Definition of Epidemiology

[dj_strom@ccmail.pnl.gov (Daniel J Strom)]

BLC = Bernard L. Cohen <blc+@pitt.edu>
DJS = Daniel J. Strom <dj_strom@pnl.gov>

>>>> BLC: I am not sure that my work should be called "epidemiology."  
It is a test of a specific theory. Tests of a theory are at the heart of 
"the scientific method" and apply rigorously to all of science. The 
baggage attached to ecological studies does not apply to, or affect such 
a test.

>>>> DJS: Definition of Epidemiology.  The study of the distribution and 
determinants of health-related states or events in specified 
populations, and the application of this study to control of health 
problems.  "Study" includes surveillance, observation, hypothesis 
testing, analytic research, and experiments.  "Distribution" refers to 
analysis by time, place, and classes of persons affected.  
"Determinants" are all the physical, biological, social, cultural, and 
behavioral factors that influence health.  "Health-related states and 
events" include diseases, causes of death, behavior such as use of 
tobacco, reactions to preventive regimens, and provision and use of 
health services.  "Specified populations" are those with identifiable 
characteristics such as precisely defined numbers.  "Application to 
control..." makes explicit the aim of epidemiology - to promote, 
protect, and restore health (Last 1995).

>>>> BLC: It is a test of a specific theory.  Tests of a theory are at 
the heart of "the scientific method" and apply rigorously to all of 
science.  The baggage attached to ecological studies does not apply to, 
or affect such a test.

>>>> DJS: Dr. Cohen has not convinced me or other critics that "the 
baggage attached to ecological studies" does not apply to a study for 
which there are no individual exposures, no individual confounder 
measures, and no individual bias measures associated with individual 
health outcomes.  

See Figure 3 of Lubin and Boice (1997) for an example of how Dr. Cohen's 
results are statistically rejected by more cogent studies.

>>>> BLC: I have clearly shown that testing a linear- no threshold 
theory does not require data for individuals.  If Strom disagrees with 
these demonstrations, he should say specifically why.  I can very easily 
explain why data for individuals is needed to determine a dose-response 
relationship; why can't he explain why data for individuals is necessary 
to test an LNT theory?

>>>> DJS: The county radon measurements made long after many of the 
cancer deaths apply only weakly to the individuals who died of lung 
cancer in those counties.  Most importantly, many other causes of lung 
cancer (i.e., confounders) that may be associated with (covary with) 
geographic location, e.g., air pollution, different genetic make up, and 
lifestyle factors (especially smoking), cannot be controlled in any 
meaningful way despite Dr. Cohen's attempts and his claims.  Dr. Cohen's 
study is useful for generating the hypothesis that radon exposure is 
causally related to lung cancer (one way or the other).  That hypothesis 
has been, and is being, tested by more cogent epidemiologic methods.  
These simple statements have been made repeatedly in print (see, e.g., 
Lubin and Boice 1997), but Dr. Cohen doesn't accept them.  His 
persistence doesn't change the truth of the simple statements.

See Lubin and Boice (1997) and Lubin et al. (1997) for good recent 
discussions.  Stay tuned for BEIR VI, due out this spring.  

References

Last, J.M., ed.  A Dictionary of Epidemiology.  A Handbook Sponsored by 
the International Epidemiological Association. 3rd edition. New York: 
Oxford University Press; 1995.

Lubin, J.H.; Boice Jr., J.D.  Lung cancer risk from residential radon: 
meta-analysis of eight epidemiologic studies.  Journal of the National 
Cancer Institute 89(1):49-57; 1997.

Lubin, J.H.; Tomásek, L.; Edling, C.; Hornung, R.W.; Howe, G.; Kunz, E.; 
Kusiak, R.A.; Morrison, H.I.; Radford, E.P.; Samet, J.M.; Tirmarche, M.; 
Woodward, A.; Yao, S.X.  Estimating Lung Cancer Mortality from 
Residential Radon Using Data for Low Exposures of Miners.  Radiation 
Research 147(2):126-134; 1997.

The opinions expressed above are my own, and have not been reviewed or 
approved by Battelle, the Pacific Northwest National Laboratory, or the 
U.S. Department of Energy.

Daniel J. Strom, Ph.D., CHP
Staff Scientist
Health Protection Department K3-56
Pacific Northwest National Laboratory
Battelle Boulevard, P.O. Box 999
Richland, WA 99352-0999 USA
(509) 375-2626
(509) 375-2019 fax
dj_strom@pnl.gov