Hearing plays an important role in our day to day life as it helps us in communication and interaction with other people. It forms an important part of speech development and defense mechanism. High prevalence of non-communicable disease due to life style changes is also contributing to pathological hearing loss. Consequently, it is anticipated that hearing impairment will progressively become prevalent across all age groups. Hearing impairment is defined by the World Health Organization (WHO) as a hearing loss with thresholds higher than 25db in one or both ears and the degree of hearing loss is classified as mild, moderate, severe or profound.[[i]]

Diabetes mellitus (DM) is a non- communicablemetabolic disease, marked by high blood glucose level due to either absolute or relative insulin hormone deficiency. Approximately 72.9 million individuals suffer from DM in India.[[ii]] The disease’s long-term complications can be macrovascular or microvascular in nature. The microvascular complications of DM and diabetic neuropathy affect hearing in the diabetic population. More than 43 % of diabetes patients are likely to have some degree of hearing impairment related or unrelated to chronic hyperglycemia.[[iii]]

Researchers have reported hearing loss of low, mid and high frequencies which can be due to either neuropathy or microvascular complications. Hearing loss complications in DM can be bilateral (B/L) and sensorineural (SN) and may be gradually progressive. SNHL is found to have an association with age, duration of DM, HbA1c, ender, hypertension, hyperlipidemia, obesity and socioeconomic status along with drinking and smoking habits.[[iv],[v],[vi]]

[i].Elzouki, Abdelaziz Y. Textbook of clinical pediatrics (2 ed.). 2012. Berlin: Springer. p. 602.ISBN 9783642022012.https://en.wikipedia.org/wiki/Hearing_loss#Classification

[ii].Gadag RP, Nayak PS, J T. Clinical Asssessment of Sensorineural Hearing Loss among Diabetes Mellitus Patients. Bengal J Otolaryngol Head Neck Surg. 2020;28(2):112–9.

[iii].Al-Rubeaan K, AlMomani M, AlGethami AK, Darandari J, Alsalhi A, AlNaqeeb D, et al. Hearing loss among patients with type 2 diabetes mellitus: a cross-sectional  study. Ann Saudi Med. 2021;41(3):171–8.

[iv].Dadhich S, Jha S, Sinha V, Samanth T.A prospective, observational study of incidence of sensory neural hearing loss in diabetes mellitus patients. Indian J Otol. 2018;24:80–2.

[v].Hwang J-H, Wu C-C, Hsu C-J, Liu T-C, Yang W-S. Association of central obesity with the severity and audiometric configurations  of age-related hearing impairment. Obesity (Silver Spring). 2009 Sep;17(9):1796–801.

[vi].Parmar SM, Khare P, Chaudhary M. Evaluation of Effects of Diabetes Mellitus Type 2 and Hyperlipidemia on Hearing. Indian J Otol. 2017;23(3).

The study was conducted at the Department of ENT, Dr. RPGMC Tanda, involving patients attending the diabetic clinic with type 2 diabetes mellitus (DM). This hospital-based, cross-sectional study included 150 patients aged 30-55 years, both male and female, over a period of one year. Participants were selected if they met the inclusion criteria of being between 30-55 years old, having type 2 DM, providing informed consent, and having intact and normal tympanic membranes. Exclusion criteria included lack of consent, history of middle ear diseases or surgeries, conductive hearing loss, chronic illnesses or neurological diseases other than diabetes, use of ototoxic medications, occupational noise exposure, family history of deafness, and history of radiotherapy, autoimmune diseases, hypertension, thyroid disorders, cardiac diseases.

The study procedure involved recruiting eligible patients from the diabetic clinic, obtaining informed consent, and recording data on age, sex, occupation, weight, smoking and alcohol history, and medical history including diabetes, hypertension, hypothyroidism, ototoxic medication use, ear surgery, radiotherapy, autoimmune disease, and renal disease. Routine investigations such as FBS, HbA1c were conducted. Hearing loss was assessed using pure tone audiometry in the ENT department, measuring air and bone conduction thresholds at various frequencies. The results were charted on an audiogram, with the degree of hearing impairment indicated by the intensity increase needed above normal levels. The bone conduction threshold measured cochlear function, and the air-bone gap indicated the degree of conductive deafness. The audiometer was calibrated to zero dB for normal hearing. 

The mean age of study participants was 45.19 ± 7.03 and majority were between age group 40-50 years (40.7%), females (51.3%).

