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NASA NTRS1984

A review of human physiological and performance changes associated with desynchronosis of biological rhythms

This review discusses the effects, in the aerospace environment, of alterations in approximately 24-h periodicities (circadian rhythms) upon physiological and psychological functions and possible therapies for desynchronosis induced by such alterations. The consequences of circadian rhythm alteration resulting from shift work, transmeridian flight, or altered day lengths are known as desynchronosis, dysrhythmia, dyschrony, jet lag, or jet syndrome. Considerable attention is focused on the ability to operate jet aircraft and manned space vehicles. The importance of environmental cues, such as light-dark cycles, which influence physiological and psychological rhythms is discussed. A section on mathematical models is presented to enable selection and verification of appropriate preventive and corrective measures and to better understand the problem of dysrhythmia.

Winget, C. M.↗

NASA NTRS1989

The biological clock of Neurospora in a microgravity environment

The effects of simulated microgravity (via the use of a slowly rotating clinostat), altered orientation (via alterations in the vector of a 1-g force), and hypergravity (via centrifugation) on the circadian rhythm of conidiation in Neurospora crassa were investigated. It was found that the clinostat, while capable of producing some of the microgravity effects seen in space (Sulzman, 1984), did not produce major repeatable results. Similarly, alterations of the vector of a 1-g gravity load were not adequate simulations of space flight on the conidiation rhythm. The results on the acute and chronic exposures to hypergravity demonstrated that chronic exposure of Neurospora to a 3-g force had no damping effect. On the other hand, an acute 10-min exposure to this hypergravity (the lift-off conditions) was found to cause significant damping on the circadian rhythm of conidiation. This effect was eliminated by a brief light pulse given 36 hrs after the exposure to 3 g.

Ferraro, James S.↗

NASA NTRS1989

Temperature regulation in rats exposed to a 2 G field

The regulation of body temperature involves both homeostatic and circadian control systems. Both systems are influenced by exposure to hyperdynamic fields and demonstrate acute responses that eventually recover to an adapted level. This experiment examined both the homeostatic and circadian responses of body temperature to a separate environmental challenge (high frequency light/dark cycles) during exposure to a 2 G hyperdynamic field.

Ishihama, Linda M.↗

NASA NTRS1989

Significance of light and social cues in the maintenance of temporal organization in man

The effects of light:darkness (LD) cycles and social interaction on the response to long-term confinement (105 days) were investigated experimentally in three groups of three male subjects aged 20-24 years. Data from measurements of physiological parameters indicating changes in circadian rhythms are presented in graphs and analyzed; it is found that the LD-induced rhythm changes observed in previous studies of subjects isolated singly do not appear when subjects are confined in groups of three, suggesting a positive adaptive effect of social contact. In one subject who was transferred to a different group at day 84, hostile social interactions and poor circadian-rhythm entrainment were observed; the possible reasons for this response are considered.

Winget, C. M.↗

NASA NTRS1992

An on-orbit viewpoint of life sciences research

As a Payload Specialist and a life science researcher, I want to present several issues that impact life science research in space. During early space station operations, life science and other experiments will be conducted in a time-critical manner and there will be the added duties of both space shuttle and space station systems operation (and the concomittent training overhead). Life sciences research is different from other science research done in space because the crew is involved both as an operator and as a subject. There is a need for pre- and post-flight data collection as well as in flight data collection. It is imperative that the life science researcher incorporate the crew members into their team early enough in the training cycle to fully explain the science and to make the crew aware of the importance and sensitivities of the experiment. During the pre-flight phase, the crew is incredibly busy with a myriad of duties. Therefore, it is difficult to get 'pristine' subjects for the baseline data collection. There are also circadian shifts, travel, and late nights to confound the data. During this time it is imperative that the researcher develop, along with the crew, a realistic estimate of crew-time required for their experiment. In flight issues that affect the researcher are the additional activities of the crew, the stresses inherent in space flight, and the difficulty of getting early in-flight data. During SSF activities, the first day or two will be taken up with rendezvous and docking. Other issues are the small number of subjects on any given flight, the importance of complete and concise procedures, and the vagaries of on-board data collection. Post flight, the crew is tired and experiences a 'relaxation.' This along with circadian shifts and rapid re-adaptation to 1-g make immediate post-flight data collection difficult. Finally, the blending of operational medicine and research can result in either competition for resources (crew time, etc.) or influence on the physiological state of the crew. However, the unique opportunity to conduct research in an environment that cannot be duplicated on Earth outweighs the 'challenges' that exist for space life researchers.

