Review of NASA's Evidence Reports on Human Health Risks 2016 Letter Report (2017) / Chapter Skim
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2016 Letter Report
2016 Letter Report
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, at the request of th National A e he Aeronautics annd Space Administration (NASA) and with g guidance from the Nation m nal Acadeemies' Standin Committe on Aerospa Medicine and the Med ng ee ace e dicine of Extreme En f nvironments, has establishe the Comm h ed mittee to Revie ew NASA Evidence Reports on Human Health Risks.
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COMMITTEE'S TASK AND OVERARCHING ISSUES To review the eight NASA evidence reports, the National Academies assembled a 13-member committee with expertise in aerospace medicine, occupational health, radiation medicine and radiological research, human performance, internal medicine, physiology and exercise science, behavioral health, sleep and circadian rhythms, psychiatry, aerospace engineering, otolaryngology, and biomedical informatics. Committee biographical sketches are included in Appendix B
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BOX 1 Review of NASA's Evidence Reports on Human Health Risks Statement of Task NASA has requested a study to provide an independent review of more than 30 evidence reports on human health risks for long-duration and ex ploration spaceflight. The evidence reports, which are publicly availa ble, are categorized into five broad categories: (1)
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THE NASA HUMAN RESEARCH ROADMAP The evidence reports reviewed in this National Academies' report are part of a larger roadmap process developed and under implementation by NASA's Human Research Program. The goals of the program are to "provide human health and performance countermeasures, knowledge, technologies, and tools to enable safe, reliable, and productive human space exploration" (NASA, 2014)
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. o RISK OF CA R ARDIOVASC CULAR DISSEASE AND OTHER DEGENNERATIVE TISSUE EF FFECTS FRO OM RADIATION EXPOSSURE As discussed in the evidenc report Risk of Cardiova s n ce k ascular Diseaase and Other Degener rative Tissue Effects from R E Radiation Exp posure (Patel et l al., 2016)
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Additional cross-referencing among these evidence reports might be considered as a way to efficiently cover all of this material. Does the Evidence Report Provide Sufficient Evidence, as Well as Sufficient Risk Context, That the Risk Is of Concern for Long-Term Space Missions?
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Does the Evidence Report Provide Evidence That the Named Gaps Are the Most Critical Presented? The report adequately supports the named gaps as the most critical to improving understanding of and appreciation for the risk of cardiovascular disease and other degenerative tissue effects from radiation exposure.
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) : This gap addresses the need to identify potential synergistic interactions with other spaceflight factors that may alter ionizing radiation−induced degenerative effects/risks and emphasizes the need for the topic of this evidence report to be discussed in other evidence reports, such as those on sleep and on immune function (Crucian et al., 2009; Flynn-Evans et al., 2016)
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Differences and similarities in male versus female responses are also largely absent. Not only are less heterogeneous and more comparable populations needed to generate meaningful risk coefficients, it is "essential that additional data with HZE particles be acquired using relevant model systems and relevant doses to refine the current model of cardiovascular disease risk from space radiation" (NCRP, 2014, p.
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An important long-term goal will be to consider all possible changes in animal validation studies once those are conducted at the extendedduration GCR simulator facility under development at NASA's Space Radiation Laboratory. The accepted relationship of low-LET ionizing radiation exposure with accelerated aging and associated degenerative diseases is discussed in the evidence report.
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and the subsequent commentary it sparked (Cucinotta et al., 2016) highlight the controversy associated with space-relevant ionizing radiation−induced cardiovascular disease.
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Missions to the ISS and any planned establishment of a moon base or manned missions to other planets, including Mars, implies radiation exposure to the crew. A major concern to space agencies is the cancer risk to astronauts caused by high-energy particles, including galactic cosmic rays and solar particle events (SPEs)
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The contribution of each of these steps may vary with tissue types, which gives each tumor its unique characteristics. The evidence report recognizes the multitude of modulating factors, both physical and biological, that can dictate the final tumor outcome from space radiation exposure.
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It provides an up-to-date overview on the state of knowledge in the field of space radiation carcinogenesis. One small point that might be worth clarifying is in the text on the parameters (p.
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However, the previous IOM report highlighted the need to address relevant interactions among risk factors. The current evidence report merely listed many of the potential confounding risk factors without a substantive discussion of the interactions.
