Hypnotics and caffeine as countermeasures for shiftwork-related sleepiness and sleep disturbance

Pharmacokinetic and pharmacodynamic herb-drug interactions-part I. Herbal medicines of the central nervous system

Unlike conventional drug substances, herbal medicines are composed of a complex of biologically active compounds. Therefore, the potential occurrence of herb-drug interactions is even more probable than for drug-drug interactions. Interactions can occur on both the pharmacokinetic and pharmacodynamic level. Herbal medicines may affect the resulting efficacy of the concomitantly used (synthetic) drugs, mainly on the pharmacokinetic level, by changing their absorption, distribution, metabolism, and excretion. Studies on the pharmacodynamic interactions of herbal medicines and conventional drugs are still very limited. This interaction level is related to the mechanism of action of different plant constituents. Herb-drug interactions can cause changes in drug levels and activities and lead to therapeutic failure and/or side effects (sometimes toxicities, even fatal). This review aims to provide a summary of recent information on the potential drug interactions involving commonly used herbal medicines that affect the central nervous system (Camellia, Valeriana, Ginkgo, Hypericum, Humulus, Cannabis) and conventional drugs. The survey databases were used to identify primary scientific publications, case reports, and secondary databases on interactions were used later on as well. Search keywords were based on plant names (botanical genera), officinal herbal drugs, herbal drug preparations, herbal drug extracts.

Recovery from shift work

One fifth of today's workforce is engaged in shift work and exposed to various mental and physical health risks including shift work disorder. Efficiently recovering from shift work through physical and mental interventions allows us to mitigate negative effects on health, enables a better work-life balance and enhances our overall wellbeing. The aim of this review is to provide a state-of-the-art overview of the available literature. The role of sleep timing and naps, light therapy and psychotherapy, diet and exercise in recovery from shift work is presented here. We further review the impact of shift schedules and social support on post-shift unwinding.

Circadian Rhythm Sleep-Wake Disorders in Older Adults

The timing, duration, and consolidation of sleep result from the interaction of the circadian timing system with a sleep-wake homeostatic process. When aligned and functioning optimally, this allows for wakefulness throughout the day and a long consolidated sleep episode at night. Changes to either the sleep regulatory process or how they interact can result in an inability to fall asleep at the desired time, difficulty remaining asleep, waking too early, and/or difficulty remaining awake throughout the day. This mismatch between the desired timing of sleep and the ability to fall asleep and remain asleep is a hallmark of a class of sleep disorders called the circadian rhythm sleep-wake disorders. In this updated article, we discuss typical changes in the circadian regulation of sleep with aging; how age influences the prevalence, diagnosis, and treatment of circadian rhythm sleep disorders; and how neurologic diseases in older patient impact circadian rhythms and sleep.

Demographics, sleep, and daily patterns of caffeine intake of shift workers in a nationally representative sample of the US adult population

STUDY OBJECTIVE

Caffeine is the most widely consumed stimulant in the world, and sociodemographic factors including occupation are associated with intake. Shift work, required in various occupations, is associated with poor sleep, inadequate diet, and adverse health effects. Using a large nationally representative database, demographics, sleep, and caffeine intake of US adults working various shifts were assessed.

METHODS

The 24-hour dietary recall data from NHANES 2005-2010 (N = 8,500) were used to estimate caffeine intake from foods and beverages. Work shifts were self-reported as follows: regular day shift; evening shift; night shift; rotating shift; or other shift. Regression analyses assessed associations of shift work with caffeine intake after adjustment for sociodemographic factors.

RESULTS

Approximately 74% of employed adults were day-shift workers and 26% were nonday-shift workers. Night-shift workers slept for 6.25 ± 0.09 hours per day, somewhat less than day-shift workers who only slept 6.83 ± 0.02 hours (p < .0001). Mean 24-hour weekday caffeine intake of evening-, night-, and rotating-shift workers (217 ± 23, 184 ± 19, and 206 ± 15 mg, respectively) was similar (p > .3) to day-shift workers (203 ± 5 mg). Regardless of work schedule, individuals consumed the most caffeine during morning hours. Evening- and night-shift workers reported consuming 36%-46% less caffeine during their work hours and 72%-169% more during nonwork hours than day-shift workers (p < .01).