Lichtenberg, Byron K.↗

NASA NTRS1992

Thermoregulatory responses of rhesus monkeys during spaceflight

This study examines the activity, axillary temperature (T(ax)), and ankle skin temperature (Tsk) of two male Rhesus monkeys exposed to microgravity in space. The animals were flown on a Soviet biosatellite mission (COSMOS 1514). Measurements on the flight animals, as well as synchronous flight controls, were performed in the Soviet Union. Additional control studies were performed in the United States to examine the possible role of metabolic heat production in the T(ax) response observed during the spaceflight. All monkeys were exposed to a 24-h light-dark cycle (LD 16:8) throughout these studies. During weightlessness, T(ax) in both flight animals was lower than on earth. The largest difference (0.75 degree C) occurred during the night. There was a reduction in mean heart rate and Tsk during flight. This suggests a reduction in both heat loss and metabolic rate during spaceflight. Although the circadian rhythms in all variables were present during flight, some differences were noted. For example, the amplitude of the rhythms in Tsk and activity were attenuated. Furthermore, the T(ax) and activity rhythms did not have precise 24.0 hour periods and may have been externally desynchronized from the 24-h LD cycle. These data suggest a weakening of the coupling between the internal circadian pacemaker and the external LD synchronizer.

Sulzman, F. M.↗

NASA NTRS1994

Flight controller alertness and performance during MOD shiftwork operations

Decreased alertness and performance associated with fatigue, sleep loss, and circadian disruption are issues faced by a diverse range of shiftwork operations. During STS operations, MOD personnel provide 24 hr. coverage of critical tasks. A joint JSC and ARC project was undertaken to examine these issues in flight controllers during MOD shiftwork operations. An initial operational test of procedures and measures was conducted during STS-53 in Dec. 1992. The study measures included a background questionnaire, a subjective daily logbook completed on a 24 hr. basis (to report sleep patterns, work periods, etc.), and an 8 minute performance and mood test battery administered at the beginning, middle, and end of each shift period. Seventeen Flight controllers representing the 3 Orbit shifts participated. The initial results clearly support further data collection during other STS missions to document baseline levels of alertness and performance during MOD shiftwork operations. These issues are especially pertinent for the night shift operations and the acute phase advance required for the transition of day shift personnel into the night for shuttle launch. Implementation and evaluation of the countermeasure strategies to maximize alertness and performance is planned. As STS missions extend to further extended duration orbiters, timelines and planning for 24 circadian disruption will remain highly relevant in the MOD environment.

Kelly, Sean M.↗

NASA NTRS1994

Ground and space flight experiments of the effects of light, sound and/or temperature on animals

Papers on the following topics are presented: (1) rat long term habitability and breeding under low light intensity (5 lux); (2) effects of low light intensity on the rat circadian system; (3) effects of sound/noise on the circadian system of rats; (4) temperature related problems involving the animal enclosure modules (AEM) lighting system; and (5) NASA AEM filter test 92/93 (Rats).

Holley, Daniel C.↗

NASA NTRS1993

The regulation of rat activity following exposure to hyperdynamic fields

The microgravity of space flight and the hyperdynamic fields produced via centrifugation have allowed researchers to examine the effect of altered gravitational environments on the regulation of physiological systems. In this study, a high frequency light/dark cycle was provided for 24 hours as an environmental challenge to assess the recovery of homeostatic and circadian components of physiological regulation in rats. For example, the nocturnal rat exhibited a homeostatic increase in body temperature during the dark periods and a decrease during the light periods. In addition, the magnitude of the body temperature response exhibits a time of day variation demonstrating the effect on circadian regulation.

