Heisenberg Chair for Medical Risk Literacy & Evidence-Based Decisions

An evidence-based health care requires risk-savvy doctors and patients. Yet, our health care system falls short on both counts.

To illustrate the extent: In a national study of 412 U.S. primary care physicians, most physicians did not know that the 5-year survival statistic—often used to communicate the benefit of screening—is a biased metric in the context of screening. Among German gynecologists who were explicitly asked for numerical information on the benefits and harms of mammography screening, not a single one provided all information required for a patient to make an informed choice. Of 32 German HIV counselors, only one were able to correctly explain the meaning of a positive HIV test. And in a study with nearly 1,700 women from 5 European countries, the majority of women overestimated their likelihood to develop certain female cancers by orders of magnitude, whereas less than one third was aware of the fact that mammography screening can also cause harms.

Why do we have this lack of risk literacy? One frequently discussed answer assumes that people suffer from cognitive deficits that make them basically hopeless at dealing with statistics. Yet the fact that even 4th-graders can understand the positive predictive value if information is presented as natural frequencies shows that the problem can lie in how information is presented. Still, a transparent presentation of risk may not eliminate all of the observed misinterpretation of risk in medicine. When, for instance, over 400 US gynecologists were presented with an easy-to-understand summary of the current best evidence on ovarian cancer screening, about half did not revise their initial assumptions about the screening’s benefit-harm-ratio, although these assumptions were incorrect. Insights from cognitive sciences imply that people’s perception and dealing with risks does not only depend on how statistics is taught and communicated, but also on how medical risk information is transformed when travelling through social networks, and on how people initially learn about a risk (by description or by experience).