Hearing loss in middle age was found to be associated with higher odds of cognitive decline and dementia later in life, according to a large study conducted in Taiwan published in JAMA Network Open on July 31st.
Using data from more than 16,000 men and women, researchers found that a new diagnosis of hearing loss between ages 45 and 65 more than doubled the odds of a dementia diagnosis in the next dozen years.
According to the study authors, even mild levels of hearing loss could be a risk factor, so hearing protection, screening and hearing aids could all play an important role in reducing cognitive risk.
Hearing Loss: a Reversible Risk Factor for Dementia and Alzheimer’s Disease?
Past research suggests that about two thirds of the risk for dementia is hereditary or genetic, which means about one third of the risk is from things that are modifiable, noted lead study author Charles Tzu-Chi Lee of the National Taiwan Normal University in Taipei.
Among modifiable risk factors, hearing loss accounts for about 9% of dementia risk, a greater proportion than factors like hypertension, obesity, depression, diabetes and smoking.
“Hearing loss is a potential reversible risk factor for dementia, including Alzheimer’s disease. The early identification of hearing loss … and successful hearing rehabilitation can mitigate the negative effects of hearing loss. However, the ideal time to perform hearing loss screening to reduce the risk of dementia remains unclear.”
–Charles Tzu-Chi Lee, Lead Study Author, in Comments to Reuters
Lee and colleague Chin-Mei Liu of the Taiwan Centers for Disease Control analyzed data on people aged 45 and older from the National Health Insurance Research Database of Taiwan. They matched 8,135 patients newly diagnosed with hearing loss between 2000 and 2011 to 8,135 similar individuals without hearing loss and followed them all through 2013.
All were free of dementia at the start, but over time, 1,868 people developed dementia – and 59% of them came from the hearing loss group.
Among people with hearing loss, new dementia cases were identified at a rate of 19 per 10,000 people, compared with 14 per 10,000 without hearing loss.
Overall, hearing loss was associated with a 17% risk increase for dementia, the researchers calculated. But when they looked at subsets of people, almost all the increased risk was concentrated in the youngest age group. Among those 45-65, dementia risk was 2.21-fold higher with hearing loss.
According to Lee, the results of their study suggests that screening for hearing loss should be performed when people are middle aged.
Connection Between Hearing Loss and Dementia
The results of the study factored in variables such as sex, age and insurance type, as well as other known risks for cognitive decline and dementia. Among these, six other conditions were associated with an increased risk of dementia: cerebrovascular disease, diabetes, anxiety, depression, alcohol-related illnesses and head injury.
The study was not designed to determine how hearing loss might contribute to dementia, or if the two conditions share the same cause. One limitation of insurance data, the researchers note, is lack of precision in the dementia diagnoses.
“In an aging population, dementia will present one of the greatest challenges to society in this century. There are now more people over the age of 65 than under the age of 5 for the first time in human history. Pharmacological treatments for the most common cause of dementia, Alzheimer’s disease, only offer symptom-modifying effects. This has led to suggestions that a change in approach to prevention rather than treatment after diagnosis may be more beneficial.”
–David Loughrey of the Trinity College Institute of Neuroscience, in Comments to Reuters
Future studies will investigate whether treating hearing loss can decrease the risk of dementia, the study team writes.
“Hearing health is critically important to the human experience,” said Dr. Richard Gurgel of the University of Utah in Salt Lake City, who wasn’t involved in the study. “There is more to hearing loss than just hearing. Hearing loss affects the way we fundamentally communicate and connect with one another. Hearing loss impacts the overall health of older adults, including their emotional well-being and social isolation, as well as cognition.”
Reference:
Liu C, Lee CT. Association of Hearing Loss With Dementia. JAMA Netw Open. Published online July 31, 20192(7):e198112. doi:10.1001/jamanetworkopen.2019.8112
Source: Reuters, JAMA Network Open
