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IN DEFENSE OF SMOKERS © 1999, Lauren A. Colby. Version 2.3 |
Chapter 8: Smoking Myths and the Role of Detection Bias |
Chapter 8: Smoking Myths and the Role of Detection Bias
Kephart insists, however, that it is normally impossible to
tell, from autopsy, whether the deceased was or was not a
smoker. Upon resection, the lungs are always clear, unless the
deceased lived in a large city where there was significant
industrial pollution. In that event, carbon deposits may be
found, but these are unrelated to smoking. So the "brown lungs"
myth is exactly that: a myth.
Recently, I posed a question to Ed Uthman, M.D., a pathologist
practicing in Dallas, TX. The question was whether a surgeon,
at autopsy, could determine from an examination of the
deceased's lungs, whether the deceased was or was not a smoker.
Here is Dr. Uthman's response:
I don't think one can tell if the deceased were a tobacco smoker
or not by the appearance of the lungs. The absence of any black
pigment suggests that the person was either a nonsmoker or a
very light smoker. Heavy black pigmentation suggests that the
person was either a heavy smoker, or lived in a city with heavy
particulate air pollution, or was a coal miner, or some
combination of the three.
The black pigment in question is elemental carbon, which most
investigators believe to be inert in its effects on the lungs
(although in the extremely heavy doses that coal miners used to
get, it may have had a partial role in coal-workers' lung
disease).
When I point these things out to anti-smokers, they frequently
say, "But I've seen photographs of smoker's lungs that were
shown to me in grade school, and they looked simply horrible."
I've seen these photographs also, but they are phonies. A
popular Internet web site features side by side photographs of
two lungs. One is labeled "Smoker's lung - dead at 50". The
other is labeled "Non-smokers's lungs, alive at 70". The
problem is simply that the photograph of the smoker's lung is a
photograph of a lung ravaged by lung cancer; it is not a
photograph of the lung of some smoker who died from some other
disease. Therefore, even if the cancerous lung is from somebody
who smoked, and the "healthy" lung is from somebody who did not,
the photographs prove nothing except that cancerous lungs look
different from non-cancerous lungs.
Of course, both photographs are photographs of dead people's
lungs, because it's not possible to take a photograph of the
lung of a living person. Also, rather obviously, the
photographs show the outside surface of the lungs. The outside
surfaces of lungs are not exposed to either air or smoke;
therefore, it would be impossible for smoke to stain those
surfaces.
Another myth, propagated by the anti-smoking crowd, is the
notion that lung cancer was a rare disease in this country until
some time in the 1930's, when it began to raise its ugly head as
the result of smoking. Not long ago, George Will told a story
on TV about a physician in the early part of the century who ran
across a case of lung cancer and declared it to be such a rare
disease that he assembled the medical students to witness the
autopsy, believing it to be a rare opportunity.
The story may be true, but it proves nothing, because, in the
early part of this century, the diagnosis of lung cancer was
complicated by the "consumption factor". "Consumption" was a
name applied to any disease characterized by emaciation, wasting
away and coughing. It doubtless included the disease which we
now know as "tuberculosis", but it also included other diseases,
as well.
Funk and Wagnalls Encyclopedia, published in 1912, has an entry
for "consumption". It says, "See: Pthisis". Under "Pthisis" we
are told that "strictly speaking, the name includes a group of
affections, but it is generally used to indicate pulmonary
consumption, i.e., a more or less advancing process of lung
destruction, associated with progressive emaciation and other
characteristics and symptoms. This is a disease of grave
importance, from its frequency and fatal tendency. It has been
estimated that consumption is responsible for one-seventh of the
mortality of Europe. "
"Any condition that weakens the constitution favors the
development of phthisis. Thus, malnutrition, syphilis,
overcrowding, lack of fresh air, and defective hygiene, are all
factors in the causation of phthisis. More especially is this
true of occupations whose performance necessitates the
inhalation of dust particles, e.g., stone masonry, knife
grinding, metal polishing, wood carving, etc...."
"The early symptoms vary much. There may be nothing but a
gradual loss of strength, it may be of flesh; there may be
slight discharge of blood from the throat or chest; there may be
a more or less persistent tickling cough; there may be
breathlessness, with or without pain; or there may be little
except a tendency to take cold easily...."
Clearly, the state of medical knowledge about "phthisis" was
confused. The article implies that all cases of the disease
were caused by the tuberculosis germ, discovered by the great
Dr. Koch. But many of the symptoms described are applicable to
lung cancer and, in 1912, most people were treated by family
physicians who made house calls, and probably diagnosed most
disease from the symptoms, rather than from any sort of
laboratory analysis.
The Historical Statistics of the United States, published by
the Government Printing Office, give cancer statistics from 1900
to 1970, but these statistics do not differentiate between
different types of cancer. The following table, derived from
the Historical Statistics, shows the number of deaths per
100,000 of the population, for tuberculosis, influenza and
pneumonia, and malignant neoplasms (cancer), for the years from
1900 to 1970:
The government statistics contain no item for "consumption" or
for "phthisis". However, as we have seen, "consumption" was
still a recognized disease as late as 1912 (and probably later).
