American Journal of Epidemiology
© The Author 2013. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of
Public Health. All rights reserved. For permissions, please e-mail: [email protected].
Vol. 177, No. 7
DOI: 10.1093/aje/kwt027
Advance Access publication:
March 10, 2013
Epidemiology in History
“If It Isn’t Ultimately Aimed at Policy, It’s Not Worth Doing”
Interview of George W. Comstock by Alfredo Morabia
Alfredo Morabia*
* Correspondence to Dr. Alfredo Morabia, Center for the Biology of Natural Systems, Queens College, City University of New York,
65-30 Kissena Blvd., Flushing, NY 11367 (e-mail: [email protected]).
Initially submitted January 30, 2013; accepted for publication February 5, 2013.
George W. Comstock (1915–2007), MD, MPH, DrPH, was lecturer and then professor of epidemiology at the
Johns Hopkins University School of Hygiene and Public Health from 1956 to 2007 and served as editor-in-chief
of the American Journal of Epidemiology from 1979 to 1988. This interview of George W. Comstock took place
in Hagerstown, Maryland, in the spring of 1990. The selection of questions and answers published here represent approximately 10% of the whole interview, which had been reviewed and hand-corrected by Dr. Comstock.
He first describes how epidemiology was taught at Hopkins in the 1950s and 1960s. He then distinguishes “epidemiology per se” from a “practical epidemiology” that works closely with local health departments, and he
finally expresses his wish that in the future, epidemiology would become more widely involved in policy and
accepted by policy makers.
history; interview; policy; teaching
In this first publication of the new section “Epidemiology in History,” I pay a tribute to George W. Comstock,
with whom I had the privilege to work (1, 2). George
passed away in 2007. He was 92 years old. His exit was
suffered as a great loss by the scientific community at
large, with obituaries appearing in The Washington Post
(3), The New York Times (4), Lancet (5), American Review
of Respiratory and Critical Care Medicine (6), and Revista
de Saúde Publica (Brazil) (7). The October 1, 2008, issue
of the American Journal of Epidemiology was entirely dedicated to Comstock, with personal remembrances (8–11)
and discussion of his contributions to the Washington
County Training Center (12) and the fields of tuberculosis
research (13), noninvasive imaging and hypertension (14),
respiratory disease epidemiology (15), and the epidemiologic use of biological samples (16). The articles by Comstock that were republished in that memorial issue are still
great readings and examples of careful studies at a time
when constraints on article length were not what they are
today and articles provided a thorough review and discussion of the literature.
It is fortunate that in 2003, Dale Sandler had a videotaped conversation with Comstock for “Voices” in the
journal Epidemiology (17). A snippet of the video is viewable online (18). Comstock was already 88 years old then,
but the video nicely captures his unforgettable voice and the
gentle way in which he made authoritative statements. There
also exists a short movie about George Comstock (19).
I happen to have interviewed George in 1990. The cover
letter of his hand-edited copy of the 55-page interview is
reproduced in this article. The interview was transcribed
verbatim and published without alteration except for the
inclusion of a few edits handwritten by Comstock on the
paper copy. However, I selected questions that were different from those published by Dale Sandler in her conversation with Dr. Comstock (17). The first set deals with his
reminiscence of the way epidemiology was taught when he
was a student. Comstock mentions 2 exercises that have
been used over very long periods of time in the Department
of Epidemiology. The first was the charity luncheon
problem, which, according to Comstock, “has been used
with practically no break in Epi 1 since 1955.” The exercise
is “Principles of epidemiology: problem 1: An outbreak of
acute sore throats following a charity luncheon” from the
Department of Epidemiology, The Johns Hopkins University Bloomberg School of Public Health, 2006. The
595
Am J Epidemiol. 2013;177(7):595–600
596 Morabia et al.
same mission. Looking at the world through their lenses
for a moment is terribly important to perceive the historical
forces that shaped the epidemiology we practice today.
