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Long-haul cabin crew regularly report misalignment between their circadian phase and the external world (i.e. jet lag). The extent to which changes in circadian phase relate to reported levels of jet lag remains unclear. The main aim of the present study was first to evaluate the relationship between objective (circadian phase) and subjective jet lag and second to explore the relative role of both subjective and objective psycho-behavioural factors in predicting the subjective experience of jet lag. Twenty-eight long-haul cabin crew completed questionnaires measuring diurnal preference, trip characteristics and subjective jet lag as a single and as a multidimensional measure. Sleep was monitored using actigraphy and urinary melatonin peak time was measured, at baseline (T1), e.g. before a long-haul trip and post-trip on the crew's first recovery day (T2). Subjective jet lag was also measured at both time points. At T1, later circadian phase related to increased unidimensional jet lag, however, a post-trip discrepancy was found between objective and subjective uni- and multidimensional jet lag measured at T2 and change from T1 to T2. After controlling for direction and size of circadian phase, increased uni- and multidimensional subjective jet lag was predicted by depressed mood states. The regression models including phase, diurnal preference, departure time on the outbound sector and arousal levels accounted for 28% of the variance in unidimensional jet lag and 53% of the variance in multidimensional jet lag. It was concluded that there is a discordance between objective and subjective jet lag post-trip. Further, subjective jet lag in long-haul cabin crew is better explained by mood impairment than circadian phase. The results are discussed with reference to the gap between subjective and objective jet lag and the role of psychology rather than just biology in the jet lag experience. The implications for improving health and safety in the workplace, through a better understanding of the role of human factors in the management of jet lag, are discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Sleep timing is controlled by the subtle interplay between circadian and homeostatic oscillators which, according to their endogenous properties, allow beings to feel spontaneously that it is time to go to bed or wake up in synchrony with the earth's light/dark cycle. In humans, however, social time and nocturnal artificial light modify sleep timing. Our modern lifestyle and artificial nocturnal light delay our bedtime, make us wake up, and lead to a greater intraindividual variability in sleep timing. Depending on the constraints that social time places on us, our sleep timing may be in or out of phase with the internal circadian timing determined by the circadian clock. When a person's social time is out of phase with their circadian time, they may be considered to suffer from circadian disruption or 'social jetlag'. There are interindividual differences in sleep timing that are known as morningness-eveningness preferences or chronotype, e.g. late chronotypes go to bed later. Chronotype may be assessed in terms of differences in kinetic homeostatic sleep pressure, intrinsic circadian period (ICP) and/or phase angle entrainment. In addition, chronotype depends on genetic and age-related factors, e.g. it gets earlier as people grow older. The social time of late chronotype individuals during week days is not adapted to their circadian time, unlike on free days. This results in social jetlag and circadian disruption, which in turn induces a chronic sleep debt due to a late bedtime and an early wake time, which is compensated on free days but only partially. Sleep and circadian clock disruption generally alter cognitive performance (alertness, attention, memory, higher-order executive functions such as response inhibition and decision-making) but their impact remains to be clarified. When subjects adopt their preferred sleep timing, a "synchrony effect" often appears with chronotypes performing better during daytime at optimal than at suboptimal timing (late chronotypes perform better in the evening, early chronotypes in the morning). Evening types appear to be cognitively more vulnerable to suboptimal times than morning types, probably because they have to deal with social jetlag and the "wake effort" period after awakening. Circadian disruption, but not chronotype, may impact attentional/inhibitory performance (more impulsivity and inattention). Strong associations have been found between mood disorders or attention deficit hyperactivity disorder (ADHD) and chronotype, with these psychiatric disorders typically being overrepresented in evening types. The association between social jetlag and these psychiatric disorders is less obvious. Social jetlag can be corrected by reducing exposure to evening light, although eveningness may be considered as a lifelong factor predisposing to depression or inattention., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Sleep and circadian clock disruption are associated with neuropsychiatric disorders, such as attention deficit hyperactivity disorder, but the impact on neurocognitive performance is unclear. We assessed whether chronotype and everyday circadian misalignment manifested as social jetlag were associated with inter-individual neurocognitive performance across domains of attention, inhibitory control and decision making. One hundred and eighty-eight healthy young adults were assessed for sleep and circadian properties and performed two neurocognitive tasks, the Continuous Performance Test and the Iowa Gambling Task. Social jetlag was associated with significantly faster and less variable reaction times and commission errors on the Continuous Performance Test. Poorer subjective sleep quality was associated with poorer decision making on the Iowa Gambling Task. No effects were present for polymorphisms in the circadian clock genes CLOCK and PER3. We conclude that circadian disruption shaped by everyday environmental factors may impact on attentional/inhibitory performance but not on a measure of risky decision making., (© 2020 European Sleep Research Society.)

Past studies examining the effect of chronotype and social jetlag on psychological well-being have been inconsistent so far. Here, we recruited participants from the general population and enquired about their natural sleeping behavior, sleep quality, depressive symptoms, and perceived stress. Partial correlations were computed between sleep variables and indicators of psychological well-being, controlling for age and sex. Less sleep during work days was found a good indicator for impairments in psychological well-being. In exploratory follow-up analyses, the same correlations were calculated within groups of early, intermediate, and late chronotype. We observed that the composition of the sample in terms of chronotype influenced whether associations between sleep variables and psychological well-being could be observed, a finding that is advised to be taken into account in future studies.

