Can melatonin improve adaptation to night shift?

Effectiveness of sleep interventions for rotating night shift workers: a systematic review and meta-analysis

Background

Sleep disturbance is a common issue among rotating night shift workers and is closely related to health risks. The present study aimed to determine the effectiveness of pharmacological and non-pharmacological sleep interventions for the management of sleep disturbance among rotating night shift workers.

Methods

For this systematic review and meta-analysis, we searched six electronic databases-EMBASE, CINAHL, Cochrane Library, PubMed, Scopus, and Web of Science-for randomized controlled trials and clinical trials published from January 1990 to June 2022. The quality of eligible studies was independently assessed by three authors using the Joanna Briggs Institute Critical Appraisal Checklist for randomized controlled trials and quasi-experimental studies. The meta-analysis was performed based on the random effects model using the Comprehensive Meta-Analysis software. The study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

Results

Of the 1019 studies retrieved, 30 met the inclusion criteria for the systematic review; 25 were selected for the meta-analysis. Sleep interventions were categorized as follows: pharmacological approach (n = 7), light therapy (n = 9), cognitive behavioral approach (n = 7), aroma or alternative therapy (n = 4), and shift schedule modification (n = 3). The overall mean effect size of the interventions was moderate (Hedges' g = 0.59; 95% confidence interval = 0.33-0.84, z = 4.50, p < 0.001).

Conclusion

Sleep interventions were effective in promoting sleep or reducing sleep disturbance among rotating night shift workers. These findings provide evidence of the effectiveness of various pharmacological and non-pharmacological sleep interventions for managing sleep health in the work environment of rotating night shift workers.

Is Melatonin the "Next Vitamin D"?: A Review of Emerging Science, Clinical Uses, Safety, and Dietary Supplements

Melatonin has become a popular dietary supplement, most known as a chronobiotic, and for establishing healthy sleep. Research over the last decade into cancer, Alzheimer's disease, multiple sclerosis, fertility, PCOS, and many other conditions, combined with the COVID-19 pandemic, has led to greater awareness of melatonin because of its ability to act as a potent antioxidant, immune-active agent, and mitochondrial regulator. There are distinct similarities between melatonin and vitamin D in the depth and breadth of their impact on health. Both act as hormones, affect multiple systems through their immune-modulating, anti-inflammatory functions, are found in the skin, and are responsive to sunlight and darkness. In fact, there may be similarities between the widespread concern about vitamin D deficiency as a "sunlight deficiency" and reduced melatonin secretion as a result of "darkness deficiency" from overexposure to artificial blue light. The trend toward greater use of melatonin supplements has resulted in concern about its safety, especially higher doses, long-term use, and application in certain populations (e.g., children). This review aims to evaluate the recent data on melatonin's mechanisms, its clinical uses beyond sleep, safety concerns, and a thorough summary of therapeutic considerations concerning dietary supplementation, including the different formats available (animal, synthetic, and phytomelatonin), dosing, timing, contraindications, and nutrient combinations.

The Effects of the Exogenous Melatonin on Shift Work Sleep Disorder in Health Personnel: A Systematic Review

(1) Background: To know the medical documentation related to exogenous melatonin in sleep disorders caused by shift work in health personnel; (2) Methods: Systematic and critical review. Data were obtained by looking up the bibliographic data base: MEDLINE (via Pubmed), Embase, Cochrane Library, Scopus, Web of Science, Latin American and Caribbean literature in Health Sciences (LILACS) and Medicine in Spanish (MEDES). The used terms, as descriptors and text in the title and abstract record fields, were "Health Personnel", "Melatonin" and "Sleep Disorders", Circadian Rhythm, by using the following filters: "Humans", "Adult: 19+ years" and "Clinical Trial". The search update was in December 2021. The documentary quality of the articles was assessed using the CONSORT questionnaire. (3) Results: Having applied the inclusion and exclusion criteria, 10 clinical essays were selected out of 98 retrieved references. CONSORT scores ranged from a minimum of 6.0 to a maximum of 13. 7 with a median of 10.2. According to the SIGN criteria, this review presented "1-"evidence with a grade of recommendation B. The intervention dose via administration of exogenous melatonin ranged between 1 and 10 mg. It was not mentioned whether the route of administration was by fast or slow absorption. The outcomes showed decreased daytime sleepiness, lessened sleep onset latency, diminished night-time awakenings, increased total sleep period and improved daytime attention in the melatonin-treated group; (4) Conclusions: Exogenously administered melatonin is effective in shift worker health personnel that are suffering from sleep disorders, and given its low adverse effects and tolerability, it might be recommended. A great disparity was evidenced in terms of dose, follow-up periods and type of melatonin, small participant population, same age ranges and young age. Therefore, new trials would be needed to amend these observations in order to have full evidence that is able to ensure the efficacy of exogenous melatonin in the studied population.

Emergency Medicine Personnel's Preparation, Performance and Perception of Their Night Shifts: A Cross-Sectional Study from Saudi Arabia

PURPOSE

This study aimed to investigate the perceptions and habits of different emergency department (ED) workers (nurses, residents, and attending physicians) and their pre- or post-shift routines. The study also examined the effect of night shifts on personal life, social life, and health.

PATIENTS AND METHODS

An anonymous, online, cross-sectional, multiple-choice, self-rating (5-point Likert scale) survey was administered to the participants. All analyses were performed using the SPSS version 22.0. Ethical approval was obtained from the Institutional Review Board (IRB) of King Saud University Medical City (KSUMC) in Riyadh, Saudi Arabia.

