In medical research, scholars use two types of data: prospective and retrospective. Prospective data refers to new data that is collected to answer a specific research question. When scholars use this data type, they first develop their study design and determine their sample, and then gather the data generated over the course of their study. Retrospective data is the data that already exists when researchers decided to conduct a study. So, retrospective data is not generated during the research but is collected from various sources, such as electronic health records. Both prospective and retrospective data have their advantages and disadvantages, which will be discussed in the present paper.
Prospective data can be used in both observational and interventional research. According to Jivraj et al. (2020), “prospective data comprise information collected before an outcome occurs and respondents are tracked longitudinally” (p. 208). Since prospective data is gathered as outcomes occur, its main advantage is that it can be tailored to answer a particular research question. However, because of the longitudinal research design, prospective studies may be long and expensive to conduct, and many participants may be lost to follow-up, which is especially true for rare outcomes (Alarkawi et al., 2018). Thus, using prospective data is not feasible for studying conditions with long latency periods (Alarkawi et al., 2018). Prospective data is also subject to the Hawthorne effect, which means that participants tend to change their behavior because they are aware of being observed (Alarkawi et al., 2018). Despite difficulties in collecting, prospective data is considered more reliable and is sometimes used to validate retrospective data. In addition, it is considered to be less susceptible to subject selection bias than retrospective data because neither researchers nor participants know about the outcomes because they have not occurred yet.
Unlike prospective data, retrospective data cannot be used in interventional research. The main advantage of retrospective data is that it allows for studying large samples and is convenient for assessing rare events at a low cost (Alarkawi et al., 2018). However, using readily available information from datasets means that researchers do not control the data collection process, so the necessary variables may be missing (Alarkawi et al., 2018). Furthermore, scholars have limited control over the quality of retrospective data. Databases may contain unreliable data, for example, because of coding errors (Alarkawi et al., 2018). Jivraj et al. (2020) state that, in addition to gathering information from databases, “retrospective data collection involves looking back in time by asking respondents to recall earlier life events and experiences after an outcome has occurred” (p. 208). In such cases, retrospective data is subject to recall errors when participants misremember or forget events from their past. Additionally, some data from the past, such as childhood circumstances, cannot be collected retrospectively because individuals may be unaware of them (Jivraj et al., 2020). Retrospective data may be biased if researchers select participants based on the outcome of interest.
To sum up, both prospective and retrospective data are valuable for medical research. Prospective data provides researchers with the exact information needed to answer a specific research question, and it is less subject to bias. However, prospective data collection is often time-consuming and costly, and participants are subject to the Hawthorne effect and high loss to follow-up. In contrast, retrospective data may lack some information necessary to answer a research question because scholars have limited control over the data collection process. For the same reason, the reliability of data should be carefully verified. Yet, retrospective data is especially helpful for conducting medical research with large sample sizes and allows for studying rare events at a relatively low cost.
References
Alarkawi, D., Ali, M. S., Bliuc, D., Center, J. R., & Prieto-Alhambra, D. (2018). The challenges and opportunities of pharmacoepidemiology in bone diseases. JBMR Plus, 2(4), 187–194.
Jivraj, S., Goodman, A., Ploubidis, G. B., & de Oliveira, C. (2020). Testing comparability between retrospective life history data and prospective birth cohort study data. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 75(1), 207–217.