AHA News: Hearing Loss and the Connection to Alzheimer’s
A growing number of studies are finding a connection between hearing loss and dementia, but researchers have yet to determine the causal link between the two conditions.
While studies stop short of saying hearing loss causes dementia or dementia to cause hearing loss, researchers theorize that long-term hearing loss somehow affects the brain’s ability to function. Dementia, as well, can lead to impairment of brain functions.
An estimated 5.8 million people in the United States are living with Alzheimer’s disease and other dementias. By 2050, the number is expected to climb to 14 million. Dementia has a number of causes, but the most common cause of the condition is Alzheimer’s, a progressive disease that destroys memory, thinking, and other cognitive skills.
Meanwhile, about 1 in 3 people between the ages of 65 and 74 have hearing loss, while nearly half of people over 75 have difficulty hearing, according to the National Institution on Deafness and Other Communication Disorders (NIDCD). Changes in the inner ear, medications, and certain medical conditions can contribute to age-related hearing loss.
Research reveals the more severe the hearing loss, the higher the risk of developing dementia. For instance, a 2011 study conducted by researchers at Johns Hopkins University in Baltimore is often cited to confirm the hearing loss-dementia connection.
The research team found the risk of dementia was nearly double for older adults with mild hearing loss and triple for people with moderate hearing loss. Adults with severe hearing loss had five times the risk of developing dementia. The study was published in the Archives of Neurology journal, now titled, JAMA Neurology.
Theories Behind the Hearing Loss-Dementia Connection
Researchers involved in numerous studies over the years have developed several theories to explain the connection between cognitive decline and dementia:
- Change in brain structure. Hearing loss could change the part of the brain that receives and processes sound. The change could eventually affect memory, reasoning, and other cognitive skills.
- Brain overload. People with hearing loss have to work harder to understand what others are saying, especially in noisy settings, and this can place stress on the brain. Stress can drain the mental resources used for memory and other brain functions. This depletion of mental resources can lead to a decline in cognitive skills and the potential development of dementia.
- Social isolation. A survey conducted by the National Council of Aging found that adults with untreated hearing loss were more likely to be depressed, have anxiety, and withdraw from social activities. Social isolation has been recognized as a risk factor for cognitive decline and dementia.
Over the next three years, Johns Hopkins University’s researchers will continue a clinical trial that began in January 2018. The study is following 850 participants, between the ages of 70 to 84 years old, who have mild to moderate hearing loss but do not have dementia.
Study participants have been randomly selected to receive treatment for hearing loss while others will participate in a healthy aging education program. Researchers hope the five-year clinical trial determines whether treatment for hearing loss can reduce cognitive decline and the risk of dementia in older adults.
Hearing Loss Treatment May Reduce Dementia Risk
A commission of experts conducted an extensive review of studies regarding hearing loss and dementia. The Lancet Commission on Dementia Prevention, Intervention, and Care reported in 2017 that hearing loss was one of nine modifiable health and lifestyle factors that increase the risk of dementia.
The commission suggests that exercise, getting treatment for hearing loss, and managing depression, diabetes, hypertension, and other health conditions contribute to the prevention or delay of dementia.
People with hearing loss, however, must recognize and accept that they have difficulty hearing, according to a study exploring why people delay getting treatment for hearing loss.
This may not be easy to do because of the stigma attached to hearing loss. The study’s authors say that support and education from a treatment program may help people overcome the stigma and improve their quality of life.