ENHANCE: a comparative prospective longitudinal study of cognitive outcomes after 3 years of hearing aid use in older adults.

Background: With an aging population, the prevalence of hearing loss and dementia are increasing rapidly. Hearing loss is currently considered the largest potentially modifiable risk factor for dementia. The effect of hearing interventions on cognitive function should therefore be investigated, as if effective, these may be successfully implemented to modify cognitive outcomes for older adults with hearing loss. Methods: This prospective longitudinal observational cohort study compared outcomes of a convenience sample of prospectively recruited first-time hearing aid users without dementia from an audiology center with those of community-living older adults participating in a large prospective longitudinal cohort study with/without hearing loss and/or hearing aids. All participants were assessed at baseline, 18 months, and 36 months using the same measures. Results: Participants were 160 audiology clinic patients (48.8% female patient; mean age 73.5 years) with mild-severe hearing loss, fitted with hearing aids at baseline, and 102 participants of the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Aging (AIBL) (55.9% female patient; mean age 74.5 years). 18- and 36-month outcomes of subsets of the first participants to reach these points and complete the cognition assessment to date are compared. Primary comparative analysis showed cognitive stability for the hearing aid group while the AIBL group declined on working memory, visual attention, and psychomotor function. There was a non-significant trend for decline in visual learning for the AIBL group versus no decline for the hearing aid group. The hearing aid group showed significant decline on only 1 subtest and at a significantly slower rate than for the AIBL participants (p < 0.05). When education effects on cognitive trajectory were controlled, the HA group still performed significantly better on visual attention and psychomotor function (lower educated participants only) compared to the AIBL group but not on working memory or visual learning. Physical activity had no effect on cognitive performance trajectory. Conclusion: Hearing aid users demonstrated significantly better cognitive performance to 3 years post-fitting, suggesting that hearing intervention may delay cognitive decline/dementia onset in older adults. Further studies using appropriate measures of cognition, hearing, and device use, with longer follow-up, are required.

No Influence of Age-Related Hearing Loss on Brain Amyloid-ß.

BACKGROUND: Hearing loss is independently associated with a faster rate of cognitive decline in older adults and has been identified as a modifiable risk factor for dementia. The mechanism for this association is unknown, and there has been limited exploration of potential casual pathology. OBJECTIVE: Our objective was to investigate whether there was an association between degree of audiometrically measured hearing loss (HL) and brain amyloid-ß (Aß) in a pre-clinical sample. METHODS: Participants of the Australian Imaging and Biomarker Longitudinal Study (AIBL; n = 143) underwent positron emission tomography (PET) imaging and objective measurement of hearing thresholds within 5 years of imaging, as well as cognitive assessment within 2 years of imaging in this observational cohort study. RESULTS: With one exception, study participants who had cognitive assessments within 2 years of their PET imaging (n = 113) were classified as having normal cognition. There was no association between cognitive scores and degree of hearing loss, or between cognitive scores and Aß load. No association between HL and Aß load was found once age was controlled for. As previously reported, positive Apolipoprotein E4 (APOE4) carrier status increased the risk of being Aß positive (p = 0.002). CONCLUSION: Degree of HL was not associated with positive Aß status.

Social Development in Children With Early Cochlear Implants: Normative Comparisons and Predictive Factors, Including Bilateral Implantation.

OBJECTIVES: There are mixed results regarding psychosocial development in children with cochlear implants (CIs) compared with children with normal hearing (NH), and the effect of bilateral CIs has not yet been investigated. This study aimed to investigate whether social development differed between NH children and those with early CIs, and to identify new predictors of psychosocial development in children with early CIs. DESIGN: The psychosocial development, cognitive and language abilities of 159 children were measured as part of a longitudinal outcomes study of children with CIs. Parental involvement was also assessed. RESULTS: The children in this study did not differ significantly from their peers with NH in terms of their psychosocial development, except with regard to Prosocial Behavior, with parents reporting significantly poorer development in this area. Having bilateral CIs predicted significantly fewer difficulties with psychosocial development, with earlier age at implantation increasing the effect size of the second CI for Emotional Symptoms and Peer Problems. Receptive language ability, higher parent education, later birth order, high parent involvement, and female gender predicted significantly fewer parent reports of psychosocial problems. Higher child cognitive ability and greater screen time predicted significantly greater reported psychosocial difficulties. Marginal effects modeling quantified the effects of changes in the predictive factors examined. CONCLUSIONS: Psychosocial development in these children with early CIs was found to be similar to that for peers with NH, with the exception of delayed Prosocial Behavior development. Having bilateral CIs predicted significantly better emotional outcomes. A number of new predictive factors were found for psychosocial development. The results of the marginal effects modeling should be shared with parents and professionals to increase their understanding of the impact of changes in predictive factors, particularly in terms of their own contribution to psychosocial outcomes for children with CIs.

