To the Editor:
We consider the article by Greenland et al1 and the authors’ response2 to the related commentaries to be a very important contribution. However, we think that the following points, not raised in the commentaries,3–6 should be addressed.
To propose that research in risk-factor epidemiology should not concern itself with a theoretical component, and thus become only an empiric part of a current or future theory, does not permit one to make a distinction between scientific investigation and ordinary knowledge. To have epidemiologic articles concerned only with the description of methods, analysis, and data would not permit a differentiation between the knowledge generated by such persons as reporters, detectives, and so on, and the knowledge designated as “scientific” by Greenland et al.1 This would mean that the knowledge generated in epidemiologic studies would be considered as lacking scientific content.
In the example that was used, to speak of a unifying theory could fall into a certain contradiction. Although the value of the articles with null associations is clearly shown, the example that is cited is based solely on positive associations. This does not take into account that, from the point of view of the falsificationist approach, the evidence against the theory is the most relevant.
Although it was not possible to develop a theory on the process of transformation from health to illness, placing replication and precision on the same plane as validity and novelty begs the following question: When would it be pertinent to end the replication of a fact about a topic of investigation in the absence of a theory that explains and predicts a disease? Given that the value of replication and precision is evident, how many studies are necessary and what degree of precision is acceptable to end research on a topic if a theory is never proposed?
Finally, to propose that risk-factor epidemiology need not show its use for public health creates the problem of distinguishing between epidemiologic and basic research. Today, various agencies that fund research require that proposed projects include a description of the usefulness of, and benefits to be derived from, the findings. To lose sight of the use of public health studies would mean that one of the most important functions of all epidemiologic investigation—the only discipline of research capable of establishing the relation between environmental factors and the health of human populations—would be lost.
Juan Manuel Mejía-Aranguré
Epidemiologia Clinica, Hospital de Pediatria, Centro Medico Nacional “Siglo XXI”, Atizapan, Mexico, firstname.lastname@example.org
Clinical Epidemiology, Hospital de Pediatria, Centro Medico Nacional SXXI, Atizapan, Mexico
1. Greenland S, Gago-Dominguez M, Castelao JE. The value of risk-factor (‘black box’) epidemiology. Epidemiology
2. Greenland S, Gago-Dominguez M, Castelao JE. Authors’ response. Epidemiology
3. Susser E. Eco-epidemiology: thinking outside the black box [Commentary]. Epidemiology
4. Haack S. An epistemologist among the epidemiologist [Commentary]. Epidemiology
5. Mayo DG, Spanos A. When can risk-factor epidemiology provide reliable test? [Commentary] Epidemiology
6. Weiss NS. Presents can come in black boxes, too [Commentary]. Epidemiology