Difficulty hearing speech in noisy rooms may be early sign of dementia

An impressively large study following more than 80,000 people for 11 years has found that difficulty hearing speech in noisy environments can be an early-warning sign of later-life dementia. The next steps for the research will be to investigate whether immediately treating mid-life hearing impairments can reduce the risk of dementia developing in a person’s senior years.

“Difficulty hearing speech in background noise is one of the most common problems for people with age-related hearing impairment,” says lead author on the new study, Jonathan Stevenson. “This is the first study to investigate its association with dementia in a large population.”

In a loud social environment it can sometimes be challenging to filter out other voices and focus on a single speaker. Known as the “cocktail party effect,” difficulty understanding speech in these kinds of scenarios is often considered an early indication of hearing impairment.

In general, mid-life hearing declines have been associated with an increased risk of later-life Alzheimer’s disease and other forms of dementia. This new research set out to explore whether this “cocktail party effect,” referred to as a speech-in-noise (SiN) hearing impairment, specifically can be associated with the development of dementia.

More than a decade ago the researchers recruited 82,000 cognitively healthy subjects over the age of 60. SiN impairment was evaluated initially through a test where subjects are tasked with identifying spoken numbers while white-noise is playing. The cohort was grouped into three SiN categories: normal, insufficient and poor.

Across an 11 year follow-up period the researchers detected 1,285 cases of dementia in the cohort. Compared to those with normal SiN results at the beginning of the study, those in the insufficient SiN drop were 61 percent more likely to develop dementia, and those in the poor SiN group were 91 percent more likely.

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

Stubbs is clear to note the challenges of determining causality from this kind of research. Jason Warren, a neurologist from University College London (UCL) who did not work on this study, says the implications of this research could be far-reaching if it can be established that treating mid-life hearing impairment reduces later-life dementia risk. But, Warren says, these findings do raise a number of questions.

“Does reduced noisy listening promote dementia or is it an early warning ‘stress test’ for the ageing brain? What is actually happening in the brain as hearing loss occurs? And what should we recommend to older people worried about their hearing and wishing to protect their memory?” Warren asks.

David Curtis, from the UCL Genetics Institute, is a little more skeptical about the suggestion that treating hearing impairment could influence dementia risk. He agrees it is plausible this kind of SiN impairment is an early-warning sign of dementia, but he is not convinced hearing aids can reduce dementia risk.

“…it is quite difficult to see how hearing problems could impact on the mechanisms of neuronal degeneration and cell loss which can ultimately manifest in a diagnosis of dementia,” says Curtis, who did not work on the new study. “Thus, while this study confirms that the conditions are associated with each other I am not convinced that it establishes a causal relationship from hearing problems to dementia.”

The new research was published in the journal Alzheimer’s & Dementia.

Source: University of Oxford