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st: Stcox and time varying covariates

From   Garry Anderson <>
Subject   st: Stcox and time varying covariates
Date   Fri, 09 Jul 2010 19:08:49 +1000

Dear Statalist,

On page 186 of Cleves et al (2008) is "Let's instead pretend that the
drug is administered only once upon entry to the study and that its
level in the bloodstream decays at an exponential rate ..."

I have a dataset where there are multiple administrations of the drug
over time. The tvc and texp options of -stcox- allow the concentration
of a single administration of the drug to be calculated over time.

Can tvc() and texp() be used when there are multiple administrations of
the drug so that a time-varying concentration can be obtained?

Cleves MA, Gould WW, Gutierrez RG and Marchenko YU (2008) An
Introduction to Survival Analysis Using Stata.

Sylvestre MP and Abrahamowicz M (2009) Flexible modeling of the
cumulative effects of time-dependent exposures on the hazard. Statistics
in Medicine 28: 3437-3453

Best wishes, Garry
Garry Anderson
School of Veterinary Science
University of Melbourne
250 Princes Highway    Ph  03 9731 2221
WERRIBEE    3030       Fax 03 9731 2388


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