EVIDENCE BOOK OVERVIEW
A.
Evolution of the Evidence Book
The original Evidence Book is a collection of Evidence Reports created from the
information presented verbally and discussed within the 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 Evidence Reports
and for the development of future versions. It is publicly available via the National
Academies Press website.
Per the recommendations of the IOM Review,
the Evidence Report information was made publicly available. The methods used
to disseminate the information were the publication of the content of selected
reports in multiple specialized journals and the publication of a subset of the
reports in a collection, forming a NASA
Special Publication entitled the HRP Evidence Book 2008. The
specialized journal publications containing the Evidence Report information
were revised and reviewed per the specifications of the particular journals in
which they were published.
Since this original publication, the HRP
Elements have continued to update each risk Evidence Report based on results
from ongoing research and technology development (R&TD)
activities. The HRR contains the most
up-to-date Evidence Reports in the above table.
An archived publication entitled Human
Health and Performance Risks of Space Exploration Missions, issued
in 2009, is available for reference. Download a copy by clicking this link.
B.
Spaceflight and Ground-Based Evidence
Each risk Evidence Report contains a narrative discussion
of the risk and its supporting 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 the data 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) 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 type of evidence provided in the reports, authors are
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 with 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 are 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 are 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-controlled, 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 present 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 are also
provided.