Investigation of Electrical Stimulation Levels Over 8 to 10 Years Postimplantation for a Large Cohort of Adults Using Cochlear Implants.

OBJECTIVES: This study examined electrical stimulation levels over 8 to 10 years postimplantation in adult Nucleus implant users. The first aim was to investigate long-term trends and amount of change in electrical stimulation levels for each of four electrode array segments. The second aim was to determine long-term trends and amount of change for particular participants who previously showed greater change (i.e., >20% of dynamic range [DR]) in each of the threshold (T) and comfort (C) levels within the first 3 to 6 months postimplantation. The third aim was to determine whether demographic characteristics were predictive of the long-term trends and amount of change in each of the T and C levels. DESIGN: For 128 adults implanted with Nucleus implants, T levels, C levels, and DR were extracted for the following postimplant time points: 6, 9, 12, 18, 24, 48, 72, 96, and 120 months. For each time point, the mean T levels, C levels, and DR were calculated for each of four electrode array segments. For each participant, regression analyses were conducted for each of the levels and DR, separately for each of the four electrode array segments. Proportions of participants with and without statistically significant trends were identified, and the amount of change was determined for all participants. RESULTS: No significant differences in trends and amount of change were evident across segments for either of the T or C levels. On average across the four segments, 42% of participants showed nonsignificant trends in each of the T and C levels; 24% and 18% of the participants showed a significant trend only in C levels or only in T levels, respectively. Only 16% of the participants showed a significant trend in both T and C levels. Separately, 73% of the participants showed a nonsignificant trend in DR. In terms of current levels (CLs), the mean amount of change over 10 years for all participants was 10.4 (SD = 8.2) and 10.8 (SD = 9.8) for T and C levels, respectively. For both T and C levels, approximately 95% of the participants showed <25 CLs of change over the 10 years. For both T and C levels, at least 75% of the participants showed less than 6% change each year as a function of their average DR across the 8 to 10 years. For the participants who were previously reported to show >20% change in levels as a function of DR in the first 3 to 6 months postimplantation, nonsignificant long-term trend in levels was shown for 70% of these participants over the first 8 to 10 years postimplantation. Etiology, onset of hearing loss, and age at implantation were not significant factors in predicting change in levels. Duration of hearing loss and hearing aid use before implantation were both predictive of long-term change in T and C levels, respectively. In terms of the amount of change in CLs, both these factors showed a very small amount of change in CLs. CONCLUSIONS: The majority of adults using Nucleus implants showed a nonsignificant trend in T levels, C levels, and DR over 8 to 10 years postimplantation. The present study provides strong evidence that only a small amount of change in levels should be expected for most adults from 6 months out to 10 years postimplantation. A large proportion of the subgroup of participants who previously showed more change in the first 3 to 6 months showed consistent long-term results with the overall group. The trends in levels and the amount of change in levels in the long term were not significantly associated with the demographic characteristics investigated. For implant users with consistent levels over a number of sessions after the first 6 months postimplantation, the frequency of programming in the long term can be reduced. The translation of the findings from the present study into clinical practice will enable more efficient programming services to be provided to implant users in the long term.

Categorical loudness scaling in cochlear implant recipients.

OBJECTIVE: This study investigated categorical loudness scaling in a large group of cochlear implant (CI) recipients. DESIGN: Categorical loudness was measured for individually determined sets of current amplitudes on apical, mid and basal electrodes of the Nucleus array. STUDY SAMPLE: Thirty adult subjects implanted with the Nucleus CI. RESULTS: Subjects were generally reliable in categorical loudness scaling. As expected, current levels eliciting the same loudness categories differed across subjects and electrodes in many cases. After scaling the electric levels to remove differences in dynamic ranges across subjects and electrodes, the across-subject loudness functions for the three electrodes were very similar. CONCLUSIONS: Scaled electric current to remove differences in dynamic range, as implemented in the Nucleus processor, ensures uniform loudness across the array and CI recipients. The results also showed that categorical loudness scaling for electric stimulation was similar to that for acoustic stimulation in normal hearing subjects. These findings could be used as a guide for aligning electric and acoustic loudness in CI recipients with contralateral hearing.

