Effect of Aging on Middle Ear Absorbance Characteristics Across Frequencies

Although age-related auditory changes are well recognized, limited studies have examined how aging affects middle ear mechanics, which can be assessed using wideband tympanometry (WBT). Unlike conventional tympanometry, WBT offers frequency-specific insights into middle ear acoustic transfer function. Ethnic differences in the anatomy of the external and middle ear such as canal length, ossicular dimensions, and stapes configuration may influence acoustic transmission. This study aimed to investigate the effect of aging on middle ear absorbance across frequencies using WBT.

A nonexperimental, standard group comparison design was used to test 60 ears from older adults (50-70 years of age) and young adults (20-30 years of age) with clinically normal hearing. Wideband absorbance was measured using click stimuli (0.2-8 kHz) at 100 dB peSPL under both ambient and peak pressure. Data were analyzed using mixed repeated-measures analysis of variance to assess the main and interaction effects of group, gender, frequency, and pressure condition; independent t test for between-group comparisons at each frequency; and paired t test between pressure within-group comparisons.

Both groups showed a similar wideband absorbance pattern. However, older adults exhibited a significantly higher absorbance at low frequencies (250-600 Hz) and a lower absorbance at high frequencies (2000-8000 Hz) compared to young adults. These differences indicate age-related alterations in middle ear mechanics, likely due to ossicular joint loosening and tissue degeneration. Pressure-related absorbance changes were more pronounced in younger adults at low to mid frequencies, suggesting that middle ear function in this group is more sensitive to pressure variations. Moreover, gender did not show a significant main effect on absorbance across frequencies.

WBT appears to be a sensitive tool to detect subtle age-related changes that may not be evident with conventional tympanometry. The findings offer insights into age-related middle ear changes and suggest possible modification that might be considered during hearing aid fitting in older adults. Additionally, it also suggests that gender may not be a significant factor in assessing middle ear transfer function.