needed to determine whether energy intake is promoted under conditions of circadian misalignment and ad libitum feeding.

Additionally, whether repeated exposures to circadian misalignment for example, during night-shift work and alignment days off chronically alter appetite hormones and energy intake remains to be determined.

Finally, inter-individual differences during circadian misalignment that might be sex dependent should be examined During experimental conditions of circadian misalignment in healthy adults, when energy intake is designed to meet energy balance demands for a typical day with adequate night-time sleep at baseline, there is a decrease in h energy expenditure predominantly due to decreased sleeping energy expenditure.

Hunger might increase owing to changes in appetite hormones, but hunger might also decrease owing to the circadian variation in hunger that shows lower hunger levels during the biological night-time than during the biological daytime.

Alternations in food choices and eating during the biological night might also contribute to weight gain. The combined effects of circadian misalignment and insufficient sleep can be assessed using a modified forced desynchrony protocol, which permits assessment of circadian and sleep—wakefulness-driven processes.

Under presumed negative energy balance conditions in older and younger adults, combined circadian misalignment and insufficient sleep increased blood levels of ghrelin and decreased blood levels of leptin, which should promote energy intake However, decreased levels of PYY were also found, which should reduce energy intake Experimental studies with ad libitum food intake in humans are needed to determine the influence of circadian misalignment on energy intake under these conditions.

Notably, when sleep restriction and circadian misalignment are combined and energy intake is controlled in healthy young adults in a fasted state, circadian timing seems to be more influential on appetite hormone fluctuations than sleep restriction To date, the scientific literature on circadian misalignment and obesity risk has primarily focused on fairly large challenges to the circadian system for example, night-shift work or a h inverted shift in behaviours.

Smaller degrees of misalignment, such as staying up late on weekends social jetlag; commonly found in teenagers , travel across a few time zones, early work start times for example, early morning shift work and insufficient sleep which can lead to morning misalignment or energy intake at night occur more frequently than large degrees of misalignment, and are also associated with adverse metabolic health , For example, every hour a person must shift their internal clock to match the wakefulness period between weekends and weekdays resulted in an increased odds ratio of 1.

Likewise, social jetlag score a higher score is indicative of a greater change in sleep timing between weekdays and weekends is positively associated with obesity in the general population Observations between social jetlag and health have predominately been conducted in cross-sectional designs, which limit the ability to identify mechanisms for observed associations.

However, individuals with an obesity-related chronic illness with a higher social jetlag consume more calorie-dense foods than those with a lower score This finding could be driven by higher circulating levels of ghrelin, as observed in lean adults with social jetlag in free-living conditions Insufficient sleep also leads to morning circadian misalignment melatonin levels are still high in the morning or to energy intake during the biological night.

Such morning circadian misalignment contributes to metabolic dysregulation for example, in blood levels of insulin and glucose in humans 76 , , , , People with obesity typically report reductions in both sleep duration and quality, although research has largely focused on sleep disorders 14 , Although there is no discounting the importance of sleep disorders in this population, little is known about the independent effects of obesity on sleep itself.

In addition, most investigations into the association between obesity and sleep rely on self-reported sleep and cross-sectional study designs. Such research might not adequately control for confounders and is unable to determine the directionality of the association 14 , However, whether poor sleep quality is a factor in this U-shaped association is unclear as sleep fragmentation might not be accounted for in these studies and can be one reason for a longer sleep duration in addition to other underlying comorbidities.

Adults with obesity are also more likely to report sleep problems than people without any comorbidities Excessive daytime sleepiness has also been reported in adults with severe obesity but without obstructive sleep apnoea A variety of physiological factors could affect sleep in a population with obesity.

For example, the location of adipose tissue has a role in the risk of certain sleep disorders. For instance, abdominal obesity and large neck circumference are risk factors for obstructive sleep apnoea Visceral adipose tissue is also well established as a key adipose depot associated with cardiovascular disease risk and T2DM.

Other factors, such as inflammatory markers and gut microbiome , should also be considered for their effects on sleep. Additionally, behavioural factors, such as poor diet and lack of physical activity, are likely to have an impact on sleep.

More research is needed to elucidate the causal mechanisms that link sleep and circadian disruption in order to define the directionality of these associations.

This section briefly discusses some potential strategies that might help individuals to mitigate the adverse effects of sleep and circadian disruption on metabolic health.

These strategies do not currently differ much from traditional sleep hygiene strategies and a detailed discussion of sleep hygiene falls outside the scope of this paper. Further information can be found at the National Sleep Foundation.

Increased levels of physical activity are well known to be related to decreased levels of metabolic syndrome , , Furthermore, a synergistic health effect has been documented of physical inactivity and poor sleep on the development of metabolic syndrome and increased mortality , Findings also suggest that evening physical activity should be discouraged owing to a disturbance of night-time sleep; however, any effect here is likely to be small Of note, whether being physically active helps to prevent or reduce the metabolic health consequences of insufficient sleep and circadian misalignment is unknown.