TEACHING IN THE 1950s AND 1960s
Photo of George, Margaret, and Gordon Comstock taken during
World War II, most likely in 1944, while Dr Comstock was serving as
Medical Officer in an Escort Destroyer Division.
exercise is based on a paper by Farber and Korff (20).
The second exercise mentioned by Dr. Comstock is
“Epidemiology 2A: exercise 4: methods of longitudinal
study” from the Department of Epidemiology, The Johns
Hopkins University School of Hygiene and Public Health,
1986–1987. It analyzes the longevity of members the
Radiological Society of North America and the American
Academy of Ophthalmology and Otolaryngology and
is based on 4 papers by Seltzer, Sartwell, and Matanoski
(21–24).
In a second set of questions, Comstock contrasts what he
calls “epidemiology per se,” which has no direct implications for the community, with “practical epidemiology”
that works closely with local health departments. In the last
set of questions, Comstock expresses his wish that in the
future, epidemiology would become more widely involved
in policy and accepted by policy makers. Comstock spoke
plainly and was not shy about defending ideas, no matter
iconoclastic they sounded. For example, when asked
whether the concept of interaction was taught at Hopkins at
the time of his doctorate of public health in the 1950s, he
answered, “I’m sure we didn’t worry about that as such. Of
course, you probably know I still don’t.”
This 23-year-old conversation with Comstock is a historical document that reflects the thinking of a classic epidemiologist who felt his role was not only to identify causes
of diseases but also to apply this knowledge to improving
people’s health. The generation of epidemiologists to
whom Comstock belongs was driven more or less by this
Question: Who was teaching Epi 1 and Epi 2 at that
time? [This question came while Comstock was describing
the learning environment of the 1950s when he completed
his doctorate of public health at The Johns Hopkins University School of Hygiene and Public Health.]
Answer: Sartwell was in charge of both of those
courses, but what we now call Epi 2 was called the joint
course. And that was joint between both biostatistics and
epidemiology. Dr. Merrell was the primary one for biostatistics. We spent a lot of time playing with marbles and
those calculators and log tables. In fact, my earliest memories of D.A. Henderson is when he took that course he was
always the last one out of class for that day, and he spent
hours playing with these marbles, reproducing epidemics
and seeing how things change then. I don’t remember
another student than him. I remember his interest in infectious disease models even then. That took up about 3
weeks of the 8-week course in advanced epidemiology.
[Philip E. Sartwell (1908–1999), MD, MPH, was a professor of epidemiology at the Johns Hopkins University
School of Hygiene and Public Health from 1947 to 1973
and chair of the Department of Epidemiology from 1954 to
1970 (25). Margaret Merrell (1900–1995), ScD, was in the
Department of Biostatistics of the Johns Hopkins University School of Hygiene and Public Health from 1925 to
1959. She was its acting chair in 1957–1958 (Karen Kruse
Thomas, personal communication, January 25, 2013).
Donald Ainslie (“D.A.”) Henderson, MD, MPH, is an epidemiologist, who, among many other accomplishments,
headed the international effort during the 1960s to eradicate
smallpox.]
Q: By this time did you talk of confounding?
A: I’m a bad one to ask. I’ve never worried too much
about what you call labels. I think I worry about what confounding is. Even now I don’t tend to use that word very
often. We adjusted for factors. I can’t remember if we
called them confounders or not.
Q: Was there the idea that the factors you adjusted for
had to be related to the cause and to the outcome?
A: That was recognized early on. We did much more
stratification than we do now. Multiple regression still was
not a common procedure. I can’t remember when they did
introduce it. Out of the ‘60s maybe, early ‘60s. That’s
about when I became exposed to it.
Q: What would you say characterized the way Sartwell
taught epidemiology at that time?
A: Not all that different from the way it is taught now.
We had the lectures and the exercises, and those were
along the same lines as they are now. In fact, I’ve told you
one of those is essentially unchanged from those days.
