Evidence based medicine

Question 1

What is a cohort study ?

Answer 1

A cohort study is a particular form of longitudinal study, that samples a cohort (a group of people who share a defining characteristic) performing a cross-section at intervals through time.

In medicine, it is an analysis of risk factors and follows a group of people who typically do not have a given disease, and uses correlations to determine the absolute risk of subject contraction

Question 2

What are some of the key bits of information cohort studies can tell us ?

Answer 2

• The relative risk
• Absolute risk
• And odds ratio

Question 3

What is relative risk ?

Answer 3

• It is used to compare the risk in two different groups of people.
• e.g. smokers have a higher risk of developing heart disease than non-smokers

Question 4

What is absolute risk ?

Answer 4

• It is your risk of developing the disease over a time period
• e.g. you have a 1 in 10 change of developing a certain disease in your life

Question 5

How is the relative risk calculated ?

Answer 5

RR = incidence in those exposed/ incidence in those not exposed

Question 6

What is odds ratio ?

Answer 6

OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure.

Question 7

How is odds ratio calculated ?

Answer 7

OR = odds of event when exposed/ odds of event when unexposed