Definition - What does Retrospective Study mean?
A retrospective study is a study that compares two groups of people—a case group and a control group—in order to learn something about the case group. Both groups are similar, except that everyone in the case group has the attribute that is being investigated, and everyone in the control group does not.
They are commonly used in occupational epidemiology studies that look to figure out what factors are associated with specific occupational injuries or illnesses. Retrospective studies require researchers to investigate the history of the people in both groups in order to determine if there are any significant differences between them, which may explain why the case group experienced a specific injury/illness and the control group did not.
Safeopedia explains Retrospective Study
Retrospective studies are so-named because they involve looking backwards at the histories of the people being studied, rather than monitoring a group of people over an extended period (a prospective study). For example, a retrospective study of breast cancer patients would involve comparing a group of people with breast cancer to a similar group of people without breast cancer, while a prospective study would involve recruiting a single group of people without breast cancer and monitoring them for an extended period in order to try and discover insights into why some of them developed breast cancer during the study.
Retrospective studies have both benefits and drawbacks. One benefit is that they allow researchers to select the desired number of people with the condition they are studying, which means that the overall number of people in the study can be significantly less than in a prospective study, and are quicker to complete. This makes them useful for conducting research into conditions that would be too resource-intensive to study using prospective methods.
Many important studies into occupational hazards have been retrospective studies. For example, retrospective studies into military veterans with cancer were able to provide information into how exposure to the toxic herbicide Agent Orange was causally linked to increased incidence of cancer amongst exposed U.S. veterans.
This type of study can also be used to investigate the effectiveness of various safety practices. If employees at two workplaces in the same industry have different health outcomes, an occupational epidemiologist may be able to review differences in their safety practices in order to investigate whether a specific difference in practices is responsible for the associated difference in health outcomes.