Auditory Agnosia for Environmental Sounds in Alzheimer’s Disease: Not Hearing and Not Listening?

Abstract

Auditory agnosia for environmental sounds (AES) is an example of central auditory dysfunction. It is presumed to be independent of language deficits and in presence of normal hearing. We undertook a detailed neuropsychological assessment including environmental sound naming and recognition in 34 clinically mild Alzheimer's disease (AD) patients and 29 age-matched healthy control subjects. In patients with AD, audiometry was performed to assess the impact on test performance, and in normal controls the Hearing Handicap Inventory for the Elderly -Screening Version to exclude more than mild hearing loss. We adapted a validated environmental sound battery and found near perfect scores in controls. We found that environmental sound agnosia is common in mild AD. We found a statistically significant difference in mean pure tone audiometry in the best ear between patients with and those patients without naming deficits of 11.3 dB (p = 0.010) and of 14.7 dB (p = 0.000) between those with and without recognition deficits. Statistical significance remained after correcting for age, aphasia, Mini-Mental State Examination score, and working memory. Slight and moderate peripheral hearing loss increases the odds ratio of recognition deficits by 13.75 (confidence interval 2.3-81.5) compared to normal hearing patients. We did not find evidence for different forms of AES. This work suggests that an interaction between peripheral hearing loss and AD pathology produces problems with environmental sound recognition. It confirms that the relationship between hearing and dementia is complex but also suggests that interventions to prevent and treat hearing loss could have an effect on AD in its clinical expression.

(Zu-)Hören mit alterndem Gehirn – eine kognitive Herausforderung

“…For example, Goll et al [129] demonstrated that Alzheimer patients were significantly worse at discriminating spectrally and temporally altered environmental sounds compared to healthy individuals with comparable peripheral auditory thresholds when non-verbal working memory was taken into account, while the ability to perceive pitch and timbre remained the same. Coeberg et al [134] also found significantly more auditory agnosia for environmental sounds in patients with mild Alzheimer's disease compared to healthy individuals, with 37 % of patients showing impairment in recognition and 57 % in naming test sounds. The mean hearing threshold of the patients affected by agnosia was significantly higher, independent of age.…”

“…Auch Coeberg et. al [134] konnten bei Patienten mit milder Alzheimer-Erkrankung im Vergleich zu Gesunden signifikant häufiger eine auditorische Agnosie für Umweltgeräusche feststellen: 37 % der Patienten wiesen dabei eine Störung der Erkennung, 57 % der Benennung der Testgeräusche auf. Die mittlere Hörschwelle der von der Agnosie betroffenen Patienten war dabei signifikant höher, und zwar unabhängig vom Lebensalter.…”

Environmental Sound Perception: Effects of Aging and Hearing Loss

“…Reduced hearing abilities in older adults can also exacerbate existing cognitive deficits. Coebergh et al (2020) tested environmental sound perception in older adults with mild Alzheimer's disease. Participants with greater agnosia for environmental sounds had higher pure-tone thresholds, even though their average audibility threshold remained within normal limits.…”