Cohort Studies Flashcards
What is a cohort?
A group of people who share a “common experience”
What is a cohort study?
Follows a cohort over a period to see how their exposures affect their outcomes
Why would a cohort be chosen?
- the general population
- special exposure groups
- special resource groups
- geographically or facility-defined groups
How to design a cohort study?
Identify cohort
Assess exposure
Assess outcome
Interpret finding
What was the Framingham Heart Study?
The objective to study the impact of a range of factors on the incidence of Cardiovascular disease.
The population of 30-62 ages
High blood pressure increases risk of stroke
Diabetes associated with CVD.
What is the UK biobank?
Cohort study of ~500,000 middle aged adults in the general population in the UK
What are the key issues in cohort studies?
Measuring exposure
Assessing outcomes
Analysis
Strength and problems
When to choose cohort or case-control design
When to measure exposure?
May measure once at baseline
(recruitment to cohort) or repeatedly during follow-up
How to avoid bias when measuring disease?
Must be measured the same way between exposed and unexposed to avoid info bias
Those assessing should be blinded to avoid observer bias
How to measure disease?
Mortality
Hospital records
Primary care records
Population-based registries
How to calculate relative risk?
Incidence rate in exposed / incidence rate in unexposed
How to calculate incidence rate?
Number of new cases of disease diagnosed during follow-up / population-at-risk of developing disease during follow up.
What are the strengths of cohort studies?
Clear temporal relationship between exposure and disease
Eliminates recall bias
Studying rare exposures
Can study multiple outcome
Can study complex interactions
What are the potential challenges with cohort studies?
- Defining and measuring exposure and disease
- Loss to follow up over long
periods - Very expensive
- Very time consuming
- Logistically challenging
