Diabetes Mellitus and the Effects on Auditory Processing

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Diabetes mellitus (DM) is a systemic disease that affects a number of sensory systems and is a major public health concern. A common, but under-recognized complication of DM is hearing difficulty. However, research on DM-related auditory deficits is relatively sparse. Recent data shows over a two-fold higher prevalence of hearing impairment in diabetic patients compared to non-diabetic individuals, further solidifying this strong association between diabetes and hearing loss. However, the nature of these hearing difficulties has not been clearly elucidated. In the present study, the auditory processing abilities of a group of adults (N = 9; mean age = 53.3) with type 2 DM was compared to an age matched control group (N = 9; mean age= 47.6). In addition, visual processing abilities of the participants were examined to determine if the hearing difficulties associated with DM were a function of a more global sensory deficit. The selection criteria for the DM group included age, duration of diabetes (> 5 years), and recent measures of diabetic control (hemoglobin A1C and blood sugar). Further, all participants in the test and control groups had a comprehensive hearing evaluation and had hearing (measured with pure tones 250-4000 Hz) within normal limits bilaterally. The following test measures were recorded. The Michigan Neuropathy Screening Instrument (MNSI) was administered to screen each subject for peripheral neuropathy symptoms. The Speech, Spatial & Qualities (SSQ12) questionnaire was administered to attain a measure of each individuals subjective hearing complaints. Subtle deficits in the peripheral auditory system were examined using (a) Extended high frequency audiometry, that assessed ultra high frequencies from 9000-16000 Hz bilaterally, (b) The Threshold Equalizing Noise (TEN) test, to assess for potential dead regions within the cochlea, and (c) Distortion product otoacoustic emissions (DPOAE) were collected bilaterally to assess frequency specific cochlear outer hair cell function. Higher-order auditory processing was examined with the Quick Speech in Noise Test (QuickSIN), the Listening in Spatial Noise test-Sentences (LiSN-S) and the Random gap detection, to measure temporal processing abilities. Further, the Text Reception Threshold Test (TRT) was employed to examine visual processing abilities. The results revealed that individuals with DM had significantly (a) Elevated high frequency (> 4 kHz) pure tone thresholds; (b) Increased self-reported hearing difficulties based on SSQ12 scores (c) Poorer spatial listening in noise skills based on LiSN results, (d) Lower DPOAE amplitudes for higher frequencies, and (e) Poorer temporal processing skills based on the average gap detection thresholds, when compared to the age-matched controls. These findings not only support the strong association between diabetes and hearing loss, they suggest that that even individuals with controlled diabetes potentially suffer with subclinical auditory processing deficits that may affect their quality of life. These findings have implications in the management of DM in the future. Further research is needed in order to determine clinically feasible means of evaluating DM subjects.


Johnson City, TN

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