Evidence of White Matter Neuroinflammation in [ME/CFS]: A Diffusion-Based Neuroinflammation Imaging Study 2026 Yu et al

[jnmaciuch]

I mean that the estimate of what the slope would be if age were held constant could be wrong, the assessed impact of age on the signals could be wrong, as in not reflective of a true population effect.

It wouldn’t be adding any problems that weren’t already there in your participant selection. What adding age as a covariate allows you to do is:
1) start with an association between ME/CFS and the outcome variable on its own
2) determine whether or not that already existing association can be better explained by a confounder in your data.

Thats going to be the one and only use case of covariates in the vast majority of papers where it is employed.