CONCLUSIONS

Total daily caffeine intake of shift workers is similar to nonshift workers; most caffeine is consumed in the morning regardless of shift. Because shift workers consume less caffeine during regular work hours and more during nonwork hours than day workers, they may be using caffeine to, in part, optimize off-duty alertness.

Sleep-Related Problems in Night Shift Nurses: Towards an Individualized Interventional Practice

Rotating shifts (mostly 8- or 12-h) are common among nurses to ensure continuity of care. This scheduling system encompasses several adverse health and performance consequences. One of the most injurious effects of night-time shift work is the deterioration of sleep patterns due to both circadian rhythm disruption and increased sleep homeostatic pressure. Sleep problems lead to secondary effects on other aspects of wellbeing and cognitive functioning, increasing the risk of errors and workplace accidents. A wide range of interventions has been proposed to improve the sleep quality of nurses and promote an increase in attention levels. In recent years, particular attention has been paid to individual and environmental factors mediating the subjective ability to cope with sleep deprivation during the night shift. Given the predictive role of these factors on the negative impact of a night shift, an individualized intervention could represent an effective countermeasure by ensuring suitable management of shift schedules. Therefore, the aims of this mini-review are to: (a) provide an updated overview of the literature on sleep problems in night shift nurses and their adverse consequences; and (b) critically analyze the psychosocial factors that mediate the negative impact of shift work with the ultimate goal of defining an effective countermeasure based on an individualized approach.

Sleep hygiene in shift workers: A systematic literature review

In response to demand for the '24/7' service availability, shift work has become increasingly common. Given their non-traditional working hours, shift workers sleep at non-traditional times, with significant research undertaken to understand shift worker sleep. However, sleep hygiene in shift workers has been paid little research attention. To investigate shift worker engagement with sleep hygiene, a systematic review using the databases Sage, ScienceDirect, and Scopus was undertaken. The search terms utilised were: shift work, shiftwork, shift-work, sleep hygiene, sleep routine, and sleep habit. Sixteen studies were included for review. Findings show that shift workers frequently report caffeine consumption and daytime napping, in line with best-practice fatigue-management strategies, but contrary to existing sleep hygiene recommendations. Shift workers also altered their bedroom environment to optimise sleep. Diet, exercise, alcohol and nicotine consumption were investigated minimally from a sleep hygiene perspective. Given that shift workers are engaging in practices in-line with current fatigue-management strategies, but contrary to sleep hygiene recommendations, further research is required. Specifically, assessment of the applicability of current sleep hygiene guidelines to shift workers (particularly caffeine and napping recommendations) is required, in addition to the development of shift work-specific sleep hygiene guidelines and interventions for this sleep-vulnerable population.

Intraperitoneal injection of ginkgolide B, a major active compound of Ginkgo biloba, dose-dependently increases the amount of wake and decreases non-rapid eye movement sleep in C57BL/6 mice

The terpene lactones of Ginkgo biloba extract, namely ginkgolides (A, B, and C) and bilobalide, possess antioxidant, anti-inflammatory, and neuroprotective effects. They are widely prescribed for the treatment of cerebral dysfunctions and neurological impairments. In addition, they demonstrate antagonistic action at the gamma-aminobutyric acid type A and glycine receptors, which are members of the ligand-gated ion channel superfamily. In the present study, the effects of ginkgolides (A, B, and C) and bilobalide on sleep in C57BL/6 mice were investigated. Ginkgolide B was found to dose-dependently increase the amount of wake and decrease that of non-rapid eye movement sleep without changes in the electroencephalography power density of each sleep/wake stage, core body temperature and locomotor activity for the first 6 h after intraperitoneal injection. Of note, the amount of wake after injection of 5 mg/kg of ginkgolide B showed a significant increase (14.9 %) compared with that of vehicle (P = 0.005). In contrast, there were no significant differences in the amount of sleep, core body temperature, and locomotor activity in the mice injected with ginkgolide A and C. Bilobalide briefly induced a decrease in locomotor activity but did not exert significant effects on the amounts of sleep and wake. The modes of action of the wake-enhancing effects of ginkgolide B are unknown. However, it may act through the antagonism of gamma-aminobutyric acid type A and glycine receptors because it is established that these inhibitory amino acids mediate sleep and sleep-related physiology. It is of interest to further evaluate the stimulant and awaking actions of ginkgolide B on the central nervous system in clinical and basic research studies.

