Effects of age and gender on dichotic sentence identification

Subcortical white matter pathology as a mediating factor for age-related decreased performance in dichotic listening

Cortical 'disconnection', involving disruption of white matter tracts in the brain, has been hypothesized as a mechanism of age-related cognitive decline. Diffuse hyperintensities in the white matter (so called white matter hyperintensities, WMH) on T2-weighted MRI scans are regarded to represent ischemic damage of the subcortical fiber system and are found to be increased with advanced age. In the present study, we examined whether WMH might be a mediating factor for age-effects in dichotic listening. For that purpose, we examined the association between age, deep or subcortical white matter hyperintensities (DWMH), periventricular hyperintensities (PVH) and dichotic listening performance in healthy older adults with ages ranging from 50 to 81 years. We found decreased dichotic listening performance with increasing age, specifically for the left ear (LE) but not the right ear (RE) in a standard unbiased-attention condition, and for the unattended ears but not the attended ears in conditions in which attention was controlled. Interestingly, hierarchical regression analyses revealed that the age-effect is partially mediated by DWMH specifically in the hemisphere contralateral to the attended ear. Moreover, we found indications that RE performance is specifically affected by DWMH in the right and left frontal and temporal areas, and that LE performance is mostly affected by DWMH selectively in the left hemisphere, including the left temporal area. The present study underlines the idea that disconnectivity is involved in age-related cognitive decline.

The benefits of bilateral versus unilateral amplification for the elderly: are two always better than one?

The use of bilateral hearing aids is based on the assumption that the human auditory system functions best when both ears receive incoming acoustic information. There is evidence, however, that some elderly individuals perform better while using unilateral as opposed to bilateral amplification. The main objective of the present study was to compare speech recognition in noise in elderly hearing-impaired patients initially fitted with bilateral hearing aids while they used unilateral versus bilateral amplification. A secondary goal was to investigate the association between performance with one versus two hearing aids and central auditory function as measured by a dichotic test, and to evaluate the effect of increasing age on these two measures. Twenty-eight patients (mean age 72.8 years, range: 62-86) with bilateral symmetrical mild-to-severe sensorineural hearing loss fitted with digital hearing aids, participated in the study. Speech recognition in noise was assessed in three conditions: (1) aided right ear, (2) aided left ear, (3) aided bilaterally, using the AB open-set monosyllabic word test at a signal-to-noise ratio of +10 dB. Speech stimuli were presented at 70 dB SPL via a loudspeaker located at 0 degree azimuth and the noise was presented via a second loudspeaker located at 180 degrees azimuth. In addition, dichotic listening abilities were evaluated using the threshold-of-interference test. The results of the present study indicated comparable mean group performance while using unilateral versus bilateral amplification. For the most of the patients (71%), however, speech recognition in noise was better while using unilateral amplification to the 'better' ear compared to bilateral amplification. While the performance in the dichotic test was not correlated with speech recognition in noise with bilateral versus unilateral amplification, the performance in these two tests deteriorated significantly with increasing age. Our results suggest that for elderly patients, bilateral amplification may not always be advantageous for speech recognition in noise. As most patients continue to use bilateral amplification, it is clear that there are listening situations in which bilateral amplification provides benefit. Sensitive performance measures that will tap critical aspects of daily binaural listening situations are therefore required. Finally, the deterioration in performance of the aging auditory system underscores the need to 'tailor' auditory habilitation to individual needs.

Odds of demonstrating auditory processing abnormality in the average older adult: the Blue Mountains Hearing Study

OBJECTIVE

To determine, for the average older adult, the odds of demonstrating an auditory processing abnormality for each of seven speech-based measures of auditory processing and how these odds vary based on a number of independent subject variables.

