Effect of Recording Duration on Heart Rate Variability During taVNS (taVNS-HRV)

Effect of Recording Duration on Heart Rate Variability During Transcutaneous Auricular Vagus Nerve Stimulation: A Randomized, Sham-Controlled Crossover Study

This study aims to evaluate how different heart rate variability (HRV) recording durations reflect autonomic nervous system responses during transcutaneous auricular vagus nerve stimulation (taVNS) in healthy adults. In a randomized, sham-controlled crossover design, participants will attend two separate sessions and receive both active taVNS and sham stimulation in randomized order. During each session, a continuous 10-minute HRV recording will be obtained, and 1-minute, 5-minute, and 10-minute analysis windows will be compared. Blood pressure and pulse will also be measured before and after stimulation. The study will investigate whether shorter or longer HRV recording durations provide results comparable to the standard 5-minute recording and which duration most reliably detects autonomic changes during taVNS.

Study Overview

• Status: Not yet recruiting
• Conditions: Healthy Volunteers
• Intervention / Treatment: Device: Transcutaneous Auricular Vagus Nerve Stimulation; Device: Sham Stimulation

Detailed Description

The vagus nerve plays a central role in autonomic regulation, and heart rate variability (HRV) is a widely used noninvasive marker of autonomic nervous system activity. Transcutaneous auricular vagus nerve stimulation (taVNS) has increasingly been used in experimental and clinical research as a noninvasive method to modulate vagal activity. Although previous studies suggest that taVNS may influence parasympathetic activity, HRV measurement duration remains an important methodological issue. Standard short-term HRV analysis is commonly based on 5-minute recordings, but ultra-short and longer recordings are also used, and their validity during taVNS has not been sufficiently clarified.

This study is designed to determine whether different HRV recording durations provide comparable and reliable information during taVNS. The study will use a randomized, sham-controlled crossover design. Healthy adult participants will attend two sessions separated by a washout period of 48 to 72 hours. In one session, participants will receive active taVNS; in the other, they will receive sham stimulation. The order of sessions will be randomized.

During each session, HRV data will be collected continuously for 10 minutes using a Polar H10 chest strap. From this single uninterrupted recording, 1-minute, 5-minute, and 10-minute analysis windows will be derived. HRV parameters from time-domain and frequency-domain analyses will be calculated. Blood pressure and pulse will be measured before and after the intervention using an automated upper-arm blood pressure monitor.

Active taVNS will be applied to the cymba conchae region of the ear using commonly reported stimulation parameters. Sham stimulation will be delivered with the same device and similar sensory conditions, but at a non-vagal ear location to minimize physiologic vagal effects. This design is intended to control for nonspecific sensory and expectation-related effects.

The primary objective is to assess whether the standard 5-minute HRV recording during taVNS detects autonomic effects compared with sham stimulation. Secondary objectives are to examine the agreement between 1-minute, 5-minute, and 10-minute HRV measurements and to evaluate whether shorter or longer recordings provide additional methodological value. The relationship between HRV findings and hemodynamic responses, including blood pressure and pulse, will also be explored. This study may help identify the most appropriate HRV recording duration for future taVNS research and contribute to methodological standardization in this field.

• Study Type: Interventional
• Enrollment (Estimated): 40
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Sefa Haktan Hatık, PhD; Phone Number: +90 368 271 55 28; Email: haktanhtk@gmail.com

Study Locations

• Turkey (Türkiye)
  • Artvin, Turkey (Türkiye)
    • Artvin Coruh University, Artvin Vocational School, Disabled Care and Rehabilitation Laboratory, Artvin,
    • Contact: Ömer Dicle Kızıl, MSc; Phone Number: +90 541 523 36 91; Email: omerdiclekizil@gmail.com
    • Sub-Investigator: Ömer Dicle Kızıl, MSc

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy volunteers aged 18 to 40 years
• Able and willing to provide informed consent
• Able to tolerate active transcutaneous auricular vagus nerve stimulation and sham stimulation
• Able to comply with study instructions, including restrictions related to caffeine, nicotine, and heavy exercise before assessment
• No condition preventing heart rate variability, blood pressure, or pulse measurements

Exclusion Criteria:

• Diagnosed cardiovascular disease, arrhythmia, or pacemaker use
• History of neurologic disease that may affect autonomic nervous system function
• Regular use of medications that may affect heart rate variability or autonomic responses, including beta blockers, antiarrhythmics, or anticholinergic drugs
• Active ear infection, dermatologic lesion, or any ear condition that may interfere with stimulation
• Marked pain, discomfort, or intolerance during stimulation
• Acute infection, fever, or other acute health problem on the measurement day
• Heart rate variability data that cannot be evaluated because of excessive motion artifact

