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NASA NTRS2020

Introduction to Sleep and Circadian Physiology

The purpose of this talk is to provide an undergraduate student audience with basic information about the sleep and circadian challenges that astronauts and pilots face. Dr. Flynn-Evans will begin by highlighting how NASA works. She will next cover basic information about sleep, circadian rhythms, and performance, including how sleep works on earth. She will explain how people have circadian rhythms of different lengths and how the circadian clock has to be re-set each day. She will also describe how jet-lag works as an example of what happens during circadian misalignment. Dr. Flynn-Evans will describe how modest circadian misalignment affects airline pilots during short-haul flights. She will also describe how sleep is different in space and will highlight the challenges that astronauts face in low-earth orbit. She will discuss how astronauts have a shorter sleep duration in space relative to on the ground and how their schedules can shift due to operational constraints. She will also describe how these issues affect alertness and performance. She will then discuss how sleep and scheduling may be different on a long-duration mission to Mars. She will discuss the differences in light and day length on earth and mars and illustrate how those differences pose significant challenges to sleep and circadian rhythms.

Flynn-Evans, Erin↗

NASA NTRSDate not supplied

Oculometric Analysis of Saccadic Compensation for Visual Motion Processing Impairment due to Alcohol and Sleep Disruption

The Visuomotor Control Laboratory at Ames Research Center has developed a 5-minute ocular tracking test that computes 21 largely independent metrics of visuomotor performance, reflecting neural signal processing along a number of distinct pathways through cortex, brainstem, and cerebellum. Human sensorimotor performance is resilient to the challenges and stressors of many operational environments, in part, because overall performance is achieved through multiple parallel systems. Our multidimensional oculometrics allow us to examine impacts on these sub-components separately. To illustrate this, we contrasted the effects of two mild neural stressors, acute sleep-deprivation and low-dose alcohol. We have previously shown that, in both cases, oculometric analysis is a highly sensitive indicator of impairment. Here we quantified not only the observed impact on the performance of one sub-system, smooth pursuit, which uses high-level cortical processing of visual motion to track a moving object, but also the observed (partial) compensation by an evolutionarily older mid-brain and brainstem subsystem, saccades, which generates jumps in eye position to catch up with the target when smooth pursuit is inadequate. Specifically, we examined the dose-response (effect size vs. dose size) of the ground lost (pursuit deficit) and the ground recouped (saccadic compensation) across three separate studies – acute low-dose alcohol administration (16 subjects), acute sleep loss (12 subjects), and acute sleep loss with caffeine intervention (9 subjects). We computed the dose-response slopes using linear regression. The figure below shows that, in the case of acute sleep deprivation, the resulting slopes for ground lost and ground recouped (mean ± SE across subjects) were significantly different (paired t-test, t(11) = 5.17, p < 0.001), indicating poor saccadic compensation. However, when sleep loss was coupled with caffeine ingestion, ground lost was decreased and ground recouped increased such that the slopes were no longer different (t(8) = -0.05, p = 0.965). With alcohol, the two slopes were large albeit not significantly different (t(15) = 0.96, p = 0.351), indicating significant pursuit impairment but effective saccadic compensation. Our findings show that sleep deprivation and alcohol affect oculomotor performance differently. Low-dose alcohol effects appear predominantly cortical, with effective brainstem compensation. Sleep loss and circadian disruption however appears to affect both cortical and brainstem pathways with caffeine providing an effective countermeasure to both effects. Beyond the mere detection of impairment, our oculometric assessment allows us to characterize the nature of the deficit, to provide insight into the neural substrate, and to assess the effectiveness of countermeasures.

pursuit↗

NASA NTRS2021

Circadian Rhythms and Homeostatic Mechanisms for Sleep Regulation

This chapter examines circadian rhythms and homeostatic mechanisms for sleep regulation. It reviews the current evidence describing the two-process model of sleep regulation and how to assess disruption to either of these sleep drives. This chapter also reviews the role of the photic and non-photic resetting of the circadian rhythm and describes how some aspects of modern society can cause sleep and circadian disruption. Furthermore, this chapter describes how misalignment between the circadian rhythm and sleep homeostat, such as occurs during jet lag and shiftwork, can lead to sleep disruption. The short and long-term consequences of circadian misalignment are also reviewed.

