topic How to calculate survival time? in SAS Programming

How to calculate survival time?

nwang5 — Fri, 05 May 2023 16:22:13 GMT

Hi SAS community,

I hope you are doing well. When conducting survival analysis, I used two ways to define the endpoint of the study period:

1. Individuals who are diagnosed with depression during the study period can be defined as the endpoint.
2. Alternatively, individuals who do not have depression at the end of the study period can be defined as the endpoint.
I was wondering how I could calculate my survival time.

Thanks for all your help!

This is original data:

idauniq	depression	wave
100052	0	3
100052	0	4
100052	0	5
100052	0	6
100052	0	7
100052	0	8
100052	0	9
100055	0	3
100055	0	4
100055	0	5
100055	0	6
100055	0	7
100055	0	8
100057	0	3
100057	0	4
100057	0	5
100057	0	6
100057	0	7
100057	0	8
100057	0	9
100059	0	3
100059	0	4
100059	1	5
100061	0	3
100061	1	4
100061	0	5
100061	0	6
100068	0	3
100068	0	5
100068	0	6
100068	1	7
100080	0	3
100080	0	5
100081	0	3
100081	0	4
100081	0	5
100081	0	6
100081	1	7

This is results what is expect:

idauniq	depression	wave	Time	censor
100052	0	9	12	0
100055	0	8	10	0
100057	0	9	12	0
100059	1	5	4	1
100061	0	4	2	0
100068	1	7	8	1
100080	0	5	4	0
100081	1	7	8	1

Re: How to calculate survival time?

mkeintz — Fri, 05 May 2023 23:01:56 GMT

And what is the rule by which you calculate the TIME variable?

For instance, for ID 100052, you start with

idauniq	depression	wave
100052	0	3
100052	0	4
100052	0	5
100052	0	6
100052	0	7
100052	0	8
100052	0	9

From that you get

idauniq	depression	wave	Time	censor
100052	0	9	12	0

How did you get time=12?

Also, if an individual has depression=1 in a given wave, does that mean you will ignore subsequent waves for that individual? For instance, see

idauniq

depression

wave

100061	0	3
100061	1	4
100061	0	5
100061	0	6

Re: How to calculate survival time?

nwang5 — Sat, 06 May 2023 00:30:35 GMT

Thanks for your questions.
I am sorry that I did not mention that this study was conducted every two years. I started using wave 3. The time between wave3 to wave 4 is two years. (Wave9- wave3) *2=12

Yes, if an individual has depression=1 in a given wave, I will ignore subsequent waves for that individual.

Thanks!

Re: How to calculate survival time?

mkeintz — Sat, 06 May 2023 05:07:31 GMT

You can follow a SET statement with

  by idauniq ;

which allows you to determine if the observation-in-hand is the first (or last) obs for a given idauniq.

You will output one obs per idauniq. It will be either the last obs (if there are no preceding depression obs) or else the first obs with depressio=1:

data have;
  input idauniq	depression	wave;
datalines;
100052	0	3
100052	0	4
100052	0	5
100052	0	6
100052	0	7
100052	0	8
100052	0	9
100055	0	3
100055	0	4
100055	0	5
100055	0	6
100055	0	7
100055	0	8
100057	0	3
100057	0	4
100057	0	5
100057	0	6
100057	0	7
100057	0	8
100057	0	9
100059	0	3
100059	0	4
100059	1	5
100061	0	3
100061	1	4
100061	0	5
100061	0	6
100068	0	3
100068	0	5
100068	0	6
100068	1	7
100080	0	3
100080	0	5
100081	0	3
100081	0	4
100081	0	5
100081	0	6
100081	1	7
run;
data want (drop=n_dep);
  set have ;
  by idauniq ;
  if first.idauniq then n_dep=0;
  n_dep+depression;
  if (n_dep=1 and depression=1) or (n_dep=0 and last.idauniq=1);
  time=2*(wave-3);
run;