Epidemiology

Question 1

What do cross-sectional studies provide information on?

Answer 1

The prevalence of disease(s) and/or exposure(s)
Associations between the disease and study factors
Can be descriptional or analytical

Question 2

What are case-control studies?

Answer 2

Individuals are classified by their disease status or outcome.
Cases - diseased
Controls - non diseased
Then past exposure to risk factor (or factors) of interest is measured for each group.
Analysis then aims to quantify the alteration in risk associated with each factor.

Question 3

What is a cohort/longitudinal study?

What are some advantages and disadvantages?

Answer 3

Study population is categorised as those that were exposed to the study factor and those that weren’t. Then compare measurement of outcome factors between both groups.
Pros: can calculate incidence, can study temporal relationships
Cons: takes longer, not good for rare disease

Question 4

What is a cross-sectional study?

What are the pros and cons?

Answer 4

Take a sample of the population. Measure risk factors and compare frequency of outcome (eg do brown dogs live longer-count no of brown dogs, look at ages upon death of brown vs non-brown dogs)
Pros: Quicker/cheaper, can estimate prevalence of outcome and exposures
Cons: Not good for rare diseases, can’t estimate incidence or study temporal relationships

Question 5

What are the pros and cons of case control studies?

Answer 5

Pros: good for rare diseases/long incubation, can look at existing records, smaller sample size-easier/cheaper
Cons: only assess 1 outcome, bias-selection, can’t calculate incidence/prevalence

Question 6

Which form of trial provides the strongest evidence and why?

Answer 6

Randomised controlled trial

Avoids selection, confounding and measurement biases