For elite athletes who exercise at a high level, sleep is critical to overall health. Many studies have documented the effects of sleep deprivation in the general population, but few studies exist regarding specific effects in the athlete. This review summarizes the effects of sleep deprivation and sleep extension on athletic performance, including reaction time, accuracy, strength and endurance, and cognitive function. There are clear negative effects of sleep deprivation on performance, including reaction time, accuracy, vigor, submaximal strength, and endurance. Cognitive functions such as judgment and decision-making also suffer. Sleep extension can positively affect reaction times, mood, sprint times, tennis serve accuracy, swim turns, kick stroke efficiency, and increased free throw and 3-point accuracy. Banking sleep (sleep extension prior to night of intentional sleep deprivation before sporting event) is a new concept that may also improve performance. For sports medicine providers, the negative effects of sleep deprivation cannot be overstated to athletes. To battle sleep deprivation, athletes may seek supplements with potentially serious side effects; improving sleep quality however is simple and effective, benefiting not only athlete health but also athletic performance., Competing Interests: Authors declare that they have no conflict of interest., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: Elite athletes have to travel long-haul distances and cross multiple meridians; thus, a unique syndrome named as jet-lag is induced. Furthermore, traveler athletes are submitted to several factors negatively affecting their well-being and athletic performance. This qualitative descriptive study aims to promote safely and future promising participations of elite athletes in great events, such as the next Olympic Games 2020 Tokyo, based on the chronobiology of jet-lag, factors affecting the traveler athlete and previous experiences from the 2014 FIFA World Cup Brazil, the 2018 FIFA World Cup Russia and the Olympic Games Rio 2016., Methods: A narrative review of the literature across a broad cross-section of the chronobiology of jet-lag and factors affecting the traveler athlete was undertaken. In addition, a general analysis based on the past sport events aforementioned is also included., Results: The jet-lag disorder may occur after transmeridian travel over more than three time-zones and the resynchronization is dependent on the direction and number of the time-zones crossed and the availability and the intensity of local circadian time cues. Also the athlete's ability to sleep, eat, get hydrated and train, are essential, as well as, others individual tolerance differences, such as age, gender, chronotype and ethnic differences. Athletes should arrive a number of days before the competition according to the number of time-zone transitions experienced., Conclusions: Jet-lag is usually benign and self-limited, but can occasionally have serious consequences for the athlete's mental and physical health and performance. A good plan concerning the athlete's traveling schedule, sleeping, eating and training before and after travelling is mandatory.

The aim of this study was to compare chronotype- and age-dependent sleep disturbances and social jetlag between rotating shift workers and non-shift workers, and between different types of shifts. In the Klokwerk+ cohort study, we included 120 rotating shift workers and 74 non-shift workers who were recruited from six Dutch hospitals. Participants wore Actigraph GT3X accelerometers for 24 hr for 7 days. From the Actigraph data, we predicted the sleep duration and social jetlag (measure of circadian misalignment). Mixed models and generalized estimation equations were used to compare the sleep parameters between shift and non-shift workers. Within shift workers, sleep on different shifts was compared with sleep on work-free days. Differences by chronotype and age were investigated using interaction terms. On workdays, shift workers had 3.5 times (95% confidence interval: 2.2-5.4) more often a short (< 7 hr per day) and 4.1 times (95% confidence interval: 2.5-6.8) more often a long (≥ 9 hr per day) sleep duration compared with non-shift workers. This increased odds ratio was present in morning chronotypes, but not in evening chronotypes (interaction p-value < .05). Older shift workers (≥ 50 years) had 7.3 times (95% confidence interval: 2.5-21.8) more often shorter sleep duration between night shifts compared with work-free days, while this was not the case in younger shift workers (< 50 years). Social jetlag due to night shifts increased with increasing age (interaction p-value < .05), but did not differ by chronotype (interaction p-value ≥ .05). In conclusion, shift workers, in particular older workers and morning chronotypes, experienced more sleep disturbances than non-shift workers. Future research should elucidate whether these sleep disturbances contribute to shift work-related health problems., (© 2018 European Sleep Research Society.)

Social jetlag is a term used to describe misalignment between biological and social time. Measured as the difference in sleep midpoints between work and free days, social jetlag has been associated with unhealthy lifestyle behaviours and adverse health outcomes. This study aimed to identify the prevalence of social jetlag, and its sociodemographic and behavioural correlates in 837 respondents who completed the Sleep Health Foundation Australia 2016 online survey. Binomial logistic regression models determined associations between social jetlag and self-reported lifestyle and work outcomes, excluding night, evening or rotating shift workers. One third (31.1%) of respondents experienced >1h of social jetlag. In analyses adjusted for sociodemographic variables associated with social jetlag (age, marital status, work status and metropolitan living plus the significant interaction term for age by metro living), social jetlag was associated with longer sleep duration on free days (OR = 2.8, CI = 1.9-4.1), evening preference (OR = 2.0, CI = 1.4-2.4), often staying up later than planned on work days (OR 1.9, CI = 1.3-2.9), and having a computer (OR = 1.7, CI = 1.2-2.4) or phone (OR = 1.6, CI = 1.1-2.4) in the bedroom and internet use in the hour before bed (OR = 1.7, CI 1.2-2.5). Almost twice as many working respondents with social jetlag reported going to work when they should have taken sick leave due to their state of health (OR = 1.9, CI = 1.3-3.0). In conclusion, social jetlag is prevalent in the Australian community and associated with bedtime technology use. Work attendance when in poor health is cause for concern in Australian day workers and requires further investigation., (Copyright © 2018 Elsevier B.V. All rights reserved.)

CME: Jet Lag Jetlag Abstract. Crossing several time zones by air travel leads to a temporary desynchronization of the internal clock with the external light/dark cycle. In the following jet lag occurs typically including difficulties falling asleep or waking up early as well as day-time sleepiness and significant reduction of wellbeing and fitness. To provide optimal medical advice, it is necessary to understand the human circadian rhythm and sleep-wake regulation. In consideration with additional information on travel plans, an approach to alleviate jet lag symptoms can be developed. This article addresses different supportive measures and advice on how to adjust to a new time zone and reduce jet lag symptoms.

