Evidence Evidence
Human Research Program Evidence
The NASA Human Research Program (HRP) Evidence is a collection of evidence-based risk reports or cited journal articles for each individual risk contained within the HRP Program Requirements Document (PRD). Thus, this set of reports provides the current record of the state of knowledge from research and operations for each of the defined human health and performance risks for future NASA exploration missions. The evidence reports provide a brief review article containing the evidence related to a specified risk, written at a level appropriate for the scientifically-educated, non-specialist reader. (For more information regarding the overview and evolution of the evidence, see Evidence Book Overview.)
As an adjunct to these HRP-approved Evidence Reports, HRP is experimenting with the use of Wikipedia articles as a repository for evidence. Wikipedia’s accessibility to the international space flight community and researchers in related terrestrial fields creates the opportunity to generate a more timely and comprehensive evidence base. For some of the risks below, there is a link to a corresponding Wikipedia article. The initial Wikipedia articles were populated with a subset of the information in the HRP-approved Evidence Report but subsequent additions included non-HRP sources. Therefore, the Wikipedia article does not necessarily represent the official HRP view of the evidence. Wikipedia also contains a portal page that lists the articles in development and areas in need of improvement. This experiment began in July 2012 and will run through the summer of 2013.
Behavioral Health and Performance
Risk of Adverse Behavioral Conditions and Psychiatric Disorders
Risk of Performance Decrements Due to Inadequate Cooperation, Coordination, Communication, and Psychosocial Adaptation within a Team
Risk of Performance Errors Due to Fatigue Resulting from Sleep Loss, Circadian Desynchronization, Extended Wakefulness, and Work Overload
Exploration Medical Capability
Risk of Unacceptable Health and Mission Outcomes Due to Limitations of In-flight Medical Capabilities
Human Health Countermeasures
Risk Factor of Inadequate Nutrition
Risk of Bone Fracture
Risk of Cardiac Rhythm Problems
Risk of Clinically Relevant Unpredicted Effects of Medication
Risk of Compromised EVA Performance and Crew Health Due to Inadequate EVA Suit Systems
Risk of Crew Adverse Health Event Due to Altered Immune Response
Risk of Decompression Sickness
Risk Of Early Onset Osteoporosis Due To Spaceflight
Risk of Impaired Control of Spacecraft, Associated Systems and Immediate Vehicle Egress Due to Vestibular/Sensorimotor Alterations Associated with Space Flight
Risk of Impaired Performance Due to Reduced Muscle Mass, Strength and Endurance
Risk of Injury from Dynamic Loads
Risk of Intervertebral Disc Damage
Risk of Orthostatic Intolerance During Re-Exposure to Gravity
Risk of Reduced Physical Performance Capabilities Due to Reduced Aerobic Capacity
Risk of Renal Stone Formation
Risk of Spaceflight-Induced Intracranial Hypertension/Vision Alterations
Space Human Factors and Habitability
Risk of Adverse Health Effects Due to Alterations in Host-Microorganism Interactions
Risk of Adverse Health Effects of Exposure to Dust and Volatiles During Exploration of Celestial Bodies
Risk of an Incompatible Vehicle/Habitat Design
Risk of Inadequate Critical Task Design
Risk of Inadequate Design of Human and Automation/Robotic Integration
Risk of Inadequate Human-Computer Interaction
Risk of Performance Decrement and Crew Illness Due to an Inadequate Food System
Risk of Performance Errors Due to Training Deficiencies
Space Radiation
Risk of Acute and Late Central Nervous System Effects from Radiation Exposure
Risk of Acute Radiation Syndromes Due to Solar Particle Events (SPEs)
Risk Of Degenerative Tissue Or Other Health Effects From Radiation Exposure
Risk of Radiation Carcinogenesis

The Human Health and Performance Risks for Space Exploration Missions book, a collection of many of the evidence reports, is available in an electronic .pdf format! Download a copy by clicking this link.



The HRP, within the NASA Human Exploration and Operations Mission Directorate (HEOMD), is a research and technology development (R&TD) program that addresses NASA's needs for human health and performance risk mitigation capabilities in support of space exploration missions. These exploration undertakings include missions to Near Earth Asteroid (NEA), including the Moon, and Mars. Although all of these mission types involve some of the same human health and performance challenges, each also includes specific challenges that depend on the nature of the mission and the mission development schedule. HRP R&TD are focused on the highest-priority risks to crew health and safety, with the goal of ensuring mission success nd maintaining long-term crew health.

