Lecture 19 - Cohort Studies Flashcards Preview

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Flashcards in Lecture 19 - Cohort Studies Deck (14)
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What is the more common type of cohort study?

-observational study where individuals are grouped based from exposure status
-useful for rare exposures
-generates a risk ratio


What type of ratio is a cohort study most useful in generating?

-risk ratio


What is the type of cohort study that is not based on initial group allocation?

-starts with a “cohort” of people that have something in common
-initial grouping can be with regards to either exposure OR disease status


Differentiate between prospective, retrospective, and ambidirectional cohort study designs.

-separate by exposure status and then follow groups to assess for outcomes

-exposure status and disease status are already known
-groups are separated by exposure status and then assessed looked at for disease status

-uses retrospective design but then follows groups for further data


What are examples of different types of cohorts?

Birth cohort:
-commonality of being born in the same region around the same time

Inception cohort:
-common factor such as where people live or work

Exposure cohort:
-common exposure


What ways do membership in cohort studies change over time?

(Slide 22)

-can’t gain members but can lose them to follow up

-can’t gain members and does not lose members to follow up

Open (Dynamic):
-can gain and lose members


What sources are available to pick unexposed individuals from?

Internal (best):
-from the same “cohort” as exposed but are not exposed themselves
-could also be the least exposed if there is nobody unexposed in the cohort

General population:
-unexposed or least exposed from the general population the exposed were taken from

Comparison (worst):
-match unexposed with exposed based off personal characteristics
-doesn’t control for other variable which may cause disease


What are strengths of cohort studies? (6)

-good for assessing multiple outcomes of one exposure
-useful for rare exposures
-useful for producing risk ratios
-less expensive than interventional
-good for long induction/latency periods (retrospective)
-can represent temporality (prospective)


What are some weaknesses of cohort studies? (6)

-can’t demonstrate causation
-difficult to control for other exposures or changes in exposure (primarily retrospective)
-not good for long induction/latent periods (prospective)
-can be impacted by unexpected confounders
-can be impacted by biases
-limited by available data


What are advantages of prospective cohort studies? (5)

(Slide 30)

-more control over data collection process
-follow-up is easier
-better answers temporality
-can look at multiple outcomes from a single exposure
-can produce incidence rates


What are disadvantages of prospective cohort studies? (6)

(Slide 31)

-time consuming
-lost to follow up
-not useful for rare diseases
-not suitable for long induction/latency periods
-degree of exposure can change (not controlled for)


What are advantages of retrospective cohort studies? (4)

(Slide 33)

-useful for long induction/latency periods
-useful in rare diseases
-useful if data is already collected
-less expensive and time consuming (compared to prospective)


What are the disadvantages of a retrospective cohort study? (5)

(Slide 34)

-requires access to data
-resources might not contain all desired information
-no control for other exposures
-can be difficult to follow-up on patients
-exposure may have changed


What are common biases with cohort studies?

(Slide 36)

-healthy worker bias
-selection bias