Examining the potential direct cardiovascular benefit of tumor-necrosis factor inhibitor in rheumatoid arthritis: Natural and controlled direct effect analyses.

Abstract

Tumor necrosis factor inhibitors (TNFi) may have a direct benefit on cardiovascular (CV) disease beyond reducing rheumatoid arthritis (RA) disease activity measured by the Clinical Disease Activity Index (CDAI). We compared TNFi initiators and methotrexate (MTX) monotherapy initiators from the CorEvitas RA registry. Two approaches to the "direct effect" of TNFi beyond CDAI were used. In the natural direct effect (NDE) analysis, the potential CV benefit of TNFi was partitioned into NDE and the natural indirect effect (NIE) mediated by CDAI during the first 6 months. We also estimated the controlled direct effects (CDE), corresponding to the direct benefit of TNFi when CDAI trajectories were hypothetically equalized between the initiators of TNFi and MTX monotherapy at a constant value. Estimates were given on the hazard ratio scale. We identified 5764 initiators of TNFi and 3588 initiators of MTX monotherapy. TNFi initiators were younger (58 vs. 64 years) with a shorter disease duration. Our total effect estimates (TNFi vs. MTX [reference]) were protective in direction (0.76-0.91). The NDE estimate was 0.76 [95% confidence interval (CI) 0.59, 0.98], whereas the NIE estimate was 1.00 [95%CI 1.00, 1.00]. In the CDE analyses accounting for longitudinal CDAI, the CDE estimates was 1.27 [95%CI 0.60, 2.69]. We could not convincingly demonstrate a direct benefit of TNFi outside its impact on CDAI. At present, the emphasis should be on the stringent control of RA disease activity, a known important CV risk factor, regardless of medication choice.