KINE 3635 Chapter Cohort Studies: Reading - cohort studies
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Establishing the cohort: a cohort study is usually 100 or more in size, share common characteristics like birth year, or smokers, etc. The unexposed group should be representative of the exposed group on all factors except exposure. Cohort studies compare an exposed group to un exposed, to determine if the outcome of interest is associated with exposure: two types of cohort studies; prospective studies, and retrospective studies. Both studies are also referred to as longitudinal or follow-up studies. Following the cohort: the basic design of a cohort study from beginning of the study to end of follow- up. E = e(cid:454)posed, = (cid:374)ot e(cid:454)posed, d = diseased a(cid:374)d d = (cid:374)ot diseased. Evaluation of the results: risk (also called cumulative incidence or incidence proportion) = new occurrences of the outcome / population-at-risk at baseline, two risks can be compared to provide a risk ratio. (rr) The reference group is the unexposed cohort: the index group is the exposed cohort.