A new survey of mostly middle-aged adults reveals that among people aged 45 to 54, one in nine shows signs of hearing impairment.

The researchers tested hearing in more than 2,800 adults between the ages of 21 to 84. Over that large range, one in seven had lost some degree of hearing, and as expected, the rate of hearing loss increased with age.

Almost all of those older than 80 - about 90 percent - had lost some hearing, but the rate had already reached one in nine among adults 45 to 54 years old, the largest age group in the population.

Hearing loss “is a significant problem, even in middle age,” said Dr. Peter Rabinowitz of Yale University, who was not involved in the study.

The authors, led by Scott Nash of the University of Wisconsin, determined someone was hearing impaired if at least one ear had trouble hearing various sounds within the range of human speech.

The cutoff, Nash explained, is considered “mild impairment.” So much so, that people may not even realize they have trouble hearing, said Rabinowitz, since the changes can occur relatively slowly. “Not everyone is aware of it.”

The authors found signs that hearing loss might be linked to risks for heart disease and stroke. Specifically, they saw hearing loss was correlated with the health of the blood vessels of the retina in the eye, an indication of blood vessel health overall.

Other studies have also linked ear health to heart disease and stroke risk, Rabinowitz said in an interview. These findings “provide additional evidence” that such risk “may be associated with hearing.”

The association makes sense, he noted - the inner ear depends on a rich supply of blood, and research shows that when blood circulation is compromised, the ear can suffer.

However, the authors did not see an association between hearing impairment and other measures of heart disease and stroke risk in middle-aged adults, such as high blood pressure, diabetes, and obesity.

“This may have been due to the younger age of the cohort, or the low prevalence of some of these conditions in this population,” Nash suggested. “As this population ages, however, it will be very informative to see what effect, if any, these diseases have on future hearing.”

At least 29 million Americans currently live with hearing impairment, most commonly men, older adults, and those exposed to loud noises, according to the Archives of Otolaryngology-Head & Neck Surgery report.

To take a closer look at hearing loss in various age groups, Nash and his team surveyed 2,837 adults.

Indeed, the rate of hearing impairment increased with age, exceeding 40 percent in those 65 and older. But it also affected 6 percent of those between the ages of 35 and 44, nearly 11 percent of adults 45 to 54, and more than 25 percent of adults 55 to 64.

These rates are high, but “unfortunately not all that surprising,” Nash told Reuters Health in an e-mail, since previous studies have also found similar numbers.