Assessment and management of sleep disorders in shift workers: Challenges and considerations for general practice

BACKGROUND

Shift work is characterised by displaced sleep opportunities and associated sleep disturbance. Shift workers often report sleepiness and other wake time symptoms associated with poor sleep. However, clinical sleep disorders are also prevalent in shift workers. Although prevalence rates are similar or higher in shift workers compared with the general population, help seeking in shift workers with sleep disorders is low.

OBJECTIVE

This article aims to provide general practitioners with a contemporary overview of the prevalence rates for sleep disorders in shift workers, to clarify the existing evidence relating to mental and physical health consequences of sleep disorders in shift workers and to highlight the need to consider undiagnosed sleep disorders before attributing sleep-related symptoms solely to work schedules.

DISCUSSION

Symptoms of sleep loss associated with shift work overlap with symptoms experienced by individuals living with sleep disorders. Although >40% of middle-aged Australians live with a sleep disorder that requires investigation and management, symptoms in shift workers are often attributed to the work schedule and, as a result, might not be investigated for appropriate diagnosis and treatment. We argue that screening for sleep disorders in shift workers with sleep complaints should be a priority.

Heart failure causes sleepless nights

Cardiac dysfunction triggers immune-mediated loss of pineal gland melatonin release.

Immune-mediated denervation of the pineal gland underlies sleep disturbance in cardiac disease

Disruption of the physiologic sleep-wake cycle and low melatonin levels frequently accompany cardiac disease, yet the underlying mechanism has remained enigmatic. Immunostaining of sympathetic axons in optically cleared pineal glands from humans and mice with cardiac disease revealed their substantial denervation compared with controls. Spatial, single-cell, nuclear, and bulk RNA sequencing traced this defect back to the superior cervical ganglia (SCG), which responded to cardiac disease with accumulation of inflammatory macrophages, fibrosis, and the selective loss of pineal gland-innervating neurons. Depletion of macrophages in the SCG prevented disease-associated denervation of the pineal gland and restored physiological melatonin secretion. Our data identify the mechanism by which diurnal rhythmicity in cardiac disease is disturbed and suggest a target for therapeutic intervention.

Human circadian variations

Circadian rhythms, present in most phyla across life, are biological oscillations occurring on a daily cycle. Since the discovery of their molecular foundations in model organisms, many inputs that modify this tightly controlled system in humans have been identified. Polygenic variations and environmental factors influence each person's circadian rhythm, contributing to the trait known as chronotype, which manifests as the degree of morning or evening preference in an individual. Despite normal variation in chronotype, much of society operates on a "one size fits all" schedule that can be difficult to adjust to, especially for certain individuals whose endogenous circadian phase is extremely advanced or delayed. This is a public health concern, as phase misalignment in humans is associated with a number of adverse health outcomes. Additionally, modern technology (such as electric lights and computer, tablet, and phone screens that emit blue light) and lifestyles (such as shift or irregular work schedules) are disrupting circadian consistency in an increasing number of people. Though medical and lifestyle interventions can alleviate some of these issues, growing research on endogenous circadian variability and sensitivity suggests that broader social changes may be necessary to minimize the impact of circadian misalignment on health.

Demographic, psychological, chronobiological, and work-related predictors of sleep disturbances during the COVID-19 lockdown in Italy

The first COVID-19 contagion wave caused unprecedented restraining measures worldwide. In Italy, a period of generalized lockdown involving home confinement of the entire population was imposed for almost two months (9 March-3 May 2020). The present is the most extensive investigation aimed to unravel the demographic, psychological, chronobiological, and work-related predictors of sleep disturbances throughout the pandemic emergency. A total of 13,989 Italians completed a web-based survey during the confinement period (25 March-3 May). We collected demographic and lockdown-related work changes information, and we evaluated sleep quality, insomnia and depression symptoms, chronotype, perceived stress, and anxiety using validated questionnaires. The majority of the respondents reported a negative impact of confinement on their sleep and a delayed sleep phase. We highlighted an alarming prevalence of sleep disturbances during the lockdown. Main predictors of sleep disturbances identified by regression models were: female gender, advanced age, being a healthcare worker, living in southern Italy, confinement duration, and a higher level of depression, stress, and anxiety. The evening chronotype emerged as a vulnerability factor, while morning-type individuals showed a lower predisposition to sleep and psychological problems. Finally, working from home was associated with less severe sleep disturbances. Besides confirming the role of specific demographic and psychological factors in developing sleep disorders during the COVID-19 pandemic, we propose that circadian typologies could react differently to a particular period of reduced social jetlag. Moreover, our results suggest that working from home could play a protective role against the development of sleep disturbances during the current pandemic emergency.

