1. Allow complete information on the subject’s exposure, including quality control of data, and experience thereafter.
2. Provide a clear temporal sequence of exposure and disease.
3. Give an opportunity to study multiple outcomes related to a specific exposure.
4. Permit calculation of incidence rates (absolute risk) as well as relative risk.
5. Methodology and results are easily understood by nonepidemiologists.
6. Enable the study of relatively rare exposures.
1. Not suited for the study of rare diseases because a large number of subjects are required.
2. Not suited when the time between exposure and disease manifestation is very long, although this can be overcome in historical cohort studies.
3. Exposure patterns, for example, the composition of oral contraceptives, may change during the course of the study and make the results irrelevant.
4. Maintaining high rates of follow-up can be difficult.
5. Expensive to carry out because a large number of subjects are usually required.
6. Baseline data may be sparse because the large number of subjects does not allow for long interviews.
1. Permit the study of rare diseases.
2. Permit the study of diseases with long latency between exposure and manifestation.
3. Can be launched and conducted over relatively short time periods.
4. Relatively inexpensive as compared to cohort studies.
5. Can study multiple potential causes of disease.
1. Information on exposure and past history is primarily based on interview and may be subject to recall bias.
2. Validation of information on exposure is difficult, or incomplete, or even impossible.
3. By definition, concerned with one disease only.
4. Cannot usually provide information on incidence rates of disease.
5. Generally incomplete control of extraneous variables.
6. Choice of appropriate control group may be difficult.
7. Methodology may be hard to comprehend for nonepidemiologists, and correct interpretation of results may be difficult.