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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 23  |  Issue : 2  |  Page : 67-70

Screening of auditory acuity in patients with type 2 diabetes mellitus


Department of ENT, Smt. Kashibai Navale Medical College and General Hospital, Pune, Maharashtra, India

Date of Web Publication14-Jun-2017

Correspondence Address:
Netra A Pathak
A3/9, Aditya Sanskruti, Manaji Nagar, Near Navale Hospital, Pune-Bangaluru Highway, Narhe, Pune - 411 041, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/indianjotol.INDIANJOTOL_98_16

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  Abstract 

Diabetes mellitus (DM) is a multifunctional metabolic disorder affecting almost all the systems of the body. There is a strong relation between DM and hearing. The three main theories of pathogenesis of hearing impairment in patients with diabetes are microangiopathy, neuropathy, and combination of both. Even though studies have proved the occurrence of sensorineural hearing loss in DM, disagreement still exists among some about their relation. Material and Methods: This study was a prospective design. Aim: The present study aimed (1) to focus on and evaluate the interrelation between Type 2 DM and hearing loss; (2) to screen the degree of auditory acuity in patients with Type 2 DM using pure tone audiometry; and (3) to analyze the effect of age, glycemic status (fasting blood sugar and postprandial blood sugar), glycemic control (glycosylated hemoglobin), and duration of Type 2 diabetes on auditory acuity. Results: In the present study, it was found that the patients with Type 2 diabetes had a higher hearing threshold than the healthy controls. The patients with diabetes showed significant high-frequency, bilateral, mild-to-moderate SNHL. Conclusion: The glycemic status had significant correlation with hearing loss may be explained by diabetic microangiopathy of the inner ear, and the hearing was affected in both sexes equally.

Keywords: Auditory acuity, blood glucose levels, pure tone audiometry, sensorineural hearing loss, Type 2 diabetes mellitus


How to cite this article:
Pathak NA, Rokade VV, Shinde KJ. Screening of auditory acuity in patients with type 2 diabetes mellitus. Indian J Otol 2017;23:67-70

How to cite this URL:
Pathak NA, Rokade VV, Shinde KJ. Screening of auditory acuity in patients with type 2 diabetes mellitus. Indian J Otol [serial online] 2017 [cited 2017 Oct 22];23:67-70. Available from: http://www.indianjotol.org/text.asp?2017/23/2/67/208037


  Introduction Top


Diabetes mellitus (DM) is a metabolic disorder, due to relative or absolute lack of insulin resulting in elevated blood glucose levels associated with long-term vascular and neurological complications.[1] It affects almost all the systems in the body to its severity if left uncontrolled. Likewise, diabetes affects hearing by damaging the inner ear structures. The effect of DM on hearing is known since 1857 when Jordao first showed hearing loss in a patient with incipient diabetic coma.[2] The typical hearing loss in patients with diabetes is progressive, bilateral sensorineural hearing loss (SNHL) affecting the higher frequencies. But rarely, there are incidences where sudden onset, SNHL affecting lower frequencies is also noted.[3] The type of hearing impairment noted is similar to that of presbycusis, but those affected show a greater decrease in hearing than one would expect at that age. Type 2 DM in the age group of 30–50 years (early onset) cannot be ignored in the present day scenario. Hence, an attempt was made to assess the increased prevalence of subclinical hearing loss in early onset middle-aged patients with Type 2 DM.

Lasisi et al. (2003) found that the mean hearing thresholds in patients with diabetes of <10 years duration were far better than those with >10 years duration, and other studies also support that threshold becomes poorer as duration of diabetes increases,[2],[5],[6],[7] while others state that there is no relation between hearing threshold and DM.[3],[4]

Glycosylated hemoglobin (HbA1C) is also one of the indicators for control of diabetes. However, its elevated levels were not systematically as associated with increased thresholds of hearing. Thus, direct evidence that poor metabolic control in diabetes causing SNHL remains to be proven.[6] Even though studies have proved the occurrence of SNHL in DM, disagreement still exists among some about their relation.[8],[9]

Considering that both hearing loss and Type 2 DM are significant health issues, it is worthwhile to examine the relation between the two. The present study aimed (1) to focus on and evaluate the interrelation between Type 2 DM and hearing loss; (2) to assess the degree of auditory acuity in patients with Type 2 DM using pure tone audiometry (evaluating the frequency and intensity of hearing acuity); and (3) to analyze the effect of age, glycemic status, glycemic control (HbA1C), and duration of Type 2 diabetes on auditory acuity.


