Hopes of slowing Alzheimer's disease from progressing have been boosted by two major breakthroughs in blood testing and brain scanning that could help detect the condition years before symptoms appear.

More than 520,000 Britons have Alzheimer's - the most common form of dementia, which is the UK's leading cause of death.

While there is no cure, early diagnosis of the disease can help slow progression and manage symptoms, which include memory loss, difficulty concentrating, mood changes and problems following conversations.

Now, researchers say new blood tests and brain scans could identify the signs of Alzheimer's years before symptoms emerge - raising the possibility of earlier diagnosis and treatment for thousands of patients. 

Published in two separate papers in The Lancet, the findings have been hailed by experts as an 'exciting' step forward.

It could also strengthen the case for NHS approval of two drugs - initially rejected due to cost - which can slow the progression of Alzheimer's if the disease is caught early.

The first study found that the proteins which have been linked to dementia - known as biomarkers - could be detected in middle-aged adults through a simple blood test.

Researchers analysed levels of amyloid-beta protein plaques and phosphorylated tau - signs of Alzheimer's when they accumulate in the blood - of 1,350 dementia-free adults from the US with an average age of 61.

They found that those with higher levels of these biomarkers had a worse cognitive performance - the term for how well the brain can perform tasks - as well as declining memory functions and the ability to process information. 

A version of this type of test was approved by the Food and Drug Administration (FDA) last year in the United States, although it is not yet part of NHS care.

Experts believe the FDA approval could pave the way for similar tests to become available in Britain in future. 

If approved, the findings suggest that the tests could help identify the early signs of Alzheimer's disease sooner.

Authors of the study wrote: 'These findings support the concept that Alzheimer's disease begins decades before clinical symptoms emerge and highlight the potential value of plasma biomarkers for early detection in the general population.'

They added that identifying individuals with early Alzheimer's disease could help assist research 'aimed at delaying or preventing the onset of dementia'.

Experts not involved in the study welcomed the findings, while cautioning that further research is still needed. 

Dr Richard Oakley, associate director of research and innovation at Alzheimer's Society, said:

'Dementia is the UK’s biggest killer and early and accurate diagnoses have never been more important.

'Blood-based biomarkers offer a promising, cost-effective and less invasive way of detecting Alzheimer's disease so it's encouraging to see momentum in this area.

'Earlier diagnosis unlocks access to treatments, support and help sooner. This study suggests blood tests could help detect Alzheimer’s disease in people in their early 60s – a group largely overlooked in previous research, which focused on older adults.'

Professor Paresh Malhotra, head of the division of neurology in the department of brain science, Imperial College London, said: 'It is also critical that we keep in mind that having an abnormal blood test is not in itself a clinical diagnosis and does not mean that someone will inevitably get dementia. 

'At the moment we only really understand what these tests mean when there is evidence of cognitive impairment, so they can be helpful where there has been a clinical assessment but we do not yet fully understand their implications when they have been done without any such assessment or in people where there is no objective evidence of cognitive difficulties.' 

The results of the study could also strengthen the case for manufacturers Eli Lilly and Eisai, who made the drugs donanemab and lecanemab, respectively.

Both were shown to delay progression from mild to moderate Alzheimer's by up to six months - in early, symptomatic Alzheimer's - and were licensed for use in the UK in 2024.

But they were not made available on the NHS after the National Institute for Health and Care Excellence (NICE) deemed their benefits 'too small' to justify the cost.

The decision was appealed by Eli Lilly and Eisai but no decision has yet been made.

The second study found that a new type of brain scan could detect tau proteins - another key Alzheimer's biomarker - more effectively than the current methods used in Europe and the US. 

Researchers studied 682 participants from the US and Canada using two different PET brain scans, which use small amounts of radiation to reveal disease including cancer. 

The new scan used an experimental tracer - the formal term for the radiation - called MK6240, while the current method uses a tracer known as Flortaucipir. 

Among cognitively healthy adults, the newer tracer detected more than twice as many early tau-positive cases as the standard scan. 

It also identified significantly more tau in people already showing signs of cognitive impairment.

Researchers believe the findings suggest that current brain scans may be missing many cases of early tau build-up linked to Alzheimer's disease.

The study also highlights the potential of the newer tracer, which is not yet approved for routine clinical use in either Britain or the US. 

Experts again welcomed the findings. 

Roslyn Bill, professor of Biotechnology at Aston University, said 'this work represents an important advance for the Alzheimer's disease field'.

Tara Spires-Jones, professor of neurodegeneration at the University of Edinburgh, and division lead in the UK Dementia Research Institute, said: 'These are both well conducted studies that advance what we know about detecting the early brain changes associated with Alzheimer's disease. 

'It is important to note that while these are important scientific findings that will be very useful for research and clinical trials, neither the blood test nor the brain scans investigated are available for routine clinical use in the UK.' 

Dr Jacqui Hanley, head of research funding at Alzheimer's Research UK, added: 'In the UK, many people wait far too long for a dementia diagnosis, meaning they often miss out on these opportunities. This is why there's so much excitement around the potential for blood tests, alongside other assessments.

'Accurate blood tests could improve how a diagnosis is made, as they are less invasive, scalable and potentially more accessible than existing tools such as PET brain scans and lumbar punctures.

'Detailed brain imaging remains important for understanding the extent and stage of disease more precisely, which is critical for research and treatment decisions. The study of tau PET scans suggests newer methods might detect Alzheimer's‑related changes earlier than existing techniques, which could enable earlier identification of disease and more precise selection of participants for clinical trials.

'As exciting as the results of these two observational studies are, we will need further research in larger and diverse groups of people before the approaches could be used routinely. We are still learning how these biomarkers behave over time, especially in people who are otherwise healthy, and we do not understand why some people can have these biomarkers yet not develop dementia.'

The findings come after the Daily Mail and Alzheimer's Society partnered in a drive to beat dementia, which claims 76,000 lives each year.

The Defeating Dementia campaign aims to raise awareness of the disease, in an effort to increase early diagnosis, boost research and improve care.