AUDITORY DYSFUNCTION IN AGING AND SENILE DEMENTIA OF THE ALZHEIMERS TYPE

Objective: To determine the prevalence and type of auditory dysfunctio n in older volunteer subjects with mild probable Alzheimer's disease ( pAD). Methods: Pure-tone thresholds, word recognition in quiet, Synthe tic Sentence Identification with Ipsilateral Competing Message or Cont ralateral Competing Message, distortion-product otoacoustic emissions, and auditory brain-stem responses were done in 82 elderly volunteer s ubjects whose cognitive, psychologic, and neurologic status had been d etermined through annual testing in a research center. Based on clinic al criteria and the Clinical Dementia Rating (CDR) scale, 40 subjects had been judged to be nondemented (CDR score, 0), and 42 had a clinica l diagnosis of pAD, with 22 in the questionable (CDR score, 0.5) and 2 0 in the mild (CDR score, 1) categories. Results: The mean age-adjuste d pure-tone average thresholds (0.5, 1.0, and 2.0 kHz) were poorer in the subjects with pAD by 5.1 dB in the right ears and 6.1 dB in the le ft ears; these differences were not statistically significant. Word re cognition in quiet did not differ by CDR category. The age-adjusted sc ores on the Synthetic Sentence Identification with Ipsilateral Competi ng Message or Contralateral Competing Message were significantly reduc ed in the subjects with mild pAD. Distortion-product otoacoustic emiss ion amplitudes and auditory brain-stem response thresholds and latenci es paralleled the pure-tone threshold results and did not differ acros s the CDR groups. Conclusions: Central auditory dysfunction was eviden t in subjects with even mild cases of pAD, whereas peripheral auditory function was not different from that in age-matched control subjects. Additional research is needed to delineate the mechanisms of central auditory dysfunction and to establish the sensitivity and specificity of auditory testing in subjects with Alzheimer's disease. We recommend auditory assessment, including Synthetic Sentence Identification with Ipsilateral Competing Message or Contralateral Competing Message, for older patients in general and in particular for those in whom dementi a is suspected.