Operational Evaluation of a Photic Countermeasure to Improve Alertness, Performance, and Mood During Nightshift Work on a 105-day Simulated Human Exploration Mission to Mars
Operational Evaluation of a Photic Countermeasure to Improve Alertness, Performance, and Mood During Nightshift Work on a 105-day Simulated Human Exploration Mission to Mars
The success of human expedition missions critically depend on the ability of the crew to be alert and maintain high levels of cognitive function while operating complex, technical equipment. Optimal human health, performance and safety during space flight requires sufficient sleep and synchrony between the circadian pacemaker-which regulates the timing of sleep, endocrine function, alertness and performance-and the timing of the imposed sleep-wake schedule.
Crewmembers of the 105-day simulation study will be required to work one night shift every sixth night. This schedule will likely result in sleep loss and circadian misalignment, especially when lighting conditions are similar to those that crewmembers experience during spaceflight. External mission controllers will work 24-hour shifts, also resulting in both sleep loss and circadian misalignment.
It has been well documented in laboratory and field studies that both working the night shift and working extended duration shifts result in decrement alertness, performance and mood. In addition to the negative effects that night shift work has on alertness, performance and mood, shift work causes significant short and long-term health problems. Shift workers, particularly night shift workers who invert their normal sleep/wake schedule, suffer for several reasons. First, their endogenous circadian rhythms and the imposed sleep/work schedule are typically out of phase. This is similar to the experience of jet lag. However, while environment cues (e.g., sunrise, sunset, the timing of meals and sleep) enable travelers to adapt quickly to a new time zone, crewmembers in the 105-day simulation will be unable to do so because they will only spend one night of every five working. When working the night shift, the timing of meals, work, and sleep will therefore be out of phase with the normal entrained phase of the circadian timing system. Ingestion of meals at an inappropriate circadian phase results in impaired metabolism, likely underlying the gastrointestinal and metabolic problems experienced by shift workers. Second, this circadian misalignment leads to a substantial loss of sleep efficiency during the (daytime) sleep period, independent of, and in addition to, environmental obstacles to sleep (e.g., noise, light, other crewmembers). Third, misalignment of circadian phase coupled with sleep loss will each result in deterioration of alertness and impairment of performance during the night. Since these adverse effects are particularly acute on the first night of work, the plan for crewmembers on the Mars 105 mission to work the midnight shift every sixth night will subject them repeatedly to the performance impairments associated with acute circadian misalignment and acute sleep deprivation.
Lighting Countermeasure. Our group at the Harvard Medical School has successfully developed and tested effective photic countermeasures to alleviate circadian misalignment and improve alertness, performance and mood in night shift workers. The most effective countermeasure to circadian alignment is appropriately-timed and sufficiently intense light. Light also acutely improves alertness, performance and mood. Most recently it has been reported that short wavelength light has been shown to be most effective for both resetting circadian rhythms and acutely improving performance during night work via antecedent suppression of the soporific hormone melatonin.
These photic countermeasures have been tested in individual subjects living in laboratory simulations (Countermeasures readiness level/Technology readiness level 7; Evaluation with human subjects in controlled laboratory simulating operational spaceflight environment). The next critical step is to evaluate our countermeasures in an operational simulation of space flight that includes study of the interaction among crew members in a high fidelity simulation (Countermeasures readiness level/Technology readiness level 8; Validation with human subjects in actual operational spaceflight to demonstrate efficacy and operational feasibility).
Adequate sleep and circadian alignment are critical to maintaining the health and performance of expedition mission crewmembers. Testing of the developed lighting countermeasure in a high fidelity operational environment imitating the conditions of a future expedition mission (e.g., to Mars) is critical to ensure countermeasure readiness and to reduce the risk of human performance errors due to factors related to circadian disruption, sleep loss and fatigue. Development and testing of this photic countermeasure for mission controllers working 24-hour shifts will further ensure the success of the future long duration expedition missions.
