Hearing Loss in Seniors Linked to Faster Brain
Shrinkage, Growing List of Associated Ailments
Among other problems for senior associated with
hearing loss are dementia, falls, failing physical and mental health
22, 2014 - Although the brain becomes smaller with age, the shrinkage
seems to be fast-tracked in older adults with hearing loss, according to
the results of a study by researchers from Johns Hopkins and the
National Institute on Aging. The findings add to a growing list of
health consequences associated with hearing loss, including increased
risk of dementia, falls, hospitalizations, and diminished physical and
mental health overall.
For the study, Frank Lin, M.D., Ph.D., and his
colleagues used information from the ongoing Baltimore Longitudinal
Study of Aging to compare brain changes over time between adults with
normal hearing and adults with impaired hearing. The Baltimore
Longitudinal Study of Aging was started in 1958 by the National
Institute on Aging to track various health factors in thousands of men
Previous research from other studies had linked
hearing loss with marked differences in brain structure compared to
those with normal hearing, both in humans and animals. In particular,
structures that process information from sound tended to be smaller in
size in people and animals with impaired hearing. Lin, an assistant
professor at the Johns Hopkins University schools of medicine and public
health, says it was unknown, however, whether these brain structural
differences occurred before or after hearing loss.
As part of the Baltimore Longitudinal Study of
Aging, 126 participants underwent yearly magnetic resonance imaging
(MRI) to track brain changes for up to 10 years. Each also had complete
physicals at the time of the first MRI in 1994, including hearing tests.
At the starting point, 75 had normal hearing, and 51 had impaired
hearing, with at least a 25-decibel loss.
After analyzing their MRIs over the following
years, Lin and his colleagues, reporting in an upcoming issue of
Neuroimage, say those participants whose hearing was already
impaired at the start of the sub-study had accelerated rates of brain
atrophy compared to those with normal hearing.
Overall, the scientists report, those with impaired
hearing lost more than an additional cubic centimeter of brain tissue
each year compared with those with normal hearing. Those with impaired
hearing also had significantly more shrinkage in particular regions,
including the superior, middle and inferior temporal gyri, brain
structures responsible for processing sound and speech.
That structures responsible for sound and speech
are affected in those with hearing loss wasn't a surprise, says Lin —
shrinkage in those areas might simply be a consequence of an
"impoverished" auditory cortex, which could become atrophied from lack
of stimulation. However, he adds, these structures don't work in
isolation, and their responsibilities don't end at sorting out sounds
and language. The middle and inferior temporal gyri, for example, also
play roles in memory and sensory integration and have been shown to be
involved in the early stages of mild cognitive impairment and
"Our results suggest that hearing loss could be
another 'hit' on the brain in many ways," Lin explains.
The study also gives some urgency to treating
hearing loss rather than ignoring it. "If you want to address hearing
loss well," Lin says, "you want to do it sooner rather than later. If
hearing loss is potentially contributing to these differences we're
seeing on MRI, you want to treat it before these brain structural
changes take place."
Lin and his colleagues say they plan to eventually
examine whether treating hearing loss early can reduce the risk of
associated health problems.
The research was supported by the intramural
research program of the National Institute on Aging, the National
Institutes of Health's National Institute on Deafness and other
Communication Disorders (K23DC011279), a Triological Society/American
College of Surgeons Clinical Scientist Development Award and the Eleanor
Schwartz Charitable Foundation.
Susan Resnick, Ph.D., of the National Institute on
Aging was the study's senior investigator. Michael A. Kraut, M.D.,
Ph.D., of Johns Hopkins; and Luigi Ferrucci, M.D., Ph.D., and Yang An,
M.S., both of the National Institute on Aging, also contributed to this
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