Every 10 decibels of hearing loss, the risk of developing Alzheimer’s Disease went up by 20%

Recent research has found a relationship between hearing loss and the onset of memory loss in Alzheimer’s Disease.

In a September online report in the journal Psychology and Aging, Canadian researchers compared the hearing ability of 74 musicians aged 19 to 91 and 89 non-musicians aged 18 to 86.

They defined a musician as someone who started musical training by age 16, had the equivalent of six years of formal lessons, and continued practicing until the day of testing. The non-musicians did not play any musical instrument.

They gave both groups four different auditory tests, and found that while musicians did not have any advantage over non-musical peers in being able to detect sounds as they grew steadily more quiet, they were better able to hear speech over background noise, detect short gaps in sound and detect differences in frequencies, and these gaps only widened with age.

For instance, by age 70, the average musician was able to understand speech in a noisy environment as well as an average 50-year-old non-musician.

“Being a musician may contribute to better hearing in old age by delaying some of the age-related changes in auditory processing in the brain,” said Benjamin Zendel, lead investigator for the study at the Baycrest Center for Geriatric Care in Toronto. He noted that the ability to hear a tone is not directly dependent on those brain circuits.

An earlier study, published in May online by PLoS One — a peer-reviewed, open-access resource from the Public Library of Science — also found that musical training can offset some of the memory deficits of aging.

Researchers at Northwestern University found that longtime musicians aged 45 to 65 bested non-musicians in the same age group in tests of auditory memory and the ability to hear speech in noisy environments.

The scientists tested 18 musicians who had started playing an instrument at age 9 or earlier and consistently played throughout their lives against 19 non-musicians.

Nina Kraus, director of the Auditory Neuroscience Lab at Northwestern, said the experience of musicians at extracting meaningful sounds from a complex soundscape, and remembering sequences of sound, builds up hearing skills that seem to help offset declines that might otherwise occur with aging.

“The neural enhancements we see in musically-trained individuals are not just an amplifying or ‘volume knob’ effect,” Kraus said, but rather a result of brain connections that help individuals better process sound.

Finally, there’s the September report in the Archives of Neurology that found older adults with hearing loss appear to be more likely to develop dementia.

The study, part of a long-term project funded by the National Institute on Aging out of Johns Hopkins University, tracked 639 people aged 36 to 90 tested for hearing loss between 1990 and 1994.

Researchers found that by 2008, 58 of them had developed dementia, including 37 diagnosed with Alzheimer’s Disease. And those who were experiencing hearing loss at the start of the study were much more likely to develop dementia.

Specifically, the scientists found that for every 10 decibels of hearing loss, the risk of developing Alzheimer’s Disease went up by 20 percent.

The lead author, Dr. Frank Lin, said it seems logical that the effects of hearing loss could lead to social isolation and mental strain and thus leave an individual more at risk for dementia, but said it’s also possible that hearing loss is a symptom of dementia. He’s trying to find out by studying whether older adults who wear hearing aids obtain any cognitive advantage.

“Unmanaged hearing loss can interrupt the cognitive processing of spoken language, exhaust cognitive reserve and lead to social isolation” no matter what other conditions may exist, said Sergi Kochkin, executive director of the Better Hearing Institute, a nonprofit advocacy group based in Washington.

Other research suggests that people may devote extra mental resources trying to hear and process sound to such an extent that other aspects of functional memory are harmed.