Key Words

Diabetes Mellitus (DM) and Hearing Loss – Type 2 Diabetes Mellitus (T2DM) and Hearing Loss – Damage to the Cochlea - Sensorineural Hearing Loss caused by Diabetes – Microangiopathy caused by DM – Age related Hearing Loss Caused by Type 2 diabetes mellitus. – Oxidative stress causing sensorineural hearing loss.

Diabetes Mellitus (DM) is a chronic metabolic disease. It is characterized by persistent hyperglycemia, impaired metabolism involving that of protein, carbohydrate and fat metabolism because of insulin dysregulation.

Persistent hyperglycemia has been shown to cause damage to microvascular and macrovascular structures. This fundamentally represents the pathophysiologic mechanism that causes damage to various structures that result in retinopathy, nephropathy, peripheral neuropathy and cardiovascular injury.

The cochlear has also been found to be involved to suffer damage caused by DM(1).

Age and duration of DM are now thought to be considerations in hearing loss in patients suffering from DM. Individuals suffering from T2 DM are 4.9 times more likely to develop a hearing loss as compared to normal controls (2).

Horikawa and colleagues (3) found that in their study patients suffering from T2DM were 2,15 times likely to develop a hearing loss compared to normal people. This is quite a significant finding. T2DM is a strong independent factor in cause of sensorineural hearing loss. Bilateral sensorineural hearing loss is also associated in persons suffering from T2DM.

Many studies have consistently demonstrated elevated hearing thresholds across all frequencies in those suffering from T2DM as compared to normal persons. The hearing thresholds most affected are between 4K Hz to 8 K Hz (4) .

Some studies evaluated persons who were suffering from T2DM and healthy normal individuals to serve as a control group. Those who were suffering from T2DM were found to have markedly elevated threshold frequencies from 8K Hz to 16 K Hz as compared to the normal healthy group ( 5 ). This led the researchers to conclude that T2DM patients can initially present with hearing loss in the high frequencies. They also concluded that their study provided a direct correlation between the duration of T2DM with hearing loss (6).

People suffering from T2DM for a period of 10 years were 2.07 times more likely to suffer from sensorineural hearing loss as compared to those who suffered from T2DM for less than 10 years (7) . T2DM progresses slowly and at times asymptomatically over a long period of time ( 8 ) . Sensorineural hearing loss progresses over time and often goes undiagnosed ( 9 ) .

Pathology

Many similarities have been found in the cochlear of persons of advanced age and those suffering from T2DM.

The American Diabetes Association emphasizes that consistent hyperglycemia combined with oxidative stress, cochlear microangiopathy along with auditory neuropathy are the mechanisms that contribute majorly to the occurrence of hearing loss in persons suffering from T2DM.

The basal turn of the spiral ganglion and the basement membrane within the capillaries of the stria vascularis were found to be significantly damaged. This could likely explain the finding of hearing loss in the high frequencies.

Arteriosclerotic changes are well known to be associated with T2DM. Thus, it is thought that T2DM could very likely exacerbate the mechanisms that cause age related hearing loss.

It is also thought that subclinical microvascular disease could be one of the factors of hearing loss in T2DM. Chronic persistent hyperglycemia can likely damage blood vessels of the inner ear that results in diminished oxygen and nutrient supply. The consequences of this diminished blood flow are thickened capillary walls , diminished blood supply that result in degeneration of the stria vascularis and damage to the outer hair cells. Oxidative stress, microvascular damage to the inner ear result in hearing loss. T2DM neuropathy can affect the auditory nerve by disrupting transmission of signals from the cochlear to the brain.

Conclusions

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Patients suffering from T2DM are more likely to suffer from hearing loss, very often in the form of sensorineural hearing loss and is often bilateral.

The high frequencies are more likely to be affected.

Males are more likely to be affected.

Effective treatment of T2DM is consistent controls of glycemia and is the key to delaying / preventing hearing loss in those suffering from T2DM.

It is very important to screen all individuals suffering from T2DM with hearing tests frequently to check if they demonstrate the beginnings of sensorineural hearing loss. Treatment lies in consistent and emphatic control of their blood sugar levels.

References

1. Kumar P, Singh NK, Apeksha K, Ghosh V, Kumar RR, Kumar Muthaiah B: Auditory and vestibular functioning in individuals with type 2 diabetes mellitus. a systematic review. Int Archives Otorhinolaryngol. 2022. 26(2);e281-e288. Doi10.1055/s-0041-1726041.

2. GiraudetF, Mulliez A, de ResendeLM et al ; Impaired auditory neural performance. Another dimension of hearing loss in type 2diabetes melitus. Diabetes Metab 2022;48(6) ;101360. Doi;10.1016/jdiabet.2022.101360.

3. Horikawa C, Kodama S, Tanaka Set al. Diabetes and risk of hearing impairment in adults; a meta-analysis. J. Clin Endocrinol Metab. 2013;98(1);51-58.

4. Akinpelu O V, Mujica- Mota M, Daniel S J . Is type 2 diabetes mellitus associated with alterations in hearing? A systematic review and meta-analysis. Laryngoscope.2014.124(3);767-776.doi:10.1002/lary.24354.

5. Caballero- Borrego M, Andujar – Lara I : Type 2 Diabetes Mellitus and Hearing Loss. A Prisma Systematic review and meta-analysis. Otolaryngol- Head and Neck Surg.2025.vol173(5)1041-1053.doi10.1002/ohn.1346 http;//otojournal.org.

6. Hyun-su Kim C, Lauritsen K L, Nguyen S A, Meyer T A, Cumpston E C, Pelic J, Labadie : Characteristics of hearing loss in type 2 diabetes mellitus; A systematic review and meta-analysis. Otolaryngol- Head and Neck Surgery. 2025 . Vol 173(6)1317-1327. Doi10.1002/ohn.1378.

7. Aladag I, Eyibilen A,Guven M, Atis O, Erkomaz U: Role of oxidative stress in hearing impairment in patients with type two diabetes mellitus. J Laryngol Otol.2009;13(9)957-963. Doi 10.1017/S0022215109004502.

8. Fukushima H, Cureoglu S, Schachern P A, Paparella MM :Harada T, Oktay MF: Effects of type 2 diabetes mellitus on cochlear structure in humans. Arch Otolaryngol Head and Neck Surg. 2006; 132(9);934-938. Doi10.1001/archotol.132.9.934.

9. Tsai Do B S, Bush ML, Weinrich H Met al; Clinical practice guideline: age related hearing loss. Otolaryngol Head and Neck Surg. 2024; 170 (Suppl2) ; S1-S54 doi;10.1002/ohn.750