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People experiencing hearing loss who are not using a hearing aid may have a higher risk of dementia than those without hearing loss, suggests a new study published in The Lancet Public Health journal.

However, using a hearing aid may reduce this risk to the same level as that of people without hearing loss.

Dementia and hearing loss are common conditions among older adults. Studies have shown that hearing loss may be linked to around 8 per cent of worldwide dementia cases, therefore, addressing hearing impairment could be a crucial way to reduce the global burden of dementia.

"The evidence is building that hearing loss may be the most impactful modifiable risk factor for dementia in midlife, but the effectiveness of hearing aid use on reducing the risk of dementia in the real world has remained unclear. 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," said Prof Dongshan Zhu from the Shandong University in China.

The researchers looked at data from 437,704 people, with an average age of 56 years. Around three-quarters of the participants (325,882/437,704) had no hearing loss, and the remaining one-quarter (111,822) had some level of hearing loss. Among those with hearing loss, 11.7 per cent (13,092 / 111,822) used hearing aids.

The study suggests that compared to participants with normal hearing, people with hearing loss not using hearing aids had a 42 per cent higher risk of all-cause dementia, while no increased risk was found in people with hearing loss who used hearing aids.

This is approximately equivalent to a 1.7 per cent risk of dementia in people with hearing loss who are not using hearing aids, compared to 1.2 per cent among those without hearing loss or who are experiencing hearing loss but using hearing aids.

"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," Zhu said.

The researchers also analysed how other factors, including loneliness, social isolation and depressive symptoms might impact the association between hearing loss and dementia.

The study analysis suggests that less than 8 per cent of the association between hearing aid use and decreased dementia risk could be removed by improving psychosocial problems.

The researchers said this indicates the association between hearing aid use and protection from increased dementia is likely mostly due to direct effects from hearing aids rather than the investigated indirect causes.

"A group effort from across society is necessary, including raising awareness of hearing loss and the potential links with dementia, increasing accessibility to hearing aids by reducing cost, and more support for primary care workers to screen for hearing impairment, raise awareness, and deliver treatment such as fitting hearing aids," Zhu said.

The team also acknowledged some limitations to the study, including that self-reporting is at risk of bias, and that as this study is observational, the association between hearing loss and dementia might be due to reverse causation through neurodegeneration or other shared mechanisms.