Statistics and risk
Number needed to treat
The number of people who need an intervention for one additional person to benefit.
What it means
Definition
Number needed to treat. Number needed to treat converts an absolute risk reduction into a practical clinical measure. Lower values usually indicate larger benefit, but the time period and outcome must be specified.
What it can tell you
It can help clarify what sort of evidence or claim is being discussed.
What it cannot tell you
It cannot, by itself, prove that the headline is accurate or clinically important.
Headline trap
Why this matters in headlines
An NNT of 50 over five years means 50 people receive the intervention for one additional person to avoid the stated outcome.