Observational Studies in CVD Flashcards
What is a cross sectional study?
A study of a sample population at one point in time that provides a descriptive output, particularly prevalence. It is cheap and easy but only provides weak evidence for causality.
What is a case control study?
An analytical study that compares previous exposure between cases and controls. Controls are matched with cases. Retrospective - point of recruitment is after outcome of interest.
What is the main advantage of case control studies?
Can study rare diseases
What is the output of a case control study?
Odds ratio - an approximation of relative risk
What is an odds ratio?
(people with disease who were exposed/people without the disease who were exposed)/(people with the disease who weren’t exposed/people without the diease who weren’t exposed)
What does an odds ratio of 2 mean?
That the exposure doubles the likelihood of the outcome
What is a cohort study?
A longitudinal study that collects incidence data and compares outcomes between subgroups who were exposed to a risk factor and subgroups who were not
What is the outcome of cohort studies?
Relative risks
What is a prospective cohort study?
The study starts after exposure but before the outcome occurs
What is a retrospective cohort study?
The study starts after exposure and outcome occur
What is the benefit of a cohort study?
Can look at multiple outcomes and exposures
What are the difficulties of a cohort study?
it is difficult to study rare outcomes, it is expensive and difficult
What is active outcome ascertainment?
explicitly undertaking surveillance for outcome
What is passive outcome ascertainment?
database linkage done retrospectively
What is bias?
A systematic difference between or among groups that leads to an under or over estimation of true results
