Found the following information:
- "Cohort studies are a type of medical research used to investigate the causes of disease, establishing links between risk factors and health outcomes. Cohort studies are usually forward-looking - that is, they are "prospective" studies, or planned in advance and carried out over a future period of time." [http://www.medicalnewstoday.com/articles/281703.php]
- "... it is an analysis of risk factors and follows a group of people who do not have the disease, and uses correlations to determine the absolute risk of subject contraction... Cohort studies are largely about the life histories of segments of populations, and the individual people who constitute these segments." [https://en.wikipedia.org/wiki/Cohort_study]
"Cohort" is a noun and refers to either an ancient Roman military unit or just a group of people. In this sentence however, it is specifically referring to a type of medical study.