Statistics and risk
Prevalence
How common a condition is in a population at a given time.
What it means
Definition
Prevalence: Prevalence counts existing cases. It can rise because more people develop a condition, because people live longer with it, or because detection improves.
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
A headline about how many people have a condition is usually describing prevalence.