Treating hearing loss via hearing aids could reduce dementia risk

• The lack of effective treatments for dementia highlights the importance of identifying modifiable risk factors to facilitate the prevention of dementia.
• A new large, observational study shows that hearing loss was associated with an increased risk of dementia, and the use of hearing aids could attenuate this risk.
• The rate of adoption of hearing aids is low among individuals with hearing loss.
• These findings underscore the need for policies that improve the diagnosis of hearing loss and the adoption and accessibility of hearing aids.

Although the symptoms of dementia often appear later in life, the underlying changes in the brain tend to begin in middle age. Similarly, the prevalence of hearing loss also starts to increase after 40 years of age. This has led scientists to think that hearing loss may increase the risk of dementia, with some evidence supporting this association.

A recent large study published in The Lancet Public Health now shows that untreated hearing loss was associated with an increased risk of all-cause and specific types of dementia.

Notably, individuals with hearing loss using hearing aids were at a similar risk of dementia as those without hearing loss, suggesting that remediation of hearing loss could reduce the risk of dementia.

The adoption rate of hearing aids is usually low among those with hearing loss, and these results highlight the importance of public health policies to increase the adoption of hearing aids. These policies could include increasing awareness about the potential adverse effects of untreated hearing loss, emphasizing screening for hearing loss, and improving access to hearing aids by making them more affordable.

Dr. David Loughrey, Atlantic Fellow for Equity in Brain Health at the Global Brain Health Institute, Trinity College Dublin, said:

“This study contributes to a growing body of research that has linked hearing loss to an increased risk of dementia and other adverse health outcomes among older adults. It is important to raise awareness of these findings and that addressing hearing loss may mitigate this risk.”

“Dementia presents a huge cost for the world’s economy, with around half of these costs being borne by people who are providing informal care for dementia patients. Hearing loss may provide a cost-effective approach to help reduce the burden of dementia.”
— Dr. David Loughrey

Hearing loss and dementia

The absence of treatments that cure or stop the development of dementia underscores the need to identify modifiable risk factors to prevent the occurrence of this neurodegenerative condition. Similar to dementia, the prevalence of hearing loss also tends to increase gradually with age.

In addition, some studies have shown an association between hearing loss and an increased risk of dementia. Thus, the use of hearing aids to relieve hearing loss could potentially reduce the risk of dementia.

Indeed, there is some evidence to suggest that the use of hearing aids can delay cognitive decline and reduce dementia risk. By contrast, other studies have shown a lack of association between hearing aid use and dementia risk.

One of the reasons for these inconsistent results has been the small sample size used in the previous studies. Moreover, the association between hearing aid use and specific types of dementia has not been extensively studied.

In the present study, the researchers used a large study sample to examine the association between hearing aid use and the risk of dementia. They also assessed the impact of hearing aid use on the risk of specific types of dementia.

Hearing aid use and dementia risk

The study included data from 437,704 individuals collected by the UK Biobank, a large biomedical database that collects data on genetic, health, and environmental information from the participants. The participants were free of symptoms of dementia at the onset of the study and had an average age of 56 years at baseline.

The researchers obtained data on hearing loss through self-reports at baseline, whereas information on dementia diagnosis was obtained through medical records and death registers. They also collected data on other variables, such as years of education, income levels, medical conditions, social isolation, etc., that could influence the risk of dementia or hearing loss over an average follow-up period of 12.1 years.

The researchers found hearing loss was more common in male participants than in females and those with cardiovascular conditions, obesity, depressed mood, and loneliness. Individuals with hearing loss had a 42% greater likelihood of developing all-cause dementia during the follow-up period than those with unimpaired hearing.

Individuals with hearing loss who used hearing aids were not at an elevated risk of all-cause dementia than those without hearing loss. Similarly, individuals with untreated hearing loss, but not those using hearing aids, were at an increased risk of Alzheimer’s disease, vascular dementia, and the rest of non-Alzheimer’s disease non-vascular dementia.

Not treating hearing loss may heighten risk

These results could suggest that untreated hearing impairment could increase the risk of dementia.

Given the study’s observational design, the association between hearing loss and dementia could also be explained by factors associated with dementia increasing the risk of hearing loss.

Consequently, the researchers reanalyzed data after excluding cases of dementia that emerged either before 5 or 10 years after the onset of the study. Untreated hearing impairment was still associated with dementia in these follow-up analyses, suggesting that hearing loss was more likely a risk factor for dementia.

Several mechanisms could potentially contribute to the increased risk of dementia due to hearing loss. For example, hearing loss may require compensatory allocation of brain resources involved in other cognitive processes.

Alternatively, the lack of auditory input due to hearing loss may cause the degeneration of brain regions involved in processing auditory information and, subsequently, cognitive function.

Hearing loss may also impede communication and lead to loneliness and depression. These mental health factors are also associated with an increased risk of dementia.

In the present study, the analysis suggested that only 11% of the reduction in dementia risk due to the use of hearing aids could be attributed to the amelioration of psychosocial factors, such as loneliness, social isolation, and depression. This suggests that hearing loss may directly increase the risk of dementia by impacting brain regions involved in cognition.

Strengths and limitations

“The analysis, which assessed risks for different forms of dementia, indicated that treating hearing loss may reduce the risk of dementia [by] mitigating the impact of hearing loss on the brain. This may reduce the brain’s vulnerability to the disease processes linked with these dementias. More research is needed to investigate this to further understand the mechanism by which hearing loss is linked with dementia.”
— Dr. David Loughrey

The study’s strengths included the use of a large study sample, long follow-up duration, and the ascertainment of dementia based on medical reports instead of self-reports.

The authors acknowledged that the study had a few limitations. This included the use of self-reported data on hearing loss, which could be inaccurate. Moreover, the data on hearing aid use was only collected at baseline.

As a result, the analysis could not account for individuals who started using hearing aids after the onset of the study.

The analysis also did not account for the duration of hearing aid use, and the duration of hearing aid use could have potentially influenced the risk of dementia.

In addition, it is worth mentioning that most participants were white which may limit a generalization of the results.

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