Advantages and Disadvantages of Case-Control Studies

Advantages and Disadvantages of Case-Control Studies

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Advantages:

• They are efficient for rare diseases or diseases with a long latency period between exposure and disease manifestation.
• They are less costly and less time-consuming; they are advantageous when exposure data is expensive or hard to obtain.
• They are advantageous when studying dynamic populations in which follow-up is difficult.

Disadvantages:

• They are subject to selection bias.
• They are inefficient for rare exposures.
• Information on exposure is subject to observation bias.
• They generally do not allow calculation of incidence (absolute risk).

 

Advantages & Disadvantages of Cohort Studies

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Advantages

Clarity of Temporal Sequence (Did the exposure precede the outcome?): Cohort studies more clearly indicate the temporal sequence between exposure and outcome, because in a cohort study, subjects are known to be disease-free at the beginning of the observation period when their exposure status is established. In case-control studies, one begins with diseased and non-diseased people and then acertains their prior exposures. This is a reasonable approach to establishing past exposures, but subjects may have difficulty remembering past exposures, and their recollection may be biased by having the outcome (recall bias).
Allow Calculation of Incidence: Cohort studies allow you to calculate the incidence of disease in exposure groups, so you can calculate:

·         Absolute risk (incidence)

·         Relative risk (risk ratio or rate ratio)

·         Risk difference

·         Attributable proportion (attributable risk %)

Facilitate Study of Rare Exposures: While a cohort design can be used to investigate common exposures (e.g., risk factors for cardiovascular disease and cancer in the Nurses' Health Study), they are particularly useful for evaluating the effects of rare or unusual exposures, because the investigators can make it a point to identify an adequate number of subjects who have an unusual exposure, e.g.,

·         Exposure to toxic chemicals (Agent Orange)

·         Adverse effects of drugs (e.g., thalidomide) or treatments (e.g., radiation treatments for ankylosing spondylitis)

·         Unusual occupational exposures (e.g., asbestos, or solvents in tire manufacturing, )

Allow Examination of Multiple Effects of a Single Exposure
Avoid Selection Bias at Enrollment

Disadvantages of Prospective Cohort Studies

1.    You may have to follow large numbers of subjects for a long time.

2.    They can be very expensive and time consuming.

3.    They are not good for rare diseases.

4.    They are not good for diseases with a long latency.

5.    Differential loss to follow up can introduce bias.

Disadvantages of Retrospective Cohort Studies

1.    As with prospective cohort studies, they are not good for very rare diseases.

2.    If one uses records that were not designed for the study, the available data may be of poor quality.

3.    There is frequently an absence of data on potential confounding factors if the data was recorded in the past.

4.    It may be difficult to identify an appropriate exposed cohort and an appropriate comparison group.

5.    Differential losses to follow up can also bias retrospective cohort studies.

 

References

1.    Song, J. and Chung, K. Observational Studies: Cohort and Case-Control Studies. Plastic and Reconstructive Surgery. 2010 Dec;126(6):2234-2242.

2.    Ury HK. Efficiency of case-control studies with multiple controls per case: Continuous or dichotomous data. Biometrics. 1975 Sep;31(3):643–649.

3.    von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP; STROBE Initiative. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet 2007 Oct;370(9596):1453-14577. PMID: 18064739.

4.    Boston University School of Public Health. Advantages and disadvantages of case-control studies; 2016 Sep. access 22/06/2019.

5.    Boston University School of Public Health. Advantages and disadvantages of cohort studies; 2016 Sep. access 22/06/2019.