Increasing efficiency from censored survival data by using random effects to model longitudinal covariates.

Important note: Information in this article was accurate in 1998. The state of the art may have changed since the publication date.

Increasing efficiency from censored survival data by using random effects to model longitudinal covariates.

Stat Methods Med Res. 1998 Mar;7(1):28-48. Unique Identifier : AIDSLINE MED/98194459
Hogan JW; Laird NM; Center for Statistical Sciences, Brown University, Providence, RI; 02912, USA. jhogan@stat.brown.edu

Abstract: When estimating a survival time distribution, the loss of information due to right censoring results in a loss of efficiency in the estimator. In many circumstances, however, repeated measurements on a longitudinal process which is associated with survival time are made throughout the observation time, and these measurements may be used to recover information lost to censoring. For example, patients in an AIDS clinical trial may be measured at regular intervals on CD4 count and viral load. We describe a model for the joint distribution of a survival time and a repeated measures process. The joint distribution is specified by linking the survival time to subject-specific random effects characterizing the repeated measures, and is similar in form to the pattern mixture model for multivariate data with nonignorable nonresponse. We also describe an estimator of survival derived from this model. We apply the methods to a long-term AIDS clinical trial, and study properties of the survival estimator. Monte Carlo simulation is used to estimate gains in efficiency when the survival time is related to the location and scale of the random effects distribution. Under relatively light censoring (20%), the methods yield a modest gain in efficiency for estimating three-year survival in the AIDS clinical trial. Our simulation study, which mimics characteristics of the clinical trial, indicates that much larger gains in efficiency can be realized under heavier censoring or with studies designed for long term follow up on survival.

Keywords: *Models, Statistical *Survival Analysis
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