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Re: st: Cox regression- non linear trends


From   Steven Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Cox regression- non linear trends
Date   Tue, 26 Jul 2011 08:45:30 -0400

Catherine,

-fracpoly- 

Steve
sjsamuels@gmail.com




On Jul 25, 2011, at 9:27 PM, Duggan, Catherine R wrote:

Hello

I have a Cox model  examining Variable A  and it's inhibitor  Var B.

Var. A seems to exhibit a non-linear trend when I examined the tertiles using a fully adjusted model, with mortality as an endpoint.  The P.H. assumption was met. 

1.00  ref
0.48 (95% CI 0.18-1.27)
0.97 (95% CI 0.35 - 2.67)

(Though Var B was linear). 


Because of this, I thought that I should present just the categorical variable in the model. However my experience has been that reviewers always want to see both continuous and categorical variables presented, especially as I will present  Var B both ways. 

Can anyone give me some advice please on how to handle non-linear continuous variables in Cox models?

Many thanks

Catherine





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