An international team of scientists has found that people with mild cognitive impairment who use hearing aids have a significantly lower risk of developing dementia and experience a slower cognitive decline.
The new paper, published in the journal Alzheimer's & Dementia: Translational Research & Clinical Interventions, is the first to investigate the link between hearing aids and progression to dementia in individuals with mild cognitive impairment (MCI).
The research team was led by Dr Magda Bucholc of Ulster University and used data from the National Alzheimer’s Coordinating Center (NACC). The researchers analysed a sample of more than 2,000 people over the age of 50 with hearing impairments, whose cognitive status ranged from MCI to dementia.
MCI involves decline in cognitive abilities greater than normal age-related changes but not severe enough to meet diagnostic criteria for dementia. Many individuals with MCI do not progress to dementia and may even regain normal cognitive ability.
Dr Sarah Bauermeister of Dementias Platform UK, who co-authored this new study, said: ‘Our results clearly suggest that the use of hearing aids is independently associated with a decreased risk of a dementia diagnosis for MCI patients.’
Dr Bucholc said: ‘We measured the time for progression from MCI to dementia in individuals using hearing aids and those with uncorrected hearing impairment, and found that use of hearing aids was associated with a two-year slower conversion to dementia. The percentage of participants who had not developed dementia five years after the baseline MCI diagnosis was 19% for non-users of hearing aids and 33% for those using hearing aids.
‘Some may say this constitutes a modest finding overall: however, in my opinion, given there is no disease-modifying treatment for dementia, even a small beneficial effect of hearing loss treatment in delaying the disease can have significant implications for public health. In fact, studies show that delaying the onset of dementia by even two years would have substantial economic and societal effects.’
The study also looked at how participants’ scores in a standard cognitive test for dementia changed over time. Researchers found that the mean annual rate of decline in cognitive scores for non-hearing aid users with MCI was nearly 30% higher than the average rate of change for hearing aid users.
Dr Bauermeister added: ‘Gender, socioeconomic factors and cultural influences all play a role in the use of hearing aids. For example, we found that men had a much higher rate of hearing aid use than women.’
In addition, people with MCI who used hearing aids were found to be older than their counterparts who didn’t use hearing aids – although the difference was only two years on average.
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 said: ‘This is an important first step in triggering policy changes to encourage people with hearing loss who are at risk of dementia to wear hearing aids. However, what is still unclear is what effect the hearing loss has on the structure and function of the brain over the long term. This needs to be further tested in clinical trials.’
Dr Ralph Holme, Executive Director of Research at the national hearing loss charity RNID, said: ‘It is well established that hearing loss is associated with an increased risk of dementia, and this new research supports the growing view that the use of hearing aids may help slow its onset. Further research is needed to definitively show this, but clearly taking early action to address your hearing loss can only be a good thing. RNID is helping to fund vital research to understand why hearing loss and dementia are linked.’
Francesca Oliver, Audiology Specialist at RNID, said: ‘This important research adds to the growing body of evidence on the link between hearing loss and dementia. There is strong evidence that already shows hearing aids improve people’s wellbeing and are clinically effective, and this research further highlights their potential additional benefits. However, many people still delay seeking help for their hearing loss. This research could strengthen the case for introducing hearing screening within the NHS Health Check, which RNID has called for. Furthermore, this research emphasises the need to ensure hearing aids are available to all who need them, as access to NHS hearing aids is restricted in some parts of England.’