8440.04/5-Cohort Studies & Case Control Studies

Question 1

What are the different types of cohort studies?

Answer 1

• Retrospective
• Prospective
• Ambi-directional

Question 2

What is a Retrospective Cohort Study

Answer 2

Both exposure and disease have occurred at start of study

Question 3

What is prospective cohort study

Answer 3

• Exposure has occurred
  
  • disease has not occurred

Question 4

What is an ambi-directional cohort study

Answer 4

• elements of both retrospective and prospective

Question 5

What study design is similar to a prospective cohort study?

Answer 5

• Randomized clinical trial

Question 6

How do you choose b/w a retrospective vs prospective design?

Answer 6

• Retrospective
  
  • cheaper, faster
  • efficient w/diseases w/long lateral periods
  • exposure data might be inadequate
• Prospective study
  
  • more expensive, time consuming
  • not efficient for diseases w/long latent periods
  • Better exposure & confounder data
  • less vulnerable to bias

Question 7

What are the strengths of cohort studies?

Answer 7

• Efficient for:
  
  • rare exposures
  • diseases w/long induction and latent period
• Can evaluate multiple effects of an exposure
• if prospective
  
  • good info on exposures
  • less vulnerable to bias
  • clean temporal relationship b/w exposure and disease

Question 8

What are the weakness of cohort studies?

Answer 8

• inefficient for rare outcomes
• if retrospective
  
  • poor info on exposure and other key variables
  • more vulnerable to bias
• If prospective
  
  • expensive & time consuming
  • inefficient for diseases w/long induction & latent period

Question 9

What is the difference b/w cohort and case-control study?

Answer 9

• Cohort
  
  • subjects are grouped by exposure
  • compare incidence
• Case-Control
  
  • Subjects grouped by disease status
  • Compare odds of exposure

Question 10

Characterize case-control study

Answer 10

• Is retrospective bc disease or outcome has already occurred by start of study
• not measuring and comparing incidence
  
  • instead likelihood of having had the exposure
• measured as odds of exposure
  
  • groups are compared by odds ratio

Question 11

How is case-control study different from a retrospective cohort study?

Answer 11

• Designs differ based on grouping
  
  • Case-control studies: Grouped by the outcome/disease
    
    • perio disease vs noperio disease
    • cancer vs no cancer
  • FINISH

Question 12

How do you calculate odds ratio?

Answer 12

• odds ratio=(ad/bc)
  
  • estimate of relative risk if the outcome is uncommon

Question 13

What are the advantages of case control studies?

Answer 13

• Good for rare diseases
• Good for diseases w/long latency period
• efficient cost & time

Question 14

What are the disadvantages of case control studies?

Answer 14

• Subject to bias:
  
  • selection bias
  • misclassification bias
  • recall bias
  • interview bias
• Can’t calculate Incidence
• Temporal relationship b/w exposure and disease might be unclear

Question 15

What are the main epidemiological study designs for testing hypotheses?

Answer 15

• Cohort Study
• Experimental study (randomized control trial)
• Case-control study