DESIGN

Using a cross-sectional design, 1576 adults aged 55 years and older were assessed with speech measures of central auditory processing and questionnaires pertaining to health status, cognitive and perceived auditory function. The speech-based measures from which abnormal/normal outcomes were derived were (a) right ear Macquarie Synthetic Sentence Identification (MSSI) test maximum performance score (Rt MSSImax), (b) left ear MSSI test maximum performance score (Lt MSSImax), (c) right ear Macquarie Dichotic Sentence Identification (MDSI) test score (Rt MDSI), (d) left ear MDSI test score (Lt MDSI), (e) difference score for the right and left ear MDSI test (MDSI Diff score), (f) right ear MSSI test maximum performance score subtracted from the maximum performance score for monosyllabic word list materials in the same ear (Rt PB-MSSImax), and (g) left ear MSSI test maximum performance score subtracted from the maximum performance score for monosyllabic word list materials in the same ear (Lt PB-MSSImax).

RESULTS

The odds of demonstrating auditory processing abnormality for average older participants, increased by 4 to 9% per year of age. Men were approximately twice as likely as women to demonstrate this abnormality, but the gender difference was only evident with dichotic measures. With increasing hearing handicap, the odds of demonstrating auditory processing abnormality increased, but this was only evident for speech-in-noise measures. With subtle cognitive decline, the odds of demonstrating auditory processing abnormality also increased.

CONCLUSIONS

This population-based study provides evidence of a link between perceived hearing handicap and outcomes on speech-in-noise measures as well as evidence of a gender difference that became apparent using dichotic tests. The contribution of central auditory processing abnormality to hearing health should therefore not be overlooked in the provision of auditory rehabilitation programs to older adults.

Complementing behavioral measures with electrophysiological measures in diagnostic evaluation: a case study in two languages

This case study focuses on a bilingual, older man who spoke Polish and English and showed weaknesses on clinical measures of dichotic listening in English. It was unclear whether these test results were influenced by the participant's facility with his second language or by other nonauditory factors. To elucidate the nature of this deficit, the authors examined behavioral and electrophysiological responses during dichotic-listening tasks involving linguistic processing in both languages. A diotic (control) condition was included to examine whether nonauditory factors, such as language familiarity, memory, or decline in speed of mental processing, might explain the dichotic results. The results from this participant were compared with those obtained from a bilingual young adult who also spoke both Polish and English. Results showed a substantial left-ear deficit for the older individual on both behavioral and electrophysiological measures of dichotic listening. The pattern of results is consistent with previous findings in demonstrating that the left-ear deficit in this patient derived from an auditory-specific defect rather than from any of the extra-auditory factors associated with language facility or cognitive decline.

Differential representation of speech sounds in the human cerebral hemispheres

Various methods in auditory neuroscience have been used to gain knowledge about the structure and function of the human auditory cortical system. Regardless of method, hemispheric differences are evident in the normal processing of speech sounds. This review article, augmented by the authors' own work, provides evidence that asymmetries exist in both cortical and subcortical structures of the human auditory system. Asymmetries are affected by stimulus type, for example, hemispheric activation patterns have been shown to change from right to left cortex as stimuli change from speech to nonspeech. In addition, the presence of noise has differential effects on the contribution of the two hemispheres. Modifications of typical asymmetric cortical patterns occur when pathology is present, as in hearing loss or tinnitus. We show that in response to speech sounds, individuals with unilateral hearing loss lose the normal asymmetric pattern due to both a decrease in contralateral hemispheric activity and an increase in the ipsilateral hemisphere. These studies demonstrate the utility of modern neuroimaging techniques in functional investigations of the human auditory system. Neuroimaging techniques may provide additional insight as to how the cortical auditory pathways change with experience, including sound deprivation (e.g., hearing loss) and sound experience (e.g., training). Such investigations may explain why some populations appear to be more vulnerable to changes in hemispheric symmetry such as children with learning problems and the elderly.

Decline of speech understanding and auditory thresholds in the elderly

A group of 29 elderly subjects between 60.0 and 83.7 years of age at the beginning of the study, and whose hearing loss was not greater than moderate, was tested twice, an average of 5.27 years apart. The tests measured pure-tone thresholds, word recognition in quiet, and understanding of speech with various types of distortion (low-pass filtering, time compression) or interference (single speaker, babble noise, reverberation). Performance declined consistently and significantly between the two testing phases. In addition, the variability of speech understanding measures increased significantly between testing phases, though the variability of audiometric measurements did not. A right-ear superiority was observed but this lateral asymmetry did not increase between testing phases. Comparison of the elderly subjects with a group of young subjects with normal hearing shows that the decline of speech understanding measures accelerated significantly relative to the decline in audiometric measures in the seventh to ninth decades of life. On the assumption that speech understanding depends linearly on age and audiometric variables, there is evidence that this linear relationship changes with age, suggesting that not only the accuracy but also the nature of speech understanding evolves with age.