Sleep↗

NASA NTRS2003

Sleep deprivation influences some but not all processes of supervisory attention

Does one night of sleep deprivation alter processes of supervisory attention in general or only a specific subset of such processes? Twenty college-aged volunteers, half female, performed a choice reaction time task. A cue indicated that compatible (e.g., right button, right-pointing arrow) or incompatible (e.g., left button, right-pointing arrow) responses were to be given to a stimulus that followed 50 or 500 ms later. The paradigm assessed response inhibition, task-shifting skill, and task strategy-processes inherent in supervisory attention. Performance, along with heart rate, was assessed for 12 hr following normal sleep or a night of complete sleep deprivation. Sleep deprivation altered neither preparation for task shifting nor response inhibition. The ability to use preparatory bias to speed performance did decrease with sleep deprivation. Sleep deprivation appears to selectively affect this supervisory attention process, which is perceived as an active effort to cope with a challenging task.

NASA Discipline Regulatory Physiology↗

NASA NTRS1999

Dose-response relationship between sleep duration and human psychomotor vigilance and subjective alertness

Although it has been well documented that sleep is required for human performance and alertness to recover from low levels after prolonged periods of wakefulness, it remains unclear whether they increase in a linear or asymptotic manner during sleep. It has been postulated that there is a relation between the rate of improvement in neurobehavioral functioning and rate of decline of slow-wave sleep and/or slow-wave activity (SWS/SWA) during sleep, but this has not been verified. Thus, a cross-study comparison was conducted in which dose-response curves (DRCs) were constructed for Stanford Sleepiness Scale (SSS) and Psychomotor Vigilance Task (PVT) tests taken at 1000 hours by subjects who had been allowed to sleep 0 hours, 2 hours, 5 hours or 8 hours the previous night. We found that the DRCs to each PVT metric improved in a saturating exponential manner, with recovery rates that were similar [time constant (T) approximately 2.14 hours] for all the metrics. This recovery rate was slightly faster than, though not statistically significantly different from, the reported rate of SWS/SWA decline (T approximately 2.7 hours). The DRC to the SSS improved much more slowly than psychomotor vigilance, so that it could be fit equally well by a linear function (slope = -0.26) or a saturating exponential function (T = 9.09 hours). We conclude that although SWS/SWA, subjective alertness, and a wide variety of psychomotor vigilance metrics may all change asymptotically during sleep, it remains to be determined whether the underlying physiologic processes governing their expression are different.

Non-NASA Center↗

NASA NTRS2005

Circadian rhythms, sleep, and performance in space

Maintaining optimal alertness and neurobehavioral functioning during space operations is critical to enable the National Aeronautics and Space Administration's (NASA's) vision "to extend humanity's reach to the Moon, Mars and beyond" to become a reality. Field data have demonstrated that sleep times and performance of crewmembers can be compromised by extended duty days, irregular work schedules, high workload, and varying environmental factors. This paper documents evidence of significant sleep loss and disruption of circadian rhythms in astronauts and associated performance decrements during several space missions, which demonstrates the need to develop effective countermeasures. Both sleep and circadian disruptions have been identified in the Behavioral Health and Performance (BH&P) area and the Advanced Human Support Technology (AHST) area of NASA's Bioastronautics Critical Path Roadmap. Such disruptions could have serious consequences on the effectiveness, health, and safety of astronaut crews, thus reducing the safety margin and increasing the chances of an accident or incident. These decrements oftentimes can be difficult to detect and counter effectively in restrictive operational environments. NASA is focusing research on the development of optimal sleep/wake schedules and countermeasure timing and application to help mitigate the cumulative effects of sleep and circadian disruption and enhance operational performance. Investing research in humans is one of NASA's building blocks that will allow for both short- and long-duration space missions and help NASA in developing approaches to manage and overcome the human limitations of space travel. In addition to reviewing the current state of knowledge concerning sleep and circadian disruptions during space operations, this paper provides an overview of NASA's broad research goals. Also, NASA-funded research, designed to evaluate the relationships between sleep quality, circadian rhythm stability, and performance proficiency in both ground-based simulations and space mission studies, as described in the 2003 NASA Task Book, will be reviewed.

