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Epidemiology: Advantages and disadvantages of cohort study


  • Incidence can be directly calculated
  • Direct estimation of the relative risk (RR)
  • More than one outcome of the risk factor can be studied
  • Dose response relationship with exposure can be studied
  • Temporal association of the exposure with the outcome can be seen
  • Certain biases like recall bias, interviewer’s bias are not a problem


  • The major disadvantage is the huge requirement for resources, viz. time, money and personnel
  • Unsuitable for rare diseases
  • Long periods of follow up needed
  • Attrition is a problem as long follow up is required
  • Ethical problems are more because as evidence of the RF accumulates, it becomes the duty of the investigator to educate those with the risk factor. Wait and watch may be unethical
  • Only one or a few risk factors can be studied.

Examples of cohort studies:

  • Smoking and lung carcinoma
  • Framingham heart study
  • Oral contraceptives and general health

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: