Philadelphia, June 17, 2008 - Hearing impairment is common in adults with diabetes, and diabetes seems to be an independent risk factor for the condition according to a study published today on the Web site of Annals of Internal Medicine.
"We found that hearing loss was much more common in people with diabetes than people without the disease," says Kathleen E. Bainbridge, PhD, the study's lead researcher. "The hearing loss we detected did not seem to be caused by other factors such as exposure to loud noises, certain medicines, and smoking."
Using the National Health and Nutrition Examination Survey, collected by the National Center for Health Statistics from 1999 to 2004, the researchers analyzed data from 5,140 adults aged 20 to 69 who completed an audiometric examination and a diabetes questionnaire.
Hearing impairment was more prevalent among adults with diabetes. Age-adjusted prevalence of low- or mid-frequency hearing impairment of mild or greater severity assessed in the worse ear was 21.3 percent among 399 adults with diabetes compared to 9.4 percent among 4,741 adults without diabetes. These differences in hearing between people with and without diabetes were present in both sexes; all groups of race or ethnicity, education, and income; and all age groups but the oldest.
Similarly, age-adjusted prevalence of high-frequency hearing impairment of mild or greater severity assessed in the worse ear was 54.1 percent among adults with diabetes compared to 32 percent among adults without diabetes.
Diabetes, which can damage small blood vessels and nerves in the body, affects an estimated 9.6 percent of the U.S. adult population.
"It is possible that high blood sugar levels damage the small blood vessels and nerves of the inner ear, resulting in hearing impairment," says Bainbridge. "People with diabetes might benefit from having their hearing checked."
Hearing impairment was assessed from the pure tone average of thresholds over low or mid-frequencies (500; 1,000; and 2,000 Hz) and high frequencies (3,000; 4,000; 6,000; and 8,000 Hz) and was defined as mild or greater severity (pure tone average greater than 25 decibels hearing level and moderate or greater severity (pure tone average greater than 40 decibels hearing level). Hearing loss is reported by more than 17 percent of the U.S. adult population.
The editors of Annals of Internal Medicine caution that diabetes was self-reported and was verified in only a small fraction of participants, and the researchers did not distinguish between type 1 and type 2 diabetes. Noise exposure was based on participant recall.
In an accompanying editorial, Keiko Hirose, MD, of Washington University, writes, "We have few current therapeutic options for progressive hearing loss from any cause, and the study of hearing loss in diabetic patients could lead to important progress in new techniques of studying and treating microvascular disease of the inner ear."