VAGAL NERVE STIMULATION DOES NOT IMPROVE HEART RATE VARIABILITY IN WOMEN WITH RHEUMATOID ARTHRITIS

PURPOSE: Vagal modulation is decreased in rheumatoid arthritis (RA). Transcutaneous vagal nerve stimulation (tVNS) may increase vagal modulation as demonstrated by increases in measures of heart rate variability (HRV). The purpose of this study is to examine the effects of tVNS on HRV in RA. METHODS: Three women diagnosed with RA (Age: 51 ± 5 years, BMI: 25.1 ± 8.7 kg/m2) volunteered to participate. Participants came to the laboratory for three visits separated by 10 days. During the first visit, anthropometric data was collected and participants were familiarized with heart rate (HR) assessment using a chest strap (PolarH10) and mobile phone application (Elite HRV). Participants were instructed to assess their morning HR daily for 1 minute. At the second visit, patients were familiarized with tVNS (Xen) and mobile phone application (Neuvana). Participants continued morning HR assessment and also performed 20 minutes of tVNS. At visit three, baseline and post tVNS HR data from participants’ cellphones was imported into HRV software (Kubios) to derive the HR and vagal HRV measures which included the root mean square of successive differences (RMSSD) and high frequency power (HF). Ten-day averages of HR, RMSSD and HF at baseline and post tVNS were calculated. HRV measures were normalized using a logarithmic (ln) transformation. Significant differences between HR, lnRMSSD and lnHF at baseline and post tVNS were determined using Wilcoxin Signed Rank Tests. Significance was accepted a priori p < 0.05. RESULTS: There were no significant differences (p > 0.05) between baseline and post tVNS for HR (baseline = 73 ± 4 bpm, post tVNS = 75 ± 4 bpm, p = 0.11), lnRMSSD (baseline = 2.97 ± 0.76 ms, post tVNS = 2.90 ± 0.62 ms, p = 0.41), or lnHF (baseline = 4.2 ± 1.47ms2, post tVNS = 3.77 ± 1.46ms2, p = 0.11). CONCLUSIONS: Preliminary findings suggest that 10 days of tVNS does not improve vagal modulation in women with RA. However, a larger sample size is needed to elucidate potential effectiveness of this treatment.