Influence of circadian phase and extended wakefulness on glucose levels during forced desynchrony.

Objectives: Circadian misalignment and sleep deprivation often occur in tandem, and both negatively impact glucose homeostasis and metabolic health. The present study employed a forced desynchrony protocol to examine the influence of extended wakefulness and circadian misalignment on hourly glucose levels.

Methods: Nine healthy adults (4F/5M; 26 ± 4years) completed a 31-day in-laboratory protocol.

Evaluation of sleep strategies between night shifts in actual shift workers.

Objectives: The aim of this observational study was to examine sleep obtained between consecutive night shifts from shift workers in their natural environment. The goal was to identify the various sleep strategies and the timing, duration, regularity, and quality of sleep associated with the strategies.

Methods: Participants (N = 33, 23 women, aged 40 ± 15years) reported their sleep information in daily diaries over 2weeks while working at least one series of consecutive night shifts.

Circadian- and wake-dependent influences on face-name memory in healthy men and women over 3weeks of chronic sleep restriction.

Objectives: Facial recognition is one of the key functions of the human brain, and linking a face to a name is critical in many social and occupational settings. This study assessed circadian- and wake-dependent effects on face-name recognition in healthy adults.

Methods: Thirteen healthy adults (20-70years; 7 F) were studied in a 39-day inpatient protocol that included 3weeks of 28 hours forced desynchrony with sleep restriction (6.

Desynchronizing the sleep---wake cycle from circadian timing to assess their separate contributions to physiology and behaviour and to estimate intrinsic circadian period.

Circadian clocks drive cyclic variations in many aspects of physiology, but some daily variations are evoked by periodic changes in the environment or sleep-wake state and associated behaviors, such as changes in posture, light levels, fasting or eating, rest or activity and social interactions; thus, it is often important to quantify the relative contributions of these factors. Yet, circadian rhythms and these evoked effects cannot be separated under typical 24-h day conditions, because circadian phase and the length of time awake or asleep co-vary. Nathaniel Kleitman's forced desynchrony (FD) protocol was designed to assess endogenous circadian rhythmicity and to separate circadian from evoked components of daily rhythms in multiple parameters.

High dose melatonin increases sleep duration during nighttime and daytime sleep episodes in older adults.

Aging is associated with changes in sleep, and improving sleep may have important consequences for the health, cognition, and quality of life of older adults. Many prescription sleep aids increase the risk of nighttime falls, have adverse effects on next-day cognition, and are associated with increased mortality. Melatonin, a hormone secreted at night, increases sleep duration in young adults but only when administered during the day when endogenous levels are low.

Impact of chronic sleep restriction on sleep continuity, sleep structure, and neurobehavioral performance.

Chronic sleep restriction (CSR) has been associated with adverse effects including cognitive impairment and increased risk of diabetes and cardiovascular disease. Yet, sleep restriction therapy is an essential component of most behavioral treatments for insomnia. Moreover, little is known about the impact of CSR on sleep continuity and structure in healthy people whose need for sleep is satiated.

Efficacy of intermittent exposure to bright light for treating maladaptation to night work on a counterclockwise shift work rotation.

Objectives: Rotating shift work is associated with adverse outcomes due to circadian misalignment, sleep curtailment, work-family conflicts, and other factors. We tested a bright light countermeasure to enhance circadian adaptation on a counterclockwise rotation schedule.

Methods: Twenty-nine adults (aged 20-40 years; 15 women) participated in a 4-week laboratory simulation with weekly counterclockwise transitions from day, to night, to evening, to day shifts.

Self-reported Drowsiness and Safety Outcomes While Driving After an Extended Duration Work Shift in Trainee Physicians.

Study Objectives: Extended duration (≥24 hours) work shifts (EDWSs) are associated with increased risk of motor vehicle crashes, and awareness of any impairment has important implications on legal accountability for any adverse driving outcome. The extent to which adverse driving events were preceded by predrive self-reported sleepiness was evaluated in medical residents after an EDWS.

Methods: Sixteen resident physicians (10 females; 29.

Sleep inertia, sleep homeostatic and circadian influences on higher-order cognitive functions.

Sleep inertia, sleep homeostatic and circadian processes modulate cognition, including reaction time, memory, mood and alertness. How these processes influence higher-order cognitive functions is not well known. Six participants completed a 73-day-long study that included two 14-day-long 28-h forced desynchrony protocols to examine separate and interacting influences of sleep inertia, sleep homeostasis and circadian phase on higher-order cognitive functions of inhibitory control and selective visual attention.

Prevalence of sleep deficiency and use of hypnotic drugs in astronauts before, during, and after spaceflight: an observational study.

Background: Sleep deprivation and fatigue are common subjective complaints among astronauts. Previous studies of sleep and hypnotic drug use in space have been limited to post-flight subjective survey data or in-flight objective data collection from a small number of crew members. We aimed to characterise representative sleep patterns of astronauts on both short-duration and long-duration spaceflight missions.

