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Mother and Child Health: Research Methods. G.J.Ebrahim Editor Journal of Tropical Pediatrics, Oxford University Press . Criteria to be fulfilled in Cohort Studies. Observation must take place over a meaningful period of time
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Mother and Child Health: Research Methods G.J.Ebrahim Editor Journal of Tropical Pediatrics, Oxford University Press.
Criteria to be fulfilled in Cohort Studies • Observation must take place over a meaningful period of time • All members of the cohort must be observed. Drop-outs distort the study.
Types of Cohort Present Future Past Concurrent Cohort Followed into future Assembled now Assembled from past records Historical Cohort Followed till now Exposure and outcome Retrospective Cohort
Direct calculation of incidence Time sequence can be established Different outcomes for one agent can be determined Large numbers to be measured over a long time Subclinical disease may escape diagnosis Advantages and Disadvantages of Cohort Studies Disadvantages Advantages
Analysis of Cohort Studies Exposed Time Diseased (n=39) Healthy n = 30 000 Not exposed Diseased (n=6) Healthy n = 60 000