Do ???Auditory Processing??? Tests Measure Auditory Processing in the Elderly?

OBJECTIVE

To examine the associations between measures of auditory processing and measures of auditory or cognitive function in elderly listeners with impaired hearing.

DESIGN

Multiple measures of auditory processing, auditory function, and cognitive function were obtained and linear, multiple-regression analyses were conducted to examine the relations between these sets of variables. In particular, four measures of auditory processing were obtained from each of 213 elderly participants. Measures of auditory processing included duration discrimination for a 1000-Hz pure tone, temporal-order discrimination for mid-frequency pure tones, dichotic syllable identification, and recognition of 45% time-compressed monosyllables. Each participant also completed additional measures of auditory function, including pure-tone thresholds, auditory brain stem responses for each ear and at two presentation rates (11.1 and 71.1 clicks per second), and performance-intensity functions for monosyllabic words (PI-PB rollover). Finally, three measures of cognitive function, all from the Wechsler Adult Intelligence Scale-Revised, were obtained from the 213 participants.

RESULTS

For three of the four measures of auditory processing examined in this study (duration discrimination, temporal-order discrimination, and dichotic CV identification), a measure of cognitive function (IQ) and age were the two primary predictors of individual differences in performance. For these three measures of auditory processing, 11 to 14% of the total variance could be accounted for by the predictor variables. For the remaining measure of auditory processing (recognition of time-compressed monosyllables), 56% of the total variance could be accounted for by a set of four predictor variables, but most of this variance (54% of the total variance) was associated with individual differences in hearing loss. When hearing loss was removed as a predictor for this measure of auditory processing, 14% of the total variance was explained by four variables: age, IQ, and two measures derived from auditory brain stem response wave-V latency.

CONCLUSIONS

Performance on the battery of auditory processing measures by elderly hearing-impaired listeners was systematically related to individual differences in cognitive function rather than auditory function, especially for stimuli not affected by peripheral hearing loss. However, much of the variance in auditory processing performance remained unaccounted for by any of the predictor variables examined in this study.

Long-term exposure to occupational noise alters the cortical organization of sound processing

OBJECTIVE

Long-term exposure to noise may cause an altered hemispheric lateralization of speech processing even in silent conditions. We examined whether this lateralization shift is speech specific or occurs also for other sounds.

METHODS

Brain responses from 10 healthy noise-exposed workers (>5 years) and 10 matched controls were recorded with a 32-channel electroencephalogram in two conditions, one including standard and deviant speech sounds, the other non-speech sounds, with novel sounds in both.

RESULTS

The deviant-sound elicited mismatch negativity (MMN) was larger to non-speech than speech sounds in control subjects, while it did not differ between the sound types in the noise-exposed subjects. Moreover, the MMN to speech sounds was lateralized to the right hemisphere in exposed workers, while it was left-hemisphere predominant in control subjects. No group topography difference was found for non-speech sounds. The deviant sounds that were close in formant space to the standards elicited a longer MMN latency in both speech and non-speech conditions in exposed subjects than controls. No group differences were found for cortical responses to novel sounds.

CONCLUSIONS

Long-term noise exposure altered the strength and the hemispheric organization of speech-sound discrimination and decreased the speed of sound-change processing.

SIGNIFICANCE

Subpathological changes in cortical responses to sounds may occur even in subjects without a peripheral damage but continuously exposed to noisy auditory environments.

