Audiological Correlates of Speech Understanding Deficits in Elderly Listeners with Mild-to-Moderate Hearing Loss. I. Age and Lateral Asymmetry Effects

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Abstract
The study was conducted to answer two questions: 1) Which auditory measures detect impairments attributable to age rather than hearing loss? 2) Among the elderly, is there a lateral asymmetry of performance? Audiological status and auditory performance of a group of elderly (60 to 81 yr old) and normal-hearing young (18 to 30 yr old) individuals were determined through a test battery. When present, the hearing loss of elderly subjects was symmetrical in the two ears and, at most, moderate. The battery included tests of speech intelligibility on the word and sentence levels, with and without the presence of interfering speech. In addition to pure-tone and speech reception thresholds, perception of spectrally or temporally distorted speech and auditory resolution of frequency, time, and space were tested. Two tests received special consideration: the Speech Perception In Noise Test and the Modified Rhyme Reverberation Test. Results indicated that 1) hearing loss was a major factor differentiating auditory performance of elderly and young individuals, and 2) genuine age-related deficits were found in measures assessing auditory resolution and the ability to utilize spatial, temporal, and/or linguistic context information to perceptually separate a speech target from surrounding speech noise. Furthermore, the elderly group exhibited a right-ear advantage, caused by left-ear deficits, in tests measuring central auditory processing and a slight left-ear advantage in tests measuring peripheral auditory resolution. The findings suggest that, after controlling for the effect of hearing loss, there are a number of test measures in which performance of elderly and young listeners differs. Regarding lateral asymmetry, a disproportionate decline in auditory processing in the left ear of elderly individuals has been demonstrated. The major clinical conclusion is that, when testing an elderly group's performance regarding any given auditory function, the influence of pure-tone threshold elevations, no matter how mild, cannot be disregarded.

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