Cohort study is the observational study with the highest strength of causality demonstration, which is often used to test the etiological hypothesis and determine the risk factors of diseases. However, it often takes a lot of manpower, material and financial resources to carry out a cohort study, and it is time-consuming. At the same time, due to the long follow-up time, it is difficult to maintain the compliance of the study population, which is prone to loss to follow-up bias. In recent years, driven by network technology, a new type of cohort study design, e-cohort study, has gradually emerged, which is based on the network to recruit participants, follow up and collect data. Taking advantage of the wide coverage and high flexibility of the network, it provides a new strategy for improving the recruitment speed, participant participation and compliance of cohort study. This article summarizes the development history, current status, key points of design and implementation, advantages and challenges of e-cohort study, so as to help researchers to fully understand and apply this study design to solve practical clinical problems.
