Home-based transcranial direct current stimulation for persistent pain state in rheumatoid arthritis: a randomized trial

BACKGROUND: Although effectively controlling inflammation, up to 50% of patients with rheumatoid arthritis (RA) experience persistent pain, associated with central sensitization and neuroinflammation. Home-based transcranial direct current stimulation (tDCS) has shown efficacy in chronic pain. OBJECTIVE: To investigate whether anodal tDCS (a-tDCS) is more effective than sham stimulation in reducing pain. METHODS: Randomized, double-blind, sham-controlled trial with 34 women (18-70 years) with RA and VAS > 40 mm. Participants were randomized to receive a-tDCS (n = 17) or sham tDCS (n = 17). Home-based tDCS (2 mA, 20 min/day) or sham (2 mA, 90 s) for four weeks, using anodal-left M1 montage. Primary outcomes was pain (Visual Analogue Scale, VAS), Secondary outcomes included pressure pain threshold (PPT), central sensitization (CSI), physical function (HAQ-DI), fatigue (FACIT-F), CNS biomarkers, adherence, and safety. RESULTS: Mean VAS reduction from baseline was greater in the a-tDCS group (-33.5 mm) versus s-tDCS (-14.1 mm), with a between-group difference of -19.4 mm (95% CI, -29.3 to -9.5; p = 0.003). Linear mixed-effects models showed that a-tDCS reduced VAS pain by 27.7% versus 6.0% with sham, a between-group difference of 21.7% (Cohen's d = 1.15). HAQ-DI improved by 38.0% versus 7.2% (ES = 1.10). a-tDCS reduced analgesic use by 62% (RR = 0.38; 95% CI, 0.18-0.79). Exploratory analyses suggested that neuroplasticity mechanisms might mediate these effects. CONCLUSION: Home-based a-tDCS effectively reduced pain, disability, and analgesic use in RA patients with persistent pain without objective inflammation.