Cohort studies are observational (no intervention) and longitudinal: they start from the exposure and follow participants over time to assess the outcome. They are the studies of risk measures — and of survival as well.
The cohort looks forward: from today’s exposure to tomorrow’s outcome.
Yes: if exposure data were recorded in the past, the cohort is historical (retrospective), keeping the exposure → outcome logic.
Relative risk, incidence and survival curves — direct measures of risk.
Loss to follow-up: patients who disappear may differ from those who stay, distorting the result.
Written by Francisco Tustumi, digestive system surgeon (FMUSP), associate editor of ABCD.
Developed by Surya MKT