Narcolepsy in Children and Adults: A Guide to Improved Recognition, Diagnosis and Management

Narcolepsy is a rare condition that affects children and adults, and commonly has an onset in childhood. Time to appropriate diagnosis frequently is at least a decade. Unrecognized or misdiagnosed symptoms of narcolepsy contribute to increased morbidity, disability and socioeconomic liability in these patients. Delays in diagnosis may be related to variability in presentation in childhood, lack of familiarity with symptoms or appropriate diagnostic testing or misdiagnosis with accidental introduction of treatment that may modify or mask narcolepsy features. Improved awareness about the diagnosis and tailored therapies improve clinical and socioeconomic outcomes by reducing time to effective treatment. Application of effective treatment results in long-term benefits by improving clinical outcomes, potentially enabling improved education, increased employment opportunity, and improved work productivity and quality of life. This review provides a comprehensive stepwise approach to improve knowledge and comfort for recognition of symptoms, diagnostic strategies and management considerations of narcolepsy in children and adults.

Shift Work and Lifestyle Factors: A 6-Year Follow-Up Study Among Nurses

Objectives: To evaluate different work schedules, short rest time between shifts (quick returns), and night shift exposure for their possible adverse effects on different lifestyle factors in a 6-year follow-up study.

Methods: Data stemmed from “The Survey of Shiftwork, Sleep and Health,” a cohort study of Norwegian nurses started in 2008/9. The data analyzed in this sub-cohort of SUSSH were from 2008/9 to 2015 and consisted of 1,371 nurses. The lifestyle factors were: Exercise (≥1 h/week, <1 h/week), caffeine consumption (units/day), smoking (prevalence and cigarettes/day), and alcohol consumption (AUDIT-C score). We divided the nurses into four groups: (1) day workers, (2) night workers, (3) nurses who changed toward, and (4) nurses who changed away from a schedule containing night shifts. Furthermore, average number of yearly night shifts (NN), and average number of quick returns (QR) were calculated. Paired t-tests, McNemar tests, and logistic regression analyses were used in the analyses.

Results: We found a significant increase in caffeine consumption across all work schedule groups and a decline in smoking prevalence for day workers and night workers at follow-up. Analyses did not show any significant differences between groups when analyzing (1) different work schedules, (2) different exposures to QR, (3) different exposures to NN on the respective lifestyle factor trajectories.

Conclusion: We found no significant differences between the different work schedule groups or concerning different exposures to QR or NN when evaluating these lifestyle factor trajectories. This challenges the notion that shift work has an adverse impact on lifestyle factors.

Circadian-Rhythm Sleep Disorders in Persons who are Totally Blind

People who are totally blind are prone to a cyclic form of insomnia, designated in medical terminology as non-24-hour sleep-wake syndrome. It is caused by a lack of synchrony between the internal body clock and the daily sleep-wake schedule. This article describes the clinical features and biological basis of the disorder and discusses the implications for its management and treatment.

Shift Work Disorder

Shift work and its negative consequences are becoming more relevant as the economy becomes increasing globalized. For many individuals, shift work serves as a significant biological and psychosocial challenge leading to Shift Work Disorder (SWD). Beyond the symptoms of sleep and excessive sleepiness, the range of consequences for health and daily functioning in those with SWD are reviewed, along with evidence-based recommendations for clinical management, including comprehensive clinical assessments and intervention strategies that target multiple domains through pharmacologic and nonpharmacologic methods. A review of important recent scientific and technological developments for assessment and intervention is also provided.

Occupational Sleep Medicine

Sleep and circadian rhythms significantly impact almost all aspects of human behavior and are therefore relevant to occupational sleep medicine, which is focused predominantly around workplace productivity, safety, and health. In this article, 5 main factors that influence occupational functioning are reviewed: (1) sleep deprivation, (2) disordered sleep, (3) circadian rhythms, (4) common medical illnesses that affect sleep and sleepiness, and (5) medications that affect sleep and sleepiness. Consequences of disturbed sleep and sleepiness are also reviewed, including cognitive, emotional, and psychomotor functioning and drowsy driving.

