Determinants of Speech Perception Outcomes After Hearing Aid Fitting in Conductive and Sensorineural Hearing Loss: A Prospective Longitudinal Observational Study

Background/Objectives: Hearing loss is a leading cause of disability worldwide, with speech perception representing a key functional outcome of auditory rehabilitation. While hearing aids improve audibility, outcomes vary substantially across clinical subgroups. This study aimed to compare speech perception outcomes after hearing aid fitting in adults with conductive and sensorineural hearing loss and to identify determinants of variability in rehabilitation outcomes. Methods: This prospective longitudinal observational study included 250 adults with clinically confirmed bilateral conductive or sensorineural hearing loss who underwent standardized audiological assessment, bilateral hearing-aid fitting, immediate post-fitting evaluation, and 3-month follow-up in Kazakhstan between January 2023 and December 2024. Participants were classified as having conductive (n = 100) or sensorineural hearing loss (n = 150) based on audiometric criteria. Speech perception was assessed using a Kazakh-language open-set speech audiometry test. Multivariable linear regression models were used to estimate differences in 3-month aided speech perception after adjustment for the corresponding immediate post-fitting aided score and prespecified demographic, clinical, and audiometric covariates. Linear mixed-effects models were used separately to assess change in aided speech perception from immediate post-fitting to 3 months and to test whether this change differed by hearing-loss type. Propensity score matching was performed as a secondary sensitivity analysis. Results: Patients with conductive hearing loss demonstrated consistently higher speech perception scores than those with sensorineural hearing loss across all conditions. At 3 months, adjusted analyses showed no significant difference between groups for aided speech perception in quiet at 60 dB SPL, whereas sensorineural hearing loss remained associated with lower aided speech perception in noise at 60 dB SPL with SNR +3 dB (β = −1.73; 95% CI: −3.10 to −0.36; p = 0.014). In mixed-effects models assessing repeated aided scores from immediate post-fitting to 3 months, sensorineural hearing loss was associated with lower overall aided speech perception in both quiet and noise conditions. A modest improvement over time was observed only for speech perception in noise, and the group-by-time interaction was not statistically significant. Increasing age, higher tonal thresholds, advanced hearing loss stage, and living alone were independently associated with poorer outcomes. Conclusions: Aided speech perception scores were high after hearing-aid fitting in both conductive and sensorineural hearing loss; however, patients with sensorineural hearing loss showed persistently poorer outcomes, particularly in noise. These findings highlight the importance of incorporating speech-in-noise assessment and addressing clinical and social determinants to support hearing rehabilitation.

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