Circadian Rhythm Sleep-Wake Disorders

PURPOSE OF REVIEW

This article provides an overview of circadian physiology and discusses common presentations and treatment strategies for the circadian rhythm sleep-wake disorders.

RECENT FINDINGS

Circadian rhythms are present throughout the body, and appreciation for the role that circadian dysregulation plays in overall health is increasing, with mounting associations between circadian disruption and cardiometabolic disease risk.

SUMMARY

It is important to recognize the ubiquitous role that circadian rhythms play throughout the brain and body. An understanding of circadian neurophysiology will provide insight into the means by which patients with a variety of neuropathologies at the level of the retina, optic nerve, or hypothalamus may also be at risk for circadian dysfunction.

Disrupted nocturnal melatonin in autism: Association with tumor necrosis factor and sleep disturbances

Sleep disturbances, abnormal melatonin secretion, and increased inflammation are aspects of autism spectrum disorder (ASD) pathophysiology. The present study evaluated the daily urinary 6-sulfatoxymelatonin (aMT6s) excretion profile and the salivary levels of tumor necrosis factor (TNF) and interleukin-6 (IL-6) in 20 controls and 20 ASD participants, as well as correlating these measures with sleep disturbances. Although 60% of ASD participants showed a significant night-time rise in aMT6s excretion, this rise was significantly attenuated, compared to controls (P < .05). The remaining 40% of ASD individuals showed no significant increase in nocturnal aMT6s. ASD individuals showed higher nocturnal levels of saliva TNF, but not IL-6. Dysfunction in the initiation and maintenance of sleep, as indicated by the Sleep Disturbance Scale for Children, correlated with night-time aMT6s excretion (r = -.28, P < .05). Dysfunction in sleep breathing was inversely correlated with aMT6s (r = -.31, P < .05) and positively associated with TNF level (r = .42, P < .01). Overall such data indicate immune-pineal axis activation, with elevated TNF but not IL-6 levels associated with disrupted pineal melatonin release and sleep dysfunction in ASD. It is proposed that circadian dysregulation in ASD is intimately linked to heightened immune-inflammatory activity. Such two-way interactions of the immune-pineal axis may underpin many aspects of ASD pathophysiology, including sleep disturbances, as well as cognitive and behavioral alterations.

Home-EEG assessment of possible compensatory mechanisms for sleep disruption in highly irregular shift workers - The ANCHOR study

Study objectives

While poor sleep quality has been related to increased risk of Alzheimer’s disease, long-time shift workers (maritime pilots) did not manifest evidence of early Alzheimer’s disease in a recent study. We explored two hypotheses of possible compensatory mechanisms for sleep disruption: Increased efficiency in generating deep sleep during workweeks (model 1) and rebound sleep during rest weeks (model 2).

Methods

We used data from ten male maritime pilots (mean age: 51.6±2.4 years) with a history of approximately 18 years of irregular shift work. Subjective sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI). A single lead EEG-device was used to investigate sleep in the home/work environment, quantifying total sleep time (TST), deep sleep time (DST), and deep sleep time percentage (DST%). Using multilevel models, we studied the sleep architecture of maritime pilots over time, at the transition of a workweek to a rest week.

Results

Maritime pilots reported worse sleep quality in workweeks compared to rest weeks (PSQI = 8.2±2.2 vs. 3.9±2.0; p<0.001). Model 1 showed a trend towards an increase in DST% of 0.6% per day during the workweek (p = 0.08). Model 2 did not display an increase in DST% in the rest week (p = 0.87).