Loss of Peripheral Right-Ear Advantage in Age-Related Hearing Loss

In young adults with normal hearing, the right ear is more sensitive than the left to simple sounds (peripheral right-ear advantage) and to processing complex sounds such as speech (central right-ear advantage). In the present investigation, the effects of hearing loss and aging on this auditory asymmetry were examined at both peripheral and central levels. Audiograms and transient evoked otoacoustic emission (TEOAE) and distortion product otoacoustic emission amplitudes were used to assess cochlear function. The contralateral suppression of TEOAEs was measured to assess the medial olivocochlear efferent system. The Hearing in Noise Test (HINT; binaural speech) was conducted to assess higher central auditory function. A group of aged subjects with normal hearing (flat audiograms) were compared to a group of aged subjects with sloping audiograms (presbycusis). At the cochlear (peripheral) level, the normal hearing group showed significantly higher otoacoustic emission amplitudes for the right ear compared to the left ear, which is consistent with the right-ear dominance normally seen in young adults. However, this finding was reversed in the presbycusic group that showed higher left-ear emission amplitudes. At the brainstem level, the amplitudes of TEOAE contralateral suppression were small and no significant difference was found between the right and left ears in both groups. On the contrary, HINT results showed a continuous dominance of the right ear (left hemisphere) in both groups, which was consistent with previous reports showing that the right hemisphere is more affected by age than the left hemisphere.

Impaired gap encoding in aged mouse inferior colliculus at moderate but not high stimulus levels

Age-related deterioration of auditory temporal acuity has been identified as a contributing factor in presbycusis. In the present study, the effects of aging and stimulus level on gap encoding and gap recovery functions were investigated by measuring near-field auditory evoked potentials in the inferior colliculus of eight 3 month old and eight 24 month old CBA/CaJ mice, in response to gap stimuli embedded in broadband noise (40, 60, and 80 dB SPL). Gap encoding was assessed by measuring latencies and amplitudes of peak features of the near-field response, and also with a procedure that calculated the root mean square of the response within specific time windows. The chief differences in gap encoding between young and old mice were longer gap thresholds, slower recovery functions, and longer response peak latencies for old mice at 60, but not 80 dB SPL, although the latency of the earliest measured peak remained delayed for this condition in the old compared with the young mice. These results demonstrate that age-related changes in temporal acuity may interact with stimulus level, and suggest that adequate amplification may be critically important for maintaining temporal acuity with advancing age.

Personal and social conditions potentially influencing women's hearing loss management

Little gender-specific data related to hearing loss and hearing loss management are available. The purpose of this investigation was to examine personal and social conditions affecting women at selected stages of the adult life course that may influence hearing loss management. In all, 191 women in three age groups, ranging from 35 to 85 years old, participated. None reported hearing problems. Participants completed a demographic data form and were given a standard audiometric evaluation to confirm age-normal hearing. Each completed assessments of speech understanding in quiet and noise, auditory signal duration discrimination, and binaural processing. Measures of hearing knowledge, behaviors, and attitudes; health-related locus of control; ego strength; and, social support were administered. Results revealed that although some variables deteriorate among subsequent age groups (i.e., hearing thresholds, central auditory processing, and ego strength), the reverse is true for others (i.e., social interaction and satisfaction with income). Age-specific sociodemographic burdens that may interfere with hearing loss management were noted. New psychosocial data are revealed against which women and men with impaired hearing may be compared.

Cognitive effects in dichotic speech testing in elderly persons

OBJECTIVE

To study the effect of chronologic age on central auditory functions using dichotic speech tests and to study whether and how the age effect in dichotic listening is related to cognitive ability.

DESIGN

Dichotic speech tests and cognitive tests were performed on 30 bilaterally hearing-impaired subjects, with a pure-tone average better than 50 dB HL. They were between 42 and 84 yr of age and were divided into an older and a younger group comprising 15 subjects each. The dichotic test material were digits, low-redundancy sentences and consonant-vowel syllables. The subjects reported stimuli heard in both ears (free report) or in one ear (directed report to left or right ear). The cognitive test battery comprised tests focusing on short-term memory, verbal information-processing speed and phonologic processing.