Fuller, Charles A.↗

NASA NTRS1993

The 1993 Gordon Research Conference on Chronobiology

The study of biological timekeeping is now at a particularly fertile stage, encompassing multiple levels of biological organization, recruiting a wide array of disciplines and methodologies and uniting a host of investigators. This report summarizes a research conference on Chronobiology. Some of the topics focused on transcriptional and translational mechanisms of circadian rhythmicity, with discussions of putative 'clock genes' in cyanobacteria, algae, fungi, fruitflies, and hamsters. Cellular analysis, with emphasis on photoreceptors in frogs, neurons in molluscs, and testis in moths was addressed. New methods for investigating the circadian clock in the suprachiasmatic nucleus were introduced.

Schwartz, William J.↗

NASA NTRS1994

Effects of light on brain and behavior

It is obvious that light entering the eye permits the sensory capacity of vision. The human species is highly dependent on visual perception of the environment and consequently, the scientific study of vision and visual mechanisms is a centuries old endeavor. Relatively new discoveries are now leading to an expanded understanding of the role of light entering the eye in addition to supporting vision, light has various nonvisual biological effects. Over the past thirty years, animal studies have shown that environmental light is the primary stimulus for regulating circadian rhythms, seasonal cycles, and neuroendocrine responses. As with all photobiological phenomena, the wavelength, intensity, timing and duration of a light stimulus is important in determining its regulatory influence on the circadian and neuroendocrine systems. Initially, the effects of light on rhythms and hormones were observed only in sub-human species. Research over the past decade, however, has confirmed that light entering the eyes of humans is a potent stimulus for controlling physiological rhythms. The aim of this paper is to examine three specific nonvisual responses in humans which are mediated by light entering the eye: light-induced melatonin suppression, light therapy for winter depression, and enhancement of nighttime performance. This will serve as a brief introduction to the growing database which demonstrates how light stimuli can influence physiology, mood and behavior in humans. Such information greatly expands our understanding of the human eye and will ultimately change our use of light in the human environment.

Brainard, George C.↗

NASA NTRS1996

Crew Factors in Flight Operations 7: Psychophysiological Responses to Overnight Cargo Operations

To document the psychophysiological effects of flying overnight cargo operations, 41 B-727 crew members (average age 38 yr) were monitored before, during, and after one of two typical 8-day trip patterns. During daytime layovers, the average sleep episode was 3 hr (41%) shorter than nighttime sleeps and was rated as lighter, less restorative, and poorer overall. Sleep was frequently split into several episodes and totaled 1.2 hr less per 24 hr than on pretrip days. Each trip pattern included a night off, which was an effective countermeasure against the accumulating sleep debt. The organization of sleep during daytime layovers reflected the interaction of duty timing with circadian physiology. The circadian temperature rhythm did not adapt completely to the inverted wake-rest schedule on duty days, being delayed by about 3 hr. Highest subjective fatigue and lowest activation occurred around the time of the temperature minimum. On duty days, reports of headaches increased by 400%, of congested nose by 200%, and of burning eyes by 900%. Crew members also reported eating more snacks. Compared with daytime short-haul air-transport operations, the overnight cargo trips included fewer duty and flight hours, and had longer layovers. Overnight cargo crews also averaged 5.4 yr younger than their daytime short-haul counterparts. On trips, both groups lost a comparable amount of sleep per 24 hr, but the overnight cargo crews had shorter individual sleep episodes and more broken sleep. These data clearly demonstrate that overnight cargo operations, like other night work, involve physiological disruption not found in comparable daytime operations.

Gander, Philippa H.↗

NASA NTRS1996

Biological Rhythms and Temperature Regulation in Rhesus Monkeys During Spaceflight

This program examined the influence of microgravity on temperature regulation and circadian timekeeping systems in Rhesus monkeys. Animals flown on the Soviet Biosatellite COSMOS 2229 were exposed to 11 2/3 days of microgravity. The circadian patterns temperature regulation, heart rate and activity were monitored constantly. This experiment has extended previous observations from COSMOS 1514 and 2044, as well as provided insights into the physiological mechanisms that produce these changes.

