cohort studies

Question 1

what are the basic things analytic epidemiology aims to do

Answer 1

Exposures and outcomes
* Causation
* Observational or intervention
study designs

Question 2

steps of a cohort study

Answer 2

1: identify a source population
2: recruit your sample of interest
3: Assess exposure to identify which group participants belong in (exposed or not exposed i.e. comparison)
4: follow up over time
5: observe who developed outcome
6: calculate data

Question 2

what is a key factor of people in the sample in cohort studies

Answer 2

*Sample population must not already have the outcome of interest

Question 2

what is a cohort study

Answer 2

individuals are defined on the basis of presence or absence of exposure to a suspected risk factor”

Question 2

whats the healthy worker effect

Answer 2

something a given type of worker is exposed to but the rest of the population in the study is not, in this situtation the comparison group must be carefully considered.
workers in the population also wont have same general exposures as other people as they are working so generally healthier than those not working.

Question 3

what is ideal about the source population, what can be exception to this

Answer 3

Ideal: random selection independent of exposure status
Sometimes: selection based on exposure status, (must consider appropriate comparison group)
If we want to study rare exposures or things that occur in particular people. In this case we select people based on the exposure status of this real thing. Ideally in all cases population gave both exposed and control group as we can make sure both groups differ very little, but do differ by exposure.

Question 3

what data can we use to interpret cohort studies

Answer 3

IP, IR, Relative risk and risk difference

Question 3

strengths of cohort studies

Answer 3

Determine temporal sequence between exposure and outcome
Can examine multiple outcomes from an exposure
Can calculate incidence (and therefore relative risk and risk difference)
Good for studying rare exposures

Question 3

what for people can change over time in the cohort studies

Answer 3

Have participants changed exposure status over time?
Ø Has everyone been followed up over the entire study?
Ø How long do participants need to be followed up?
have they developed the outcome

Question 3

what are the two types of cohort study

Answer 3

Prospective cohort studies
2. Historical cohort studies

Question 3

limitations of cohort studies

Answer 3

Loss to follow up, Potential for misclassification of exposures/outcomes
* Generally not good for studying rare outcomes
* Time consuming
* Can be expensive

Question 4

what can historical cohort studies also be called

Answer 4

retrospective cohort studies

Question 5

peoples exposures across the test change, how do we combat this

Answer 5

People may change their exposure over time. So at the start of the study they were one thing but they are now in a different group. To combat this issue the cohort studies will follow up frequently to detect change

Question 6

whats a prospective cohort study

Answer 6

They start at the start of time, when we define on the exposure status and then do follow ups to see what happens

Question 7

whats a historical cohort study

Answer 7

These start once exposure and outcome hhave occurred. They are done using data that was collected using previous records. They define the people on exposure and see of the people they defined, who got the outcome.

Question 8

benefits of historical cohort studies

Answer 8

So they don’t need to do follow ups in these as the follow ups have occurred.
They are faster and cheaper than the prospective. They are good for outcomes that take long times to develop.

Question 9

downfall of historical cohort studies

Answer 9

They use existing data that was collected for other reasons, this means the data may not be best quality and also may not have all the data the researchers wanted.
Because the outcome has occurred we may not know all relevant factors that led to that disease. There may also be bias on these historic studies.