LECTURE 12 COHORT

what is an observational study?

investigator simply observes exposure and disease status of each participant

what are the 3 common observational studies?

1. cohort studies

2. case-control studies

3. cross-sectional studies

what is a cohort?

group of people with a common characterisitc within a time period

what is a cohort study?

follow a cohort over time to see if there is an association between an exposure and an outcome

how are cohort studies and experimental studies different?

in cohort, investigator does not decide who was exposed and not exposed. they are placed in groups based on exposure/non-expsoure

what does the group with exposure become?

exposure group

what does the group without exposure become

comparison (control) group

is a cohort study looking at incidence or prevelance?

incidence: looking at new diseases over time

how do you calculate cohort proprotions?

A/A+B and C/C+D. then divide those proprtions to get risk ratio

what are the biggest issues with cohort studies?

takes a long time to complete

what is the most important epi study?

framignham, cardiovascular study

is the framingham study prospective or retrosepctive?

prospective

what are advantages of cohort studies?

can determine incidence,

good for rare exposures,

look for multiple outcomes from 1 exposure,

can look back at multiple exposures depending on outcome and structure

what are the disadvantages to cohort studies?

time consuming

expensive

bias

not useful for rare diseases

loss of follow-up due to time