Unilateral and Bilateral taVNS in Fibromyalgia (taVNS-FMS)

May 5, 2026 updated by: BUSENUR KARAGÖZ, Istanbul Gelisim University

Comparison of Unilateral and Bilateral Transcutaneous Auricular Vagus Nerve Stimulation on Autonomic Function and Exercise Performance in Fibromyalgia

This randomized controlled trial aimed to compare the effects of unilateral (left-sided) and bilateral transcutaneous auricular vagus nerve stimulation (taVNS) combined with a home exercise program on clinical outcomes, autonomic nervous system function, and exercise performance in individuals with fibromyalgia syndrome (FMS).

Participants diagnosed with fibromyalgia were randomly assigned to one of three groups: unilateral taVNS, bilateral taVNS, or a home exercise program. The intervention period lasted two weeks and included ten treatment sessions. Clinical outcomes were assessed using validated scales including the Fibromyalgia Impact Questionnaire (FIQ), Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI), and Pittsburgh Sleep Quality Index (PSQI). Autonomic function was evaluated using heart rate variability (HRV) parameters, and exercise performance was assessed based on repetition capacity.

The study aimed to determine whether bilateral stimulation provides additional benefits compared to unilateral stimulation and exercise alone. The findings may contribute to understanding the role of neuromodulation strategies in improving autonomic regulation, symptom severity, and functional performance in individuals with fibromyalgia.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Fibromyalgia syndrome (FMS) is a chronic condition characterized by widespread pain, fatigue, sleep disturbances, and psychological symptoms, often associated with autonomic nervous system dysfunction. Reduced heart rate variability (HRV) and increased sympathetic activity are commonly observed in individuals with FMS, contributing to impaired exercise tolerance and reduced quality of life.

Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique that targets the auricular branch of the vagus nerve and has been shown to influence autonomic regulation and central pain processing. However, evidence regarding its effects on exercise performance and the comparative efficacy of unilateral versus bilateral stimulation remains limited.

This study was designed as a randomized controlled trial including individuals diagnosed with fibromyalgia. Participants were allocated into three groups: unilateral taVNS, bilateral taVNS, and a home exercise program. The interventions were applied over a two-week period consisting of ten sessions. The taVNS intervention was administered via auricular stimulation targeting vagal afferents, while the exercise group followed a structured home-based program.

Outcome measures included clinical symptom scales (FIQ, BAI, BDI, PSQI), autonomic nervous system parameters derived from HRV analysis (including RMSSD, pNN50, LF, HF, and LF/HF ratio), and exercise performance assessed through repetition capacity. Assessments were conducted before and after the intervention period.

The primary objective was to compare the effects of unilateral and bilateral taVNS on autonomic function and exercise performance, and to evaluate whether combining neuromodulation with exercise provides additional clinical benefits in individuals with fibromyalgia. The results of this study may help inform rehabilitation strategies integrating neuromodulation and exercise-based interventions.

Study Type

Interventional

Enrollment (Actual)

90

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Were between 18 and 45 years of age

  • Were diagnosed with fibromyalgia according to the 2016 ACR diagnostic criteria

    -- Stable clinical condition

  • Ability to understand and follow study procedures
  • Willingness to participate and provide informed consent

Exclusion Criteria:

  • A history of malignancy
  • Cardiopulmonary diseases contraindicating exercise
  • Limb loss
  • Ear infections and implants, implanted electronic devices
  • Systemic diseases (hematological, endocrine, rheumatological, renal, cardiovascular, gastrointestinal, neurological, or autoimmune diseases)
  • Active infection
  • Surgery or major trauma within the previous 6 months
  • Postmenopausal status
  • Pregnancy or lactation

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Unilateral taVNS
Participants received unilateral (left-sided) transcutaneous auricular vagus nerve stimulation (taVNS) for ten sessions over a two-week period.
Device: taVNS
Transcutaneous auricular vagus nerve stimulation applied via the auricular branch of the vagus nerve for neuromodulation purposes.
Experimental: Bilateral taVNS
Participants received bilateral transcutaneous auricular vagus nerve stimulation (taVNS) for ten sessions over a two-week period.
Device: taVNS
Transcutaneous auricular vagus nerve stimulation applied via the auricular branch of the vagus nerve for neuromodulation purposes.
Active Comparator: Home Exercise Program
Participants followed a structured home-based exercise program for two weeks.
Behavioral: Home Exercise Program
A structured home-based exercise program including strengthening and mobility exercises performed over a two-week period.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Exercise performance (repetition count)
Time Frame: Baseline (Week 0) and Week 2
Number of repetitions performed during exercise sessions to evaluate functional exercise performance.
Baseline (Week 0) and Week 2

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Fibromyalgia Impact Questionnaire (FIQ) score
Time Frame: Baseline (Week 0) and Week 2
Change in Fibromyalgia Impact Questionnaire (FIQ) score (range: 0-100; higher scores indicate worse disease severity and functional impairment) to assess disease severity and functional status in patients with fibromyalgia.
Baseline (Week 0) and Week 2
Beck Anxiety Inventory (BAI) score
Time Frame: Baseline (Week 0) and Week 2
Change in Beck Anxiety Inventory (BAI) score (range: 0-63; higher scores indicate greater anxiety levels) to assess anxiety severity.
Baseline (Week 0) and Week 2
Beck Depression Inventory (BDI) score
Time Frame: Baseline (Week 0) and Week 2
Change in Beck Depression Inventory (BDI) score (range: 0-63; higher scores indicate more severe depressive symptoms) to assess depression severity.
Baseline (Week 0) and Week 2
Pittsburgh Sleep Quality Index (PSQI) score
Time Frame: Baseline (Week 0) and Week 2
Change in Pittsburgh Sleep Quality Index (PSQI) score (range: 0-21; higher scores indicate worse sleep quality) to assess sleep quality.
Baseline (Week 0) and Week 2
Heart Rate Variability (RMSSD)
Time Frame: Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Change in RMSSD (ms), reflecting parasympathetic activity.
Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Heart Rate Variability (pNN50)
Time Frame: Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Change in pNN50 (%), representing parasympathetic modulation.
Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Heart Rate Variability (HF power)
Time Frame: Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Change in high-frequency (HF) power (ms²), reflecting parasympathetic nervous system activity.
Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Heart Rate Variability (LF power)
Time Frame: Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Change in low-frequency (LF) power (ms²), reflecting mixed sympathetic and parasympathetic activity.
Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Heart Rate Variability (LF/HF ratio)
Time Frame: Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement
Change in LF/HF ratio (unitless), indicating autonomic balance between sympathetic and parasympathetic systems.
Week 0 pre-exercise measurement, Week 0 post-exercise measurement, Week 2 pre-exercise measurement, and Week 2 post-exercise measurement

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Istanbul Gelisim University

Collaborators

Bahçeşehir University

Investigators

  • Principal Investigator: Kerem KARAGÖZ, PhD, Bahçeşehir University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 1, 2022

Primary Completion (Actual)

June 20, 2023

Study Completion (Actual)

June 20, 2023

Study Registration Dates

First Submitted

April 28, 2026

First Submitted That Met QC Criteria

May 5, 2026

First Posted (Actual)

May 11, 2026

Study Record Updates

Last Update Posted (Actual)

May 11, 2026

Last Update Submitted That Met QC Criteria

May 5, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • FMS-taVNS-2022-01

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data (IPD) will not be shared due to ethical and privacy considerations. The study involves a limited sample size, and participants did not consent to data sharing beyond the scope of this research.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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