Conclusions

Our findings indicated that increased efficiency in generating deep sleep during workweeks is a more likely compensatory mechanism for sleep disruption in the maritime pilot cohort than rebound sleep during rest weeks. Compensatory mechanisms for poor sleep quality might mitigate sleep disruption-related risk of developing Alzheimer’s disease. These results should be used as a starting point for future studies including larger, more diverse populations of shift workers.

Sleep and sleepiness in shift-working tram drivers

Driver sleepiness contributes to traffic accidents. However, sleepiness in urban public transport remains an understudied subject. To fill this gap, we examined the sleepiness, sleep, and on-duty sleepiness countermeasures (SCMs) in 23 tram drivers working morning, day, and evening shifts for three weeks. Sleepiness was measured using Karolinska Sleepiness Scale (KSS). Nocturnal total sleep time (TST) was measured with wrist actigraphy. SCMs and naps were self-reported with a smartphone application. Caffeine and napping were considered effective SCMs. Severe sleepiness (KSS ≥ 7) was observed in 22% of shifts with no differences between shift types. Rest breaks were associated with slight reductions in sleepiness. TST between days off averaged 7 h but was 1 h 33 min and 38 min shorter prior to morning and day shifts, respectively. The use of effective SCMs showed little variance between shift types. These results highlight the need for fatigue management in non-night-working tram drivers.

Carotid intimal medial thickness in rotating night shift is related to IL1β/IL6 axis

BACKGROUND AND AIMS

Sleep disturbances may promote glucose abnormalities and inflammatory burden among shift workers. Therefore, precocious subclinical atherosclerotic process might develop in healthy shift workers even without known metabolic and cardiovascular risk factors.

METHODS AND RESULTS

We measured anthropometric parameters, glucose, lipids, inflammation and common carotid Intimal Medial Thickness (cIMT) in rotating-night shift workers (r-NSW, n = 88, age = 40.3 ± 7.8 y) in comparison with former-night shift workers (f-NSW, n = 35, age = 44.2 ± 6.4 y) and with day-only workers (DW, n = 64, age = 44.1 ± 8.9 y). R-NSW and f-NSW showed significantly higher cIMT and high sensitivity C-Reactive Protein (hs-CRP) respect to DW (p = 0.043 and p = 0.025, respectively). IL-1β levels were higher in r-NSW than in DW and f-NSW (p = 0.043) and significantly correlated with IL6 (r = 0.365, p < 0.001). In addition, r-NSW and f-NSW had higher HbA1c levels in comparison with DW (p = 0.047). Carotid-IMT was significantly related to night shift work (p = 0.023), with age (p < 0.001), with HOMA IR (p = 0.009), with insulin (p = 0.006) with HbA1c (p = 0.002), with LDL cholesterol (p < 0.001), with diastolic BP (p < 0.001), with WBC (p = 0.002) and with IL6 (p = 0.004). After performing a multivariate analysis night shift work remained statistically related to cIMT (B = 2.633, 95%CI = 0.489-4.776, p = 0.016).

CONCLUSIONS

Our result described a possible link bridging night shift work, inflammation and carotid Intimal Medial Thickness. Future studies are warranted to understand if carotid atherosclerosis process should be mainly driven by the IL1β/IL6 citokine axis connected to sleep disturbances.

[Circadian rhythm sleep disorders: clinical picture, diagnosis and treatment]

Circadian rhythm sleep disorders (CRSD) represent sleep-wake disturbances due to a disruption of endogenous circadian system or to a desynchronization between internal sleep-wake rhythms and the external environment. They comprise seven diagnostic entities grouped in two main categories: endogenous and exogenous. The patients typically describe chronic excessive daytime sleepiness and/or insomnia symptoms, impacting their daytime functioning. The exact prevalence of CRSD is probably underestimated. The diagnosis is based on sleep diary coupled with actigraphy. Several therapeutic options are validated to allow the realignment between endogenous circadian rhythm and the external environment. The correct diagnostic of CRSD is important to improve the patient's quality of life and to propose them appropriate treatment.

Effect of Suvorexant vs Placebo on Total Daytime Sleep Hours in Shift Workers: A Randomized Clinical Trial

IMPORTANCE

Many shift workers have difficulty sleeping during the daytime owing to an inappropriately timed circadian drive for wakefulness.

