With commentary by Elizabeth Purchase Helzner, PhD, assistant professor of epidemiology, SUNY Downstate Medical Center.
If you have type 2 diabetes, you already know to practice heart-healthy habits due to higher heart disease risk and to watch for complications such as nerve problems or neuropathy. Now, growing research suggests you need to be on the lookout for hearing loss.
"It seems that people with diabetes, based on the evidence we have, are 40 to 80% percent more likely than those without diabetes to have hearing loss in the frequency range that is important for understanding speech," says Elizabeth Purchase Helzner, PhD, assistant professor of epidemiology at SUNY Downstate Medical Center. She reviewed published studies that focused on diabetes and hearing loss, concluding that the evidence of a link is convincing. The review, co-authored by Kevin Contrera, a researcher at Johns Hopkins University, is published in Current Diabetes Reports.
The researchers looked at both large-population based studies and smaller studies. Not all of the studies found an association, but in some of the smaller studies the increased risk of hearing loss in those who had diabetes was even greater, more than 90%.
The studies cover a wide age span, and the finding of hearing loss in the younger people with diabetes, Dr. Helzner says, suggests there is an explanation other than age-related hearing loss. Based on those and other findings, Dr. Helzner says, doctors should include hearing tests as part of the medical management of type 2 diabetes.
While Dr. Helzner found what she considers convincing evidence, she stressed that she have found an association, or link, but cannot prove cause and effect. There is a need, she says, to launch studies looking at those with and without diabetes and follow them over time, to see how their hearing holds up.
Meanwhile, she says, she has three potential explanations for why those with diabetes are more vulnerable to hearing loss. Damage to the small blood vessels that supply the inner ear (from high blood glucose) is one explanation, she says. Damage to the nerves that supply the auditory system may also contribute, as well as damage to the mitochondria, the cell's power house, in cells in the auditory system.
The link found between diabetes and hearing impairment does not surprise Gerald Bernstein, MD, an endocrinologist and coordinator of the Friedman Diabetes Program at Lenox Hill Hospital. Dr. Bernstein is also a former president of the American Diabetes Association.
The auditory nerve, he says, ''is going to be subjected to the same vicissitudes as other nerves." If there is any suspicion of hearing loss, it's important to be tested, Dr. Bernstein says.
The studies, so far, have produced mixed results on whether diabetes increases the risk of hearing loss, says Kourosh Parham, MD, PhD, an otolaryngologist and associate professor in the division of otolaryngology at UConn Health in Farmington. While cause and effect have not been proven, he says, the evidence is strong enough to be concerned.
"I agree with the authors that further systematic investigation is needed to establish the link between diabetes and hearing loss," he says. Meanwhile, he offers several recommendations for anyone with diabetes—control blood sugar, control risk factors for heart disease such as obesity and minimize exposure to loud noises. He also recommends having a formal hearing test (audiogram). If the results show no significant or mild loss, he says, repeat the test in one to three years, shortening the interval as you age. If significant hearing loss is found, he advises using hearing aids or other devices.
On its webpage, the American Diabetes Association notes the research linking diabetes and hearing loss. It also urges those with diabetes to talk to their primary care doctor if they suspect a hearing loss. Your doctor, in turn, may refer you to a hearing specialist such as an audiologist for hearing tests or to a doctor who is a specialist in diagnosing hearing loss.
To detect hearing loss, "I think it’s important to have a much closer screening of people with diabetes," Dr. Helzner says. If there is a change in hearing, she says, it is ideal to catch it early. While it may not be possible to reverse the loss, correcting it with hearing aids or other devices can keep people socially engaged, she says.
Hearing loss often results in people socializing less and becoming less engaged in life as they struggle to understand conversations, she says. That isolation, in turn, is linked with cognitive decline. "The idea is, if you can keep people functioning, when it comes to hearing, you can prevent some of these problems," Dr. Helzner says.
Often, the person with hearing loss is unaware until a friend or loved one points it out, according to the American Academy of Otolaryngology—Head and Neck Surgery. Its website has a quick test to help you decide if your hearing might be declining.