American Journal of
EPIDEMIOLOGY
Volume 149
Copyright © 1999 by The Johns Hopkins University
Number 5
School of Hygiene and Public Health
March 1, 1999
Sponsored by the Society for Epidemiologic Research
COMMENTARY
Invited Commentary: What Can We Infer from Author Order in Epidemiology?
David A. Savitz
In a thoughtful Journal essay on molecular epidemiology, Ambrosone and Kadlubar (1) offered a number
of useful recommendations for enhancing communication between laboratory scientists and epidemiologists.
Ironically, one suggestion reveals the authors' grounding in a firmly established tradition of laboratory science: "Authorship should be discussed and agreed
upon at the beginning of a collaboration. One approach
taken by an interdisciplinary research group is an
agreement that when an individual from one group is
first author, a researcher from the other group will be
last author, with a footnote that the project was a collaborative effort with equal input from both groups" (1,
pp. 916-17). In this case, information about the nature
of the collaboration is encrypted in the sequence of
authors, obvious to some readers and certain to be misunderstood by others.
The purpose of publication is communication, and
the reason to reveal the identity and order of authors is
to provide information about both who deserves credit
for the work and who is accountable for its integrity (2,
3). Readers use the author list to form impressions
about the capabilities and achievements of the authors.
Moreover, those who assess individual scholars for
hire, promotion, or receipt of awards and honors rely
heavily on the information in the author list. There
needs to be a match between the message intended by
those who designate the authors and their order and
those who interpret this information (3). At present,
such communication is often unsuccessful.
Criteria for inclusion as an author have been a continuing source of controversy. The most persistent battle is between journal editors, who seek to reduce the
number of authors by setting a more restrictive standard
of authorship based on contributions to the research
activity and the manuscript itself (4, 5), and
researchers, who often are more generous in their definition of an author (6-8). Placing editors and authors in
adversarial positions is counterproductive (3), and pressure from editors for authors to follow rules they dislike
may lead to more dishonesty and less clarity in the
meaning of author designation.
In many scientific efforts, especially epidemiology,
many people contribute, and the magnitude of their
contributions ranges from critical to trivial.
Determining where to draw the line between author and
nonauthor is not a straightforward matter. Much of the
debate concerns "gift authorship," whereby authors are
included on the basis of logistical contributions such as
providing funds or granting access to patients rather
than on intellectual contributions to the research (2).
Journals routinely prohibit including such contributors,
but compliance is limited (8). Conversely, the term
"ghost authorship" has been applied to those who make
a substantial intellectual contribution to the work but
are excluded for some arbitrary reason (2). A movement is developing to encourage or require authors to
directly state their contributions to the research in a
footnote to the article (2, 9-12), which is a useful
experiment to enhance communication between
authors and readers. Nevertheless, with or without footnotes, there will continue to be a list of persons, ordered
in some manner, on the masthead.
Even under the most structured proposals for designation of authorship (13), the authors themselves will
continue to make subjective judgments when drawing
Received for publication September 21, 1998, and accepted for
publication October 23, 1998.
From the Department of Epidemiology, CB #7400, School of
Public Health, University of North Carolina, Chapel Hill, NC 275997400. (Reprint requests to Dr. David A. Savitz at this address).
401
402
Savitz
the line between author and nonauthor, as well as when
designating the order of authors, which is the focus
here. Standardization would enable the reader to accurately interpret author contributions across research
teams, journals, and disciplines, but the requirements
for authorship cannot be structured and enforced to that
degree. A more modest goal for author lists is to enable
the reader to accurately interpret the authors' subjective
views of the relative magnitude of their contributions to
the work. The ambiguity associated with the last author
position is of particular interest, because this position
invites a uniquely subjective, inconsistent, and misinterpreted message about the research activity and product. However, confusion about the second author's
expected contribution and on occasion the penultimate
author's contribution may also occur, with the designation of the position intended to send a message.
The concept of "last authorship" implies that relative
position counts: being the third of three authors is
meant to be different from being the third of four or
more authors. The tendency to use author placement to
designate a "senior author" varies markedly across
realms of biomedical research, and without a more
direct statement by the authors, there is no way to know
with certainty what was meant. The most recent statement regarding "Uniform Requirements for
Manuscripts Submitted to Biomedical Journals" indicates that "the order of authorship should be a joint
decision of the authors. Because the order is assigned in
different ways, its meaning cannot be inferred accurately unless it is stated by the authors" (2, pp. 928-9).
As noted by Bhopal et al., "In some papers the senior
investigator is named last, in others it is the head of the
laboratory or department, and in others it is the person
who contributed least" (14, p. 1046). At the extreme,
the work may be thought of as primarily the intellectual contribution of the last author, with the first author
implementing the study and leading the writing and
other authors playing supporting roles. Not only is the
inference about the last author's contribution prone to
misinterpretation, but the perceived contribution of all
other contributors also shifts depending on the intellectual credit granted to the last author.
In a clinical journal, it was proposed that the last
author's position be used to "indicate the person in
whose laboratory the study was done and who was
peripherally involved with the details of the study, but
who also participated in either the general conception,
supplying the administrative support, or overseeing the
general progression of the study" (15, p. 604).
