Evaluation of the effect of age factor on the contralateral acoustic reflex suporession test in individuals with normal hearing

The efferent auditory system has an important role in auditory perception. The medial olivocochlear bundle performs the functions of perception of speech in the presence of noise, protection of the inner ear against loud sounds and localization of sounds. It is known that the olivocochlear bundle has an inhibitory effect on the peripheral auditory system. Acoustic stimulation of the cochlea can alter contralateral afferent responses as an effect mediated by the medial efferent system. Depending on the inhibition of the efferent auditory system in the presence of contralateral noise, some mechanical and electrical changes occur in the cochlea. Contralateral suppression of the acoustic reflex can be determined by a decrease in acoustic reflex amplitude or an increase in the acoustic reflex threshold in the presence of a noise stimulus from the contralateral ear. In the contralateral acoustic reflex suppression test, an increase in the acoustic reflex threshold and a decrease in its amplitudes are considered as acoustic reflex suppression. Age-related changes in the function of the efferent auditory system have been confirmed in the superior oliveric complex and cochlear nuclei. Based on the demonstration that functional and neurochemical changes in the medial oliveric complex occur with age, a decrease in medial oliveric complex function is expected in older people. Accordingly, the amount of suppression caused by the efferent system decreases with age. In our study, which aimed to examine the effect of the age factor on the contralateral Acoustic Reflex Suppression test, 66 individuals with normal hearing in the 18-30, 31-45 and 46-65 age ranges were given a broadband noise stimulus at 40 dB SL intensity level from the contralateral ear at 500, 1000 and 2000 Hz frequencies. reflex threshold test and acoustic reflex amplitude test at 10 dB SL intensity level were applied. Acoustic reflex threshold and amplitude values of all individuals were recorded in the presence and absence of noise, and average suppression amounts were determined at frequencies of 500, 1000 and 2000 Hz. The increase in the acoustic reflex threshold and the decrease in amplitudes at all frequencies were found to be statistically significant (p<0,05). The group with the highest amount of suppression of acoustic reflex threshold and amplitude at all frequencies was found in the youngest group, 18-30 years old. As a result of the study, it was observed that the efferent hearing system was affected by age and the highest suppression amounts were in the youngest age group. In the comparison of the amount of suppression of the age groups in the study, there were significant differences in the amount of suppression in the pairwise comparisons of the 18-30 age group and 31-45 and between the 18-30 and 46-65 age groups (p <0,05), while in the comparison of the 31-45 and 46-65 age groups, there were significant differences in the amount of suppression. no significant differences were found (p >0,05). Our study is the first study in the literature examining the effect of age factor on contralateral acoustic reflex suppression test. There are few studies in the literature on contralateral suppression of the acoustic reflex. This test is a powerful test that can be more widely applied to the clinical population in the evaluation of the efferent hearing system, as acoustic reflexes can be obtained even with moderate to severe sensorineural hearing loss. Therefore, the literature should be expanded by making more studies on the contralateral acoustic reflex suppression test.