Epidemiological study design Flashcards Preview

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Flashcards in Epidemiological study design Deck (14)
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1
Q

Give 6 types of study design

A

Cohort study, case-control, ecological, cross-sectional, RCT, meta-analysis

2
Q

describe the design of a cohort study

A

An observational study

Longitudinal study in similar groups but with different risk factors/treatments

Follow up over time (constantly checking in)

(in contrast to case-control, the outcome has not occurred yet)

3
Q

Describe case-control studies

A

An observational study looking at the cause of a disease. Compares similar participants w/ disease and those without (controls). Looks RETROSPECTIVELY for exposure/cause (potential RF data is collected - e.g. questionnaires)

The outcome has already occurred at the time of investigation

important idea: looks backwards in time

4
Q

describe ecological studies

A

Observational study of a disease or outcome and exposure of interest are measured in a number of populations/groups (e.g. between electoral wards or different hospitals)

5
Q

describe a cross-sectional study

A

Observational study collecting data from a population at a specific point in time (no follow-up) - a SNAPSHOT STUDY

Example: the census (conducted every 10 years) –> other examples include prevalence at a specific time (e.g. number of smokers in a GP practice)

6
Q

describe an RCT

A

Experimental study

Similar participants are randomly assigned to an intervention or control group to study effect of intervention

7
Q

What are the advantages and disadvantages of an RCT?

A

Advantages:

  • Low risk of bias and confounding
  • Comparative
  • randomised
  • blind - reduces possibility of information bias

Disadvantages:

  • High drop out rate
  • Ethical issues
  • Time consuming and expensive
  • prior knowledge required
8
Q

What are the advantages and disadvantages of an ecological study?

A

Advantages: can lookout geographical correlations, good for generating a hypothesis

Disadvantages:
- subject to bias + confounding

9
Q

What are the advantages and disadvantages of a cohort study?

A

Advantages:

  • Can follow up rare exposure
  • Allows to identify risk factors
  • Data on confounders collected prospectively

Disadvantages:

  • Large sample size required
  • Impractical for rare diseases
  • Expensive
  • People drop out
  • Confounding/bias
10
Q

What are the advantages and disadvantages of a case control study?

A

Advantages:

  • Quick
  • Good for rare outcomes

Disadvantages:

  • Difficult finding appropriately matched controls
  • Prone to selection and information bias (e.g. recall bias)
  • dropout
  • Reverse causality (as the outcome interest has already occurred)

n.b. all the observational studies (case control, ecological, cohort, cross-sectional) are subject to bias and confounding

11
Q

What are the advantages and disadvantages of a cross-sectional study?

A

Advantages:

  • Large sample size
  • Provides data on prevalence of risk factors and disease
  • Quick to carry out
  • Repeated studies show changes over time

Disadvantages:

  • Risk of reverse causality – which came first?
  • Less likely to include those who recover quickly or short recovery
  • Not useful for rare outcomes
  • subject to bias + confounding
  • Temporality: impossible to be certain whether an outcome developed before or after the exposure concerned
12
Q

What is a meta-analysis?

A

An evidence synthesis where all the data of similar studies are pooled together and a forest plot is created

13
Q

What is an ethical dilemma of RCTs?

A

is it ethical to withhold potentially life-saving treatment form the control group?

14
Q

Give an example of a cross-sectional study

A

Census