Sudden hearing loss as a first complication of long-standing Type 1 diabetes mellitus: a case report

A review of the auditory-gut-brain axis

Hearing loss places a substantial burden on medical resources across the world and impacts quality of life for those affected. Further, it can occur peripherally and/or centrally. With many possible causes of hearing loss, there is scope for investigating the underlying mechanisms involved. Various signaling pathways connecting gut microbes and the brain (the gut-brain axis) have been identified and well established in a variety of diseases and disorders. However, the role of these pathways in providing links to other parts of the body has not been explored in much depth. Therefore, the aim of this review is to explore potential underlying mechanisms that connect the auditory system to the gut-brain axis. Using select keywords in PubMed, and additional hand-searching in google scholar, relevant studies were identified. In this review we summarize the key players in the auditory-gut-brain axis under four subheadings: anatomical, extracellular, immune and dietary. Firstly, we identify important anatomical structures in the auditory-gut-brain axis, particularly highlighting a direct connection provided by the vagus nerve. Leading on from this we discuss several extracellular signaling pathways which might connect the ear, gut and brain. A link is established between inflammatory responses in the ear and gut microbiome-altering interventions, highlighting a contribution of the immune system. Finally, we discuss the contribution of diet to the auditory-gut-brain axis. Based on the reviewed literature, we propose numerous possible key players connecting the auditory system to the gut-brain axis. In the future, a more thorough investigation of these key players in animal models and human research may provide insight and assist in developing effective interventions for treating hearing loss.

Otological and Visual Implications of Diabetes Mellitus in North Indian Population

The worldwide population of diabetic patients is increasing alarmingly with India claiming number one position. It causes irreversible damage to cochlear hair cells, vestibular apparatus, visual pathway, nephrons, nerves, if not checked in time. A total of 188 patients of diabetes mellitus were included in this prospective study. The patients underwent routine anamnesis, hearing handicap inventory and dizziness handicap inventory assessment along with clinical examination for audiological, vestibular, neurological and ophthalmological (fundoscopy) status. In our study a sensorineural hearing loss, retinopathy, neuropathy, vestibulopathy was seen in diabetic patients.

Susceptibility of Diabetic Mice to Noise Trauma

Diabetes can lead to many end-organ complications. However, the association between diabetes and hearing loss is not well understood. Here, we investigated the effect of noise exposure on diabetic mice compared with wild-type mice. Hearing threshold shifts, histopathologic changes in the cochlea, and inflammatory responses were evaluated over time. After noise exposure, more severe hearing threshold shifts, auditory hair cell loss, and synaptopathies were notable in diabetic mice compared with wild-type mice. Moreover, increased inflammatory responses and reactive oxygen species production were observed in the ears of diabetic mice. The results demonstrated that diabetic mice are more susceptible to noise trauma.

Risk of developing sudden sensorineural hearing loss in diabetic patients: a population-based cohort study

OBJECTIVES

To explore the risk of development of sudden sensorineural hearing loss (SSHL) among diabetes mellitus patients.

STUDY DESIGN

A retrospective cohort study.

SETTING

Population-based study of Taiwan National Health Insurance Research Database.

PATIENTS

Approximately 26,556 newly diagnosed diabetic patients and 26,556 comparison subjects without diabetes mellitus were selected from claims made during 2000 to 2004.

MAIN OUTCOME MEASURES

The incidence of sudden sensorineural hearing loss (SSHL) at the end of 2009 was determined.

RESULTS

The incidence of SSHL was 1.54-fold higher in the diabetic group compared with the nondiabetic group (1.29 versus 0.78 per 1,000 person-years), and using Cox proportional hazard regressions, the adjusted hazard ratio (HR) was 1.592 (95% confidence interval [CI], 1.295-1.957). The risk of developing SSHL increased substantially to an HR of 2.060 (95% CI, 1.051-4.037), for patients who required triple antidiabetic medication compared with diabetic patients treated with a single antidiabetic drug. An increased risk of developing SSHL, with adjusted HRs of 1.574 (95% CI, 1.091-2.271) and 2.842 (95% CI, 1.880-4.295), was observed in diabetic patients with newly diagnosed comorbidities of retinopathy or retinopathy combined with renal insufficiency, which are both expected to reflect the severity of diabetes.

CONCLUSION

Diabetes mellitus was significantly associated with an increased risk of developing SSHL. Coronary heart disease or retinopathy comorbidities in diabetic patients seemed to be associated with an increased risk of developing SSHL. The risk of developing SSHL increased with the severity of diabetes.

Reducing a Barrier to Diabetes Education

Purpose

Recent research suggests that hearing loss, a frequent problem for aging adults, is more prevalent in people with diabetes. Hearing impairment affects a patient’s learning. This article reviews the anatomy and physiology involved in hearing, describes common causes of hearing loss in people with diabetes, and describes how hearing loss is diagnosed and treated. Two simple tests the diabetes educator can use to screen for hearing loss are described, and interventions that improve communication with patients with difficulty hearing are explained.

Conclusions

Hearing loss can negatively affect a patient’s ability to actively participate in diabetes education. Diabetes educators have a responsibility to learn how to communicate better with their patients who have a hearing impairment. Diabetes educators are uniquely positioned to improve the health status of their patients by identifying persons who need referral for further evaluation of their hearing.