OBJECTIVE

To determine whether a dual hypocretin receptor antagonist would enable shift workers to have more daytime sleep.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind, placebo-controlled randomized clinical trial included 2 weeks of baseline data and 3 weeks of intervention data, from March 2016 to December 2018. Individuals were recruited through poster advertisements in the broader San Francisco Bay area in California. From an initial voluntary recruitment cohort of 38 shift workers, 19 individuals with self-reported difficulty sleeping during the daytime following night work shift were included. Data were analyzed from Janaury to March 2019.

INTERVENTIONS

1 week of 10 mg suvorexant or placebo, titrated upward to 20 mg suvorexant or placebo for 2 additional weeks.

MAIN OUTCOMES AND MEASURES

Objective (ie, actigraphy) and subjective (ie, sleep logs) measures of sleep.

RESULTS

Among 19 participants who completed the study (mean [SD] age, 37.7 [11.1] years; 13 [68%] men), 8 participants (42%) were assigned to the suvorexant group and 11 participants (58%) were assigned to the placebo group. Compared with individuals in the placebo group, individuals in the suvorexant group increased their objective total sleep time by a mean (SE) of 1.04 (0.53) hours (P = .05) at the end of 1 week of 10-mg doses and by 2.16 (0.75) hours (P = .004) by the end of the 2 weeks of 20-mg doses. Subjective sleep was similarly improved as, compared with the placebo group, individuals in the suvorexant group increased their subjective total sleep time by a mean (SE) of 2.08 (0.47) hours (P < .001) at the end of 1 week of 10-mg doses and by 2.97 (0.56) hours (P < .001) by the end of the 2 weeks of 20-mg doses. Physician ratings of daytime sleep aligned with these measures, as there was no change in the placebo group and a much improved change in the suvorexant group. No adverse events were reported in the suvorexant group.

CONCLUSIONS AND RELEVANCE

This pilot study found that the use of a dual hypocretin receptor antagonist in shift workers under real-world conditions resulted in more than 2 extra hours of daytime sleep per episode. Future research should confirm this pilot finding in a larger sample size and examine whether, over the long term, use of this medication has a concomitant improvement in medical and psychiatric health as well as workplace performance and safety.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02491788.

Rapid suppression of bone formation marker in response to sleep restriction and circadian disruption in men

We describe the time course of bone formation marker (P1NP) decline in men exposed to ~ 3 weeks of sleep restriction with concurrent circadian disruption. P1NP declined within 10 days and remained lower with ongoing exposure. These data suggest even brief exposure to sleep and circadian disruptions may disrupt bone metabolism.

INTRODUCTION

A serum bone formation marker (procollagen type 1 N-terminal, P1NP) was lower after ~ 3 weeks of sleep restriction combined with circadian disruption. We now describe the time course of decline.

METHODS

The ~ 3-week protocol included two segments: "baseline," ≥ 10-h sleep opportunity/day × 5 days; "forced desynchrony" (FD), recurring 28 h day (circadian disruption) with sleep restriction (~ 5.6-h sleep per 24 h). Fasted plasma P1NP was measured throughout the protocol in nine men (20-59 years old). We tested the hypothesis that PINP would steadily decline across the FD intervention because the magnitude of sleep loss and circadian misalignment accrued as the protocol progressed. A piecewise linear regression model was used to estimate the slope (β) as ΔP1NP per 24 h with a change point mid-protocol to estimate the initial vs. prolonged effects of FD exposure.

RESULTS

Plasma P1NP levels declined significantly within the first 10 days of FD ([Formula: see text] = - 1.33 μg/L per 24 h, p < 0.0001) and remained lower than baseline with prolonged exposure out to 3 weeks ([Formula: see text] = - 0.18 μg/L per 24 h, p = 0.67). As previously reported, levels of a bone resorption marker (C-telopeptide (CTX)) were unchanged.

CONCLUSION

Sleep restriction with concurrent circadian disruption induced a relatively rapid decline in P1NP (despite no change in CTX) and levels remained lower with ongoing exposure. These data suggest (1) even brief sleep restriction and circadian disruption can adversely affect bone metabolism, and (2) there is no P1NP recovery with ongoing exposure that, taken together, could lead to lower bone density over time.