Sleep deficiency is a major public health concern. Since epidemiological studies play an important role in public health evaluations, this theoretical paper pursues answers to the question: 'How can we compute sleep deficiency as informative measures of exposures or doses in observational research?' Starting from the social jetlag concept and based on the chronodisruption rationale, we illustrate and discuss five approaches (one established and four untested, each with unique strengths and limitations) to quantify sleep deficiency by focusing on the timing and duration of sleep. Hitherto, social jetlag and chronodisruption rationale were neither explicitly proposed nor developed as assessments of sleep deficiency but, as we suggest, could potentially be utilized to this end. This first foray into computing sleep deficiency in epidemiological studies makes clear that laboratory, field and epidemiological collaboration is pre-requisite to elucidating potential (co-)causal roles of sleep deficiency in disease endpoints., (© 2017 European Sleep Research Society.)

We investigated the effects of a circadian disadvantage (i.e. playing in a different time zone) on the winning percentages in three major sport leagues in North America: the National Basketball Association, the National Hockey League and the National Football League. We reviewed 5 years of regular season games in the National Basketball Association, National Hockey League and National Football League, and noted the winning percentage of the visiting team depending on the direction of travel (west, east, and same time zone) and game time (day and evening games). T-tests and analysis of variance were performed to evaluate the effects of the circadian disadvantage, its direction, the number of time zones travelled, and the game time on winning percentages in each major league. The results showed an association between the winning percentages and the number of time zones traveled for the away evening games, with a clear disadvantage for the teams travelling westward. There was a significant difference in the teams' winning percentages depending on the travelling direction in the National Basketball Association (F 2,5908  = 16.12, P < 0.0001) and the National Hockey League (F 2,5639  = 4.48, P = 0.011), and a trend was found in the National Football League (F 2,1279  = 2.86, P = 0.058). The effect of the circadian disadvantage transcends the type of sport and needs to be addressed for greater equity among the western and eastern teams in professional sports. These results also highlight the importance of circadian rhythms in sport performance and athletic competitions., (© 2017 European Sleep Research Society.)

Purpose: This study aimed to determine the recovery timeline of sleep, subjective jet lag and fatigue, and team sport physical performance after east and west long-haul travel., Methods: Ten physically trained men underwent testing at 0900 h and 1700 h local time on four consecutive days 2 wk before outbound travel (BASE), and the first 4 d after 21 h of outbound (WEST) and return (EAST) air travel across eight time zones between Australia and Qatar. Data collection included performance (countermovement jump, 20-m sprint, and Yo-Yo intermittent recovery level 1 [YYIR1] test) and perceptual (jet lag, motivation, perceived exertion, and physical feeling) measures. In addition, sleep was measured via wrist activity monitors and self-report diaries throughout the aforementioned data collection periods., Results: Compared with the corresponding day at BASE, the reduction in YYIR1 distance after EAST was significantly different from the increase in WEST on day 1 after travel (P < 0.001). On day 2, significantly slower 20-m sprint times were detected in EAST compared with WEST (P = 0.03), with large effect sizes (ES) also indicating a greater reduction in YYIR1 distance in EAST compared with WEST (d = 1.06). Mean sleep onset and offset were significantly later and mean time in bed and sleep duration were significantly reduced across the 4 d in EAST compared with BASE and WEST (P < 0.05). Lastly, mean jet lag, fatigue, and motivation ratings across the 4 d were significantly worse in EAST compared with BASE and WEST (P < 0.05) and WEST compared with BASE (P < 0.05)., Conclusions: Long-haul transmeridian travel can impede team sport physical performance. Specifically, east travel has a greater detrimental effect on sleep, subjective jet lag, fatigue, and motivation. Consequently, maximal and intermittent sprint performance is also reduced after east travel, particularly within 72 h after arrival.

Objective: Established risk factors for jet lag are mostly physiological including circadian preference, age, gender, the number of flight zones crossed and to some extent direction of travel. Some research has also highlighted a role for psychosocial factors including sleep, diet and 'circadian' health behaviours and illness cognitions although this remains relatively untested. The aim of this study was to evaluate the role of sleep, diet and illness cognitions in predicting perceived jet lag amongst long-haul crew., Design: Sixty long-haul crew took part in a longitudinal study. Profile characteristics (including chronotype), preparation strategies (sleep, eating and 'circadian' behaviours) and illness cognitions were measured at baseline (before a trip)., Main Outcome Measures: Subjective jet lag (unidimensional and multidimensional) was measured on the crews' second day off (post-trip)., Results: Hierarchical regression analyses showed that unidimensional jet lag was predicted by the belief in a cyclical timeline, whereas multidimensional jet lag was predicted by multidimensional jet lag at baseline and to a lesser extent by identity. No role was found for profile characteristics and preparation strategies., Conclusion: Illness cognitions partly explain the experience of perceived jet lag in long-haul cabin crew indicating that jet lag is in part a psycho-social construct, not just a biological one.

Objective: Jet lag is common place amongst long-haul cabin crew. Timed food has been shown to reset the circadian rhythm in rodents. Implementation intentions have been used to change eating behaviour. Mealtimes could therefore be used as a countermeasure to reduce jet lag and improve alertness in long-haul cabin crew through forming an implementation intention to improve the regularity of meals on days off., Design: Sixty long-haul crew took part in a randomised controlled trial, with two conditions: forming an implementation intention to eat regular meals on days off vs. no implementation intention. Pre-intervention measurements were taken at baseline (before a long-haul trip) and post-intervention measures were taken on the first and second days off post-trip., Main Outcome Measures: Subjective jet lag (unidimensional and multidimensional) and objective alertness (Psychomotor Vigilance Task (PVT))., Results: Mixed ANOVA showed a significant condition x time interaction for unidimensional jet lag but not for multidimensional jet lag and objective alertness. In particular, the formation of an implementation intention to alter mealtimes resulted in a reduction of unidimensional jet lag., Conclusion: Implementation intentions can be used to alleviate jet lag in long-haul crew through promoting a change in mealtimes.

