RE: "A FRAMEWORK FOR DESCRIPTIVE EPIDEMIOLOGY".

Abstract

In a recent article, Lesko et al. presented a detailed “framework for descriptive epidemiology” while also stating, “Many, if not all, of the considerations discussed in this framework apply to estimation of valid causal effects” (1, p. 2063). Although the article contains many highly reasonable ideas, its contribution to the advancement of the understanding of descriptive epidemiology vis-à-vis its nondescriptive counterpart may be hampered by the apparent conflation of the concept of epidemiology as the practice of community medicine with epidemiology as a genre of health research/science. Consequently, some statements in the article—in particular, those regarding descriptive topics, unconcerned with causality—refer to inquires in epidemiologic practice (e.g., community-level diagnostication), while others—in particular, those regarding causal topics—refer to epidemiologic research. However, certain similarities between them notwithstanding, these types of activities fundamentally differ in their essence, objects of inquiry, and theory. Notably, the authors state, “A well-defined research [sic] question (causal or descriptive) states: 1) the target population, characterized by person and place, and anchored in time…” (1, p. 2065); but unlike in inquiries in epidemiologic practice, there is no place- and time-specific target population in either causal or descriptive epidemiologic research, where the domain of inference is a particular theoretical/abstract (super-)population, infinite in size. Consequently, validity assurance generally requires representative sampling (in the selection of the sample of the target population) in survey-type inquires in epidemiologic practice, but not (in the selection of the study base/population from the source population) in epidemiologic research. On the other hand, assurance of applicability of (the knowledge produced from) the results of epidemiologic research to a multitude of place- and time-specific populations cared for by community-medicine practitioners requires thorough attention to modifiers of the magnitude(s) of the parameter(s) at issue, while no such imperative generally exists in inquiries in epidemiologic practice. Unfortunately, the difference of the practice-pertinent concept of target population from the research-pertinent concepts of study population and superpopulation is left unexplained.