Comparing TDMARDs with nonuse or even with nonbiologic DMARDs is subject to severe bias due to confounding, as the decision to initiate treatment with TDMARDs in old age is likely influenced by RA activity and frailty, which cannot be fully measured with claims data.44 Some active comparators, for instance methotrexate, which was used in another recent study as a comparator to TNF inhibitors,45 are likely more appropriate than nonuser comparisons owing to improved confounding adjustment. Here, TNF is linked to rheumatoid arthritis.