Selective Loss of Calretinin-Poor Cochlear Afferent Nerve Fibers in Streptozotocin-Induced Hyperglycemic Mice

The Impact of Diabetes Mellitus on Sensorineural Hearing Loss: A Cross-Sectional Study in Eastern India

Objective Hearing loss as a comorbidity of type 2 diabetes mellitus (type 2 DM) is frequently overlooked by patients and healthcare professionals because of a lack of awareness. This cross-sectional study aims to investigate the impact of DM on sensorineural hearing loss (SNHL) in the population of Eastern India. The primary objectives are to assess the prevalence and severity of SNHL among individuals with DM, explore demographic and clinical factors associated with hearing impairment, and contribute valuable insights to the understanding of this relationship in a specific regional context. Methods An institutional-based cross-sectional study was conducted on 198 patients with type 2 DM. Of these, 46 patients were excluded based on exclusion criteria. All patients underwent detailed demographic and clinical assessments, including glycemic control, DM duration, and associated complications. Pure tone audiometry was used to evaluate hearing thresholds. Otoacoustic emission testing was performed to assess cochlear dysfunction. Results A high prevalence of SNHL (70.4%) was observed among the 152 participants meeting the inclusion criteria. Females exhibited a higher prevalence than males, and most participants experienced mild SNHL. Rural residence, lower socioeconomic status, and poor glycemic control were associated with increased SNHL. Significant associations were found between hearing loss severity and DM duration, glycosylated hemoglobin (HbA1c) levels, and complications. Among complications, a strong association was noted with diabetic neuropathy. No significant association was observed with the presence or absence of otoacoustic-emission. Conclusion This study reveals a substantial impact of DM on SNHL in Eastern India, emphasizing the importance of routine hearing assessments in diabetic populations. The findings contribute to regional understanding and have implications for targeted healthcare interventions and preventive strategies.

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.

Subtype maturation of spiral ganglion neurons

PURPOSE OF REVIEW

We review recent progress in the characterization of spiral ganglion neurons (SGNs), the afferent neurons that transmit sound information from mechanosensory hair cells in the inner ear to the central nervous system.

RECENT FINDINGS

Single-cell ribonucleic acid sequencing studies of murine SGNs have demonstrated that SGNs consist of molecularly distinct subtypes. The molecularly defined SGN subtypes likely correspond to SGN subtypes previously identified on the basis of physiological properties, although this has not been experimentally demonstrated. Subtype maturation is completed postnatally in an activity-dependent manner and is impaired in several models of hearing loss.

SUMMARY

The recent molecular studies open new avenues to rigorously test whether SGN subtypes are important for the encoding of different sound features and if they show differential vulnerability to genetic factors and environmental insults. This could have important implications for the development of therapeutic strategies to treat hearing loss.