5.7: Types of Research Studies - Prospective or Longitudinal Studies
Cohort studies are often also referred to as longitudinal studies, and these are typically much more expensive and time consuming than other observational studies. In contrast to a case-control study which starts with the health outcome and then looks “backwards” in time for a risk factor, the cohort study starts by identifying risk factors - or exposures - in a group (or cohort) of people and then follows this group over time to see what health outcomes occur. Thus, cohort studies are typically prospective , which means tracking data forward in time with follow-up data collection on the same cohort. There are “retrospective” cohort studies, but these still begin with identifying exposures or risk factors from historical data in a particular group, and then following up with this group later on to determine outcomes (Celentano & Szklo, 2018). See Fig. \(\PageIndex{1}\) for a diagram of cohort or longitudinal studies.