Impairment of extra-high frequency auditory thresholds in subjects with elevated levels of fasting blood glucose

High-Frequency Audiovestibular Dysfunction in Long-Standing Diabetes Mellitus: Insights from a Cross-Sectional Study

This study investigates audiovestibular dysfunction in individuals with long-standing diabetes mellitus (DM). A cross-sectional study was conducted involving 100 patients (DM for ≥ 10 years) at the Department of E.N.T. in Prakash Institute of Medical Sciences and Research, Sangli, Maharashtra. A mean age of 43.09 years among patients, with 64% male and 36% female participants. Hearing loss was the most common complaint, affecting 46% of subjects, followed by vertigo in 23%. Pure tone audiometry revealed that 34% of patients had sensorineural hearing loss, with varying degrees of severity. Vestibular dysfunction was observed in 10% of cases. Correlation analysis indicated a significant positive relationship between the duration of DM and hearing thresholds at various frequencies, as well as with HbA1c levels. This suggests a worsening of hearing with longer DM duration and higher HbA1c levels. The prevalence of hearing impairment was higher at higher frequencies, with vestibular dysfunction also noted in a subset of patients.

Audiological profile of patients with type 2 diabetes mellitus

BACKGROUND

 South Africa shows a high prevalence of type 2 diabetes with reported association with auditory dysfunction.

OBJECTIVES

 To describe the audiological profile of adults with this metabolic condition.

METHOD

 Employing a descriptive research design, 35 individuals with type 2 diabetes, selected through purposive sampling, underwent a basic audiological assessment in addition to extended high-frequency (EHF) audiometry, distortion product otoacoustic emissions (DPOAE) testing and neurological auditory brainstem response (ABR) test.

RESULTS

 This study revealed a 31.4% prevalence of hearing loss with 81.8% being sensorineural in nature. Poor hearing thresholds were observed at 16 kHz (n = 19; 54.3%), 18 kHz (n = 24; 68.6%) and 20 kHz (n = 30; 85.7%) in the right ear and at 16 kHz (n = 20; 57.1%), 18 kHz (n = 24; 68.6%) and 20 kHz (n = 30; 85.7%) in the left ear. Absent DPOAEs were observed at 6 kHz (n = 20; 51.7%) and 8 kHz (n = 24; 68.6%) in the right ear and at 6 kHz (n = 17; 48.6%) and 8 kHz (n = 29; 82.9%) in the left ear, possibly indicating that type 2 diabetes specifically targets higher frequency hearing. The ABR results revealed a delayed absolute latency of wave III bilaterally (right ear -69%; left ear - 51%), suggesting an impact of this metabolic disease on retro-cochlear pathways.

CONCLUSION

 Hearing loss should be recognised as a comorbidity accompanying type 2 diabetes, which indicates the need for routine comprehensive audiological assessments to facilitate early detection and intervention.Contribution: The present findings have implications for audiology clinical protocols; diabetes related health policies and patient education.

Diabetes mellitus and hearing loss

Diabetes mellitus (DM) is a major disease threatening human health and its incidence is increasing year on year. As a chronic complication of DM, hearing loss mostly occurs undetectably. However, the mechanism of this diabetes-related hearing loss (DRHL) remains unclear and there is no effective clinical treatment. Studies of animal or human pathology show that DM causes damage to the blood vessels, spiral ganglion neurons, afferent nerve fibers, the organ of Corti, and the stria vascularis of the inner ear. In recent years, more advances in pathological research have revealed the possible mechanism of DRHL. In addition, a large number of clinical studies suggest that the duration and severity of DM are closely related to the incidence and severity of DRHL. This review focuses on the relationship between DM and hearing loss. The clinical audiological characteristics of diabetic patients, risk factors for DRHL, typical pathology, and potential interventions of DRHL are summarized. This will help reveal the pathogenesis and intervention approaches for DRHL.

Manganese in toenails is associated with hearing loss at high frequencies in humans

PURPOSE

Elevated hearing thresholds from high frequencies are known to be one of the hallmarks of age-related hearing loss. Our recent study showed accumulation of manganese (Mn) in inner ears resulting in acceleration of age-related hearing loss in mice orally exposed to Mn. However, there is no evidence showing an association between Mn in non-invasive biological samples and hearing loss in humans evaluated by pure tone audiometry (PTA). In this study, we evaluated Mn in non-invasive biological samples as a possible biomarker for hearing loss in humans.

MATERIALS AND METHODS

We determined hearing levels by PTA and Mn levels in toenails, hair and urine with an inductively coupled plasma mass spectrometer (ICP-MS) in 145 healthy subjects in Bangladesh.

RESULTS

Multivariable analyses showed that Mn levels in toenails, but not in hair and urine samples, were significantly associated with hearing loss at 8 kHz and 12 kHz. Moreover, our experimental study showed a significant correlation between Mn levels in inner ears and nails, but not hair, in mice orally exposed to Mn.

CONCLUSIONS

The results provide novel evidence that Mn in toenails is a possible biomarker for hearing loss at high frequencies in humans.