Review↗

NASA NTRS1973

Sleep-monitoring, experiment M133

The Skylab sleep-monitoring experiment simulated the timelines and environment expected during a 56-day Skylab mission. Two crewmembers utilized the data acquisition and analysis hardware, and their sleep characteristics were studied in an online fashion during a number of all night recording sessions. Comparison of the results of online automatic analysis with those of postmission visual data analysis was favorable, confirming the feasibility of obtaining reliable objective information concerning sleep characteristics during the Skylab missions. One crewmember exhibited definite changes in certain sleep characteristics (e.g., increased sleep latency, increased time Awake during first third of night, and decreased total sleep time) during the mission.

Frost, J. D., Jr.↗

NASA NTRS1986

Nocturnal sleep and daytime alertness of aircrew after transmeridian flights

The nocturnal sleep and daytime alertness of aircrew were studied by electroencephalography and the multiple sleep latency test. After a transmeridian flight from London To San Francisco, sleep onset was faster and, although there was increased wakefulness during the second half of the night, sleep duration and efficiency over the whole night were not changed. The progressive decrease in sleep latencies observed normally in the multiple sleep latency test during the morning continued throughout the day after arrival. Of the 13 subjects, 12 took a nap of around 1-h duration in the afternoon preceding the return flight. These naps would have been encouraged by the drowsiness at this time and facilitated by the departure of the aircraft being scheduled during the early evening. An early evening departure had the further advantage that the circadian increase in vigilance expected during the early part of the day would occur during the latter part of the return flight.

Nicholson, Anthony N.↗

NASA NTRS1989

Adjustment of sleep and the circadian temperature rhythm after flights across nine time zones

The adjustment of sleep-wake patterns and the circadian temperature rhythm was monitored in nine Royal Norwegian Airforce volunteers operating P-3 aircraft during a westward training deployment across nine time zones. Subjects recorded all sleep and nap times, rated nightly sleep quality, and completed personality inventories. Rectal temperature, heart rate, and wrist activity were continuously monitored. Adjustment was slower after the return eastward flight than after the outbound westward flight. The eastward flight produced slower readjustment of sleep timing to local time and greater interindividual variability in the patterns of adjustment of sleep and temperature. One subject apparently exhibited resynchronization by partition, with the temperature rhythm undergoing the reciprocal 15-h delay. In contrast, average heart rates during sleep were significantly elevated only after westward flight. Interindividual differences in adjustment of the temperature rhythm were correlated with some of the personality measures. Larger phase delays in the overall temperature waveform (as measured on the 5th day after westward flight) were exhibited by extraverts, and less consistently by evening types.

Gander, Philippa H.↗

NASA NTRS1991

Adaptation of sleep and circadian rhythms to the Antarctic summer - A question of zeitgeber strength

Adaptation of sleep and circadian rhythms was examined in three temperate zone dwellers arriving in Antarctica during summer. Rectal temperature, wrist activity, and heart rate were monitored continuously, sleep timing and quality noted on awakening, and mood and fatigue rated every 2 h while awake. Sleep was poorer in 2/3 subjects in Antarctica, where all subjects reported more difficulty rising. Sleep occurred at the same clock times in New Zealand and Antarctica, however, the rhythms of temperature, activity, and heart rate underwent a delay of about of 2 h. The subject with the most Antarctic experience had the least difficulty adapting to sleeping during constant daylight. The subject with the most delayed circadian rhythms had the most difficulty. The delay in the circadian system with respect to sleep and clock time is hypothesized to be due to differences in zeitgeber strength and/or zeitgeber exposure between Antarctica and New Zealand.

Gander, Philippa H.↗

NASA NTRS1996

Evaluating Sleep Disturbance: A Review of Methods

There are three general approaches to evaluating sleep disturbance in regards to noise: subjective, behavioral, and physiological. Subjective methods range from standardized questionnaires and scales to self-report measures designed for specific research questions. There are two behavioral methods that provide useful sleep disturbance data. One behavioral method is actigraphy, a motion detector that provides an empirical estimate of sleep quantity and quality. An actigraph, worn on the non-dominant wrist, provides a 24-hr estimate of the rest/activity cycle. The other method involves a behavioral response, either to a specific probe or stimuli or subject initiated (e.g., indicating wakefulness). The classic, gold standard for evaluating sleep disturbance is continuous physiological monitoring of brain, eye, and muscle activity. This allows detailed distinctions of the states and stages of sleep, awakenings, and sleep continuity. Physiological delta can be obtained in controlled laboratory settings and in natural environments. Current ambulatory physiological recording equipment allows evaluation in home and work settings. These approaches will be described and the relative strengths and limitations of each method will be discussed.