Objectives: Given the sensitivity of individuals with mood disorders to circadian disruption, transmeridian travel would likely be a high-risk endeavour leading to onset or relapses in mood. A systematic review was undertaken to identify the evidence of the impact of transmeridian travel on people with mood disorders., Methods: Databases search included the following: CINAHL, MEDLINE, PsycINFO and manual searching using the keywords jetlag, transmeridian travel, circadian rhythm disruption, mood disorder, bipolar, major depression, seasonal affective disorder, depression, mania and hypomania., Results: Only three studies were identified that related to transmeridian travel and jetlag in people with mood disorders. There is some suggestion that transmeridian travel does appear to precipitate mood episodes with an increased rate of episodes of depression with westward compared with an increased rate of manic/hypomanic episodes with eastward travel. Individuals with a previous history of mood disorder appear to be more vulnerable if adherence to medication is compromised., Conclusion: Given the limited evidence that transmeridian travel precipitates mood episodes, this poses difficulties in identifying suitable ways to mitigate the effects of transmeridian travel in mood disorders. However, in the absence of mood-specific guidelines, some guidance can be given based on our current understanding of the relevance of circadian disruption to both jetlag and mood disorders. Further research is required to identify more focused strategies to mitigate the impact of transmeridian travel for individuals with mood disorders., (© The Royal Australian and New Zealand College of Psychiatrists 2015.)

Study Objectives: To group participants according to markers of risk for severe mental illness based on subsyndromal symptoms reported in early adulthood and evaluate attributes of sleep across these risk categories., Methods: An online survey of sleep and psychiatric symptomatology (The Oxford Sleep Survey) was administered to students at one United Kingdom university. 1403 students (undergraduate and postgraduate) completed the survey. The median age was 21 (interquartile range = 20-23) and 55.60% were female. The cross-sectional data were used to cluster participants based on dimensional measures of psychiatric symptoms (hallucinations, paranoia, depression, anxiety, and (hypo)mania). High, medium, and low symptom groups were compared across sleep parameters: insomnia symptoms, nightmares, chronotype, and social jet lag., Results: Insomnia symptoms, nightmares frequency, and nightmare-related distress increased in a dose-response manner with higher reported subsyndromal psychiatric symptoms (low, medium, and high). The high-risk group exhibited a later chronotype (mid sleep point for free days) than the medium- or low-risk group. The majority of participants (71.7%) in the high-risk group screened positive for insomnia and the median nightmare frequency was two per 14 days (moderately severe pathology)., Conclusions: Insomnia, nightmares, and circadian phase delay are associated with increased subsyndromal psychiatric symptoms in young people. Each is a treatable sleep disorder and might be a target for early intervention to modify the subsequent progression of psychiatric disorder., (© 2016 Associated Professional Sleep Societies, LLC.)

Context: Shift work, which imposes a habitual disruption in the circadian system, has been linked to increased incidence of cardiometabolic diseases, and acute circadian misalignment alters various metabolic processes. However, it remains unclear whether day-to-day circadian dysregulation contributes to these risks beyond poor sleep and other behavioral characteristics., Objective: Individuals differ in circadian phase preference, known as chronotype, but may be constrained by modern work obligations to specific sleep schedules. Individuals experience social jetlag (SJL) due to a habitual discrepancy between their endogenous circadian rhythm and actual sleep times imposed by social obligations. Here, we examined whether chronotype and/or SJL associate with components of cardiovascular disease risk beyond the known effects of sleep disturbances, poor health behaviors, and depressive symptomatology., Design: Participants were healthy, midlife adults who worked part- or full-time day shifts (n = 447; mean age, 42.7 [range, 30-54] y; 53% female; 83% white). Chronotype was assessed with the Composite Scale of Morningness. SJL was quantified as the difference (in minutes) between the midpoints of actigraphy-derived sleep intervals before work vs non-workdays., Results: Multiple regression analyses showed that SJL related to a lower high-density lipoprotein-cholesterol level, higher triglycerides, higher fasting plasma insulin, insulin resistance, and adiposity (P < .05), even after adjustment for subjective sleep quality, actigraphy-derived sleep characteristics, depressive symptomatology, and health behaviors. Evening chronotype associated with lower high-density lipoprotein-cholesterol after adjustment for covariates., Conclusion: Our findings suggest that a misalignment of sleep timing is associated with metabolic risk factors that predispose to diabetes and atherosclerotic cardiovascular disease.

Rationale: A substantial number of clinical studies indicate associations between sleep abnormalities and drug abuse; however, the role played by the circadian system in the development of addiction is largely unknown., Objective: The aim of this study was to examine the effects of experimentally induced chronic jet lag on methamphetamine consumption in a rat model of methamphetamine drinking., Methods: Male Sprague-Dawley rats (n = 32) were housed in running wheel cages in a 12:12 h light:dark cycle. One group of rats (n = 16) was given 2 weeks of forced methamphetamine consumption (0.01 % in drinking water; meth pre-exposed) while a second group (n = 16, not pre-exposed) received water only. This was followed by a 2-week abstinence period during which half of the animals from each group were exposed to four consecutive 6-h advancing phase shifts of the light:dark cycle, while the other half remained on the original light:dark cycle. Methamphetamine consumption was assessed in all rats following the deprivation period using a two-bottle choice paradigm., Results: Methamphetamine consumption was initially lower in methamphetamine pre-exposed versus not pre-exposed rats. However, during the second week following abstinence, consumption was significantly higher in phase-shifted rats of the methamphetamine pre-exposed group compared to all other groups., Conclusions: These data reveal an effect of circadian rhythm disturbance on methamphetamine consumption and suggest that dysregulation of the circadian system be considered in the etiology of relapse and addiction.