Thalamic Circuit Mechanisms Link Sensory Processing in Sleep and Attention

The correlation between sleep integrity and attentional performance is normally interpreted as poor sleep causing impaired attention. Here, we provide an alternative explanation for this correlation: common thalamic circuits regulate sensory processing across sleep and attention, and their disruption may lead to correlated dysfunction. Using multi-electrode recordings in mice, we find that rate and rhythmicity of thalamic reticular nucleus (TRN) neurons are predictive of their functional organization in sleep and suggestive of their participation in sensory processing across states. Surprisingly, TRN neurons associated with spindles in sleep are also associated with alpha oscillations during attention. As such, we propose that common thalamic circuit principles regulate sensory processing in a state-invariant manner and that in certain disorders, targeting these circuits may be a more viable therapeutic strategy than considering individual states in isolation.

Tick-tock-tick-tock: the impact of circadian rhythm disorders on cardiovascular health and wellness

Humans spend a third of their lives asleep. A well-balanced synchrony between sleep and wakefulness is needed to maintain a healthy lifestyle. Optimal sleep is based on an individual's inherent sleep requirement and circadian rhythm. If either one or both of these critical elements are disrupted, daytime dysfunction, non-restorative sleep, and/or reduced sense of well-being may result. While the medical community is more familiar with sleep disorders such as sleep apnea, insomnia, and narcolepsy, circadian rhythm sleep wake disorders (CRSWDs) are less known, despite these being common within the general population. CRSWDs are comprised of the following: shiftwork disorder, delayed sleep phase disorder, advanced sleep phase disorder, jet lag disorder, non-24-hour sleep-wake disorder, and irregular sleep-wake rhythm disorder. In general, a CRSWD results when there is misalignment between the sleep pattern and the desired sleep schedule, dictated by work, family, and social schedules. Subsequently, patients have difficulty falling asleep, maintaining sleep, and/or experience poor quality sleep predisposing them to insomnia or excessive sleepiness. In this article, we review the core concepts related to sleep, and sleep deprivation in the context of CRSWDs.

Sleep and fatigue countermeasures for the neurology resident and physician

PURPOSE OF REVIEW

Fragmented sleep, prolonged work hours, misalignment of sleep-wake cycles, and an expectation to make medical decisions when alertness levels are reduced are pervasive in neurology residency training. Sleep loss in residency training can lead to cognitive and psychosocial impairment and accidents, compromise patient care, and reduce the trainee's quality of life. Neurology residents experience levels of hypersomnolence similar to residents in surgical specialties and have comparable subjective levels of sleepiness as persons with pathologic sleep disorders such as narcolepsy and obstructive sleep apnea. Over the past 2 decades, work-hour limitations were established to alleviate fatigue and sleepiness. However, the implementation of work-hour limitations alone does not guarantee alleviation of fatigue and may be insufficient without additional key measures to prevent, counteract, and control sleepiness when it strikes. This article provides effective strategies to combat sleepiness, such as modification of the on-call structure (night float), power naps, and caffeine, in neurologists in training and those who are at risk for excessive sleepiness.

RECENT FINDINGS

Despite two specific work-hour restrictions set by the Accreditation Council for Graduate Medical Education, the most recent in July 2011, little data exist about the efficacy of work-hour restrictions alone in improving fatigue and sleepiness. Curtailed work hours, while appearing attractive on the surface, have important financial, educational, and patient care imperfections and fail to address the core issue--sleepiness.

SUMMARY

Historically, sleepiness and fatigue place both residents and patients at risk. Excessive sleepiness in residency training occurs because of sleep deprivation and a spectrum of other factors, such as mood disorders or even the anxiety of anticipating being woken up. An effective model to counteract sleep deprivation and its consequences is a multiplayer approach that uniquely targets and addresses the needs of all the stakeholders. A sleep medicine perspective is proposed along with other interventions to prevent adverse consequences.

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.

