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Is Diabetes Linked to Hearing Loss?
For several years now, researchers have been studying the relationship between diabetes and hearing loss.
Multiple authors have found a higher proportion of hearing loss in people with diabetes than those without the condition.
While scientists aren’t quite in agreement, scientific literature generally indicates that diabetes—particularly when blood sugar is poorly controlled—is a risk factor for hearing loss. Even though the statistical connection between the two conditions is becoming better documented, we still don’t know exactly how they are related.
How Does It Work?
Diabetes is a metabolic problem that causes too much sugar to remain in the blood. The body then produces too much glycated hemoglobin, which builds up on the walls of smaller blood vessels. This, combined with the resulting immune response, leads to the thickening of the walls and reduced permeability, leaving less room for blood to circulate. As such, tissues (nerves, organs, etc.) that rely on those blood vessels end up damaged because they are not receiving enough blood. This chain reaction is the cause of some well-known complications of diabetes, like peripheral neuropathy.
Smaller blood vessels are especially vulnerable, which is why it is believed that a similar reaction affects the inner ear. The most plausible theory is that the auditory nerve and parts of the cochlea become damaged. In diabetics taking insulin, researchers have noted differences in the cochlea, more specifically a thickening of the blood vessel walls in the stria vascularis and basilar membrane (parts of the cochlea), atrophy of the stria vascularis and a loss of cells in the spiral ganglion. Other authors have also found indicators of poorly functioning external cilia (in the inner ear).
The link between diabetes and hearing loss is especially difficult to prove because age is often a factor as well. Some researchers believe that presbycusis can mask complications of diabetes in the inner ear. After all, it has been found that blood microcirculation in the cochlea is affected over time, causing the tissues to receive poor blood supply. This is similar to the way diabetes affects the inner ear.
Typically, hearing loss in people with diabetes is progressive, bilateral and sensorineural, and it mostly affects higher frequencies. Some scientists also believe that central auditory processing may also be affected, leading to trouble hearing in noisy environments despite generally normal hearing acuity. Hearing loss, especially when it is bilateral and progressive, can easily go unnoticed, even though it may greatly affect communication. For that reason, it’s a good idea for people with diabetes to visit an audiologist, who can assess hearing acuity and make recommendations as needed.
References: CRUICKSHANKS, K. J. et al. Smoking, Central Adiposity and Poor Glycemic Control Increase Risk of Hearing Impairment. JournalAm Geriatr Soc., 63(5): 918-924. 2016. FUKUSHIMA, H., CUREOGLU, S., SCHACHERN, P. A. et al. Cochlear changes in patients with type 1 diabetes mellitus. Otolaryngol Head Neck Surg, 133:100-6. 2005. HANDZO, D. J., RAMACHANDRAN, V. S., STACH, B., PETERSON, E. and YAREMCHUK, K. L. The Effect of Glycemic Control on Hearing Loss. Annals of Otolaryngology and Rhinology, 3(4): 1098. 2016. HORIKAWA, C., KODAMA, S., TANAKA, S. et al. Diabetes and risk of hearing impairment in adults: a meta-analysis. J Clin Endocrinol Metab, 98:51-8. 2013. Other references upon request