Actually, the radiologist exercise we used in Epi 2 was
developed back in those days. I think we’ve had a few
more lectures on the epidemiology of specific diseases than
we do now. We didn’t get very much into adjustment. They
Am J Epidemiol. 2013;177(7):595–600
Interview of George W. Comstock 597
Cover letter of Dr. Comstock’s hand-edited copy of the 55-page interview.
were not exposed to life tables. That way students picked
up a lot of things that we used to teach in Epi 2 and which
I don’t think are grasped by many students of Epi 1
because they are gone over so quickly. They don’t seem to
recognize it when they come to it in Epi 2. And Sartwell
had considerable difficulties with students during the late
‘60s when there were student rebellions. Because he was a
quiet spoken, he was not a dramatic person and the students
gave him a rough time. So was Frost from what I’ve heard.
Frost was an even worse lecturer. I remember Carroll
Palmer telling that he was sitting back there with the students and they would be grumbling, and he would say,
“Alright, just listen to what he’s saying not how he’s
saying it.” Dr. Gordis’s major improvement over the other
heads of department is that he was a much more exciting
lecturer. The content was no better, no worse than it ever
was. I think the content has always been very good, but the
presentation has changed dramatically. [Wade Hampton
Frost (1880–1938), MD, was an epidemiologist, first chair
of the Department of Epidemiology at the Johns Hopkins
University School of Hygiene and Public Health from 1919
to 1938, and the first US professor of epidemiology in
1921 (26). Carroll Edwards Palmer (1903–1972), MD,
Am J Epidemiol. 2013;177(7):595–600
PhD, spent the major part of his career in the US Public
Health Service as Director of Research for the Child
Hygiene Bureau and was, from 1949 to 1955, director of
the Tuberculosis Research Office of the World Health
Organization (27). Earlier in the interview, Comstock said
that Palmer was his mentor and greatest influence on his
career. Leon Gordis, MD, DrPH, is an epidemiologist,
chair of the Department of Epidemiology at the Johns
Hopkins University School of Hygiene and Public Health
from 1974 to 1993, and author of the textbook Epidemiology (28).]
Q: So the criticism by the students in the ‘60s was on
the form, not on the content?
A: True. That’s my feeling. They just didn’t feel excited
by the way in which Dr. Sartwell said it. I still have some
of his tapes. What he says is every bit as good, he just
didn’t say it nearly as well.
EPIDEMIOLOGY PER SE
Q: Has there been a shift from an epidemiology linked
to public health to an epidemiology that is relatively
598 Morabia et al.
independent from public health and very close to medical
practice and hospitals?
A: And to epidemiology per se.
Q: What is epidemiology per se?
A: Well, many of our research projects, just take the one
I have up there in Hagerstown on the Serum Bank. That’s
not really linked to anything specific to Washington
County. That study, on the precursors of cancer, I would
call that epidemiology per se. If I were interested in things
locally I’d be studying, oh, the extent to which cervical
cytology is applied and is effective locally and if our blood
pressure screening and cholesterol screening were effective
locally. It is hard to get money to do that sort of thing,
because it isn’t generalizable. [Comstock is referring to the
Training Center for Public Health Research in Washington
County, Maryland (29).]
Q: How did this change from practical epidemiology to
epidemiology per se influence the way it is taught or it is
practiced?
A: We teach it as epidemiology per se. Did you get
exposed to anything about how you’d solve the problems
of the local health department? I don’t think you did, not in
this school. There is no money in it. The local and state
health departments almost without exception don’t put any
money into research. In fact, many of them would consider
that they should not be interested in research. I think this is
wrong, and I see that as one of the major differences of
being in epidemiology in this country and in Great Britain.
A sizeable chunk of their money comes from the health services end, and so is focused on how well do things work,
or where are the problems locally. Of course they get their
Medical Research Council money (which is the equivalent
to the NIH) more or less for pure epidemiology or otherwise epidemiology per se.
Q: Did the turn to epidemiology per se improve the
discipline?
