Blood test could spot dementia years earlier

A blood test could help spot early cognitive decline years before a standard dementia diagnosis is possible, research suggests.

Scientists found that subtle changes in the blood, caused by chemicals produced by gut bacteria, may reveal the earliest signs of cognitive decline long before symptoms become obvious.

The findings suggest the link between the gut and the brain, often called the gut-brain axis, may play an important role in early cognitive ageing.

Co-author Dr Simon McArthur, from Queen Mary University of London, said: “While we’re not yet at the point of providing a diagnostic test, our work suggests we may be able to use dietary and microbial information to help catch the presence of dementia earlier in life, potentially even before significant brain damage has occurred.

“We hope this work will pave the way for simple, non-invasive blood tests capable of identifying people at higher risk of memory decline years before dementia is typically diagnosed.”

Researchers analysed blood and stool samples from 150 adults aged 50 and over, ranging from healthy individuals to those with mild cognitive impairment, or MCI, which is often a precursor to dementia.

A third group included people experiencing subjective memory lapses, who still performed normally on standard cognitive tests but felt something was not quite right.

Fasting blood samples were tested using highly sensitive laboratory techniques to measure 33 key molecules produced by gut microbes and from diet.

Stool samples were used to map the communities of bacteria living in each participant’s digestive system.

Using artificial intelligence and machine learning, the researchers built a model based on just six of these molecules.

It classified people into the three groups with 79 per cent accuracy and distinguished healthy adults from those with mild cognitive impairment with more than 80 per cent accuracy.

Lead researcher Dr David Vauzour, from UEA’s Norwich Medical School, said: “Identifying biological warning signs earlier could allow for timely lifestyle changes, targeted interventions, and better monitoring.

“Even in people who had only just begun noticing mild memory changes, there were clear shifts in both their gut bacteria and the metabolites they release into the bloodstream.

“Crucially, the chemical changes in the volunteers’ blood were strongly linked to differences in specific gut bacteria.

“This adds weight to growing evidence that the so-called gut-brain axis, the communication network between our digestive system and the brain, may play an important role in cognitive ageing.”

The study also highlights the potential of the gut microbiome as a target for protecting brain health.

Dr Vauzour said: “If particular gut bacteria or the chemicals they produce contribute to early cognitive decline, treatments involving diet, probiotics, microbiome-based therapies, or personalised nutrition could one day form part of dementia prevention strategies.”