The Change in Electrical Stimulation Levels During 24 Months Postimplantation for a Large Cohort of Adults Using the Nucleus® Cochlear Implant.

OBJECTIVES: To examine electrical stimulation data over 24 months postimplantation in adult implant users. The first aim was to calculate mean T and C levels for seven time points, for four cochlear segments, and two array types. The second aim was to (a) analyze the degree of change in each of the T and C levels as a function of dynamic range for six consecutive time point comparisons, for the four segments, and (b) to determine the proportion of participants with an acceptable degree of change. The third aim was to examine relationships between demographic factors and degree of change. DESIGN: T levels, C levels, and dynamic ranges were extracted for 680 adults using Nucleus implants for the following postimplant time points: 2-, 3-, 6-, 9-, 12-, 18-, and 24-month. For each time point, mean levels were calculated for the four segments. The degree of change in each of the levels was analyzed for six consecutive time point comparisons. The criterion for an acceptable degree of change was ≤20% of DR. RESULTS: Mean T level was significantly lower for the 2-month time point compared with all time points after the 3-month time point. Mean C level was significantly lower for the 2- and 3-month time points compared with all other time points. Mean T level was significantly lower for the apical compared with all other segments and for the lower-basal compared with the upper-basal segment. Mean C level was significantly different across all four segments. Mean C level for the basal segments was 4 CLs higher for the perimodiolar array compared with the straight array. No significant differences were evident for the mean degree of change between consecutive time point comparisons. For all segments, approximately 65 to 75% of the participants showed an average acceptable degree of change in levels from the 3- to 6-month comparison. The mean degree of change in T levels was significantly greater for the basal segments compared with all other segments. The mean degree of change in levels was significantly greater for the otosclerosis group compared with all other groups, and for the prelingual onset of deafness group compared with the postlingual group. CONCLUSION: Given the very large cohort, this study provides evidence for the mean levels and the degree of change in these levels that should be expected for four segments in the first 24 months postimplantation for adults using Nucleus implants. The mean T and C levels were consistent after the 3- and 6-month time points postimplant, respectively. The degree of change was variable between individuals. For each segment, however, a large percentage of participants showed an average change of ≤20% in each of the T and C levels from the 3- to 6-month comparison. Given the large degree of change in levels for some groups, the results provide strong evidence in favor of frequent monitoring of levels in the first 24 months postimplantation for patients with otosclerosis, prelingual onset of deafness, and those who exhibit >20% change in levels after 3 months postimplantation.

Effects of Threshold Adjustment on Speech Perception in Nucleus Cochlear Implant Recipients.

OBJECTIVE: The objective of this study was to investigate the impact of using smaller and larger electric dynamic ranges on speech perception, aided thresholds, and subjective preference in cochlear implant (CI) subjects with the Nucleus device. DESIGN: Data were collected from 19 adults using the Nucleus CI system. Current levels (CLs) used to set threshold stimulation levels (T-levels) were set above or below the measured hearing thresholds to create smaller or larger electric output dynamic ranges, respectively, whereas the upper stimulation level (C-level) was fixed. The base (unadjusted) condition was compared against two conditions with higher T-levels (compression), by 30% and 60% of the measured hearing dynamic range, and three conditions with lower T-levels (expansion), by 30%, 60%, and 90% of the measured hearing dynamic range. For each subject, the clinical CL units were adjusted on each electrode to achieve these conditions. The slow-acting dynamic acoustic gains of ADRO and Autosensitivity™ were enabled. Consonant-nucleus-consonant (CNC) word scores were measured in quiet at 50 dB and 60 dB SPL presentation levels. The signal-to-noise ratios (SNRs) for 50% understanding of sentences in noise were measured for sentences presented at 55 dB and 65 dB SPL in 4-talker babble noise. Free-field aided thresholds were measured at octave frequencies using frequency-modulated (warble) tones. Thirteen of the 19 subjects had take-home experience with the base and experimental conditions and provided subjective feedback via a questionnaire. RESULTS: There were no significant effects of 30% expansion and 30% compression of the electric dynamic range on scores for words in quiet and SNRs for sentences in noise, at the two presentation levels. There was a significant decrement in scores for words in quiet for 60% and 90% expansion compared with the base condition at the 50 dB and 60 dB SPL presentation levels. The score decrement was much less at 60 dB SPL. For the 50 dB SPL presentation level, the decrements in word scores at 60% and 90% expansion were linearly related to the reduction in CL units required to achieve these experimental conditions, with a greater decrement in scores for a larger CL change. There was a significant increase in SNR for sentences in noise for 60% compression compared with the base condition at the 55 dB and 65 dB SPL presentation levels. There was also a significant increase in SNR for sentences at the 55 dB SPL presentation level for 90% expansion. Aided thresholds were significantly elevated for the three expansion conditions compared with the base condition, although the mean elevation at 30% expansion was only 4 dB. The questionnaire results showed no clear preference for any condition; however, subjects reported a reduced preference for the extreme compression (60%) and expansion (90%) conditions. CONCLUSIONS: The results showed that CI subjects using the Nucleus sound processor had no significant change in performance or preference for adjustments in T-levels by ±30% of the hearing dynamic range. In quiet, speech perception scores were reduced for the more marked expansion (60% and 90%) conditions, whereas in noise, performance was poorer for the highest compression (60%) condition. Across subjects, the decrement in scores for words at 50 dB SPL for the 60% and 90% expansion conditions was related to the changes in CL units required for these conditions, with greater decrements for larger changes in levels.

