What is my risk, doctor? How to convey disease risk and treatment effects

Ms Olsen is a 65 year old woman with hypercholesterolaemia and hypertension. Her doctor tells her that she can reduce her risk of getting a major cardiovascular event by up to 50% if she takes a statin. “That’s great,” she thinks, “50% reduction is a lot!” She feels happy and well informed and plans to take the statin.

After she comes home, she remembers her recent conversation with a car dealer (she really needed a new car). He told her a car he had in his lot was reduced in price by 15%. May be a good deal, she thought, and asked for the price of the car. Unfortunately it was far too high, even with the 15% off. She thought the dealer had not been honest since he did not tell her the price upfront, only the discount.

Risk for disease and for treatment effects is conveyed in many ways: relative or absolute, in percentages, hazards, or odds ratios. Some are more informative than others, and many of the most frequently used are hard to understand. This article outlines how to convey benefits, harms, and burden of interventions to patients and society in an informative way, and offers pointers for communicating absolute and relative risks in consultation with patients, colleagues, and policy makers.