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Re: Radon - county linear model and LNT
> As Dr. Lubin's pointed out, "Cohen's claims are based on his linear (or
> linear- quadratic) model for county lung cancer rates, are therefore built on
a false premise, and his continual reference to the `scientific method' is
fatuous.
Cohe replied --I do not use any such model, and don't know what he is talking
about.
Dr. Cohen, are you now saying you are not using a linear model to test the LNT?
You previously said you derived a LNT model that was equivalent to the BIER IV
model. Do you recall the discussions we had concerning the validity of your
assumptions you used for your model?
---------------------
I would like to see a point-by-point response to his paper. But, how can you
adequately respond to Lubin if you don't understand his points?
------------------------------------
------------------------------------------------------------------------>
On Tue, 24 Jun 2003 epirad@mchsi.com wrote:
>
> > I am pointing out a response by Lubin that I am in agreement with
> >
> > Cohen wrote: --My response to that paper, Jour. Rad. Prot. 22(2002)305-307, is
> > > available on the web at http://www.iop.org/EJ/toc/0952-4746/22/3 The
> > > problem is that it contains no consideration of plausibility. For example.
> > > it hypothesizes that the ratio of radon exposures for smokers/non-smokers
> > > in a county varies with county average radon levels, r, from 7.0 for r=30,
> > > to 1.0 for r=75, to 2.2 for r=90, to 0.36 for r=150; all this at a time
> > > when nothing was known about radon levels.
> > --------------
> >
> > As Dr. Lubin's pointed out, "Cohen's claims are based on his linear (or
> linear-
> > quadratic) model for county lung cancer rates, are therefore built on a false
> > premise, and his continual reference to the `scientific method' is fatuous.
>
> --I do not use any such model, and don't know what he is talking
> about. In any case, what does this have to do with my above comments?
>
> One
> > could equally fit and reject a sinusoidal relationship for county lung cancer
> > rates and radon concentrations; the factual basis of an inadequate model is
> > true, but of little inferential value for evaluating risk."
>
> --Again, I have no idea of what he is talking about.
>
> > Reply to Cohen's letter on `The potential for bias in Cohen's ecological
> > analysis of lung cancer and residential radon'
>
> --I was not given an opportunity to respond to this pile of BS. He
> completely ignores my tightly reasoned justification for my procedures, as
> given in item #7 on my web site. He completely ignores issues of
> plausibility. He completely ignores the fact that my study is not designed
> to determine risks, but only to test LNT. He shows no understanding of my
> new and novel approach to solving a scientific problem. If anyone wants a
> response on any one point, please ask.
>
> > Dear Sir
> >
> > In the above letter, Cohen [1] repeats arguments that he as made in the past;
> > however, the thrust of those comments indicates a fundamental misunderstanding
> > of the point of my article [2] and indeed of my prior articles on this topic.
> > It was not and has never been my goal to identify a specific factor (or
> several
> > factors) that induced the negative correlation between the estimates of
> county-
> > level mean radon concentration and county lung cancer mortality rates. Other
> > investigators have offered powerful examples, both theoretical and practical,
> > that Cohen's results are indeed an artifact of ecological regression [3-9].
> The
> > primary purpose of my contributions to this topic has been to demonstrate the
> > fundamental deficiencies of the methodology itself, in particular the
> > unboundedness of the bias [10]. The current article [2] demonstrates that the
> > ecological fallacy always applies, that the addition of county-level
> adjustment
> > variables does not reduce bias and increase validity, and that an observed
> > ecological risk pattern can differ markedly from the true risk pattern.
> Because
> > of these deficiencies, epidemiologists have never used ecological regression
> as
> > a tool for confirmatory analysis. For radon and lung cancer, results of 25-30
> > analytic studies of individuals clearly prove the deficiency of the method.
> >
> > There are numerous risks factors for lung cancer, including smoking, age,
> > various occupational exposures, air pollution, previous lung diseases, and so
> > on. In [2], I take an extremely simplified model for lung cancer in radon and
> > smoking status, and demonstrate that the induced county-level model is non-
> > linear. A more realistic, and complex, model for lung cancer would include all
> > principal risk factors, and would also generate a non-linear model at the
> > county level. Cohen's claims, which are based on his linear (or linear-
> > quadratic) model for county lung cancer rates, are therefore built on a false
> > premise, and his continual reference to the `scientific method' is fatuous.
> One
> > could equally fit and reject a sinusoidal relationship for county lung cancer
> > rates and radon concentrations; the factual basis of an inadequate model is
> > true, but of little inferential value for evaluating risk.
> >
> > Given two counties with equal proportions of smokers and equal patterns of
> > smoking, I showed that a positive association for radon and lung cancer at the
> > individual level can be easily transformed into an observed negative
> > relationship between lung cancer rates and mean radon levels at the county
> > level through simple manipulations of the within-county correlation between
> > smoking and radon [10]. Moreover, the within-county correlations can be
> > extremely small, on the order of 0.05 to 0.10 (see table 1 in [10]). The
> > current paper [2] extends that two-county analysis, and shows that the
> reversal
> > in trend can be extended to all 1,599 counties in Cohen's regression, even
> when
> > the ecological regression is assumed to perfectly fit the data with no
> residual
> > variation. Those results demonstrate the potential for extreme distortion of
> > any ecological regression.
