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Epi Exam Two > Cohort Study > Flashcards

Cohort Study Flashcards

1
Q

A cohort study is what kind of study?

A

Observational

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2
Q

Cohort studies allow a researcher to be a ____ observer of natural events occurring in ______-exposed and _______ grous.

A
  1. passive
  2. naturally
  3. unexposed
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3
Q

Group allocation in cohort studies are based on _______ or _________

A
  1. Exposure-status

2. Group membership (something in common)

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4
Q

Cohort studies are useful when studying?

A

a rare exposure

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5
Q

A cohort study can give then measure of association?

A

Risk Ratio (RR)

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6
Q

Which boxes in a 2x2 table does a cohort study give?

A

(A+B) and (C+D)

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7
Q

A _______ study may not always describe how groups are allocated

A

Cohort

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8
Q

What are four reasons to select a cohort study design?

A
  1. Unable to force group allocation (‘randomize’)
  2. Limited resources
  3. The exposure of interest is rare
  4. More interested in incidence rates or risks for outcome of interest
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9
Q

What three fashions can a cohort study be conducted in?

A
  1. Prospective
  2. Retrospective
  3. Ambidirectional
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10
Q

In this type of cohort study, an exposure group is selected on the basis of a past or current exposure and followed into the future to assess for outcomes of interest.

A

Prospective

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11
Q

In this type of cohort study the exposure and outcome of interest have already occurred, but groups are still allocated on past history of exposure.

A

Retrospective

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12
Q

This type of study uses a retrospective design but also adds future data collected on additional outcomes

A

ambidirectional

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13
Q

What is a cohort?

A

A group with something in common

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14
Q

What are three examples of cohorts?

A
  1. Birth cohort - being born in same region in a given time period
  2. Inception - based on some common factor
  3. Exposure cohort - based on some common exposure
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15
Q

What is an example of an inception cohort?

A

Framingham study

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16
Q

What is a fixed cohort?

A

A cohort that can’t gain members but can have loss to followup

17
Q

What is a closed cohort?

A

A fixed cohort with no loss to follow up

18
Q

What is an open or dynamic cohort?

A

A cohort with new additions and loss to follow up

19
Q

How do you select an exposed study group in a cohort study

A

Allocated subjects based on pre-defined criteria of exposure. (scientifically and consistently determined)

20
Q

How do you select an unexposed study population?

A

Make the groups as close as possible (coming from the same cohort yet not exposed.

21
Q

If exposure truly has no effect what will the RR be?

A

1.0

22
Q

What is an internal unexposed group?

A

Patients from the same cohort who are unexposed.

Best option if there are only levels of exposure, lowest level becomes baseline

23
Q

What is a general population unexposed group?

A

Second Best Choice

Unexposed come from general population

24
Q

What is a comparison cohort unexposed group?

A

least acceptable
An attempt to match different groups as close as possible
based on numerous personal characteristics

25
Q

What are the seven listed strengths of a cohort study?

A
  1. Good for assessing multiple outcomes of one exposure
  2. Useful when exposures are rare
  3. Useful in calculating risk and RR
  4. Less expensive than interventional trials
  5. Good when ethical issues limit use of interventional studies
  6. Good for long induction/latent periods (retrospective)
  7. Able to represent “Temporality” (prospective)
26
Q

What are the seven listed weaknesses of cohort studies?

A
  1. Cant demonstrate causation
  2. Hard to control for other exposures if more than one plausible for being associated with an outcome
  3. Retrospective; can’t control for other exposures or potential changes in amount of study-exposure
  4. Prospective; not good for long induction/latent periods
  5. Can be impacted by unassessed confounders
  6. Can be impacted by selection &recall biases
  7. Limited by available data; Retrospective
27
Q

What are the five listed advantages of prospective cohort studies?

A
  1. Can obtain study-important info from patients
  2. Tracking of patients is easier
  3. Better at answering temporality
  4. May look at multiple outcomes from a single exposure
  5. can calculate incidence and incidence rates
28
Q

What are the four listed disadvantages of prospective cohort studies?

A
  1. Time, expense, loss to follow up
  2. Not efficient for rare diseases
  3. Not suited for long induction/latency conditions
  4. Exposure may change over time
29
Q

What must authors do with loss to follow up?

A

list them by group!

30
Q

Do ALL you can to limit ______?

A

loss to follow up

31
Q

Loss to follow ups increase what type of error?

A

Type 2

32
Q

What are the four listed advantages of retrospective cohort studies?

A
  1. Best for induction/latency conditions
  2. Able to study rare exposures
  3. Useful if the data already exists
  4. Saves time and money in comparison to prospective
33
Q

What are the four listed disadvantages of Retrospective cohort studies?

A
  1. Requires extensive access to patient info that may not be available
  2. Info may not factor in or control for other harmful exposures
  3. Patients may not be available for interview
  4. Exposure may have changed over time
34
Q

What is matching?

A

A way to make groups as equal as possible on known cofounders.

35
Q

What are the key biases with cohort studies?

A

Healthy-worker effect & selection bias

36
Q

What is healthy-worker effect

A

If healthy you work, if too ill to work you may be unemployed and part of non-working gen pop

37
Q

What is selection bias?

A

How exposure status is defined/determined

Epi Exam Two (6 decks)

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