Even with an aging population, hearing loss among U.S. adults aged 20 to 69 has declined over the past decade, according to a new study published last week by the National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health.

The researchers found that in 2011 and 2012, about 14 percent of Americans — some 27.7 million — had a hearing impairment. That was down from 16 percent, or 28 million, from 1994 to 2004.

Men had nearly twice the rate of hearing loss (18.6 percent) than women (9.6 percent), and as expected, rates increased with age. About 39 percent of those in their 60s has some hearing impairment.

The researchers defined hearing loss as not being able to hear sounds up to 25 decibels, about as loud as rustling leaves or a whisper.

The researchers said the trend may mean individuals are now starting to develop hearing loss at a later age. That could be due to less exposure to occupational noise, with fewer manufacturing jobs and more use of hearing protection. The decline could also reflect lower smoking rates or better control of diabetes and high blood pressure, all of which has been linked to hearing loss.

“Our findings show a promising trend of better hearing among adults that spans more than half a century,” said Howard Hoffman, an epidemiologist with the deafness institute and lead author of the study. “The decline in hearing loss rates among adults under age 70 suggests that age-related hearing loss may be delayed until later in life. This is good news because for those who do develop hearing loss, they will have experienced more quality years of life with better hearing than earlier generations.”

Individuals who worked for more than five years in loud occupational settings or who fired more than 1,000 firearm rounds in their lifetime were at a significantly higher risk for hearing loss.

“Despite the benefits from the apparent delayed start of hearing loss, there will be an increased need for affordable hearing health care as the numbers of adults aged 70 and older continue to grow,” institute director Dr. James Battey said.

The findings come with some surprise giving public health warnings over the past decade that teens were increasingly listening to loud music over headphones. The study considered only those individuals over the age of 20, so it may still be too early to gauge the full impact on the Walkman and iPod generations. Previous research has shown that as many as 1 in 5 teens experience hearing loss, and 9 out of 10 listen to music at volumes that can damage hearing.

The authors called for eliminating barriers to getting hearing aids, echoing the findings of a report issued in June by the National Academies of Sciences, Engineering and Medicine. That report found that less than a third of adults 50 years and older who might benefit from a hearing aid use them.

The authors attributed the shortfall to high cost, lack of insurance coverage, the stigma associated with wearing a hearing aid and limited awareness of the options.

“Hearing loss has been relegated to the sidelines of healthcare,” said Dr. Dan Blazer, a professor of psychiatry emeritus at Duke University Medical Center and chair of the committee that wrote the report. “For many people with hearing loss, trying to navigate the health care system to address their issues can be confusing and frustrating and they can be left with no clear guidance on what will best fit their financial, health, social and hearing needs.”

The committee found that the average cost of a hearing aid, including the professional services involved, ran about $4,700, and that few individuals have any insurance coverage for hearing needs. The vast majority of employers do not provide any hearing health care insurance, and Medicare covers only diagnostic hearing tests, although some Medicare-managed care plans offer such benefits.

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