Hair-cortisol and hair-BDNF as biomarkers of tinnitus loudness and distress in chronic tinnitus

Laura Basso,Benjamin Boecking,Patrick Neff,Petra Brueggemann,Eva M J Peters,Birgit Mazurek

doi:10.1038/s41598-022-04811-0

Abstract

The role of stress and its neuroendocrine mediators in tinnitus is unclear. In this study, we measure cortisol as an indicator of hypothalamus–pituitary–adrenal (HPA) axis alterations and brain-derived neurotrophic factor (BDNF) as a marker of adaptive neuroplasticity in hair of chronic tinnitus patients to investigate relationships with tinnitus-related and psychological factors. Cross-sectional data from chronic tinnitus inpatients were analyzed. Data collection included hair sampling, pure tone audiometry, tinnitus pitch and loudness matching, and psychometric questionnaires. Elastic net regressions with n-fold cross-validation were performed for cortisol (N = 91) and BDNF (N = 87). For hair-cortisol (R2 = 0.10), the strongest effects were sampling in autumn and body-mass index (BMI) (positive), followed by tinnitus loudness (positive) and smoking (negative). For hair-BDNF (R2 = 0.28), the strongest effects were hearing aid use, shift work (positive), and tinnitus loudness (negative), followed by smoking, tinnitus-related distress (Tinnitus Questionnaire), number of experienced traumatic events (negative), and physical health-related quality of life (Short Form-12 Health Survey) (positive). These findings suggest that in chronic tinnitus patients, higher perceived tinnitus loudness is associated with higher hair-cortisol and lower hair-BDNF, and higher tinnitus-related distress with lower hair-BDNF. Regarding hair-BDNF, traumatic experiences appear to have additional stress-related effects, whereas hearing aid use and high physical health-related quality of life appear beneficial. Implications include the potential use of hair-cortisol and hair-BDNF as biomarkers of tinnitus loudness or distress and the need for intensive future research into chronic stress-related HPA axis and neuroplasticity alterations in chronic tinnitus.

Highlights

The pathogenic mechanisms linking tinnitus and stress are still not fully u nderstood1–3
Chronic stress can lead to a dysregulation of the HPA axis, which can manifest in altered stress response profiles to acute challenges8
Because the main aim of this study was to investigate associations of hair-cortisol and hair-brain-derived neurotrophic factor (BDNF) with tinnitus-related and psychological factors while controlling for confounding influences, the two biomarkers were investigated as outcome variables using elastic net regression, whereas all other assessed variables were used as predictors

Summary

Introduction

The pathogenic mechanisms linking tinnitus and stress are still not fully u nderstood. Perceived tinnitus loudness and tinnitus-related distress are two distinct phenomena that appear linked by psychological factors like tinnitus a cceptance and subjective stress level. Common psychological conditions in tinnitus patients, such as a nxiety and depression, are known to be chronic stress-related. Chronic stress is an important factor in tinnitus patients seeking clinical help. The hypothalamus–pituitary–adrenal (HPA) axis is a primary neuroendocrine stress response system. Chronic stress can lead to a dysregulation of the HPA axis, which can manifest in altered stress response profiles to acute challenges. Previous studies on HPA axis function measuring salivary cortisol in tinnitus patients reported lower overall cortisol levels, a blunted cortisol response to an acute experimental psychosocial s tressor, increased. Hair washing or the use of hair products (hair mousse, hair gel, hair wax, hair spray) within 3 days prior to sampling

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