Daniel McDermott

A 5-year prospective study of diabetes and hearing loss in a veteran population.

Hypothesis: Veterans with diabetes will have significantly greater hearing loss than nondiabetic veterans. Background: The association between diabetes and hearing loss remains unclear despite the volume of research that has been devoted to the question. Often, differences in hearing thresholds between diabetic and nondiabetic patients are confounded by age and noise exposure. Methods: In this 5-year prospective study, 342 diabetic veterans and 352 nondiabetic veterans from the Portland VA Medical Center in Oregon were tested on a variety of audiometric measures, including pure-tone thresholds. Results: Age and noise exposure were accounted for in the analyses. There was a trend toward greater hearing loss in diabetic patients 60 years of age and younger across the frequency range. These differences were statistically significant only in the highest frequencies tested (10, 12.5, 14, and 16 kHz). The effects of both diabetes and noise exposure on high-frequency hearing thresholds were dependent on age. For patients older than 60 years, the mean thresholds were not significantly different. Conclusion: These results suggest that diabetic patients 60 years old or younger may show early high-frequency hearing loss similar to early presbycusis. After age 60, difference in hearing loss between diabetic and nondiabetic patients was reduced.

Diabetes-related changes in hearing†

Determine the effects on hearing of diabetes mellitus (DM) severity.

Age-related changes in the auditory brainstem response

PURPOSE This cross-sectional study had two goals: (1) Identify and quantify the effects of aging on the auditory brainstem response (ABR); (2) Describe how click rate and hearing impairment modify effects of aging. RESEARCH DESIGN AND ANALYSIS: ABR measures were obtained from 131 predominately male Veteran participants aged 26 to 71 yr. Metrics analyzed include amplitude and latency for waves I, III, and V, and the I-V interpeak latency interval (IPI) at three repetition rates (11, 51, and 71 clicks/sec) using both polarities. In order to avoid confounding from missing data due to hearing impairment, participants had hearing thresholds <40 dB HL at 2 kHz and 70 dB HL at 4 kHz in at least one ear. Additionally, the median 2, 3, and 4 kHz pure tone threshold average (PTA2,3,4) for the sample, ∼17 dB HL, was used to delineate subgroups of better and worse hearing ears, and only the better hearing sample was modeled statistically. We modeled ABR responses using age, repetition rate, and PTA2,3,4 as covariates. Random effects were used to model correlation between the two ears of a subject and across repetition rates. Inferences regarding effects of aging on ABR measures at each rate were derived from the fitted model. Results were compared to data from subjects with poorer hearing. RESULTS Aging substantially diminished amplitudes of all of the principal ABR peaks, largely independent of any threshold differences within the group. For waves I and III, age-related amplitude decrements were greatest at a low (11/sec) click rate. At the 11/sec rate, the model-based mean wave III amplitude was significantly smaller in older compared with younger subjects even after adjusting for wave I amplitude. Aging also increased ABR peak latencies, with significant shifts limited to early waves. The I-V IPI did not change with age. For both younger and older subjects, increasing click presentation rate significantly decreased amplitudes of early peaks and prolonged latencies of later peaks, resulting in increased IPIs. Advanced age did not enhance effects of rate. Instead, the rate effect on wave I and III amplitudes was attenuated for the older subjects due to reduced peak amplitudes at lower click rates. Compared with model predictions from the sample of better hearing subjects, mean ABR amplitudes were diminished in the group with poorer hearing, and wave V latencies were prolonged. CONCLUSIONS In a sample of veterans, aging substantially reduced amplitudes of all principal ABR peaks, with significant latency shifts limited to waves I and III. Aging did not influence the I-V IPI even at high click rates, suggesting that the observed absolute latency changes associated with aging can be attributed to changes in auditory nerve input. In contrast, ABR amplitude changes with age are not adequately explained by changes in wave I. Results suggest that aging reduces the numbers and/or synchrony of contributing auditory nerve units. Results also support the concept that aging reduces the numbers, though perhaps not the synchrony, of central ABR generators.

Performance on Tests of Central Auditory Processing by Individuals Exposed to High-Intensity Blasts

Thirty-six blast-exposed patients and twenty-nine non-blast-exposed control subjects were tested on a battery of behavioral and electrophysiological tests that have been shown to be sensitive to central auditory processing deficits. Abnormal performance among the blast-exposed patients was assessed with reference to normative values established as the mean performance on each test by the control subjects plus or minus two standard deviations. Blast-exposed patients performed abnormally at rates significantly above that which would occur by chance on three of the behavioral tests of central auditory processing: the Gaps-In-Noise, Masking Level Difference, and Staggered Spondaic Words tests. The proportion of blast-exposed patients performing abnormally on a speech-in-noise test (Quick Speech-In-Noise) was also significantly above that expected by chance. These results suggest that, for some patients, blast exposure may lead to difficulties with hearing in complex auditory environments, even when peripheral hearing sensitivity is near normal limits.

Diabetes-related changes in auditory brainstem responses.

Determine effects on auditory brainstem response (ABR) of diabetes mellitus (DM) severity.

Implications of blast exposure for central auditory function: a review.

Auditory system functions, from peripheral sensitivity to central processing capacities, are all at risk from a blast event. Accurate encoding of auditory patterns in time, frequency, and space are required for a clear understanding of speech and accurate localization of sound sources in environments with background noise, multiple sound sources, and/or reverberation. Further work is needed to refine the battery of clinical tests sensitive to the sorts of central auditory dysfunction observed in individuals with blast exposure. Treatment options include low-gain hearing aids, remote-microphone technology, and auditory-training regimens, but clinical evidence does not yet exist for recommending one or more of these options. As this population ages, the natural aging process and other potential brain injuries (such as stroke and blunt trauma) may combine with blast-related brain changes to produce a population for which the current clinical diagnostic and treatment tools may prove inadequate. It is important to maintain an updated understanding of the scope of the issues present in this population and to continue to identify those solutions that can provide measurable improvements in the lives of Veterans who have been exposed to high-intensity blasts during the course of their military service.