Implementing this highly refined definition would not
be easy. A counterproposal by the editor of the same
journal may be more feasible: "The first author should
have made major contributions. . . . the following
sequence of authors should represent progressively
lesser contributions" (16, p. 271). Different teams of
researchers "know" the rules as they apply them, yet
there is no consistency since readers "know" different
rules (3). Even in the most recent series of thoughtful
publications on the topic of authorship, author order is
not mentioned (9, 11, 12), or it is mentioned only to
note the lack of a recommended systematic approach to
designating author order (10).
Despite the failure of journal editors to resolve the
meaning of the last author position (4), the goal of clear
communication would be met if authors had reached an
implicit consensus. A small survey of authors of multiauthored papers in a medical journal suggested notably
greater contributions for first authors, with the other
authors, including the last one, not much different from
each another (6). In the late 1980s, Shapiro et al. (7)
conducted a more extensive survey of biomedical
papers with four or more authors and queried first
authors about the contributions of all authors to the
works that were published. While there was substantial
variability in the specific contributions of authors listed
in various positions, the last authors made the second
greatest contributions to the works, following only the
first authors. Last authors were more likely to "provide
resources" than were even first authors; were between
the first and second authors in contributing to the conception, design, analysis, and writing; but were notably
less likely than the first or second authors to contribute
to data collection. The last authors of basic science
papers made greater contributions than the last authors
of clinical research papers.
Thus, some criteria begin to emerge for inferring
what the last author has actually done. These authors
are likely to provide resources and perhaps direct the
laboratory or unit in which the research took place, but
the inference is more likely to be accurate if the work is
in the basic sciences and less accurate in clinical
research. The last author may especially contribute to
the overall concept or direction of the research but is
not likely to have conducted the study. None of these
educated guesses can be made with confidence.
In practice, readers must use yet more subtle clues. If
the last author is prominent, and he or she follows other
less prominent authors, the last author is likely to have
special significance. Name recognition inevitably
comes into consideration, so the reader's familiarity
with the administrative hierarchy of the research group
or overall familiarity with the literature affects the ability to make the correct inference. There is an element of
noblesse oblige associated with having the stature to be
so generous as to place oneself at the end of the list (3).
Rather than downplaying the senior investigators' role,
this sleight of hand actually may exaggerate his or her
Am J Epidemiol Vol. 149, No. 5, 1999
Author Order in Epidemiology
importance. Designation of the "corresponding author"
can help in the interpretation: if reprint requests and
correspondence go to the last author, he or she is more
likely to be serving as the "senior author," which may
be closely related to having sufficient clerical help to
respond to those requests. At its worst, the last authorship position is conferred solely for administrative
authority over the research group, a form of "honorary
authorship" (17) prohibited by journal editors.
In epidemiology, the interpretation is further clouded
by the diversity of the disciplinary backgrounds of the
investigators. Different interpretations are required for
those epidemiologists who have basic science training
versus those who have other backgrounds. The content
of the paper may affect interpretation, with molecular
epidemiology studies possibly requiring a different
interpretation from those studies of a more clinical
nature or those addressing social influences on disease.
Broadly defined, the most direct consequence of
author order aside from professional reputation is the
use of such data in hiring and promotion decisions.
Here, what matters is not what message the authors
intended to convey by their ordering but the inference
that is made. Those epidemiologists based in medical
schools or settings dominated by biomedical scientists
(such as the National Institutes of Health) are more
likely to be presumed to follow a "senior author" tradition than are epidemiologists in schools of public health
or settings such as the Centers for Disease Control and
Prevention. Authors may have learned to respond to the
reward system applied to the setting in which they work
and designate author order as their evaluators will interpret it. The credit assigned to an author in a given position, although rarely quantified formally, is certain to
differ based solely on the presumptions of the assessor.
A simple and easily understood solution is to
sequence the authors in order of their contributions,
without exception, and for readers to be able to safely
assume that this has been done. Rennie et al. argue for
listing the names "according to the relative importance
of their duties: in descending order, starting with the
collaborator who made the most substantive contributions" (3, p. 583). Order of authors must be provided,
and subjectivity in sequencing them remains unavoidable because of the many activities required to instigate
the research and bring the results to publication.
Prescribing a general hierarchy of importance to developing the research program, acquiring funding, developing the idea on which the manuscript is based, implementing the underlying study, planning and conducting
the analysis, and writing the manuscript itself is not a
solution, since weighting of the relative importance of
these contributions varies across studies. The research
enterprise in epidemiology may be so different from the
Am J Epidemiol Vol. 149, No. 5, 1999
403
laboratory model that a different system of assigning
credit may be warranted. Describing individual contributions (3, 7) or formally assigning credit by using
quantitative criteria (13, 18) warrant consideration but
are not yet in widespread use. One step toward clearer
communication would be the ability to correctly interpret an ordered list of authors as a reflection of a consensus about their relative contributions to the reported
research.
ACKNOWLEDGMENTS
The author thanks Drs. Harvey Checkoway, Graham
Colditz, David Eaton, and Muin Khoury for helpful comments on the manuscript.
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