RESULTS

Thirty-three nurses, 51 residents, and 39 attending physicians participated in the survey (response rates of 21%, 100%, and 100%, respectively). A significant difference was noted in the need to use physical sleeping aids between the three groups (P < 0.003), with more nurses using humidifiers as a sleeping aid (21.2%) than residents or attending physicians. However, there was no difference in the use of pharmacological aids between the three groups. All groups utilized coffee as the preferred stimulant, especially residents (76.5%, P <0.032). Nurses and attending physicians wake up 2 hours before their shift, while residents prefer 3 hours (P <0.001). Attending physicians reported the highest accident rates post-night shifts of 17.9% (P < 0.001). Residents reported satisfaction while working night shifts and were least in agreement with night shifts reducing life span. Attending physicians were more in agreement with the increasing risk of drug/alcohol misuse and the incidence of depression in relation to night shifts.

CONCLUSION

Participants shared many commonalities, yet residents were less likely to use sleeping aids and enjoy night shifts more than the other groups. All groups consumed coffee for stimulation. Attending physicians reported the highest accident rates post night shifts.

Implementation of interventions designed to promote healthy sleep and circadian rhythms in shiftworkers

Shiftwork is a significant risk factor for a host of negative health and safety outcomes, which have been at least partly attributed to disturbances of the circadian timing system. As a result, an entire sub-field of chronobiology has been devoted to developing and evaluating countermeasures for circadian misalignment, sleep disruption, fatigue, and other issues associated with shiftwork. Much of this research takes place under highly controlled laboratory conditions due to the necessity of accurately characterizing individual rhythms, both for intervention design and assessment of efficacy. Applied studies of interventions for shiftworkers are, by their nature, more complicated, often demonstrating less consistent findings. While this, in part, reflects execution under less rigorously controlled conditions, it may also stem from variability in implementation approaches. A systematic review of published studies (through May 2017) of interventions designed to enhance circadian health in shiftworkers was conducted to determine the frequency and quality of the assessment of implementation as well as barriers and enablers to implementation. A search of PubMed, PsychINFO, Web of Science, and CINAHL databases yielded a total of 5368 unique references. After a title and abstract screen, 323 proceeded to full-text review; 68 of those met final criteria for data extraction. Implementation was assessed to some degree in 60.3% of those 68 articles. Where it was assessed, the mean quality score on a scale from 1 to 5 (1 = very little, 3 = moderate, 5 = very in-depth) was 2.56. One or more enablers were identified in just 17 of the 68 studies (25.0%), and barriers in just 18 (26.5%). Implementation of these interventions is a critical but seldom-acknowledged component of their uptake and effectiveness, and we highly recommend that future shiftworker intervention research make an effort to incorporate formalized assessments of implementation and/or hybrid effectiveness-implementation approaches.

Melatonin Is a Feasible, Safe, and Acceptable Intervention in Doctors and Nurses Working Nightshifts: The MIDNIGHT Trial

Nightshift working is associated with sleep deprivation, fatigue and attention/concentration deficits which, in healthcare workers, may impact on patient safety. Clinical staff in the UK routinely work several 12 h nightshifts in a row at about 1-3 month intervals. We investigated the feasibility and acceptability of a crossover trial of melatonin administration in clinical staff working nightshifts with an exploration of effects on sleep measures and attention/concentration tasks. This was a pilot, double-blinded, randomized, placebo-controlled crossover feasibility trial in doctors and nurses working 3 consecutive nightshifts at a tertiary referral hospital in the UK. Twenty five male and female subjects were randomized to receive either 6mg Circadin™ slow release melatonin or placebo before sleep after each consecutive nightshift, followed by a washout period, before crossing over to the other experimental arm. We used actigraphy for objective assessment of sleep parameters. The trial design was feasible and acceptable to participants with negligible side effects, but elevated melatonin levels were prolonged during the active arm (P=0.016). Double digit addition testing, a concentration/attention task, improved with melatonin treatment (P<0.0001). Lapses of vigilance or judgement while doctors or nurses are working nightshifts could impact on patient safety and melatonin may be a useful intervention. This study supports the conclusion that a larger definitive trial of this design is both feasible and safe. Clinical Trial Registration: identifier ISRCTN15529655. https://www.isrctn.com/.

Chronotherapeutics: Recognizing the Importance of Timing Factors in the Treatment of Disease and Sleep Disorders

This review describes the characteristics of a number of pathologies, which are considered from the point of view of chronobiology, that is, the way in which biological processes are expressed throughout the 24-hour day. This perspective is a relatively new way of thinking about disease and additionally about how to treat diseases. It has called attention to the importance of not only the quantity of a drug that is administered but also when it is administered. In addition, the review presents an overview of the emerging clinical strategies known as chronotherapeutics, that is, the effects of the daily scheduling of drug administration and the consequences of the activity and efficacy of therapies that are applied in this manner. This article also reviews innovative ways in which physicians are applying time-specified drug treatment (chronopharmacology) for sleep disorders. Here, we present a systematic description of chronopharmacology as well as definitions of key terms that, we believe, will be helpful for newcomers to the field. It is hoped that greater awareness of this new perspective on pharmacology will promote its adoption by researchers and clinicians.

