Cohort Study

Question 1

A cohort study is what kind of study?

Answer 1

Observational

Question 2

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

Answer 2

1. passive
2. naturally
3. unexposed

Question 3

Group allocation in cohort studies are based on _______ or _________

Answer 3

1. Exposure-status

2. Group membership (something in common)

Question 4

Cohort studies are useful when studying?

Answer 4

a rare exposure

Question 5

A cohort study can give then measure of association?

Answer 5

Risk Ratio (RR)

Question 6

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

Answer 6

(A+B) and (C+D)

Question 7

A _______ study may not always describe how groups are allocated

Answer 7

Cohort

Question 8

What are four reasons to select a cohort study design?

Answer 8

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

Question 9

What three fashions can a cohort study be conducted in?

Answer 9

1. Prospective
2. Retrospective
3. Ambidirectional

Question 10

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.

Answer 10

Prospective

Question 11

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.

Answer 11

Retrospective

Question 12

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

Answer 12

ambidirectional

Question 13

What is a cohort?

Answer 13

A group with something in common

Question 14

What are three examples of cohorts?

Answer 14

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

Question 15

What is an example of an inception cohort?

Answer 15

Framingham study

Question 16

What is a fixed cohort?

Answer 16

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

Question 17

What is a closed cohort?

Answer 17

A fixed cohort with no loss to follow up

Question 18

What is an open or dynamic cohort?

Answer 18

A cohort with new additions and loss to follow up

Question 19

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

Answer 19

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

Question 20

How do you select an unexposed study population?

Answer 20

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

Question 21

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

Answer 21

1.0

Question 22

What is an internal unexposed group?

Answer 22

Patients from the same cohort who are unexposed.

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

Question 23

What is a general population unexposed group?

Answer 23

Second Best Choice

Unexposed come from general population

Question 24

What is a comparison cohort unexposed group?

Answer 24

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

Question 25

What are the seven listed strengths of a cohort study?

Answer 25

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)

Question 26

What are the seven listed weaknesses of cohort studies?

Answer 26

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

Question 27

What are the five listed advantages of prospective cohort studies?

Answer 27

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

Question 28

What are the four listed disadvantages of prospective cohort studies?

Answer 28

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

Question 29

What must authors do with loss to follow up?

Answer 29

list them by group!

Question 30

Do ALL you can to limit ______?

Answer 30

loss to follow up

Question 31

Loss to follow ups increase what type of error?

Answer 31

Type 2

Question 32

What are the four listed advantages of retrospective cohort studies?

Answer 32

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

Question 33

What are the four listed disadvantages of Retrospective cohort studies?

Answer 33

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

Question 34

What is matching?

Answer 34

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

Question 35

What are the key biases with cohort studies?

Answer 35

Healthy-worker effect & selection bias

Question 36

What is healthy-worker effect

Answer 36

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

Question 37

What is selection bias?

Answer 37

How exposure status is defined/determined