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Re: st: Cox proportional hazard model

From   Nyasha Tirivayi <>
Subject   Re: st: Cox proportional hazard model
Date   Thu, 12 Aug 2010 23:31:40 +0200

Dear Michael

Thanks for the reference.

Answers to your questions

1. I can measure duration of AIDS medication prior to my study
2. I can observe the event for the patient and non-patient family members too
3. I have multiple observations (2)

I would like to look at the outcome for patients and also the
non-patient family members to check if there are any spillover effects
from the medication the patient is receiving- theory being AIDS
medication restores health to patient, helping them return to work,
and in turn could also help other family members to shift labour from
caring for the patient, to gainful employment. So I would like to have
separate cox regressions for the patients and non-patient family

So can I still assign the duration of AIDS medication (time variable)
to non-patient family members?

Kindly respond

Nyasha Tirivayi
Maastricht University

On Thu, Aug 12, 2010 at 11:04 PM, Michael McCulloch
<> wrote:
> Dear Nyasha,
> It seems your main outcome is time to employment, and your co-variates
> include:
>        # of non-patient household members living together with the patient
>        patient receiving AIDS medication (yes/no)
> Questions which also occur to me are:
>        can you measure duration of AIDS medication prior to start of
> observation in your study?
>        are you observing for the event (becoming employed) only for the AIDS
> patient or for any household member?
>        do you have multiple observations (in which case a time-dependent
> model can be built)?
> If the answer to that last question is yes, then a relevant paper may be:
> Fewell, Z., M. A. Hernan, et al. (2004). "Controlling for time-dependent
> confounding using marginal structural models." The Stata Journal 4(4):
> 402-20
> Michael McCulloch
> On Aug 12, 2010, at 12:32 PM, Nyasha Tirivayi wrote:
>> Hello
>> I would like to model  intrahousehold transitions from unemployment to
>> employment. In the household are:
>> 1. A patient receiving AIDS medication
>> 2. And non-patient household members living together with the patient.
>> I am thinking of applying the cox proportional hazard model, where
>> duration of AIDS medication is the time variable. How can  I analyse
>> the transitions by other non-patient family members, when they do not
>> receive AIDS medication? Do I assign the time variable to the patient
>> and his/her non-patient family members?
>> Kindly advise
>> Regards
>> Nyasha Tirivayi
>> Maastricht University
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> Best wishes,
> Michael McCulloch, LAc MPH PhD
> Pine Street Foundation
> 124 Pine Street
> San Anselmo, CA 94960-2674
> tel:    415-407-1357
> fax:    206-338-2391
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