Etiologic and prevention effectiveness intervention studies in occupational health.

In this article a basic distinction is made between etiologic and prevention effectiveness intervention studies. Etiologic intervention studies focus on elucidating causes of disease, while the purpose of prevention effectiveness intervention studies is to study methods of prevention. The design requirements for each of these studies are very different: etiologic intervention studies usually need large study populations, large exposure contrasts, ascertainment of exposure, as well as health outcome. Ideally, randomization and blinding should also be applied. Effective preventive strategies may, on the other hand, be identified in small study populations with exposure as the only outcome measure, and randomization and blinding may be superfluous. At present, intervention studies are in great demand, and often there is a wish that etiologic questions as well as prevention effectiveness be addressed in the same study. We argue that this should not be done without careful consideration of possible conflicting design aspects.