There is disturbing news on two fronts regarding aging and hearing loss. Almost two thirds of Americans over the age of 70 have some degree of hearing loss, according to a study in the Journal of Gerontology (February 28, 2011). Among those over 60, hearing loss accounted for over one-third of the risk of developing dementia (other risk factors for dementia include age, cardiovascular risk, and gender, among others), reports a study in the Archives of Neurology (February 2011). Older adults who experience a loss of hearing also have a greater risk of developing Alzheimer’s disease. Both studies were conducted by Frank Lin, MD, PhD, Assistant Professor, Division of Otology, Neurotology and Skull Base Surgery Core, faculty member, Johns Hopkins Center on Aging and Health, Baltimore, and his colleagues. “We are increasingly realizing that hearing loss is incredibly important as we age and that it may in fact be directly tied with our risk of cognitive decline and dementia,” says Dr. Lin.
Findings from the Journal of Gerontology study include:
- Among 717 subjects age 70 and over, 63 percent had mild to severe hearing loss.
- Rates were higher in men than in women
- Rates were higher in older adults than in younger ones
- Rates were higher in white subjects (64%) than in black participants (43 %).
Findings from the Archives of Neurology study include:
- The risk of dementia increased among those with a hearing loss greater than 25 decibels
- The risk increased in those who had moderate to severe loss as opposed to mild hearing loss
- The risk of Alzheimer’s increased by 20 percent for every 10 decibels of hearing loss.
Experts don’t know exactly what to do about the hearing loss/dementia problem. “We don’t know yet if an intervention as simple as a hearing aid could have an effect on delaying cognitive decline,” says Dr. Lin. “However, there’s little to no risk of being more proactive in addressing and seeking treatment for hearing loss.” The authors also suggest that everything possible be done to create social and environmental conditions that make hearing as easy as possible, for example, diminishing background noise that might make hearing a conversation difficult. Although the number of older adults with hearing loss is at an all-time high, only 20 percent of those affected use hearing aids. It’s only three percent among those with mild hearing loss–“Phenomenally low,” observes Dr. Lin. “We’ll need to do more research to figure out what the exact mechanism may be and whether intervention such as hearing aids or cochlear implants could have an effect on delaying cognitive decline,” concludes Dr. Lin.
Previous studies have shown an association between hearing loss and diminished driving ability, walking difficulty, social isolation, cognitive and daily functioning decline, and falls. Hearing loss in Americans over the age of 70 is widely prevalent, largely untreated, and predicts dementia. Treating your hearing loss with the
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A new study from the University of Pennsylvania shows that declines in hearing ability may accelerate gray matter atrophy in auditory areas of the brain and increase the listening effort necessary for older adults to successfully comprehend speech. However, a hearing aid may help decrease the atrophy, as well as help hearing ability.
When a sense (taste, smell, sight, hearing, touch) is altered, the brain reorganizes and adjusts. In the case of poor hearers, the researchers found that the gray matter density of the auditory areas was lower in people with decreased hearing ability, suggesting a link between hearing ability and brain volume.
Lead author Jonathan Peelle, Ph.D, research associate in the Department of Neurology, explained in the press release, “As hearing ability declines with age, interventions such as hearing aids should be considered, not only to improve hearing, but also to preserve the brain.’’ He added, “People hear differently, and those with even moderate hearing loss may have to work harder to understand complex sentences.”
Researchers measured the brain’s response to increasingly complex sentences and then measured cortical brain volume in the auditory cortex. Older adults (60 to 77 years of age) with normal hearing for their age were evaluated to determine whether normal variations in hearing ability impacted the structure or function of the network of areas in the brain that support speech comprehension. The studies found the following:
- People with hearing loss showed less brain activity on functional MRI scans when listening to complex sentences
- Poorer hearers had less gray matter in the auditory cortex
- Areas of the brain related to auditory processing may show accelerated atrophy when hearing ability declines.
In general, research suggests that hearing sensitivity has cascading consequences for the neural process supporting both perception and cognition. Although the research was conducted in older adults, the findings also have implications for younger adults including those concerned about listening to music at loud volumes.
The research appears in the August 31, 2011, edition of The Journal of Neuroscience and was funded by the National Institutes of Health.