[Basic principles, design elements, advantages and challenges of emulated target trial]

Cohort studies have unique advantages such as good representation of subjects, large sample size, and long follow-up time, but the difficulty in controlling confounders is the main obstacle to their insufficient causal inference. On the contrary, randomized controlled trial (RCT) research has absolute advantages in controlling confounding factors, but human, material, and ethical aspects limit its organizational implementation. With the accumulation of real-world cohort research data in recent years, emulated target trial (ETT) following the design principles of RCT research in large cohort studies has attracted more attention. ETT research based on cohort data produces more accurate research conclusions and provides new ideas for real-world cohort data analysis. This paper aims to introduce the basic principles, design elements, and advantages and challenges of ETT research to provide a reference for medical researchers to carry out ETT.