Investigating the use of Heart Rate Entrainment for reducing Tinnitus using Biosensors

Abstract

Background: Entrainment refers to the adaptation of the frequency of one or more independent rhythmical systems to that of another. Evidence suggest that rhythmic auditory stimuli are able to entrain neural oscillators, reactive attention, and more recently, heart rate. Due to strong links between the auditory, limbic, and autonomic nervous systems, heart rate entrainment is linked to a downregulation of sympathetic tone and positive emotional changes. Elevated levels of emotional distress and sympathetic tone have been shown in people with tinnitus. This study investigates whether a rhythmic auditory stimulus is able to reduce the perception of tinnitus through heart rate entrainment. The hypothesis is that a rhythmic stimulus overlaid with broadband noise will reduce sympathetic tone and improve emotional ratings, leading to a greater reduction in tinnitus compared to broadband noise alone. Methods: Fourteen participants with constant bothersome tinnitus and good cardiovascular health underwent audiological assessment and psychoacoustical evaluation of tinnitus. Participants were presented with two sounds: a rhythmic click overlaid with broadband noise and broadband noise alone. Each sound was presented for 30 minutes in a counterbalanced order and participants were given a 15 minute break between each sound. The level of sympathetic activity was quantified using heart rate, blood pressure, and heart rate variability. Emotional and tinnitus ratings were measured using the Positive and Negative Affect Schedule and Tinnitus Severity Numeric Scale, respectively. These measures were carried out before and during the last 5-minutes of presentation for both sounds. Correlations between changes in sympathetic activity, emotional ratings, and tinnitus ratings for both sounds were also investigated. Results: No statistically significant changes in measures of sympathetic activity and emotional ratings were found for either sound. Tinnitus ratings showed a statistically significant improvement in several domains, more so in response to the rhythmic click overlaid with broadband noise than broadband noise alone. Statistically significant negative correlations were found between changes in heart rate and changes in tinnitus ratings in response to broadband noise alone. A statistically significant positive correlation was found between changes in diastolic blood pressure and changes in negative emotional ratings in response to the rhythmic click overlaid with broadband noise.