RESULTS

A decreased overall performance in all dichotic speech tests was observed in the older group. In the syllable test the older subjects showed poorer results when focusing on the stimuli heard in the left ear, as compared with when focusing on stimuli heard in the right ear, whereas the younger group showed almost equal results for left- and right ear-focusing conditions. An age effect was also seen in reaction times recorded in the cognitive tests and in the scores of the reading span test. These cognitive parameters correlate with the results of the dichotic test when focusing to the left, but not when focusing to the right in the directed report condition. In the free report condition the overall performance showed a high correlation with cognitive test parameters.

CONCLUSIONS

Effects of chronologic age in dichotic speech tests in the elderly have been verified. The degree of effect is dependent on test material, way of reporting and focusing condition. The different listening tasks in dichotic tests put different demands on cognitive ability shown by a varying degree of correlations between cognitive function and dichotic test parameters. Also, the results indicate a strong connection between age-related cognitive decline in the elderly and problems to perceive stimuli presented to the left ear.

Effects of aging and gender on interhemispheric function

The ability of the two hemispheres of the brain to communicate with one another via the corpus callosum is important for a wide variety of sensory, motor, and cognitive functions, many of them communication related. Anatomical evidence suggests that aging results in structural changes in the corpus callosum and that the course over time of age-related changes in corpus callosum structure may depend on the gender of the individual. Further, it has been hypothesized that age- and gender-related changes in corpus callosum structure may result in concomitant decreased performance on tasks that are reliant on interhemispheric integrity. The purpose of this study was to investigate the effects of age and gender on auditory behavioral and visuomotor temporal indices of interhemispheric function across the life span of the normal adult. Results from 120 consistently right-handed adults from age 20 to 75 years revealed that interhemispheric integrity, as measured by dichotic listening, auditory temporal patterning, and visuomotor interhemispheric transfer time tasks, decreases relatively early in the adult life span (i.e., between the ages of 40 and 55 years) and shows no further decrease thereafter. In addition, the course over time of interhemispheric decline is different for men compared to women for some tasks. These findings suggest that decreased interhemispheric function may be a possible factor contributing to auditory and communication difficulties experienced by aging adults. In addition, results of this study hold implications for the clinical assessment of interhemispheric function in aging adults and for future research into the functional ramifications of decreased multimodality interhemispheric transfer.

Aging affects hemispheric asymmetry in the neural representation of speech sounds

Hemispheric asymmetries in the processing of elemental speech sounds appear to be critical for normal speech perception. This study investigated the effects of age on hemispheric asymmetry observed in the neurophysiological responses to speech stimuli in three groups of normal hearing, right-handed subjects: children (ages, 8-11 years), young adults (ages, 20-25 years), and older adults (ages > 55 years). Peak-to-peak response amplitudes of the auditory cortical P1-N1 complex obtained over right and left temporal lobes were examined to determine the degree of left/right asymmetry in the neurophysiological responses elicited by synthetic speech syllables in each of the three subject groups. In addition, mismatch negativity (MMN) responses, which are elicited by acoustic change, were obtained. Whereas children and young adults demonstrated larger P1-N1-evoked response amplitudes over the left temporal lobe than over the right, responses from elderly subjects were symmetrical. In contrast, MMN responses, which reflect an echoic memory process, were symmetrical in all subject groups. The differences observed in the neurophysiological responses were accompanied by a finding of significantly poorer ability to discriminate speech syllables involving rapid spectrotemporal changes in the older adult group. This study demonstrates a biological, age-related change in the neural representation of basic speech sounds and suggests one possible underlying mechanism for the speech perception difficulties exhibited by aging adults. Furthermore, results of this study support previous findings suggesting a dissociation between neural mechanisms underlying those processes that reflect the basic representation of sound structure and those that represent auditory echoic memory and stimulus change.

Older adult performance on the Communication Profile for the Hearing Impaired: gender difference

Gender difference in auditory function with age is well documented. However, little is known about the influence of interacting sensory, psycho-social, and economic variables on adjustment to hearing loss. Adjustment to acquired, mild-to-moderate hearing loss by advantaged older women and men was examined using the Communication Profile for the Hearing Impaired (CPHI) (Demorest & Erdman, 1987). Correlational analyses revealed relationships between scales to be similar for women and men. Controlling for socio-demographic and hearing variables, group responses for the majority of CPHI scales did not differ significantly. Six scales differed significantly, and those results are discussed. When compared to men, women assigned greater importance to effective social communication, were more likely to use nonverbal communication strategies, reported greater anger and stress, and reported greater problem awareness and less denial associated with hearing loss. The CPHI is a useful tool for specifying parameters of perceived communication handicap for both older men and women. Findings underscore the need to consider gender-specific self-assessment of communication and personal adjustment in clinical management of older adults with age-related hearing loss.