  Materials and Methods Top


The present study was conducted on 100 patients with diabetes selected randomly from diabetes outpatient department of our hospital who have Type 2 DM who were willing to participate in the study. Informed consent was obtained from all the participants enrolled in the study after explaining to them in detail about the study in their own language.

Inclusion criteria

The inclusion criteria were as follows:

  • Known patients with Type 2 DM
  • Aged between 31 and 55 years
  • Willing to undergo investigations.


Exclusion criteria

The exclusion criteria were as follows:

  • Patients with conductive hearing loss
  • Patients with mixed hearing loss
  • SNHL other than due to Type 2 diabetes, trauma due to head injury, congenital causes, family history of deafness, occupational noise exposure, and presbycusis in otherwise normal will be excluded from the study
  • Not willing to undergo investigations.


All the participants fulfilling the inclusion criterion underwent the following investigations:

  1. Thorough ENT examination with case history
  2. HbA1C level (HbA1C) to find the glycemic control, if patients have HbA1C level between 6% and 8% they were labeled as controlled and those with HbA1C level >8% were labeled as poorly controlled
  3. Hearing tests such as pure tone audiometry were performed for all patients. For pure tone audiometry, thresholds were obtained for octave frequencies from 250 to 8 KHz for air-conduction stimuli and from 250 to 4 KHz for bone-conduction stimuli.[10]



  Results Top


In our study, 100 patients with Type 2 DM underwent pure tone audiometry. [Table 1] shows that out of 100 patients, 60 had SNHL that is the prevalence of SNHL among Type 2 DM is 60%.
Table 1: Prevalence of sensorineural hearing loss

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In our study, patients were divided into three groups; Group A (31–38), Group B (39–46), and Group C (47–55). Ten patients of Group A (43.4%), twenty of Group B (57.1%), and thirty patients of Group C had SNHL (71.4%) [Table 2].
Table 2: Sensorineural hearing loss and age of the patient

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Out of 100 patients, there were 62 male and 38 female patients.SNHL was found in forty male patients (64.5%) and twenty female patients (52.6%). Ratio of male and female patients was 1.2:1 [Table 3].
Table 3: Sensorineural hearing loss and sex of the patient

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  • Degree of hearing loss among Type 2 DM was also taken into account the degree of SNHL is slight (16–25 dB)/mild (26–40 dB)/moderate (41–55 dB)/severe (56–70 dB)
  • Descriptive statistics was done to measure mean and standard deviation (SD). Inferential statistics was also carried out through independent t-test to find P value.


Out of 60 cases with SNHL, 28 had slight SNHL, 22 had mild SNHL, 10 cases had moderate SNHL, and none of them had severe SNHL. Hearing loss was more common in high frequencies, but in few cases, there was loss in mid-frequencies also. In the present study, pure tone average of 500, 1000, and 2000 Hz was taken to find the degree of hearing loss. The present study followed ASHA classification of hearing loss [Table 4].[11]
Table 4: Different degrees of hearing loss in patients with Type 2 diabetes mellitus

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From [Table 5], we can see that there are 36 cases with 1–7 years duration of diabetes, among which 15 (41.6%) had SNHL. Similarly, among 43 cases with 8–14 years of duration, 29 cases had SNHL (67.4%). Among 21 cases of 15–21 years duration of diabetes, 16 cases had SNHL (76.1%). It is clearly seen that there is no relation between duration of DM and SNHL. Independent t-test shows no association between duration of diabetes and SNHL (P > 0.05).
Table 5: Sensorineural hearing loss and duration of the diabetes

