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Hearing loss is common as we get older. Age is the main risk factor for dementia. The two conditions may occur together, but can deafness cause dementia? It’s harder to tell than you might suppose, since one of the key steps in making a diagnosis of dementia involves cognitive testing, which is mainly done verbally, so a person with impaired hearing may score lower simply on account of not having heard the question. Also, if you have hearing impairment it becomes harder to hear speech against background noise and this can cause people to withdraw from social events in a manner that may resemble the onset of dementia. For illustration, if you have ever had impacted wax in your ear, you will recall how strange this makes the world seem.

Some research studies that have tested the possible causal contribution of hearing loss to dementia, the best known led by Professor Frank Lin from Baltimore. To answer this question, you need quite large samples and you need to follow them up over time, long enough for at least some of the sample to develop dementia. So this is expensive research that takes several years to deliver. Or you can use existing sets of data if they have included relevant information, such as hearing tests. A study I have been involved with used data from the UK Biobank and we found that there was more decline in several different cognitive tests for people with greater degrees of hearing loss over a 3-year period. It’s worth saying that the people in this sample did not have dementia and were relatively young so these are small changes. And we don’t know if they are early changes that will lead to dementia for these individuals or not.

Meanwhile, back in the real world, we have a large population of people, probably about 300,000 in the UK, who have dementia and significant hearing loss. Many live in care homes, where more studies of hearing loss and improving communication (e.g. through hearing aids) are urgently needed. As well as this, older people with dementia are frequently admitted to acute hospitals with a whole range of medical conditions, and many of these will have hearing impairment too. We know that hospitals are noisy places but nobody seems able to do anything to remedy the situation.

One the research groups I most enjoy working with is a small hearing and dementia group. We have representatives from Nottingham University Hospitals, both Audiology and Health Care of Older People, and the Nottingham Hearing Biomedical Research Unit. We have agreed a small suite of service improvement projects that, taken together, will (we hope) impact on the sound environment of hospitals. First, we propose to measure sound levels in our wards for older people. A previous study suggested that parts of a surgical ward were like being at a busy bus stop, with peak noise levels equivalent to HGVs passing regularly. Second, Audiology has invested in a dedicated member of their staff to take referrals of older people from the wards, e.g. to advise about or fix hearing aids or to provide hearing assessments when needed. We have baseline data from the first 4 months and now we are planning an intervention, e.g. at nursing induction, so that we can audit how this affects future referrals. Third, we will undertake a prevalence study (a census, if you like) of the older people’s wards on a single day, to see what numbers of patients have dementia and/or hearing loss and we will look at how many have and are using hearing aids. The fourth strand is a conversation with our health commissioners about how to ensure effective ways of following on from any good work done in hospitals, for example, fitting new aids. Finally, the outputs from these small studies will inform our research agenda as we think there is scope for a programme of research around improving communication with people who have both cognitive and hearing impairment. We know, for instance, that it is not just a matter of fitting hearing aids. It will instead require a more comprehensive approach to the sound environment and a more positive engagement from nursing and care staff.