Cohort Studies

Question 1

What is a cohort study?

Answer 1

Cohort studies fall under analytic epidemiology
They observe peoples exposures and what happens to them
Defines individuals on the basis on the presence or absence of exposure to a suspected risk factor

Question 2

What does a cohort study measure?

Answer 2

We can measure the onset of new cases of disease - the incidence of a disease, incidence proportion and incidence rate (measures of occurrence). We can also measure relative risk and risk difference (measures of association)

Question 3

How to use a cohort study

Answer 3

Identify source population, recruit sample population, assess exposure to identify which group participants belong in, follow up, observe whether or not participants develop outcome, calculate measures of occurrence and association

Question 4

Strengths of cohort study

Answer 4

Determines temporal sequence between exposure and outcome, examines multiple outcomes from an exposure, can calculate incidence, good for studying rare exposures

Question 5

Limitations of a cohort study

Answer 5

Loss of follow up, could lead to bias if related to the exposure and outcome
Potential for misclassifications of exposure/outcomes, not good for studying rate outcomes, time consuming, expensive

Question 6

What is a prospective cohort study?

Answer 6

In a prospective cohort study they classify exposure follow up over time and classify outcome, research begins with exposure

Question 7

What is a historical cohort study?

Answer 7

In a historical cohort study the exposure and outcome have already occurred, research starts after outcome, uses existing data, follow up period is reconstructed as outcome has already occurred

Question 8

Strengths and weakness of historical cohort studies

Answer 8

Less time consuming compared to prospective study, good outcome that take a long time to develop, less expensive, but uses existing data, quality?, may not know all relevant factors, could be bias