Although the brain naturally becomes smaller with age, the shrinkage is accelerated in older adults with hearing loss, according to a study by researchers from Johns Hopkins and the National Institute on Aging. The findings add to a growing list of adverse 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 and women.

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 participant also had a complete physical at the time of the first MRI in 1994, including a hearing test. At the starting point, 75 participants had normal hearing, and 51 participants had impaired hearing, with at least a 25-decibel loss.

After analyzing the participants’ MRIs over the following years, Lin and his colleagues
reported in Neuroimage that those participants whose hearing was already impaired .
at the start of the study had accelerated rates of brain atrophy compared to those with normal hearing. The scientists reported more than an additional cubic centimeter of brain tissue loss each year in those with hearing loss, compared to 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.

The structures responsible for sound and speech being affected in those with hearing loss wasn’t a surprise, says Lin, noting that 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 do not work in isolation, and their responsibilities do not 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 Alzheimer’s disease.

Comprehensive Mobile Care’s team stresses the importance of preventative care. “Hearing loss is the third most common health problem in America,” states Dr. Enoch Cox, who provides hearing care to residents in long term care facilities. “Untreated hearing loss will increase the risk of dementia, anxiety, and depression by up to 5x. The great news is that using proper amplification can help to mitigate the risks associated with hearing loss.”
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 research.