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

摘要

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.