Understanding age-related middle ear properties and basilar membrane damage in hearing loss: A finite element analysis and retrospective cohort study

Age-related hearing loss (ARHL) is primarily attributed to inner-ear factors, yet the role of age-related middle ear characteristics remains elusive. Employing a finite element (FE) model, we conducted a comparative analysis with clinical data extracted from a retrospective cohort study involving 90 younger adults (mean age = 38.1 ± 7.7) and 111 older adults (mean age = 63.8 ± 8.4). The clinical dataset encompassed air-bone gap (ABG) measurements obtained through pure-tone audiometry (PTA) at frequencies of 0.5, 1.0, 2.0, and 4.0 kHz. FE results quantified the normalized stapes displacement value of the simulated form of air-bone gap ($\text{ABGSim}$) between the two age groups. The Mann-Whitney U test, with a significance threshold set at P < 0.05, was employed for statistical analysis. Furthermore, the study employs simulated auditory risk unit (ARU) results to evaluate basilar membrane (BM) damage. A significant intergroup discrepancy surfaces at 1.0 kHz ($\text{ABGSim}$ = 1.0; ABG: P = 0.008), with pronounced BM damage occurring within the speech frequency range (0.5–4.0 kHz) among older adults. The ARU consistently localizes within the 3–18 mm region from the base for both age groups. In conclusion, older adults exhibited significant conductive hearing loss (CHL) at 1.0 kHz but demonstrated a modest enhancement in middle ear sound transmission efficiency at 2.0 kHz. Furthermore, our research indicates that aging exacerbates damage to the BM when exposed to speech frequency excitation exceeding 90 dB sound pressure level (dB SPL).