Baseline sleep dysfunction among matriculating interns

BACKGROUND

Work hour limitations for graduate medical trainees, motivated by concerns about patient safety, quality of care, and trainee well-being, continue to generate controversy. Little information about sleep habits and the prevalence of sleep disorders among residents is available to inform policy in this area.

OBJECTIVES

To evaluate the sleep habits of matriculating residents, postgraduate year-1 (PGY-1).

DESIGN

An anonymous, voluntary, self-administered survey study was used with 3 validated questionnaires: the Pittsburgh Sleep Quality Index, the Insomnia Severity Index, and the Epworth Sleepiness Scale, which were fielded to PGY-1 residents entering the Accreditation Council for Graduate Medical Education-accredited programs at Massachusetts General Hospital and/or Brigham and Women's Hospitals in June and July 2009.

RESULTS

Of 355 eligible subjects, 310 (87%) participated. Mean sleep time for PGY-1 residents was 7 hours and 34 minutes, and 5.6% of PGY-1 residents had Pittsburgh Sleep Quality Index global scores greater than 5, indicating poor quality sleep. Using multiple linear and ordinal logistic regression models, men had higher Pittsburgh Sleep Quality Index sleep latency scores, whereas women and those with children had higher Epworth Sleepiness Scale daytime sleepiness scores, and 18% of PGY-1 residents had abnormal amounts of daytime sleepiness based on the Epworth Sleepiness Scale. The Insomnia Severity Index identified 4.2% of PGY-1 residents with moderate insomnia.

CONCLUSIONS

Some PGY-1 residents may begin residency with sleep dysfunctions. Efforts to provide targeted help to selected trainees in managing fatigue during residency should be investigated.

Sleep, stress and compensatory behaviors in Australian nurses and midwives

OBJECTIVE: To describe sleep, stress and compensatory behaviors in nurses and midwives. METHODS: The study included 41 midwives and 21 nurses working in Australian hospitals between 2005 and 2009. Participation was voluntary. All participants recorded on a daily basis their work and sleep hours, levels of stress and exhaustion, caffeine intake and use of sleep aids for a month (1,736 days, 1,002 work shifts). RESULTS: Participants reported moderate to high levels of stress and exhaustion on 20-40% of work days; experienced sleep disruption on more than 50% of work days; struggled to remain awake on 27% of work days; and suffered extreme drowsiness or experienced a near accident while travelling home on 9% of workdays. Age, perceived sleep duration and work hours were significant predictors of caffeine intake. About 60% of participants reported using sleep aids (about 20% reported taking prescription medications and 44% of nurses and 9% of midwives reported alcohol use as a sleep aid at least once during the study). Stress and workdays were significant predictors of sedative use. Overall, 22% reported being indifferent or mildly dissatisfied with their job. CONCLUSIONS: Sleep problems, high levels of stress and exhaustion and low job satisfaction are prevalent among nurses and midwives. The use of alcohol and sleeping pills as sleep aids, and the use of caffeine to help maintain alertness is also common. Nurses and midwives may use caffeine to compensate for reduced sleep, especially on workdays, and sleeping pills to cope with their daily work-related stress.

Expert opinion on pharmacotherapy of narcolepsy

IMPORTANCE TO THE FIELD

Narcolepsy is a neurodegenerative disorder resulting in the instability of the sleep-wake cycle and marked by low levels of hypocretin in cerebrospinal fluid. Sleep instability is marked by brisk, sleep-onset REM periods and sleep fragmentation, while the waking state is interrupted by the intrusion of REM sleep and sometimes accompanied by cataplectic attacks.

AREAS COVERED IN THIS REVIEW

Current pharmacologic interventions that aim to address three primary features of this disorder; excessive daytime sleepiness (EDS), cataplexy and automatic behaviors, and sleep fragmentation. We review and compare the use of traditional and new stimulants in the treatment of EDS. For the treatment of cataplexy and automatic behaviors, serotonergic and noradrenergic agents are considered. The role of gamma-hydroxybutyrate (GHB) is also explored in its ability to reduce daytime sleepiness and catapletic attacks and to consolidate sleep. Findings are based on a PubMed literature search of clinical and basic science research papers spanning 1977-2009.

