Illustrating the structures of bias from immortal time using directed acyclic graphs.

ABSTRACT:

Background

Immortal time is a period of follow-up during which death or the study outcome cannot occur by design. Bias from immortal time has been increasingly recognized in epidemiological studies. However, the fundamental causes and structures of bias from immortal time have not been explained systematically.

Methods

We use an example 'Does winning a Nobel Prize prolong lifespan?' for illustration. We illustrate how immortal time arises and present structures of bias from immortal time using directed acyclic graphs that specify time-varying variables. We further explore the structures of bias with the exclusion of immortal time and with the presence of competing risks. We discuss how these structures are shared by different study designs in pharmacoepidemiology and provide

SUBMITTER: Yang G 

PROVIDER: S-EPMC11706530 | biostudies-literature | 2024 Dec

REPOSITORIES: biostudies-literature