Healthy eating patterns have been reported to be associated with a decreased risk of developing metabolic syndrome , Healthful diets, especially dietary patterns similar to the Mediterranean diet , have been associated with improved sleep quality in various populations Increased food intake in the evening is associated with weight gain and obesity and reduces the effectiveness of weight loss programmes A study showed that early time-restricted feeding in healthy adults food intake restricted to the early part of the day provides greater benefits for insulin resistance and related metabolic parameters than mid-day time-restricted feeding Bright daytime and dim evening light exposure is important for circadian alignment and could benefit metabolic function , , Further studies are needed to examine whether increasing bright light exposure during the day by going outside more often can improve metabolic health by improving sleep and circadian health In addition, research is needed to determine whether bright light exposure during evening physical activity could affect sleep.

Previous research has shown that a reduction of exposure to blue light at night promotes better sleep quality , , This strategy might also decrease the risk of developing metabolic syndrome by improving fasting plasma levels of glucose and insulin resistance; however, more research in this area is needed Observational studies report that people who drink coffee seem to have a lower risk of obesity, metabolic syndrome and T2DM than people who do not drink coffee , , However, caffeine consumed later in the day is well known to disrupt sleep.

Caffeine might also contribute to late sleep and circadian timing. The magnitude of that delay was nearly half the size of the delay induced by evening exposure to bright light.

Further research is needed to determine whether earlier versus later time of day caffeine consumption has benefits for sleep, circadian alignment and metabolic health. A dose—response meta-analysis on napping found a J-shaped relationship between the length of nap time and the risk of T2DM and metabolic syndrome A short nap when night-time sleep is insufficient could potentially help reduce the adverse effects of a lack of night-time sleep on metabolic health but research in this area is needed.

Alcohol consumption in adults has been found to interact with reduced sleep duration to increase the risk of dysglycaemia Evidence also suggests that smoking is associated with the development of metabolic syndrome whereas smoking cessation seems to reduce this risk People who smoke, particularly at night-time, have longer sleep latency, more awakenings, poorer sleep quality and shorter sleep duration than people who do not smoke 44 , , Not smoking and limiting alcohol consumption, especially near bedtime, are recommended for healthy sleep and optimal metabolic regulation.

Effective treatment strategies are available for sleep problems and sleep and circadian disorders. As noted, sleep and circadian disorders are often comorbid with mental health and obesity. Treating sleep and circadian problems and any related health conditions concurrently is generally associated with better health outcomes compared with treating these disorders alone , Addressing modern emotional stresses and mental health issues is also important given that they are prominent risk factors for insufficient sleep and obesity.

Growing evidence indicates that both insufficient sleep and circadian misalignment contribute to adverse metabolic health and obesity by altering multiple components of energy metabolism and behaviour.

Insufficient sleep increases 24 h energy expenditure and, under controlled energy intake conditions, changes in appetite hormones occur that promote hunger and energy intake 75 , 76 , 80 , Importantly, during insufficient sleep and ad libitum food intake, 24 h energy intake is higher than the increase in 24 h energy expenditure, which leads to a positive energy balance 5 , 76 , Furthermore, energy intake tends to occur later in the day for example, after dinner despite appetite-reducing changes in the levels of appetite hormones.

Later timing of food intake is associated with lower thermic effects of food than earlier timing of intake and obesity 76 , , , , , The timing of food intake is emerging as an important factor in weight regulation. Food choices during conditions of insufficient sleep might also be less healthy than during adequate sleep , , , , Circadian misalignment increases the risk of obesity by reducing 24 h energy expenditure.

Furthermore, changes in appetite hormones occur that promote hunger and energy intake , , , Energy intake does not seem to be higher in shift workers experiencing circadian misalignment than in non-shift workers; however, food choices might be less healthy and obesity rates are higher , , , Findings from rodent models indicate that the consumption of calories during the circadian time typically reserved for sleep leads to more weight gain than consumption of the same number of calories during the circadian time typically reserved for wakefulness , These findings highlight that, even without changes in energy intake, weight gain could ensue when energy is consumed at inappropriate circadian times.

Knowledge in this field has substantially increased over the past 10 years and the importance of sleep is increasingly recognized in public health strategies and clinical practice , However, key knowledge gaps remain and future studies are needed to address these gaps and move the agenda forward Box 3.

Sleep and circadian rhythms are critical for optimal metabolic and weight regulation and directly influence eating and activity behaviours to impact health. Future efforts should aim to quantify the global burden of disease associated with poor sleep health and circadian health for example, health-care and productivity costs and test the cost-effectiveness of interventions at the population level.

Sleep and circadian health are important pillars of health and are part of an overall healthy lifestyle along with a healthy diet and physical activity.

Large trials with long follow-ups are needed to determine whether the short-term effects of sleep restriction and circadian disruption on metabolic health and obesity last over time.

Furthermore, studies are needed to determine whether there are differences between acute and chronic insufficient sleep and circadian disruption. Research in this area is limited by safety concerns; thus, designs are mostly limited to observational studies.

The interaction between sleep, circadian clocks and gut hormones and how these factors modulate appetite and metabolism as well as their clinical relevance for the efficacy of novel pharmacotherapies for obesity should be examined.