Effect of Light Flashes vs Sham Therapy During Sleep With Adjunct Cognitive Behavioral Therapy on Sleep Quality Among Adolescents: A Randomized Clinical Trial

IMPORTANCE

Owing to biological, behavioral, and societal factors, sleep duration in teenagers is often severely truncated, leading to pervasive sleep deprivation.

OBJECTIVE

To determine whether a novel intervention, using both light exposure during sleep and cognitive behavioral therapy (CBT), would increase total sleep time in teenagers by enabling them to go to sleep earlier than usual.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind, placebo-controlled, randomized clinical trial, conducted between November 1, 2013, and May 31, 2016, among 102 adolescents enrolled full-time in grades 9 to 12, who expressed difficulty going to bed earlier and waking up early enough, was composed of 2 phases. In phase 1, participants were assigned to receive either 3 weeks of light or sham therapy and were asked to try to go to sleep earlier. In phase 2, participants received 4 brief CBT sessions in addition to a modified light or sham therapy. All analyses were performed on an intent-to-treat basis.

INTERVENTIONS

Light therapy consisted of receiving a 3-millisecond light flash every 20 seconds during the final 3 hours of sleep (phase 1) or final 2 hours of sleep (phase 2). Sham therapy used an identical device, but delivered 1 minute of light pulses (appearing in 20-second intervals, for a total of 3 pulses) per hour during the final 3 hours of sleep (phase 1) or 2 hours of sleep (phase 2). Light therapy occurred every night during the 4-week intervention. Cognitive behavioral therapy consisted of four 50-minute in-person sessions once per week.

MAIN OUTCOMES AND MEASURES

Primary outcome measures included diary-based sleep times, momentary ratings of evening sleepiness, and subjective measures of sleepiness and sleep quality.

RESULTS

Among the 102 participants (54 female [52.9%]; mean [SD] age, 15.6 [1.1] years), 72 were enrolled in phase 1 and 30 were enrolled in phase 2. Mixed-effects models revealed that light therapy alone was inadequate in changing the timing of sleep. However, compared with sham therapy plus CBT alone, light therapy plus CBT significantly moved sleep onset a mean (SD) of 50.1 (27.5) minutes earlier and increased nightly total sleep time by a mean (SD) of 43.3 (35.0) minutes. Light therapy plus CBT also resulted in a 7-fold greater increase in bedtime compliance than that observed among participants receiving sham plus CBT (mean [SD], 2.21 [3.91] vs 0.29 [0.76]), as well as a mean 0.55-point increase in subjective evening sleepiness as compared with a mean 0.48-point decrease in participants receiving sham plus CBT as measured on a 7-point sleepiness scale.

CONCLUSIONS AND RELEVANCE

This study found that light exposure during sleep, in combination with a brief, motivation-focused CBT intervention, was able to consistently move bedtimes earlier and increase total sleep time in teenagers. This type of passive light intervention in teenagers may lead to novel therapeutic applications.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01406691.

Effectiveness of an Online CBT-I Intervention and a Face-to-Face Treatment for Shift Work Sleep Disorder: A Comparison of Sleep Diary Data

