Hearing Loss May Accelerate Brain Shrinkage: Studies find that untreated hearing loss may lead to or hasten dementia.
Dr. Grimes is quick to say that not everyone who has hearing loss will become demented, but research has shown that there is a relationship.
Brain Shrinkage Accelerates with Hearing Loss
Although the brain naturally becomes smaller with age, the shrinkage seems to be fast-tracked in older adults with hearing loss, according to the results of a study 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, MD, PhD., 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. 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.
The study included 12b participants who underwent yearly magnetic resonance imaging (MRI) to track brain changes for up to 10 years. Each participant also had complete physicals at the time of the first MRI, 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 say 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. 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 Alzheimer's disease.
The authors say the study gives some urgency to treating hearing loss rather than ignoring it. "If you want to address hearing loss well," Dr. 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."
Expending Cognitive Reserve
Constantly struggling to hear is exhausting to the brain and body. "You only have so much bandwidth," explains Dr. Grimes. "If you're talking with someone and not hearing well and your brain is trying to fill in the missing pieces of the sentence, then the next sentence comes in, your brain is not ready and can't catch up because it's still trying to figure out what the last sentence was. There's a lot of cognitive energy that gets used up when filling in those blanks."
The brain can become exhausted through over work just like the body does through extreme exercise--there comes a point when you've spent all the energy you have for a task.
Hearing aids help you reduce the cognitive overload on your brain created by constantly straining to hear. These often discreet, nearly invisible devices can reduce stress and allow you to re-enter conversations and life.
While it's best to see an audiologist to get a customized fit and personalized sound programming, there are many over-the-counter choices on the market. Referred to as personal sound amplification products (PSAPs), these low-cost hearing devices can range from just $10 to $500 or more. They can be helpful to people with mild hearing loss, but pale in comparison to a custom fit. It's like the difference between over-the-counter reading glasses and prescription pair made for your vision needs. The generic readers may be fine for a while, but eventually you will hear better with a custom device.
Whether you choose PSAP or custom hearing aid, know that it takes some time to get used to the devices. "The brain has to be retrained to hear and interpret new sensory input," says Dr. Grimes. That includes getting used to your own voice, conversations, and all the sounds around you, such as the refrigerator, fans, and television sets.
Research into hearing loss, the brain, and quality of life is ongoing. The ACHIEVE study is recruiting 850 people age 70-84 with hearing loss who are cognitively normal. Participants will be randomized to participate in either the hearing intervention (hearing needs assessment, fitting of hearing devices, education/counseling) or the successful aging intervention (sessions with a health educator covering healthy aging topics). Participants will be followed semi-annually for three years.
The Aging and Cognitive Health Evaluation in Elders (ACHIEVE) study is a research study investigating two different treatments that may promote healthy aging and cognitive health in older adults. These treatments include a successful aging education program and a hearing loss program. Study participants will be randomly selected to either receive the successful aging education or the hearing program. At the end of the study, participants can then get the other program if they wish.
The study is sponsored by the Johns Hopkins Bloomberg School of Public Health and will take place at four centers across the United States.
For more information, go the ACHIEVE website www.achievestudy.org.