TYPES OF STUDIES EPIDEMIOLOGY

Question 1

What is a cohort study?

Answer 1

A study where individuals are defined according to the presence or absence of an exposure of interest

Question 2

What are the advantages of a cohort study?

Answer 2

• Determine temporal sequence between exposure + outcome
• Can examine multiple outcomes from an exposure
• Can calculate incidence (+ therefore relative risk + risk difference)
• Good for rare exposures

Question 3

What are the limitations of a cohort study?

Answer 3

• Loss to follow up – can lead to bias if related to exposure + outcome= bias -
• Potential for misclassification of exposures/outcomes
• Generally, not good for studying rare outcome
• Time consuming
• Can be expensive

Question 4

what types of study is cross sectional study?

Answer 4

• descriptive and observational

Question 5

what does cross-sectional study calculate?

Answer 5

prevalence

• the proportion of a defined population who have a disease a a given point in time

Question 6

what can the findings of cross-sectional study be used for?

Answer 6

• we don’t know if the exposure or outcome came first as they were both assessed at the same time so the findings can only be used for hypothesis generation.

Question 7

what are the strengths of cross sectional studies?

Answer 7

• assess multiple exposures and outcomes
• can be used to calculate prevalence, distribution of prevalence in population and hypothesis generation
• inexpensive and quick

Question 8

what are the limitations of cross-sectional study?

Answer 8

• no temporal sequence (exposure and outcome measured at same time)
• can’t measure incidence or measures of association
• not good for rare exposures/outcomes
• not good for assessing transient/variable exposures or outcomes (temporary)

Question 9

what type of study is an ecological study?

Answer 9

• descriptive and observational

Question 10

what are the strengths of ecological studies?

Answer 10

• can asses population level exposures
• considers hypotheses
• data usually already collected so less time consuming
• less expensive

Question 11

what are the limitations of ecological studies?

Answer 11

• doesn’t show causation
• no control for confounding
• ecological fallacy (20 year old isn’t 40)

Question 12

what does a measure of association do?

Answer 12

it quantifies the relationship between exposre/outcome among the two groups

Question 13

what does relative risk tell us?

Answer 13

tells us the strength of association
- how closely linked the exposure is to the outcome

Question 14

what type of study is a case control study?

Answer 14

analytic and observational

Question 15

how do case control studies work?

Answer 15

they work backwards
- start with participants with a known outcome status

Question 16

what are the strengths of a case control study?

Answer 16

• good for rare outcomes and transient exposures
• can assess multiple exposures
• temporal sequencing
• quick and inexpensive compared to other studies

Question 17

What are the limitations of a case control study?

Answer 17

• not good for multiple exposures
• difficult to select a quality control group
• susceptible to selection and recall bias

Question 18

What type of study is randomised control trial?

Answer 18

analytic and interventional

Question 19

what does RCTs measure?

Answer 19

similar to cohort, but instead of measuring exposure it randomises an intervention

Question 20

RCT Strengths?

Answer 20

• calculates measures of association
• calculates incidence
• strongest design for causal association
• strongest to account for confounding and bias

Question 21

RCT limitations

Answer 21

• expensive
• time consuming
• loss to follow up
• difficulty blinding
• non-adherance
• low generalizability