Effect of age on click-evoked otoacoustic emission A systematic review

OBJECTIVE：The aims of this study were to investigate the changes of the total intensity of transient evoked otoacoustic emission（TEOAE） and signal-to-noise ratio in various frequency bands as a function of aging,and to explore the role of age-related decline of cochlear outer hair cells.DATA SOURCES：The literature was searched using the PubMed database using ＇transient-evoked otoacoustic emissions＇ as a keyword.Articles were limited as follows：Species was ＇Humans＇;languages were ＇English and Chinese＇;publication date between 1990-01-01 and 2010-12-31.The references of the found were also searched to obtain additional articles.DATA SELECTION：Inclusion criteria：（1） Articles should involve the total TEOAE level or signal-to-noise ratio.（2） The measurement and analysis system used was Otodynamics ILO analysis system（ILO88,ILO92,ILO96 or ILO292）.（3） Studies involved groups of greater than 10 subjects and TEOAE results were from normally hearing ears.（4） If more papers from the same author or laboratory analyzed the same subjects,only one was used.MAIN OUTCOME MEASURES：The correlations of the age scale with the total level and signal-to-noise ratio of TEOAE was determined,respectively.RESULTS：（1） TEOAE total level gradually increased until 2 months of age,and then decreased with increasing age.Significant negative correlations between total TEOAE level and age were found（r =-0.885,P = 0.000）.（2） The most rapid decrease of TEOAE amplitude occurred at 1 year old.The total TEOAE level decreased about 4.25 dB SPL between 2 months to 1 year old,then about 0.26-0.52 dB SPL from 1 year to 10 years old,about 0.23 dB SPL from 11 years to 25 years old,and about 0.14 dB SPL from 26 years to 60 years old.（3） The signal-to-noise ratio in the frequency bands centered at 1.5,2,3 and 4 kHz decreased with increasing age after 2 months of age.Significant negative correlations between the signal-to-noise ratio and age were found for frequency bands ranging from 1.5 kHz to 4 kHz,with the highest correlations at 4 kHz（r =-0.890,P 〈 0.01）,then at 3 kHz（r =-0.889,P 〈 0.01）,at 2 kHz（r =-0.850,P 〈 0.01） and at 1.5 kHz（r =-0.705,P 〈 0.05）.Conversely,a positive correlation between the signal-to-noise ratio centered at 1 kHz and age was found,but was not statistically significant（r = 0.298,P = 0.374）.CONCLUSION：The total TEOAE response level decreased with increasing age after the first 2 months of age.The signal-to-noise ratio also decreased with increasing age in frequency bands above 1.5 kHz.The signal-to-noise ratio in higher frequencies decreased faster than in lower frequencies,leading to the maximum signal-to-noise ratio shift form 3.2-4.0 kHz in neonates to 1.5 kHz in adults,and further decreasing the total TEOAE response level.The age-related TEOAE spectrum peak shift is most likely because the outer hair cells functioning in higher frequencies are more prone to damage than those for lower frequencies.

Otoacoustic Emissions and Evoked Potentials in Infants after Breast-Feeding Jaundice——Hearing Dysfunction in Breast-Feeding Jaundice

We study hearing in a group of infants with Breast-feeding jaundice (BFJ) by means of Transient-evoked otoacoustic emissions (T-EOE) and Brainstem auditory evoked potentials (BAEP) searching for relationship between bilirubin serum levels and auditory dysfunction. Eleven infants born at-term with BFJ were selected for the study. We studied also 11 control age- and gender matched healthy at-term infants without signs of jaundice. T-EOAE studies were performed between 5-7 days after birth, and 3 months later. BAEP studies were performed once. BFJ group infants exhibited lower amplitudes in T-EOE than infants in the control group. These differences disappear at the 3-month evaluation. In BAEP, we observed a significant latency delay of waves I and V in Breast-feeding jaundice group infants. All infants in both groups demonstrated reproducible wave V response at 30 decibels. No significant correlation values were observed between bilirubin serum levels and T-EOE and BAEP variables. Our data suggest that BFJ can result in transient peripheral and central auditory dysfunction. Dysfunction is reversible after treatment of infants with BFJ.