How hearing loss can impact dementia risk

According to the World Health Organization, almost 2.5 billion people are estimated to have some form of hearing loss, and at least 700 million people will need help with their hearing by 2050. Although hearing loss is common worldwide, it is often left untreated, particularly in lower- and middle-income countries.

Age-related hearing loss is significantly associated with dementia risk, with a 2020 report finding that it nearly doubled the risk for the condition. Overall, hearing loss was associated with over 8% of all dementia cases, or 800,000 of the almost 10 million new cases diagnosed each year.

Currently, it's not clear hearing loss may increase dementia risks, but researchers have identified three potential mechanisms:

1. People with hearing loss have to put in more effort to understand what others are saying, which means there are fewer cognitive resources to help them process the meaning of what they heard.

2. Hearing loss may cause the temporal lobe to shrink more quickly since it's not receiving as much auditory input. Because the temporal lobe is connected to other areas of the part, "that could have cascading influences on brain structure and function," said Justin Golub, an associate professor of otolaryngology at Columbia University Irving Medical Center.

3. People with hearing loss may be less likely to go out and be social, which means that they have less cognitive stimulation overall.

"We've long known that … staying really engaged in commonly social activities is very important for maintaining our cognitive health as well," said Frank Lin, professor at Johns Hopkins University School of Medicine and the Bloomberg School of Public Health

Can hearing aids protect against dementia?

Although hearing loss has been established as a risk factor for dementia, there has been little research on whether using hearing aids as an intervention could reduce this risk.

In a new study published in The Lancet, researchers analyzed data from almost 1,000 older adults, ages 70 to 84, at four community sites across the United States. The participants had untreated hearing loss but did not have substantial cognitive impairment. Some participants were also part of the ongoing Atherosclerosis Risk in Communities (ARIC) study while others were healthy volunteers.

Researchers randomly assigned the participants into two groups. The hearing intervention group received audiological counseling and hearing aids while the control group received health education on chronic disease prevention. The participants had a follow-up every six months for three years and were scored on a "comprehensive neurocognitive" test at the end.

When the researchers analyzed the combined group, hearing aids did not significantly slow cognitive decline. However, when analyzing the ARIC group, which had a higher risk of dementia, alone, researchers found that the hearing intervention was able to reduce cognitive decline by 48%.

"These findings suggest that a hearing intervention might reduce cognitive change over 3 years in populations of older adults at increased risk for cognitive decline but not in populations at decreased risk for cognitive decline," the researchers wrote.

So far, it's still unknown whether hearing treatments can reduce the risk of dementia in the long term. "That's the next big question — and something we can't answer yet," said Lin, who was the co-principal investigator of the study. Currently, Lin and his colleagues are planning a follow-up study to examine the long-term effects of hearing interventions.

Commentary

According to Golub, although there have been smaller trials on hearing aids and cognition, this is the first large-scale study that examined the long-term cognitive effects of wearing a hearing aid. "This is truly unique, truly groundbreaking," he said.

Similarly, Ira Chang, medical director of neurocritical care at Swedish Medical Center, said the study's findings offer patients at high risk of dementia a potential way to slow their cognitive decline. "I think this is a very exciting, very concrete intervention that we can use," she said.

To protect yourself from potential cognitive decline from hearing loss, health experts recommend getting your hearing checked if you haven't already and using a hearing aid even if your hearing loss is mild.

"It is a simple, effective and practically risk-free method to preserve your cognition as much as possible," said Benjamin Tan, Dean's Fellow at the Yong Loo Lin School of Medicine at the National University of Singapore.

For people who cannot easily access an ear, nose, and throat doctor or an audiologist for consultations and treatment, Tan said that lower cost over-the-counter hearing aids could be a good option.

"Even though you will not have experts diagnosing the cause of your hearing loss or fine-tuning your device, it is probably still better to use a hearing aid than none at all," Tan said.

In general, health experts say that early intervention when it comes to physical health is important to preventing cognitive decline and dementia. Some ways people can protect their health include visiting a primary care provider regularly, getting regular physical activity, eating a healthy diet, getting good sleep, and learning new things.

"Intervening earlier to either prevent the disease process altogether or to help build resilience in the face of a disease process is ideal," said Thomas Holland, a physician scientist at the Rush Institute for Healthy Aging. (Holcombe, CNN, 7/18; Posey/Bink, The Hill, 7/22; Bever, Washington Post, 7/19)

As occurrence of neurodegenerative disease in the U.S. has increased, advances in medicine have expanded the outlook for diagnosing, treating, and curing these diseases. We’ve identified four key drivers that are changing the treatment prospect and delivery of care for patients with neurodegenerative diseases.  Download the report with strategic insights on the drivers below.