The timing of food intake as it relates to the sleep schedule and circadian timing as well as its influence on altering metabolic health and obesity should be examined. Studies are needed to examine how the different sleep health characteristics, combined and individually, affect metabolic health and obesity.

Research is needed to determine whether energy intake is promoted under conditions of circadian misalignment and ad libitum food intake.

Studies are needed to examine the most effective circadian times for exercising and how much exercise is needed for shift workers to maintain their metabolic health. Studies should examine whether obesity, independent of sleep disorders, causes poor sleep and should identify the underlying mechanisms.

Additional investigations are needed into how diet content and quality affect circadian rhythmicity and sleep health. NCD Risk Factor Collaboration NCD-RisC.

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Zhu, B. Effects of sleep restriction on metabolism-related parameters in healthy adults: a comprehensive review and meta-analysis of randomized controlled trials. Sleep Med. This review enhances our knowledge about the detrimental effects of sleep restriction on metabolism and provides novel directions in preventing metabolic diseases, including obesity and T2DM.

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Chan, C. Prevalence of insufficient sleep and its associated factors among working adults in Malaysia. Sleep 13 , — Wright, K. Entrainment of the human circadian clock to the natural light-dark cycle. This study has important implications for understanding how modern light exposure patterns contribute to late sleep schedules and might disrupt sleep and circadian clocks.

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org Medical School Nursing Find a Clinical Trial. Circadian Rhythm Sleep Disorders. with wake up time after 10 in the morning. This results in difficulty falling asleep and waking up at times conducive to school and work.

When the individual attempts to wake up earlier, they become sleep deprived and alertness may be impaired. This condition is most common in adolescents. This makes it difficult to stay awake through the evening hours and people who have this kind of circadian rhythm sleep disorder often wake up much earlier than desired.

Irregular Sleep Wake Disorder is most commonly seen in elderly patients with dementia and refers to a lack of rhythm in a person's sleep and wake cycle.

Sleep occurs irregularly throughout a hour period. The individual cannot sleep through the night and has difficulty maintaining wakefulness during the day. Free-running disorder or non hour sleep-wake disorder is rare and seen more commonly in individuals with blindness.

Bright morning light sunrise aligns our internal clock to the hour day. When light perception is absent, the sleep period drifts later and later each day, causing this disorder. Jet Lag happens during air travel when we traverse time zones faster than our body clocks can adjust. This causes a mismatch between the preferred sleep and waking times and the destination sleep and waking times.

Conversely, circadian rhythm disturbances are common in people with depression, who often have changes in the pattern of their sleep, their hormone rhythms, and body temperature rhythms. Symptoms of depression may also have a circadian rhythm, as some people experience more severe symptoms in the morning.

Many successful treatments of depression, including bright light therapy, wake therapy , and interpersonal and social rhythm therapy , also directly affect circadian rhythms. For the impact of circadian rhythm on the occurrence and treatment of depression related to bipolar disorder, please see this blog post on light therapy for bipolar disorder.

Misalignment of the circadian rhythm may also provoke anxiety. Shift work results in a sleep disorder when your nighttime work shifts affect your ability to fall asleep and stay asleep, causing you to have excessive sleepiness during the day that in turn results in distress and affects your ability to function normally.

Nurses with shift work disorder have increased anxiety scores on questionnaires. In a study on jet lag , in which travel changes the time of the external environment so that it is no longer synchronized with the internal clock and disrupts sleep, travelers had elevated anxiety and depression scores.

In seasonal affective disorder, people feel down and depressed in the winter months. Researchers believe this is due to changes in circadian rhythms as a result of seasonal changes in the length of daylight.

People with seasonal affective disorder feel better using artificial morning light to realign their circadian rhythm with their sleep-wake cycle. There is no way to change your circadian type since it is genetically determined, though there is some natural change that occurs during your lifespan.

For example, our circadian sleep phase tends to shift later during adolescence more owls and advances earlier as we age more like the lark. If you find that your circadian sleep phase is out of sync with your desired schedule, you can either shift your social life to match your circadian rhythm, or try to shift your circadian rhythm to match your social life.

It may be easier to try to shift your work and social life to your circadian rhythm: an example would be a person who has a delayed circadian rhythm and likes to sleep late and wake up late switching from a job with a 7 AM start time to a job which allows him or her to start working later — around 10 AM.

The other option would be talking to a sleep physician and doing ongoing work to try to shift your circadian rhythm to match your work and social life to an earlier wakeup time. Exposure to light in the morning helps synchronize the clock.

Exposure to bright light at night, including bright artificial lights and screen time on laptops, tablets, and phones, can cause disruption in circadian rhythm and may contribute to worsening mood and negative consequences for health.

Lawrence Epstein, MD , Contributor. Syed Moin Hassan, MD , Contributor. As a service to our readers, Harvard Health Publishing provides access to our library of archived content.

Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician. When you wake up in the morning, are you refreshed and ready to go, or groggy and grumpy?

For many people, the second scenario is all too common. Improving Sleep: A guide to a good night's rest describes the latest in sleep research, including information about the numerous health conditions and medications that can interfere with normal sleep, as well as prescription and over-the-counter medications used to treat sleep disorders.

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