Complexity and indeterminism of evidence-based public health: an analytical framework.

Improving the evidence in public health is an important goal for the health promotion community. With better evidence, health professionals can make better decisions to achieve effectiveness in their interventions. The relative failure of such evidence in public health is well-known, and it is due to several factors. Briefly, from an epistemological point of view, it is not easy to develop evidence-based public health because public health interventions are highly complex and indeterminate. This paper proposes an analytical explanation of the complexity and indeterminacy of public health interventions in terms of 12 points. Public health interventions are considered as a causal chain constituted by three elements (intervention, risk factor, and disease) and two levels of evaluation (risk factor and disease). Public health interventions thus differ from clinical interventions, which comprise two causal elements and one level of evaluation. From the two levels of evaluation, we suggest a classification of evidence into four typologies: evidence of both relations; evidence of the second (disease) but not of the first (risk factor) relation; evidence of the first but not of the second relation; and no evidence of either relation. In addition, a grading of indeterminacy of public health interventions is introduced. This theoretical point of view could be useful for public health professionals to better define and classify the public health interventions before acting.