Dichotic speech tests

When central auditory dysfunction is present, ability to understand speech in difficult listening situations can be affected. To study this phenomenon, dichotic speech tests were performed with test material in the Swedish language. Digits, spondees, sentences and consonant-vowel syllables were used as stimuli and the reporting was free or directed. The test material was recorded on CD. The study includes a normal group of 30 people in three different age categories; 11 years, 23-27 years and 67-70 years. It also includes two different groups of subjects with suspected central auditory lesions; 11 children with reading and writing difficulties and 4 adults earlier exposed to organic solvents. The results from the normal group do not show any differences in performance due to age. The children with reading and writing difficulties show a significant deviation for one test with digits and one test with syllables. Three of the four adults exposed to solvents show a significant deviation from the normal group.

Age-related alteration in processing of temporal sound features in the auditory midbrain of the CBA mouse

The perception of complex sounds, such as speech and animal vocalizations, requires the central auditory system to analyze rapid, ongoing fluctuations in sound frequency and intensity. A decline in temporal acuity has been identified as one component of age-related hearing loss. The detection of short, silent gaps is thought to reflect an important fundamental dimension of temporal resolution. In this study we compared the neural response elicited by silent gaps imbedded in noise of single neurons in the inferior colliculus (IC) of young and old CBA mice. IC neurons were classified by their temporal discharge patterns. Phasic units, which accounted for the majority of response types encountered, tended to have the shortest minimal gap thresholds (MGTs), regardless of age. We report three age-related changes in neural processing of silent gaps. First, although the shortest MGTs (1-2 msec) were observed in phasic units from both young and old animals, the number of neurons exhibiting the shortest MGTs was much lower in old mice, regardless of the presentation level. Second, in the majority of phasic units, recovery of response to the stimulus after the silent gap was of a lower magnitude and much slower in units from old mice. Finally, the neuronal map representing response latency versus best frequency was found to be altered in the old IC. These results demonstrate a central auditory system correlate for age-related decline in temporal processing at the level of the auditory midbrain.

[Is the afferent auditory message modulated by the cortex?]

An eventual modulation of the afferent auditory message by the cortex is the subject of this study. To test this hypothesis, clicks (10 Hz, 100 microseconds) of white noise of 40 and 70 dB Hl were sent alternatively into the ears of normally hearing volunteers, while the brainstem evoked potentials were recorded. The subjects were asked to focus or relax their attention on one or other ear. Thirty subjects aged less than 25 years (15 men and 15 women) with normal hearing level, were split into two groups. The first group was asked to focus first on the more strongly stimulated ear (70 dB), the second group on the more weakly stimulated one (40 dB). Each subject received (1) without any instruction about attention: 40 dB on the left ear (L), 70 dB on the right ear (R); 40 dB then 70 dB bilateral; (2) 2 runs with 40 dB on the L and 70 dB on the R focussing on the most or less strongly stimulated ear; (3) a run without instruction with 70 dB on the L and 40 dB on the R, and (4) two runs with 70 dB on the L and 40 dB on the R focussing enough on the more or less strongly stimulated ear. On the evoked potentials simultaneously recorded, amplitudes and latencies of the pikes were measured and compared. From these experiments, the following elements were obtained. (1) The measured potentials were always caused by ipsilateral stimuli. (2) Focussing on left or right ear was not equivalent. (3) A gender difference appeared in the brainstem auditory responses. (4) Preferential attention paid to the left ear was more efficient than to the right one. (5) Attention can alter the whole nervous pathway with considerable lengthening of O-I, O-III, O-V, III-V, I-V but not I-III latencies. The III wave amplitude generally decreased on the side where attention was focussed while V waves seemed not to vary. These first results indicate that a cortico-efferent pathway stimulated by the attention plays a role in the auditory responses modifying the afferent message. These effects were not the same among the side focussing attention and among sex.

