When a headline says 'cuts risk by 30%', what does that number actually mean?
Updated: 2026-09-09 · Safety and evidence
Short answer
A 30% figure is usually a relative reduction: it compares two groups with each other. If risk went from 2% to 1.4%, that is a 30% relative reduction and a 0.6 percentage-point absolute one. Both numbers are true, but the absolute one tells you how much actually changes. A relative figure alone is missing context.
In plain English
- Relative: how much one group changed compared with the other, as a percentage.
- Absolute: how many percentage points really changed.
- Check what was measured too: a lab marker is not the same as a clinical event.
- And check who it was measured in: the study population may not resemble you.
What we know
- The distinction between relative and absolute measures is well established in epidemiology.
- Headlines lean on the relative figure because it sounds larger.
What we don't know yet
- A relative percentage alone cannot give you the absolute benefit; you need the baseline.
- Results on intermediate markers do not guarantee clinical benefit.