Pemmaiah K.D , Srinivas D.R
Background: The complex arrangement of inner ear makes it potential target of hyperglycaemic damage. A study was conducted to identify the probable occurrence of hearing loss as a complication of Diabetes Mellitus (DM).
Aims and objective:
• To assess the hearing loss in type 2 diabetic patients and correlate with age, duration of diabetes, HbA1C.
• To correlate hearing loss with nerve conduction study.
Design: Cross sectional study was done involving randomly 110 Type 2 DM patients. Data regarding their age and duration of diabetes was collected. Pure tone Audiometry and Nerve conduction study was done. HbA1c level determined. Data statistically analysed using Pearson correlation coefficient.
Results: Out of 110 patients 48 patients (43.6%) had bilateral Sensorineural hearing in higher frequency (2000hz, 4000hz). Among them Severe hearing loss (71 dB to 90dB) was seen in 7 patients (6.36%), moderately severe hearing loss (61dB to 70dB) in 16 patients (14.54%) and moderate hearing loss(30dB to 60 dB) in 25 patients (22.7%). Among 47 patients who had diabetes for more than 10 years, 29 patients (61.7%) showed at least mild hearing loss. Duration of DM and sensorineural hearing loss at 2000Hz and 4000Hz showed statistically significant correlation (Pearson coefficient r= 0.561 and r= 0.727 respectively) at 0.01 level. In other frequencies no significant correlation was found. Coefficient of determination was r2=0.31(31%) and r2=0.52(52%) respectively between duration of DM and hearing loss at 2000Hz and 4000Hz. The correlation of hearing loss in lower frequency with HbA1c did not show any statistical significance. However HbA1c and hearing loss in higher frequency (2000 hz and 4000hz) showed statistically significant correlation (Pearson coefficient r= 0.282 and r= 0.385) respectively. The correlation of hearing loss with Nerve conduction study did not show any statistical significance.
Study Limitation: Longitudinal study involving larger sample size and wide geographical area would confirm the above results.
Conclusion: We concluded that progressive bilateral high frequency sensorineural hearing loss is a complication of DM and probably due to involvement of inner ear structures particularly hair cells with preservation of vestibulocochlear nerve functions. However hearing loss is unrelated to development of peripheral neuropathy. Further study needs to be conducted to confirm the mechanism of hearing loss.
