How do I plot the spline effect of a cox model by sex?

sseb — Wed, 23 Dec 2020 20:10:45 GMT

Hi,

I am attempting to create a plot of the hazard ratio vs. continuous exposure by sex.

I used code from LinusS (https://communities.sas.com/t5/SAS-Health-and-Science/How-do-I-plot-the-spline-effect-in-PHREG/m-p/626357#M2294) but don't know how to modify the estimate command to add sex-stratified results. Below is my code (for this example I just took LinusS's code and modified it a bit to add the parts I'm confused about).

The main change I made to LinusS's code (and the part that doesn't work) is:

estimate "&value. male" sex 0 bmis [-1, &ref] [1, &value] / exp cl;
estimate "&value. female" sex 1 bmis [-1, &ref] [1, &value] / exp cl;

But it's not working to produce sex-specific HRs.

Any help is greatly appreciated!

Sebastian

*running the model and outputting results;
proc phreg data=temp;
   effect bmiS = spline(bmi / basis=tpf(noint) NATURALCUBIC details knotmethod=list(18.0175 20.5289 22.4059 27.4693) );
   class sex (ref='F') / param=ref;
   model time*event(0) = bmiS|sex / rl=wald ties=EFRON ;
    store sasuser.coxr;
run;

*creating macro to estimate HR at each BMI value compared to reference at BMI=20, separately for males and females;
%macro est(ref=20, start=15, end=35, by=0.1);
   %Do i = 1 %To %eval(%SysFunc( Ceil( %SysEvalF( ( &End - &Start ) / &By ) ) ) +1) ;
      %Let value=%SysEvalF( ( &Start - &By ) + ( &By * &I ) ) ;
         estimate "&value. male" sex 0 bmis [-1, &ref] [1, &value] / exp cl;
         estimate "&value. female" sex 1 bmis [-1, &ref] [1, &value] / exp cl;
   %end;
%mend est;

*using the macro and outputting the results;
ods html select none;
ods rtf select none;

ods dataset Estimates=Estimates;
proc plm restore=sasuser.coxr;
   %est(ref=20, start=16, end=35, by=0.01);
run;

ods html select all;
ods rtf select all;

*making some changes to output to use in sgpanel;
data estimates;
    set estimates;
    BMI=substr(label, 1, 2)*1;
    sex=substr(reverse(label), 1, 1);
run;

proc sort data=estimates; 
   by sex; 
run;

*producing plots;
proc sgpanel data=estimates NOAUTOLEGEND;
   panelby sex;
   refline 1;
   Series y=ExpEstimate x=BMI;
   Series y=LowerExp x=BMI;
   Series y=UpperExp x=BMI;
run;

Re: How do I plot the spline effect of a cox model by sex?

ChrisNZ — Sat, 09 Jan 2021 08:31:07 GMT

Moved to Statistics community.

topic Re: How do I plot the spline effect of a cox model by sex? in Statistical Procedures

How do I plot the spline effect of a cox model by sex?

Re: How do I plot the spline effect of a cox model by sex?