In western societies, about one in six employees works in shifts. Shiftwork is associated with a number of poor somatic and psychological health outcomes, especially sleep issues. Higher rates of absenteeism and accidents in the workplace are possible consequences. Still, prevention programs and treatment options that are specifically tailored to shift-workers’ needs are rare. We devised a 4-week online cognitive behavioral therapy for insomnia (CBT-I) intervention (n = 21) and compared sleep outcomes to a face-to-face outpatient treatment for shift-workers (n = 12) using a sleep diary and the Epworth Sleepiness Scale (ESS). In the online sample, measures also included the World Health Organization wellbeing questionnaire (WHO-5) and the Insomnia Severity Index (ISI). In the outpatient sample, the Beck Depression Inventory (BDI-II), the Montgomery–Åsberg Depression Rating Scale (MADRS), and the Pittsburgh Sleep Quality Index (PSQI) were administered. Results showed significant improvements in sleep efficiency by 7.2% in the online sample and 7.7% in the outpatient sample. However, no significant difference was found in the rate of improvement in sleep efficiency across four weeks of treatment between the samples. In the online sample, the wellbeing (WHO-5) and insomnia symptoms (ISI) scores were significantly improved following the CBT-I intervention (p < 0.004 and p < 0.002 respectively). In the outpatient sample, symptoms of depression (BDI-II and MADRS scores) and insomnia symptoms (PSQI scores) improved significantly following the CBT-I intervention. In summary, CBT-I significantly improved sleep efficiency in both the online and outpatient samples, in addition to wellbeing, symptoms of insomnia, and depression. The findings of this study demonstrate online CBT-I as a feasible approach for treating insomnia in shift-workers. Future randomized controlled trials are needed.

Morning Circadian Misalignment Is Associated With Insulin Resistance in Girls With Obesity and Polycystic Ovarian Syndrome

CONTEXT

To our knowledge, circadian rhythms have not been examined in girls with polycystic ovarian syndrome (PCOS), despite the typical delayed circadian timing of adolescence, which is an emerging link between circadian health and insulin sensitivity (SI), and decreased SI in PCOS.

OBJECTIVE

To examine differences in the circadian melatonin rhythm between obese adolescent girls with PCOS and control subjects, and evaluate relationships between circadian variables and SI.

DESIGN

Cross-sectional study.

PARTICIPANTS

Obese adolescent girls with PCOS (n = 59) or without PCOS (n = 33).

OUTCOME MEASURES

Estimated sleep duration and timing from home actigraphy monitoring, in-laboratory hourly sampled dim-light, salivary-melatonin and fasting hormone analysis.

RESULTS

All participants obtained insufficient sleep. Girls with PCOS had later clock-hour of melatonin offset, later melatonin offset relative to sleep timing, and longer duration of melatonin secretion than control subjects. A later melatonin offset after wake time (i.e., morning wakefulness occurring during the biological night) was associated with higher serum free testosterone levels and worse SI regardless of group. Analyses remained significant after controlling for daytime sleepiness and sleep-disordered breathing.

CONCLUSION

Circadian misalignment in girls with PCOS is characterized by later melatonin offset relative to clock time and sleep timing. Morning circadian misalignment was associated with metabolic dysregulation in girls with PCOS and obesity. Clinical care of girls with PCOS and obesity would benefit from assessment of sleep and circadian health. Additional research is needed to understand mechanisms underlying the relationship between morning circadian misalignment and SI in this population.

The Circadian Syndrome: is the Metabolic Syndrome and much more!

The Metabolic Syndrome is a cluster of cardio-metabolic risk factors and comorbidities conveying high risk of both cardiovascular disease and type 2 diabetes. It is responsible for huge socio-economic costs with its resulting morbidity and mortality in most countries. The underlying aetiology of this clustering has been the subject of much debate. More recently, significant interest has focussed on the involvement of the circadian system, a major regulator of almost every aspect of human health and metabolism. The Circadian Syndrome has now been implicated in several chronic diseases including type 2 diabetes and cardiovascular disease. There is now increasing evidence connecting disturbances in circadian rhythm with not only the key components of the Metabolic Syndrome but also its main comorbidities including sleep disturbances, depression, steatohepatitis and cognitive dysfunction. Based on this, we now propose that circadian disruption may be an important underlying aetiological factor for the Metabolic Syndrome and we suggest that it be renamed the 'Circadian Syndrome'. With the increased recognition of the 'Circadian Syndrome', circadian medicine, through the timing of exercise, light exposure, food consumption, dispensing of medications and sleep, is likely to play a much greater role in the maintenance of both individual and population health in the future.

