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Epidemiology: Differences between Case – control and cohort study

Case – control study

  1. Proceeds from the outcome to cause
  2. Starts with cases of disease
  3. Tests if the suspected risk factor occurs more often in the cases than that in the controls
  4. Usually the first study for testing a hypothesis
  5. Requires fewer number of participants
  6. Yields the results relatively earlier
  7. Suitable for rare diseases
  8. Cannot directly estimate the relative risk hence calculates the ‘Odd’s ratio’ (OR)
  9. Only one outcome (disease) can be studied
  10. Inexpensive

Cohort study

  1. Proceeds from cause to outcome
  2. Starts with people exposed to the risk factor but free from the disease
  3. Tests if the disease occurs more frequently among those exposed as compared to those not similarly exposed
  4. Conducted for a more established hypothesis
  5. Involves larger number of participants
  6. Long follow ups lead to delayed results
  7. Not suitable for rare diseases
  8. Directly estimates the relative risk (RR)
  9. More than one outcome can be studied
  10. expensive

Tiwari P. Epidemiology Made Easy. New Delhi: Jaypee Brothers; 2003
Gordis, L. (2014). Epidemiology (Fifth edition.). Philadelphia, PA: Elsevier Saunders.
Bonita, R., Beaglehole, R., Kjellström, T., & World Health Organization. (2006). Basic epidemiology. Geneva: World Health Organization.
Schneider, Dona, Lilienfeld, David E (Eds.), 4th ed. Lilienfeld’s Foundations of Epidemiology. New York: Oxford University Press; 2015
K. Park. Principles of Epidemiology and Epidemiologic Methods. In Park’s Textbook of Preventive and Social Medicine. 24th Ed. Jabalpur: Banarasidas Bhanot, 2017: pg 58 – 145

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Steps in Investigation of an Epidemic:
Tests of Significance:
Monitoring and Evaluation:
Advantages and Disadvantages of Case Control Studies:
Advantages and disadvantages of cohort study:
Basic Concepts in Epidemiology:
Types of Epidemiological Studies:
Differences between Case – control and cohort study:
Uses of epidemiology:
Blinding in Experimental Studies:
Evaluation of a Screening Test: