Effects of Transcutaneous Vagus Nerve Stimulation in Older Adults

NCT ID: NCT07292623

Last Updated: 2025-12-18

Basic Information

• Recruitment Status: ENROLLING_BY_INVITATION
• Clinical Phase: NA
• Total Enrollment: 12 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-12-31
• Study Completion Date: 2026-02-28

Brief Summary

The autonomic nervous system consists of two branches, the sympathetic and the parasympathetic, which must work in balance. Its functioning can be measured indirectly by heart rate variability, which is the time between heartbeats, which is not constant. The more it varies, the greater the role of the parasympathetic branch, and vice versa. However, with age, an imbalance can occur and the parasympathetic branch can play a lesser role, resulting in less heart rate variability (the times between heartbeats become more similar).

The aim of this study is to know if electrical stimulation in the ear can improve the balance between the two branches of the autonomic nervous system in older adults, comparing two different locations of application. The main questions to answer are:

Does applying electrical stimulation to a specific area of the ear improve the balance of the autonomic nervous system? Does it also help improve hand tremors, balance, concentration, saliva production, and voice quality?

Detailed Description

Electrical stimulation (ES) of the nervous system, also denominated as neuromodulation, has been investigated for diverse conditions as cardiovascular diseases, chronic pain and psychiatric conditions. It is unknown which locations and parameters can be more effective and better tolerated. The transcutaneous ES is a non-invasive technique which has fewer side-effects than subcutaneous vagus nerve stimulation.

The aim of this study is to analyze the acute effects of transcutaneous ES on autonomic nervous modulation by heart rate variability (HRV) and heart frequency (HF) in older adults who perceive themselves as healthy, comparing two different locations for the ES, before and after a battery of motor, cognitive and other tests.. In addition, the tolerance to the current and the side-effects will be compared.

Once the participants have given their informed consent and had been checked for exclusion criteria, are invited to an experimental session. Subjects will be advised to refrain from caffeine or alcohol for 12 h and vigorous exercise for at least 24h prior to the intervention. The volunteers will be randomized by sex to begin with one of two electrode locations: cymba concha and cavum concha at the left ear (active session); or scapha and lobule at the left ear (sham-session). These two interventions will be denominated as Transcutaneous Vagus Electrical Nerve Stimulation (t-VNS) and Sham Transcutaneous Vagus Electrical Nerve Stimulation (sham t-VNS). Allocation concealment, stratified by sex, will be ensured as the person will choose a piece of paper with the assignment coded with numbers (real/placebo) from a bag containing all the coded options that only the person applying the stimulation will see and understand (coded) The stimulation location will be wiped down with alcohol and the minimum intensity, at which the stimulus is perceived, will be registered. Subsequently, the intensity will be increased until reaching the discomfort threshold, and then decreased to a strong but well-tolerated sensation.

At the beginning of the intervention, the different tests will be explained to the participant, the chest strap will be placed, its synchronisation with the HRV measurement system will be checked, and the TENS equipment will be placed on the waist using a belt.

After 10 minutes, the pre-stimulation assessment will be carried out. At the beginning of each session, participants will be allowed to try each one to familiarise themselves with it. At the end of the session, the stimulation will be applied and the variables will be measured in the same order during the actual electrical stimulation or placebo, as appropriate.

The second session will be performed in the same way, but using the application not used in the previous session (placebo or active, as appropriate).

The participants will be asked upon completion of the session their presumed group assignment.

Adverse effects will be checked at the end of each session, and again 48 h after.

Conditions

Older Adults Without Any Specific Clinical Condition; Autonomic Nervous System Imbalance; Transcutaneous Vagus Nerve Stimulation

Keywords

Transcutaneous Electric Nerve Stimulation; Vagus Nerve; Ear Auricle; Heart Rate; Aged; Voice; Saliva; Postural Balance; Tremor; Executive Function

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: TREATMENT
• Blinding Strategy: DOUBLE

Study Groups

Active tVNS

While acclimatization of the participant (10 minutes) the different tests will be explained, the chest strap will be placed, its synchronization with the HRV measurement system will be checked, and the TENS equipment will be placed on the waist using a fanny pack.

The pre-stimulation assessment will be carried out (from 10 to 40 minutes after initiating the session). Participants will be allowed to try each one to familiarize themselves with it. All the tests will be performed (tremor, saliva, Flanker, balance, voice, Heart Rate Variability- HRV). At the end of this first part, the stimulation will be applied at the left ear in the area innervated by the vagus nerve (concha and cymba concha),and all the variables will be measured again in the same order during the actual electrical stimulation, after a new HRV measurement (from 45 to 75´). Then, the last HRV measurement will be taken and the participant will be asked about tolerance, the occurrence of adverse effects, and blinding.