Exogenous melatonin as a treatment for secondary sleep disorders: A systematic review and meta-analysis

Melatonin is a physiological indoleamine involved in circadian rhythm regulation and it is currently used for secondary sleep disorders supported by empirical evidence. A small amount of evidence and some controversial results have been obtained in some randomized controlled trials (RCT). The objective of this meta-analysis is to determine the efficacy of exogenous melatonin versus placebo in managing secondary sleep disorders. Literature retrieval of eligible RCT was performed in 5 databases (PubMed, Embase, Cochrane Library, ClinicalTrials.gov, and Web of Science). In total, 7 studies of 205 patients were included. Pooled data demonstrate that exogenous melatonin lowers sleep onset latency and increases total sleep time, whereas it has little if any effect on sleep efficiency. Although, the efficacy of melatonin still requires further confirmation, this meta-analysis clearly supports the use of melatonin as a management for patients with secondary sleep disorders.

The effectiveness of melatonin for promoting healthy sleep: a rapid evidence assessment of the literature

A systematic review was conducted using Samueli Institute’s Rapid Evidence Assessment of the Literature (REAL^©) process to determine the evidence base for melatonin as an agent to optimize sleep or improve sleep quality, and generalize the results to a military, civilian, or other healthy, active, adult population. Multiple databases were searched yielding 35 randomized controlled trials (RCTs) meeting the review’s inclusion criteria, which were assessed for methodological quality as well as for melatonin effectiveness. The majority of included studies were high quality (83.0%). Overall, according to Grading Recommendations, Assessment Development and Evaluation (GRADE) methodology, weak recommendations were made for preventing phase shifts from jet lag, for improving insomnia in both healthy volunteers and individuals with a history of insomnia, and for initiating sleep and/or improving sleep efficacy. Based on the literature to date, no recommendations for use in shift workers or to improve hormonal phase shift changes in healthy people can be made at this time. Larger and longer-duration RCTs utilizing well characterized products are needed to warrant melatonin recommendations in young, healthy adults.

Pharmacological interventions for sleepiness and sleep disturbances caused by shift work

BACKGROUND

Shift work results in sleep-wake disturbances, which cause sleepiness during night shifts and reduce sleep length and quality in daytime sleep after the night shift. In its serious form it is also called shift work sleep disorder. Various pharmacological products are used to ameliorate symptoms of sleepiness or poor sleep length and quality.

OBJECTIVES

To evaluate the effects of pharmacological interventions to reduce sleepiness or to improve alertness at work and decrease sleep disturbances whilst off work, or both, in workers undertaking shift work in their present job and to assess their cost-effectiveness.

SEARCH METHODS

We searched CENTRAL, MEDLINE, EMBASE, PubMed and PsycINFO up to 20 September 2013 and ClinicalTrials.gov up to July 2013. We also screened reference lists of included trials and relevant reviews.

SELECTION CRITERIA

We included all eligible randomised controlled trials (RCTs), including cross-over RCTs, of pharmacological products among workers who were engaged in shift work (including night shifts) in their present jobs and who may or may not have had sleep problems. Primary outcomes were sleep length and sleep quality while off work, alertness and sleepiness, or fatigue at work.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies, extracted data and assessed risk of bias in included trials. We performed meta-analyses where appropriate.

MAIN RESULTS

We included 15 randomised placebo-controlled trials with 718 participants. Nine trials evaluated the effect of melatonin and two the effect of hypnotics for improving sleep problems. One trial assessed the effect of modafinil, two of armodafinil and one examined caffeine plus naps to decrease sleepiness or to increase alertness.Melatonin (1 to 10 mg) after the night shift may increase sleep length during daytime sleep (mean difference (MD) 24 minutes, 95% confidence interval (CI) 9.8 to 38.9; seven trials, 263 participants, low quality evidence) and night-time sleep (MD 17 minutes, 95% CI 3.71 to 30.22; three trials, 234 participants, low quality evidence) compared to placebo. We did not find a dose-response effect. Melatonin may lead to similar sleep latency times as placebo (MD 0.37minutes, 95% CI - 1.55 to 2.29; five trials, 74 participants, low quality evidence).Hypnotic medication, zopiclone, did not result in significantly longer daytime sleep length compared to placebo in one low quality trial and we could not use the data from the study on lormetazepam.Armodafinil taken before the night shift probably reduces sleepiness by one point on the Karolinska Sleepiness Scale (KSS) (MD -0.99, 95% CI -1.32 to -0.67; range 1 to 10; two trials, 572 participants, moderate quality evidence) and increases alertness by 50 ms in a simple reaction time test (MD -50.0, 95% CI -85.5 to -15.5) at three months' follow-up in shift work sleep disorder patients. Modafinil probably has similar effects on sleepiness (KSS) (MD -0.90, 95% CI -1.45 to -0.35; one trial, 183 participants, moderate quality evidence) and alertness in the psychomotor vigilance test in the same patient group. Post-marketing, severe skin reactions have been reported. Adverse effects reported by trial participants were headache, nausea and a rise in blood pressure. There were no trials in non-patient shift workers.Based on one trial, caffeine plus pre-shift naps taken before the night shift decreased sleepiness (KSS) (MD -0.63, 95% CI -1.09 to -0.17).We judged most trials to have a low risk of bias even though the randomisation method and allocation concealment were often not described.

AUTHORS' CONCLUSIONS

There is low quality evidence that melatonin improves sleep length after a night shift but not other sleep quality parameters. Both modafinil and armodafinil increase alertness and reduce sleepiness to some extent in employees who suffer from shift work sleep disorder but they are associated with adverse events. Caffeine plus naps reduces sleepiness during the night shift, but the quality of evidence is low. Based on one low quality trial, hypnotics did not improve sleep length and quality after a night shift.We need more and better quality trials on the beneficial and adverse effects and costs of all pharmacological agents that induce sleep or promote alertness in shift workers both with and without a diagnosis of shift work sleep disorder. We also need systematic reviews of their adverse effects.

