Evaluation of Sensorineural Hearing Loss in Iraqi Diabetic Patients

Abstract

Background: Diabetes mellitus is associated with alterations in metabolism of carbohydrates, proteins and fats with excessive atherosclerosis resulting in long term complications mainly in heart, kidney, retina and nerves. The majority of the studies on the impact of diabetes mellitus on the hearing had been performed in western countries. The relationship between diabetes mellitus and sensorineural hearing loss (SNHL) in Iraqi population is yet to be established

Objective: This study was designed to evaluate hearing threshold in diabetic patients and severity of sensorineural hearing loss in patients with diabetes mellitus at selective frequencies.

Methods: This study was conducted at the Department of Physiology and Medical Physics at the Medical College of Al-Mustansyriah University in co-operation with the department of Otolaryngiology at Al Yarmouk Teaching Hospital. The period of study extended from March to August 2004. Hundred healthy subjects served as control groups and 101 diabetic patients were involved in this study. All were examined for evaluation of hearing threshold and sensorineural hearing loss at different hearing intensity levels. The duration, type of diabetes, and the degree of metabolic control were all tested for their influential effect on hearing loss severity.

Results: The mean hearing threshold of audible pure tone sound at low frequency at 250 Hz was 15.3 + 5.5 decibel (dB) in the diabetic group which was significantly (P90.001) higher than the healthy control subjects (12.7 + 5.2 dB). At conversational frequencies (500, 1000, and 2000 Hz) the mean of hearing threshold was 15.4 ± 5.9 dB, 17.2 ± 6.8 dB, and 19.5 ± 9.8 dB respectively in diabetes mellitus patients which was significantly (P 90.001) higher than in healthy control subjects (12.5 ± 4.9 dB, 15 ± 5 dB, and 15.4 ± 5.7 dB respectively).  At higher frequencies (4000 and 8000 Hz) the hearing threshold in diabetic patients was 26.3±13.3 dB and 26.7 ± 14.5 dB respectively which was significantly (P90.001) higher than in healthy subjects (19 ± 7.9 dB and 18.2 ± 9.2 dB respectively). Among the total of 101 diabetic patients tested for hearing threshold at low frequency, 6 cases (5.9%) had mild to moderate sensorineural hearing loss, at conversational frequencies there were 13 cases (12.9%), while at high frequencies there were 49 cases (48.5%). In contrast, in healthy subjects there were only 2 (2%), 8 (8%), and 24  (24%) cases of all having mild to moderate sensorineural hearing loss  at the corresponding frequencies mentioned above

Conclusion: The study showed that the risk of developing sensorineural hearing loss in diabetic patients at low and intermediate pure tone sound frequencies was low and statistically insignificant compared to healthy subjects. This risk was profound at high frequencies and was approximately three times in diabetics than in healthy subjects (P 90.001). Long duration of diabetes with poor glycemic control seems to exert hazards on having sensorineural hearing loss in diabetic patients. Sensorineural hearing loss (SNHL) was neither affected by the type of diabetes, nor by the duration of diabetes mellitus nor by the modality of therapy used to correct hyperglycemia
 
Keywords: Diabetes mellitus, Sensorineural hearing loss, Hearing threshold