California Department of Public Health logo: three likenesses of people colored blue, green, and orange  
Last Edited: 6/2/2001

What is a cohort study?

A cohort study is an analytical study in which individuals with differing exposures to a suspected factor are identified and then observed for the occurrence of certain health effects over some period, commonly years rather than weeks or months. The occurrence rates of the disease of interest are measured and related to estimated exposure levels. Cohort studies can either be performed prospectively or retrospectively from historical records.