Is Iodide a Confounding or Effect Modifying Factor of Liver Cirrhosis?

Abstract

Development of a disease in a human population is generally a multifactorial process, characterised by the operation of both direct (or causal) and indirect (or confounding and effect modification) factors. In most cases, the focus of epidemiological interest is on the effects of the causal factors. Confounding and effect modification factors, however, may act either to magnify or damp down these effects. Confounding factors are independent of the exposure and the health outcome but can modify both. Effect modifiers act concurrently with the exposure but independently of it: they modify the effect of the exposure—that is, the health outcome — but not the exposure itself (Miettinen 1974, 1995, Ely 1992.)