The development of HRP content has been formulated around the management architecture of “Evidence to Risk to Gap to Task to Deliverables”. In other words, evidence indicates that a risk exists to the human system, and gaps in our knowledge about the risk or how to mitigate it indicate what tasks need to be carried out in order to produce the deliverables needed to fill these gaps. Three core documents thus describe the HRP: 1) the Program Requirements Document (PRD), 2) the Evidence Book, and 3) the Integrated Research Plan (IRP). These documents are updated regularly and provide relevant information that can be used to manage the program.

The HRP PRD defines, documents, and allocates the high-level requirements to each of the HRP Program Elements: Behavioral Health and Performance, Exploration Medical Capability, Human Health Countermeasures, ISS Medical Projects (as an implementing Element, no risks assigned), Space Human Factors and Habitability, and Space Radiation. These requirements are derived to satisfy the exploration mission requirements of the HEOMD and the Office of the Chief Health and Medical Officer (OCHMO) and are essentially the set of spaceflight human health and performance risks and standards of acceptability for these risks upon which the HRP is focused [NASA Standard (STD) 3001, Space Flight Human System Standard - Volume 1: Crew Health, and Volume 2, Human Factors, Habitability, and Environmental Health, available on the Standards and Technical Assistance Resource Tool (START)]. In addition, NASA/SP-2010-3407, Human Integration Design Handbook (HIDH) was published as a compendium of human space flight history, lessons learned, and design information for a wide variety of disciplines to serve as a companion document to NASA-STD-3001, Volume 2, Human Factors, Habitability, and Environmental Health.

The Evidence Book provides a record of the state of knowledge from research and operations for each risk currently in the PRD. The book consists of an evidence-based report or collection of citations for each individual risk. Each report is essentially a brief review article, written for a scientifically-educated, non-specialist reader.

The IRP documents what implementation activities are necessary to fill the knowledge and mitigation gaps associated with each risk listed in the PRD and supported by the Evidence Book. It also details when those activities will be accomplished, where they will be accomplished (for example, the International Space Station or a ground analog), who will accomplish them (investigators within a specific project or organization within the HRP), and what is being produced (risk uncertainty reduction, candidate health or performance standard, countermeasure strategy, etc.). The Human Research Roadmap is the web-based tool for communicating the IRP content.


The Bioastronautics Roadmap (BR) documents the health and performance risks and areas of concerns of a wide cross-section of the professional space life sciences community, but it does not have the level of detail necessary to prioritize risks across physiological disciplines or to compare strategies for how to manage a given risk across mission operational architectures. In order to identify missing risk details, organize the diverse risk information needed and facilitate mission-focused analysis and communication of risks, the NASA Human Health and Performance Directorate (HHPD) developed the Risk Mitigation Analysis Tool (RMAT). It provides a method to consolidate information such as identified risk and evidence base; the standard level of acceptable risk; likelihood and consequence of risk; current and proposed mitigation capabilities for risk; and potential costs and benefits of mitigation capabilities for risk. Further, all of the information in the RMAT is provided in the context of specific mission architectures, which vary in duration, degree of autonomy (due to distance from Earth), onboard capabilities, etc. In total, this tool permits analysis of risks in a manner based on evidence and provides a platform for comparison within and between risks.

The HRP 2008 PRD risk list, which has no cross-risk prioritization, was generated from an extensive discipline-by-discipline Program Review of risks held in 2006. This review began with the BR risk list, continued with an extensive assessment of medical observations and research findings, and finally led to the identification of a slightly narrowed and more operationally-focused series of risks and risk factors. During this review, teams of discipline experts analyzed the current evidence for each risk and presented their assessments to HRP management. Each HRP element then evaluated the available information from the discipline teams and determined whether the risks were relatively high priority and operationally relevant. For many risks, the data to generate information regarding the likelihood and consequences of a risk were not yet available. Although probabilistic risk methodology was currently being used to provide this information, most of these analyses had not yet been completed; therefore cross-risk prioritization is not yet possible. However, the HRP expects to have this capability in the near future. As more mission experience and space and ground-based evidence become available, new risks may be identified and added to the PRD, while other risks and contributing factors may be taken off the PRD requirements list. The HRP shall thus periodically review the available evidence and revise the lists of risks and contributing factors in the PRD as appropriate.

