What are cohort studies?

Cohort studies are longitudinal observational (non-intervention) studies in which exposure is used to assess the outcome.

In what kind of situation could we use the cohort study?

Cohort studies assess measures of risk.

For example, we would like to know whether fiber consumption decreases the risk of developing colorectal cancer. Thus, we can infer whether low fiber intake may be a causal factor for the development of colorectal cancer.

We selected patients with low fiber intake and compared them with patients with high fiber intake. After years of follow-up, we evaluated which patients developed colorectal cancer.

Cohort studies are commonly used to assess survival measures as well.

What is the advantage of carrying out the cohort study?

It is a good study design to develop causality hypotheses, namely, whether a certain exposure causes a certain disease.

What are the disadvantages of cohort studies?

We usually need a substantial sample size so that, after a long follow-up period, some develop the condition of interest. This issue can pose a difficulty when dealing with rare or infrequent diseases.

This text was written by:

Francisco Tustumi,

FMUSP Digestive System Surgeon

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