[R] Multilevel Survival Analysis - Cox PH Model

[David Winsemius]

On Jul 1, 2011, at 10:22 AM, David Winsemius wrote:

>
> On Jul 1, 2011, at 10:10 AM, dunner wrote:
>
>> Hello all, thanks for your time and patience.
>>
>> I'm looking for a method in R to analyse the following data:
>>
>> Time to waking after anaesthetic for medical procedures repeated on  
>> the same
>> individual.
>>
>>> str(mysurv)
>> labelled [1:740, 1:2] 20  20  15  20  30+ 40+ 50  30  15  10  ...
>> - attr(*, "dimnames")=List of 2
>> ..$ : NULL
>> ..$ : chr [1:2] "time" "status"
>> - attr(*, "type")= chr "right"
>> - attr(*, "units")= chr "Day"
>> - attr(*, "time.label")= chr "ORIENTATION"
>> - attr(*, "event.label")= chr "FullyOrientated"
>>
>> mysurv is constructed from the following data:
>>
>> head(data.frame(MRN, ORIENTATION, FullyOrientated))
>>
>>      MRN ORIENTATION FullyOrientated
>> 1 0008291           20               2
>> 2 0008469           20               2
>> 3 0008469           15               2
>> 4 0010188           20               2
>> 5 0013664           30               1
>> 6 0014217           40               1
>>
>>
>> I had planned to use a Cox PH model to analyse time to waking  
>> (ORIENTATION =
>> 10, 15, 20 mins ....... 50 mins) and whether or not people (MRN)  
>> are fully
>> awake within an hour (FullyOrientated). I've put  GENDER, etc. into  
>> the
>> model but I have the following bias:
>>
>> The procedure is repeated weekly on each individual (MRN), so each
>> individual has 5-9 cases associated with them. Currently I am  
>> including
>> these in the model as if they were independent.
>>
>> Is there a way to account for the non-independence of these waking  
>> times?
>>
>> I'm thinking of something similar to the NLMER package and  
>> Multilevel /
>> Mixed Effects analysis as described in Pinheiro and Bates.
>
> Have you looked at the coxme package?

As an initial strata()-gem, as it were, perhaps just adding  
strata(MRN) may parcel out the intra-individual variability and  
degrees of freedom, so that they are not inappropriately included in  
the IV's. My initial suggestion of coxme may be overkill.

> -- 
>
> David Winsemius, MD
> West Hartford, CT
>
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David Winsemius, MD
West Hartford, CT