Fuller, Charles A.↗

NASA NTRS1999

Crew Factors in Flight Operations X: Alertness Management in Flight Operations

In response to a 1980 congressional request, NASA Ames Research Center initiated a Fatigue/Jet Lag Program to examine fatigue, sleep loss, and circadian disruption in aviation. Research has examined fatigue in a variety of flight environments using a range of measures (from self-report to performance to physiological). In 1991, the program evolved into the Fatigue Countermeasures Program, emphasizing the development and evaluation of strategies to maintain alertness and performance in operational settings. Over the years, the Federal Aviation Administration (FAA) has become a collaborative partner in support of fatigue research and other Program activities. From the inception of the Program, a principal goal was to return the information learned from research and other Program activities to the operational community. The objectives of this Education and Training Module are to explain what has been learned about the physiological mechanisms that underlie fatigue, demonstrate the application of this information in flight operations, and offer some specific fatigue counter-measure recommendations. It is intended for all segments of the aeronautics industry, including pilots, flight attendants, managers, schedulers, safety and policy personnel, maintenance crews, and others involved in an operational environment that challenges human physiological capabilities because of fatigue, sleep loss, and circadian disruption.

Rosekind, Mark R.↗

NASA NTRS1999

Cardiovascular Deconditioning in Humans: Human Studies Core

Major cardiovascular problems, secondary to cardiovascular deconditioning, may occur on extended space missions. While it is generally assumed that the microgravity state is the primary cause of cardiovascular deconditioning, sleep deprivation and disruption of diurnal rhythms may also play an important role. Factors that could be modified by either or both of these perturbations include: autonomic function and short-term cardiovascular reflexes, vasoreactivity, circadian rhythm of cardiovascular hormones (specifically the renin-angiotensin system) and renal sodium handling and hormonal influences on that process, venous compliance, cardiac mass, and cardiac conduction processes. The purpose of the Human Studies Core is to provide the infrastructure to conduct human experiments which will allow for the assessment of the likely role of such factors in the space travel associated cardiovascular deconditioning process and to develop appropriate countermeasures. The Core takes advantage of a newly-created Intensive Physiologic Monitoring (IPM) Unit at the Brigham and Women's Hospital, Boston, MA, to perform these studies. The Core includes two general experimental protocols. The first protocol involves a head down tilt bed-rest study to simulate microgravity. The second protocol includes the addition of a disruption of circadian rhythms to the simulated microgravity environment. Before and after each of these environmental manipulations, the subjects will undergo acute stressors simulating changes in volume and/or stress, which could occur in space and on return to Earth. The subjects are maintained in a rigidly controlled environment with fixed light/dark cycles, activity pattern, and dietary intake of nutrients, fluids, ions and calories.

Williams, Gordon↗

NASA NTRS1999

Renal and Cardio-Endocrine Responses in Humans to Simulated Microgravity

The volume regulating systems are integrated to produce an appropriate response to both acute and chronic volume changes. Their responses include changing the levels of the hormones and neural inputs of the involved systems and/or changing the responsiveness of their target tissues. Weightlessness during space travel produces a volume challenge that is unfamiliar to the organism. Thus, it is likely that these volume regulatory mechanisms may respond inappropriately, e.g., a decrease in total body volume in space and abnormal responses to upright posture and stress on return to Earth. A similar "inappropriateness" also can occur in disease states, e.g., congestive heart failure. While it is clear that weightlessness produces profound changes in sodium and volume homeostasis, the mechanisms responsible for these changes are incompletely understood. Confounding this analysis is sleep deprivation, common in space travel, which can also modify volume homeostatic mechanisms. The purpose of this project is to provide the required understanding and then to design appropriate countermeasures to reduce or eliminate the adverse effects of microgravity. To accomplish this we are addressing five Specific Aims: (1) To test the hypothesis that microgravity modifies the acute responsiveness of the renin-angiotensin-aldosterone system (RAAS) and renal blood flow; (2) Does simulated microgravity change the circadian rhythm of the volume- regulating hormones?; (3) Does simulated microgravity change the target tissue responsiveness to angiotensin 11 (AngII)?; (4) Does chronic sleep deprivation modify the circadian rhythm of the RAAS and change the acute responsiveness of this system to posture beyond what a microgravity environment alone does? and (5) What effect does salt restriction have on the volume homeostatic and neurohumoral responses to a microgravity environment? Because the RAAS plays a pivotal role in blood pressure control and volume homeostasis, it likely is a major mediator of the adaptive cardio-renal responses observed during space missions and is a special focus of this project. Thus, the overall goal of this project is to assess the impact of microgravity and sleep deprivation in humans on volume-regulating systems. To achieve this overall objective, we are evaluating renal blood flow and the status and responsiveness of the volume- regulating systems (RAAS, atrial natriuretic peptide and vasopressin), and the adrenergic system (plasma and urine catecholamines) in both simulated microgravity and normal gravity with and -Without sleep deprivation. Furthermore, the responses of the volume homeostatic mechanisms to acute stimulation by upright tilt testing, standing and exercise are being evaluated before and after achieving equilibrium with these interventions.

