Effects of Transcutaneous Auricular Vagus Nerve Stimulation on Symptom Severity, Sleep Quality, Central Sensitization, and Kinesiophobia in Fibromyalgia

January 14, 2026 updated by: Hatice Betigul Meral

Effects of Transcutaneous Auricular Vagus Nerve Stimulation on Symptom Severity, Sleep Quality, Central Sensitization, and Kinesiophobia in Fibromyalgia: A Randomized Controlled Trial

Fibromyalgia is a chronic condition characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and sensitivity to touch. Current treatments often provide only partial relief. This study evaluates a non-invasive technique called transcutaneous auricular vagus nerve stimulation (TaVNS), which delivers gentle electrical impulses to a part of the ear connected to the vagus nerve. The vagus nerve plays an important role in regulating pain, stress, and autonomic body functions such as sleep.

In this randomized controlled pilot trial, participants with fibromyalgia are assigned to receive either active TaVNS or sham (placebo) stimulation for 30 minutes per day, five days per week, over a four-week period. Participants are followed for a total of 8 weeks. The investigators will assess outcomes including pain intensity, sleep quality, central sensitization, and fear of movement (kinesiophobia).

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Fibromyalgia (FM) is a chronic pain syndrome associated with widespread musculoskeletal pain, fatigue, sleep disturbances, and autonomic dysregulation. Current treatments provide only partial relief, highlighting the need for novel therapeutic approaches.

Rationale:

The vagus nerve is a key regulator of autonomic and inflammatory processes. Transcutaneous auricular vagus nerve stimulation (TaVNS) is a non-invasive technique that can modulate vagal activity through electrodes placed on the external ear, offering a potential alternative to surgically implanted vagus nerve stimulators.

Study Design:

This is a randomized, sham-controlled pilot trial conducted at Istanbul Medipol University. Thirty participants with fibromyalgia are randomized in a 1:1 ratio to receive either active TaVNS or sham stimulation.

Intervention:

Device: VagusStim® (Vagus Medical Technologies, Istanbul, Türkiye; CE-marked).

Electrode placement: left cymba concha (active group) vs. left earlobe (sham group).

Stimulation parameters: frequency 1-30 Hz, pulse width 50-250 μs, current intensity individually adjusted (0.1-36 mA) to each participant's sensory threshold.

Schedule: 30 minutes per day, 5 days per week, for 4 consecutive weeks (20 sessions total).

Supervision: All sessions are clinician-supervised.

Outcome Measures:

Primary outcomes:

Pittsburgh Sleep Quality Index (PSQI) - subjective sleep quality.

Fibromyalgia Impact Questionnaire (FIQ) - disease severity and functional impact.

Central Sensitization Inventory (CSI) - symptoms related to central sensitization.

Secondary outcomes:

Visual Analog Scale (VAS) - pain intensity.

Tampa Scale for Kinesiophobia (TSK) - fear of movement.

Symptom Severity Scale (SSS).

Widespread Pain Index (WPI).

Assessment timepoints: baseline, week 2, week 4, and week 8.

Study Type

Interventional

Enrollment (Actual)

30

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

  • Turkey (Türkiye)
    • Bagcılar
      • Istanbul, Bagcılar, Turkey (Türkiye), 34815
        • Istanbul Medipol University, Faculty of Medicine, Department of Physical Medicine and Rehabilitation

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
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

Age between 18 and 65 years

Diagnosis of fibromyalgia according to the 2016 revised ACR criteria

Receiving stable pharmacological and/or non-pharmacological treatment for at least 3 months

Ability to understand study procedures and provide informed consent

Exclusion Criteria:

Pregnancy

History of epilepsy or cardiac arrhythmia

Acute or chronic infection

Heart failure (NYHA class II-IV)

