|Year : 2018 | Volume
| Issue : 2 | Page : 165-169
Prevalence of sensorineural hearing loss among type-II diabetes mellitus patients attending KLES Dr. Prabhakar Kore Hospital and MRC: A cross-sectional study
Aniruddh Tiwari, Ramesh S Mudhol
Department of Otorhinolaryngology and Head and Neck Surgery, J. N. Medical College, Belagavi, Karnataka, India
|Date of Web Publication||18-May-2018|
Dr. Aniruddh Tiwari
‘Parvati’, Sector 2, Shivabasava Nagar, Belagavi 590 010, Karnataka
Source of Support: None, Conflict of Interest: None
INTRODUCTION: Diabetes mellitus (DM) is an important healthcare concern in the modern world. This disease and its complications can affect virtually every system in the human body. A possible complication of DM is sensorineural hearing loss (SNHL).
AIM: The current study aimed to evaluate the prevalence of SNHL among the patients of type-2 DM attending the hospital as well as to correlate the severity of hearing loss to the duration of diabetes and the glycosylated hemoglobin (HbA1c) levels. A total of 125 known cases of type-2 DM were included in the study.
METHODOLOGY: For each patient, a detailed history was taken, thorough clinical ear, nose, and throat examination was done, hearing thresholds were evaluated by means of pure tone audiometry and HbA1c levels were measured.
RESULTS: SNHL was seen in 76.8% of the patients. Robust correlation was seen between the severity of SNHL and the duration of DM (P < 0.0001, r coefficient 0.3668). Positive correlation was seen between SNHL and HbA1c levels (P = 0.0001, r coefficient 0.3517).
CONCLUSION: This study confirms that there is a high prevalence of SNHL in type-2 DM.
Keywords: Diabetes mellitus, glycosylated hemoglobin, pure tone audiometry, sensorineural hearing loss
|How to cite this article:|
Tiwari A, Mudhol RS. Prevalence of sensorineural hearing loss among type-II diabetes mellitus patients attending KLES Dr. Prabhakar Kore Hospital and MRC: A cross-sectional study. Indian J Health Sci Biomed Res 2018;11:165-9
|How to cite this URL:|
Tiwari A, Mudhol RS. Prevalence of sensorineural hearing loss among type-II diabetes mellitus patients attending KLES Dr. Prabhakar Kore Hospital and MRC: A cross-sectional study. Indian J Health Sci Biomed Res [serial online] 2018 [cited 2020 Feb 25];11:165-9. Available from: http://www.ijournalhs.org/text.asp?2018/11/2/165/232684
| Introduction|| |
Diabetes mellitus (DM) is a metabolic disorder which occurs due to relative or absolute insulin deficiency resulting in elevated blood glucose and causing long-term vascular as well as neurological complications. While type-1 DM occurs due to autoimmune destruction of insulin-producing beta cells of the pancreas, type-2 diabetes is due to a combination of impaired beta pancreatic cell function with insulin resistance at the receptor level. Worldwide around 422 million people suffer from this disease. In India, roughly 5% of the population consists of diabetics. DM is the most important disease that can affect virtually every system of the body. The long-term complications of the disease can be a macrovascular (coronary artery disease, peripheral vascular disease, nephropathy, etc.,) or microvascular (neuropathy, retinopathy, etc.,) nature. A frequent complication in type-2 DM is deafness. Hearing loss described in DM is generally bilateral and sensorineural in nature. It may be gradual and progressive with high frequencies being affected in the elderly similar to presbycusis. However, low- and mid-range frequency hearing loss has also been reported by some authors. Microvascular complications of diabetes  as well as diabetic neuropathy  are believed to affect the hearing of diabetic patients. The present study aims to clarify the picture regarding type-2 DM and auditory dysfunction.
To study the prevalence of sensorineural hearing loss (SNHL) among type-2 DM patients and to study the correlation between degree of hearing loss and the duration of DM.
