JSM 2004 - Toronto

Abstract #301214

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Activity Number: 157
Type: Contributed
Date/Time: Monday, August 9, 2004 : 2:00 PM to 3:50 PM
Sponsor: ENAR
Abstract - #301214
Title: Comparing Treatments in a Longitudinal Study with Multiple Responses: The Effects of Bypass Surgery on Cognition
Author(s): Sarah J.E. Barry*+ and Scott L. Zeger and Guy M. McKhann
Companies: Johns Hopkins University and Johns Hopkins University and Johns Hopkins University
Address: 615 N. Wolfe St., Baltimore, MD, 21205,
Keywords: longitudinal ; multiple responses
Abstract:

In a study of the effects of coronary artery bypass graft (CABG) surgery on cognition, the response comprises 16 standardized results of neuropsychological tests. The study observes CABG patients and nonsurgical controls at baseline and 3, 12, and 36 months later. The scientific question is whether there is a decline in cognitive function in the CABG group relative to the controls. We compare and contrast three approaches. The first is the standard approach of summarizing the 16 NP tests into a single measure of cognition and then conducting standard longitudinal data analysis (LDA). The second is to fit an LDA model separately to each of the 16 NP tests and then to summarize the results. The final method is an hierarchical model that comprises random effects for both subjects and tests and directly estimates a mean (over tests) contrast of the time trends for the two groups. We contrast the methods in terms of statistical efficiency, ease of implementation and interpretation.

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