Age-related and gender-related changes in monaural speech recognition

Previous studies of older listeners suggest age-related declines in speech recognition. However, the interpretation of these results is not straightforward because auditory thresholds, which account for the largest proportion of the variance in speech-recognition scores, also vary considerably with age. Here, effects of age, gender, and auditory thresholds on several measures of speech recognition were assessed for a large sample of individuals enrolled in a longitudinal study of age-related hearing loss. Participants ranged in age from 55-84 years. They were evaluated with a battery of conventional audiometric measures and speech-recognition materials, including NU-6 monosyllabic words, Synthetic Sentence Identification sentences, and high-context and low-context sentences from the Speech Perception in Noise test. Two analyses were conducted to assure that changes in speech-recognition scores with age were examined independently of age-related changes in auditory thresholds. In the first analysis, no significant differences in speech recognition were observed for individuals in three age groups (55-64, 65-74, 75-84 years) who were selected so that average puretone thresholds for the groups were within 5 dB. In the second analysis, using partial correlations to adjust both score and age for their association with average thresholds, significant declines with age were observed for males in maximum word recognition, maximum synthetic sentence identification, and keyword recognition in high-context sentences. For females, no significant changes in speech recognition with age were observed for any test.

Audiological correlates of speech understanding deficits in elderly listeners with mild-to-moderate hearing loss. I. Age and lateral asymmetry effects

OBJECTIVE

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?

DESIGN

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

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.

CONCLUSIONS

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.

Hearing in the elderly > or = 80 years of age. Prevalence of problems and sensitivity

This article is part of an epidemiological study on hearing in an urban population > or = 80 years of age, and concentrates on the prevalence of hearing problems and hearing sensitivity as a function of age and gender. Prior to the study, 2915 residents aged 80+ from the Valby area in Copenhagen were selected for investigation and subdivided into two groups. The first group, comprising n = 859 subjects previously provided with HA, and the second group, resulting from an invitation mailed to n = 565 subjects, were matched according to the age and gender distribution of the population, i.e. 24% males and 76% females. Among these, only 41% at a median age of 84 years, range 80-96, accepted the invitation, being significantly younger than the non-attenders. The estimated prevalence of self, reported hearing problems ranged between 33 and 66%, increasing with increasing age. Significant differences were found in the hearing sensitivity as a function of gender, i.e. the hearing in the low-frequency area < 1 kHz is better, whereas the hearing sensitivity at > 2 kHz is significantly worse in males compared with females. The speech recognition score (SRS) was significantly higher in females compared with males, and a comparison between ears supports the finding that the right ear speech recognition score is better than the left. The study demonstrates the difficulties in obtaining reliable epidemiological data on the hearing in the elderly > or = 80 years, which represents an obstacle for the planning of appropriate hearing health services directed towards this age group, and collaborative studies are suggested in order to accumulate more knowledge.

Assessing the cognitive demands of speech listening for people with hearing losses

OBJECTIVE

Measures of listening effort can provide a useful complement to measures of listening performance. The purpose of the present study was to measure the effort required of hearing-impaired subjects when they listen to speech.

METHOD

Our subjects performed two tasks simultaneously: a speech task, which took the form of listening to connected discourse; and a digit-memorization task, which competed with the speech task for cognitive resources. Changes in speech-listening effort altered the distribution of resources between the two tasks and modulated memory performance. In two experiments, this dual-task test was given to individuals with congenital/early-onset hearing loss or with presbyacusic hearing loss. We first asked whether they could perform the dual tasks at reasonable levels. If they could, we then asked what their performance revealed about the effortfulness of speech listening, compared with the effort required of normally hearing control subjects.

RESULTS

We found the dual-task test to be broadly accessible to hearing-impaired persons. We also found evidence that speech listening was abnormally effortful for both hearing-impaired groups.

CONCLUSIONS

These findings encourage further study of attentional and other cognitive factors that accompany speech listening by the hearing impaired.