A: The discipline I hope has improved. Certainly its
tools and techniques have improved. I think the immediate
availability to what we consider local public health has
diminished obviously. All the things we deal with have
something to do with people’s health and therefore deal
directly or indirectly with public health.
Q: Can you be more explicit on which aspect this discipline has improved over the last 15 years?
A: Not in many ways in my opinion. I think a major
improvement has come with the multiple regression. I
would include the Cox procedure there. Of course, we’ve
got a lot of laboratory things we can do, a lot of laboratory
tests, but those really don’t change. We deal with viruses
now where we used to have to deal almost entirely with
bacteria and that sort of thing. I think that, sitting here this
minute, I would say that that’s almost the only really
important change that has occurred: the ability to handle a
whole bunch of possibly confounding factors at once
instead of teasing them out one at a time by direct adjustment or analysis of variance. A lot of those things are
really unchanged. The advantages are kind of trivial and
there is also a disadvantage in that they are not always
wisely used, in my opinion. People don’t stop to think of
the consequences of forcing their data to fit a preconceived
line. Rarely do you look to see if the data does fit that line.
And we’re getting where we don’t communicate very well.
We communicate in kappas and betas and funny ratios like
the body mass index to name a few, although they don’t
make sense to the average person on the street.
Q: Let’s take an example. Let’s say that you had to
design a case-control study in 1965 or today. In which
sense would it be different?
A: Not at all, except the analysis. We would probably
use logistic regression.
Q: What about the enormous production of theoretical
literature in epidemiology on confounding, interaction and
the different measures of incidence?
A: I think most of that stuff is for the birds. You stop
and think. What could go wrong? How should the cases
and controls be treated? Did I really select them to represent what I think they should select? You can stop and
break this thing up into lots of little pieces and give them
all names, but I’m not sure that really helps. Because if you
give them all names, there may be something come up that
you don’t know the name for or you don’t think of it. You
have to think about the whole individual thing. All this
business about whether a control is alive at the same time
the case was diagnosed and whether that makes a case,
they can’t even remember the names of. You know they’re
all so nearly the same, and they lead you to the same conclusions. I think it is still basically a matter of sitting down
and finding something that you think is going to work from
the sense that you’ve chosen your people correctly and
you’ve handled them correctly. The big advantage is that if
we do want to adjust for a lot of other variables, we can do
it very beautifully with all of our regressions. The trouble
of that is we sometimes just plug it in and do it without
stopping to think. Fortunately the regression models are
pretty robust. Of course, one of my pets is that I think
people should all be looking at things categorically instead
of continuously. Again, the world thinks in categories.
Who across the street cares whether the risk of heart
disease is increased so much a millimeter of blood pressure? But how do we analyze it? By millimeter most of the
time. And that’s assuming we’ve got a straight line or
slightly curved line. But sometimes when you do it by category you discover that it doesn’t go that way. It’s a broken
line, it’s a jagged curve. You’d never find that out if you
don’t also look at your data by categories. Why do they do
it continuous? I think they do it because you get better significance that way. But that’s statistical significance, not
better meaningful significant data.
FUTURE OF EPIDEMIOLOGY
Q: You’ve already pointed out some aspects that could
improve the quality of epidemiology. How do you see the
future of epidemiology? How would you like it to be?
A: I guess I would like to see all things that I’ve mentioned take place. Well, I do think we need to be more
widely accepted in policy areas then we are, and I think if
we’re going to do that, we’ve got to talk the language of
the policy makers. Which I don’t think we’ve learned very
well. It’s a big problem, of course, in that the attitude of
Am J Epidemiol. 2013;177(7):595–600
Interview of George W. Comstock 599
the courts towards causation is entirely different than ours.
