[R-meta] metafor-mota-analysis with between group moderator

[Matilde Vaghi]

Dear all,


I am using metafor to conduct a between group meta-analysis to test if
there is a difference between groups (controls vs. patients) on the
continuous independent variable y.


I need to check the influence of relevant moderator, in particular I obtain
a between group difference on the variable y and I want to check if the
finding remains significant after account for the effect of age (if the
difference in the independent variable y is still difference once adjusted
for age).


On the metafor manual, a clear example shows how to assess the effect of a
moderator (such as latitude) on the variable of interest. However, such
example refers to the presence of a study-level moderator (each study was
conducted at a different latitude, therefore one value is associated to
each study). In my case, each study have two values (i.e, mean age controls
and mean age patients). Therefore, it is not immediately clear how to adapt
the following


Rma(yi, vi, mods=cbind(Latitude), data=df)


for situations in which there is one moderator variable but two values
associated to it for each study. I tentatively computed a mean age per
study ((mean age controls for study 1+ mean age patients for study1)/2;
((mean age controls for study 2+ mean age patients for study2)/2 etc) to
have one value per study but I am not sure this is the best way forward.


Any advice would be highly appreciated. Many thanks and best wishes,

Matilde

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