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: taVNS First; Participants assigned to this sequence will receive active transcutaneous auricular vagus nerve stimulation (taVNS) during the first session and sham stimulation during the second session, with a 48- to 72-hour washout period between sessions.	Device: Transcutaneous Auricular Vagus Nerve Stimulation; Active transcutaneous auricular vagus nerve stimulation will be applied bilaterally to the cymba conchae region of the ear using a transcutaneous stimulation device. Stimulation will be delivered for 10 minutes with a frequency of 25 Hz, a pulse width of 200 to 300 microseconds, and an individually adjusted intensity that is clearly perceptible but not painful. Heart rate variability will be recorded continuously during the intervention.; Other Names: taVNS
Sham Comparator: Sham First; Participants assigned to this arm will receive sham stimulation during the first session and active transcutaneous auricular vagus nerve stimulation (taVNS) during the second session, with a 48- to 72-hour washout period between sessions.	Device: Sham Stimulation; Sham stimulation will be delivered for 10 minutes using the same transcutaneous stimulation device and similar stimulation settings as the active intervention, but the stimulation will be applied to a non-vagal ear region, such as the earlobe or helix, to minimize physiologic vagal effects while maintaining similar sensory input. Heart rate variability will be recorded continuously during the intervention.; Other Names: Sham taVNS

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in 5-minute lnRMSSD During Active taVNS Compared With Sham Stimulation	The primary outcome is the between-condition difference in 5-minute heart rate variability, assessed by lnRMSSD derived from the continuous RR interval recording obtained during the 10-minute intervention period. The 5-minute analysis window is the prespecified standard short-term HRV measure used to compare active transcutaneous auricular vagus nerve stimulation with sham stimulation.	During the 10-minute intervention period at each study session

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Agreement Between 1-minute and 5-minute HRV Measurements During Active taVNS	Agreement between ultra-short 1-minute and standard 5-minute HRV measurements obtained from the same continuous RR recording during active taVNS will be assessed using predefined agreement analyses.	During the 10-minute intervention period at each active taVNS session
Comparison of 10-minute and 5-minute HRV Measurements During Active taVNS	HRV parameters derived from 10-minute and 5-minute analysis windows of the same continuous RR recording during active taVNS will be compared to determine whether the longer recording provides additional physiologic sensitivity or discriminatory value.	During the 10-minute intervention period at each active taVNS session
Effect of Recording Duration on HRV Differences Between Active taVNS and Sham Stimulation	Differences between active taVNS and sham stimulation will be evaluated across 1-minute, 5-minute, and 10-minute HRV analysis windows to determine whether recording duration influences the detection of autonomic effects.	During the 10-minute intervention period at each study session
Change in Systolic and Diastolic Blood Pressure After Active taVNS Compared With Sham Stimulation	Systolic and diastolic blood pressure will be measured before and immediately after each intervention session to assess hemodynamic responses to active taVNS and sham stimulation.	Immediately before and immediately after each 10-minute intervention session
Change in Pulse Rate After Active taVNS Compared With Sham Stimulation	Pulse rate will be measured before and immediately after each intervention session to assess hemodynamic responses to active taVNS and sham stimulation.	Immediately before and immediately after each 10-minute intervention session

Collaborators and Investigators

• Sponsor: Sinop University

Publications and helpful links

General Publications

• Frangos E, Ellrich J, Komisaruk BR. Non-invasive Access to the Vagus Nerve Central Projections via Electrical Stimulation of the External Ear: fMRI Evidence in Humans. Brain Stimul. 2015 May-Jun;8(3):624-36. doi: 10.1016/j.brs.2014.11.018. Epub 2014 Dec 6.
• Shaffer F, Ginsberg JP. An Overview of Heart Rate Variability Metrics and Norms. Front Public Health. 2017 Sep 28;5:258. doi: 10.3389/fpubh.2017.00258. eCollection 2017.
• Peuker ET, Filler TJ. The nerve supply of the human auricle. Clin Anat. 2002 Jan;15(1):35-7. doi: 10.1002/ca.1089.
• Clancy JA, Mary DA, Witte KK, Greenwood JP, Deuchars SA, Deuchars J. Non-invasive vagus nerve stimulation in healthy humans reduces sympathetic nerve activity. Brain Stimul. 2014 Nov-Dec;7(6):871-7. doi: 10.1016/j.brs.2014.07.031. Epub 2014 Jul 16.

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): August 31, 2026
• Study Completion (Estimated): September 15, 2026

Study Registration Dates

• First Submitted: April 6, 2026
• First Submitted That Met QC Criteria: April 6, 2026
• First Posted (Actual): April 13, 2026

Study Record Updates

• Last Update Posted (Actual): April 16, 2026
• Last Update Submitted That Met QC Criteria: April 13, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Autonomic Nervous System; Transcutaneous Auricular Vagus Nerve Stimulation; taVNS
• Other Study ID Numbers: TAVNS6

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No