Review of literature
DM can lead to an array of the head-and-neck manifestations. Commonly encountered ocular conditions include diabetic retinopathy, conjunctival hemorrhage and diabetic cataract, and mononeuropathy of the head-and-neck region is often a presenting sign of the disease. There is a high association of Bell's palsy with diabetes and neuropathies of all cranial nerves except olfactory and hypoglossal nerves have been documented. The equilibrium disorders also occur frequently in this disease either due to peripheral neuropathy, direct end organ vestibular toxicity or fluctuations in the cerebral circulation glucose concentration. The diabetic patients are also particularly prone to infections in general as well as certain particular infections such as malignant otitis externa (due to Pseudomonas aeruginosa) and invasive fungal rhinosinusitis (rhinocerebral mucormycosis). Jordao in 1857 was the first to report a relationship between DM and deafness. The suggested reasons for this SNHL include cochlear microangiopathy, hyperglycemia of the cerebrospinal fluid or perilymph, auditory neuropathy, and diabetic encephalopathy. The two important factors seen in diabetics which are believed to affect hearing are diabetic angiopathy and diabetic neuropathy. In diabetic angiopathy, due to insulin resistance, there is the higher production of triglycerides in diabetes. There is a proliferation of endothelium, with an accumulation of glycoproteins leading to thickening of the capillary vessels in basement membranes. There is the reduced transport of nutrients through these thickened vessels resulting in reduced blood flow through narrow vessels, which may lead to secondary degeneration of the vestibulocochlear nerve (CN VIII). Diabetic neuropathy– there is activation of the polyol pathway in diabetic patients which causes accumulation of sorbitol within the neurons. This reduces the myoinositol content as well as the intracellular Na/K ATPase activity, leading to cellular swelling and osmotic damage. A positive relation between glycosylated hemoglobin (HbA1c) levels and the severity of hearing loss was observed by Krishnappa and Naseeruddin in 2014. Patients with poor glycemic control (HbA1c levels >8%) showed higher levels of hearing loss, while patients with good glycemic control had either normal hearing or mild hearing loss.
| Methodology|| |
This cross-sectional study was conducted from January 2016 to December 2016. 125 patients with type-2 DM were included in the study. The sample size was calculated using the standard formula for a prevalence study– 4 pq/d*d (where “P” = prevalence rate of SNHL in type-2 diabetes, here taken as 73%, “q” = 100−p, and “d” is the standard error, here taken as 8). Ethical clearance for the study was obtained from the Institutional Ethical Committee. Only known type-2 diabetes patients with minimum duration of disease 3 years were included in the study. Patients with family history of deafness, history of ear surgery/trauma, history of chronic otitis media, and occupational noise exposure were excluded from the study. All cases were subjected to ear, nose, and throat examination, pure tone audiometry and measurement of HbA1c levels. Written and informed consent was obtained from all the study participants. The prevalence of SNHL was calculated among the diabetic patients. The correlation, if any, was studied between SNHL and duration of diabetes, as well as between SNHL and HbA1c levels.
| Results|| |
Out of a total 125 cases, 66 (52.8%) patients were male and 59 (47.2%) were female. The patients were between 30 years and 65 years of age. Considering the age-wise distribution of cases, more number of patients were found in the age group of 50–60 years (54) and patients above 60 years (46). There were 20 patients in the age group of 40–50 years, whereas patients in the age group 30–40 years were only five. This age-wise distribution is depicted in [Table 1] and [Graph 1]. The mean age was found to be 55.52 ± 7.47 years. All the patients were known cases of type-2 DM. A total of 96 cases were found to have SNHL and 29 cases had normal levels of hearing (elevation of thresholds 0–25 dB). A majority (50) of the cases having sensorineural hearing loss showed mild degree of deafness, i.e., loss of 26–40 dB. Twenty-nine patients showed moderate (41–55 dB) degree deafness, while the number of patients with moderately severe (56–70 dB) and severe (71–90 dB) degree deafness were 12 and 7, respectively. None of the cases showed profound hearing loss (>90 dB). The proportion of cases with SNHL and the distribution of various degrees of deafness are depicted in [Table 2] and [Graph 2], [Graph 3]. All the cases included in the study had been known cases of type-2 DM for at least 3 years. A large majority of cases (81) had been suffering from the disease for 3–6 years out of which 60 (74.07%) showed SNHL. Twenty-six patients had the disease for 6–9 years, with 22 exhibiting SNHL. Thirteen patients had a disease duration of 9–12 years (with 12 having hearing loss) and five patients had had the disease for >12 years (four showing hearing loss). The maximum duration of disease encountered was 20 years. Distribution based on the duration of the disease as shown in [Table 3] and [Graph 4]. The correlation of hearing loss with duration of disease was found to be highly significant (P < 0.0001, Pearson's r coefficient– 0.3668). HbA1c was measured for each case and tallied with the level of SNHL. Of the 125 patients, 80 had HbA1c levels between 6% and 8%, with 57 (71.25%) having hearing loss. In the 8.1%–10% range were 29 patients, 26 (89.65%) of whom had SNHL. There were 8 patients each in the 10.1%–12% group as well as in the group with levels >12%, and 7 cases in each group showed hearing loss. This relationship between HbA1c and hearing loss is shown in [Table 4] and [Graph 5]. The P = 0.0001 and Pearson's r coefficient was 0.3517.
