Longitudinal study

A longitudinal study follows participants prospectively over time with continuous or repeated monitoring of risk factors or health outcomes, or both. The length and size of a longitudinal study varies greatly depending on how quickly a health outcome may be expected to occur and how common the health outcome may be.

The simplest design includes prospectively following a sample of participants who were exposed to a risk factor or have genetic change increasing their risk of developing a disease and a similarly-sized sample of controls, who were not exposed or do not have the genetic risk factor.

Sourced From
Epidemiology for the Uninitiated: Longitudinal studies (British Medical Journal)