title: Understanding immortal time bias in observational cohort studies.
authors.forename: A M-H
authors.initials: AM
authors.lastname: Ho
authors.forename: P W
authors.initials: PW
authors.lastname: Dion
authors.forename: C S H
authors.initials: CS
authors.lastname: Ng
authors.forename: M K
authors.initials: MK
authors.lastname: Karmakar
mesh_terms: D015982:Bias; D015331:Cohort Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D019370:Observation / Q000379:methods; D016016:Proportional Hazards Models; D016019:Survival Analysis; D013995:Time