Electrophysiological spread of excitation and pitch perception for dual and single electrodes using the Nucleus Freedom cochlear implant.

OBJECTIVES: The first objective of the study was to determine whether there were any consistent differences in the electrophysiological spread of excitation (SOE) function, as measured using the electrically evoked compound action potential (ECAP), between dual and single electrode stimulation with the Nucleus Freedom cochlear implant system. Dual electrode stimulation is produced by electrically coupling two adjacent single electrodes. The second objective was to determine whether there were any relationships between the SOE functions and psychophysically measured pitch ranking of dual and single electrodes. DESIGN: Nine adult cochlear implant subjects participated in the study. ECAPs for dual and single electrode stimulation were measured using the forward masking paradigm, as also used in the Neural Response Telemetry (NRT) software with the Nucleus implant. Research software was used to generate the dual and single electrode stimuli and record the ECAPs. Spread of excitations (SOEs) were measured on a dual electrode and the two adjacent single electrodes, at three positions on the array: apical, mid, and basal. Compared were the ECAP amplitudes at the peak of the SOE functions, the widths of the scaled SOE functions at the 75% point, and the electrode positions at the peak of the SOE function and at the 75%, 50%, and 25% points on apical and basal sides of the scaled functions. Pitch ranking was measured for the same sets of dual and single electrodes. A two-alternative forced choice procedure was used, with the electrodes in each set paired with each other as AB and BA pairs. The subject indicated which of the two stimuli had the higher pitch. RESULTS: Dual electrode SOEs could be successfully obtained using the same methods as used to measure single electrode SOEs. The shapes of the dual and single electrodes SOEs were similar. There was a trend of a higher ECAP amplitude for the dual electrode at the peak of the SOE function, but this was only significant for two comparisons at the apical and basal positions. There were no significant differences in the SOE widths between dual and single electrodes. The electrodes at the peak of the SOE function and on the apical and basal sides of the function at the 75% position were, in most cases, tonotopically ordered. At the 50% and 25% positions, there were fewer significant differences between the dual and single electrodes The pitch ranking results showed that in 74% of cases, the single and dual electrodes at each position were successfully ranked in the expected tonotopic order. There were no statistically significant correlations between the pitch ranking results and the ordering of electrodes on the SOE functions. CONCLUSIONS: Dual electrode stimulation produced similar SOE functions as single electrode stimulation. A tonotopic ordering of electrodes at the peak of the SOE and on the sides of the functions was found, but this was not statistically related to the pitch ranking results. SUMMARY: Electrophysiological spread of neural excitation (SOE) and pitch perception using dual and single electrodes was investigated in nine subjects using the Nucleus Freedom cochlear implant. Dual electrodes are produced by electrically coupling two adjacent single electrodes. The dual and single electrodes SOEs were similar in shape. Higher electrophysiological response amplitudes were generally found for the dual electrodes. There were no differences in SOE widths between dual and single electrodes. In three quarters of cases, dual and single electrodes were successfully pitch ranked in the expected tonotopic order. No significant relationships between pitch ranking and the SOE functions were found.

The development of the Nucleus Freedom Cochlear implant system.