No doubt, those early death certificates which listed the cause
of death as "consumption" have been classified as
"tuberculosis", in the later years. Note the nice, linear and
inverse relationship between cancer deaths and deaths from
"tuberculosis" ("consumption") over the time period covered by
the chart. There is no doubt that some of the early deaths
reported from "consumption" were really lung cancer. I've also
thrown in the figures for influenza, because, in the early
years, some terminal lung cancers may have been diagnosed as
pneumonia, and also because it's simply interesting to note the
devastating impact of influenza and pneumonia in the early
years.
It is generally assume that today, doctors can easily recognize
lung cancer when they see it. But can they? In 1959, in
England, Heasman and Lipworth 25 surveyed reports from 75
hospitals of the National Health Service. Attending physicians
diagnosed 338 cases of cancer of the lung, while pathologists
discovered 417 cases, by post mortem autopsy. The attending
physicians and the pathologists agreed, however, in only 227
instances. If the pathologists were correct, 111 (33%) of the
diagnoses of the attending physicians were false positive, while
190 genuine cases of lung cancer (46%) were missed.
A similar result was obtained by Feinstein, in a study
conducted at the Yale University School of Medicine, and
published in September, 1986, in the Archives of Internal
Medicine 26
. Researchers at Yale obtained records on 3,286
adults who had died between 1971 and 1982. 153 of these
patients were found, upon autopsy, to have died of lung cancer.
The researchers then went back and obtained the death
certificates for these 153 patients and attempted to obtain
information about their smoking habits. For 13 patients,
adequate smoking information was not available, so they were
thrown out of the survey. The researchers reported, however,
that out of these 13 patients, seven had been correctly
diagnosed as having lung cancer during life, but 6 had not.
Working with the remaining 140 cases, it turned out that there
were 37 "surprise" cases of lung cancer, i.e., cases which had
not been correctly diagnosed during life. 57% of these cases
involved non-smokers; 30% involved moderate smokers; but only
16% involved heavy smokers. The researchers concluded that
there was a detection bias; that doctors were very ready to
diagnose lung cancer in a smoker; very reluctant to make the
diagnosis in a non-smoker.
Before leaving this study, it is important to point out that,
by reason of the methodology used, working from autopsies
backwards to death certificates, the study could only
expose false negatives, i.e., cases of lung cancer which had not
been discovered during life. It is a pity that the researchers
could not have conducted another study, working from death
certificates forward to autopsies. That would have yielded a
number for false positives, i.e., the number of cases diagnosed
as having lung cancer which, upon autopsy, turned out not to be
lung cancer.
At the beginning of this book, I said I would describe the work
of a British medical researcher, who questioned the hypothesis
that smoking causes disease. The researcher was the late Philip
R. J. Burch, a professor of Medical Physics at the University of
Leeds. He was a non-smoker, whose principal life work was an
attempt to develop a unified theory of cancer.
In 1976, Doll and Peto issued a paper in which they reported
that daily cigarette consumption by the British doctors who had
been studied in connection with the 1964 SG's report had
declined from 9.1 in 1951 to 3.6 in 1971. Doll and Peto claimed
that, as a result there was a 38% reduction in lung cancer death
rates amongst the doctors. In a paper 27 , however, Burch showed that
Doll and Peto had compared the lung cancer death rates among the
doctors with the lung cancer death rates for the entire British
male population. Burch re-plotted the data to compare the
doctors with themselves and showed that, on that basis, the risk
for lung cancer amongst the doctors had actually increased by
31%.
Burch may have been on to something here, even beyond what he,
himself, saw. His chart shows that during the time period 1955
to 1971, the risk of lung cancer amongst all men in England and
Wales more than doubled, while the risk amongst the doctors
increased only 31%. Remember our earlier discussion of
socio-economic status? The doctors, of course, were, as a group,
in a socio-economic class far higher than most other men. They
worked indoors at a sedentary occupation, ate different food,
and were not as susceptible to depression. Could these factors
account for the difference between the doctors and ordinary men?
In the same paper, Burch plotted cigarette consumption for
women and men in England and Wales against lung cancer death
rates, during the period 1890 to 1971. He showed that the
largest increases in LCDR's in both sexes came during the time
periods 1916- 1920 and 1931-35, when at a time when cigarette
consumption among women in England and Wales was very small.
From this Burch concluded that the rise in lung cancer was due
to improved diagnosis, not smoking. In England and Wales, there
was, in fact, a 30 year gap between the time when males began
smoking and females. So it is not surprising that the
anti-smoking crowd in Britain made the argument that recent (in
1966) increases in lung cancer among women resulted from a "30
year incubation period". Burch effectively refuted that
argument by plotting lung cancer rates for males in 1906 through
1926, against female rates for 1936 to 1966, and showing that
while, if the incubation theory was correct, the two curves
should have been synchronous, they were in fact completely
dissimilar.
Burch also wrote, extensively, about the problem of "detection
bias". Primary lung cancer can be simulated by pulmonary
metastases from carcinoma of the pancreas, kidney, stomach,
breast and thyroid, and by malignant melanoma. He suggested that
many cases diagnosed as "primary lung cancer" are not, in fact,
"primary lung cancer", but simply metastasized tumors,
originating in some other site 28 .
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