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COHORT STUDY BIAS - Coggle Diagram
COHORT STUDY BIAS
Selection bias
retrospective cohort studies
occurs when choice of population is related to exposure and outcome
occurs if completion, retention or loss of data are related to both exposure and outcome
minimisation
clearly defined population
correct choice of comparison group
exposed and unexposed groups should be identical!
selection of groups should be done without knowledge of outcome
not prospective??
subjects enrolled prior to disease/outcome
exposed population may be less likely to enrol
participants/investigators less influenced as no outcome yet
Loss to follow-up bias
prospective cohort studies
minimisation
maintain high follow-up rate!!!
enrol motivated population
use subjects who are easy to track
make data collection earsy
maintain participant interest
provide incentives!
short follow-up!
not retrospective???
there is no follow-up
using historical data
occurs when those actively participating in a study stop
results in over- or under-estimation of outcome/exposure association