Subjective Hunger, Gastric Upset, and Sleepiness in Response to Altered Meal Timing during Simulated Shiftwork

Shiftworkers report eating during the night when the body is primed to sleep. This study investigated the impact of altering food timing on subjective responses. Healthy participants (n = 44, 26 male, age Mean ± SD = 25.0 ± 2.9 years, BMI = 23.82 ± 2.59kg/m²) participated in a 7-day simulated shiftwork protocol. Participants were randomly allocated to one of three eating conditions. At 00:30, participants consumed a meal comprising 30% of 24 h energy intake (Meal condition; n = 14, 8 males), a snack comprising 10% of 24 h energy intake (Snack condition; n = 14; 8 males) or did not eat during the night (No Eating condition; n = 16, 10 males). Total 24 h individual energy intake and macronutrient content was constant across conditions. During the night, participants reported hunger, gut reaction, and sleepiness levels at 21:00, 23:30, 2:30, and 5:00. Mixed model analyses revealed that the snack condition reported significantly more hunger than the meal group (p < 0.001) with the no eating at night group reporting the greatest hunger (p < 0.001). There was no difference in desire to eat between meal and snack groups. Participants reported less sleepiness after the snack compared to after the meal (p < 0.001) or when not eating during the night (p< 0.001). Gastric upset did not differ between conditions. A snack during the nightshift could alleviate hunger during the nightshift without causing fullness or increased sleepiness.

The multiple sleep latency test

The measurement of daytime sleepiness is important in the evaluation of patients with excessive sleepiness. The multiple sleep latency test (MSLT) is an objective test that measures the tendency to fall asleep under controlled conditions. It is based on the notion that sleep latency reflects underlying physiological sleepiness. The MSLT consists of four to five naps given 2h apart during the day, following a standardized procedure. The mean sleep latency from all naps is used as the measure of sleepiness. The test has been shown to be valid and reliable and is part of the diagnostic criteria for narcolepsy and idiopathic hypersomnia. However, the MSLT is affected by numerous variables including insufficient sleep, drugs, activity, and arousal level. Adherence to the established protocol is necessary to limit the effect of these extraneous factors on the MSLT. While the test is a valuable and widely used diagnostic tool for narcolepsy and idiopathic hypersomnia, the use of MSLT in other sleep disorders is not well established.

Rhythms of life: circadian disruption and brain disorders across the lifespan

Many processes in the human body - including brain function - are regulated over the 24-hour cycle, and there are strong associations between disrupted circadian rhythms (for example, sleep-wake cycles) and disorders of the CNS. Brain disorders such as autism, depression and Parkinson disease typically develop at certain stages of life, and circadian rhythms are important during each stage of life for the regulation of processes that may influence the development of these disorders. Here, we describe circadian disruptions observed in various brain disorders throughout the human lifespan and highlight emerging evidence suggesting these disruptions affect the brain. Currently, much of the evidence linking brain disorders and circadian dysfunction is correlational, and so whether and what kind of causal relationships might exist are unclear. We therefore identify remaining questions that may direct future research towards a better understanding of the links between circadian disruption and CNS disorders.

Impact of Shift Work on the Circadian Timing System and Health in Women

Women who do shift work are a sizable part of the workforce. Shift workers experience circadian misalignment due to shifted sleep periods, with potentially far-reaching health consequences, including elevated risk of sleep disturbances, metabolic disorders, and cancer. This review provides an overview of the circadian timing system and presents the sex differences that can be observed in the functioning of this system, which may account for the lower tolerance to shift work for women compared with men. Recent epidemiologic findings on female-specific health consequences of shift work are discussed.

The pupillary light reflex distinguishes between circadian and non-circadian delayed sleep phase disorder (DSPD) phenotypes in young adults

This study investigated the utility of the pupillary light reflex as a method of differentiating DSPD patients with delayed melatonin timing relative to desired/required sleep time (circadian type) and those with non-delayed melatonin timing (non-circadian type). All participants were young adults, with a total of 14 circadian DSPD patients (M = 28.14, SD = 5.26), 12 non-circadian DSPD patients (M = 29.42, SD = 11.51) and 51 healthy controls (M = 21.47 SD = 3.16) completing the protocol. All participants were free of central nervous system acting medications and abstained from caffeine and alcohol on the day of the assessment. Two pupillary light reflex measurements were completed by each participant, one with a 1s dim (~10 lux) light exposure, and one with a 1s bright (~1500 lux) light exposure. Circadian DSPD patients showed a significantly faster pupillary light reflex than both non-circadian DSPD patients and healthy controls. Non-circadian patients and healthy controls did not differ significantly. Receiver operating characteristic curves were generated to determine the utility of mean and maximum constriction velocity in differentiating the two DSPD phenotypes, and these demonstrated high levels of sensitivity (69.23–-100%) and specificity (66.67–91.67%) at their optimal cut offs. The strongest predictor of DSPD phenotype was the mean constriction velocity to bright light (AUC = 0.87). These results support the potential for the pupillary light reflex to clinically differentiate between DSPD patients with normal vs. delayed circadian timing relative to desired bedtime, without the need for costly and time-consuming circadian assessments.