In the general consideration of travel-related illnesses, not much attention is given to mental health, while a significant proportion is due to psychiatric problems. Any trip is a source of stress that may trigger or worsen mental disorders ranging from culture shock to a pathogenic trip via the classic pathological trip: for a tourist seeking exotic adventure, young people in initiatory journey, an expatriate, a political refugee or an immigrant in search of better economic conditions, any traveler may stumble upon the traces of his own family history or of his home culture fantasy, and show symptoms at some stage along his path of psychological disorders. Indeed every culture identify appointed destinations where its members are seemingly more likely to falter: the roads to the east or the search for paradise lost for westerners (the Florence syndrome, the India syndrome or the island syndrome), those of the West (the Japanese in Paris syndrome), or places rich with mystical associations: Mecca for Muslims, Benares for Hindis, Jerusalem for the monotheistic religions. A return to the home country is mostly a necessary requirement for the subject to regain a footing in his culture.

Sleep loss and circadian disruption-a state of misalignment between physiological functions and imposed sleep/wake behavior-supposedly play central roles in the etiology of shift work-related pathologies [1-4]. Circadian entrainment is, however, highly individual [5], resulting in different chronotypes [6, 7]. Chronotype in turn modulates the effects of working times: compared to late chronotypes, earlier ones sleep worse and shorter and show higher levels of circadian misalignment during night shifts, while late types experience more sleep and circadian disruption than early types when working morning shifts [8]. To promote sleep and reduce the mismatch between circadian and working time, we implemented a chronotype-adjusted (CTA) shift schedule in a factory. We abolished the most strenuous shifts for extreme chronotypes (i.e., mornings for late chronotypes, nights for early ones) and examined whether sleep duration and quality, social jetlag [9, 10], wellbeing, subjective stress perception, and satisfaction with leisure time improved in this schedule. Intermediate chronotypes (quartiles 2 and 3) served as a control group, still working morning (6:00-14:00), evening (14:00-22:00), and night (22:00-6:00) shifts, with two strenuous shifts (out of twelve per month) replaced by evening ones. We observed a significant increase of self-reported sleep duration and quality, along with increased wellbeing ratings on workdays among extreme chronotypes. The CTA schedule reduced overall social jetlag by 1 hr, did not alter stress levels, and increased satisfaction with leisure time (early types only). Chronotype-based schedules thus can reduce circadian disruption and improve sleep; potential long-term effects on health and economic indicators need to be elucidated in future studies., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Behavior, physiological functions and cognitive performance change over the time of the day. These daily rhythms are either externally driven by rhythmic environmental cues such as the light/dark cycle (masking) or controlled by an internal circadian clock, the suprachiasmatic nucleus (SCN), which can be entrained to the light/dark cycle. Within a given species, there is genetically determined variability in the temporal preference for the onset of the active phase, the chronotype. The chronotype is the phase of entrainment between external and internal time and is largely regulated by the circadian clock. Genetic variations in clock genes and environmental influences contribute to the distribution of chronotypes in a given population. However, little is known about the determination of the chronotype, the stability of the locomotor rhythm and the re-synchronization capacity to jet lag in an animal without a functional endogenous clock. Therefore, we analyzed the chronotype of BMAL1-deficient mice (BMAL1-/-) as well as the effects of repeated experimental jet lag on locomotor activity rhythms. Moreover, light-induced period expression in the retina was analyzed to assess the responsiveness of the circadian light input system. In contrast to wild-type mice, BMAL1-/- showed a significantly later chronotype, adapted more rapidly to both phase advance and delay but showed reduced robustness of rhythmic locomotor activity after repeated phase shifts. However, photic induction of Period in the retina was not different between the two genotypes. Our findings suggest that a disturbed clockwork is associated with a late chronotype, reduced rhythm stability and higher vulnerability to repeated external desynchronization.

Long-term exposure to transmeridian flights has been shown to impact cognitive functioning. Nevertheless, the immediate effects of jet lag in the activation of specific brain networks have not been investigated. We analyzed the impact of short-term jet lag on the activation of the default mode network (DMN). A group of individuals who were on a transmeridian flight and a control group went through a functional magnetic resonance imaging acquisition. Statistical analysis was performed to test for differences in the DMN activation between groups. Participants from the jet lag group presented decreased activation in the anterior nodes of the DMN, specifically in bilateral medial prefrontal and anterior cingulate cortex. No areas of increased activation were observed for the jet lag group. These results may be suggestive of a negative impact of jet lag on important cognitive functions such as introspection, emotional regulation and decision making in a few days after individuals arrive at their destination.

Air travel is a common mode of transportation in today's society, particularly for individuals traveling long distances. Sleep disturbances associated with air travel frequently result in cognitive and physiologic impairments that may be detrimental to the traveler's experience and intent. A primary consequence of air travel is the development of acute sleep deprivation, which may result in reduced attention/vigilance, alteration in mood states, diminished memory processing, and alteration in executive function. Along with and contributing to acute sleep deprivation, circadian rhythm misalignment resulting in jet lag disorder (JLD) is frequently encountered by air travelers traversing multiple time zones. JLD is characterized by insomnia or excessive daytime sleepiness associated with physical or mental impairment associated with travel. This review focuses on the neurocognitive manifestations of acute sleep deprivation and the pathophysiology and treatment of JLD to provide the practicing clinician a greater understanding of the sleep abnormalities manifest in air travelers. Treatment recommendations for the traveler, including the use of light/melatonin therapy, sleep scheduling, and pharmacologic aids for both sleep and alertness, are provided.

