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Re: Radon - county linear model and LNT
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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