Renal failure stage II or higher

Active malignancy

Psychotic disorders or current psychiatric treatment

Diagnosis of immune-mediated rheumatic disease

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: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Active TaVNS
Participants received active transcutaneous auricular vagus nerve stimulation (TaVNS) using the VagusStim® device (Vagus Medical Technologies, Istanbul, Türkiye). The electrode was placed on the left cymba concha and stimulation was applied for 30 minutes per day, 5 days per week, over 4 weeks (20 sessions). Stimulation parameters included 1-30 Hz frequency, 50-250 μs pulse width, and current individually adjusted (0.1-36 mA) to each participant's sensory threshold.
Device: Active Transcutaneous Auricular Vagus Nerve Stimulation (TaVNS)
Active TaVNS delivered with the VagusStim® device (Vagus Medical Technologies, Istanbul, Türkiye). The bipolar electrode was placed on the left cymba concha. Stimulation was applied for 30 minutes per day, 5 days per week, for 4 weeks (20 sessions). Parameters included frequency 1-30 Hz, pulse width 50-250 μs, and current intensity individually adjusted (0.1-36 mA) to the participant's sensory threshold.
Placebo Comparator: Sham TaVNS
Participants underwent sham stimulation using the same VagusStim® device under identical conditions. The electrode was placed on the left earlobe, an area without vagal innervation, and sessions lasted 30 minutes per day, 5 days per week, for 4 weeks. No effective vagus nerve stimulation was delivered, maintaining participant blinding.
Device: Sham Transcutaneous Auricular Vagus Nerve Stimulation
Sham stimulation delivered with the same VagusStim® device under identical conditions. The electrode was rotated and placed on the left earlobe, which lacks vagal innervation. Sessions lasted 30 minutes per day, 5 days per week, for 4 weeks (20 sessions). No effective vagus nerve stimulation was delivered, preserving participant blinding.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Fibromyalgia Impact Questionnaire (FIQ)
Time Frame: Baseline, Week 2, Week 4, Week 8
The FIQ evaluates the overall health status and functional impact of fibromyalgia, including physical functioning, pain, fatigue, and mood. Scores range from 0 to 100, with higher scores reflecting greater disease impact.
Baseline, Week 2, Week 4, Week 8
Pittsburgh Sleep Quality Index (PSQI)
Time Frame: Baseline, Week 2, Week 4, Week 8
The PSQI is a validated self-report questionnaire that assesses subjective sleep quality and disturbances over the past month. Scores range from 0 to 21, with higher scores indicating poorer sleep quality.
Baseline, Week 2, Week 4, Week 8
Central Sensitization Inventory (CSI)
Time Frame: Baseline, Week 2, Week 4, Week 8
The CSI is a 25-item self-report questionnaire assessing symptoms related to central sensitization, including sensitivity to pain, fatigue, and cognitive complaints. Scores range from 0 to 100, with higher scores indicating greater sensitization.
Baseline, Week 2, Week 4, Week 8

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Tampa Scale for Kinesiophobia (TSK)
Time Frame: Baseline, Week 2, Week 4, Week 8
The TSK is a 17-item self-report questionnaire measuring fear of movement or reinjury. Items are scored on a 4-point Likert scale, with total scores ranging from 17 to 68. Higher scores indicate greater kinesiophobia.
Baseline, Week 2, Week 4, Week 8
Visual Analog Scale (VAS) for Pain
Time Frame: Baseline, Week 2, Week 4, Week 8
Pain intensity is assessed using a 10-cm visual analog scale, with 0 representing "no pain" and 10 representing "worst imaginable pain." Participants mark their pain level along the line, which is recorded as a numeric score.
Baseline, Week 2, Week 4, Week 8

Collaborators and Investigators

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

Sponsor

Hatice Betigul Meral

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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)

August 1, 2025

Primary Completion (Actual)

October 10, 2025

Study Completion (Actual)

October 10, 2025

Study Registration Dates

First Submitted

September 5, 2025

First Submitted That Met QC Criteria

September 12, 2025

First Posted (Estimated)

September 15, 2025

Study Record Updates

Last Update Posted (Actual)

January 15, 2026

Last Update Submitted That Met QC Criteria

January 14, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • E-10840098-202.3.02-4945 (30/0

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

This study is a small, single-center pilot trial. Due to the limited sample size and ethical/privacy considerations, individual participant data will not be shared in a public repository. De-identified data may be made available from the corresponding author upon reasonable request.

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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