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
EVIDENCE BOOK OVERVIEW
I. BACKGROUND AND DOCUMENTS
The HRP, within the NASA Human Exploration and Operations Mission Directorate (HEOMD),
is a directed and applied research program that addresses NASA's needs for human
health and performance risk mitigation strategies 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 research and technology development are focused on
the highest-priority risks to crew health and safety, with the goal of ensuring
mission success and 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:
Program Requirements Document (PRD),
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 Project (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)
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 Space Life Sciences Directorate (SLSD) 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 strategies for risk; and potential costs and benefits of mitigation
strategies 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
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.
III. EVIDENCE BOOK
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
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
are being 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..
Note that the evidence for two risks, Risk of Reduced Physical Performance Capabilities
due to Reduced Aerobic Capacity and Risk of Unnecessary Operational Limitations due to
Inaccurate Assessment of Cardiovascular Performance, has been provided in a single evidence
report with the overall heading, Risk of Cardiovascular Effects on Performance and Operational
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
||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
||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
||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
In each evidence-based risk report, the qualitative likelihood and physiological consequences of a risk
were presented within the context of a relevant space exploration mission or scenario, such as a short
or long mission to the moon or a mission to Mars, and risk factors were discussed. If a risk was due to
the possibility of exceeding a current physiological standard during a certain mission scenario, that
fact was stated. If the standard existed but was incompatible with the evidence, then the standard was
restated in appropriate terms. Alternatively, if a physiological limit was needed but not available,
a measure or level beyond which risk was present could be proposed. In any case, a clear rationale for
the use of standards or limits in the discussion of likelihood or consequences of a risk during a particular
mission scenario was given.