Impact of glycemic control and duration on hearing impairment in diabetics

 

Nickitha Veereddy¹, Soumya Singh^2*, Gaveshani Mantri³, A K Garg⁴

 

Abstract              Background: Diabetes mellitus is a non-communicable chronic disease with numerous complications, hearing impairment is one of the less known complications. The biggest impact of the disease is on adults of working age. The present study is planned to evaluate hearing loss in subjects with type 2 diabetes mellitus (controlled and uncontrolled) and the resulting audiometric pattern in the present population. Material and method: This was a prospective observational study done for 2 years (2015-2017) in 128 Type 2 diabetes mellitus patients according the inclusion and exclusion criteria of the study. The blood investigation for diabetes mellitus included fasting blood sugar, random blood sugar, postprandial blood sugar, and HbA1C. The disease was graded as controlled and uncontrolled, depending on the HbA1C value. The duration of diabetes mellitus was also categorized into three subgroups: < 5 years, 5-10 years, and > 10 years. Hearing impairment was measured using Pure Tone Audiometry (PTA). The statistical analysis was done using SPSS (Statistical packages for Social Sciences) Version 18.0 software. Result: The mean age of the study population was 44.48± 5.47 years. Total prevalence of SNHL is 71.09% in diabetics, of which patient’s aged between 40-50 showed maximum prevalence. The uncontrolled group has more prevalence of SNHL (80.68 %) than the well-controlled group (50%) and prevalence was also high in those patients who presented with duration of more than 10 years (100%) while less in those with less than 5 years (50.7%). Conclusion: The study emphasizes importance of metabolic assessment for patients presenting with hearing loss so as to reduce the high rate of undiagnosed diabetes mellitus in the community. And also the need of early evaluation of auditory impairment in diagnosed diabetes mellitus cases and use of audiological tests to monitor diabetic patients should be considered a routine procedure.

Keywords: Diabetes mellitus, Hearing loss, SNHL.

 

INTRODUCTION

The relationship between diabetes mellitus (DM) and sensorineural hearing loss (SNHL) has been a subject of debate since Jordao (1857) reported a case of hearing impairment with incipient diabetic coma¹. Edgar in 1915 was the first to report a high-frequency SNHL in a diabetic patient². Till now, the most widely accepted concept is the hyperglycemia-induced oxidative stress and nitrosative stress. This stress results in dysfunction at the endothelium and destruction of DNA at the cellular level and may lead to vascular ischemia in the neural tissue leading to demyelination and organ dysfunction. The microangiopathic changes are also studied in animal models to detect the auditory system's failure in diabetes mellitus³. The typical hearing loss in diabetes is a progressive bilateral sensorineural type deafness of gradual onset, which affects predominantly higher frequencies. The prevalence and its adverse health effects have increased more rapidly in South Asia than in any other world region⁴. Untreated hearing loss can negatively impact the social and emotional wellbeing of individuals, thus hampering the economy of developing countries⁵.  The effects of different variables such as duration of diabetes, blood sugar control, and the presence of end-organ damage on hearing loss have not yet been clarified, despite several studies on this topic. Furthermore, the most extensive studies in this area as described in the medical literature have examined several patients but still limit the conclusion because of insufficient statistical power⁶.Hence, the present study evaluates hearing loss in subjects with type 2 diabetes mellitus (controlled and uncontrolled) and the resulting audiometric pattern in central India's population.

              

MATERIAL AND METHODS

This prospective observational study was conducted in the Department of Otorhinolaryngology at Jawaharlal Nehru Hospital and Research Centre, Bhilai, from June 2015 to May 2017. About 128 patients attending ENT OPD (outpatient department) with a history of hearing loss and diabetes mellitus were enrolled in the study, fulfilling inclusion and exclusion criteria. The ethical and scientic society of the institution has given the ethiiical clearance for the study. After a patient has given written informed consent, a detailed history was taken regarding diabetes mellitus and hearing loss along with the detailed physical examination of the external ear, tympanic membrane, and eighth cranial nerve examination. The audiometric evaluation included Pure Tone Audiometry (PTA), using a calibrated Interacoustics Clinical Audiometer ELKON eda 3 N 3 multi with RadioEar B 71 bone vibrator to assess the hearing loss. The blood investigation for diabetes mellitus included fasting blood sugar, random blood sugar, postprandial blood sugar, and HbA1C. The disease was graded as controlled and uncontrolled, depending on the HbA1C value. The duration of diabetes mellitus was also categorized into three subgroups: < 5 years, 5-10 years, and > 10 years.