Potency of melatonin in living beings

Living beings are surrounded by various changes exhibiting periodical rhythms in environment. The environmental changes are imprinted in organisms in various pattern. The phenomena are believed to match the external signal with organisms in order to increase their survival rate. The signals are categorized into circadian, seasonal, and annual cycles. Among the cycles, the circadian rhythm is regarded as the most important factor because its periodicity is in harmony with the levels of melatonin secreted from pineal gland. Melatonin is produced by the absence of light and its presence displays darkness. Melatonin plays various roles in creatures. Therefore, this review is to introduce the diverse potential ability of melatonin in manifold aspects in living organism.

Shift work: health, performance and safety problems, traditional countermeasures, and innovative management strategies to reduce circadian misalignment

There are three mechanisms that may contribute to the health, performance, and safety problems associated with night-shift work: (1) circadian misalignment between the internal circadian clock and activities such as work, sleep, and eating, (2) chronic, partial sleep deprivation, and (3) melatonin suppression by light at night. The typical countermeasures, such as caffeine, naps, and melatonin (for its sleep-promoting effect), along with education about sleep and circadian rhythms, are the components of most fatigue risk-management plans. We contend that these, while better than nothing, are not enough because they do not address the underlying cause of the problems, which is circadian misalignment. We explain how to reset (phase-shift) the circadian clock to partially align with the night-work, day-sleep schedule, and thus reduce circadian misalignment while preserving sleep and functioning on days off. This involves controlling light and dark using outdoor light exposure, sunglasses, sleep in the dark, and a little bright light during night work. We present a diagram of a sleep-and-light schedule to reduce circadian misalignment in permanent night work, or a rotation between evenings and nights, and give practical advice on how to implement this type of plan.

Treatment of shift work disorder and jet lag

OPINION STATEMENT

With the growth of the 24-hour global marketplace, a substantial proportion of workers are engaged in nontraditional work schedules and frequent jet travel across multiple time zones. Thus, shift work disorder and jet lag are prevalent in our 24/7 society and have been associated with significant health and safety repercussions. In both disorders, treatment strategies are based on promoting good sleep hygiene, improving circadian alignment, and targeting specific symptoms.Treatment of shift work must be tailored to the type of shift. For a night worker, circadian alignment can be achieved with bright light exposure during the shift and avoidance of bright light (with dark or amber sunglasses) toward the latter portion of the work period and during the morning commute home. If insomnia and/or excessive sleepiness are prominent complaints despite behavioral approaches and adequate opportunity for sleep, melatonin may be administered prior to the day sleep period to improve sleep, and alertness during work can be augmented by caffeine and wake-promoting agents.For jet lag, circadian adaptation is suggested only for travel greater than 48 h, with travel east more challenging than travel west. Although advancing sleep and wake times and circadian timing for eastward travel with evening melatonin and morning bright light several days prior to departure can help avoid jet lag at the new destination, this approach may be impractical for many people, Therefore, strategies for treatment at the destination, such as avoidance of early morning light and exposure to late-morning and afternoon light alone or in conjunction with bedtime melatonin, can accelerate re-entrainment following eastward travel. For westward travel, a circadian delay can be achieved after arrival with afternoon and early-evening light with bedtime melatonin.Good sleep hygiene practices, together with the application of circadian principles, can improve sleep quality, alertness, performance, and safety in shift workers and jet travelers. However, definitive multicenter randomized controlled clinical trials are still needed, using traditional efficacy outcomes such as sleep and performance as well as novel biomarkers of health.

Therapeutics for Circadian Rhythm Sleep Disorders

The sleep-wake cycle is regulated by the interaction of endogenous circadian and homeostatic processes. The circadian system provides timing information for most physiological rhythms, including the sleep and wake cycle. In addition, the central circadian clock located in the suprachiasmatic nucleus of the hypothalamus has been shown to promote alertness during the day. Circadian rhythm sleep disorders arise when there is a misalignment between the timing of the endogenous circadian rhythms and the external environment or when there is dysfunction of the circadian clock or its entrainment pathways. The primary synchronizing agents of the circadian system are light and melatonin. Light is the strongest entraining agent of circadian rhythms and timed exposure to bright light is often used in the treatment of circadian rhythm sleep disorders. In addition, timed administration of melatonin, either alone or in combination with light therapy has been shown to be useful in the treatment of the following circadian rhythm sleep disorders: delayed sleep phase, advanced sleep phase, free-running, irregular sleep wake, jet lag and shift work.

Morning Melatonin Has Limited Benefit as a Soporific For Daytime Sleep After Night Work

Exogenous melatonin administration in humans is known to exert both chronobiotic (phase shifting) and soporific effects. In a previous study in our lab, young, healthy, subjects worked five consecutive simulated night shifts (23:00 to 07:00 h) and slept during the day (08:30 to 15:30 h). Large phase delays of various magnitudes were produced by the study interventions, which included bright light exposure during the night shifts, as assessed by the dim light melatonin onset (DLMO) before (baseline) and after (final) the five night shifts. Subjects also ingested either 1.8 mg sustained-release melatonin or placebo before daytime sleep. Although melatonin at this time should delay the circadian clock, this previous study found that it did not increase the magnitude of phase delays. To determine whether melatonin had a soporific effect, we controlled the various magnitudes of phase delay produced by the other study interventions. Melatonin (n=18) and placebo (n=18) groups were formed by matching a melatonin participant with a placebo participant that had a similar baseline and final DLMO (+/-1 h). Sleep log measurements of total sleep time (TST) and actigraphic measurements of sleep latency, TST, and three movement indices for the two groups were examined. Although melatonin was associated with small improvements in sleep quality and quantity, the differences were not statistically significant by analysis of variance. However, binomial analysis indicated that melatonin participants were more likely to sleep better than their placebo counterparts on some days with some measures. It was concluded that, the soporific effect of melatonin is small when administered prior to 7 h daytime sleep periods following night shift work.

