Study design
Cohort study
An observational study following people over time to compare outcomes by exposure or characteristic.
What it means
Definition
Cohort study. A cohort study can show whether outcomes occur more often after an exposure, and it can measure incidence over time. It remains observational unless exposure is assigned randomly.
What it can tell you
It can show how close the evidence is to a real human health outcome.
What it cannot tell you
It cannot prove that a treatment works in people unless human outcome data are available.
Headline trap
Why this matters in headlines
A cohort may find that sleep duration is associated with later disease, but confounding remains possible.