Decline of speech understanding in the hearing impaired elderly listeners who visited our hearing aid clinic

Abstract

The aim of this study was to investigate distinctive change in the hearing impaired elderly listeners, especially about speech recognition. Subjects were 525 patients (235 males, 290 females), from 60 to 98 years of age who had visited the Hearing Aid Clinic of Otorhinolaryngology, National Center for Geriatrics and Gerontology Hospital, between June 2001 and December 2012. Pure-tone air conduction threshold determination was administered to each subject. The speech audiometry materials used to define speech discrimination ability were Japanese monosyllabic word lists, 67S word lists. Sex- and age-specific trends in maximum discrimination score (MDS) and rollover index (RI) were shown in this study. RI was computed by the formula (PBmax-PBmin)/PBmax. PBmax has almost the same meaning as MDS in Japan. PBmin represented the lowest PB score above the test intensity level of PBmax. Mean MDSs were 80.8% in their sixties, 75.3% in their seventies, 60.7% in their eighties, and 45.5% in their nineties. The rate of decrease in mean MDS per decade accelerated in the older generation. Mean RIs were 0.18 in patients in their sixties, 0.24 in their seventies, 0.30 in their eighties, and 0.30 in their nineties. It increased until the age of eighties. In the model 1, multiple logistic analyses were performed to examine the effect of age (in 10-year increments), sex and mean hearing levels in pure tone average of values at 500, 1000, 2000, 4000 Hz (in 10 dB increments) on the MDS < 60%. Significant associations were observed between MDS < 60% and age (odds ratio, 3.03; 95% confidence interval, 2.38 to 3.85), and mean hearing levels in pure tone average of values at 500, 1000, 2000, 4000 Hz (2.33; 2.03 to 2.68). Sex was not associated with MDS < 60%. In the model 2, multiple logistic analyses adjusted for age and sex were performed to examine the effect of hearing level at test frequencies of 125, 250, 500, 1000, 2000, 4000, and 8000 Hz (in 10 dB increments)on the MDS < 60%. Significant associations were observed between MDS < 60% and hearing level at 250 Hz (2.04; 1.44 to 2.89), and 2000 Hz (1.46; 1.16 to 1.83), and 4000 Hz(1.24; 1.02 to 1.50). These outcomes suggest that the important point in qualifying the fitting of hearing aid is to present the list words at an adequate sound pressure level for evaluation of speech understanding especially in the hearing impaired elderly listeners.