Among older adults, hearing loss and dementia are both highly prevalent and are thought to be linked. In a huge new study, a team of international researchers has tried to determine how the two are linked.
It’s predicted that, by 2050, dementia will affect 150 million people worldwide. Hearing loss equal to or above 20 dB affects 10% of people aged 40 to 69, 30% of those over 65, and 70% to 90% of people aged 85 or older. For context, whispering heard from 5 ft (1.5 m) away produces a sound of 20 dB.
Studies have demonstrated a link between the two conditions, suggesting hearing loss is a modifiable risk factor for dementia. The 2020 Lancet Commission report on dementia prevention found that hearing loss might be linked to around 8% of worldwide dementia cases. As such, addressing hearing issues in older people, such as through the use of hearing aids, might be a way of reducing dementia risk.
A few studies have investigated the relationship between hearing aid use and dementia, but their findings have been inconsistent. A new study by a team of international researchers has examined the link between hearing aid use and dementia among middle-aged and older adults.
“The evidence is building that hearing loss might be the most impactful modifiable risk factor for dementia in midlife, but the effectiveness of hearing aid use on reducing the risk of dementia has remained unclear,” said Dongshan Zhu, corresponding author of the study. “Our study provides the best evidence to date to suggest that hearing aids could be a minimally invasive, cost-effective treatment to mitigate the potential impact of hearing loss on dementia.”
The researchers used the UK Biobank to look at data from 437,704 people aged between 40 and 69 who had self-reported hearing aid use and risk of dementia of all causes and cause-specific dementia, that is, dementia caused by Alzheimer’s disease, vascular dementia, and non-Alzheimer’s disease non-vascular dementia.
Around three-quarters of participants had no hearing loss. The remaining one-quarter had some hearing loss, and 11.7% of those used hearing aids.
The researchers found that compared to participants with normal hearing, those with hearing loss who didn’t use hearing aids had an increased risk of all-cause dementia. They did not find an increased risk among people with hearing loss who used hearing aids.
This means that people with hearing loss who are not using hearing aids have approximately a 1.7% risk of dementia compared to those with normal hearing or those using hearing aids, whose risk is 1.2%.
“Close to four-fifths of people experiencing hearing loss do not use hearing aids in the UK,” Zhu said. “Hearing loss may begin early in one’s 40s, and there is evidence that gradual cognitive decline before a dementia diagnosis can last 20 to 25 years. Our findings highlight the urgent need for the early introduction of hearing aids when someone starts to experience hearing impairment.”
The study also examined how other factors, such as loneliness, social isolation and depression, might impact the relationship between hearing loss and dementia. The data suggests that less than 8% of the association between the two could be removed by addressing psychosocial problems. This, the researchers say, indicates that decreasing dementia risk comes mostly from hearing aid use rather than indirect causes.
The researchers note the limitations of their study, namely that self-reporting runs the risk of introducing bias, and that the association between hearing loss and dementia might be due to neurodegeneration. Further, the generalizability of the study may be limited given that US Biobank participants are white and few were born deaf.
Nonetheless, they say their findings highlight the need for a society-wide push to raise awareness about hearing loss and its potential links to dementia, in addition to increasing accessibility to hearing aids.
More research is needed to uncover the causal link between hearing loss and dementia.
“The underlying pathways which may link hearing aid use and reduced dementia risk are unclear,” said Fan Jiang, lead author of the study. “Further research is needed to establish a causal relationship and the presence of underlying pathways.”
The study was published in the journal The Lancet Public Health.
Source: University of Melbourne/University of Sydney/Shandong University via Scimex