Smith, Roy M.↗

NASA NTRS1994

Effect of inducing nocturnal serum melatonin concentrations in daytime on sleep, mood, body temperature, and performance

We examined effects of very low doses of melatonin (0.1-10 mg, orally) or placebo, administered at 1145 h, on sleep latency and duration, mood, performance, oral temperature, and changes in serum melatonin levels in 20 healthy male volunteers. A repeated-measure double-blind Latin square design was used. Subjects completed a battery of tests designed to assess mood and performance between 0930 and 1730 h. The sedative-like effects of melatonin were assessed by a simple sleep test: at 1330 h subjects were asked to hold a positive pressure switch in each hand and to relax with eyes closed while reclining in a quiet darkened room. Latency and duration of switch release, indicators of sleep, were measured. Areas under the time-melatonin concentration curve varied in proportion to the different melatonin doses ingested, and the 0.1- and 0.3-mg doses generated peak serum melatonin levels that were within the normal range of nocturnal melatonin levels in untreated people. All melatonin doses tested significantly increased sleep duration, as well as self-reported sleepiness and fatigue, relative to placebo. Moreover, all of the doses significantly decreased sleep-onset latency, oral temperature, and the number of correct responses on the Wilkinson auditory vigilance task. These data indicate that orally administered melatonin can be a highly potent hypnotic agent; they also suggest that the physiological increase in serum melatonin levels, which occurs around 2100 h daily, may constitute a signal initiating normal sleep onset.

Non-NASA Center↗

NASA NTRS2012

Assessing Individual Differences in Adaptation to Extreme Environments: A 36-Hour Sleep Deprivation Study

In space, astronauts may experience effects of cumulative sleep loss due to demanding work schedules that can result in cognitive performance impairments, mood state deteriorations, and sleep-wake cycle disruption. Individuals who experience sleep deprivation of six hours beyond normal sleep times experience detrimental changes in their mood and performance states. Hence, the potential for life threatening errors increases exponentially with sleep deprivation. We explored the effects of 36-hours of sleep deprivation on cognitive performance, mood states, and physiological responses to identify which metrics may best predict fatigue induced performance decrements of individuals.

Martinez, Jacqueline↗

NASA NTRS2015

Daytime Cognitive Performance in Response to Sunlight or Fluorescent Light Controlling for Sleep Duration

Light is the primary synchronizer of the human circadian rhythm and also has acute alerting effects. Our study involves and comparing the alertness, performance and sleep of participants in the NASA Ames Sustainability Base, which uses sunlight as its primary light source, to in a traditional office building which uses overhead florescent lighting and varying exposure to natural light. The purpose of this study is to determine whether the use of natural lighting as a primary light source improves daytime cognitive function and promotes nighttime sleep. Participants from the Sustainability Base will be matched by gender and age to individuals working in other NASA buildings. In a prior study we found no differences in performance between those working in the Sustainability Base and those working in other buildings. Unexpectedly, we found that the average sleep duration among participants in both buildings was short, which likely obscured our ability to detect a difference the effect of light exposure on alertness. Given that such sleep deprivation has negative effects on cognitive performance, in this iteration of the study we are asking the participants to maintain a regular schedule with eight hours in bed each night in order to control for the effect of self-selected sleep restriction. Over the course of one week, we will ask the participants to wear actiwatches continuously, complete a psychomotor vigilance task (PVT) and digit symbol substitution task (DSST) three times per day, and keep daily sleepwork diaries. We hope that this study will provide data to support the idea that natural lighting and green architectural design are optimal to enhance healthy nighttime sleep patterns and daytime cognitive performance.

cognitive performance↗

NASA NTRS2020

A Summary Of: Collecting Sleep, Circadian, Fatigue, and Performance Data in Complex Operational Environments

