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st: RE: Data Setup for Survival Analysis With Unequal Interval

From   "Jesper Lindhardsen" <>
To   <>
Subject   st: RE: Data Setup for Survival Analysis With Unequal Interval
Date   Tue, 10 May 2011 17:26:28 +0200

Hi Peter

Yes, you can use multiple records per individual i.e. stset with more than one record per person. However, from my experience it really pays off to consult the manual (on stset) and also thoroughly check if the variables constructed by -stset- are consistent with what you expect.

Regarding 1) -stset- doesn't care if the time between the visits are off, but perhaps your interpretation of data does. You would have to conside what timespan these variables are relevant to. Before the visit, after the visis etc. Perhaps it makes most sense to crude categories, for example, high, low & normal bloodpressure.

2) I'm not sure I get this - it sound more like you have been provided a date of death ?? (I would presume the bloodpressure is quite low when the patient's passed away BTW ;-) )

BW Jesper

Jesper Lindhardsen
MD, PhD candidate
Department of Cardiovascular Research
Copenhagen University Hospital, Gentofte


-----Original Message-----
From: [] On Behalf Of TA Stat
Sent: 10 May 2011 16:59
Subject: st: Data Setup for Survival Analysis With Unequal Interval

Dear All

I would like to know the best way to run survival analysis (Cox PH
Model) in Stata (I am not sure I did it correctly) in a long format.
I also have a few points to discuss.

1.  The data is in a long format.  One row represents one hospital
visit.  Each visit we measured blood pressure and other lab tests
which will be time-varying covariates in Cox PH model.  However, the
time interval between hospital visits is not the same for each
patient.  Can Stata handle this?  I can calculate the numbers of days
or months from the first visit.  But I am not sure if I have to setup
the data in such a format that each visit is one or two months apart
for all patients.

2.  For the last visit, if the patient passed away, that patient won't
have a value of any time-varying covariates, would this effect the
analysis?  I am thinking about using missing data calculation to fill
in those values, but it doesn't make sense to me because the day that
patient passed away, those value such as systolic blood pressure
should be lower or higher than their normal level.


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