Diabetes-Associated Changes in Cortical Auditory-Evoked Potentials in Relation to Normal Aging.

Objectives: (1) To characterize the influence of type 2 diabetes mellitus (DM) on cortical auditory-evoked potentials (CAEPs) separate from the effects of normal aging, and (2) to determine whether the disease-related effects are modified by insulin dependence. Design: A cross-sectional study was conducted in a large cohort of Veterans to investigate the relationships among type 2 DM, age, and CAEPs in randomly selected participants with (N = 108) and without (N = 114) the disease and who had no more than a moderate hearing loss. Participants with DM were classified as insulin-dependent (IDDM, N = 47) or noninsulin-dependent (NIDDM, N = 61). Other DM measures included concurrent serum glucose, HbA1c, and duration of disease. CAEPs were evoked using a passive homogeneous paradigm (single repeating stimulus) by suprathreshold tones presented to the right ear, left ear, or both ears. Outcome measures were adjusted for the pure-tone threshold average for frequencies of 0.5, 1, and 2 kHz and analyzed for differences in age effects between participant groups using multiple regression. Results: There is little variation across test ear conditions (left, right, binaural) on any CAEP peak in any of the groups. Among no-DM controls, P2 latency increases about 9 msec per decade of life. DM is associated with an additional delay in the P2 latency of 7 and 9 msec for the IDDM and NIDDM groups, respectively. Moreover, the slope of the function relating P2 latency with age is similar across participant groups and thus the DM effect appears constant across age. Effects on N1 latency are considerably weaker, with age effects of less than 4 msec per decade across all groups, and DM effects of only 2 (IDDM) or 3 msec (NIDDM). In the NIDDM group, the slope relating N1 latency to age is steeper relative to that observed for the no-DM group, providing some evidence of accelerated “aging” for this CAEP peak. DM does not substantially reduce N1–P2 amplitude and age relationships with N1–P2 amplitude are effectively absent. There is no association between pure-tone average at 0.5, 1, and 2 kHz and any aspect of CAEPs in this cohort. Conclusions: In a large cohort of Veterans, we found that type 2 DM is associated with prolonged N1 and P2 latencies regardless of whether insulin is required to manage the disease and independent of peripheral hearing thresholds. The DM-related effects on CAEP latencies are threefold greater for P2 compared with N1, and there is little support that at the cortical level, IDDM participants had poorer responses compared with NIDDM participants, although their responses were more variable. Overall, these results indicate that DM is associated with slowed preattentive neural conduction. Moreover, the observed 7 to 9 msec P2 latency delay due to DM is substantial compared with normal age changes in P2, which are 9 msec per decade of life in this cohort. Results also suggest that whereas N1 latency changes with age are more pronounced among individuals with DM versus without DM, there was no evidence for more rapid aging of P2 among patients with DM. Thus, the damage responsible for the major DM-related differences may occur early in the DM disease process. These cross-sectional results should be verified using a longitudinal study design.

Description, Normative Data, and Utility of the Hearing Aid Skills and Knowledge Test

BACKGROUND The ability to manage hearing aids is crucial for successful outcomes and for maintaining hearing aid use. It is therefore important to have a tool that can effectively identify which hearing aid management skills are lacking so that the audiologist can provide additional education and training on that skill. Such a tool can also provide useful quantitative data for researchers. PURPOSE To collect normative data (Experiment 1) and assess inter- and intrarater reliability (Experiment 2) for a hearing aid management assessment tool known as the Hearing Aid Skills and Knowledge (HASK) test. STUDY SAMPLE Two hundred thirty-six new hearing aid users recruited from the VA Portland Health Care System and 126 experienced hearing aid users recruited from the local Portland community participated in Experiment 1. The veteran participants were taking part in a larger hearing aid study, and the community participants were recruited at community events that took place around Portland, OR. Three clinical audiologists and two AuD students completing their fourth year externship participated in Experiment 2. DATA COLLECTION AND ANALYSIS In Experiment 1, HASK data were collected from the new hearing aid users at 4-8 wk and 6-8 mo after the fitting of their first pair of hearing aids, and from experienced users on a single occasion. In addition, self-reported hearing aid use, benefit, and satisfaction were assessed for all participants. The audiologists/students in Experiment 2 watched and independently scored videos of six individuals completing the HASK. Intraclass correlation coefficients (ICCs) across audiologists were computed for HASK scores. Three audiologists/students rated at least one video on two occasions to provide interrater reliability data. RESULTS Mean performance on the HASK was about 70% for knowledge and 80% for skills for both the new and experienced hearing aid users. Performance did not change among the new users between the 4-8 wk and 6-8 mo administration. The specific skills lacking were associated with advanced management abilities (cleaning and troubleshooting). Experiment 2 revealed ICCs for inter- and intrarater reliability for HASK to range from 0.76 to 0.94, showing acceptable to excellent reliability. CONCLUSIONS The HASK is a quick and easy test with good-to-excellent inter- and intrarater reliability. It can effectively identify which hearing aid management skills are lacking so that the audiologist can provide additional education and training on those skills. Data show performance is ∼70% for knowledge and 80% for skills and this does not change with hearing aid experience. The significant positive correlations between HASK scores and hearing aid use and satisfaction highlight the notion that ability to manage hearing aids successfully is integral to good hearing aid outcome.