Inclusion Criteria:

1. Patients diagnosed with Type 2 diabetes mellitus as per The National Diabetes Data Group and the World Health Organization issued diagnostic criteria.
2. Patients Random blood glucose concentration >200 mg/Dl, Fasting plasma glucose >126 mg/dL
3. Patients greater than 18 and less than 55 years old. 

Exclusion criteria:

The patients with the following features were excluded from the study-

1. Subjects with history of chronic exposure to noise, trauma to the ear, any chronic ear disease, family history of hearing loss.
2. Subjects with hypertension, hyperlipidemia, any other chronic liver, and kidney diseases. 
3. Subjects with the history of ototoxic drugs intake and cranial nervous system sedatives in the past 2 month.

Analysis of data (statistical methods employed):

The statistical analysis was done using SPSS (Statistical packages for Social Sciences) Version 18.0 software. Pearson chi-square value and p-value has been estimated in our study and tried to find the correlation between different variables of diabetes mellitus and SNHL.

 

RESULTS
The characteristics of the study cohort have been shown in table 1,graph 1. Age group 40 to 50 years was in the majority comprising 66.41%, while patients in the age group < 40 years were only 20.31 % and > 50 years were 13.28 %. The mean age of the study population was 44.48± 5.47 years. There were 54.69 % males, and 45.31 % were females in our study. The duration of diabetes in our cohort was analyzed; a maximum of 71 (55.47%) patients presented with < 5 years duration, 49 (38.28%) patients with 5- 10 years duration, and 8 (6.25%) patients with >10 years duration. The mean duration of the DM in the study population was 4.70 ± 3.65 years. In the present study, the mean random blood sugar was 250.008 ± 43.28 mg/dL, the mean fasting blood glucose level was 158.07 ± 31.27 mg/dL, and the mean postprandial blood glucose level was found to be 228.93 ± 48.73 mg/dL. The mean HbA1C was 7.05 ± 1.071 in our study. In this study, a family history of diabetes was present in 31.25 % of the patients, while most of the patients (68.75 %) had no family history. The severity of hearing loss was minimal in 23.44 %, mild in 32.81 %, moderate in 8.59%, and moderately severe in 6.25%. When we analyzed the prevalence of SNHL in patients, it was found to be 71.09% of which patients age between 30-35 years, 35-40 years, 40-45 years, 45-50 years, 50-55 years were 22.22%, 58.82%, 76%,83.33%, 58.82% respectively and it was found to be statistically significant (p<0.01)(table 2, graph 2). We tried to evaluate the association between different diabetes parameters as random blood sugar (RBS) and fasting blood sugar (FBS) with hearing loss. As shown in the table and figure(table ,Graph 3a,3b), the maximum number of patients with RBS >250 mg/dL had 81.82 % hearing loss, and patients with RBS <200 mg/dL, the hearing loss was only 65.48%, which was not significant (p=0.27). Patients with the FBS >150mg/dL had hearing loss in 81.03% compared to 62.86% with FBS 126-150mg/dL which was also not statistical significant (p <0.09). These observations suggest that these values of the sugar estimation do not correlate with hearing loss. When we took HbA1C as a variable and assessed the correlation with hearing loss, we found that the uncontrolled group has more prevalence of SNHL (80.68 %) than the well-controlled group (50%). This result was highly significant (p=0.0036) in our study, shown in Table 4 and Graph 4. The other variable which was found significant was the duration of diabetes and the prevalence of SNHL. Prevalence was high in those patients who presented with a duration of more than ten years (100%) while less in those with less than five years (50.7%). (table 5,Graph 5) This difference was statistically significant (p<0.001). (Table 6) The prevalence of SNHL was also significantly high in patients with a family history of diabetes (77.5 %) compared to those with no family history (68.18 %) (p=0.12).

 

Table 1

(*) 30-35 does not include 35 ie upper limit

 

GRAPH -1

Graph 1: Percentage age distribution       Graph 2: Percentage gender distribution

 TABLE 2: Association of age with SNHL

 

GRAPH 2: Distribution of hearing loss                               GRAPH-3 a: Association of SNHL GRAPH 3b: Association of SNHL

according to age                                                                          with RBS                                                            with RBS

 

 

 

TABLE 4: Association of SNHL with HbA1c

 

GRAPH 4: Association of SNHL with HbA1c

 

TABLE 5 : Association of duration of diabetes with SNHL

 

GRAPH 5: Distribution of hearing loss according to duration in years

 

Table 6: Association of SNHL with family history of diabetes

 

Graph 6

 

 

 

 

 

 

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