Hearing loss is a typical health issue that older adults encounter and can be a type of stimulus deprivation that profoundly affects the brain. The loss of this sense takes a toll on regions responsible for processing auditory stimulation, which can atrophy like an underused muscle. But the neurological consequences don’t stop there. According to a recent study, hearing loss hastens age-related shrinkage of the entire brain and increases the risk for dementia and other health issues.

Dr. Frank Lin, assistant professor at Johns Hopkins University, and colleagues conducted magnetic resonance imaging (MRI) on 126 participants (56 to 86 years of age) for up to 10 years to compare brain changes between people who had normal hearing with those who suffered from impaired hearing. The authors report in NeuroImage that participants who were hard of hearing at the beginning of the study showed accelerated rates of brain atrophy. Specifically, the brains of the hearing impaired lost more than an additional cubic centimeter of tissue per year compared with people who could hear just fine.

Unsurprisingly, when the scientists assessed the brains of the hard of hearing, they detected significant brain shrinkage in parts that were responsible for handling sound and speech in the right hemisphere. But Lin pointed out that although these brain regions displayed a "use it or lose it" reaction to being deprived of auditory stimulation, it didn’t mean that the only responsibility of these areas is to decipher sounds and language. Regions, such as the middle and inferior temporal gyri, which process auditory information are also important in memory and play a role in the early stages of mild cognitive impairment that signals Alzheimer’s disease.

“Our results suggest that hearing loss could be another ‘hit’ on the brain in many ways,” Lin explained in a press release, adding that hearing loss should not be treated lightly when considering the neurological consequences that would otherwise ensue. “If you want to [properly] address hearing loss, you want to do it sooner rather than later,” he said. “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.”

This latest finding provides an anatomical basis to the results of a study that Lin published last year, which found that cognitive decline was 41 percent faster in older adults with hearing problems. The next step that Lin and team will take is to measure whether preventing hearing loss lessens the cognitive decline that older adults experience.

Lin’s work is important since almost two-thirds of adults age 70 and older suffer from some form of hearing problem yet many delay seeing a doctor about it due to stigma. Complaints about hearing are reportedly not taken as seriously by the medical estabishment as it should. The problem becomes all the more self-perpetuating when hearing difficulties dissuade elderly sufferers from enjoying an active, social lifestyle that is key in keeping the mind sharp during old age.

 

Source: Lin F R, Ferrucci L, An Y et al. Association of hearing impairment with brain volume change in older adults. NeuroImage. 2014