Half of the 11,405 study participants were randomly assigned a hearing test, and nearly 90 percent of them completed the hearing exam and diabetes questionnaire. The test measured participants’ ability to hear low, middle, and high frequency sounds in both ears. Participants were asked if they had a little trouble hearing, a lot of trouble hearing, or were deaf without a hearing aid. In addition, 2,259 of the participants who received the hearing tests were randomly assigned to have their blood glucose tested after an overnight fast.
“Using the data from the hearing tests, we measured hearing impairment in eight different ways,” said Catherine Cowie, PhD, of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The study, the first nationally representative investigation of adults aged 20 to 69, found an association between diabetes and hearing impairment in people as young as 30 years. A link between diabetes and hearing loss was seen across all frequencies, with more people reporting hearing difficulty in the high frequency range. Even adults with prediabetes had a 30 percent higher rate of hearing loss compared to those with normal blood sugar after an overnight fast.
Although earlier studies have found a less meaningful association between diabetes and hearing problems, they were based on smaller samples of older adults and were not nationally representative.
It is thought that diabetes leads to hearing loss by damaging the nerves and blood vessels of the inner ear. Autopsy studies of diabetes patients have shown evidence of such damage. “As diabetes becomes more common, the disease may make a more significant contribution to hearing loss,” said Cowie.