Simple blood test may detect dementia warning signs years before symptoms appear, paving the way for targeted interventions and better monitoring

A simple blood test could identify people at higher risk of dementia years before any symptoms appear, researchers say.

The breakthrough, which measures chemicals related to gut bacteria and diet, could change how the condition is detected and treated. 

With dementia, early intervention is vital. It increases the amount of treatment options available and gives patients time to make lifestyle changes which can protect the brain and potentially prolong the onset of the disease.

Researchers from the University of East Anglia studied 150 adults aged 50 and over. 

They were split into three groups of fifty; a healthy control group with no cognitive impairment; a group with Subjective Cognitive Impairment (SCI), people who report to experience memory and thinking issues but test normally; and those with Mild Cognitive Impairment (MCI), who had measurable early cognitive decline, a recognised precursor to dementia. 

The cohort gave blood and stool samples which were analysed using highly sensitive lab techniques to scan for chemicals produced by gut bacteria and diet, known as metabolites. 

Then, using advanced computer modelling and AI, the researchers looked for patterns in metabolites to see if they revealed early signs of cognitive decline.

They found clear changes in both gut bacteria and the chemicals they release into the bloodstream in those in the MCI group who had just begun noticing mild memory problems.

A model based on just six chemicals was able to classify participants into the three groups with 79 per cent accuracy. It could distinguish healthy adults from those with mild cognitive impairment with over 80 per cent accuracy.

Dr David Vauzour, lead researcher from UEA’s Norwich Medical School, said: ‘Early detection is critical because by the time symptoms appear, much of the brain damage has already happened.

‘Identifying biological warning signs earlier could allow for timely lifestyle changes, targeted interventions, and better monitoring.’   

Around 982,000 people are currently living with dementia in the UK, a number expected to rise to 1.4 million by 2040. 

Globally, over 55 million people are affected, and this figure could reach 139 million by 2050.

The research, published in the journal Gut Microbes, also highlights the potential of the gut microbiome as a target for protecting brain health. Further research could identify certain supplements – such as probiotics – which could bolster people against the disease. 

Dr Vauzour added: ‘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 gut-brain axis – the communication network between our digestive system and the brain – may play an important role in cognitive ageing.

‘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.’    

The new research was led by the University of East Anglia in collaboration with Queen Mary University of London. It was part-funded by Alzheimer’s Research UK.

Professor Fiona Carragher, Chief Policy and Research Officer at Alzheimer’s Society, said: ‘Blood tests could transform how we diagnose dementia and even identify a person’s risk of developing dementia in the future. Studies like this are helping to build a clearer picture of the early biological changes linked to the condition.

‘This is a small study looking at associations at a single point in time, so we cannot say whether these changes cause cognitive decline or are a result of it or whether these individuals went on to develop dementia. It does, however, add to a growing field of research looking at the connection between gut and brain health.

‘Understanding risk earlier could be key to helping people access support, take steps to reduce their risk, and take part in research. Alzheimer’s Society part funded the influential Lancet Commission on dementia prevention, intervention and care, which identified 14 modifiable risk factors for dementia and showed that up to 45 per cent of dementia globally may be preventable. 

‘Dementia is one of the biggest challenges facing our health and care system, and with the number of people affected set to rise to 1.4 million by 2020, prevention must be a central part of how we tackle it.’

Finding ways to stop dementia from taking hold is being treated as a global health emergency, with thousands of researchers exploring potential causes and early warning signs.  

In February, Swedish researchers isolated 17 factors that have the largest influence on two of the most common forms of dementia, Alzheimer’s disease and vascular dementia.

While some are predetermined or unchangeable, including age, genetics and sex, others, such as alcohol consumption, physical activity and smoking, are under a person’s control.

The team from Lund University in Sweden identified 17 fixed and flexible factors: heart disease, high cholesterol, heart medications, stroke status, age, blood pressure, smoking status, diabetes, low and high alcohol consumption, sleep, carrying the APOE e4 gene, depression, living alone, BMI, sex and education.