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A new study has found that hearing loss increases the risk of a precursor to dementia called mild cognitive impairment – but this increased risk is not present in people who wear hearing aids.

The study – which was co-funded by Dementias Platform UK (DPUK) – investigated the risk of cognitively healthy people developing mild cognitive impairment (MCI). It found that hearing loss increases the risk of MCI, but that hearing aid use significantly reduces this risk.

MCI is a condition involving thinking and memory problems that are worse than the normal decline with age, but not bad enough to disrupt daily life and warrant a diagnosis of dementia. Around 20% of people over 65 have MCI, and while some patients’ functioning remains at this level, 10-15% of those with MCI develop dementia.

Furthermore, roughly a third of people aged 65 and older have some form of hearing impairment. These figures are so high that The Lancet Commission on Dementia Prevention, Intervention, and Care estimated that untreated hearing loss may account for up to 9% of dementia cases.

Shedding light on this issue is a research team led by Dr Magda Bucholc (Lecturer in Data Analytics at Ulster University) and including Dr Sarah Bauermeister (Senior Scientist at DPUK). Their latest study, published in the journal Alzheimer’s & Dementia: Translational Research & Clinical Interventions, a journal of the Alzheimer’s Association, is the first to investigate the link between hearing aids, cognitive decline, and progression to MCI in cognitively healthy individuals.

The current work builds on the team’s previous paper, which found that people with MCI who wore their hearing aids were less likely to develop dementia. The new study aimed to find interventions that can be put in place earlier in the dementia process to prevent the condition.

The team used data on over 4,300 participants from the National Alzheimer’s Coordinating Center (NACC). The participants’ changing cognitive and functional skills were calculated based on their scores in six areas: memory, orientation, judgement and problem solving, community affairs, home and hobbies, and personal care. These scores were analysed alongside any clinical diagnosis of MCI and the participants’ self-reported hearing impairment and hearing aid use.

The team found that people with hearing loss were at significantly higher risk of developing MCI than people with normal hearing. However, people with hearing loss who wore their hearing aids had a significantly reduced risk of MCI.

Dr Bucholc said:

‘Our latest paper demonstrates that hearing aid use is linked to lower rates of cognitive decline and reduced risk of MCI in cognitively healthy adults, with hearing aid users having more than 50% lower risk of MCI compared to those not using hearing aids. Importantly, we found that no significant differences in risk of developing MCI and cognitive decline exist between participants experiencing no hearing loss and those diagnosed with hearing impairment using hearing aids.’

Dr Bauermeister added:

Our findings provide compelling evidence in support of hearing aid use, but we now need clinical trials to objectively measure hearing aid use in the context of dementia to establish a causal link. We also encourage other researchers to incorporate hearing aid usage as a confounding factor when analysing changes in cognitive function.’

It is not yet known with certainty why hearing loss is associated with increased dementia risk. Potential explanations include a reduction in people’s ability to engage socially, resulting in higher rates of depression or loneliness, and/or changes to the brain associated with the impact of sensory deprivation. There is also the possibility that hearing problems require greater use of cognitive resources when individuals are engaged in listening.

Dr Bucholc concluded:

‘Our findings imply that the use of hearing aids may help lessen cognitive decline associated with hearing loss. So, improved audiology screening and better access to quality hearing healthcare form an actionable strategy to reduce the incidence of MCI and help mitigate the impending dementia epidemic.’