WHAT THE READER WILL GAIN

A comprehensive understanding of the various existing and promising future treatments for narcolepsy. For each of these treatments, we evaluate risks versus benefits of treatment, and proposed pharmacologic mechanisms of action. We conclude with a review of new treatment approaches, including thyrotropin-releasing hormone (TRH), histamine agonists, immunotherapy and hypocretin replacement therapies.

TAKE HOME MESSAGE

Narcolepsy is an autoimmune, neurodegenerative disorder that results in significant sleep-wake instability with or without cataplectic attacks. Current treatments aim symptomatically to reconsolidate the sleep and waking states and to reduce daytime attacks of cataplexy. Future treatments aim primarily towards correcting the causal deficiency of hypocretin or preventing the autoimmune response that results in the loss of hypocretin cells.

Sleep Loss and Fatigue in Shift Work and Shift Work Disorder

Shift work is highly prevalent in industrialized societies (>20%) but, when it includes night work, it has pronounced negative effects on sleep, subjective and physiological sleepiness, performance, accident risk, as well as on health outcomes such as cardiovascular disease and certain forms of cancer. The reason is the conflict between the day oriented circadian physiology and the requirement for work and sleep at the "wrong" biological time of day. Other factors that negatively impact work shift sleepiness and accident risk include long duration shifts greater than 12 hours and individual vulnerability for phase intolerance that may lead to a diagnosis of shift work disorder; i.e., those shift workers with the greatest sleepiness and performance impairment during the biological night and insomnia during the biological day. Whereas some countermeasures may be used to ameliorate the negative impact of shift work on nighttime sleepiness and daytime insomnia (combined countermeasures may be the best available), there seems at present to be no way to eliminate most of the negative effects of shift work on human physiology and cognition.

Practical interventions to promote circadian adaptation to permanent night shift work: study 4

Scheduled bright light and darkness can phase shift the circadian clocks of night workers for complete adaptation to a night work, day sleep schedule, but few night workers would want this because it would leave them out of phase with the diurnal world on days off. This is the final study in a series designed to produce a compromise circadian phase position for permanent night shift work in which the sleepiest circadian time is delayed out of the night work period and into the first half of the day sleep episode. The target compromise phase position was a dim light melatonin onset (DLMO) of 3:00, which puts the sleepiest circadian time at approximately 10:00. This was predicted to improve night shift alertness and performance while permitting sufficient daytime sleep after work as well as late-night sleep on days off. In a between-subjects design, 19 healthy subjects underwent 3 simulated night shifts (23:00-7:00), 2 days off, 4 more night shifts, and 2 more days off. Subjects "worked" in the lab and slept at home. Experimental subjects received four 15-min bright light pulses during each night shift, wore dark sunglasses when outside, slept in dark bedrooms at scheduled times, and received outdoor afternoon light exposure ("light brake") to keep their rhythms from delaying too far. Control subjects remained in normal room light during night shifts, wore lighter sunglasses, and had unrestricted sleep and outdoor light exposure. The final DLMO of the experimental group was 3:22 +/- 2.0 h, close to the target of 3:00, and later than the control group at 23:24 +/- 3.8 h. Experimental subjects slept for nearly all the permitted time in bed. Some control subjects who slept late on weekends also reached the compromise phase position and obtained more daytime sleep. Subjects who phase delayed (whether in the experimental or control group) close to the target phase performed better during night shifts. A compromise circadian phase position improved performance during night shifts, allowed sufficient sleep during the daytime after night shifts and during the late nighttime on days off, and can be produced by inexpensive and feasible interventions.

Some chronobiological and physiological problems associated with long-distance journeys

Long-distance travel is becoming increasingly common. Whatever the means of transport, any long journey will be associated with "travel fatigue". The symptoms associated with this phenomenon result from a changed routine (particularly sleep lost and meals) and the general disruption caused by travel. Planning any trip well in advance will minimise many of these problems, but some factors are less easy to guard against. These problems include sitting in cramped and uncomfortable conditions and, with flights, the hypoxic environment in the cabin. After arrival at the destination in another country, there can be problems coping with the local language, alterations in food and different customs. If the flight has crossed the equator, then there is likely to be a change in season and natural lighting and, if it has crossed several time zones, there will also be the problem of "jet lag", caused by a transient desynchrony between the "body clock" and the new local time. Moreover, the new environment might differ from the place of departure with regard to ambient temperature and humidity, altitude, natural lighting (including ultraviolet radiation) and pollution. The traveller needs to be aware of these changes before setting off, so that appropriate preparations (clothing, for example) can be made.

