Expert Roundtable | September 2015 Hearing Review
Note: This is the third article in a seven-part special Expert Roundtable series published in the September 2015 edition of The Hearing Review, guest-edited by Douglas Beck, AuD. For all the articles in this Expert Roundtable, click here.
Chapter 3: The interactions between aging, cognition, and listening ability
Studies demonstrate that, even in the absence of elevated audiometric thresholds, various levels of speech processing are affected by age and co-occur with changes in cognition and a decline in the sensitivity to supra-threshold temporal cues. From a clinical perspective, these findings indicate a need for diagnostic tests in addition to the audiogram when assessing the hearing of older people.
Among the hallmarks of aging in adults are difficulties in understanding speech, especially in noisy and reverberant conditions.1 It has long been known that hearing sensitivity, as measured by the pure-tone audiogram, worsens with increasing age2 and that this is associated with poorer speech intelligibility.3
The standard treatment for these difficulties is the provision of hearing aids which, at least partially, restore audibility of those sounds that would not otherwise be perceived by the hearing-impaired person. While hearing aids generally improve speech identification, the observed benefit often falls short of what would be expected based on the audibility of the speech (for a review, see Humes and Dubno4). One possible explanation for this is that age-related changes in supra-threshold auditory processing and cognition—that is, factors not captured by a traditional audiometric assessment—contribute to the speech-identification difficulties of older people.
To study these age effects, researchers generally compare older listeners to younger controls. Due to the high prevalence of sensorineural hearing loss in the older population, establishing audiometric equality between these age groups is not easy. Consequently, alternative solutions have been sought to match audibility across listeners, including spectrally shaping the speech signal for the older listeners, or statistically removing the effect of hearing loss. However, these approaches do not control for possible “central effects of peripheral pathology”5 in the older listeners (ie, physiological and anatomical changes in the central auditory system induced by peripheral pathology).
In a study6 published this year, we investigated whether aging is associated with reduced speech intelligibility even for listeners with normal audiograms (ie, audiometric thresholds ? 20 dB HL up to and including 6 kHz in each ear). Older (60-79 years) and younger (18-27 years) listeners, matched in terms of audiogram, years of education, and non-verbal intelligence were tested on speech identification (consonants and sentences) in quiet and in interfering maskers (unmodulated and modulated noise and speech babble) of varying levels, as well as on supra-threshold auditory processing (sensitivity to temporal-fine-structure and temporal-envelope cues) and cognitive abilities (including memory, attention, and processing speed). The results showed that speech identification performance was consistently lower for the older than for the younger normal-hearing listeners across all masker types and levels.
Somewhat surprisingly, these deficits were not reflected in the self-ratings of the listeners’ hearing abilities on standard questionnaires (such as the SSQ and APHAB). Sensitivity to both types of temporal cues was reduced in older listeners and correlated positively with masked speech identification; however, this was not due to a reduced ability to listen in the temporal dips of the fluctuating maskers.
Many, but not all, cognitive abilities were lower for the older listeners, and better overall cognitive performance was associated with higher intelligibility of masked speech (see, however, Füllgrabe and Rosen,7 showing that working memory is not associated with speech-in-noise intelligibility in younger normal-hearing listeners). For the linguistically more complex sentence material, intelligibility in noise was best predicted by composite measures of cognition and, to a lesser extent, sensitivity to temporal fine structure.
An important implication of these findings is that current knowledge of the perceptual consequences of peripheral hearing loss on speech perception is likely biased by age effects, as most published studies have compared younger normal-hearing to older hearing-impaired listeners, with age differences up to 50 years between the listener groups!
The results of this “proof-of-concept” study constitute important evidence that age-related deficits indeed exist independently of the ubiquitous decline in hearing sensitivity, but the use of two discrete age groups did not allow us to determine when exactly during adulthood these deficits can first be observed. This question is currently being investigated in a large-scale study of audiometrically normal-hearing listeners sampled continuously across the adult lifespan, using a battery of speech, temporal-processing, and cognitive tasks. The preliminary data suggest that age-related changes in all three domains are already present in midlife, with the earliest deficits (for listeners aged 30-39 years) observed for a binaural task of temporal-fine-structure processing.8
Taken together, these studies demonstrate that, even in the absence of elevated audiometric thresholds, various levels of speech processing—from phoneme identification to paragraph comprehension—are affected with age. These deficits co-occur with changes in cognition and a decline in the sensitivity to supra-threshold temporal cues. From a clinical perspective, these findings indicate a need for diagnostic tests in addition to the audiogram when assessing the hearing of older people.
1) Aging is associated with a reduced ability to understand speech even when the standard measure of hearing—the audiogram —remains normal.
2) Poorer speech understanding is associated with lower general cognitive functioning and reduced abilities to discriminate sounds that are clearly audible.
CHABA. Speech understanding and aging. J Acoust Soc Am. 1988;83(3):859-895.
Bunch CC. Age variations in auditory acuity. Arch Otolaryngol. 1929;9(6):625-636.
Harris JD, Haines HL, Myers CK. A new formula for using the audiogram to predict speech hearing loss. Arch Otolaryngol. 1956;63(2):158-176.
Humes LE, Dubno JR. Factors affecting speech understanding in older adults. In: Gordon-Salant S, Frisina RD, Popper AN, Fay RR, eds. The Aging Auditory System. Heidelberg: Springer;2010:211-257.
Willott JF. Anatomic and physiologic aging: A behavioral neuroscience perspective. J Am Acad Audiol. 1996;7(3):141-151.
Füllgrabe C. Age-dependent changes in temporal-fine-structure processing in the absence of peripheral hearing loss. Am J Audiol. 2013;22(2):313-315.
Füllgrabe C, Rosen S. Investigating the role of working memory in speech-in-noise identification for listeners with normal hearing. In van Dijk P, Baskent D, Gaudrain E, de Kleine E, Wagner A, Lanting C, eds. Physiology, Psychoacoustics and Cognition in Normal and Impaired Hearing: Heidelberg: Springer;2015.
Füllgrabe C, Moore BC, Stone MA. Age-group differences in speech identification despite matched audiometrically normal hearing: contributions from auditory temporal processing and cognition. Frontiers in Aging Neurosci. 2015;6:347.
Christian Füllgrabe, PhD, is a senior investigator scientist at the MRC Institute of Hearing Research in Nottingham, United Kingdom.
Correspondence can be addressed to HR or [email protected]
Original citation for this article: Füllgrabe C. Beyond audibility: The role of supra-threshold auditory processing and cognition in presbycusis. Hearing Review. 2015;22(9):18.
This article is one of seven chapters in a series of articles that review the key points addressed during the 2015 AudiologyNOW! session titled “Issues, Advances, and Considerations in Cognition and Amplification.” Follow the links to related chapters by Douglas L. Beck, PhD, Brent Edwards, PhD, Gabrielle Saunders, PhD, Jason Galster, PhD, Andrea Pittman, PhD, and Gurjit Singh, PhD.