Sleep loss and circadian misalignment contribute to a meaningful proportion of operational accidents and incidents. Countermeasures and work scheduling designs aimed at mitigating fatigue are typically evaluated in controlled laboratory environments, but the effectiveness of translating such strategies to operational environments can be challenging to assess. This manuscript summarizes an approach for collecting sleep, circadian, fatigue, and performance data in a complex operational environment. We studied 44 airline pilots over 34 days while they flew a fixed schedule, which included a baseline data collection with 5 days of mid-morning flights, four early flights, four high-workload mid-day flights, and four late flights that landed after midnight. Each work block was separated by 3-4 days of rest. To assess sleep, participants wore a wrist-worn research-validated activity monitor continuously and completed daily sleep diaries. To assess the circadian phase, pilots were asked to collect all urine produced in four or eight hourly bins during the 24 h after each duty block for the assessment of 6-sulfatoxymelatonin (aMT6s), which is a biomarker of the circadian rhythm. To assess subjective fatigue and objective performance, participants were provided with a touchscreen device used to complete the Samn-Perelli Fatigue Scale and Psychomotor Vigilance Task (PVT) during and after each flight, and at wake-time, mid-day, and bedtime. Using these methods, it was found that sleep duration was reduced during early starts and late finishes relative to baseline. Circadian phase shifted according to duty schedule, but there was a wide range in the aMT6s peak between individuals on each schedule. PVT performance was worse on the early, high-workload, and late schedules relative to baseline. Overall, the combination of these methods was practical and effective for assessing the influence of sleep loss and circadian phase on fatigue and performance in a complex operational environment.

Arsintescu, Lucica↗

NASA NTRS2001

Microgravity reduces sleep-disordered breathing in humans

To understand the factors that alter sleep quality in space, we studied the effect of spaceflight on sleep-disordered breathing. We analyzed 77 8-h, full polysomnographic recordings (PSGs) from five healthy subjects before spaceflight, on four occasions per subject during either a 16- or 9-d space shuttle mission and shortly after return to earth. Microgravity was associated with a 55% reduction in the apnea-hypopnea index (AHI), which decreased from a preflight value of 8.3 +/- 1.6 to 3.4 +/- 0.8 events/h inflight. This reduction in AHI was accompanied by a virtual elimination of snoring, which fell from 16.5 +/- 3.0% of total sleep time preflight to 0.7 +/- 0.5% inflight. Electroencephalogram (EEG) arousals also decreased in microgravity (by 19%), and this decrease was almost entirely a consequence of the reduction in respiratory-related arousals, which fell from 5.5 +/- 1.2 arousals/h preflight to 1.8 +/- 0.6 inflight. Postflight there was a return to near or slightly above preflight levels in these variables. We conclude that sleep quality during spaceflight is not degraded by sleep-disordered breathing. This is the first direct demonstration that gravity plays a dominant role in the generation of apneas, hypopneas, and snoring in healthy subjects.

short duration↗

NASA NTRS2023

Sleep Issues in Aviation and Space

This article describes the factors that cause sleep issues in aviation and spaceflight. There are many causes of sleep disruption that are common to both domains, including, irregular schedules, circadian misalignment, and inadequate sleep environment. There are also factors that are unique to each type of operation that may lead to the manifestation of sleep disorders among these populations. Each of these factors, and their subsequent impact on sleep, are reviewed in this article.

Astronaut↗

NASA NTRS2001

A sleep diary and questionnaire study of naturally short sleepers

Whereas most people require more than 6 h of sleep to feel well rested, there appears to be a group of people who can function well on between 3 and 6 h of sleep. The aims of the present study were to compare 12 naturally short (3-6 h) sleepers (9 males 3 females, mean age 39.6 years, SD age 10.1 years) recruited by a media publicity campaign with age, gender and chronotype matched medium length (7-8.5 h) sleepers on various measures. Measurement instruments included diaries and questionnaires to assess sleep duration and timing, as well as questionnaire assessments of sleep pathology, morningness-eveningness, extroversion, neuroticism, pathological daytime sleepiness, subclinical hypomania, optimism, depressive symptoms, exercise, and work habits. Few measures showed reliable differences between naturally short sleepers and controls except the obvious ones related to sleep duration. There was, however, some evidence for subclinical hypomanic symptoms in naturally short sleepers.

NASA Discipline Regulatory Physiology↗