Epidemiology Flashcards

1
Q

Name three advantages and disadvantages of case control studies.

A

Time efficient, efficient for rare or long latency diseases, several exposure assessment.
Not efficient for rare exposures, retrospective recall bias, difficult to temporally clarify.

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2
Q

What is advantageous in cohort studies.

A

rare exposures, multiple effects of SAME exposures, examine causality, direct estimate of risk.
Fill out questionnaire then follow you.

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3
Q

Why are cohort studies sometimes not suitable?

A

expensive, unsuitable for rare disease, time, difficult to interpret if loss to follow up is high.

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4
Q

What three types of populations are used in studies?

A

Target (want to make inferences about them)
Source (study population drawn from here)
Study (serve as study participants)

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5
Q

What is validity and how do internal and external validity differ?

A
Validity = lack of bias
Internal = validity of inferences as they pertain to members of the source population. 
External = validity as they pertain to members outside the population.
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6
Q

What are self selection and diagnostic bias?

A

Self-selection = (healthy worker effect) - survey respondents allowed to decide whether to participate.

Diagnostic = Outcome more likely to be ascertained as consequence of a particular exposure. (e.g. doctors aware of a relationship).

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7
Q

What is recall bias?

A

A problem in case control studies when cases recall past exposures differently than controls.
Cases and controls must have same recall period.

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8
Q

What is confounding?

A

Apparent effect of exposure of interest distorted due to effect of extraneous factor (confounder) being mistaken or mixed with actual exposure (which may be null) –> bias.

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9
Q

What are the criteria for confounding factors?

A
  • Must be a risk factor for disease.
  • Must be associated with EXPOSURE under study in the source population.
  • Must not be affected by exposure or disease. (can’t be be an INTERMEDIATE FACTOR).
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