The effect of aging and asymmetrical hearing on speech discrimination

Speech discrimination (SpD) is exacerbated by hearing loss, but the relationship between pure-tone audiometry (PTA) and SpD is poorly described and understood in the aging process. It is also unclear whether severity of left-right (L-R) differences in PTA threshold disproportionately affects SpD.

We conducted a retrospective cross-sectional study of a broad age range (10-99 years) of patients in Japan. Demographic data, SpD, and PTA threshold data were collected for each patient and side (L-R). We evaluated the association between chronological age and overall SpD, and SpD according to severity of PTA-threshold difference for ear pairs. Asymmetries in L-R PTA thresholds were stratified into four equally spaced categories: <10dB L-R difference to ≥40 dB L-R difference.

Among the 2760 eligible participants, data from 5508 ears are analyzed. Overall SpD gradually decreases with age, with SpD scores in the oldest groups being significantly worse (Kruskal-Wallis followed by Dunn's test; p < 0.0001) than those of the youngest group. Comparison of worse-hearing ears to better-hearing ears within the same severity of hearing impairment reveals significant differences on SpD in ears that have moderate or severe hearing impairment (p < 0.0001). Post-hoc analysis identifies significant differences in SpD between the worse-hearing ears and the better-hearing ears that have hearing differences of 20 dB or more.

SpD is dramatically affected by age and asymmetrical hearing. Therefore, appropriate audiological interventions should be proactively considered according to an individual's hearing level, age, and difference in L-R hearing levels.