DEVELOPING Alzheimer's or another form of dementia is many people's worst fear when it comes to ageing, according to a recent survey by YouGov.
And it's easy to see why. Outside the pandemic years, when Covid deaths slightly outnumbered dementia deaths (by 0.6 per cent), dementia and Alzheimer's disease have been the leading cause of mortality in the UK.
In care homes it's to blame for more than 65 per cent of deaths, data from the Office for National Statistics show.
But would you want to know, more than a decade in advance, that dementia was to be your fate?
How would that devastating news change your life, especially when there may be little you can do to delay its onset and science has repeatedly failed to come up with drugs to cure - or even radically slow - its progress?
These difficult questions are no longer just hypothetical.
In Britain, a University of Cambridge spin-off company, called Cognetivity Neurosciences, is beginning NHS trials of a simple, five-minute diagnostic test that, the firm claims, will instantly and accurately predict your risk of Alzheimer's in up to 15 years' time.
Most people are only diagnosed once symptoms - such as severe memory loss, confusion, forgetting words or becoming anxious and withdrawn - start to appear.
The new test is remarkably simple, says James Medcalf, commercial director of Cognetivity Neurosciences.
"In the test you are shown quickly - only for about 100 milliseconds - pictures that feature either an animal or no animal," he says.
"You are asked to respond quickly by pressing 'yes' or 'no', depending on whether you see an animal.
"In evolutionary terms, spotting an animal very quickly was vital for our survival.
"The task involves some of the most basic structures of our brains, such as the amygdala, which helps to regulate our fight-or-flight responses."
As the test relies purely on instinctive responses, we don't consciously learn how to perform it, so practice cannot improve a person's scores over time.
But why is this reaction important in terms of predicting dementia risk?
"In the earliest stages of Alzheimer's, it is not memory that gets affected," says Mr Medcalf.
"Research shows instead that it is your brain's processing speed that starts to slow, and this is what the new test shows."
It is designed to work on screens such as an Apple iPad. The company says the test is so straightforward that it plans to sell an abbreviated two-minute form to anyone who wants to use it at home.
"You could use it every day, to track how you're doing over the weeks," adds Mr Medcalf.
Pilot projects are under way at three NHS trusts, in Staffordshire, Sussex and the West Midlands, and two care homes, to try to pick up signs of mild cognitive impairment (MCI), where people start forgetting names, have trouble planning or organising things or get easily distracted.
An estimated one in 10 people with MCI develops dementia.
Meanwhile, scientists at the Centre for Neurodegenerative Diseases in Bonn, Germany, are working on a rather more complex test they believe will also predict if someone will get dementia up to five years before it develops.
They have identified three molecules in the blood, called microRNAs, that may indicate Alzheimer's risk. MicroRNAs act as chemical messengers between cells, transporting instructions about, for example, the building of essential new proteins.
In research published in the journal EMBO Molecular Medicine, the scientists described how 90 per cent of older people with very raised levels of the three molecules developed Alzheimer's within two years.
Andre Fischer, a professor of psychiatry who led the research, says: "An increased blood level of these three microRNAs can indicate that Alzheimer's symptoms will begin about two to five years later."
Researchers now hope to develop a simple blood test that can be applied in routine medical care to assess dementia risk.
They say it may also be possible to develop drugs that can reverse the increase in these microRNAs - potentially undoing some of the damage.
But how helpful is it to find out years in advance that you may be on course for an incurable illness?
Hannah Churchill, research communications manager at the Alzheimer's Society, said: "There is no sure-fire way to prevent the onset of dementia.
"Researchers believe that only around 40 per cent of cases may be preventable, by addressing risk factors such as hearing loss, smoking, excess drinking or obesity.
"The other 60 per cent of dementia cases may not be linked to modifiable risk factors.
"Our age and genetics will also play a role and are outside our control."
But not everyone thinks this renders risk-testing useless.
"There has always been this argument in dementia care: should we bother doing something if we can't do anything about it?" says Mr Medcalf.
"I say yes - at the very least you can put your affairs in order and give legal power of attorney to your loved ones in good time."
However, research suggests people prefer not to know their risk of dementia.
The Social Care Institute for Excellence, a UK charity, says many people with early signs of dementia "choose not to seek a diagnosis" because of concerns about the effect on their jobs, social lives and ability to drive.
In May 2020, psychiatrists at Yale University in the United States reported that adults aged over 65 who had recently been diagnosed with Alzheimer's or other types of dementia were twice as likely to die from suicide compared with those who didn't have dementia.
Authors of the study, published in the journal Alzheimer's & Dementia, said all patients should be given "suicide risk screening and additional support at the time of receiving a dementia diagnosis".
The Alzheimer's Society agrees that patients and loved ones should receive this support, including, says Hannah Churchill, access to peer support groups, education for carers and care planning.
It could also mean starting medicines that might help the person cope with their symptoms - such as Aricept, a drug which helps nerve cells damaged by dementia to keep communicating with each other.
It can temporarily ease some symptoms but cannot prevent the disease from worsening.
"For many, a dementia diagnosis may be a relief - an explanation for the changes they've been experiencing, especially if they have lived with symptoms for years," she says.
"And early diagnosis means better access to personalised care and support, such as occupational therapy, which means people with dementia can live well for longer."
So is there any prospect of a drug that could stop Alzheimer's in its tracks?
In October, scientists at Durham University revealed they had developed a futuristic £7,000 helmet that might be able to reverse dementia by zapping the brain with pulses of infrared light to boost memory and processing skills.
But the technology is several years away from routine use.
Hopes of a breakthrough in the search for a pharmaceutical solution were raised earlier this year by the fast-track approval in the US of aducanumab, a drug that could slow or halt Alzheimer's by reducing the build-up of a toxic protein - called amyloid - in the brain.
But the approval caused huge controversy, with some critics accusing the US Food and Drug Administration - which gave it the green light - of ignoring the unanimous verdict by its expert advisory committee that trial evidence failed to show that aducanumab is effective.
The injectable drug, which costs £42,000 per patient per year, is not available in the UK, but regulators are carrying out their own rigorous assessment to see if the clinical benefits justify a licence.
The drug would then have to be evaluated for cost benefit by the National Institute for Health and Care Excellence.
According to the charity Alzheimer's Research UK, that process is unlikely to be completed until "the middle of 2022 at the earliest".
© Daily Mail
