What are Cohort studies?
A cohort study is an epidemiological study design called an observational study. Observational studies differ from experimental studies in that the researcher does not control the assignment of people to groups. Instead the groups are ‘observed’. Unlike experimental studies, observational studies do not look at the effectiveness of an intervention. A cohort study is an analytical observation study, i.e. it has a comparsion (control) group. Cohort studies follow up two or more groups from exposure to outcome. They compare the experience of one group exposed to a factor (exposed group) with that of the other which was not exposed to the factor (control group). If the exposed group has a higher or lower frequency of an outcome than the unexposed, than an association between exposure and outcome is evident. Cohorts look at causes and natural history of diseases and are also useful for examining prognosis of people who already have the disease. In a cohort study, precise choice of cohort de
