Risk-based medicine, a hieroglyph full of traps

Jordi Varela
Editor

 

Gerd Gigerenzer, Director of the Harding Center for Risk Literacy at the Max Plank Institute for Human Development in Berlin, was featured in this blog in 2016 following the publication of "Risk Savvy. How to make good decisions." Gigerenzer's crusade against risk manipulation and its consequences are consistent and tenacious, and that's why we should use more of his materials to help overcome the traps of malicious numbers if we want to practice proportionate medicine to address the real risks to peoples health. The following video which was edited in February 2020 by the Gigerenzer factory,  turns out to be essential in differentiating between absolute risk and relative risk.

According to the video, when the Australian press headlines warn that shark attacks have doubled, it would be fair if, at the same time, they said that their incidence has gone from one to two attacks for every two million divers. In the same way, when women are informed that if they agree to enter a breast cancer prevention plan through mammograms every two years, pushed by the magic data of 20% in the reduction of mortality, it would also be fair if they would be informed that this reduction is part of a decrease from five to four deaths for every thousand women in the program, a reduction that in terms of absolute risk is 0.1%.

Gigerenzer explains that relative risks, which are always more striking, are used insistently to encourage people to make decisions that are favourable to the interests of the promoters or detractors of a certain program as it suits them. Let's put a clear case of risk manipulation that, explains Professor Gigerenzer in the following video, was experienced in England and Wales in the 60s with the appearance of third-generation contraceptives when it was noticed that the risk of thrombosis had increased by one to two cases per seven thousand female users, so some newspapers said that the risk of thrombosis had doubled (which was, relatively speaking, true), but there was a headline that announced that the risk of thrombosis had increased by 100% because of the new pills and panic skyrocketed. The result was immediate and there was a large increase in teenage pregnancies and an excess of 13,000 abortions per year.

A sign of the lack of collective rationality in the understanding of risk by societies, explains Gigerenzer, was seen in the reaction of Americans after September 11, 2001. The vast majority avoided air travel and the consequence was an increase in road traffic, especially over long distances, with the estimated result of some 1,600 excess deaths on the roads, which could have been avoided if, as they had before, take the plane, since, during the studied period, no aviation accident was recorded in that country.

Gigerenzer says that as in the last century a large part of the world population learned to read and write, now it would be useful to teach the youth to make decisions based on realistic estimates. If this is not done, risk-based medicine will always be in the hands of opaque interests.