Circadian rhythms are endogenous and need to be continuously entrained (synchronized) with the environment. Entrainment includes both coupling internal oscillators to external periodic changes as well as synchrony between the central clock and peripheral oscillators, which have been shown to exhibit different phases and resynchronization speed. Temporal desynchronization induces diverse physiological alterations that ultimately decrease quality of life and induces pathological situations. Indeed, there is a considerable amount of evidence regarding the deleterious effect of circadian dysfunction on overall health or on disease onset and progression, both in human studies and in animal models. In this review we discuss the general features of circadian entrainment and introduce diverse experimental models of desynchronization. In addition, we focus on metabolic, immune and cognitive alterations under situations of acute or chronic circadian desynchronization, as exemplified by jet-lag and shiftwork schedules. Moreover, such situations might lead to an enhanced susceptibility to diverse cancer types. Possible interventions (including light exposure, scheduled timing for meals and use of chronobiotics) are also discussed., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Sleep is a key element, both physiologically and psychologically, in adolescent development. The prevalence of sleep disorders in western countries is important, as with age the sleep-wake cycle of adolescents becomes irregular and delayed in relation with later sleep onset and waking time resulting in rhythm desynchronization. A large number of adolescents sleep for 7-8h instead of 9-10h per night, which can lead to a cumulative sleep debt with fatigue, behavioral problems and poor academic achievement. The effect of electronic media use (such as television, mobile phone, computer, and electronic gaming) on sleep has been the object of several international studies, though pubertal changes may also impact adolescent sleep. Adolescents and their parents should be educated by professionals, including physicians and nurses, on the key role of sleep in adolescent well being and quality of life. A number of basic rules are proposed to improve sleep in adolescents. The permanent social jet lag experienced by a number of adolescents should be considered as a matter of public health., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Jet lag syndrome appears after multiple time zone transitions as bodily rhythms shift out of phase with the local environment. The possible psychiatric complications of jet lag have been underinvestigated. In the present review, the symptoms of jet lag in the general population, the chronobiological aspects of psychosis, as well as a possible correlation between jet lag and psychosis are discussed. The conclusions are that jet lag, through disruption of biological rhythm and probably sleep deprivation, may yield an exacerbation of existing psychotic conditions. The evidence concerning the appearance of de novo psychosis triggered by jet lag is inconsistent and far from convincing.

Objective: To assess the effect of armodafinil, the longer-lasting isomer of modafinil, on jet lag disorder., Participants and Methods: This double-blind, randomized, parallel-group, multicenter study was conducted between September 18, 2008, and February 9, 2009. Adults with a history of jet lag symptoms on previous flights through multiple time zones flew from the United States to France (a 6-hour time zone change) for a 3-day laboratory-based study period. Participants received armodafinil (50 or 150 mg/d) or placebo each morning. Wakefulness was assessed by the coprimary outcomes, mean sleep latency on the Multiple Sleep Latency Test (MSLT) (average of all MSLT sessions across days 1 and 2) and Patient Global Impression of Severity in relation to jet lag symptoms (averaged across days 1 and 2)., Results: A total of 427 participants received armodafinil at 50 mg/d (n=142), armodafinil at 150 mg/d (n=143), or placebo (n=142). Armodafinil at 150 mg/d provided a significant benefit in sleep latency on the MSLT (days 1-2: mean, 11.7 minutes vs 4.8 minutes for placebo; P<.001) and participants' perception of their overall condition in relation to jet lag symptoms (Patient Global Impression of Severity, days 1-2: mean, 1.6 vs 1.9 for placebo; P<.05). The most frequently reported adverse events for armodafinil at 150 mg/d were headache (27%), nausea (13%), diarrhea (5%), circadian rhythm sleep disorder (5%), and palpitations (5%)., Conclusion: Armodafinil increased wakefulness after eastward travel through 6 time zones., Trial Registration: clinicaltrials.gov identifier: NCT00758498.

Objective: Millions of adults in the United States travel abruptly across time zones each year. Nevertheless, the impact of traveling over relatively short distances (across 3 or fewer time zones) on diurnal patterning of typical physiological response patterns has yet to be studied in a large, epidemiological sample., Design: The current research focuses on 764 middle-aged men comparing variations in diurnal cortisol regulation based on number of time zones traveled eastward or westward the day before., Main Outcome Measure: Participants provided samples of salivary cortisol at waking, 30-min postwaking, 10 a.m., 3 p.m., and bedtime., Results: Eastward travel was associated with a steeper salivary cortisol awakening response (p < .01) and lower peak (PEAK) levels of salivary cortisol the next morning (p < .05). Westward travel was associated with lower peak levels of cortisol the next morning (p < .05). Effect sizes for these differences ranged from Cohen's d = .29 to .47. Differences were not present for 2 days in their home environment., Conclusions: The results provide evidence that traveling across time zones is associated with diurnal cortisol regulation and should be studied further to understand the subsequent impacts on health and well-being in large national samples., (Copyright 2010 APA, all rights reserved.)

It is often stated that light is the primary environmental cue (zeitgeber) for entrainment of circadian clocks. Here, we use a new conflict test design in Syrian hamsters comparing the strength of a photic zeitgeber to that of a non-photic cue, i.e. wheel availability. Re-entrainment to an inverted LD cycle was significantly slowed down in the nocturnal hamster by restricting wheel access to the light phase of the inverted LD cycle. This effect is more pronounced if the illuminance level of the entraining lights is 0.1 lx compared to 6 lx. In this conflict design, the hamsters did not re-entrain to an inverted LD cycle for up to four weeks (when the experiment ended), but voluntarily ran during the light phase. This approximates the situation in people subjected to shift work or jet lag.

Many aspects of life in plants, animals and humans are controlled by light. Endogenous, so-called circadian rhythms in the body deviate from the exact 24-hour day and have typically a period of around 25.5 hours in man. Normally these rhythms adapt to the external 24-hour day-and night changes but under constant conditions the rhythms can free run. Many studies show how important the interplay between light and the circadian rhythms are for man as well as for other organisms. The control of these rhythms by light is mediated via the retina and the melatonin system in man. The adaptation of the rhythms is very important in shift work, in rapid jet lag travels over time zones, etc. Organisms often use the circadian rhythm to determine the length of day and of night, a feature that has given rise to the term biological clocks. A biological clock provides possibilities to determine the proper time for physiological processes to start in plants and animals (flowering, hibernation etc). The importance of light and circadian rhythms for seasonal affective disorders and manic-depressive disorders is also discussed. For several organisms one has now been able to specify genes that determine the period of the clocks. The rhythmic physiologic processes, the light reactions and the general importance of light for rhythms and for man are now studied at the molecular level.