Cochlear Limited (Cochlear) released the fourth-generation cochlear implant system, Nucleus Freedom, in 2005. Freedom is based on 25 years of experience in cochlear implant research and development and incorporates advances in medicine, implantable materials, electronic technology, and sound coding. This article presents the development of Cochlear's implant systems, with an overview of the first 3 generations, and details of the Freedom system: the CI24RE receiver-stimulator, the Contour Advance electrode, the modular Freedom processor, the available speech coding strategies, the input processing options of Smart Sound to improve the signal before coding as electrical signals, and the programming software. Preliminary results from multicenter studies with the Freedom system are reported, demonstrating better levels of performance compared with the previous systems. The final section presents the most recent implant reliability data, with the early findings at 18 months showing improved reliability of the Freedom implant compared with the earlier Nucleus 3 System. Also reported are some of the findings of Cochlear's collaborative research programs to improve recipient outcomes. Included are studies showing the benefits from bilateral implants, electroacoustic stimulation using an ipsilateral and/or contralateral hearing aid, advanced speech coding, and streamlined speech processor programming.

A psychophysical forward masking comparison of longitudinal spread of neural excitation in the Contour and straight Nucleus electrode arrays.

The objective of the study was to compare the widths of forward masking profiles in subjects implanted with the Nucleus 24 Contour or straight electrode array. The Contour array is typically positioned closer to the modiolus than the straight array. Subjects were fourteen postlingually hearing-impaired adults with severe-profound hearing loss, seven used the Contour array and seven used the straight array. Forward masking profiles were measured at three positions along the array (apical, mid, and basal) using maskers at the 15% loudness level. It was hypothesized that masking profile widths would be more sensitive to differences in distance from the neural structures using low-level maskers. Masking width was calculated at the 50% point of the masking peak amplitude. There were no significant differences in masking widths between Contour and straight array subject groups. Current levels for hearing thresholds and maximum comfortable listening levels were significantly lower for the Contour array subjects.

Dual electrode stimulation using the nucleus CI24RE cochlear implant: electrode impedance and pitch ranking studies.

OBJECTIVE: The first aim of the study was to determine the reduction in electrode impedances using dual electrode stimulation compared with single electrode stimulation in the new Nucleus CI24RE receiver-stimulator. The CI24RE is connected to the Nucleus 22-electrode intracochlear array. Dual electrode stimulation is produced by electrically coupling two adjacent single electrodes. The second aim was to determine whether dual electrode stimulation produced pitch percepts that were intermediate to the pitch of the two adjacent single electrodes. DESIGN: Eight postlingually hearing-impaired adults with severe to profound loss, implanted with the CI24RE, participated in the study. Electrode impedances were measured by using the standard telemetry function of the system. A pitch ranking task was used to measure pitch for dual and single electrodes. Seven sets of three electrodes along the electrode array were tested. Each set of electrodes consisted of a dual electrode and the two adjacent single electrodes. Pitch ranking was measured using a two-alternative forced choice procedure, with the three electrodes in each set paired with each other as AB and BA pairs. The subject indicated which of the two stimuli had the higher pitch. Random variation in current level was used to remove any loudness cues. RESULTS: The average electrode impedance was 38.6% lower for dual electrodes compared with single electrodes. Three subjects were able to successfully rank the three electrodes in each set in the expected tonotopic order for all seven sets of electrodes along the array. Three other subjects were able to rank sets of electrodes in the tonotopic order for most of the tested positions on the array. The remaining two subjects gave more variable pitch ranking across positions along the array, although successful tonotopic ranking was demonstrated for several sets of electrodes. CONCLUSIONS: Dual electrode stimulation with the CI24RE receiver-stimulator produced systematically lower electrode impedances and was capable of producing pitch percepts that were intermediate to those produced by the corresponding adjacent single electrodes. This makes available up to 43 channels of stimulation from 22 single electrodes.

Cognitive processing in children using cochlear implants: the relationship between visual memory, attention, and executive functions and developing language skills.

We performed this study to determine whether children using a cochlear implant performed differently from age- and gender-matched hearing aid users on 8 neuropsychological measures of visual memory, attention, and executive functioning. The study also examined whether differences in cognitive skills could account for some of the observed variance in speech perception, vocabulary, and language abilities of hearing-impaired children. In contrast to previous studies, our results revealed no significant cognitive differences between children who use a cochlear implant and children who use hearing aids. Partial correlation analysis indicated that the children's visual memory skills, ie, their recognition memory, delayed recall, and paired associative learning memory skills, correlated significantly with their language skills. When examined at a significance level of .01, attention and executive functioning skills did not relate to the children's developing speech perception, vocabulary, or language skills. The results suggested that differences in visual memory skills may account for some of the variance seen in the language abilities of children using implants and children using hearing aids.