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From [Table 6], we can infer that among 57 controlled patients with diabetes, 26 (45.6%) had SNHL, and out of 43 uncontrolled diabetes, 34 (79%) had SNHL. Independent t-test shows association between control of diabetes and SNHL (P < 0.05).
Table 6: Sensorineural hearing loss and glycated hemoglobin

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Mean fasting blood glucose (FBG) was higher in patients with diabetes with SNHL than in those without SNHL 175.3 (SD = 83.3) mg/dL versus 157.7 (54.9) mg/dL, but the difference was not statistically signifi cant (P = 0.247) [Table 7]. The FBG level was not significantly related to severity of SNHL, but early age at DM onset and longer duration of diabetes were related to higher severity of SNHL (P = 0.042 and P= 0.007, respectively).
Table 7: Sensorineural hearing loss and blood sugar levels

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  Discussion Top


The relationship between DM and hearing loss is controversial, primarily because the pathogenic mechanism remains obscure. This is a case–control study investigating this relationship using pure tone audiometer. Most of studies have supported association of SNHL with diabetes. The present study also supports the association of SNHL with diabetes with a prevalence of 60%. The hearing loss is usually of gradually progressive type.

The previous studies show incidence of SNHL ranging from 30% to 95%. Friedman et al.[1] showed a 55% incidence of SNHL in patients with diabetes. Weng et al. in 2005 reported a series of 68 patients with gradual onset of SNHL in diabetes.[11] Diabetes has been shown to affect hearing acuity by many studies. Many have tried to identify the cause, and based on their conclusions, the probable mechanisms are microangiopathy of the inner ear, neuropathy of the cochlear nerve, a combination of both, outer hair dysfunction, and disruption of endolymphatic potential.

This study demonstrates that diabetes affects all frequencies significantly. This could be explained by microangiopathy of the vessels to the inner ear as proposed by This study demonstrates that diabetes affects all frequencies significantly. This could be explained by microangiopathy of the vessels to the inner ear as proposed by Kakarlapudi et al.[12] and Zelenka and Kozak.[13]

Studies have found that there is no association between duration of diabetes and hearing loss.[14],[15],[16],[17] The present study supports the above conclusion. It can be concluded that not all the patients with diabetes have uncontrolled hyperglycemia during their course of the illness. Hence, rather than the duration of illness, the degree of hyperglycemia and the HbA1C levels are more important in determining the auditory acuity. Lack of glycemic control shows a positive correlation with extent of hearing loss when compared to those with diabetes with good glycemic control. High postprandial blood sugar (PPBS) levels cause a significant alteration in high-frequency hearing thresholds in patients with diabetes. Damage to outer hair cells by sustained hyperglycemia has been noted in animal studies.[5],[15],[16],[17] Currently, outer hair cell function in diabetes is an area of intense research activity.

Our study reports that the incidence of sensorineural deafness is increased in patients with diabetes. The hearing loss is a progressive, bilateral, sensorineural deafness of gradual onset which affects predominantly the higher frequencies. The decrease in hearing acuity is similar to presbycusis, but those affected show a hearing loss greater than could be expected at that age. For all the patients with diabetes with hearing loss, the threshold of hearing in both the air conduction and bone conduction started to increase from 2000 Hz. Screening of all patients with diabetes for hearing loss in a longitudinal study may provide a clearer understanding of the relationship between diabetes and hearing loss.


