Possible correlation between diabetes and hearing loss

The link between diabetes and auditory decline has long been hypothesized. Now, preliminary findings indicate that people with this illness show signs of hearing loss at younger ages than those without it.

"There are so many microvascular and neuropathic complications with diabetes," said Nancy Vaughan, PhD, lead author and a research investigator at the Dept. of Veterans Affairs National Center for Rehabilitative Auditory Research in Portland, Ore. "It just seems logical that there should be some effect on hearing." The study was presented in February at the midwinter meeting of the Assn. for Research in Otolaryngology in Daytona Beach, Fla.

Diabetes experts have long thought that the same kind of destruction wrought by the illness on the kidneys, eyes, heart and nerves may also be occurring in the auditory system. Several epidemiological studies have suggested that hearing loss may also be more common in this population.

"In retrospect, this may explain why we give people directions and they just don't follow them," said James Mulinda, MD, chief of the diabetes and endocrinology section at Pennsylvania Hospital in Philadelphia. "Maybe they didn't hear half of what you said."

Those who focus on this question, however, have struggled to separate diabetes-related decline from the diminishing function that could be related to age or cardiovascular problems -- both of which are also common in this patient group.

Dr. Vaughan's team tested the auditory function of nearly 700 veterans with and without the disease. They found that for those younger than 60 with diabetes, hearing loss was more severe than for the same age group without diabetes. Differences in those 60 and older were not statistically significant at most frequencies. They concluded that diabetics' auditory system may grow older faster and that past a certain age hearing loss may be obscured by the aging process.

"If you're under 60 and diabetic, you're more likely to have hearing loss," said Dr. Vaughan. "But we don't know yet what this means in terms of all the other factors that need to be considered, such as heart and vascular disease. There's a long way to go, but we have some really solid evidence that there are differences."

Researchers and other experts suggested that this study may lead to an eventual role for auditory screening for diabetics. Specifically, it could become a useful measure of neuropathy for which there is yet no good screening test. It could also serve as an indication that the disease is not as well-controlled as it should be.

"We're probably going to find that it makes sense to screen diabetics early for very high frequency hearing loss," said Sujana Chandrasekhar, MD, director of otology and neurotology at Mount Sinai School of Medicine in New York. "These aren't necessarily frequencies that pertain to how we appreciate environmental sound, but they may be precursors that tell us this person needs to be in better control."

Others maintained that while the data, which were in the form of an interim analysis, were interesting, it was far too soon for diabetics to start being concerned about their hearing. Findings should be finalized by the end of this month.

"It's an interesting study, and it's preliminary data, but it's certainly not at a point where it would cause any change in care or the need for further tests," said Nathaniel Clark, MD, national vice president for clinical affairs at the American Diabetes Assn.

Some did say that possible concerns about hearing should be one more reason for diabetics to better control their disease and for those who don't to work towards prevention.

"If we could convince people of the multiple implications of this disease on their entire function, I think they'd deal with it differently," said Dr. Vaughan.