News & Research

Increased Inner Ear Susceptibility to Noise Injury in Mice With Streptozotocin-Induced Diabetes, Takeshi Fujita and colleagues. Diabetes, 61:2980–2986, 2012

What is the problem and what is known about it so far?

Research suggests that diabetes is a risk factor for hearing loss. Studies that have tried to determine the underlying connection between diabetes and hearing loss have reported inconsistent results.

Why did the researchers do this particular study?

The researchers in this study aimed to determine whether diabetes causes anatomical changes that promote hearing loss, and whether these changes occur over time or are triggered by loud sounds.

Who was studied?

The study included normal mice and those with streptozotocin-induced diabetes. Streptozotocin is toxic to the beta cells in the pancreas that make insulin, so the diabetes that develops in rodents treated with the chemical is similar to type 1 diabetes.

How was the study done?

Researchers tested the hearing of the mice 1, 3, and 5 months after inducing diabetes in half the rodents. They then subjected the mice to loud noises and tested their hearing again. In addition to hearing tests, the researchers checked for evidence of damage by counting the nerve cells that transmit sounds from the ear to the brain and by measuring blood flow in the ear.

What did the researchers find?

The ears of mice with and without diabetes looked similar at the 1-, 3-, and 5-month time points, plus they performed similarly on hearing tests. Once the mice were subjected to a loud noise, however, differences began to emerge. The mice with diabetes started to hear less well, had less blood flow in the ears, and had fewer sound-sensing cells than the mice without diabetes.

What were the limitations of the study?

This is an animal study, so the results may not be applicable to humans. Also, the study included only a few mice.

What are the implications of the study?

The results suggest that diabetes makes ears more susceptible to noise-related damage. Diabetes is known to damage blood vessels, which may be what causes the reduced blood flow. Without adequate blood flow, ear cells may not get enough nutrients, which could lead to cell death and hearing loss. It may be prudent for people with diabetes to avoid loud noises and wear ear plugs as necessary to protect the ears.

FOR MORE INFORMATION

Diabetes and Hearing Loss

National Institute on Deafness and Other Communication Disorders

The Uncomplicated Guide to Diabetes Complications