The objective and tasks of the investigation.
The purpose of this study is to validate the efficacy and operational feasibility of a photic countermeasure to improve alertness and performance during night shift work occurring during a simulated expedition mission. We propose to address the following specific aims:
Specific Aim 1. Evaluate the feasibility of monitoring sleep and circadian neuroendocrine rhythms in a high fidelity operational simulation of a 105-day expedition mission, in preparation for such monitoring in longer duration simulations that include the 24.65-hour Martian sol.
Specific Aim 2. Test the hypothesis that sleep, alertness, performance and mood will be impaired during acute circadian misalignment associated with night shift work operations in a high fidelity operational simulation of a 105-day expedition mission;
Specific Aim 3. Test the hypothesis that alertness, performance and mood of crewmembers exposed to shorter wavelength light (with a peak wavelength between 485 to 525 nm) during the night shift in the console monitoring room will be significantly better than the alertness, performance and mood of those same crewmembers when they are exposed to intermediate wavelength light (with a peak wavelength of either 545 nm to 555 nm) or longer wavelength light (620 nm to 690 nm) during the night shift. We hypothesize that these improvements in alertness, performance and mood will be associated with suppression of the pineal hormone melatonin. Melatonin levels are expected to be lowest across the night shift during exposure to the short 485 nm-525 nm light; low for the first quartile of the night shift during exposure to the intermediate wavelength 545 nm-555 nm light; and highest during exposure to the longer wavelength 620 nm-690 nm light. This aim will permit us to evaluate the feasibility of deploying lighting countermeasures (Light Tower; Sunnex Biotechnologies Winnipeg, Manitoba, Canada; ww.Sunnexbiotech.com) in the control panel room (inside the module EU-150) to assess the effects of this wavelength of light on alertness, performance, and subsequent sleep, in preparation for deploying lighting countermeasures in longer duration simulations that include the 24.65-hour Martian sol. Subjects will be randomized to the three lighting conditions using a balanced Latin square design.
Specific aim 4. Test the hypothesis that the alertness, performance and mood of the external mission controllers will be impaired during the final third of their extended duration, 24-hour work shifts as compared with the first third of that same work shift. We anticipate that the acute total sleep deprivation and circadian misalignment associated with hours 16 through 24 of their work shift will significantly degrade their alertness, performance and mood.
Specific aim 5. Test the hypothesis that the alertness, performance and mood of external mission controllers exposed to shorter wavelength light (with a peak wavelength between 485 to 525 nm) during the final third of their extended duration work shift will be significantly better than the alertness, performance and mood of those same crewmembers when they are exposed to intermediate wavelength light (with a peak wavelength of either 545 nm to 555 nm) or longer wavelength light (620 nm to 690 nm) during the final third of their extended duration work shift.
The purpose of the proposed studies is to address five specific hypotheses aimed at validating methods to collect data to monitor performance, sleep and circadian rhythms in an operational environment. We also plan to evaluate the efficacy of a photic countermeasure designed to improve alertness, performance, mood during acute circadian misalignment during the 105-day mission in which crewmembers will be required to be on duty in the console monitoring room during the night shift every sixth night. These five hypotheses are based on the results of our preliminary data which indicate that: (a) night shift workers who invert their normal sleep/wake schedule experience sleep loss, decreased alertness and performance; (b) individual working extended duration, 24-hour shifts experience sleep loss and impaired alertness, performance and mood, especially during a critical zone of vulnerability between the 16th and 24th hours of such extended duration work shifts; (c) shorter wavelength light acutely suppresses melatonin and increases alertness, performance and mood during night work; and (d) shorter wavelength visible light is more effective than intermediate or longer wavelength light at suppressing melatonin and increasing alertness, performance and mood during the night.
The Institute of Biomedical Problems (IBMP) selected the participants for the 105-day simulated spaceflight mission. All participants that were selected by the IBMP were eligible to participate in this study.
Inclusion
Exclusion