At the population level, analysis of secondary data can be used to monitor secular trends, assess specific diseases or treatments, analyze health-care , and may serve as an important resource to inform policy decision-making. These data are quite useful as one can often draw conclusions about very large populations without expending the resources required by primary data collection. In addition, because sample sizes are often large, secondary data analysis is quite appropriate to study rare diseases or events.
Healthcare research may involve the analysis of “secondary data” referring to data collected by someone other than the user. Secondary data sources can be research or survey based but often they are the by-products of health-care providers' nonresearch activities. This includes administrative (billing) as well as clinical activities.