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The committee reviewed the evidence report Risk of Acute Radiation Syndromes Due to Solar Particle Events (Carnell et al., 2016)
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Does the Evidence Report Provide Sufficient Evidence, as Well as Sufficient Risk Context, That the Risk Is of Concern for Long-Term Space Missions? Possible acute effects from radiation exposure have been a concern to NASA since the Apollo program, and extensive research on the possibility of acute effects has been under way since the early 1960s, building on military concerns of radiation exposure in the tactical nuclear battlefield.
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While the threat posed by acute radiation syndrome is clear, many critical gaps in knowledge remain to be answered before there is enough evidence-based understanding of the risk of acute radiation exposure to implement successful countermeasures. Several critical gaps exist in the risk assessment for prodromal effects.
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Will those agents being developed for use against high-dose and largely gamma radiation or other low LET sources of injury be appropriate for use in acute radiation syndrome that is caused by high-dose, highly ionizing particles? The storage, use, and potential side effects of promising pharmaceuticals in an operational space environment also need to be considered.
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A more focused effort in each of these evidence reports (Carnell et al., 2016; Huff et al., 2016; Nelson et al., 2016; Patel et al., 2016) to discuss the overlap and crossreference as appropriate is needed.
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For recent studies of acute radiation syndrome, see, for example, Dörr et al., 2014, and MacVittie et al., 2015. For recent reviews relevant to solar particle events see Lee et al., 2012; Baker et al., 2013; and Desai and Giacalone, 2016.
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This evidence book meets the general recommendations of that review. RISK OF ACUTE AND LATE CENTRAL NERVOUS SYSTEM EFFECTS FROM RADIATION EXPOSURE Does the Evidence Report Provide Sufficient Evidence, as Well as Sufficient Risk Context, That the Risk Is of Concern for Long-Term Space Missions?
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Another challenge in assessing additive or synergistic effects is the clear possibility that other stressors (e.g., sleep loss or circadian disruption) could mask smaller effects due to radiation exposure.
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. Because so many factors can affect CNS function acutely and might lead to early cognitive decline in retired astronauts, it might be reasonable to reword this risk as, "Acute and Late CNS Effects from Space Radiation and Other Elements in the Spaceflight Environment." What Is the Overall Readability and Quality?
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Does the Evidence Report Provide Sufficient Evidence, as Well as Sufficient Risk Context, That the Risk Is of Concern for Long-Term Space Missions? The evidence report, which notes that most reports of behavioral health problems are either anecdotal, based on analog samples, or extrapolated from subclinical risks, clearly indicates that the risk is of concern for long-term space missions (e.g., to Mars, which would last approximately 3 years)
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The BMed 2 gap listed in the evidence report refers to the need to "identify and validate measures of behavioral health" (Slack et al., 2016, p.
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The impossibility of real-time communication on a Mars mission could, and probably should, be identified as a specific and important knowledge gap. Consideration should also be given to incorporation in the report of an overview of the current state of knowledge with respect to genetic or epigenetic influences on behavioral health.
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The committee believes the potential seriousness of the psychological and behavioral health risks highlights the need for the evidence book to contain a review and any relevant data, including an analysis of newer instruments and scales for evaluating more sub tle personality differences. Including this information will also point to potential associated research gaps.
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. This risk differs from the others discussed in the evidence reports in that it addresses team performance first; health is a secondary consideration.
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Team Gap 3: We need to identify a set of countermeasures to support team function for all phases of autonomous, long duration and/or distance exploration missions. Team Gap 4: We need to identify psychological measures that can be used to select in dividuals most likely to maintain team function for autonomous, long du ration and/or distance exploration missions.
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helped refine the committee's views. Does the Evidence Report Provide Sufficient Evidence, as Well as Sufficient Risk Context, That the Risk Is of Concern for Long-Term Space Missions?
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Workshop presenters noted the importance of tools such as team dynamics training, which can help improve team functioning even when the initial composition of the team is less than optimal. Team Gap 6 identifies the need to support and enable multiple distributed teams to manage shifting levels of autonomy during longduration and/or long-distance exploration missions.
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This report clearly identifies interactions with the issues discussed in a number of the evidence reports on radiation, sleep, and biomedical risks. Missing is a likely interaction with the evidence report Risk of Inadequate Critical Task Design (Sandor et al., 2013)
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. Has the Evidence Report Addressed Previous Recommendations Made by the IOM in the 2008 Letter Report?
