An early warning test for Alzheimer’s disease could enable doctors to deliver treatment 10 years before a diagnosis is usually made, helping to delay the onset of symptoms.
Researchers at the Mayo Clinic in the US have developed a tool to estimate the risk of a person developing memory and thinking problems associated with Alzheimer's disease, years before symptoms first appear.
In its early stages, the condition can be notoriously difficult to diagnose. Common indicators such as memory loss and confusion can be related to the effects of ageing, while patients often conceal memory loss – further delaying diagnosis.
Research, published in The Lancet Neurology journal, built on decades of data from the Mayo Clinic Study of Ageing – one of the world's most comprehensive population-based studies of brain health. It has assessed more than 7,000 people in Minnesota and analysed the effect of age-related mental decline.
The study aimed to understand cognitive decline, identify risk factors and develop predictive tools.
It found that women have a higher lifetime risk of developing dementia and mild cognitive impairment than men, while those carrying a specific genetic variant, APOE-e4, were also more likely to develop Alzheimer’s.
"What's exciting now is that we're looking even earlier – before symptoms begin – to see if we can predict who might be at greatest risk of developing cognitive problems in the future," said Dr Clifford Jack, a radiologist and lead author of the study.
Brain markers
Alzheimer's is marked by two key proteins in the brain: amyloid, which forms plaques, and tau, which forms tangles.
Drugs recently approved by the US Food and Drug Administration remove amyloid from the brain and can slow the rate of disease progression. By combining several factors, including age and gender, the prediction model helps doctors to determine when to begin treatment.
Using the data, researchers can calculate the likelihood of a person developing MCI or dementia within 10 years, or over the predicted lifetime. Of all the predictors evaluated, the brain amyloid levels detected through PET scans had the biggest effect on lifetime risk of MCI and dementia.
Currently in the research stage, the diagnostic tool represents a major step towards more personalised care, with next generation tests likely to incorporate blood-based biomarkers, which could make testing more accessible.
Dr Derk Krieger, professor of neurology at Fakeeh University Hospital in Dubai, said the hospital was already testing younger patients more at risk of developing Alzheimer’s in later life.
“I would say from age 55 you can actually diagnose Alzheimer's disease pre-symptomatic, with a blood test,” he said. “What we're looking for is people with slight clinical findings like slipping words or memory problems. These are tiny things that you always wonder if it is ageing, or is it a problem?
“If you have any kind of cognitive impairment, subjectively of the patient or more importantly, from the caregivers, then these patients should be screened.”
That process begins with an evaluation of family history of the disease, followed by a blood test and then a potential brain scan to search for the build up of protein plaques that can lead to memory loss. “Alzheimer's disease starts 20 years before the first clinical symptoms,” Dr Krieger said.
Delaying symptoms
Dementia medications, primarily for Alzheimer’s, include cholinesterase inhibitors that boost brain communication, which can ease memory and thinking issues. Newer drugs such as lecanemab and donanemab, target amyloid plaques to slow decline, but are expensive and come with risks such as brain swelling.
AS the global population ages, Alzheimer’s is predicted to reach epidemic proportions. At least 55 million people are currently living with the condition, with that number expected to increase to 78 million by 2030 and 139 million by 2050, Alzheimer's Disease International said.
Dr Taleb Rooeintan, a consultant in neurology at Medcare Hospital Sharjah, said an early diagnosis can have a profound impact on patients. “Early diagnosis of Alzheimer's disease can improve patient outcomes by enabling timely initiation of disease modified therapy, such as anti-amyloid monoclonal antibodies, which are approved for use in mild cognitive impairment or mild dementia stage,” he said.
“They have already demonstrated efficacy in slowing disease progression when started early. Early diagnosis can facilitate proactive planning, shared decision making and access to support service before significant function decline occurs."
