Hi Matthieu,
one option is to replace time with score in the model. That should be
straight forward.
The other option is to include score as a time-varying covariate. If
your score is not varying much across time and you are more interested
if the average score (or baseline score) affects atrophy rates, you can
also include is as a standard (fixed across time) co-variate (such as
baseline age) with a time (and a group etc) interaction.
Sorry, but I cannot do your design. Ultimately the model is the research
question that you are asking and it is important that this is done
correctly. Maybe there is a local biostats person that you can talk to?
Best, Martin
On 05/15/2017 08:20 PM, Matthieu Vanhoutte wrote:
Hi Martin,
Thank you. How should this variable be coded ? Should it be as age
covariate where age at baseline is used along all time points of each
subject ?
Could you provide me an example of design matrix, I don't manage to
see what does it look like to.
Best regards,
Matthieu
Le 14 mai 2017 8:08 PM, "Martin Reuter" <mreu...@nmr.mgh.harvard.edu
<mailto:mreu...@nmr.mgh.harvard.edu>> a écrit :
Hi Matthieu,
yes, that is possible. Instead of group, you use a variable for
your score (and interaction etc). Sometimes it may also makes
sense to use score instead of time.
Best, Martin
> On 12 May 2017, at 10:51, Matthieu Vanhoutte
<matthieuvanhou...@gmail.com <mailto:matthieuvanhou...@gmail.com>>
wrote:
>
> Dear Freesurfer's experts,
>
> I have searched through the mailing list but haven't found any
answer to my question.
>
> Is it possible with LME model to make correlations between for
example cortical thickness surface data and cognition scores along
time ? As it is possible to test for interaction of group X time,
is this also in the same way feasible to test for coognition score
X time on cortical thickness ?
>
> Many thanks for your advice !
>
> Best regards,
> Matthieu
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