Hearing-impaired adults are more likely to be depressed than those with excellent hearing - and than those who are fully deaf -according to a large U.S. survey.
Higher rates of depression were most common among women and among the middle aged, compared to people over 70, researchers found.
A few smaller studies have shown a connection between hearing loss and depression, but they were not based on nation-wide samples and the results were conflicting, Dr. Chuan-Ming Li said.
Li worked on the new study at the National Institute on Deafness and Other Communication Disorders at the National Institutes of Health in Bethesda, Maryland.
The researchers analyzed data from the 2005-2010 National Health and Nutrition Examination Surveys. More than 18,000 adults over age 18 answered questions about their mental and physical health, and those over 70 years old were also examined for hearing loss by a doctor.
To assess hearing in all participants, one item on the questionnaire asked: "Is your hearing excellent, good, do you have trouble hearing, or are you deaf?" For this study, those who reported having "some" or "a lot" of trouble hearing were counted as "hearing impaired" (HI).
Almost 80 percent of the people surveyed reported having good or excellent hearing.
The participants also answered nine questions about depression symptoms.
More than 11 percent of people with some hearing problems scored as having moderate to severe depression, compared to six percent of people with good or excellent hearing.
Among those with hearing problems, nine percent of men had moderate to severe depression compared to almost 15 percent of women, according to the results published in JAMA Otolaryngology-Head and Neck Surgery.
Women were more likely to report depression than men, but less likely to report hearing problems.
Low education level, living alone, smoking and binge drinking were all associated with both hearing problems and depression.
In general, as hearing impairment got worse, risk for depression increased, except for people who were totally deaf - they were about half as likely to be depressed as people with excellent hearing.
"One reason for this result may be that people with severe to profound HI have had a different experience in their exposure and access to hearing health care," Li told Reuters Health. They are more likely to have been "discovered" and offered treatments like hearing aids or cochlear implants.
"Thus, their lower prevalence of depression may be because a higher proportion of them have had access to hearing health care services and thereby have obtained more help and earlier interventions than those with mild to moderate HI," Li said.
Although hearing impairment is more common in older people, for those over 70 there was no association between self-reported hearing trouble and depression. But this group also received a physical exam for hearing loss, and according to that exam there was an association between moderate hearing loss and depression among older women.
Researchers can't yet say why women might have stronger links between hearing impairment and depression, Li said. Women do tend to suffer more depression than men, also for unknown reasons.
"On average, men begin to lose their hearing in high frequencies, 3 to 6 kiloHertz, during middle age, probably due to a variety of factors, but especially due to noise-induced hearing loss," he said. "Women, on average, have fairly well-preserved hearing in the higher frequencies, which are critical for understanding speech in noisy environments, until after reaching age 65 or 70 when they begin to experience a steady decline."
Anyone with signs of depression should see a physician, he said. For those with hearing loss, the Hearing Loss Association of America website is a good resource.
"We should encourage people to find out about hearing loss and how people successfully cope with it," Li said. "It can be very helpful - and empowering - for an individual to know that others are in the same situation and are finding ways to cope."
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