| Discussion|| |
The current study was carried out at KLES Dr Prabhakar Kore Hospital and Medical Research Centre, Belagavi (Karnataka) to evaluate the prevalence of SNHL among type-2 DM patients attending the hospital. A large majority of cases, i.e., 96 showed SNHL. Thus, the prevalence was calculated to be 76.8%. Twenty-nine patients had normal hearing levels. Prevalence-based studies give prevalence rates comparable to the current study. Malucelli et al. found the prevalence to be 76%, Rajendran et al. as 73.3% and Krishnappa and Naseeruddin  found the prevalence of SNHL among type-2 diabetic patients to be 73%, which are all comparable to our calculated prevalence of 76.8%. A positive correlation was seen in the current study when extrapolating the severity of the SNHL with the duration of DM. As the duration of the disease increased, higher proportions of patients were found to have SNHL, except in the group which had diabetes for >12 years where the number of samples was very low, i.e., only 4. This propensity of worsening of hearing loss with duration of disease follows the logic that exposure to the basic pathological processes that result in SNHL (microangiopathy and neuropathy) is greater in the patients that have been suffering from the disease for a longer time. Similar results have been reported by other authors., On examining the distribution of different degrees of hearing loss in each group, the correlation between HbA1c levels and the severity of hearing loss does not seem as straightforward as the correlation between duration of disease and severity of hearing loss. The groups with the lowest (5.1%–7%) and the highest (>13.0%) HbA1c levels had no cases with severe SNHL and a large majority of cases in both these groups had hearing loss of a mild degree. The group with HbA1c levels 9.1%–11.0% had the highest number (3) of cases with the severe hearing loss, whereas the 11.1%–13.0% group had the highest proportion (1 out of total 4, i.e., 25%) of cases with the severe hearing loss. A number of studies have shown a positive correlation between HbA1c levels and the severity of hearing loss,, while some have found no correlation. Multiple authors have concluded that good glycemic control in diabetic patients reduces the incidence of SNHL.,,
As the prevalence of DM in the Indian population is on the higher side, a larger sample size could have thrown more light on the matter of SNHL in type-2 DM. The primary aim of this study was to calculate a prevalence rate, and hence only a single pure tone audiometry evaluation was done. Serial monitoring of auditory ability in the diabetic patients could have helped delineate the progression of auditory impairment.
| Conclusion|| |
There is a real threat of auditory impairment in long-standing cases of type-2 DM. As the duration of illness progresses, the degree of hearing loss is seen to worsen indicating that prolonged and continued exposure to the harmful pathological effects of DM has a strong bearing on hearing impairment. Some amount of correlation was seen between severity of hearing loss and HbA1c but not as strong as the correlation between the severity of hearing loss and duration of disease. It is important to keep in mind the auditory complications of DM while evaluating a diabetic patient, especially if the disease is long standing. Routine audiological evaluation in such cases may help in early diagnosis of SNHL while good glycemic control may prevent or delay its occurrence.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]