[elcritch]

You could try and reduce the possible effect by controlling for disease severity. If it reduced the effect a large amount it'd strengthen the case that the effect is actually due to RA disease severity. Actually I'd be a bit surprised if the authors didn't do that for an observational study.

[carbocation]

Agreed. I didn't see it described in their methods, although it seemed that the main focus of this paper (based on length dedicated to the material) was the biological/model data rather than the EHR data.