Hearing loss raises risk of dementia by 17 per cent by speeding up ageing of the brain, scientists believe.
In people aged 45 to 64 years old, the risk was 40 per cent, according to a study.
Straining to hear causes the brain to work differently, which could cause its structure to change and lead to symptoms of dementia.
The brain may divert its resources from other areas in order to fully understand and process sounds or lip-read.
Hearing loss is known to be a key driver of the memory-robbing disorder, but scientists are still trying to understand why.
Around 40 per cent of people over 50 in the UK have some form of hearing loss, according to Age UK.
Hearing loss raises risk of dementia by 17 per cent by speeding up ageing of the brain, scientists in Taiwan believe
Researchers led by the National Taiwan Normal University collected data from the National Health Insurance Research Database of Taiwan.
The study included 8,135 patients with newly diagnosed hearing loss and an equal number of individuals without hearing loss for comparison.
Among the 16,270 study participants, 1,868 developed dementia.
Among the dementia patients, almost two thirds (58.6 per cent) had difficult hearing, compared with 41.4 per cent who did not.
Of those with hearing loss, the dementia incidence rate was 19.38 per 1,000 person-years compared with 13.98 per 1,000 person-years in those with hearing intact.
Patients with hearing loss had a higher risk of dementia, especially those 45 to 64 years old whose risks increased by 121 per cent.
Six other conditions were also found as risk factors – cerebrovascular disease, diabetes, anxiety, depression, alcohol-related illnesses and head injury.
The team, led by Dr Chin-Mei Liu, said: ‘The risk of HL [hearing loss] increases with age and is associated with lower scores on tests of memory and a higher risk of incident all-cause dementia.
‘Evidence suggests that even mild levels of HL increase the long-term risks of cognitive decline and dementia.
‘Hearing loss is associated with a higher risk of dementia, and findings suggest that hearing protection, screening, and treatment may be used as strategies to mitigate this potential risk factor.’
The findings support a slew of studies linking hearing loss and dementia, for which several neural changes have been suggested as the reason.
The strain of trying to hear better may cause the brain’s function to reduce because it speeds up the ageing process, the researchers said.
A person hard of hearing uses more of the frontal lobe in the brain, which is responsible for language and communication.
The constant effort causes a ‘cognitive load’, consequently affecting processes such as memory and executive function, which helps to do tasks.
Because a person with hearing has lost one of their senses, they may compensate by using more of their other senses, particularly vision.
This cross-over of senses in the brain has been shown to affect the brain’s normal functioning by speeding up brain tissue depletion.
Dr Sara Imarisio, Head of Research at Alzheimer’s Research UK, said: ‘This study adds to growing evidence of a link between hearing loss and dementia but it’s still unclear what is driving this link.
‘The only way to find out if treating hearing loss could lower dementia risk is through carefully designed clinical trials.’
Scientists have previously said that, although people’s brains are known to become smaller with age, the rate of shrinkage is quicker in people who are deaf.
A team at John Hopkins University, in Baltimore, did MRI brain scans of 126 patients every year across a decade as well as hearing tests.
After analysing their MRIs over the following years, Dr Frank Lin and his colleagues published their findings in 2014 – participants whose hearing was already impaired at the start of the study had accelerated rates of brain deterioration compared to those with normal hearing.
A key theory for why hearing loss may be fueling dementia is that it causes people to isolate themselves, which has implications for mental health.
Action on Hearing Loss estimates that there are more than 10million people in the UK with some degree of hearing impairment or deafness, which is around one in six.
There is no cure for age-related hearing loss, and many experts believe hearing aids can help prevent against dementia.
Alzheimer’s is the most common form of dementia, affecting around 500,000 Britons. Scientists still have not nailed down what causes it and a cure is yet to be found.
The focus of research is on developing techniques which can catch the condition at an earlier stage.
Dr Imarisio said: ‘While researchers continue to investigate the link between hearing loss and dementia risk, we know that there are things we can all do to reduce our risk.
‘Eating a healthy diet, only drinking within recommended limits, staying mentally and physically active, keeping weight and cholesterol in check, and not smoking can all support good brain health.’
WHAT IS DEMENTIA? THE KILLER DISEASE THAT ROBS SUFFERERS OF THEIR MEMORIES
Dementia is an umbrella term used to describe a range of neurological disorders
A GLOBAL CONCERN
Dementia is an umbrella term used to describe a range of progressive neurological disorders, that is, conditions affecting the brain.
There are many different types of dementia, of which Alzheimer’s disease is the most common.
Some people may have a combination of types of dementia.
Regardless of which type is diagnosed, each person will experience their dementia in their own unique way.
Dementia is a global concern but it is most often seen in wealthier countries, where people are likely to live into very old age.
HOW MANY PEOPLE ARE AFFECTED?
The Alzheimer’s Society reports there are more than 850,000 people living with dementia in the UK today, of which more than 500,000 have Alzheimer’s.
It is estimated that the number of people living with dementia in the UK by 2025 will rise to over 1 million.
In the US, it’s estimated there are 5.5 million Alzheimer’s sufferers. A similar percentage rise is expected in the coming years.
As a person’s age increases, so does the risk of them developing dementia.
Rates of diagnosis are improving but many people with dementia are thought to still be undiagnosed.
IS THERE A CURE?
Currently there is no cure for dementia.
But new drugs can slow down its progression and the earlier it is spotted the more effective treatments are.
Source: Dementia UK