Context: Both light and melatonin can be used to phase shift the human circadian clock, but the phase-advancing effect of the combination has not been extensively investigated., Objective: The objective of the study was to determine whether phase advances induced by morning intermittent bright light and a gradually advancing sleep schedule could be increased with afternoon melatonin., Participants: Healthy adults (25 males, 19 females, between the ages of 19 and 45 yr) participated in the study., Design: There were 3 d of a gradually advancing sleep/dark period (wake time 1 h earlier each morning), bright light on awakening [four 30-min bright-light pulses (approximately 5000 lux) alternating with 30 min room light < 60 lux] and afternoon melatonin, either 0.5 or 3.0 mg melatonin timed to induce maximal phase advances, or matching placebo. The dim light melatonin onset was measured before and after the treatment to determine the phase advance., Results: There were significantly larger phase advances with 0.5 mg (2.5 h, n = 16) and 3.0 mg melatonin (2.6 h, n = 13), compared with placebo (1.7 h, n = 15), but there was no difference between the two melatonin doses. Subjects did not experience jet lag-type symptoms during the 3-d treatment, Conclusions: Afternoon melatonin, morning intermittent bright light, and a gradually advancing sleep schedule advanced circadian rhythms almost 1 h/d and thus produced very little circadian misalignment. This treatment could be used in any situation in which people need to phase advance their circadian clock, such as before eastward jet travel or for delayed sleep phase syndrome.

Entrainment of the circadian rhythm has 2 aspects, period and phase adjustments, which are established simultaneously in most nonhuman circadian systems. The human circadian system is unique in its functional structure in which 2 different subsystems are involved; one is the circadian pacemaker analogous to that located in the suprachiasmatic nucleus, and the other is the oscillatory system of unknown nature that drives the rest-activity cycle. The human circadian system shows the endogenous period very close to 24 h under entrainment and less sensitive to photic stimuli than under free running, which may explain stable entrainment in the real word where natural sun lights are unpredictable in terms of the intensity and time of appearance. On the other hand, nonphotic entrainment seems to play a significant role in phase adjustment of the human circadian system. Nonphotic zeitgebers initially directed to the rest-activity cycle may affect the circadian pacemaker through feedback and/or associated LD cycles.

Introduction: The melatonin agonist LY 156735 (LY) is a new investigational drug under development to treat circadian rhythm disorders. The present study assessed the efficacy of LY to alleviate the symptoms of shift lag and to enhance readaptation of desynchronized circadian rhythms to a new time zone., Subjects and Methods: Eight healthy male volunteers of age 25-35 yr participated in three identical trials of 13d duration in a temporal isolation unit separated by washout intervals. A high dose (HD) of 5 mg and a low dose (LD) of 0.5 mg of LY and placebo (PL) were administered double-blinded in a three-period cross-over design. Each trial consisted of an adaptation period, a pre-shift period for baseline measurements, a simulated 9h phase-advance shift, and a post-shift period for follow-up. The time shift was performed at 23:00h of day 6 by advancing the laboratory time to 08:00h of day 7. Double-blind study medication was administered at 14:30h on day 6, and at 22:30h on days 7-10. Subjective ratings of jet lag, alertness, tenseness, and daytime fatigue were assessed using visual analog scales (VAS) and standardized questionnaires. The objective markers of readaptation included core body temperature, wrist actigraphy, cortisol and electrolyte excretion, and a battery of computerized performance tests., Results: HD but not LD enhanced the readaptation speed of all physiological rhythms investigated, as demonstrated by a significantly faster movement of acrophases towards the post-shift target time. HD (p = 0.05) significantly blunted the post-shift deterioration of performance in those tests that were sensitive to shift lag. Parameters of subjective well-being were not significantly affected by either dose., Conclusion: This pilot study demonstrates the chronobiotic efficacy of LY when taken at a dose of 5 mg/d.

Background: Circadian rhythms shift out of phase after transmeridian flights. Desynchronization between body rhythms and the environment is linked to jet lag, which depends on age, flight direction, and number of time zones crossed., Methods: To investigate this problem in airline pilots, we performed a multivariate analysis of their circadian systems during Madrid-Mexico-Madrid flights (-7 time zones, n = 12) and Madrid-Tokyo-Madrid flights (+8 time zones, n = 21). Telemetry was used to record pilots' activity, skin temperature, and heart rate, obtaining 6 d of continuous data, including 2 d before the flight, the flights themselves, 2 d at the stopover, and 1 d after the return flight. Time series were analyzed by cosinor, and the resulting parameters of the rhythms were compared by ANOVA and Tukey contrasts in every category formed by the age groups (under and over 50 yr old) and flight direction groups. Subjective time estimation of short, intermediate, and long intervals was recorded. Other psychological variables were measured, including anxiety, tiredness, and performance., Results and Conclusions: Activity/rest and heart rate rhythms appeared to be linked to a "weak oscillator." Temperature rhythms manifested a rigid response after the phase shifts of the light/dark cycle, closely related to the biological clock. Subjective time appreciation tended to be overestimated without exhibiting a clear circadian component, but attributable to fatigue and stress. Psychometric evaluation showed that desynchronization affected all the pilots. Some results showed an age-related variability with a more marked influence in younger pilots. No consistent effects regarding flight direction were found.