Efficacy and hypnotic effects of melatonin in shift-work nurses: double-blind, placebo-controlled crossover trial

Background

Night work is associated with disturbed sleep and wakefulness, particularly in relation to the night shift. Circadian rhythm sleep disorders are characterized by complaints of insomnia and excessive daytime sleepiness that are primarily due to alterations in the internal circadian timing system or a misalignment between the timing of sleep and the 24-h social and physical environment.

Methods

We evaluated the effect of oral intake of 5 mg melatonin taken 30 minutes before night time sleep on insomnia parameters as well as subjective sleep onset latency, number of awakenings, and duration of sleep. A double-blind, randomized, placebo-controlled crossover study with periods of 1 night and washouts of 4 days comparing melatonin with placebo tablets was conducted. We tried to improve night-time sleep during recovery from night work. Participants were 86 shift-worker nurses aged 24 to 46 years. Each participant completed a questionnaire immediately after awakening.

Results

Sleep onset latency was significantly reduced while subjects were taking melatonin as compared with both placebo and baseline. There was no evidence that melatonin altered total sleep time (as compared with baseline total sleep time). No adverse effects of melatonin were noted during the treatment period.

Conclusion

Melatonin may be an effective treatment for shift workers with difficulty falling asleep.

Circadian rhythm sleep disorders: part I, basic principles, shift work and jet lag disorders. An American Academy of Sleep Medicine review

OBJECTIVE

This the first of two articles reviewing the scientific literature on the evaluation and treatment of circadian rhythm sleep disorders (CRSDs), employing the methodology of evidence-based medicine. In this first part of this paper, the general principles of circadian biology that underlie clinical evaluation and treatment are reviewed. We then report on the accumulated evidence regarding the evaluation and treatment of shift work disorder (SWD) and jet lag disorder (JLD).

METHODS

A set of specific questions relevant to clinical practice were formulated, a systematic literature search was performed, and relevant articles were abstracted and graded.

RESULTS

A substantial body of literature has accumulated that provides a rational basis the evaluation and treatment of SWD and JLD. Physiological assessment has involved determination of circadian phase using core body temperature and the timing of melatonin secretion. Behavioral assessment has involved sleep logs, actigraphy and the Morningness-Eveningness Questionnaire (MEQ). Treatment interventions fall into three broad categories: 1) prescribed sleep scheduling, 2) circadian phase shifting ("resetting the clock"), and 3) symptomatic treatment using hypnotic and stimulant medications.

CONCLUSION

Circadian rhythm science has also pointed the way to rational interventions for the SWD and JLD, and these treatments have been introduced into the practice of sleep medicine with varying degrees of success. More translational research is needed using subjects who meet current diagnostic criteria.

Practice parameters for the clinical evaluation and treatment of circadian rhythm sleep disorders. An American Academy of Sleep Medicine report

The expanding science of circadian rhythm biology and a growing literature in human clinical research on circadian rhythm sleep disorders (CRSDs) prompted the American Academy of Sleep Medicine (AASM) to convene a task force of experts to write a review of this important topic. Due to the extensive nature of the disorders covered, the review was written in two sections. The first review paper, in addition to providing a general introduction to circadian biology, addresses "exogenous" circadian rhythm sleep disorders, including shift work disorder (SWD) and jet lag disorder (JLD). The second review paper addresses the "endogenous" circadian rhythm sleep disorders, including advanced sleep phase disorder (ASPD), delayed sleep phase disorder (DSPD), irregular sleep-wake rhythm (ISWR), and the non-24-hour sleep-wake syndrome (nonentrained type) or free-running disorder (FRD). These practice parameters were developed by the Standards of Practice Committee and reviewed and approved by the Board of Directors of the AASM to present recommendations for the assessment and treatment of CRSDs based on the two accompanying comprehensive reviews. The main diagnostic tools considered include sleep logs, actigraphy, the Morningness-Eveningness Questionnaire (MEQ), circadian phase markers, and polysomnography. Use of a sleep log or diary is indicated in the assessment of patients with a suspected circadian rhythm sleep disorder (Guideline). Actigraphy is indicated to assist in evaluation of patients suspected of circadian rhythm disorders (strength of recommendation varies from "Option" to "Guideline," depending on the suspected CRSD). Polysomnography is not routinely indicated for the diagnosis of CRSDs, but may be indicated to rule out another primary sleep disorder (Standard). There is insufficient evidence to justify the use of MEQ for the routine clinical evaluation of CRSDs (Option). Circadian phase markers are useful to determine circadian phase and confirm the diagnosis of FRD in sighted and unsighted patients but there is insufficient evidence to recommend their routine use in the diagnosis of SWD, JLD, ASPD, DSPD, or ISWR (Option). Additionally, actigraphy is useful as an outcome measure in evaluating the response to treatment for CRSDs (Guideline). A range of therapeutic interventions were considered including planned sleep schedules, timed light exposure, timed melatonin doses, hypnotics, stimulants, and alerting agents. Planned or prescribed sleep schedules are indicated in SWD (Standard) and in JLD, DSPD, ASPD, ISWR (excluding elderly-demented/nursing home residents), and FRD (Option). Specifically dosed and timed light exposure is indicated for each of the circadian disorders with variable success (Option). Timed melatonin administration is indicated for JLD (Standard); SWD, DSPD, and FRD in unsighted persons (Guideline); and for ASPD, FRD in sighted individuals, and for ISWR in children with moderate to severe psychomotor retardation (Option). Hypnotic medications may be indicated to promote or improve daytime sleep among night shift workers (Guideline) and to treat jet lag-induced insomnia (Option). Stimulants may be indicated to improve alertness in JLD and SWD (Option) but may have risks that must be weighed prior to use. Modafinil may be indicated to improve alertness during the night shift for patients with SWD (Guideline).

