L6 - Cohort studies Flashcards
What is a cohort study?
A study which starts with disease free individuals, that have been exposed to something and then follows them to see if they develop the disease.
Can be prospective or retrospective.
What would be an ideal study?
A study in where only the exposure of interest was different between a case group and a control group, all other factors would be identical.
What is a longitudinal study?
A longitudinal study is an observational research method in which data is gathered for the same subjects repeatedly over a period of time.
Define person-years
The sum of the total time of everybody followed up in a study, e.g.
1 person followed up for ten years +
3 people followed up for 2 years + …
What type of analysis to you use for cohort studies?
IRR= (IR exposed)/(IR (unexposed)
What are the advantages of cohort studies over routinely available data?
- You can study exposures and personal characteristics that are not routinely collected
- You can obtain more detailed information on outcomes and exposures
- You can collect additional data on potential confounding factors
What is a prospective cohort study?
Recruit disease-free individuals and classify them according to their exposure status and then follow them up over a time period.
E.g. study starting now may begin collecting information and continue following-up until 2020.
What is a retrospective cohort study?
Recruit disease-free individuals and classify their exposure status and subsequent disease status USING HISTORICAL RECORDS.
E.g. study taking place now may go back and collect information from records 2000 onwards.
What is involved in the ‘follow-up’ in a cohort study?
Count person-years and disease status (outcome).
What can exposure data look like?
Binary (exposed or not exposed)
In several categories (number of cigarettes a day - up in 5)
Continuous
