Cohort studies work well for rare exposures–you can specifically select people exposed to a certain factor.
But this design does not work for rare diseases–you would then need a large study group to find sufficient disease cases.
Why are cohort studies not good for rare diseases?
As with prospective cohort studies, they are not good for very rare diseases. If one uses records that were not designed for the study, the available data may be of poor quality. There is frequently an absence of data on potential confounding factors if the data was recorded in the past.
What are cohort studies good for?
Cohort studies are a type of medical research used to investigate the causes of disease and to establish links between risk factors and health outcomes. The word cohort means a group of people. These types of studies look at groups of people.
What are the strengths and weaknesses of cohort studies?
Strengths and weaknesses of cohort studiesMultiple outcomes can be measured for any one exposure. Can look at multiple exposures. Exposure is measured before the onset of disease (in prospective cohort studies). Good for measuring rare exposures, for example among different occupations.
What are the pros and cons of using a retrospective cohort study?
The advantages of retrospective cohort studies are that they are less expensive to perform than cohort studies and they can be performed immediately because they are retrospective. Also due to this latter aspect, their limitation is: poor control over the exposure factor, covariates, and potential confounders.