Journal of Otology & RhinologyISSN: 2324-8785

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Research Article, J Otol Rhinol Vol: 6 Issue: 1

Prediabetes Associated Hearing Loss: A One Year Prospective Study on Hundred Patients

Prabhakara Rao Y and Vamshi K Biroj*
Department of ENT, MRIMS, Suraram, Hyderabad, India
Corresponding author : Dr. Vamshi K Biroj
Associate Professor, Department of ENT, MRIMS, Suraram, Hyderabad, India
[email protected]
Received: November 23, 2016 Accepted: January 17, 2017 Published: January 24, 2017
Citation: Rao YP, Biroj VK (2017) Prediabetes Associated Hearing Loss: A One Year Prospective Study on Hundred Patients. J Otol Rhinol 6:1. doi: 10.4172/2324-8785.1000302


Aim: The objective of this study was to identify whether prediabetics have a higher incidence of hearing loss than people with normal blood glucose levels.

Materials and method: We performed a prospective study of audiometric data of a hundred patients with pre-diabetes matched with another hundred of normal control group over a span of a year. A complete detailed otological examination and pure tone averages were calculated initially from each group and evaluated.

Result: There has been an increase incidence of high frequency hearing loss in prediabetic group compared to normal individuals implying that increase uncontrolled glucose levels increase risk of hearing impairment.

Keywords: Prediabetes; Sensorineural hearing loss; Pure tone audiometry


Prediabetes; Sensorineural hearing loss; Pure tone audiometry


Prediabetes is an intermediate state of hyperglycaemia with glycaemia parameters above normal but below the diabetic range. Adults with prediabetes whose blood glucose is higher than normal have a 30% higher rate of hearing loss compared to those with normal blood glucose [1]. This is a study to correlate the audiometric data between prediabetics and normal population.

Materials and Methods

In a one year prospective study, one hundred patients diagnosed with prediabetes attending outpatient department of medicine and ENT in our institution were tested on audiometric measures including puretone thresholds and compared with another hundred normal healthyindividuals.
Fasting, Post prandial blood glucose, urine for sugars, Hb1Ac, puretone audiometric measurements and detailed ENT examination were performed in all individuals participated in the study. Age less than 18 years, Patients suffering from or on treatment for tinnitus, any middle ear disease, any psychiatric illness and any known systemic disease were the exclusion criteria.


In the prediabetic group there were 68 men and 32 women, while the control group had 80 men and 20 women (Table 1). 10% of prediabetics had normal hearing compared to 65% in control group. 75% of prediabetics had some degree of sensory hearing loss (Table 2). The prediabetic group had more (42%) moderate and (14%) severe hearing loss compared to (21%) moderate and (6%) severe hearing loss in normal study individuals (Figures 1-3). All the patients were evaluated by pure tone audiometry and bone conduction and air conduction thresholds were compared. More number of prediabetics had higher loss at high frequencies compared to normal individuals (Tables 3-6).
Figure 1: Severity of hearing loss in Prediabetics.
Figure 2: percentage of low and highfrequency Hearing loss.
Figure 3: There is more incidence of high frequency hearing loss in prediabetics compared to the non- prediabetic group.
Table 1: Male:Female distribution.
Table 2: Hearing loss in two groups.
Table 3: Bone conduction thresholds in prediabetics compared with control group.
Table 4: Air conduction thresholds in prediabetics.
Table 5: Bone conduction thresholds.
Table 6: Air conduction thresholds.


The most frequent causes of vestibular and auditory abnormalities are attributed to dysfunctions in the metabolism of carbohydrates, thyroid hormones, adrenal and other different metabolic disorders. Among glucose metabolism disorders, diabetes mellitus is the affection most commonly related with auditory disorders [2].
Prediabetes is the precursor stage before diabetes mellitus in which not all of the symptoms required to diagnose diabetes are present, but blood sugar is abnormally high. This stage is often reoffered as “grey area” [3]. The diagnostic criteria are not uniformly across various international professional organizations, it remains a high risk for future development of early nephropathy, retinopathy and macrovascular disease.
WHO defined Prediabetes/Impaired Fasting glucose [4] (IFG) as
• Fasting blood glucose (FBG) 6.1-6.9 mMol/L (110-125 mG/ dL)
• Impaired Glucose tolerance test (GTT) 7.8-11.0 mMol/L (140-200 mG/dL) after 75 g of oral glucose.
• Or a combination of two based on 2 hour oral GTT.
It is evident from a review of the otolaryngology literature that the relationship between diabetes and SNHL is complex. There is paucity of data about pathogenesis of audiovestibular abnormalities in prediabetes. The pathogenesis of vascular impairment in prediabetic conditions is particularly intriguing [5]. All the conditions leading to diabetes may occur at a lesser extent in course of prediabetes [6].
Cullen et al. [7] summarised that male with diabetes had worse hearing than female, may be due to occupational noise exposure. Taylor et al. [8] observed that female patients with diabetes had significantly greater loss than male patients with diabetes.
The pathogenic effects of diabetes on ear can be because of neuropathy, angiopathy and association of both. Jorgensen et al. [9] was the first to study the histopathological properties of temporal bones in patients with diabetes and hearing loss, and observed thickening of walls of the vasa nervosum of the eighth nerve, leading to acoustic neuropathy. Micro angiopathic changes in the Stria vascularis, endolymphatic sac and basilar membrane were noted by Wackym et al. [10]. Makishima et al. [11] described atrophy of spiral ganglion neurons and demylination of the eighth cranial nerve in four diabetic subjects.
Diabetic angiopathy has been characterised by endothelial proliferation, accumulation of glucoprotein in the intima and thickness of basal membraneofcapillaries and small blood vessels. Accumulation of positive Periodical Schiff Acid (PAS) on the artery wall as well as modiolus vessels and vascular stria has been confirmed [11]. Costa [12] in a study conducted with temporal bones of six subjects has also detected positive PAS material on the wall of stria vasscularis and modiolus capillaries.
Genetic correlation between diabetes and hearing loss has also been suggested. Yamasoba et al. [13] presented a theory of mitochondrial 1 DNA affection leading to alteration in mitochondrial protein synthesis, which inturn leads to alteration of oxidative phosphorilation, reduction in ATP formation, alteration of ionic pumps leading to alteration of Na++ , K+, Ca++ ultimately leading to cell death. Fowler et al. [14] described Diadmoad Syndrome or Wolfram syndrome also as a consequent mutation of mitochondrial DNA.
We observed that out of 100 patients there was male predominance in the ratio of 2:1 as most of the studies denote. There was also aslighty more incidence of degree of hearing loss in males compared to females. 75% of patients had SNHL in Prediabetic group. While studying the threshold levels high frequency loss was noted in bone as well as air conduction thresholds as in uncontrolled diabetics. The pathogenic effects of elevated blood sugars can be compounded by various confounding factors such as acoustic trauma, exposure to neuro-ototoxic compounds, concurrent viral infections, which all warrant further detailed and long term studies


There is a predisposition of high frequency hearing loss in prediabetics compared to normal population which may progress further as the disease progresses. Further large scale studies are to be performed with auditory brain stem response to evaluate the probable site of pathology in the auditory pathway.


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