Table 1.

Comparison between cohort studies and target trial emulation

	Cohort study	Target trial emulation	Random controlled trials
Characteristics
Study type	observational	both	experimental
Sample Size	large	either	small
Representativeness	high	medium	low
Confounding factors	more	some	less
Follow-up time	long	either	short
Dias risks	high	medium	low
Evidence quality	low	medium	high
To real world	near	near	far
Statistical analysis	Cox proportional-hazards model or mixed models	flexible, G methods, standard methods for observational data
Strengths	reliable causality wide applications multiple outcome analysis	cost-efficiency reduce self-inflicted biases informative to patient care: by describing the target trial population, treatment strategies, follow-up time, and outcome, investigators clarify when and how their results might be informative to patient care
Limitations	time-consuming and costly loss to follow-up control confounding factors	lack of randomization: observational data inherently lack randomization, requiring an assumption that treatment strategies can be compared as if they were randomized restriction to pragmatic trials: certain features of highly controlled trials (e.g., blinded treatment assignment) cannot be replicated using observational data inability to study novel treatments: investigators can only consider treatment strategies used in practice and captured in observational data
Key points	clear temporal sequence and etiological exploration	explicitly defined target trial protocol (time zero)