Charles Czeisler

Charles Czeisler
Harvard Medical School | HMS · Division of Sleep Medicine

Ph.D., M.D.

About

520
Publications
110,167
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55,352
Citations

Publications

Publications (520)
Preprint
Background: Sleep deficiency can adversely affect the performance of resident physicians resulting in greater medical errors. However, the impact of sleep deficiency on surgical outcomes, particularly among attending surgeons is less clear. Methods: Sixty attending surgeons from academic and community departments of surgery or obstetrics and gyneco...
Preprint
Objectives: This study assessed the associations between parent intent to have their child receive COVID-19 vaccination, and demographic factors and various child activities including attendance at in-person education or childcare. Methods: Persons undergoing COVID-19 testing residing in Minnesota and Los Angeles County, California with children ag...
Preprint
Background Given a downward age shift in COVID-19-involved deaths observed during the COVID-19 pandemic, we sought to estimate years of life lost (YLL) associated with leading causes of US death during the first 20 months of the pandemic. Findings Despite 4796 fewer COVID-19 deaths in Jan-Oct 2021 than in Mar-Dec 2020, the number of YLL due to COV...
Article
Full-text available
We conducted a retrospective observational study using remote wearable and mobile application data to evaluate whether US public holidays or Daylight Saving Time transitions were associated with significant changes in sleep behaviors, including sleep duration, sleep onset and offset, and the consistency of sleep timing, as well as changes in the po...
Article
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Restorative sleep is a commonly used term but a poorly defined construct. Few studies have assessed restorative sleep in nationally representative samples. We convened a panel of 7 expert physicians and researchers to evaluate and enhance available measures of restorative sleep. We then developed the revised Restorative Sleep Questionnaire (REST-Q)...
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Introduction Sleep deficiency and undiagnosed or untreated sleep disorders are pervasive among employed adults, yet are often ignored in the context of workplace health promotion. Smartphone applications (apps) are a promising, scalable approach to improving sleep among employees. We evaluated an online sleep education program followed by access to...
Article
Background: The Accreditation Council for Graduate Medical Education (ACGME) enacted a policy in 2011 that restricted first-year resident physicians in the USA to work no more than 16 consecutive hours. This was rescinded in 2017. Methods: We conducted a nationwide prospective cohort study of resident physicians for 5 academic years (2002-2007)...
Article
Circadian adaptation to shifted sleep/wake schedules may be facilitated by optimizing the timing, intensity and spectral characteristics of light exposure, which is the principal time cue for mammalian circadian pacemaker, and possibly by strategically timing non‐photic time cues such as exercise. Therefore, circadian phase resetting by light and e...
Article
Aging is associated with changes in sleep, and improving sleep may have important consequences for the health, cognition, and quality of life of older adults. Many prescription sleep aids increase the risk of nighttime falls, have adverse effects on next‐day cognition, and are associated with increased mortality. Melatonin, a hormone secreted at ni...
Article
Objectives To characterize objective sleep patterns among U.S. adults before and during the COVID-19 pandemic, and to assess for associations between adverse mental health symptoms and (1) sleep duration and (2) the consistency of sleep timing before and during the pandemic. Design Longitudinal objective sleep-wake data during January-June 2020 we...
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Full-text available
Ocular light exposure has important influences on human health and well-being through modulation of circadian rhythms and sleep, as well as neuroendocrine and cognitive functions. Prevailing patterns of light exposure do not optimally engage these actions for many individuals, but advances in our understanding of the underpinning mechanisms and eme...
Article
Chronic sleep restriction (CSR) has been associated with adverse effects including cognitive impairment and increased risk of diabetes and cardiovascular disease. Yet, sleep restriction therapy is an essential component of most behavioral treatments for insomnia. Moreover, little is known about the impact of CSR on sleep continuity and structure in...
Article
Background: Nearly 14% of Americans experience chronic circadian disruption due to shift work, increasing their risk of obesity, diabetes, and other cardiometabolic disorders. These disorders are also exacerbated by modern eating habits such as frequent snacking and consumption of high-fat foods. Methods: We investigated the effects of recurrent...
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While studies suggest that light and feeding patterns can reset circadian rhythms in various metabolites, whether these shifts follow a predictable pattern is unknown. We describe the first phase response curves (PRC) for lipids and hepatic proteins in response to combined light and food stimuli. The timing of plasma rhythms was assessed by constan...
Article
The daily rhythm of plasma melatonin concentrations is typically unimodal, with one broad peak during the circadian night and near‐undetectable levels during the circadian day. Light at night acutely suppresses melatonin secretion and phase shifts its endogenous circadian rhythm. In contrast, exposure to darkness during the circadian day has not ge...
