[R] time dependency of Cox regression

array chip arrayprofile at yahoo.com
Wed Nov 3 00:41:05 CET 2004


How can I specify a Cox proportional hazards model
with a covariate which i believe its strength on
survival changes/diminishes with time? The value of
the covariate was only recorded once at the beginning
of the study for each individual (e.g. at the
diagnosis of the disease), so I do not have the time
course data of the covariate for any given individual.
For example, I want to state at the end of the
analysis that the hazard ratio of the covariate is 6
at the beginning, decrease to 3 after 2 years and
decrease to 1.5 after 5 years.

Is this co-called time-dependent covariate? I guess
not, because it's really about the influence of the
covariate (which was measured once at the beginning)
on survival changing over time.

Thanks for any input.


More information about the R-help mailing list