Alzheimer’s ‘more prevalent than previously thought’ among the elderly

Researchers used a simple blood test to look for biomarkers associated with the development of dementia.

The study also found more than one in 10 people over the age of 70 would meet the criteria for drugs that can slow down the early stages of Alzheimer’s.

Experts described the disease as a “global challenge” and said it is “vital that we are able to detect signs of dementia at the earliest possible stages”.

For the study, researchers at King’s College London, Stavanger University Hospital and University of Gothenburg analysed 11,486 blood samples provided by people over the age of 57 taking part in the Trondelag Health Study (HUNT) in Norway.

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They looked for the frequency of proteins in the blood that have been linked to cognitive impairment, or the gradual decline in thinking, memory and reasoning.

The analysis found that the frequency of Alzheimer’s disease neuropathological changes (ADNC) – deposits of proteins in the brain that lead to the death of nerve cells – increased with age.

It was higher in older people but lower than previously estimated in the younger groups, according to the study.

ADNC was present in fewer than 8% of those aged 65-69, increasing to 65.2% in patients over 90.

In people over 70, the study found 10% had pre-clinical Alzheimer’s disease, which has no symptoms, while 9.8% had Alzheimer’s dementia.

Some 10.4% had prodromal Alzheimer’s, the stage between pre-clincal and dementia, when memory and thinking problems are noticeable due to cognitive impairment.

Researchers suggest 11% of the over-70s group would be eligible for antibody treatments which slow down the early stages of the disease.

These drugs include donanemab and lecanemab, which are licensed for use in the UK but will not be made available on the NHS after the spending watchdog deemed their benefits “too small” to justify the cost.

Dag Aarsland, a professor of old age psychiatry at King’s IoPPN, said: “In an ageing global population, the assessment and treatment of dementia presents a significant challenge.

“Our study used a simple blood test to establish changes that contribute to cognitive impairment in those with dementia.

“In doing so, we found that around 11% of participants over the age of 70 meet the eligibility criteria for monoclonal antibody treatments that can potentially slow the impact of cognitive decline in these individuals.

“If we are to meet this global challenge, it is vital that we are able to detect signs of dementia at the earliest possible stages. This blood test looks to be an effective means of providing that clarity at scale.”

Elsewhere, researchers found that ADNC “was more prevalent in individuals with lower education”.

Blood tests to diagnose Alzheimer’s disease are also not available on the NHS.

At the moment, doctors use lumbar punctures or PET scans to test for ADNC.

However, a trial announced in September will recruit 1,100 people from memory clinics to explore how well a blood test works on the health service, with results expected in three years.

Reacting to the findings, David Thomas, head of policy and public affairs at Alzheimer’s Research UK, said: “High quality studies like this are crucial to enhancing our understanding of how blood tests for Alzheimer’s could be used in clinical practice.

“These tests have huge potential in supporting an early and accurate dementia diagnosis.

“They are less invasive, relatively inexpensive and more scalable than existing tests that detect the biological signs of Alzheimer’s diseases, such as PET scans and spinal fluid sampling.

“However, the detection of the proteins linked with Alzheimer’s disease is not in itself a diagnosis.

“Some people will develop these proteins but never go on to experience the symptoms of the disease. Therefore, it’s important to interpret these findings with caution.

“Blood test results can also be less sensitive in older adults and future studies should address this by testing across a wider range of ages.

“We need to generate more evidence so we can use these tests in the NHS.

“Alzheimer’s Research UK, Alzheimer’s Society and other partners are funding the READ-OUT and ADAPT studies of blood tests to develop these insights. Alzheimer’s Research UK is calling for the Government to invest in the NHS services which provide dementia diagnosis in order to pave the way for new innovations in clinical practice.”

Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, added: “This is the first time we’ve seen this type of data from such a large group of people, with over 11,000 blood samples analysed.

“It is a stark reminder of the scale of dementia. We already know it’s the UK’s biggest killer, but its impact may be even bigger than we think.

“Blood tests could transform how Alzheimer’s disease is diagnosed. They are quicker, cheaper and can be easier for patients than scans or lumbar punctures. Ultimately, these tests could help many more people get a diagnosis earlier.”