Transient decrease in sound tolerance levels following hearing deprivation in normal-hearing subjects

Abstract

Objective: To determine the circadian influence on sound sensitivity produced by temporal hearing deprivation in healthy normal human subjects.

Design: Participants underwent bilateral earplugging before completion of anthropometry, the author's developed questionnaire, the Hamilton Anxiety and Depression Inventory, pure tone audiometry (PTA), stapedial reflex thresholds (SRT), distortion products otoacoustic emissions input/output (DPOAE-I/O), and uncomfortable loudness levels (ULLs). Afterward, the participants were randomly divided into group A, starting at 8:00 a.m. and finishing at 8:00 p.m., and group B, starting at 4:00 p.m. and ending at 4:00 a.m. Serum cortisol levels and audiological test results were obtained at the beginning and end of the session and 24-h free urinary cortisol levels were measured.

Study sample: Thirty healthy volunteers.

Results: PTA was 2.68 and 3.33 dB HL in groups A and B, respectively, with no statistical difference between them. ULLs were significantly lower in group A compared to group B, with an average of 8.1 dB SPL in group A and 3.3 dB SPL in group B (p < 0.0001). A SRT shift was observed in group A, with no difference in group B, and a night shift in DPOAE-I/O in group B.

Conclusions: Reduced loudness tolerance is demonstrated during daytime hearing deprivation in contrast to nighttime; this may be due to increased central gain in the awake cortex.

Keywords: ACTH, adrenocorticotropic hormone; BMI, body mass index; CNS, central nervous system; Central gain; DPOAE, distortion products otoacoustic emissions; DSM-V, Diagnostic and Statistical Manual of Mental Disorders; FVO, Venezuelan Foundation of Otology; GABA, ϒ-aminobutyric acid; GABA-R, ϒ-aminobutyric acid receptors; Hearing deprivation; Hyperacusis; NBN, narrow band noise; NRR, noise reduction ratio; OHC, outer hair cells; OSHA, Occupational Safety and Health Administration; SRT, stapedial reflex threshold; ULL, uncomfortable loudness level; r.p.m., revolutions per minute.

Fig. 1

A–B. Pure tone audiogram (PTA) thresholds per group, pre-and post-occlusion.

Fig. 2

A: N = 14, Group A Pre-Post Occlusion accounts for 12.07% of the total variance. p-value is < 0.0001. Abbreviations: dB SPL decibel sound pressure level, Hz Hertz, ULL Uncomfortable Loudness Level. Fig. 2B: Group B Pre-Post Occlusion accounts for 1.79% of the total variance. p-value = 0.0645 (P < 0.001). Abbreviations: dB SPL decibel sound pressure level, Hz Hertz, ULL Uncomfortable Loudness Level. Fig. 2C: Group A vs B Pre-Post Occlusion Difference accounts for approximately 1.05% of the total variance. p-value = 0.1413 (P < 0.001). Abbreviations: dB SPL decibel sound pressure level, Hz Hertz, ULL Uncomfortable Loudness Level.

Fig. 3

A–B: Group A vs. B Pre-Post Occlusion Difference accounts for approximately 1.05% of the total variance. p value = 0.1413 (Not significant). Abbreviations: dB SPL decibel sound pressure level, Hz Hertz, ULL Uncomfortable Loudness Level.

Fig. 4

A–B. DPOAE signal/noise per group, pre-and post-occlusion. Group A vs B Pre-Post Occlusion Difference accounts for approximately 0.11% of the total variance. p value = 0.4594 (P < 0.001).

Fig. 5

A–B. Serum cortisol levels per group, pre-and post-occlusion.