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Full-text available
Sleep deficiency is a hidden cost of our 24–7 society, with 70% of adults in the US admitting that they routinely obtain insufficient sleep. Further, it is estimated that 50–70 million adults in the US have a sleep disorder. Undiagnosed and untreated sleep disorders are associated with diminished health for the individual and increased costs for th...
Chapter
Sleep, a modifiable health behavior and an essential physiologic state, is a fundamental human need for overall health and survival. Sleep health has emerged as a broad concept to refer to healthy sleep. Sleep health involves several measurable dimensions including satisfaction, alertness, timing, efficiency, and duration. Sleep disorders and sleep...
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Many people are concerned about whether they are getting “enough” sleep, and if they can “sleep too much.” These concerns can be approached scientifically using experiments probing long-term (i.e., multi-night) sleep homeostatic processes, since homeostatic processes move the system toward its physiological setpoint (i.e., between “not enough” and...
Article
Diabetes affects approximately one in 10 persons in the United States† and is a risk factor for severe COVID-19 (1), especially when a patient's diabetes is not well managed (2). The extent to which the COVID-19 pandemic has affected diabetes care and management, and whether this varies across age groups, is currently unknown. To evaluate access to...
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Full-text available
Sleep deficiencies and associated performance decrements are common among astronauts during spaceflight missions. Previously, sleep in space was analyzed with a focus on global measures while the intricate structure of sleep oscillations remains largely unexplored. This study extends previous findings by analyzing how spaceflight affects characteri...
Preprint
We conducted a retrospective observational study using remote wearable and mobile application data to identify US public holidays associated with significant changes in sleep behaviors, including sleep duration, bedtime and waketime, and the consistency of sleep timing, as well as changes in the point prevalence of alcohol use. These metrics were c...
Article
Study Objectives Clinical and population health recommendations are derived from studies that include self-report. Differences in question wording and response scales may significantly affect responses. We conducted a methodological review assessing variation in event definition(s), context (i.e., work- versus free-day), and timeframe (e.g., “in th...
Preprint
Sleep deficiency and undiagnosed or untreated sleep disorders are pervasive among employed adults, yet often ignored in the context of workplace health promotion programs among employers. Smartphone applications (app) are a promising, scalable approach to improving sleep among employees. In this randomized clinical trial, we evaluate the dayzz app,...
Preprint
Sleep deficiency is a hidden cost of our 24-7 society, with 70% of adults in the US admitting that they routinely obtain insufficient sleep. Further, it is estimated that 50-70 million adults in the US have a sleep disorder. Undiagnosed and untreated sleep disorders are associated with diminished health for the individual and increased costs for th...
Article
Full-text available
A potential contributor to insufficient sleep among college students is their daily schedule, with sleep sacrificed for other waking activities. We investigated how daily schedules predict day-to-day sleep-wake timing in college students. 223 undergraduate college students (M±SD = 19.2±1.4 years, 37% females) attending a Massachusetts university in...
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Insufficient sleep, which has been shown to adversely affect metabolism, is generally associated with prolonged exposure to artificial light at night, a known circadian disruptor. There is growing evidence suggesting that circadian disruption adversely affects metabolism, yet few studies have attempted to evaluate the adverse metabolic effects of i...
Article
Background : Unpaid caregivers of adults play critical roles in health care systems by providing care to older adults and those with chronic conditions. The COVID-19 pandemic has heightened caregiving needs, forcing some into caregiving roles and disrupting others. We sought to estimate the prevalence of and identify factors associated with adverse...
Article
Adults with disabilities, a group including >25% of U.S. adults (1), experience higher levels of mental health and substance use conditions and lower treatment rates than do adults without disabilities* (2,3). Survey data collected during April-September 2020 revealed elevated adverse mental health symptoms among adults with disabilities (4) compar...
Article
Objective: To evaluate whether caregiving for older adults is associated with insomnia symptoms and diminished workplace productivity. Methods: We analyzed data collected from caregivers to older adults in the US. Participants self-reported awakenings from sleep (caregiving-related or spontaneous) and workplace measures (presenteeism, absenteeis...
Article
Study objectives: To determine whether there was evidence of circadian or sleep-regulatory dysfunction in sighted individuals with Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD). Methods: Three sighted individuals with signs and/or symptoms of N24SWD were studied. Thirty-five to three-hundred and thirty-two day laboratory and home-based assessm...
