Hearing loss is about twice as common in adults with diabetes compared to those who do not have the disease, according to a new study funded by the National Institutes of Health. "Hearing loss may be an under-recognized complication of diabetes. As diabetes becomes more common, the disease may become a more significant contributor to hearing loss," said senior author Catherine Cowie, Ph.D., of the National Institute of Diabetes and Digestive and Kidney Diseases, who suggested that people with diabetes should consider having their hearing tested.
"Our study found a strong and consistent link between hearing impairment and diabetes using a number of different outcomes."
The researchers discovered the higher rate of hearing loss in those with diabetes after analyzing the results of hearing tests given to a nationally representative sample of adults in the United States. The test measured participants' ability to hear low-, middle- and high-frequency sounds in both ears.
The link between diabetes and hearing loss was evident across all frequencies, with a stronger association in the high-frequency range.
Adults with pre-diabetes, whose blood glucose is higher than normal but not high enough for a diabetes diagnosis, had a 30 percent higher rate of hearing loss, compared to those with normal blood sugar tested after an overnight fast.
The study was published online in the Annals of Internal Medicine. The researchers analyzed data from a hearing test administered to 11,405 participants aged 20 to 69. The test measures hearing sensitivity across a range of sound frequencies.
Earlier U.S. studies that examined diabetes and hearing loss found a weaker association or no association, but these studies were based on smaller samples of older adults, and they were not nationally representative, according to epidemiologist Howard Hoffman.
"This is the first study of a nationally representative sample of working age adults, 20 to 69 years old, and we found an association between diabetes and hearing impairment evident as early as ages 30 to 40."
Diabetes may lead to hearing loss by damaging the nerves and blood vessels of the inner ear, the researchers suggest. Autopsy studies of diabetes patients have shown evidence of such damage.
Afflicting more than 20 million people in the United States, diabetes is a major cause of heart disease, stroke, blindness, kidney failure and lower limb amputations.
For information about the causes, prevention and treatment of diabetes, see http://diabetes.niddk.nih.gov.