[R-meta] Subgroup comparison for non-linear meta-regression

[Mustafa Kilickap]

Dear all,

I did a “non-linear” meta-regression for prevalence (proportion) on time variable (year) using a power function. The studies consist of information for male and female participants. I would like to assess
whether the non-linear fit was similar for male and female. In other words, I would like to

make a comparison for male and female. 

I think it is more appropriate to do a meta-regression including gender*time interaction, however, number of the studies is small. My questions are:

1) Is it acceptable just to compare the subgroups (as stated below) without using interaction term. If it is acceptable;

2)    Does metafor package has a command like “byvar” that makes a statistical comparison of two subgroups possible? If not,

2)    Is it appropriate to calculate z=(p1-p1)/sqrt(se1^2 +se2^2) and then p for a “non-linear” relationship?
 
Kind regards
Mustafa Kilickap