Assessment of drowsiness based on ocular parameters detected by infrared reflectance oculography.

Study Objectives: Numerous ocular parameters have been proposed as reliable physiological markers of drowsiness. A device that measures many of these parameters and then combines them into a single metric (the Johns Drowsiness Scale [JDS]) is being used commercially to assess drowsiness in professional drivers. Here, we examine how these parameters reflect changes in drowsiness, and how they relate to objective and subjective indices of the drowsy state in a controlled laboratory setting.

The effects of circadian phase, time awake, and imposed sleep restriction on performing complex visual tasks: evidence from comparative visual search.

Cognitive performance not only differs between individuals, but also varies within them, influenced by factors that include sleep-wakefulness and biological time of day (circadian phase). Previous studies have shown that both factors influence accuracy rather than the speed of performing a visual search task, which can be hazardous in safety-critical tasks such as air-traffic control or baggage screening. However, prior investigations used simple, brief search tasks requiring little use of working memory.

One night of sleep deprivation affects reaction time, but not interference or facilitation in a Stroop task.

The Stroop color-naming task is one of the most widely studied tasks involving the inhibition of a prepotent response, regarded as an executive function. Several studies have examined performance on versions of the Stroop task under conditions of acute sleep deprivation. Though these studies revealed effects on Stroop performance, the results often do not differentiate between general effects of sleep deprivation on performance and effects specifically on interference in the Stroop task.

Comparison of sustained attention assessed by auditory and visual psychomotor vigilance tasks prior to and during sleep deprivation.

To date, no detailed examination of the pattern of change in reaction time performance for different sensory modalities has been conducted across the circadian cycle during sleep deprivation. Therefore, we compared sustained auditory and visual attention performance during 40h of sleep deprivation assessing multiple metrics of auditory and visual psychomotor vigilance tasks (PVT). Forty healthy participants (14 women) aged 30.

Circadian and wake-dependent influences on subjective sleepiness, cognitive throughput, and reaction time performance in older and young adults.

Study Objectives: To assess circadian and homeostatic influences on subjective sleepiness and cognitive performance in older adults when sleep and waking are scheduled at different times of day; to assess changes in subjective sleepiness and cognitive performance across several weeks of an inpatient study; and to compare these findings with results from younger adults.

Design: Three 24-h baseline days consisting of 16 h of wakefulness and an 8-h sleep opportunity followed by 3-beat cycles of a 20-h forced desynchrony (FD) condition; 18 20-h "days," each consisting of 13.33 h of scheduled wakefulness and 6.

EEG sleep spectra in older adults across all circadian phases during NREM sleep.

Study Objectives: Healthy aging is associated with changes in sleep-wake regulation, and those changes often lead to problems sleeping, both during the night and during daytime. We aimed to examine the electroencephalographic (EEG) sleep spectra during non-rapid eye movement (NREM) sleep when sleep was scheduled at all times of day.

Design/interventions: After three 24-h baseline (BL) days, participants were scheduled to live on 20-hour "days" consisting of 6.

Comparison of subjective and objective assessments of sleep in healthy older subjects without sleep complaints.

Older adults have reduced sleep quality compared with younger adults when sleeping at habitual times and greater sleep disruption when their sleep is at adverse times. The purpose of this analysis was to investigate how subjective measures of sleep relate to objectively recorded sleep in older subjects scheduled to sleep at all times of day. We analyzed data from 24 healthy older (55-74 years) subjects who took part in a 32-day inpatient study where polysomnography was recorded each night and subjective sleep was assessed after each scheduled wake time.

A role for non-rapid-eye-movement sleep homeostasis in perceptual learning.

Slow-wave activity (SWA; EEG power density in the 0.75-4.5 Hz range) in non-rapid-eye-movement (NREM) sleep is the primary marker of sleep homeostasis and thought to reflect sleep need.

Sleep-facilitating effect of exogenous melatonin in healthy young men and women is circadian-phase dependent.

Study Objectives: To investigate the effects of a physiologic and a pharmacologic dose of exogenous melatonin on sleep latency and sleep efficiency in sleep episodes initiated across a full range of circadian phases.

Design: Double-blind placebo-controlled parallel-group design in a 27-day forced desynchrony paradigm with a 20-hour scheduled sleep-wake cycle.

Setting: Private suite of a general clinical research center, in the absence of time-of-day information.

Sleep and wakefulness out of phase with internal biological time impairs learning in humans.

Sleep-wake homeostatic and internal circadian timedependent brain processes interact to regulate human brain function so that alert wakefulness is promoted during the daytime and consolidated sleep is promoted at nighttime. The consequence of chronically altering the normal relationship between these processes for human brain function is largely unknown. We tested cognitive and vigilance performance while subjects lived in the laboratory for over a month.