Group Type: ACTIVE_COMPARATOR

Active location tVNS

Intervention Type: DEVICE

The tVNS will be performed at 20 Hz and 200 microseconds, in the area innervated by the auricular branch of the vagus nerve (cymba concha and concha) in the active location.

The intensity will be set above the sensory threshold (intense tingling sensation) but below the level of discomfort. The TENS will be set to 27 seconds of working time, with a 3-second ramp-up and 90 seconds off. It will last until the end of the last HRV test.

Sham tVNS

At the beginning, the different tests will be explained, the chest strap will be placed, its synchronization with the HRV measurement system will be checked, and the TENS equipment will be placed on the waist using a fanny pack.

Next, the pre-stimulation assessment will be carried out. Participants will be allowed to try each one to familiarize themselves with it. All the tests will be performed (tremor, saliva, Flanker, balance, voice, Heart Rate Variability- HRV). At the end of this first part, the stimulation will be applied at the left ear in the area not innervated by the vagus nerve (scapha) and all the variables will be measured in the same order during the sham electrical stimulation, after a new HRV measurement. Then, the last HRV measurement will be taken and the participant will be asked about tolerance, the occurrence of adverse effects, and blinding.

Group Type: SHAM_COMPARATOR

Sham Comparator

Intervention Type: DEVICE

The tVNS will be performed at 20 Hz and 200 microseconds, in the area not innervated by by the auricular branch of the vagus nerve (scapha) for sham TENS.

The intensity will be set above the sensory threshold (intense tingling sensation) but below the level of discomfort. The TENS will be set to 27 seconds of working time, with a 3-second ramp-up and 90 seconds off. It will last until the end of the last HRV test.

Interventions

Active location tVNS

The tVNS will be performed at 20 Hz and 200 microseconds, in the area innervated by the auricular branch of the vagus nerve (cymba concha and concha) in the active location.

The intensity will be set above the sensory threshold (intense tingling sensation) but below the level of discomfort. The TENS will be set to 27 seconds of working time, with a 3-second ramp-up and 90 seconds off. It will last until the end of the last HRV test.

Intervention Type: DEVICE

Sham Comparator

The tVNS will be performed at 20 Hz and 200 microseconds, in the area not innervated by by the auricular branch of the vagus nerve (scapha) for sham TENS.

The intensity will be set above the sensory threshold (intense tingling sensation) but below the level of discomfort. The TENS will be set to 27 seconds of working time, with a 3-second ramp-up and 90 seconds off. It will last until the end of the last HRV test.

Intervention Type: DEVICE

Other Intervention Names

tVNS; aVNS; auricular vagus nerve stimulation; Active tVNS; Sham tVNS; sham aVNS; Sham auricular vagus nerve stimulation

Eligibility Criteria

Inclusion Criteria

• Non-smokers aged 65 to 80, with BMI from 18.5 to less than 30, who consider themselves healthy and are able to maintain their balance for at least 1 minute without assistance, living in A Coruña (Spain), with a 50% allocation to each sex

Exclusion Criteria

• systolic blood pressure above 160 mm Hg and diastolic blood pressure above 100 mm Hg,
• previous vagotomy, history of syncope in the last two years, or lack of reliable reading in heart rate variability
• presence of chronic pain (migraine, back, neck, shoulder, etc.) or being diagnosed with or receiving treatment for malignant, cardiovascular disease (excluding hyperlipidaemia and hypercholesterolaemia), respiratory, neurological or autonomic, metabolic (e.g. diabetes), osteoarticular of autoimmune origin (e.g. arthritis), psychiatric or history of treatment with antidepressants or anxiolytics
• impaired cognitive level
• presence of any contraindication or difficulty in applying TENS: pacemaker, defibrillator or any implanted electronic device, apprehension of electric current, burns or irritated skin or allergic reaction or any alteration in the area that prevents the electrode from being placed on the left ear;
• previous application of electrical stimulation to the ear

• Minimum Eligible Age: 65 Years
• Maximum Eligible Age: 80 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Universidade da Coruña

OTHER

Sponsor Role: lead

Responsible Party

Alicia Martínez Rodríguez

Lecturer; Faculty of Physical Therapy. Researcher; Psychosocial Intervention and Functional Rehabilitation Group

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Alicia Martínez-Rodríguez, Lecturer

Role: PRINCIPAL_INVESTIGATOR

Universidade da Coruña (University of A Coruna)

Olalla Bello, Lecturer

Role: PRINCIPAL_INVESTIGATOR

Universidade da Coruña (University of A Coruna)

Locations

Faculty of Physiotherapy

A Coruña, La Coruña, Spain

Countries

Spain

Other Identifiers

2025/295_I

Identifier Type: -

Identifier Source: org_study_id