The new study, led by Johns Hopkins researchers and published in the Nov. 14 Archives of Internal Medicine, is thought to be the first to estimate hearing loss on the national scale rather than on specific cities or populations.
Researchers utilized the National Health and Nutritional Examination Surveys (NHANES), a research program to analyze data from all participants age 12 and over whose hearing was tested during NHANES examinations from 2001 to 2008. Unlike previous estimates, NHANES includes men and women of all races and ages and from cities scattered across the country. It therefore is considered to statistically mimic the U.S. population.
Using the World Health Organization's definition for hearing loss (not being able to hear sounds of 25 decibels or less in the speech frequencies), the researchers found that overall, about 30 million Americans, or 12.7 percent of the population, had hearing loss in both ears. That number jumped to about 48 million, or 20.3 percent, for people who have hearing loss in at least one ear. These numbers far surpass previous estimates of 21 to 29 million.
"This gives us the real scope of the problem for the first time and shows us how big of a problem hearing loss really is," said study leader Frank Lin, M.D., Ph.D. Lin is an assistant professor with dual appointments in both the Department of Otolaryngology-Head & Neck Surgery at the Johns Hopkins School of Medicine and in the Department of Epidemiology at the Johns Hopkins Bloomberg School of Public Health.
Hearing loss prevalence nearly doubled with every age decade. Women and African Americans, however, were significantly less likely to have hearing loss at any age. Researchers could not conclude why these groups appear to be protected, but it is possible that the female hormone estrogen, as well as the melanin pigment in darker skin, could have a protective effect on the inner ear.