Explaining risk reductions in medical practice : prevention or postponement?

Abstract

Diagnosis, treatment and follow up of risk conditions such as hypercholesterolemia and osteoporosis are prominent tasks of contemporary medical practice. The aim is to prevent, or at least postpone the onset of adverse health outcomes such as angina pectoris, heart attacks, strokes and fractures. Dealing with risks involves decision making under uncertainty. For patients to be able to engage meaningfully in shared decision making, benefits of risk reducing interventions must be communicated in easily comprehensible ways. From randomised controlled trials effectiveness of such interventions may be estimated and conveyed in traditional formats such as relative risk reduction, absolute risk reduction or number needed to treat (NNT), Alternatively, to account for the time dimension, prolongation of (disease free) life or, equivalently, postponement of adverse events may be used. There is ample evidence that the different formats for risk reductions yield different decisions, i.e. framing effects. The most consistent finding is that decision makers are more inclined to accept interventions when risk reductions are explained in relative rather than absolute terms. To some extent decisions on hypothetical drug therapies by NNT and postponement of adverse outcomes have been studied empirically. It appears that lay people are insensitive to effect size in terms of NNT but sensitive to the length of postponement. The aim of this Ph. D. study was to explore how physicians and lay people understand and respond to the concepts of NNT and postponement when making decisions about risk reducing interventions against cardiovascular diseases and osteoporosis.