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.

Sleep disorders, sleepiness and traffic safety: a public health menace

Sleep disorders are not uncommon and have been widely reported throughout the world. They have a profound impact on industrialized 24-h societies. Consequences of these problems include impaired social and recreational activities, increased human errors, loss of productivity, and elevated risk of accidents. Conditions such as acute and chronic insomnia, sleep loss, excessive sleepiness, shift-work, jet lag, narcolepsy, and sleep apnea warrant public health attention, since residual sleepiness during the day may affect performance of daily activities such as driving a car. Benzodiazepine hypnotics and zopiclone promote sleep, both having residual effects the following day including sleepiness and reduced alertness. In contrast, the non-benzodiazepine hypnotics zolpidem and zaleplon have no significant next-day residual effects when taken as recommended. Research on the effects of wakefulness-promoting drugs on driving ability is limited. Countermeasures for excessive daytime sleepiness have a limited effect. There is a need for a social awareness program to educate the public about the potential consequences of various sleep disorders such as narcolepsy, sleep apnea, shift-work-related sleep loss, and excessive daytime sleepiness in order to reduce the number of sleep-related traffic accidents.

A clinical approach to circadian rhythm sleep disorders

Circadian rhythm sleep disorders are characterized by complaints of insomnia and excessive 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. In addition to physiological and environmental factors, maladaptive behaviors often play an important role in the development of many of the circadian rhythm sleep disorders. This review will focus on the clinical approach to the diagnosis and management of the various circadian rhythm sleep disorders, including delayed sleep phase disorder, advanced sleep phase disorder, non-entrained type, irregular sleep-wake rhythm, shift work sleep disorder and jet lag disorder. Diagnostic tools such as sleep diaries and wrist activity monitoring are often useful in confirming the diagnosis. Because behavioral and environmental factors often are involved in the development of these conditions, a multimodal approach is usually necessary. Interventions include sleep hygiene education, timed exposure to bright light as well as avoidance of bright light at the wrong time of the day and pharmacologic approaches, such as melatonin. However, it should be noted that the use of melatonin is not an FDA-approved indication for the treatment of circadian rhythm sleep disorders.

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.

Circadian Rhythm Sleep Disorders

Individuals who have circadian rhythm sleep disorders present with symptoms of insomnia or excessive sleepiness and complain of an inability to sleep at their desired time. Although the primary etiology of these disorders is a misalignment between the endogenous circadian clock and the external environment, social and behavioral factors can also play important roles in perpetuating or exacerbating these disorders. Currently, the management of circadian rhythm disorders is limited to the use of bright light and melatonin to realign the circadian clock with the desired sleep time.However, as the understanding of the physiologic and genetic basis of sleep and circadian rhythm regulation advances, even more practical and effective treatments should become available.

Light treatment and circadian adaptation to shift work

Work at unconventional hours can have both long and short term consequences. Shift workers are often required to perform their duties at times that are not favoured by the body's endogenous clock, or circadian pacemaker. A typical night shift worker, for example, may report reductions in alertness and performance during shifts, or significant difficulty attaining sleep of recuperative value in the day, all the while being more likely to develop health complications. The study of circadian physiology has significantly contributed to our current ability to aid the shift worker deal with atypical schedules. We discuss the usefulness of light treatment as a countermeasure for maladaptation to atypical work schedules.

