Diabetes is especially associated with a type of hearing loss known as sensorineural hearing loss (SNHL). SNHL is caused by damage to the tiny hair cells and nerves of the inner ear that are used to sense sounds. These cells cannot repair themselves, which means that SNHL hearing loss will usually not improve on its own.
This is the most common form of hearing loss, the variant that so often causes the declining hearing of older adults. SNHL can affect one ear or both ears, in which case it may be stronger in one ear than the other. Sounds may be muffled, and it may become more difficult to perceive high voices or to navigate noisy environments or conversations with multiple people. “Hearing loss in diabetes often presents as high-frequency sensorineural hearing loss, which can develop gradually and remain unnoticed until it becomes more pronounced,” says Mittal.
Of course, people with diabetes can experience any other type of hearing loss, too. Conductive hearing loss occurs when sounds are blocked or muffled in the middle or outer ear. This is often due to physical factors such as ear wax, fluids, foreign objects, or bone abnormalities. Diabetes does not increase the risk of conductive hearing loss.
It is possible to experience conductive hearing loss and SNHL at the same time. This is known as mixed hearing loss. Mixed hearing loss can be due to multiple independent but simultaneous causes, or to single factors such as head trauma or illness that damage both the inner and middle or outer parts of the ear at the same time.
People with diabetes also have a higher risk of tinnitus, a persistent ringing or buzzing sound that is unrelated to external noises. Tinnitus, which is not technically a form of hearing loss, often occurs at the same time as hearing loss. Diabetes-related tinnitus is probably another consequence of nerve damage to the inner ear.
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