Difficulty hearing speech could be a risk factor for dementia

Hearing impairment affects around 1.5 billion individuals worldwide (World Health Organization), and there is growing evidence that this could increase the risk of dementia. A major component of hearing impairment is difficulty hearing speech in noisy environments (speech-in-noise hearing impairment). This can have a large impact on the day-to-day functioning of affected individuals who can struggle to follow conversations or hear announcements in noisy environments. However, until now it was unclear whether difficulty hearing speech-in-noise was associated with developing dementia.

This has now been robustly investigated in a new study led by the University of Oxford’s Nuffield Department of Population Health (NDPH) published today in Alzheimer's & Dementia: The Journal of the Alzheimer's Association. The study involved over 82,000 women and men aged 60 years or older from UK Biobank. At the beginning of the study, participants were asked to identify spoken numbers against a background of white noise and based on this test were grouped by the researchers into normal, insufficient and poor speech-in-noise hearing.

Key results:

• Over 11 years of follow-up, 1,285 participants were identified as developing dementia based on hospital inpatient and death register records.
• Insufficient and poor speech-in-noise hearing were associated with a 61% and 91% increased risk of developing dementia, compared to normal speech-in-noise hearing, respectively.

Dr Thomas Littlejohns, senior epidemiologist in the Nuffield Department of Population Health(NDPH), and senior author of the study, said: ‘Dementia affects millions of individuals worldwide, with the number of cases projected to treble in the next few decades. However, there is growing evidence that developing dementia is not inevitable and that the risk could be reduced by treating pre-existing conditions. Whilst preliminary, these results suggest speech-in-noise hearing impairment could represent a promising target for dementia prevention.’

Dr Jonathan Stevenson (former MSc student at NDPH and current Otolaryngology-Head and Neck Surgery trainee with the Royal Australasian College of Surgeons), lead author for the study, said: ‘Difficulty hearing speech in background noise is one of the most common problems for people with age-related hearing impairment. This is the first study to investigate its association with dementia in a large population.’

It has been suggested that hearing impairment could lead to increased social isolation or depression, and that it is these factors that increase the risk of dementia. However, the study found little evidence that this was the case.

The study found that the risk of dementia remained similar when restricting the analysis to dementia which developed after nine years as well as within three years. This was explored as there is speculation that pre-diagnosed dementia could be driving the association between hearing loss and dementia. If this was the case, then an increased risk within three years but less so after nine years would be expected.

Dr Katy Stubbs from Alzheimer’s Research UK, said: ‘While most people think of memory problems when we hear the word dementia, this is far from the whole story. Many people with dementia will experience difficultly following speech in a noisy environment – a symptom sometimes called the ‘cocktail party problem’. This study suggests that these hearing changes may not just be a symptom of dementia, but a risk factor that could potentially be treated.’

‘Large studies like the UK Biobank are powerful tools for identifying genetic, health and lifestyle factors linked to conditions like dementia, but it is always difficult to tease apart cause and effect in this type of research.’

‘Anyone who has concerns about their hearing should speak to their GP.’