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Re: Fw: Epidemiology Epedemic
Jerry,
Thanks for passing this along. It is very interesting
reading. Conincidentally, I am reading Marilun vos
Savant's "The Power of Logical Thinking" which has
many excellent examples of how our thinking can
mislead us.
http://www.amazon.com/exec/obidos/tg/detail/-/0312139853/qid=1088968814/sr=1-3/ref=sr_1_3/103-8945587-4661468?v=glance&s=books
I think there are two facets that need to be
considered. First, there is a need for some sort of
guidance in our lives. We all want to know about what
is good for us. That is why there are a lot of
followers of astrology, beliefs in aliens (who will
save us), etc. Science seems to offer a lot. Before
WW II, and probably even today, there is a belief that
scientists should guide government and our society.
However, there is limits to what we know and can
determine. Part of this is the faith in numbers. The
more digits, the better result. The smaller the P
value the better the study. The P value only speaks
to the reliability of the numbers, not to the source
of the numbers. That is, if the sampling size is too
small or biased, the statistics may be impressive but
the results may be worthless. People love numbers,
but may not understand what is behind them.
Second, I think that may of the researchers them
selves put too much emphasis on the work. This is
probably due to the emphasis on "publish or perish."
I would look at the article by Brenner, et. al.,
"Estimated risks of radiation-induced fatal cancer
from pediatric CT," AJR Am J Roentgenol. 2001
Feb;176(2):289-96.
http://www.ajronline.org/cgi/content/abstract/176/2/289
As stated in the abstract:
". . . Estimated lifetime cancer mortality risks
attributable to the radiation exposure from a CT in a
1-year-old are 0.18% (abdominal) and 0.07% (head)-an
order of magnitude higher than for adults-although
those figures still represent a small increase in
cancer mortality over the natrual background rate. .
."
The question that should be asked is, can these
increases in risk be determine? If not, all we have
is an ability to estimate an unreliable conclusion.
Yet, this article sparked a tremendous amount of
interest in radiology and medicine.
I am sure others can cite similar studies.
--- jjcohen <jjcohen@PRODIGY.NET> wrote:
>
> ----- Original Message -----
> From: jjcohen
> To: Jerry Cohen
> Sent: Friday, July 02, 2004 4:38 PM
> Subject: Fw: Epidemiology Epedemic
>
>
>
> ----- Original Message -----
> From: jjcohen
> To: radsafe@list.vanderbilt.edu
> Sent: Friday, July 02, 2004 4:08 PM
> Subject: Fw: Epidemiology Epedemic
>
>
>
>
>
> In previous discussions on radsafe, concerns were
> expressed regarding how
> epidemiology had been applied in determining effects
> of exposure to radon,
> radioactivity , and 'hazardous" materials in
> general.
> It appeared, at least to me, that certain
> epidemiological determinations
> were being made that defied common sense. Recently,
> on another website, I
> came across the following review and thought the
> group might be interest.
> Anyone have any thoughts on the subject?? Jerry
> Cohen
>
----------------------------------------------------------------------------
> -----------------------
>
>
>
> An Epidemic of Epidemiology
> by Rob Lyons
>
> Fifty years ago, we discovered that smoking is bad
> for us. In 1954, Austin
> Bradford Hill and Richard Doll published a
> preliminary report on a study
> showing the very strong correlation between smoking
> and premature mortality
> (1).
>
>
> However, this classic study has in many ways sent
> medical science up a blind
> alley. While the dangers of smoking have been
> demonstrated in numerous
> subsequent studies, the attempts to find the New
> Smoking - another example
> of an environmental or lifestyle factor that causes
> substantial health
> problems - have largely failed. But the many pieces
> of junk science that
> have been produced in the process have provided the
> ammunition for
> unwarranted health scares too numerous to mention.
>
>
> This state of affairs is well described in John
> Brignell's new book The
> Epidemiologists. Hill and Doll were given the task
> of trying to find out why
> cases of lung cancer had increased 15-fold in only
> 25 years. Their first
> attempt was to ask 649 lung cancer patients, and 649
> matched controls, about
> their habits. What they found was a correlation
> between smoking and lung
> cancer, albeit not a very strong one. However, it
> was strong enough to
> warrant a fuller study, starting with a large group
> of healthy individuals,
> assessing their smoking habits and then monitoring
> them to see what diseases
> they developed.
>
>
> This study began in 1951. Their method was to write
> to every doctor in the
> country - around 35,000 doctors replied, of whom
> only 17 per cent were
> lifelong non-smokers (how times change). The doctors
> were asked just a few
> questions about their smoking habits. Three years
> later, Hill and Doll
> published their first analysis of the results, and
> were already able to
> indicate how strong the link was between smoking and
> lung cancer.
>
>
> What they found was that persistent smokers were 24
> times more likely to
> develop lung cancer than non-smokers. Moreover, the
> risk of death from heart
> disease in any particular year was roughly doubled.
> This study has been
> followed up every few years, and these results have
> been confirmed time and
> again.
>
>
> Hill made it clear, however, that such a study had
> to comply with some
> pretty strict criteria in order to be considered
> valid. These criteria are
> worth restating, because they stand in sharp
> contrast to the bulk of
> epidemiological research:
>
> 1. Strength
>
> Is the association strong enough that we can rule
> out other factors?
>
> 2. Consistency
>
> Have the results been replicated by different
> researchers, and under
> different conditions?
>
> 3. Specificity
>
> Is the exposure associated with a very specific
> disease as opposed to a wide
> range of diseases?
>
> 4. Temporality
>
> Did the exposure proceed the disease?
>
> 5. Biological gradient
>
> Are increasing exposures associated with increasing
> risk of disease?
>
> 6. Plausibility
>
> Is there a credible scientific mechanism that can
> explain the association?
>
> 7. Coherence
>
> Is the association consistent with the natural
> history of the disease?
>
> 8. Experimental evidence
>
> Does a physical intervention show results consistent
> with the association?
>
> 9. Analogy
>
> Is there a similar result to which we can draw a
> relationship?
> Above all, as Brignell emphasizes, correlation does
> not prove causation. He
> draws an analogy with growing tomatoes and
> fertilizer. It can easily be
> shown that increasing use of fertilizer will
> increase tomato yields. But
> fertilizer does not cause tomatoes, it merely
> promotes the process of
> growth. The same goes for smoking and lung cancer.
> Smoking may massively
> promote the growth of lung cancer, but it does not
> cause the tumours. Hill
> and Doll had nothing to say about why cancer occurs
> in the first place.
>
>
> Nonetheless, it is an entirely reasonable conclusion
> to draw that smokers
> will, on average, die younger than non-smokers, and
> we do not need to know
> the precise mechanism to conclude that giving up
> smoking is prudent from a
> health viewpoint.
>
>
> What is not reasonable is the response to this one,
> classic study. First, it
> has provided the justification for state
> intervention in lifestyle in a
> previously unprecedented way. Secondly, it has
> encouraged the proliferation
> of other studies, which make grand statements about
> disease based on
> correlations far weaker than those found by Hill and
> Doll.
>
>
> Brignell's book is a handy demolition of the science
> and statistics behind
>
=== message truncated ===
=====
+++++++++++++++++++
"To be persuasive, we must be believable,
To be believable, we must be credible,
To be credible, we must be truthful."
Edward R. Murrow
-- John
John Jacobus, MS
Certified Health Physicist
e-mail: crispy_bird@yahoo.com
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