Prevention and treatment of sleep deprivation among emergency physicians

Emergency physicians commonly experience sleep deprivation because of the need to work shifts during evening and late night hours. The negative effects of this problem are compounded by job stress and traditional methods of scheduling work shifts. Sleep deprivation may be reduced by schedules designed to lessen interference with normal sleep patterns and circadian rhythms. Pharmacological treatments for sleep deprivation exist in the form of alertness-enhancing agents, caffeine and modafinil. Sleep-promoting agents may also help treat the problem by helping physicians to sleep during daytime hours. Minimizing sleep deprivation may help prevent job burnout and prolong the length of an emergency physician's career.

Working on atypical schedules

Shift work has been associated with a number of health problems including cardiovascular disease, impaired glucose and lipid metabolism, gastrointestinal discomfort, reproductive difficulties, and breast cancer. The specific contributions of disturbed physiological rhythms, circadian misalignment, and sleep debt to the various medical problems encountered by shift workers remain to be clarified. Fatigue can be caused by extended on-duty and/or waking periods, inadequate sleep quantity, sleep disturbances, disruption of circadian rhythms, and difficult work and familial conditions. Fatigue-related accidents raise a safety concern for shift workers, especially at the end of the night when the circadian nadir of alertness interacts with increased time awake. Individuals vary greatly in their capacity to adjust to atypical work schedules and their tolerance to circadian misalignment. Predisposing individual and domestic factors have been identified, such as increasing age, being a single woman in charge of children, and split sleep patterns, all of which can affect the ability to adjust to atypical schedules. However, prior studies indicate that predisposing individual and social determinants are generally poor predictors of shift work tolerance in a given individual. In this manuscript, we review several countermeasures to improve adaptation to shift work.

A survey to describe sleep-facilitating substances used by Canadian emergency physicians

BACKGROUND

Because night shifts disrupt the normal circadian rhythm, sleep management is crucial for emergency physicians. The purpose of the survey was to describe the use of sleep-facilitating substances (SFSs) by emergency physicians before or after a night shift and to evaluate factors associated with their use.

METHODS

All members of the Canadian Association of Emergency Physicians with a Canadian postal address were mailed a copy of the survey. Canadian physicians were eligible if they worked at least one night shift per month and spent 50% or more of their time in emergency medicine. Logistic regression was used to identify characteristics most predictive of using SFSs before or after a night shift.

RESULTS

Of the 1621 surveys mailed, 805 were returned completed, for a response rate of 49.6%. Of these, 628 respondents met inclusion criteria and 215 respondents (34%) reported consuming at least one SFS in their career to help them sleep around a night shift. The use of an SFS before a night shift was associated with the use of SFSs after a night shift (odds ratio [OR] 3.8; 95% confidence interval [CI] 2.4-5.9) and the use of SFSs at other times (OR 3.8; 95% CI 2.1-6.6). The use of SFSs after a night shift was associated with the use of a sleep-facilitating technique before a night shift (OR 2.1; 95% CI 1.3-3.3); use of an SFS before a night shift (OR 4.0; 95% CI 2.4-6.4); use of SFSs at other times (OR 4.7; 95% CI 2.6-8.4); and success of a nap before the night shift (OR 0.46; 95% CI 0.25-0.83).

CONCLUSION

The rate of SFS use is similar in emergency physicians and other shift workers. Emergency physicians who use SFSs before or after a night shift are more likely to use them at other times as well, and less likely to use them if they nap successfully prior to a night shift.

Circadian rhythm sleep disorders and phototherapy

Circadian rhythm sleep disorders are characterized by a desynchronization between the timing of the intrinsic circadian clock and the extrinsic light-dark and social/activity cycles resulting in symptoms of excessive sleepiness and insomnia. This article explores the six recognized circadian rhythm sleep disorders: delayed sleep phase syndrome, advanced sleep phase syndrome, non-24-hour sleep-wake syndrome, irregular sleep-wake pattern, shift work sleep syndrome, and time zone change syndrome. Additionally discussed are the therapeutic roles of synchronizing agents, such as light and melatonin.

Efficacy and safety of exogenous melatonin for secondary sleep disorders and sleep disorders accompanying sleep restriction: meta-analysis

OBJECTIVE

To conduct a systematic review of the efficacy and safety of exogenous melatonin in managing secondary sleep disorders and sleep disorders accompanying sleep restriction, such as jet lag and shiftwork disorder.

DATA SOURCES

13 electronic databases and reference lists of relevant reviews and included studies; Associated Professional Sleep Society abstracts (1999 to 2003).

