Abstract #301063


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JSM 2002 Abstract #301063
Activity Number: 259
Type: Contributed
Date/Time: Tuesday, August 13, 2002 : 2:00 PM to 3:50 PM
Sponsor: Biometrics Section*
Abstract - #301063
Title: A Case Cohort Design for Assessing Covariate Effects in Longitudinal Studies
Author(s): Ruth Pfeiffer*+ and Louise Ryan and Matt Wand
Affiliation(s): National Cancer Institute and Harvard School of Public Health and Harvard School of Public Health
Address: 6120 Executive Boulevard, Bethesda, Maryland, 20892-7244, USA
Keywords: Correlated binary data ; Nested random effects model
Abstract:

We propose a case cohort design for longitudinal data as a cost-effective way to study the effects of covariates on repeated observations of rare binary outcomes. Our design entails choosing a random sub-cohort at the beginning of the study and following them repeatedly over time. Although some members in this sub-cohort may experience events over the study period, we refer to it as the "control cohort." The "case cohort," on the other hand, is a random sample of subjects not in the control cohort, who have experienced at least one event during the study period. This design is an extension of the case-cohort design (Prentice, 1986) and the bidirectional case-crossover design (Navidi, 1998). We illustrate it using data from a study of childhood asthma. The purpose of the study is to assess the role of immune function in impacting asthma risk directly, and in modifying the risk associated with various environmental exposures. Immune function is generally assessed through biomarkers. As the evaluation of biomarkers is expensive and labor-intensive, a cost effective sub-sampling strategy is very useful. The efficiency of our design is compared to a full cohort analysis.


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