I’m not quite sure I know how you solve that. It seems to
me it takes not only a change in epidemiology for practical
and more understandable terms, but it requires the courts to
get away from their very rigid and frequently irrational
decisions as to cause. The world isn’t black and white all
over, although it pretends it is. How they put their house in
order I don’t know. I think, obviously, there’s got to be
some judicial system that recognizes that you can’t just say
that this guy got leukemia because of radiation exposure
out there in Utah and this guy didn’t. You’ve got to
develop some other way of saying, OK, the probabilities
are such and reimburse or reward or punish people according to probabilities, not just either you do or you don’t. I
don’t know how you work it. That’s beyond me. I haven’t
thought much about it either. From our point of view I
think we’ve got to learn to present our findings in ordinary
English, in your case, ordinary French or German, or whatever it may be where you are. In other words, in nontechnical terms. It’s nice to talk jargon, once you know
what it means, I know what it means, but does the guy on
the street know what it means? Well, often he doesn’t. And
if he doesn’t know what it means he certainly isn’t going
to use it.
Q: If I understand you well, you think that epidemiology
that used to be applied on local public health should now
become useful for state and national public health.
A: Yes.
Q: But this national state level impact hasn’t been yet
reached by epidemiologists?
A: No. Part of it is our problem by not communicating
as quickly. Part of it is their problem, by not realizing,
because they don’t know enough about epidemiology. And
somehow or other we’ve not gotten over to the health
administrators and the policy makers of this country adequately the fact that this is in many ways rather soft
science. You can’t expect to do one study and get a definitive answer forever. You’ve got to look at the range of
studies. Well, estrogens and breast cancer for instance. You
can look at anyone study and come to almost any conclusion you can think of from here to here. If you look at them
all, you come down pretty close to the middle. And, well, I
was very aware of that. My father was metal engineer. He
could never understand why I had so much trouble telling
him something definite. You know, if you pull this piece of
metal apart and it broke and you did something to it and
tested its strength, you know that was the same today,
tomorrow and if you did it in Germany or South Africa,
you got the same reading. He could never understand biologic variability. I think that’s true of a lot of other people.
But on the other hand, I think epidemiology is the basic
science for policies, far more than statistics, although statistics is important too. Statistics pretty much just deals only
with chance. But our whole basic education is such that
people expect that one cause is going to cause an effect in
all populations and that an association is an effect. Because
if they walk out in front of a truck there’s an association
between doing that and a severe injury, and there is also a
very direct cause and effect. And they think everything else
is that way. Now to what extent that’s our job to see that
Am J Epidemiol. 2013;177(7):595–600
the public understands—I don’t know quite how we’d do
that. Except that if in our reporting of these things we fairly
report the other findings and fairly judge what they overall
mean, other than just saying what this particular study
means. Particularly when we go on TV or talk to the newspaper reports, because there if you listen to those guys or
read what they say it’s always as if this study is to be the
“all and end all” for all research on this topic. Never hesitate to be humble enough to recognize you are just one of
many. How do we teach our students to try to give the
press a balanced view rather than just reporting on what
they’re asked on their study? The press asks about it as if
were the final answer. It’s so awfully easy to get seduced
into talking as if it were the final answer. You must have
been interviewed by the press occasionally. Yes, you have.
You know, it’s awfully easy to talk about your own study
as if it were the study, and not just part of the whole
picture. I’ve fallen into the trap all the time, but I try not to.
Q: Do you think there is a conscience among epidemiologists that the ultimate goal should be to influence policy?
A: Yes. Directly or indirectly. It may be that the study
you’ve done has directly, maybe indirectly helped getting
at a cause. Once you’ve established with reasonable certainty that there is a cause and effect, presumably one
hopes to have some effect on some policy somewhere.
You’re not just doing it for the fun of it. Yes. I think that if
it isn’t ultimately aimed at policy, it’s not worth doing.
ACKNOWLEDGMENTS
Author affiliations: Center for the Biology of Natural
Systems, Queens College, City University of New York,
Flushing, New York (Alfredo Morabia); and Department of
Epidemiology, Mailman School of Public Health, Columbia University, New York, New York (Alfredo Morabia).
This work was supported by the National Library of
Medicine grant 1G13LM010884-01A1.
Conflict of interest: none declared.
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