> >
> > A relatively simple within-county adjustment was needed to show the
> > compatibility of Cohen's regression with the BEIR VI extrapolation of risk.
> > Contrary to Cohen's view, the vast majority (84 per cent) of within-county
> > correlation coefficients for radon and smoking were between -0.3 and 0.3. In
> > addition, those correlations are artificially elevated due to measurement
> > error. The implicit assumption is that all covariates are measured without
> > error. However, it is clear cigarette smoking is very poorly measured. A total
> > of 85-90 per cent of all lung cancers are attributed to cigarette consumption,
> > while Cohen's smoking variable explains only about 25 per cent of the
> variation
> > in lung cancer rates among counties. Equation (3) in [2] defines the risk-
> > adjusted radon concentration for a county (denoted w) as represented in the
> > true county-level regression. The risk-adjusted mean radon depends on the
> > proportion of smokers and the relative risk of smoking for the county. Thus,
> > even if errors in smoking status and residential radon concentration were
> > independent at the individual level, equation (3) shows that the proportion of
> > smokers and w are correlated. Thus, county-level correlations between smoking
> > and radon are further distorted by the joint misclassification of two factors.
> >
> > Finally, as a practical matter, it is worth noting that Puskin has recently
> > offered a plausible explanation for Cohen's negative correlation [11] that
> > agrees with the possible role of correlated errors. Puskin conducted
> ecological
> > regressions of radon and smoking for several strongly smoking-related cancers
> > (cancers of the lung, oesophagus, larynx, nasopharynx and oral cavity), weakly
> > smoking-related cancers (cancers of the bladder and pancreas) and cancers
> > unrelated to smoking (cancers of the colon, breast and prostate). He found
> > strong negative correlations between county radon concentrations and cancers
> > strongly linked to cigarette smoking, weaker correlations between radon and
> > cancers weakly associated with smoking, and essentially no correlation between
> > radon and cancers not linked to smoking. Puskin concludes that the negative
> > trend reported by Cohen for lung cancer is very likely explained by a negative
> > correlation between smoking and radon levels across counties.
> >
> > Yours faithfully,
> >
> > J H Lubin
> >
> > [1] Cohen B L 2002 Response to `The potential for bias in Cohen's ecological
> > analysis of lung cancer and residential radon' J. Radiol. Prot. 22 305-7
> > IOP Article
> >
> > [2] Lubin J H 2002 The potential for bias in Cohen's ecological analysis of
> > lung cancer and residential radon J. Radiol. Prot. 22 141-8
> > IOP Article
> >
> > [3] Greenland S 1992 Divergent biases in ecologic and individual-level studies
> > Stat. Med. 11 1209-23
> > PubMed Abstract | Buy at Infotrieve
> >
> > [4] Greenland S and Robins J 1994 Invited commentary: ecologic studies -
> > biases, misconceptions, and counterexamples Am. J. Epidemiol. 139 747-60
> > PubMed Abstract | Buy at Infotrieve
> >
> > [5] Morgenstern H 1995 Ecologic studies in epidemiology: concepts, principles,
> > and methods Ann. Rev. Public Health 16 61-81
> > CrossRef Link | Buy at Infotrieve
> >
> > [6] Muirhead C R, Butland B K, Green B M R and Draper G J 1991 Childhood
> > leukaemia and natural radiation (letter) Lancet 337 503-4
> > ChemPort Abstract | PubMed Abstract | Buy at Infotrieve
> >
> > [7] Piantadosi S, Byar D P and Green S B 1988 The ecologic fallacy Am. J.
> > Epidemiol. 127 893-904
> > ChemPort Abstract | PubMed Abstract | Buy at Infotrieve
> >
> > [8] Stidley C A and Samet J M 1994 Assessment of ecologic regression in the
> > study of lung cancer and indoor radon Am. J. Epidemiol. 65 234-51
> > Buy at Infotrieve
> >
> > [9] Smith B J, Field R W and Lynch C F 1998 Residential Rn-222 exposure and
> > lung cancer: Testing the linear no-threshold theory with ecologic data Health
> > Phys. 75 11-7
> >
> > [10] Lubin J H 1998 On the discrepancy between epidemiologic studies in
> > individuals of lung cancer and residential radon and Cohen's ecologic
> > regression Health Phys. 75 4-10
> > Inspec Abstract | ChemPort Abstract | PubMed Abstract | Buy at Infotrieve
> >
> > [11] Puskin J S 2002 Smoking as a confounder in ecological correlations of
> > cancer mortality rates with average county radon levels Health Phys.
> > >
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> >
> >
>
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