A new study investigates the relationship between hearing loss and cognitive decline. The scientists have found that after 18 months of hearing aid use, participants’ performance on some cognitive tests improved.
Dementia becomes more likely as we age — so as the population’s average age steadily rises, the prevalence of dementia climbs accordingly.
To date, there is no cure for dementia, and researchers are avidly investigating ways to treat and prevent it.
Because cognitive decline precedes dementia, understanding how to curb this decline could help reduce the risk of dementia.
A group of researchers from the University of Melbourne, in Australia, is particularly interested in the potential role of another condition that becomes more prevalent with age — hearing loss.
According to the authors of the study, published in the Journal of Clinical Medicine, age-related hearing loss affects 30–60% of people aged over 65 and 70–90% of those aged 85 or older.
The authors explain how, “Hearing loss is associated with many comorbidities, including poorer physical health, anxiety, depression, loneliness, and isolation.” Yet, they note, hearing loss is undertreated, with only 1 in 20 working adults aged 50–70 wearing hearing aids.
Importantly, medical researchers now consider hearing loss to be a risk factor for dementia.
It follows that using a hearing aid might reduce the risk of dementia or slow its progress. However, to date, the evidence has been contradictory, with some studies finding benefits and others finding none.
Earlier research had certain limitations. For instance, some studies only had access to relatively small sample sizes or relied on self-reported hearing loss and cognitive decline.
Other studies did not capture information about education level, mood, exercise frequency, and other factors that can also influence cognitive decline.
The latest study involved 99 adult participants aged 62–82 with hearing loss who were new to hearing aids.
The scientists assessed the participants before they had acquired the hearing aids and then 18 months later. The team was also interested in observing any differences between males and females.
The researchers collated information about hearing, speech perception, levels of physical activity, the quality of life, mood, loneliness, and general health.
They also assessed cognitive performance in five domains: psychomotor function, attention, working memory, visual learning, and executive function.
Primarily, the authors were interested in the relationship between hearing loss and cognitive impairment; they also wanted to track whether wearing a hearing aid, over time, might influence cognitive ability.
At the 18-month mark, there was a pronounced improvement in self-reported speech perception in quiet situations. As the authors explain, this has “been widely reported for users of hearing aids.”
When the scientists assessed cognitive performance after 18 months, they found that average scores across the battery of cognitive tests had not improved.
However, when they assessed executive function separately, they found significant improvements. Of the 99 participants, only one male had experienced a decline in executive function.
Executive function refers to a set of cognitive tools that helps us navigate our everyday lives. It includes flexible thinking, working memory, and self-control.
This increase in executive function was more pronounced in females than males.
When the researchers analyzed cognitive data from females only, they found significant improvements in working memory, visual attention, and visual learning, alongside improvements in executive function.
The researchers had also monitored how often the participants used their hearing aids. They found that those who used their devices most regularly experienced greater improvements in cognitive performance.
The authors believe that this difference between sexes might be, at least partially, due to how often the participants used their hearing aids; females used their devices 56.3% of the time, whereas males used them just 33.3% of the time.
The authors are quick to note that their sample is not representative; on average, the participants were more highly educated than the general population. This means that they are likely to have more cognitive reserves and, therefore, might be more resistant to cognitive decline.
Yet even among highly educated people, cognitive performance is not expected to improve in this age group. Overall, the authors conclude:
“Despite the small sample size to date, both the observed relative stability and clinically and statistically significant improvement in cognition seen in this initial participant group after 18 months of hearing aid use are exciting and encouraging.”
When the authors looked at measures of quality of life, they noted a significant improvement over the 18 months.
Again, they found a difference between the sexes, with “a greater proportion of females than males reporting improved quality of life after 18 months of hearing aid use.”
Earlier studies have shown links between hearing loss and mental health issues. In the current study, at the 18-month mark, mental health, on average, was good.
However, the participants in this study had relatively good mental health at baseline. Again, the sample is not representative of society at large, so to fully assess the impact of hearing aids on mental health, scientists will need to carry out more research with larger, more diverse samples of the population.
Although some risk factors for dementia, such as advancing age and genetics, cannot be altered, others can be minimized, and one modifiable risk factor is hearing loss.
Wearing a hearing aid many not prevent dementia. But, as the authors write, “If the onset of functional impairment could even be delayed by only a few years for some people, this would be a significant achievement.”