Article
Two patients with delayed sleep-wake phase disorder (DSWPD) demonstrated improvement in sleep quality and duration, reduction in symptoms, and elimination of the need for hypnotic or stimulant medications after changing their sleep schedules in response to the coronavirus disease 2019 (COVID-19) pandemic lockdown work schedule changes. These cases...
Preprint
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Rigorous nonpharmaceutical interventions (e.g., stay-at-home orders, remote-work directives) were implemented in early 2020 for coronavirus disease 2019 (COVID-19) pandemic containment in the U.S. During this time, increased sleep duration and delayed sleep timing were reported through surveys (Leone et al., 2021) and wearable data (Rezaei and Gran...
Article
Objectives: Due to the significant mortality and morbidity consequences of the coronavirus 2019 (COVID-19) pandemic among older adults, these individuals were urged to avoid going out in public and socializing with others, among other major disruptions to daily life. While these significant and often unavoidable disruptions have been shown to bear...
Article
Early during the COVID-19 pandemic, nearly two thirds of unpaid caregivers of adults reported adverse mental or behavioral health symptoms, compared with approximately one third of noncaregivers† (1). In addition, 27% of parents of children aged <18 years reported that their mental health had worsened during the pandemic (2). To examine mental heal...
Article
Sleep difficulties have been implicated in the development and progression of dementia and in all-cause mortality. This study examines the relationship between sleep difficulties, incident dementia and all-cause mortality over 8 years of follow-up among a nationally representative sample of older (≥65 years) adults in the United States. We used dat...
Article
The COVID-19 pandemic has been associated with mental health consequences due to direct (i.e., SARS-CoV-2 infection, potentially due to neuronal or astrocytic infection, microvascular, or inflammatory mechanisms) and indirect (i.e., social and economic impacts of COVID-19 prevention measures) mechanisms. Investigation of mental health in a region w...
Article
Shiftwork and circadian disruption are associated with adverse metabolic effects. Therefore, we examined whether clinical biomarkers of metabolic health are under endogenous circadian regulation using a 40‐h constant routine protocol (CR; constant environmental and behavioral conditions) and evaluated the impact of typical daily conditions with per...
Article
The time of dim light melatonin onset (DLMO) is the gold standard for circadian phase assessment in humans, but collection of samples for DLMO is time and resource intensive. Numerous studies have attempted to estimate circadian phase from actigraphy data, but most of these studies have involved individuals on controlled and stable sleep-wake sched...
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Full-text available
Aims Markedly elevated adverse mental health symptoms were widely observed early in the coronavirus disease-2019 (COVID-19) pandemic. Unlike the U.S., where cross-sectional data indicate anxiety and depression symptoms have remained elevated, such symptoms reportedly declined in the U.K., according to analysis of repeated measures from a large-scal...
Preprint
Full-text available
Importance SARS-CoV-2 containment is estimated to require attainment of high (>80%) post-infection and post-vaccination population immunity. Objective To assess COVID-19 vaccine intentions among US adults and their children, and reasons for vaccine hesitancy among potential refusers. Design Internet-based surveys were administered cross-sectionally...
Article
Introduction Melatonin levels are partially driven by the parenchyma volume of the pineal gland. Low urinary levels of 6‐sulfatoxymelatonin have been associated with increased risk of advanced prostate cancer, but the relationship between pineal gland volume and composition and prostate cancer risk has not been examined. Materials and Methods We u...
Article
Objectives: Rotating shift work is associated with adverse outcomes due to circadian misalignment, sleep curtailment, work-family conflicts, and other factors. We tested a bright light countermeasure to enhance circadian adaptation on a counterclockwise rotation schedule. Methods: Twenty-nine adults (aged 20-40 years; 15 women) participated in a...
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Full-text available
Background Governments worldwide recommended unprecedented measures to contain the coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As pressure mounted to scale back measures, understanding public priorities was critical. We assessed initial public adherence with and support for s...
Article
Objectif Notre objectif était d’identifier les tendances en matière de durée du sommeil et de Jet-Lag social en utilisant les données d’une application mobile populaire en France et au Canada, “iSommeil”. Méthodes Nous avons examiné 8 207 nuits de iSommeil, une application de suivi du sommeil très répandue en France et au Canada. Dans cette analys...
Article
Intermittent light (IML) pulses are more efficient per minute of exposure than continuous exposure in resetting the phase of the human circadian pacemaker. We assessed the spectral sensitivity in phase resetting, melatonin suppression and alertness induced by IML pulses. Twelve healthy young adults (6 females; mean age ± SD = 25.4 ± 3.6 years) were...