[Sleep and circadian rhythms]

The sleep-wake regulatory system and the circadian rhythm generating system are two brain networks integrated in the classical two-process model. These processes interact continuously, and to obtain an optimal sleep they must be correctly aligned. The suprachiasmatic nucleus located in the hypothalamus is crucial in the regulation of circadian rhythms, and the hypothalamus is a key component of the sleep-wake regulatory system in association with the thalamus, basal forebrain and brainstem. Alterations of these processes can result in a variety of sleep disturbances or sleep disorders.

Circadian Rhythm Sleep-Wake Disorders

PURPOSE OF REVIEW

The endogenous circadian rhythms are one of the cardinal processes that control sleep. They are self-sustaining biological rhythms with a periodicity of approximately 24 hours that may be entrained by external zeitgebers (German for time givers), such as light, exercise, and meal times. This article discusses the physiology of the circadian rhythms, their relationship to neurologic disease, and the presentation and treatment of circadian rhythm sleep-wake disorders.

RECENT FINDINGS

Classic examples of circadian rhythms include cortisol and melatonin secretion, body temperature, and urine volume. More recently, the impact of circadian rhythm on several neurologic disorders has been investigated, such as the timing of occurrence of epileptic seizures as well as neurobehavioral functioning in dementia. Further updates include a more in-depth understanding of the symptoms, consequences, and treatment of circadian sleep-wake disorders, which may occur because of extrinsic misalignment with clock time or because of intrinsic dysfunction of the brain. An example of extrinsic misalignment occurs with jet lag during transmeridian travel or with intrinsic circadian rhythm sleep-wake disorders such as advanced or delayed sleep-wake phase disorders. In advanced sleep-wake phase disorder, which is most common in elderly individuals, sleep onset and morning arousal are undesirably early, leading to impaired evening function with excessive sleepiness and sleep-maintenance insomnia with early morning awakening. By contrast, delayed sleep-wake phase disorder is characterized by an inability to initiate sleep before the early morning hours, with subsequent delayed rise time, leading to clinical symptoms of severe sleep-onset insomnia coupled with excessive daytime sleepiness in the morning hours, as patients are unable to "sleep in" to attain sufficient sleep quantity. Irregular sleep-wake rhythm disorder is misentrainment with patches of brief sleep and wakefulness spread throughout the day, leading to unstable sleep and waking behavioral patterns and an entirely idiosyncratic sleep-wake schedule.

SUMMARY

Familiarity with these major circadian rhythm sleep-wake disorder phenotypes and their overlap with other neurologic disorders is essential for the neurologist so that clinicians may intervene and improve patient functioning and quality of life.

Effects of sleep and fatigue on teams in a submarine environment

Successful submarine operations rely on the performance of tactical teams who must work under conditions of physiological and cognitive fatigue. Sleep loss and circadian disruption contribute to fatigue in this setting and, although the effects of this fatigue have been studied extensively in individuals, little is understood about how fatigue impacts team performance Рespecially in a submarine environment. The present review provides an overview of the fatigue on submarine teams and is divided into four main sections: 1) A discussion of factors that should be considered in team fatigue research. 2) An outline of how sleep and circadian rhythms of submariners are impacted by submarine-specific factors. 3) A discussion of the known effects of fatigue from sleep loss and circadian disruption on individual performance. 4) A consideration of how this fatigue impacts team performance. As the submarine force has recognized the need to protect submariner sleep and improve team dynamics, it is vital that future research accounts for the interplay between these two factors.