title: The incident user design in comparative effectiveness research.
abstract: Comparative effectiveness research includes cohort studies and registries of interventions. When investigators design such studies, how important is it to follow patients from the day they initiated treatment with the study interventions? Our article considers this question and related issues to start a dialogue on the value of the incident user design in comparative effectiveness research. By incident user design, we mean a study that sets the cohort's inception date according to patients' new use of an intervention. In contrast, most epidemiologic studies enroll patients who were currently or recently using an intervention when follow-up began. We take the incident user design as a reasonable default strategy because it reduces biases that can impact non-randomized studies, especially when investigators use healthcare databases. We review case studies where investigators have explored the consequences of designing a cohort study by restricting to incident users, but most of the discussion has been informed by expert opinion, not by systematic evidence.
authors.affiliation: The Center for Health Research, Kaiser Permanente, Portland, Oregon, USA. Eric.S.Johnson@kpchr.org
authors.forename: Eric S
authors.initials: ES
authors.lastname: Johnson
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Bartman
authors.forename: Becky A
authors.initials: BA
authors.lastname: Briesacher
authors.forename: Neil S
authors.initials: NS
authors.lastname: Fleming
authors.forename: Tobias
authors.initials: T
authors.lastname: Gerhard
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Kornegay
authors.forename: Parivash
authors.initials: P
authors.lastname: Nourjah
authors.forename: Brian
authors.initials: B
authors.lastname: Sauer
authors.forename: Glen T
authors.initials: GT
authors.lastname: Schumock
authors.forename: Art
authors.initials: A
authors.lastname: Sedrakyan
authors.forename: Til
authors.initials: T
authors.lastname: Stürmer
authors.forename: Suzanne L
authors.initials: SL
authors.lastname: West
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schneeweiss
mesh_terms: D015982:Bias; D015331:Cohort Studies; D057186:Comparative Effectiveness Research / Q000379:methods*; D006801:Humans; D017891:Pharmacoepidemiology / Q000379:methods*; D012107:Research Design; D013997:Time Factors