Jet lag is a travel-induced circadian rhythm phenomenon that afflicts healthy individuals following long- distance flights through several time zones. The typical jet-lag manifestations - insomnia during local sleep time, day fatigue, reduced concentration, irritability, and exhaustion with mild depression - are attributed to transient desynchronization in the circadian rhythm until the internal biological clock is rephased to the new environmental conditions. There is strong evidence relating affective disorders with circadian rhythm abnormalities. Less convincing suggestions relate jet lag to psychosis. It can be hypothesized that in predisposed individuals jet lag may play a role in triggering exacerbation or even de novo affective disorders. Furthermore, we propose the possibility that psychosis and even schizophrenia can be elicited by jet lag. This outlook gains its support from case studies and some common underlying phase-advanced biological denominators involved in both jet lag sufferers and psychotic patients.

Twenty healthy elderly subjects (12 female, 8 male; mean age 81 years, range 67-87 years) each experienced a 15-day time isolation protocol in which they lived individually in a special laboratory apartment in which sleep and circadian rhythm measures could be taken. There were two experiments: one (6 females, 4 males) involved a 6-h phase advance of the sleep/wake cycle, and the other (6 females, 4 males) a 6-h phase delay. Each started with 5 baseline days, immediately followed by the phase shift. The subject was then held to the phase shifted routine for the remainder of the study. Rectal temperatures were recorded minute-by-minute throughout the entire experiment and each night of sleep was recorded using polysomnography. A directional asymmetry in phase-shift effects was apparent, with significantly more sleep disruption and circadian rhythm amplitude disruption after the phase advance than after the phase delay. Sleep disruption was reflected in reduced time spent asleep, and in changed REM latency, which increased in the phase advance direction but decreased in the phase delay direction. Although the phase advance led to a significant increase in wakefulness in the first half of the night, the phase delay did not lead to an equivalent increase in wakefulness during the second half of the night. Examination of both raw and 'demasked' circadian rectal temperature rhythms confirmed that phase adjustment was slow in both directions, but was less slow (and more monotonic) after the phase delay than after the phase advance. Subjective alertness suffered more disruption after the phase advance than after the phase delay.

Desynchronization of circadian rhythmicity resulting from rapid travel through at least 4 time zones leads to symptoms of jet lag syndrome. The most commonly experienced symptoms in normal individuals are sleep disorders, difficulties with concentrating, irritability, mild depression, fatigue, and gastrointestinal disturbances. There is strong evidence relating affective disorders to circadian rhythm abnormalities, such as occur in jet lag. Less convincing suggestions relate jet lag to psychosis. We presume, relying on the literature and our accumulated experience, that in predisposed individuals jet lag may play a role in triggering exacerbation of, or de novo affective disorders, as well as, though less convincing, schizophreniform psychosis or even schizophrenia. An illustrative case vignette exemplifies the possible relationship between jet lag following eastbound flight and psychotic manifestations.

The effects of zopiclone on the rest/activity rhythm were investigated after a westward flight with a 5-h phase delay (Grenoble-Martinique). The rest/activity rhythm was recorded continuously with an actigraph monitor during a 6-day baseline episode in Grenoble and a 6-day sojourn in Martinique. Rectal temperature was recorded before the flight on day 2 and after the flight on days 2 and 5. Subjective jet-lag score was assessed before the flight on days 1 and 2 and in Martinique on days 1, 2, 5 and 6. Zopiclone (7.5 mg) or placebo were administered double blind 30 min prior to bedtime during the first 4 post-flight days (D1-D4). Under zopiclone treatment, sleep was less fragmented on the first post-flight night and the curtailment of sleep duration observed on D2 and D3 under placebo was prevented. During day-time, subjects tended to be more active than with placebo. By contrast, subjective jet-lag scores did not differ between both groups. Zopiclone seemed to accelerate the readjustment of the rest/activity rhythm and the normalisation of the phase relationship between sleep and the temperature rhythm. Zopiclone probably exerts its "resetting" effects on jet-lag desynchronosis by facilitating sleep induction rather than via a chronobiotic action.

Traveling across time zones causes disruption to the normal circadian rhythms and social schedules because of travelers' shift in time. As the endogenous circadian timing system adapts slowly to new time cues, the phase relationship between biological rhythms and external time cues are out of synchronization for a period of time. This disturbance of circadian rhythms has been shown to impair physical and psychological health (Winget et al., 1984). To test the effects of repeated jet lag on mental abilities, airline cabin crew were compared with ground crew. Salivary cortisol was used as a physiological marker for circadian disruption. The cabin crew group, who had a history of repeated jet lag, had significantly higher salivary cortisol levels in an average working day. In addition, this elevated level of cortisol was only seen in the same subjects when the cabin crew were on transmeridian flights but not domestic flights. Cabin crew also exhibited cognitive deficits, possibly in working memory, that became apparent after several years of chronic disruption of circadian rhythms.

At periodic intervals throughout the biological day, assessments were made for a week prior to intercontinental flight yielding a reference of biological time set to the environment of origin, for two weeks at the temporally displaced environment of destination, and for a week following return to the environment of origin. Assessments made included rectal temperature, heart rate, respiratory rate, palmar evaporative water loss, urinalysis, reaction time, decision time, critical flicker fusion, subjective fatigue and well-being, and intellectual facility. The intercontinental flights consisted of east-west and west-east flights which permitted a comparative analysis of bidirectional effects of time zone displacements and a north-south flight which provided an appraisal of effects solely attributable to prolonged flight. Shifts of the phase of circadian periodicity manifested by the physiological functions were effected by the east-west and west-east flights but not by the north-south flight. Bidirectional differences in lag time and extent of dissociation were revealed, but these may be due to individual variability. All flights engendered significant increment in subjective fatigue. Only one flight, the east-west, produced significant performance deficit indicating that while rapid translocation through many time zones does effect physiological phase shifts requiring 4-6 days for completion and impairment of well-being, these phenomena are not accompanied by a commensurate change in the efficiency of basic psychological functions.