A. Evolution of the Evidence Book

The original Evidence Book, the 2008 Evidence Book, is a collection of evidence reports created from the information presented verbally and discussed within the NASA HRP in 2006. In April of 2008, the 2008 Evidence Book was reviewed by the members of the Committee on NASA's Research on Human Health Risks, established by the Institute of Medicine (IOM). The resulting thorough Review of NASA's Human Research Program Evidence Books: A Letter Report (2008) provided guidance for both the revision of the current Risk Reports and for the development of future versions. It is publicly available via the National Academies Press website.

As per the recommendations of the IOM Review, risk report information was made publicly available. The method was either to publish the content of selected reports in multiple specialized journals or to publish a subset of the reports in a collection, forming a NASA Special Publication entitled the HRP Evidence Book 2008. The reports revised for presentation in the HRP Evidence Book 2008 incorporate the recommendations from the IOM Review as much as possible. The specialized journal publications containing the evidence report information were revised and reviewed as per the specifications of the particular journals in which they are to be published.

Since this original publication, the HRP elements continue to update each evidence report given results from ongoing research and technology development tasks. The Human Research Roadmap contains the most up-to-date evidence reports in the above table..

B. Spaceflight and Ground-Based Evidence

Each risk report contains a narrative discussion of the risk and its supporting evidence. Every declarative statement concerning the risk is supported by a description of the evidence. All cited publicly-available references are listed at the end of the report. In addition, data that are significant or pivotal are summarized in text, tables, and charts in sufficient detail to allow the reader to critique and draw conclusions. The authors also indicate whether the data are from human, animal, or tissue, cellular, or molecular studies. The reports discuss evidence from both spaceflight (including biomedical research, Medical Requirements Integration Document [MRID] data, and operational performance or clinical observations) and ground (including space analog research and non-space analog biomedical or clinical research). When providing evidence from ground-based studies, authors discuss why these results are likely to be applicable in the space environment, offering any available validation information for the use of these ground-based systems.

C. Categories of Evidence

To help characterize the kind of evidence provided in the reports, authors were encouraged to label evidence according to the "NASA Categories of Evidence." These categories indicate whether data are from two possible types of controlled experiments, are observational, or are expert opinion. As shown below, the NASA categories are compared to a more familiar version of a scale for levels of evidence. The use of a coordinated data categorization system is new to many NASA life scientists, but authors were encouraged to use such a system to help clarify the type of evidence presented and thus provide some additional information about the strength of interpretations derived from those data. They were not required to use the categorization system hierarchically.

Broad "Experimental" Design Type Silagy & Haines Levels of Evidence* (for comparison only) NASA Categories of Evidence
Controlled Ia. Meta-analysis of randomized trials I. At least one randomized, controlled trial
Ib. At least one randomized trial
IIa. At least one controlled study without randomization II. At least one controlled study without randomization, including cohort, case-control, or subject operating as own control
IIb. At least one other type quasi-experimental study
Observational III. Non-experimental descriptive studies, e.g. comparative correlation, or case studies III. Non-experimental observations or comparative, correlation, and case or case-series studies
Opinion IV. Expert committee reports or opinions or clinical experiences of respected authorities IV. Expert committee reports or opinions of respected authorities based on clinical experiences bench research, or "first principles"
*Source: Silagy C, Haines A. Evidence Based Practice in Primary Care, 2nd ed., London: BMJ Books, 2001.
D. Computer-Based Simulation Information

Mathematical modeling and computer simulation provide another type of information distinct from experimental evidence, observation, and expert opinion that can support decision making, including the identification of risks. In the evidence reports, authors presented the results of simulations, the types of models used, and the reasoning that supports the acceptance of the modeling and simulation results as valid and appropriate in the situation of interest. Appropriate references to papers or reports describing the types of verification to which models were subjected and the validation methods used were also provided.

E. Risk in Context of Exploration Mission Operational Scenarios

The HRP uses a research rating as a tool to communicate to Agency management the seriousness of a risk to crew health and performance when applied to the mission architecture and/or mission characteristics defined for each DRM. The research ratings serve as one of several inputs to determine the priority of each human risk, helping HRP Management make program decisions and allocate program resources.