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RISK OF PERFORMANCE DECREMENTS AND ADVERSE HEALTH OUTCOMES RESULTING FROM SLEEP LOSS, CIRCADIAN DESYNCHRONIZATION, AND WORK OVERLOAD The Behavioral Health and Performance element in NASA's Human Research Program aims to further characterize the risk of performance decrements and adverse health outcomes resulting from sleep loss, circadian desynchronization, and work overload, which occur for ground and flight crews both before and during long-distance and exploration spaceflight missions, in preparation for exploration missions beyond low Earth orbit, including to Mars. Ground evidence indicates such risk factors may lead to performance decrements and adverse health outcomes, which could potentially compromise mission objectives.
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space missions. However, by contrast, the evidence report lacks a discussion of the evidence and risk context for how the physiological and behavioral health outcomes resulting from sleep loss, circadian desynchronization, and work overload are of concern for long-duration space missions.
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and gross motor performance, including balance, walking, and other operational outcomes, both of these domains would affect EVAs as well as day-to-day activities • Understanding of the effects of microgravity on central and pe ripheral circadian oscillators, and on sleep homeostasis and sleep quality • Knowledge of the effects of diet and nutrition on circadian rhythms and on sleep, and investigating the timing of food as a countermeasure Does the Evidence Report Address Relevant Interactions Among Risks? The report appropriately addresses many of the relevant interactions with the risks described in the other behavioral health and performance element evidence reports (e.g., Landon et al., 2016; Slack et al., 2016)
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; individual differences in response to sleep loss (both phenotype and genotype studies) ; work overload; and sex differences in response to sleep loss, circadian desynchronization, and work overload.
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. To resolve this issue, weblinks could be added to the evidence reports.
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RISK OF IMPAIRED CONTROL OF SPACECRAFT/ASSOCIATED SYSTEMS AND DECREASED MOBILITY DUE TO VESTIBULAR/SENSORIMOTOR ALTERATIONS ASSOCIATED WITH SPACE FLIGHT NASA's Human Research Program has identified that vestibular and sensorimotor alterations during spaceflight can increase risks related to the control of the spacecraft and other systems, as well as impair mobility following spaceflight. In the evidence report focused on this risk (Bloomberg et al., 2016, p.
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Does the Evidence Report Provide Sufficient Evidence, as Well as Sufficient Risk Context, That the Risk Is of Concern for Long-Term Space Missions? The report very convincingly shows that this risk is a serious concern for long-term space missions.
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Does the Evidence Report Provide Evidence That the Named Gaps Are the Most Critical Presented? Broadly, the evidence report synthesized the literature thoroughly to arrive at the named gaps.
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Finally, Gap SM 2.8 (Develop a sensorimotor countermeasure system integrated with current exercise modalities to mitigate performance decrements during and after space flight) may be overly constrained.
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Many sections of the evidence report do not address potentially important interactions among risks (e.g., interactions with risks of radiation exposure, cardiovascular deconditioning, and orthostatic intolerance, etc.)
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The cited literature is quite extensive, it is generally well synthesized, and the report is well organized. With the caveats raised above, the evidence report provides a comprehensive understanding of the current data.
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In a number of the evidence reports, the focus is on the acute health outcomes that potentially could result from exposures and risks of space travel. Other than radiation carcinogenesis, not enough attention is paid to longer-term outcomes of space health risks (including adverse behavioral health outcomes and cardiovascular events)
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The committee urges NASA to characterize the fidelity and utility of various animal models for the behavioral, sensorimotor, and radiation-related health risks discussed in this report. The committee greatly appreciates the opportunity to review the evidence reports and applauds NASA's commitment to improving the quality of its reports.
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2016. NASA evi dence report: Risk of performance decrements and adverse health outcomes resulting from sleep loss, circadian desynchronization, and work overload.
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2014. Review of NASA's evidence reports on human health risks: 2013 letter report.
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2016. NASA evidence report: Risk of cardiovascular disease and other degenerative tis sue effects from radiation exposure.
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2016. NASA evidence report: Risk of adverse cognitive or behavioral condi tions and psychiatric disorders.
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52 REVIEW OF NASA'S EVIDENCE REPORTS ON HUMAN HEALTH RISKS Zeitlin, C, D
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