Relative and Absolute Risk Reduction

These are measures to describe the efficacy of a new therapy compared to another therapy. The relative risk reduction describes the percentage by which the risk is reduced by an intervention. For example, a change in stroke frequency from 2% to 1.6% is a 20% change in relative risk. Important: This measure is often stated in professional advertising. However, it should be viewed critically, because the reader tends to overestimate the effect achieved. Absolute risk reduction refers to the absolute alteration of an event by an intervention or treatment, or by a behaviour related to all investigated persons. For example, a change in stroke frequency from 2% to 1.6% corresponds to a change in absolute risk of 0.4%.