  Conclusion Top


Globalization is rapidly transforming India from a developing to a developed country. People have become more health conscious, and they expect to add more socially and economically productive years to their life span. This disorder which was manifesting mainly in older years of life is now manifesting in earlier years, hence it is advisable to screen for SNHL in all patients with diabetes. In all patients with Type 2 DM while examining them clinically due consideration may be given to hearing tests along with other tests such as fasting blood sugar, PPBS levels, and HbA1C level to find the glycemic control. Furthermore, it is mandatory for necessary follow-ups to be done regularly. In the present study, it was found that the patients with Type 2 diabetes had a higher hearing threshold than the healthy controls. The patients with diabetes showed significant high-frequency, bilateral, mild-to-moderate SNHL. The glycemic status had significant correlation with hearing loss may be explained by diabetic microangiopathy of the inner ear, and the hearing was affected in both sexes equally. Therefore, the auditory health of patients with diabetes is to be more carefully followed up by health-care professionals.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Friedman SA, Schulman RH, Weiss S. Hearing and diabetic neuropathy. Arch Intern Med 1975;135:573-6.  Back to cited text no. 1
[PUBMED]    
2.
Lasisi OA, Nwaorgu OG, Bella AF. Cochleovestibular complications of diabetes mellitus in Ibedan, Nigeria. Int Congr Ser 2003;1240:1325-8.  Back to cited text no. 2
    
3.
Taylor IG, Irwin J. Some audiological aspects of diabetes mellitus. J Laryngol Otol 1978;92:99-113.  Back to cited text no. 3
[PUBMED]    
4.
King H, Aubert RE, Herman WH. Global burden of diabetes, 1995-2025: Prevalence, numerical estimates, and projections. Diabetes Care 1998;21:1414-31.  Back to cited text no. 4
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5.
Harris MI. Undiagnosed NIDDM: Clinical and public health issues. Diabetes Care 1993;16:642-52.  Back to cited text no. 5
    
6.
Kurien M, Thomas K, Bhanu TS. Hearing threshold in patients with diabetes mellitus. J Laryngol Otol 1989;103:164-8.  Back to cited text no. 6
    
7.
Cullen R, Cinnamond NJ. Hearing loss in diabetes. J Laryngol Otol 1993;107:179-82.  Back to cited text no. 7
    
8.
Wackym PA, Linthicum FH Jr. Diabetes mellitus and hearing loss: Clinical and histopathologic relationships. Am J Otol 1986;7:176-82.  Back to cited text no. 8
[PUBMED]    
9.
Triana RJ, Suits GW, Garrison S, Prazma J, Brechtelsbauer PB, Michaelis OE, et al. Inner ear damage secondary to diabetes mellitus. I. Changes in adolescent SHR/N-cp rats. Arch Otolaryngol Head Neck Surg 1991;117:635-40.  Back to cited text no. 9
    
10.
Suckfüll M, Winkler G, Thein E, Raab S, Schorn K, Mees K. Changes in serum osmolarity influence the function of outer hair cells. Acta Otolaryngol 1999;119:316-21.  Back to cited text no. 10
    
11.
Weng SF, Chen YS, Hsu CJ, Tseng FY. Clinical features of sudden sensorineural hearing loss in diabetic patients. Laryngoscope 2005;115:1676-80.   Back to cited text no. 11
    
12.
Kakarlapudi V, Sawyer R, Staecker H. The effect of diabetes on sensorineural hearing loss. Otol Neurotol 2003;24:382-6.  Back to cited text no. 12
    
13.
Zelenka J, Kozak P. Disorder in blood supply of the inner ear as early symptom of diabetic angiopathy. J Laryngol Otol 1965;79:314-9.  Back to cited text no. 13
    
14.
Dalton DS, Cruickshanks KJ, Klein R, Klein BE, Wiley TL. Association of NIDDM and hearing loss. Diabetes Care 1998;21:1540-4.  Back to cited text no. 14
    
15.
Tay HL, Ray N, Ohri R, Frootko NJ. Diabetes mellitus and hearing loss. Clin Otolaryngol 1995;20:130-4.  Back to cited text no. 15
    
16.
Triana RJ, Suits GW, Garrison S, Prazma J, Brechtelsbauer B, Michaelis OE, et al. Inner ear damage secondary to diabetes mellitus. Arch Otolaryngol Head Neck Surg 1991;117:635-40.   Back to cited text no. 16
    
17.
Suckfull M, Winkler G, Trein E, Raab S, Schorl K, Mees K. Changes in serum osmolarity influence the function of outer hair cells. Acta Otolaryngol 1999;119:316-21.  Back to cited text no. 17
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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