Older adults with severe hearing loss are more likely to have dementia, according to a study by researchers at the Johns Hopkins Bloomberg School of Public Health, but instances of dementia were lower among study participants who used hearing aids.
What did we learn?
Previous studies have also observed a link between hearing loss and dementia. A study published in 2012 found that compared to those with normal hearing, those with mild hearing loss had twice the risk of developing dementia, those with moderate hearing loss had three times the risk, and those with severe hearing loss had five times the risk of developing dementia. In fact, hearing loss has been estimated to account for 8% of dementia cases worldwide — more than any other potentially modifiable dementia risk factor, according to the Lancet Commission on dementia prevention, intervention and care.
But researchers for this latest study, the findings of which were published in a research letter in the peer-reviewed journal JAMA on Jan. 10, say past studies were limited because they were “vulnerable to selection bias” — using self-reported data that may not have provided an accurate look at hearing loss and dementia on a national scale.
“This study used an objective, audiometric measure of hearing rather than relying on subjective, self-reported hearing loss. We also used data that has greater representation of older adults in the U.S.,” Alison Huang, lead author of the study and a senior research associate at the Johns Hopkins Cochlear Center for Hearing and Public Health, said in an email to Yahoo News.
The study, funded by the National Institute on Aging, analyzed a national dataset from the National Health and Aging Trends Study, which has been ongoing since 2011.
“The National Health and Aging Trends Study collects data through home visits, which makes it easier for more vulnerable populations, such as adults over 90 years old and older adults with disabilities, to participate compared to a clinic-based study, which only captures people who have the ability and means to get to clinics,” Huang said.
This study’s analysis covered 2,413 individuals, about half of whom were over 80, and “showed a clear association between severity of hearing loss and dementia,” according to a press release from Johns Hopkins. Among participants with “moderate/severe hearing loss,” prevalence of dementia was 61% higher than among participants with normal hearing.
The good news?
The good news is that there may be a potential side benefit to hearing aids. The study found that among 853 participants with moderate to severe hearing loss, “hearing aid use was associated with a 32% lower prevalence of dementia.”
“We’re encouraged by seeing an association between hearing aid use and lower prevalence of dementia, which builds support for public health action to improve hearing care access,” Huang told Yahoo News.
She added that more work is needed from randomized trials to definitively test the effect of hearing aids on cognition and dementia. The ACHIEVE (Aging and Cognitive Health Evaluation in Elders) trial, also funded by the National Institute on Aging, tests the effect of hearing loss treatment on cognition and dementia, and results from that trial will be available later this year, Huang said.
About a third of older adults have hearing loss, with chances of developing hearing loss increasing with age, according to the National Institute on Aging.
Dr. Frank Lin, one of the leaders of the ACHIEVE trial, has offered several possible reasons for the connection between hearing loss and cognitive decline. Hearing loss “can make the brain work harder,” straining to hear at the expense of memory systems; hearing loss may also cause the brain to “shrink more quickly.” Another possible reason is that hearing loss can cause people to become more socially isolated, which harms brain health.
“If you can’t hear very well, you may not go out as much,” Lin said, “so the brain is less engaged and active.”