Summary: A Brazilian study of over 800 adults in their 50s shows that hearing loss is strongly linked to accelerated cognitive decline. Participants with hearing loss experienced faster reductions in memory, language, and executive function over eight years.
Researchers identified two key mechanisms: reduced brain stimulation from hearing loss and increased social isolation, both known risk factors for dementia. These findings emphasize the need for early detection and intervention to protect hearing and potentially reduce dementia risk, especially in low- and middle-income countries where dementia rates are expected to surge.
Key Facts:
- Faster Decline: Adults with hearing loss showed significantly faster cognitive decline over eight years.
- Dual Mechanisms: Reduced brain stimulation and social isolation contribute to dementia risk.
- Prevention Potential: Early hearing tests and interventions like hearing aids could help prevent cognitive deterioration.
Source: FAPESP
A study conducted in Brazil on 805 people in their 50s confirmed that those with hearing loss had an increased risk of cognitive decline.
The results, published in the Journal of Alzheimer’s Disease, point to the need for greater attention to hearing health as a way to prevent dementia.
“Hearing loss is what we call a modifiable risk factor for dementia, including Alzheimer’s, precisely because it can be detected and corrected. By 2050, more than 70% of people with dementia are expected to live in low- and middle-income countries like Brazil.
“That’s why it’s important to have studies that identify our reality and the factors that can be prevented. In addition to the individual burden, there’s also a collective burden.
“There’s no way that Brazil and other low- and middle-income countries can grow old with dementia,” said Claudia Suemoto, professor at the University of São Paulo’s Medical School (FM-USP) and author of the study.
The research was conducted as part of the Longitudinal Study of Adult Health (ELSA-Brazil), which has been monitoring data from 15,000 public servants from six universities and research centers in the country since 2008.
The initiative is funded by the Ministry of Health and the National Council for Scientific and Technological Development (CNPq), linked to the Ministry of Science, Technology and Innovation (MCTI). The audiological assessment and its comparison with the data on cognition collected by ELSA-Brazil were supported by FAPESP.
Mechanisms
Hearing loss usually begins in middle age and is a recognized risk factor for dementia. According to Suemoto, this occurs through two mechanisms. The first is that hearing is an important input pathway for information to the brain.
“It depends on input pathways to deliver a response, along with the knowledge it’s already acquired. However, when a pathway is interrupted, important areas are no longer stimulated, which can accelerate cognitive decline,” she explains.
The second mechanism is behavioral: hearing loss tends to lead to social isolation.
“Almost everyone knows someone older, be it a friend or relative, who doesn’t hear well. To talk to them, you have to speak louder, repeat sentences and they end up being excluded from conversations.
“In a way, it’s so hard for them to hear that they shut themselves out, lose interest and move away. So there’s also the mechanism of social isolation, which is another recognized risk factor for dementia,” she says.
In the study, the participants underwent audiometry tests, an objective measure of hearing quality, three times over the course of the eight-year study.
Tests of memory, language and executive function were carried out during the same period to measure the association between hearing loss and significant cognitive decline. Of the 805 participants, 62 (7.7%) had hearing loss.
After eight years of follow-up, these individuals had faster overall cognitive decline than expected for their age. In addition, specific cognitive tests showed similar but less precise declines in memory, verbal fluency and executive function.
“This shows that it’s important to do an audiometry test because it usually takes a while for people to become aware of their hearing deficit. They start to hear badly, but they don’t realize it and adapt to the new situation.
“But knowing that there’s a loss, it’s possible to correct it with the use of hearing aids. And you also have to remove the stimulus that’s causing the problem,” she warns.
According to the researcher, the main causes of hearing loss in middle age are work-related.
“There are different types of jobs that involve a lot of noise. These people need to wear protective equipment to reduce hearing loss. There’s also the problem of using headphones at too high a volume. All of this is detrimental, so it’s important to get the problem diagnosed,” she adds.
In addition to hearing loss, says the researcher, there are 11 other potential modifiable risk factors for dementia: low education, hypertension, brain damage, diabetes, obesity, alcoholism, smoking, depression, sedentary lifestyle, air pollution and social isolation.
About this hearing loss and cognition research news
Author: Heloisa Reinert
Source: FAPESP
Contact: Heloisa Reinert – FAPESP
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Hearing loss and cognitive decline in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) during eight years of follow-up” by Claudia Suemoto et al. Journal of Alzheimer’s Disease
Abstract
Hearing loss and cognitive decline in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) during eight years of follow-up
Background
Hearing loss (HL) of moderate or higher grades is common in older adults with increasing prevalence as people age, rising from 12% at the age of 60 years to over 58% at 90 years. HL in midlife is one of the main potentially modifiable risk factors for dementia.
It is estimated that 7% of dementia cases globally could be avoided if this risk factor was eliminated. However, much of the research conducted has been in high-income countries even though low- and middle-income countries have the highest prevalence of dementia.
Objective
To study the association between HL and cognitive decline during eight years of follow-up in a Brazilian sample.
Methods
Participants from the São Paulo center of the Brazilian Longitudinal Study of Adult Health were evaluated in three study waves (2008–10, 2012–14, and 2017–19). HL was defined as pure-tone audiometry above 25 dB in the better ear.
Cognitive performance was evaluated with six tests related to memory, verbal fluency, and trail-making tests. A global cognitive z-score was derived from these tests. The association between HL and cognitive decline was evaluated with linear mixed-effects models adjusted for sociodemographic, lifestyle, and clinical factors.
Results
Of 805 participants (mean age 51 ± 9 years, 52% women, 60% White), 62 had HL. During follow-up, HL was associated with faster global cognitive decline (β = −0.012, 95% CI = −0.023; 0.000, p = 0.039).
Conclusions
HL was significantly associated with a faster rate of global cognitive decline after a median follow-up of eight years in a sample of middle-income country.
