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Re: Concrete Ecologic Example Myth
On Sat, 21 Jun 2003 epirad@mchsi.com wrote:
> In Cohen's ecologic study, this is what I see:
--I have responded to all of these point in the last few days. If
anyone wants repeats of one of these responses, please specify
>
> 1.) An inverse relationship between estimated county smoking information and
> estimated county radon concentrations. Maybe the reason for this should be
> explored first.
>
> 2.) Estimated county smoking rates explaining little of the variation in
> county lung cancer mortality.
>
> 3.) Uses smoking data that can not adjust for duration of smoking or intensity
> of smoking.
>
> 4.) Estimated lung cancer incidence rates for the time period of interest
> being poorly estimated by lung cancer mortality data from a different time
> period.
>
> 5.) An inverse association between estimated county radon concentrations and
> other smoking related cancers not related to radon, which to me and most
> others points to confounding by smoking.
>
> 6.) The negative association goes away in Iowa (a state with 1% of the U.S.
> population but 1/16 of the U.S. ecologic units) if I merely use better SEER
> lung cancer incidence data. Dr. Cohen's only answer for this is that there
> must be some problems associated with ethnic minorities in Iowa.
>
> etc.
>
> Given these facts, I am not motivated to perform studies analogous to little
> green men.
>
> Perhaps Cohen could set up 1600 ecologic units starting with an inverse
> association that he finds between smoking and radon, counties unevenly
> weighted by population and geographic area and randomly sample (yes, he would
> have to get better data by surveys of counties)the joint distribution of
> smoking and related socioeconomic variables in a Monte Carlo analyses?
>
> Email me directly and I would be happy to point you to existing papers that
> document points 1-4 below. If you would read the papers that document my
> statements below, I think you would understand the limits of ecologic analyses
> and the fact it has little to do with dose response.
>
> Bill Field
> > Bill,
> >
> > I think you are confusing trying to establish a dose response relationship
> > from ecological data with testing a particular theory against an ecological
> > observation. These issues are not limited to epidemiology. It tends to be
> > difficult (impossible?) to formulate a theory of how small things interact
> > by just looking at the end result of the interaction, but any valid theory
> > must still be compatible with the observation.
> >
> > If I look at Mars and it looks red, that is not proof that Mars is populated
> > by a bunch of compulsive Martians who go around painting everything red.
> > However, if you have a theory that states that Mars is populated by a bunch
> > of compulsive Martians who go around painting everything green, then my red
> > observation is a problem for your theory. That doesn't mean your theory is
> > wrong, but it would sure help if you could come up with an explanation that
> > reconciles your theory with my observation. (e.g. Martians have wives that
>
> > go around covering the green paint up with red blankets.)
> >
> > To me, no one has come up with an explanation that makes LNT compatible with
> > the ecological observation. Until that happens, I can't accept LNT as a
> > valid scientific theory. (Using LNT as a basis of regulation is a different
> > story.)
> >
> > You state that many examples have been given on how Dr. Cohen's data can be
> > biased. I don't recall any that seem reasonable to me. All I need is one
> > NUMERICAL example. Put 1600 hypothetical counties on a spreadsheet. Put in
> > some confounders (Martian wives) and reproduce the ecological observation.
> > (You correctly state that it may be impossible to IDENTIFY empirical sources
> > of ecologic bias from aggregate data alone, but that should not stop you
> > from POSTULATING them.)
> >
> > Kai
> >
> > ----- Original Message -----
> > From: <epirad@mchsi.com>
> > To: "Kai Kaletsch" <eic@shaw.ca>
> > Cc: "BERNARD L COHEN" <blc+@PITT.EDU>; <radsafe@list.vanderbilt.edu>
> > Sent: Friday, June 20, 2003 12:54 PM
>
> > Subject: Concrete Ecologic Example Myth
> >
> >
> > > Kai,
> > >
> > > I know we have gone through discussions about the limitations of ecologic
> > > studies many times but there are some points that a few radsafers continue
> > to
> > > miss.
> > >
> > > You suggested the other day putting an upper limit on the error from an
> > > ecologic study. Unfortuantely, this is not easy to do since the error in
> > > ecologic studies is unbounded.
> > >
> > > Others problems to keep in mind -
> > >
> > > 1) It is not possible to identify empirical sources of ecologic bias from
> > > aggregate data alone. Researchers must rely on prior knowledge of
> > intergroup
> > > variation in the distribution of other risk factors and effect modifiers.
> > > We don't know this inter group variation for Dr. Cohen's data nor has he
> > > adjusted for it.
> > >
> > > 2) Factors responsible for ecologic bias may not be confounders or effect
> > > modifiers at the individual level and that identifying the bias is even
> > more
> > > difficult because factors may not even "appear" to be confounders or
>
> > modifiers
> > > at the ecologic level.
> > >
> > > 3) Ecologic biases can even reverse the direction of an observed
> > association,
> > > especially when the range of average exposure levels across groups is
> > small or
> > > the exposure under study is not a strong risk factor regardless even if
> > you are
> > > using an ecologic study to test the LNT.
> > >
> > > 4) If cross level bias is occurring (which we know it is), ecologic data
> > can
> > > not be successfully used to adjust for ecologic bias.
> > >
> > > Many examples have been given on how Dr. Cohen's data can be biased and
> > since
> > > Cohen will use his own faulty data to test the "concrete" example;
> > providing
> > > a "concrete" example is doing no more than providing an explanation Cohen
> > will
> > > use his own faulty data to negate. So, the circle will never end.
> > > > Friends,
> > >
> > > > We are all aware that ecological studies have some limitations - these
> > issues have been discussed (some would say ad
> > > > infinitum) on this board and elsewhere.
> > >
>
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> > >
> >
>
>
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