STUDY SELECTION

The efficacy review included randomised controlled trials; the safety review included randomised and non-randomised controlled trials.

QUALITY ASSESSMENT

Randomised controlled trials were assessed by using the Jadad Scale and criteria by Schulz et al, and non-randomised controlled trials by the Downs and Black checklist.

DATA EXTRACTION AND SYNTHESIS

One reviewer extracted data and another reviewer verified the data extracted. The inverse variance method was used to weight studies and the random effects model was used to analyse data.

MAIN RESULTS

Six randomised controlled trials with 97 participants showed no evidence that melatonin had an effect on sleep onset latency in people with secondary sleep disorders (weighted mean difference -13.2 (95% confidence interval -27.3 to 0.9) min). Nine randomised controlled trials with 427 participants showed no evidence that melatonin had an effect on sleep onset latency in people who had sleep disorders accompanying sleep restriction (-1.0 (-2.3 to 0.3) min). 17 randomised controlled trials with 651 participants showed no evidence of adverse effects of melatonin with short term use (three months or less).

CONCLUSIONS

There is no evidence that melatonin is effective in treating secondary sleep disorders or sleep disorders accompanying sleep restriction, such as jet lag and shiftwork disorder. There is evidence that melatonin is safe with short term use.

Ritmo circadiano e doença vascular encefálica: um estudo de correlação com fatores de risco

Os mecanismos biológicos humanos exibem variabilidade clínica previsível no tempo, o que tem permitido reavaliação das práticas médicas atuais, do estudo mais aprofundado do ritmo circadiano (RC) e dos mecanismos que geram as oscilações sustentadas em todos os níveis biológicos. Fizemos um estudo procurando relacionar o RC e o momento do aparecimento do quadro clínico neurológico decorrente da lesão vascular do encéfalo com os fatores de risco modificáveis identificados no momento da internação. Foram estudados 53 pacientes, sendo 50,94% (n =27) do sexo feminino e 49,50%(n =26) do masculino, com média de idade de 66,4 anos. Quatro intervalos de 6 horas (0-6; 6-12; 12-18; 18-24) foram usados para análise da freqüência do ictus e da incidência em cada intervalo. Os resultados mostraram 6 (11,32%) pacientes no intervalo 0-6 hs; 21 (39,62%) no intervalo 6-12 hs; 10 (18,86%) no intervalo 12-18 hs; 16 (30,18%) no intervalo 18-24 hs. Estudo de correlação com os fatores de risco, baseado nos dados clínicos no momento da internação, mostrou que a hipertensão arterial [(81,25%)] e o tabagismo[ (56,25%)] predominaram no intervalo 18-24 hs, enquanto o sedentarismo[11; (52,38%)] o estresse[11 (52,38%)] o diabetes [(47,61%)] a hiperlipidemia [8 (38,09%)] e o alcoolismo[8 (38,09%)] predominaram no intervalo 6-12 hs; as cardiopatias [(50,00%)] predominaram no intervalo de 12-18 hs.

Role of morning melatonin administration and attenuation of sunlight exposure in improving adaptation of night-shift workers

The authors studied whether melatonin administration improves adaptation of workers to nightshift and if its beneficial effect is enhanced by attenuation of morning sunlight exposure. Twelve nightshift nurses received three treatments: Placebo (Pla), Melatonin (Mel), and Melatonin with Sunglasses (Mel-S). Each treatment procedure was administered for 2d of different 4d nightshifts in a repeated measures crossover design. In Pla, nurses were treated with placebo before daytime sleep and allowed exposure to morning sunlight. In Mel, 6mg of melatonin was similarly administered before daytime sleep with morning sunlight permitted. In Mel-S, 6 mg of melatonin was given as in Mel, with sunglasses worn in the morning to attenuate sunlight exposure. Placebo or melatonin was administered during days 2 and 3 when the first and second daytime sleep occurred. Nocturnal alertness and performance plus daytime sleep and mood states were assessed during all three treatments. The sleep period and total sleep times were significantly increased by melatonin treatments; yet, nocturnal alertness was only marginally improved. There were no differences between Mel and Mel-S. Performance tests revealed no difference between Pla and melatonin treatments. Melatonin exerted modest benefit in improving the adaptation of workers to nightshift, and its effect was not enhanced by attenuation of morning sunlight exposure.

Melatonin phase shifts human circadian rhythms in a placebo-controlled simulated night-work study

There has been scant evidence for a phase-shifting effect of melatonin in shift-work or jet-lag protocols. This study tested whether melatonin can facilitate phase shifts in a simulated night-work protocol. Subjects (n = 32) slept in the afternoons/evenings before night work (a 7-h advance of the sleep schedule). They took melatonin (0.5 mg or 3.0 mg) or placebo before the first four of eight afternoon/evening sleep episodes at a time when melatonin has been shown to phase advance the circadian clock. Melatonin produced larger phase advances than placebo in the circadian rhythms of melatonin and temperature. Average phase advances (+/-SD) of the dim light melatonin onset were 1.7 +/- 1.2 h (placebo), 3.0 +/- 1.1 h (0.5 mg), and 3.9 +/- 0.5 h (3.0 mg). A measure of circadian adaptation, shifting the temperature minimum enough to occur within afternoon/evening sleep, showed that only subjects given melatonin achieved this goal (73% with 3.0 mg, 56% with 0.5 mg, and 0% with placebo). Melatonin could be used to promote adaptation to night work and jet travel.