Article
Polyphasic sleep is the practice of distributing multiple short sleep episodes across the 24-hour day rather than having one major and possibly a minor (“nap”) sleep episode each day. While the prevalence of polyphasic sleep is unknown, anecdotal reports suggest attempts to follow this practice are common, particularly among young adults. Polyphasi...
Article
Objectives: Extended-duration work rosters (EDWRs) with shifts of 24+ hours impair performance compared with rapid cycling work rosters (RCWRs) that limit shifts to 16 hours in postgraduate year (PGY) 1 resident-physicians. We examined the impact of a RCWR on PGY 2 and PGY 3 resident-physicians. Methods: Data from 294 resident-physicians were an...
Article
Background: Sleep disturbance and deficiency are common among older adults and have been linked with dementia and all-cause mortality. Using nationally representative data, we examine the relationship between sleep disturbance and deficiency and their risk for incident dementia and all-cause mortality among older adults. Methods: The National He...
Preprint
Full-text available
Objectives To estimate the prevalence of unpaid caregiving during the coronavirus disease 2019 (COVID-19) pandemic, and to identify factors associated with adverse mental health symptoms, substance use, and suicidal ideation in this population, which provides critical support in health care systems by providing care to older adults and those with c...
Preprint
Full-text available
Aims Markedly elevated adverse mental health symptoms were widely observed early in the coronavirus disease 2019 (COVID-19) pandemic. Unlike the U.S., where cross-sectional data indicate anxiety and depression symptoms have remained elevated, such symptoms reportedly declined in the U.K., according to analysis of repeated measures from a largescale...
Article
Appropriate synchronization of the timing of behaviors with the circadian clock and adequate sleep are both important for almost every physiological process. The timing of the circadian clock relative to social (i.e., local) clock time and the timing of sleep can vary greatly between individuals. Whether the timing of these processes is stable with...
Article
This project was designed to support the US Navy's (USN) implementation of circadian-based watchbills by providing guidance on sleep management and shipboard practices which support crew endurance. In the first two years of the three-year effort, we identified specific training needs and developed instructor-led materials. We delivered the training...
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Full-text available
Cross-sectional observations have shown that the timing of eating may be important for health-related outcomes. Here we examined the stability of eating timing, using both clock hour and relative circadian time, across one semester (n = 14) at daily and monthly time-scales. At three time points ~ 1 month apart, circadian phase was determined during...
Preprint
Full-text available
Ocular light exposure has important influences on human health and well-being through modulation of circadian rhythms and sleep, as well as neuroendocrine and cognitive functions. Current patterns of light exposure do not optimally engage these actions for many individuals, but advances in our understanding of the underpinning mechanisms and emergi...
Article
Background Poor sleep health, including sleep deficiency and sleep disturbance, is common among employed adults in the U.S. and is associated with undesirable workplace outcomes. Adoption of workplace health promotion programs (WHPPs) is increasing, yet few programs aim to reduce fatigue or improve sleep among employees. Objective We analyzed data...
Article
Background Sleep difficulties are common among older adults, and clinical management of sleep difficulties commonly includes sleep medication (pharmacological and non-pharmacological). Our research examines sleep medication use and incident dementia over 8 years using nationally representative data from older adults ages 65 years and older in the U...
Article
Full-text available
Frequent hand hygiene, including handwashing with soap and water or using a hand sanitizer containing ≥60% alcohol when soap and water are not readily available, is one of several critical prevention measures recommended to reduce the spread of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19).* Previous studies identified demog...
Article
Objective: We evaluated the efficacy of a combined short-wavelength-enriched white light and exercise fatigue countermeasure during breaks for flight controllers working overnight shifts. Methods: Twenty NASA flight controllers were studied for two blocks of nightshifts in ISS mission control, randomized to either the control or countermeasure c...
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Full-text available
Context Dyslipidemia and cardiovascular disease are common in shift workers and eating at night may contribute to this pathophysiology. Objective To examine the effects of eating at different times of day on lipid profiles. Design Two 24-hour baseline days with 8 hours of sleep, 3 meals (breakfast, lunch, dinner) and a snack, followed by a 40-hou...
Article
Full-text available
Temporary disruptions in routine and nonemergency medical care access and delivery have been observed during periods of considerable community transmission of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19) (1). However, medical care delay or avoidance might increase morbidity and mortality risk associated with treatable and p...
Preprint
Full-text available
Background Clinical practice guidelines and population health recommendations are derived from studies that include self-reported data. Small semantic differences in question wording and response scales, may significantly affect the response. We conducted a methodological review to assess the variation in event definition(s), context (i.e., work- v...