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Cohort or
longitudinal studies represent another form of
analytic study that provides information on the relationship
between causal factors and injuries. In a cohort study, subjects
with an exposure to a causal factor are identified and the
incidence of injury over time is compared with that of controls
(persons who do not have the exposure). In a longitudinal study,
subjects are followed over time with continuous or repeated
monitoring of risk factors or health outcomes, or both.
One issue to consider in cohort studies is the frequency in
which the outcome occurs. Cohort studies are usually not
appropriate when the outcome is a rare event. The study subjects
would have to be followed up for long periods before sufficient
cases accrue to give statistically meaningful results.
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