Table 1: Demographic characteristics of the patients

The study found that age had a statistically significant association with SNHL (p<0.001). The prevalence of SNHL increased with age, being 16.0% in the 30-40 age group, 41.3% in the 40-50 age group, and 42.7% in participants over 50 years old, with the highest prevalence observed in the >50 age group.

Table 4: Association of age with SNHL

Duration of diabetes mellitus showed a significant association with hearing impairment (p=0.001), with one case of profound impairment in participants with 1-3 years of diabetes and one case of severe impairment in those with 3-7 years of diabetes. Similarly, fasting blood sugar (FBS) levels were significantly associated with hearing impairment (p=0.000), with seven cases of moderate impairment, one case of profound impairment, and one case of severe impairment observed in participants with FBS >126 mg/dL. Additionally, HbA1c levels were significantly associated with hearing impairment (p=0.000), with seven cases of moderate impairment, one case of profound impairment, and one case of severe impairment noted in 

participants with HbA1c ≥6.5%.

Table 4: Association of different variables with SNHL

The present cross-sectional study was done with the objective to examine age related trends in sensorineural hearing loss among diabetic patients. This study includes 150 diabetic patients who presented at RPGMC, Tanda. The present study found significant increase in hearing loss prevalence with advancing age, particularly among those over 50 years.

The present study found that the mean age of study participants was 45.19 ± 7.03 years and the mean age of participants who had SNHL (47.60 ± 6.27) was statistically significant (P <0.001) more than the mean age of those who doesn’t have SNHL (42.77 ± 6.97). A study by Bhaskar KN et al found that the incidence of SNHL increases with an increase in age.27 A study by Srinivas et al found that the SNHL was more among study participants who were 60-65 years old (64%) and lowest among those who were 31-35 years of age.28Virtaniemi J et al found that Older diabetic patients have higher incidence of hearing loss especially severe grade hearing loss.[[i]] The increase in hearing threshold is attributed to microvascularangiopathy occurring in capillaries of striavascularis which makes this vessel thicker than normal and these changes can occur in vessels supplying other parts of auditory system as well.[[ii]]  A study by Shafiepour et al found a significant association (p<0.01) between age and hearing loss of moderate to severe level, however there was no significant association between the gender and hearing loss.[[iii]]

  A study by Thimmasettaiah NB et al found that 100% cases of sever impairment had their HbA1c more than 10 %, 80% cases with moderate impairment had HbA1c between 8.5 to 10% while 66.7% cases of mild impairment had their HbA1c between 7.5 to 8.5%.[[iv]]

The present study found that the mean PTA right ear was 25.06 ± 9.3 and the mean PTA among those who had SNHL (31.02 ± 9.98) was statistically significantly (p=0.00) more than those who doesn’t have SNHL (19.11 ± 2.44). The present study found that the mean PTA left ear was 25.22 ± 9.85 and the mean PTA among those who had SNHL (31.84 ± 9.94) was statistically significantly (p=0.00) more than those who doesn’t have SNHL (18.60 ± 2.80). A study by Santosa A et al found that mean right ear audiogram was 48.15 ± 36.92 and left ear audiogram was 44.93 ± 28.34. A study by Abhilash et al found that mean PTA on right side was 63.91±14.62 db while that of left ear was 54.40 ± 13.72 db.[[v]]

[i].Virtaniemi J, Laakso M, Nuutinen J, Karjalainen S, Vartiainen E. Hearing thresholds in insulin-dependent diabetic patients. J Laryngol Otol. 1994 Oct;108(10):837–41.

[ii].Rust KR, Prazma J, Triana RJ, Michaelis OE 4th, Pillsbury HC. Inner ear damage secondary to diabetes mellitus. II. Changes in aging SHR/N-cp  rats. Arch Otolaryngol Head Neck Surg. 1992 Apr;118(4):397–400.

[iii].Shafiepour M, Bamdad Z, Radman M. Prevalence of hearing loss among patients with type 2 diabetes. J Med Life. 2022 Jun;15(6):772–7.

[iv].Thimmasettaiah NB, Shankar R, Ravi GC, Reddy S. A one year prospective study of hearing loss in diabetes in general population. Transl Biomed. 2012;3(2):1–7.

[v].A M A, H M S. BERA as a objective test in cases of inconsistent response for pure tone audiometry. IP J Otorhinolaryngol Allied Sci. 2021;4(1):9–15.

The study concludes that there is significant increase in hearing loss prevalence with advancing age , highlighting the need of regular hearing assessments in older diabetic populations.

The authors declare that they have no conflict of interest

No funding sources

The study was approved by theENT, DRPGMC, Tanda, Himachal Pradesh.