ABSTRACT
Introduction: The association between diabetes and hearing loss has been a topic of discussion since many years. Type 2diabetes mellitus (DM) which is the most predominant form of diabetes worldwide, accounts for 90% of cases globally. DMis a chronic metabolic disorder characterized by high blood glucose level, associated with insulin resistance and relativeinsulin deficiency. DM is associated with a lot of complications; a lesser known complication is auditory organ dysfunction.The International Diabetes Federation estimated in 2014 that 387 million people have diabetes worldwide and that by 2035this number will rise to 592 million. Among these, 179 million are undiagnosed. In the United States, the Centers for DiseaseControl and Prevention estimated in 2014 that 29.1 million people had diabetes and that 8.1 million of them (27.8%) wereundiagnosed. These data reflect the late detection of hearing loss due to undiagnosed diabetes. Studies have indicated thatvascular changes which include thickening of capillary walls in the stria vascularis, neural changes in the cochlea, and loss ofouter hair cells are the causes of hearing changes in DM.Objective: The objectives are as follows: (1) Primary objective: To assess the prevalence of hearing loss in patients with Type 2DM when compared to non-diabetic patients and (2) secondary objective: To analyze the effect of age, glycemic control (HbA1c),and duration of diabetes on auditory acuity and to assess whether otoacoustic emission (OAE) can be used as a screeningtest for hearing assessment in diabetics.Materials and Methods of Study: The design of this study was hospital based observational prospective study carried outfrom February 2017 to July 2018. A total of 100 patients who presented to the ENT OP Department Sree Gokulam MedicalCollege and Research Foundation were studied by dividing into two groups; Group A consisted of 50 type 2 diabetic patientsand Group B consisted of 50 age- and gender-matched non-diabetic patients. The age group of the patients was between 30and 50 years. All the patients were subjected to Pure Tone Audiometry for the quantitative and qualitative assessment of hearingloss. Transient OAE (transient evoked OAEs [TEOAE]) was also done to know whether it can be used as a screening test forthe early detection of hearing loss. HbA1c was done in diabetic patients to detect any association with the hearing loss. Ageand duration of diabetes and its correlation with hearing loss were also assessed.Results: Our study confirmed the existence of sensorineural hearing loss (SNHL) in type II diabetic patients, mostly bilateralmoderate SNHL. Age and duration of diabetics had an association with SNHL. As the age increases, there is increase in theauditory thresholds and amount of hearing loss (AHL). Type 2 diabetic patients with long duration of diabetes also had higherauditory thresholds at all frequencies from 250 to 8000 Hertz (Hz), when compared to non-diabetic patients and the AHL wasalso higher as the duration of diabetes increased. HbA1clevel had no significant correlation with hearing loss. Theresult of TEOAE was refer, i.e. abnormal in all the patientswith hearing loss.Conclusion: The present study reports SNHL in 68% of type IIdiabetic subjects and 2% of healthy non-diabetic subjects.The majority of the patients had bilateral moderate SNHL.The diabetic patients had increased hearing threshold at all frequencies with gradual increase in hearing loss from 250 Hz to 8000 Hz. Age and duration of diabetes had a positive correlationwith hearing loss. As the age increased AHL also increased. Similarly, as duration of diabetes increased, AHL also increased.HbA1c had no relation with auditory threshold and AHL. TEOAE can be used as a screening test for the early detection ofhearing loss in Type 2 diabetic patients, as the result was abnormal in all the patients with hearing loss. Since hearing loss canbe considered to be a consequence of diabetes, a metabolic assessment may be useful for patients presenting with hearingloss so as to reduce the high rate of undiagnosed diabetes mellitus in the community. The use of audio logical tests to monitorhearing in diabetic patients should be considered as a routine procedure so that quality of life can be improved for long standingdiabetics with needed therapeutic interventions for hearing improvement.