A new Brazilian study reveals a hidden connection between hearing loss and cognitive decline, pointing to a surprisingly preventable path to combating dementia.
A study tracking 805 Brazilians in their 50s over an eight-year period has concluded that greater focus on hearing health may play a crucial role in preventing dementia.
A major study from Brazil has found that people in their 50s with hearing loss face a greater risk of cognitive decline. The findings, published in the Journal of Alzheimer's Disease , highlight how protecting your hearing could also help protect your brain. Researchers say this connection deserves more attention, especially when it comes to preventing 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 part of the Longitudinal Study of Adult Health (ELSA-Brazil), an ongoing national project that has tracked the health of 15,000 public servants from six universities and research centers since 2008. The study is supported by Brazil's Ministry of Health and the National Council for Scientific and Technological Development, under the Ministry of Science, Technology, and Innovation. Funding for the hearing and cognitive assessments was also provided 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.
The Evidence from ELSA-Brazil
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.
Reference: “Hearing loss and cognitive decline in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) during eight years of follow-up” by Alessandra Giannella Samelli, Natalia Gomes Gonçalves, Fernanda Yasmin Odila Maestri Miguel Padilha, Vitor Martins Guesser, Carla Gentile Matas, Camila Maia Rabelo, Renata Rodrigues Moreira, Itamar S Santos, Paulo Andrade Lotufo, Isabela J Bensenõr, Paola Gilsanz and Claudia Kimie Suemoto, 1 March 2025, Journal of Alzheimer's Disease
DOI: 10.1177/13872877251315043
The research was funded by the São Paulo Research Foundation.