Hearing Loss and Diabetes

The global prevalence of diabetes in the U.S. is estimated to be 9% among adults, and according to the Center for Disease Control (CDC), diabetes will affect nearly one third of the world’s population by the year 2050 (CDC, 2014). It is reported the prevalence is rising and predictions also suggest that by the year 2025, there will be a 57% increase in the prevalence of diabetes in North America. Nearly 30 million people in the U.S. currently have diabetes and 86 million adults have prediabetes (CDC).

Diabetes mellitus is a group of diseases which includes altercation in glucose metabolism which ultimately results in elevated blood glucose levels. Diabetes can be classified as Type 1 or Type 2. When beta cells of the pancreas no longer make insulin, Type 1 diabetes is evident. When the pancreas continues to make insulin but a cellular impairment in sensitivity to insulin causes raised blood glucose levels, Type 2 diabetes is apparent (Bainbridge, 2010). Bainbridge reports that adults with diabetes can experience cardiovascular disease risk factors such as hypertension and high cholesterol, and diabetic retinopathy, which is the leading cause of blindness in the U.S. Diabetes is the leading cause of kidney failure among Americans. Severe diabetic nerve disease is a major cause of lower extremity amputations. Since diabetes is a systemic disease that affects multiple sense organ systems, it is reasonable to question whether the auditory system or hearing is affected.

The National Institutes of Health (2008) found that hearing loss is twice as common in adults with Type 2 diabetes as with those who do not have the disease. The link between hearing loss and diabetes was found at all frequencies, but a somewhat stronger association was found in the high-frequency range. The study found 54% of those with diabetes reported hearing loss for high frequency sounds as compared with 32% of those without diabetes. Bainbridge also found a stronger link between diagnosed diabetes and hearing loss in younger people than older people. U.S. data suggests that in those 50-69 years old with diabetes, 70% have high-frequency hearing loss and one-third have low or mid-frequency hearing impairment.
Why is hearing loss twice as common in adults with Type 2 diabetes?

Although the reason is speculative, some researchers suggest it may be due to poor circulation. The elevated blood sugar levels associated with Type 2 diabetes can damage to blood vessels and reduce blood flow which could damage the structure of the inner ear. Since the inner ear does not have a back-up supply of blood flow, in cases with diabetes, permanent damage to the blood vessels in the inner ear could occur. The American Diabetes Association suggests the higher percentage of glycated hemoglobin can increase the risk for hearing loss because high blood sugar damages blood vessels throughout the body, including the ears. Post-mortem studies of diabetic patients have shown damage to nerves and blood vessels of the inner ear.

Studies have found:

Sclerosis of the internal auditory artery
Thickened capillaries of the stria vascularis
Atrophy of the spiral ganglion
Demyelination of the eighth cranial nerve
Loss of outer hair cells (Bainbridge, 2010)

Recommendations

Patients with diabetes should maintain good blood glucose control in accordance with the guidelines from the American Diabetes Association.
Diabetic individuals should avoid tobacco use as smoking increases the risk of cardiovascular disease which could further compound the risk of hearing damage (Bainbridge).
All patients with diabetes should have their hearing tested annually. The earlier hearing loss is detected, the more effective hearing aids are likely to be.

References

American Diabetes Association. (2010). Standards of medical care in diabetes. Diabetes Care, 3. S11-S61
Bainbridge, K. (2008). Diabetes and hearing impairment: An epidemiological perspective. American Speech-Language-Hearing Association.
Center for Disease Control. (2014). Diabetes prevalence
National Institutes of Health News (2008). Hearing loss in common in people with diabetes