J Appl Physiol 112: 1429 –1430, 2012;
doi:10.1152/japplphysiol.00271.2012.
Editorial
Effects of aging, and other bad behaviors
Peter D. Wagner
Department of Medicine, University of California, San Diego, La Jolla, California
EVERY YEAR, THOMSON-REUTERS
Address for reprint requests and other correspondence: P. D. Wagner, Dept.
of Medicine, Univ. of California, San Diego, La Jolla, CA (e-mail: pdwagner
@ucsd.edu).
http://www.jappl.org
Fig. 1. Frequency distribution by decile of total lifetime citations to all 747
articles (top) and 512 research papers (bottom) published in the Journal of
Applied Physiology in 2007. Each decile represents, and averages citations to,
⬃75 articles (top) and 512 articles (bottom).
point that cannot be overemphasized: To judge individual
authors for academic promotion or research funding by the
average impact factor of the journal carrying their papers is
ludicrous. Was the author in question in the first, the 10th, or
another decile of citations? Surely that is important if impact
factor is to be used as the pass/fail criterion in their judgment.
So once again, we echo the conclusions of the International
Respiratory Journal Editors Roundtable (3) and plead with
those charged with evaluating faculty for promotion or research funding to do away with journal impact factors in
making these critical, life-changing decisions. The impact
factor is just one of several parameters of a journal’s influence,
with the different parameters each leading to different journal
ranking (6). But more importantly for the candidate up for
promotion or research funding, citation variance among papers
within a journal is huge. By all means check the individual’s
personal citation record [such as the H-index (2, 5)], but do not
use the journal impact factor to evaluate the candidate when it
is the average of a citation distribution likely as uneven as
shown in Fig. 1.
DISCLOSURES
No conflicts of interest, financial or otherwise, are declared by the author.
8750-7587/12 Copyright © 2012 the American Physiological Society
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publishes journal impact factors,
which equal the number of citations in a given calendar year to
papers published in a journal the prior 2 yr divided by that
number of papers. The term “papers” includes anything ThomsonReuters considers citable. They also provide several additional
statistical citation parameters, and each tells a different story.
In the July 2011 issue of the Journal of Applied Physiology,
this problem was addressed (6), and it was shown that where a
journal ranked among its peers depended on which citation
parameter you chose. This is not the only reason why the
standard impact factor should not be the sole determinant of
individual author evaluation or even of journal standing.
Within-journal variance in citation numbers across the spectrum of published articles is a further limitation to use of the
impact factor, and that is the subject of this editorial. In this
issue of the Journal of Applied Physiology, an analysis of one
cause of within-journal citation variance is presented by Araujo
et al. (1). This is the “aging effect.” With the impact factor
being a number based on average citations to papers published
over 12 calendar months, the authors showed that those papers
published early in the calendar year receive more citations than
those published later in the year. Linear regression of their data
(1) shows the decrease in citations is linear month by month
from a high of 6.7 in January to a low of 4.8 in December. The
reason given is that the longer a paper has been in print, the
more likely it is to have garnered citations, all other factors
equal. From this decline one can calculate that the relative
dispersion (SD/mean) of the aging effect is 0.13.
If one now examines all of the 747 articles (512 research
articles, plus 235 editorials, reviews, point:counterpoint debates, viewpoints, and letters) published in the Journal of
Applied Physiology in 2007 [one of the years covered by the
analysis of Araujo et al. (1)], the frequency distribution of
citations to each paper is astonishing, as shown in Fig. 1. In
Fig. 1, top, all 747 articles were first ordered, left to right, from
least to most citations lifetime since appearing and then divided
into deciles (i.e., of ⬃75 articles each). The least-cited 75 (first
decile, leftmost bar) were not cited at all. The most-cited 75
(10th decile, rightmost bar) were cited an average of 38.6 times
in all. The relative dispersion of the distribution in Fig. 1 comes
to 1.14. In Fig. 1, bottom, the same relationship is shown for
just the 512 research papers, and whereas the pattern is clearly
similar, as expected, the relative dispersion is a little less, at
0.84. Therefore, although the age effect is significant, the
majority of the variance in citations to different papers in the
journal is not due to this but most likely to inherent interest in
the fields of the highly cited papers and those papers’ content.
This analysis is presented to make a single point— one that
has previously been made well by my predecessor, Jerry
Dempsey, and his colleagues (3) among others (4)— but a
Editorial
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REFERENCES
1. Araujo CGS, Oliveira BRR, Brito LVO, Matta TT, Viana B, Souza CP,
Guerreiro RC, Slama FA, Portugal EMM. Two-year citations of JAPPL
original articles: evidence of a relative age effect. J Appl Physiol; doi:
10.1152/japplphysiol.01491.2011.
2. Araujo CGS, Sardinha A. H-index of the citing articles: a contribution to
the evaluation of scientific production of experienced researchers. Rev Bras
Med Esporte 17: 358 –362, 2011.
3. Dempsey JA. Impact factor and its role in academic promotion: A statement adopted by the International Respiratory Journal Editors Roundtable.
J Appl Physiol 107: 1005, 2009.
4. Fersht A. The most influential journals: impact factor and Eigenfactor.
Proc Natl Acad Sci USA 106: 6883–6884, 2009.
5. Hirsch JE. An index to quantify an individual’s scientific research output.
Proc Natl Acad Sci USA 102: 16569 –16572, 2005.
6. Wagner PD. What’s in a number? J Appl Physiol 111: 951–953,
2011.
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