Circadian rhythm sleep disorders: lessons from the blind

As totally blind people cannot perceive the light-dark cycle (the major synchroniser of the circadian pacemaker) their circadian rhythms often "free run" on a cycle slightly longer than 24 h. When the free-running sleep propensity rhythm passes out of phase with the desired time for sleep, night-time insomnia and daytime sleepiness result. It has recently been shown that daily melatonin administration can entrain the circadian pacemaker, thereby correcting this burdensome circadian sleep disorder. The primary purpose of this review is to elevate awareness of circadian sleep disorders in totally blind people (especially free-running rhythms) and to provide some guidance for clinical management. An additional goal is to show how research on sleep and circadian rhythms in the totally blind can contribute insights into the scientific understanding of the human circadian system. 2001 Harcourt Publishers Ltd

Sleep loss and temporal memory

Historical evidence suggests that sleep deprivation affects temporal memory, but this has not been studied systematically. We explored the effects of 36 hr of sleep deprivation on a neuropsychological test of temporal memory. To promote optimal performance, the test was short, novel, and interesting, and caffeine was used to reduce "sleepiness". A total of 40 young adults were randomized into four groups: control + caffeine (Cc), control + placebo (Cp), sleep deprived + caffeine (SDc), and sleep deprived + placebo (SDp). Controls slept normally. Caffeine (350 mg) or placebo were given just prior to testing. The task comprised colour photographs of unknown faces and had two components: recognition memory (distinction between previously presented and novel faces), and recency discrimination (temporal memory), when a previously shown face was presented. An interpolated task, self-ordered pointing, acted as a distraction. Caffeine had no effects within control conditions, but significantly reduced subjective sleepiness in SDc. Recognition was unaffected by sleep deprivation, whereas for recency, sleep deprivation groups scored significantly lower than controls. There was no significant improvement of recency with caffeine in the SDc group. Both sleep deprivation groups had poorer insight into their performance with recency. Self-ordered pointing remained unchanged. In conclusion, sleep deprivation impairs temporal memory (i.e. recency) despite other conditions promoting optimal performance.

How to use light and dark to produce circadian adaptation to night shift work

The circadian rhythms of night shift workers do not usually adjust to their unusual work and sleep schedules, reducing their quality of life and producing potentially dangerous health and safety problems. This paper reviews field studies of simulated night work in which shifted light-dark cycles were constructed with artificial bright or medium-intensity light to produce circadian adaptation, ie the shifting of circadian rhythms to align with night work and day sleep schedules. By using these studies we describe fundamental principles of human circadian rhythms relevant to producing circadian adaptation to night shift work at a level designed for the reader with only a basic knowledge of circadian rhythms. These principles should enable the reader to start designing work/sleep-light/dark schedules for producing circadian adaptation in night shift workers. One specific schedule is presented as an example. Finally, we discuss phase-response curves to light and clarify common misconceptions about the production of circadian rhythm phase shifts.

Promoting sleep in shiftworkers and intercontinental travelers

A number of techniques and treatments can be used to alleviate the sleep disturbance associated with both shiftwork and transmeridian travel. Optimization of the sleeping environment and avoidance of substances such as caffeine and alcohol before sleep are the best initial approach. Timing sleep to coincide with some of the normal sleep period where possible will improve sleep quality in shiftworkers. Similarly, following transmeridian flight, restricting sleep to the nocturnal period in the new time zone will assist adaptation. Hypnotic drugs may be of benefit to alleviate sleep disturbance experienced by shiftworkers or transmeridian travelers. Selection of the most appropriate medication must take into account required duration of action and possible residual effects of the drug on alertness. Hypnotics may be useful, particularly in middle-aged individuals who already have disturbed sleep, on those occasions when poor sleep is anticipated, for example following an eastward flight or after the initial change to night duty. Over-the-counter preparations should be avoided whenever possible unless it is known that they are not associated with residual sequelae.

Alertness-enhancing drugs as a countermeasure to fatigue in irregular work hours

Irregular work/rest patterns frequently cause disturbed sleep and excessive sleepiness and accidents. This review is focused on four pharmacological countermeasures-the "new" drugs modafinil and pemoline, the traditional caffeine, and, as a reference, amphetamine. It is concluded that there is still too little data available to decide whether systematic use of alertness-enhancing drugs is feasible in occupational settings. D-Amphetamine is ruled out because of its abuse potential and mood effects. Modafinil and pemoline have not been tested in field situations, whereas caffeine certainly is used to improve alertness during work, but the use is spontaneous/ad hoc, and there is still a lack of data on its systematic application. Particularly, the optimal amount and pattern of administration need elucidation.