Each research rating is derived by comparing the current state of knowledge about a risk, whether existing standards are defined and met, and the degree to which research will improve the current risk posture with respect to crew health and performance during long duration missions. Each human risk has one of four research ratings identified for each of the four DRMs, driven by its applicability to the DRM mission architecture and/or mission characteristics. HRP uses the following four DRMs to bound its exploration mission assumptions: (1) 12-month mission on ISS (ISS-12); (2) Lunar (Outpost) mission; (3) Deep Space Journey mission; and (4) Planetary mission [Appendix B of this document for further definition and assumptions for each DRM]. The four possible research ratings are: Controlled, Partially Controlled, Uncontrolled, and Insufficient Data. These ratings are described below.

Rating: Controlled (C) - Green

A risk is deemed to have a research rating of Controlled if based on available evidence, the projected mission architecture (with assumptions on DRM-specific vehicle design and operations constraints) meet existing standards for maintaining crew health and performance and countermeasures exist to control the risk. Continued research or technology development will improve capabilities, provide additional trade space to support meeting crew health standards or ensure that vital Agency core competencies are accessible.

The scientific, operational and clinical evidence for the risk and current available mitigations and countermeasure capabilities demonstrate that the Agency can meet the existing standards for maintaining crew health and performance during all phases of the mission. Research has provided at least one solution capability to address the risk. Additional research or technology development could further reduce risk by enhancing understanding and offering different options to increase engineering and operational efficiencies, make the best use of unique assets such as ISS in optimizing risk posture, and maintain vital Agency core competencies.

Rating: Partially Controlled (P) - Yellow

A risk is deemed to have a research rating of Partially Controlled if based on available evidence, the projected mission architecture (with assumptions on DRM-specific vehicle design and operations constraints) likely provides the capability to meet existing standards for maintaining crew health and performance but the risk is not fully controlled. The remaining level of uncertainty would likely lead the Agency to accept a higher than expected level of risk to crew health and performance during some phases of the mission. Continued research or technology development is expected to improve capabilities or substantiate crew health standards.

The scientific, operational and clinical evidence for the risk and current available mitigation and countermeasure capabilities demonstrate that the Agency can likely meet existing standards for maintaining crew health and performance during some, but not all phases of the mission. Additional research or technology development may further improve the risk research rating to achieve a Controlled rating.

Rating: Uncontrolled (U) - Red

A risk is deemed to have a research rating of Uncontrolled if based on available evidence, the projected mission architecture (with assumptions on DRM-specific vehicle design and operations constraints) will not provide the capabilities required to meet existing standards for maintaining crew health and performance during all phases of the mission. Therefore, research is required to acquire necessary information and develop necessary capabilities and countermeasures to arrive at an acceptable risk posture.

The scientific, operational and clinical evidence for the risk and current available mitigations and countermeasure capabilities do not adequately demonstrate the capability of the Agency to meet existing standards to protect and/or maintain crew health and performance during all phases of the mission. The inadequacy and uncertainty in the risk mitigation capabilities and countermeasures will require additional data and/or mitigation strategies to be developed through the research performed by the HRP.

Rating: Insufficient Data (I) - Gray

A risk is deemed to have a research rating of Insufficient Data if there is not enough available evidence to assess whether the projected mission architecture (with assumptions on DRM-specific vehicle design and operations constraints) can meet existing standards for crew health and performance or if such standards need to be developed. Research is required to further understand and define the risk to the point that its research rating can be determined by HRP to controlled, partially controlled or uncontrolled. This rating is primarily for new risks before a research rating can be determined.

The scientific, operational and clinical evidence for the risk and current mitigation and countermeasures capabilities are inadequate to allow the assessment of the ability of the mission architecture and/or mission characteristics to support crew health and performance standards. Additional research is expected to support determination of a new research rating.

The research rating of a risk alone is not sufficient to determine its priority within the HRP research portfolio. Priority is dependent on other factors such as limited availability of certain necessary resources (as the ISS, ground analogs, etc.), program funding, exceptionally long lead times (e.g., needed to improve understanding and mitigation of radiation risks), or the amount of risk reduction that can be obtained with a specific set of resources. The level of activity (or budget) and timing of research investments reflect the final prioritization of the risks.

Implementation of the HRP Research Rating and applicability to the HRP owned risks are contained in the Human Research Program Requirements Document (HRP-47052)