Future-focused studies allow investigation of how the effects of exposures unfold over time and are influenced by other life events. A person's beliefs and understanding of the world evolves with age, and so a person may look back differently on an event from the way they experienced it at the time. Prospective collection of data in longitudinal studies, by contrast, can help minimise the risk of recall bias among research participants. They may favour retrospective designs because they can get quick answers from participant recall however, recall can be unreliable (especially over longer periods) and further, many types of observations (such as measurement of clinical measures or biomarkers) are not feasible in retrospective designs. Some may argue that retrospective studies can collect data on life history in a more economical way. Some may question why scientists undertake longitudinal research at all, when there are cheaper, faster designs for research studies. How do people live? How do we change as we grow? What happens as we get older? If an event or experience occurs during childhood, will it have an affect in later life, and how? These are some of the questions that longitudinal studies are intended to help address.

Longitudinal studies