Williams, Gordon H.↗

NASA NTRS1999

Countermeasures to Neurobehavioral Deficits from Cumulative Partial Sleep Deprivation During Space Flight

This project is concerned with identifying ways to prevent neurobehavioral and physical deterioration due to inadequate sleep in astronauts during long-duration manned space flight. The performance capability of astronauts during extended-duration space flight depends heavily on achieving recovery through adequate sleep. Even with appropriate circadian alignment, sleep loss can erode fundamental elements of human performance capability including vigilance, cognitive speed and accuracy, working memory, reaction time, and physiological alertness. Adequate sleep is essential during manned space flight not only to ensure high levels of safe and effective human performance, but also as a basic regulatory biology critical to healthy human functioning. There is now extensive objective evidence that astronaut sleep is frequently restricted in space flight to averages between 4 hr and 6.5 hr/day. Chronic sleep restriction during manned space flight can occur in response to endogenous disturbances of sleep (motion sickness, stress, circadian rhythms), environmental disruptions of sleep (noise, temperature, light), and curtailment of sleep due to the work demands and other activities that accompany extended space flight operations. The mechanism through which this risk emerges is the development of cumulative homeostatic pressure for sleep across consecutive days of inadequate sleep. Research has shown that the physiological sleepiness and performance deficits engendered by sleep debt can progressively worsen (i.e., accumulate) over consecutive days of sleep restriction, and that sleep limited to levels commonly experienced by astronauts (i.e., 4 - 6 hr per night) for as little as 1 week, can result in increased lapses of attention, degradation of response times, deficits in complex problem solving, reduced learning, mood disturbance, disruption of essential neuroendocrine, metabolic, and neuroimmune responses, and in some vulnerable persons, the emergence of uncontrolled sleep attacks. The prevention of cumulative performance deficits and neuroendocrine disruption from sleep restriction during extended duration space flight involves finding the most effective ways to obtain sleep in order to maintain the high-level cognitive and physical performance functions required for manned space flight. There is currently a critical deficiency in knowledge of the effects of how variations in sleep duration and timing relate to the most efficient return of performance per unit time invested in sleep during long-duration missions, and how the nature of sleep physiology (i.e., sleep stages, sleep electroencephalographic [EEG] power spectral analyses) change as a function of sleep restriction and performance degradation. The primary aim of this project is to meet these critical deficiencies through utilization of a response surface experimental paradigm, testing in a dose-response manner, varying combinations of sleep duration and timing, for the purpose of establishing how to most effectively limit the cumulative adverse effects on human performance and physiology of chronic sleep restriction in space operations.

Dinges, David F.↗

NASA NTRS2000

Behavioral Health Support of NASA Astronauts for International Space Station Missions

Two areas of focus for optimizing behavioral health and human performance during International Space Station missions are 1) sleep and circadian assessment and 2) behavioral medicine. The Mir experience provided the opportunity to examine the use and potential effectiveness of tools and procedures to support the behavioral health of the crew. The experience of NASA has shown that on-orbit performance can be better maintained if behavioral health, sleep, and circadian issues are effectively monitored and properly addressed. For example, schedules can be tailored based upon fatigue level of crews and other behavioral and cognitive indicators to maximize performance. Previous research and experience with long duration missions has resulted in the development and upgrade of tools used to monitor fatigue, stress, cognitive function, and behavioral health. Self-assessment and objective tools such as the Spaceflight Cognitive Assessment Tool have been developed and refined to effectively address behavioral medicine countermeasures in space.

Sipes, Walter↗