What is a cohort study
Getting 2 groups; an exposed and unexposed group and monitoring them over time to see if they develop the outcome of interest
What are the 2 types of cohort study
Prospective or reterospective
What are reterospective cohort studies
When the study was started in the past by looking at historical evidence of outcome free individuals to determine their exposure status
What can be calculated in a cohort study
- incidence risk ratio
- odds ratio
- relative risk
How do you work out the relative risk
Work out death of the 2 groups divided by person years
Then divide the 2 numbers with exposed on top
What is the absolute risk
The number of deaths per 1000 people per year
What are the advantages of cohort studies
- allow for detailed assessment of exposure, outcomes and con founders
- better for rare exposures, for studying a range of different outcomes
- better for conditions which fluctuate with age
What are the difference of cohort studies
- usually large and resource intensive
- takes a long time
- potential ethical dilemmas
- not good for rare outcomes
- difficulty with confounding
Is there much bias in cohort studies
No
What is the risk ratio
The prevalence proportion of outcome
