Relative Risk Reduction
The percentage decrease in the risk of an event in the treatment group compared to the control group. For example, a relative risk reduction of 20% means the treatment reduced the risk by one-fifth compared to placebo. This measure can overstate the practical benefit when baseline risk is low.
Technical Context
RRR = (control event rate - treatment event rate) / control event rate × 100%. RRR is independent of baseline risk but can be misleading without absolute context. Example: RRR of 50% sounds impressive, but if the event rate decreases from 2% to 1% (ARR = 1%, NNT = 100), the clinical impact is modest. Conversely, RRR of 20% with baseline rate of 40% (ARR = 8%, NNT = 13) is clinically impactful. For GLP-1 RA cardiovascular trials, the ~20% MACE RRR translates to absolute risk reductions that depend on baseline cardiovascular risk of the population studied. Reporting both RRR and ARR (with NNT) provides the most complete picture of treatment benefit.