Effects of melatonin administration on daytime sleep after simulated night shift work

Disturbed sleep and on-the-job sleepiness are widespread problems among night shift workers. The pineal hormone melatonin may prove to be a useful treatment because it has both sleep-promoting and circadian phase-shifting effects. This study was designed to isolate melatonin's sleep-promoting effects, and to determine whether melatonin could improve daytime sleep and thus improve night time alertness and performance during the night shift. The study utilized a placebo-controlled, double-blind, cross-over design. Subjects (n=21, mean age=27.0 +/- 5.0 years) participated in two 6-day laboratory sessions. Each session included one adaptation night, two baseline nights, two consecutive 8-h night shifts followed by 8-h daytime sleep episodes and one recovery night. Subjects took 1.8 mg sustained-release melatonin 0.5 h before the two daytime sleep episodes during one session, and placebo before the daytime sleep episodes during the other session. Sleep was recorded using polysomnography. Sleepiness, performance, and mood during the night shifts were evaluated using the multiple sleep latency test (MSLT) and a computerized neurobehavioral testing battery. Melatonin prevented the decrease in sleep time during daytime sleep relative to baseline, but only on the first day of melatonin administration. Melatonin increased sleep time more in subjects who demonstrated difficulty in sleeping during the day. Melatonin had no effect on alertness on the MSLT, or performance and mood during the night shift. There were no hangover effects from melatonin administration. These findings suggest that although melatonin can help night workers obtain more sleep during the day, they are still likely to face difficulties working at night because of circadian rhythm misalignment. The possibility of tolerance to the sleep-promoting effects of melatonin across more than 1 day needs further investigation.

Circadian rhythm, shift work, and emergency medicine

Human beings, like other living organisms, have physiologic systems that are cyclic in nature. Many of these systems have a circadian length. This provides for internal stability while at the same time enabling the organism to interact with the external environment and respond to changes in that environment. These physiologic systems, including those with a circadian length, can change timing as a result of environmental cues, such as the light-dark cycle or seasonal variations, but this takes time. When people engage in rotating or night shift work, the circadian rhythms are unable to quickly adapt to a rapidly changing activity schedule. This results in desynchronosis of many physiologic systems, including those with circadian timing. Because many emergency physicians engage in shift work, they are subject to the effects of circadian rhythm disruption. Research on the effect of desynchronosis on emergency physicians is sparse but has demonstrated negative effects. This article reviews the effect of desynchronosis on the health and productivity of physicians engaged in shift work.

Effect of exogenous melatonin on mood and sleep efficiency in emergency medicine residents working night shifts

OBJECTIVE

To determine whether melatonin taken prior to attempted daytime sleep sessions will improve daytime sleep quality, nighttime sleepiness, and mood state in emergency medicine (EM) residents, changing from daytime to nighttime work schedules.

METHODS

A prospective, randomized, double-blind crossover design was used in an urban emergency department. Emergency medicine residents who worked two strings of nights, of at least three nights' duration each, and separated by at least one week of days were eligible. Subjects were randomized to receive either melatonin 1 mg or placebo, 30 to 60 minutes prior to their daytime sleep session, for three consecutive days after each night shift. Crossover to the other agent occurred during their subsequent night shifts. Objective measures of quality of daytime sleep were obtained using the Actigraph 1000. This device measures sleep motion and correlates with sleep efficiency, total sleep time, time in bed, and sleep latency. The Profile of Mood States (POMS) and the Stanford Sleepiness Scale (SSS) were also used to quantify nighttime mood and sleepiness.

RESULTS

Among the 19 volunteers studied, there was no difference in sleep efficiency (91.16% vs 90.98%, NS), sleep duration (379.6 min vs 342.7 min, NS), or sleep latency (7.59 min vs 6.80 min, NS), between melatonin and placebo, respectively. In addition, neither the POMS total mood disturbance (5.769 baseline vs 12.212 melatonin vs 5.585 placebo, NS) nor the SSS (1.8846 baseline vs 2.2571 melatonin vs 2.1282 placebo, NS) demonstrated a statistical difference in nighttime mood and sleepiness between melatonin and placebo.

CONCLUSIONS

There are no beneficial effects of a 1-mg melatonin dose on sleep quality, alertness, or mood state during night shift work among EM residents.

What can the chronobiologist do to help the shift worker?

This article is composed of a review of how the increasing numbers of people working abnormal hours (referred to as "shift workers") can best be helped by the science of chronobiology. While recognizing that chronobiologists can give much general advice regarding such things as diet, sleep hygiene, cardiovascular health, and the need to address social and domestic tensions, this article will focus specifically on the advice that can be given to employers and employees, which is directly rooted in our knowledge of chronobiology.

Sleep-wake cycle, sleep-related disturbances, and sleep disorders: a chronobiological approach

There is convincing evidence that the functions of sleep include restoration of brain energy storage and memory consolidation. The circadian timing system (CTS) is involved in the daily variation of almost any physiological and psychological variable evaluated thus far. Disturbances of the CTS can be clinically observed by their influence on the sleep-wake cycle, hormones, body temperature, and locomotor activity. This article reviews the basic mechanisms of circadian rhythm sleep disturbances, names the applicable diagnostic tools and specific therapeutic strategies, and thereby hints at the impact of circadian rhythm sleep disturbance on psychiatric disorders, especially disorders of affect and cognition. In light of the preventive, diagnostic, and therapeutic tools now available, a new round of chronobiological studies in psychiatry seems justified, promising, and necessary.