Epidemiology: Advantages and disadvantages of cohort study

Advantages

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

Disadvantages

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

References:
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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