Is hearing loss an inevitable facet of aging? A growing body of research suggests it can be a warning sign of a health problem – and shouldn’t be ignored. Earlier this week, a study by scientists at Queen Mary University of London, which used the health records of over a million people living in east London between 1990 and 2018, found that hearing loss can be a warning sign of Parkinson’s disease.
“This will be news, I think, to most doctors,” says Jason Warren, professor of neurology at University College London. “This is part of a larger theme that emerges more generally, which suggests that hearing loss is associated with neurodegenerative diseases.”
Scientists still don’t know exactly why hearing loss could mean early signs of underlying processes affecting the brain and central nervous system, Warren says, but there are some clues. Research has already shown that people with Parkinson’s disease – a progressive neurological disorder that affects movement, leading to tremors and stiffness – can perceive sounds abnormally.
“It’s taken for granted, but it’s very hard for the brain to hear,” he explains. “In everyday life, we usually try to listen to a conversation in the presence of background noise, and it’s a complicated task for the brain. Anything that will reduce the efficiency of brain processing will tend to affect this process, because hearing is almost like a stress test for the brain.
The new study, which was conducted primarily in people over 60, adds to an existing collection of research showing that hearing loss can be an early indicator that a person is at risk of developing dementia. Neuroscientists are still trying to unravel the nature of this connection.
Helen Henshaw, a researcher at the NIHR Nottingham Hearing Biomedical Research Center, says there are four plausible explanations. As in Parkinson’s disease, hearing loss may indicate underlying brain deterioration, but it may also be a determining factor in the disease.
“When you have hearing loss, you get less auditory brain stimulation,” she says. “These areas that typically process auditory information may start to deteriorate. They’re not getting the information to process, so they’ll slowly decrease in size. They won’t be as active as they used to be.”
But if you’ve recently noticed that your hearing has started to deteriorate or you’ve developed a hearing problem such as tinnitus, there’s no need to panic right away. Both Warren and Henshaw point out that hearing loss is extremely common – according to the Royal National Institute for Deaf People there are 12 million adults in the UK with a significant level of hearing loss – and the vast majority of these people will not have a neurodegenerative condition.
However, it is important to have any signs of hearing loss checked by a specialist. There can be a variety of underlying causes, ranging from genetics and ear infections to lifestyle and dietary factors. Surveys have shown that hearing loss is more prevalent in areas of the UK where there is greater social deprivation, and it has been linked to type 2 diabetes and other cardiovascular problems. Although hearing damage is unlikely to be reversed, treating dietary problems or lifestyle-related conditions, such as type 2 diabetes, can prevent further deterioration.
Henshaw says research done on dementia shows that tackling significant hearing loss through measures such as reducing excessive noise exposure – a common cause in young adults – or wearing hearing aids, can be a crucial preventive step. A report from the University of Manchester found that 20% of people who received hearing aids do not use them.
“I think the public perception of hearing loss, and hearing ability in general, is pretty poor,” says Henshaw. “It’s not in the public eye like the loss of sight. But the sooner we deal with it, the better our quality of life and the better our ability to mitigate some of these truly negative consequences on social, mental and physical well-being.
But for Parkinson’s and dementia researchers, the next steps are to try to dig deeper to identify the specific types of hearing loss that appear to be linked to the onset of neurological problems. If they can establish why hearing is linked to the underlying pathology and integrate it into screening tools, it could eventually lead to better treatments because in both cases patients are usually diagnosed too late.
“We need very careful and detailed studies of what kind of hearing problems people with early Parkinson’s disease and dementia might have,” Warren says. “Standard hearing tests aren’t the best at detecting problems in the brain, whether someone can really make sense of a sound or perceive it correctly against background noise. My research group is trying to figure out what the hallmarks of this hearing loss could look like.This is a truly exciting time for the field.
For advice and assistance with hearing loss, contact the RNID