The Independent and Combined Effects of Mindfulness Meditation and Transcranial Direct Current Stimulation on Central Pain Processing in Adults with Knee Osteoarthritis

OBJECTIVE: The Pain Relief for OsteoArthritis through Combined Treatment (PROACT) was a proof-of-principle mechanistic randomized controlled trial to examine the effects of Breathing and Attention Training (BAT), and transcranial direct current stimulation (tDCS) on pain modulatory balance, pain-related brain function, and clinical pain in middle-aged to older adults with knee osteoarthritis (OA). METHODS: Participants completed baseline health screening, clinical knee pain assessment, quantitative sensory testing (QST), and functional magnetic resonance imaging (fMRI) in response to mechanical pain evocation of the index knee. They were randomized to receive concurrent sham BAT/sham tDCS, active BAT/sham tDCS, sham BAT/active tDCS or active BAT/active tDCS. Participants completed 20-minute interventions for five consecutive days. After, participants repeated the clinical knee pain assessment, QST, and fMRI. RESULTS: Adjusted analyses of 226 completers revealed no significant main effects of treatment on clinical pain or pain modulatory balance. However, average pain-evoked cerebral blood flow across pain-related regions of interest was significantly lower for active tDCS (-3.14 [CI:-4.83- -1.45]) vs. sham tDCS (-0.51 [CI:-2.19-1.17]), though this finding did not survive multiple correction. Pre-planned follow-up comparisons revealed that the active BAT/active tDCS group showed lower post-intervention pain-evoked cerebral blood flow than the sham BAT/sham tDCS group. CONCLUSIONS: The PROACT study found that mindfulness meditation in combination with tDCS may reduce pain-evoked cerebral blood flow in adults with knee OA. Future research is needed to determine if a longer duration of exposure to the combined active BAT/active tDCS treatment beneficially influences pain modulatory balance and clinical knee pain in this population.