Gut microbiome could help identify people at risk of dementia
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In what is thought to be the first study of its kind, researchers from Cardiff University and Imperial College London examined both gut bacteria and chemicals. Their findings could support earlier diagnosis and help spot people at risk of faster decline.
The study is published in the journal MedComm.
"This study leads us to conclude that the gut could offer a window into what's happening in the brain at the earliest stages of cognitive decline," said Paul Morgan, professor of complement biology in the Division of Infection and Immunity.
Gut bacteria and chemicals reveal differences
The researchers analyzed fecal samples from 35 older adults, most of whom were part of couples living together in which one partner had mild cognitive impairment and the other did not, and used machine learning to see whether the samples could help diagnose the condition and predict how quickly it progresses.
The study found that people with mild cognitive impairment had a different mix of gut bacteria compared with people without cognitive impairment. In particular, people with mild cognitive impairment displayed significantly elevated levels of the bacteria Izemoplasmatales spp. and the gut chemical proline. They also showed decreased levels of Ruminococcus spp. and Lachnospira spp. bacteria and lower levels of the chemical fumaric acid.
These bacteria belong to a larger group that has been linked to brain health in previous studies.
The team also tested for these bacterial markers in an independent group of people from a previous study and found that the markers could still distinguish people with mild cognitive impairment from healthy individuals.
Markers linked to faster cognitive decline
The researchers followed people with mild cognitive impairment for a year. They found that those whose initial samples had higher levels of the bacteria Bilophila spp. and the chemicals arginine, aspartic acid and hypoxanthine and lower levels of Coprococcus spp. showed a faster decline in memory and thinking skills.
Study co-author Dr. You Zhou, of Cardiff University, said, "Mild cognitive impairment affects around one in four older adults worldwide, but we have no simple way of telling who will go on to decline quickly."
"We found that a combination of gut bacteria and chemicals could distinguish people with mild cognitive impairment from healthy individuals with high accuracy, and certain gut chemicals were strongly linked to faster decline over the following year," said Zhou, a senior lecturer.
Larger studies needed to confirm findings
"This was a small study and the findings need confirming in larger groups, but they point toward simple, noninvasive tests that could one day support earlier diagnosis."
Co-author Julian Marchesi, of Imperial College London, said, "Gut bacteria and chemicals are increasingly recognized as an important link between the gut and the brain. By looking at both together, we get a much fuller picture of what's changing in people with mild cognitive impairment. Future studies on larger groups of patients will help pinpoint exactly which microbes and chemicals matter most."
The researchers say further studies are now needed in more diverse groups and to examine the influence of diet, lifestyle, ethnicity, environment and genetic risk.
More information
Birong Zhang et al., Profiling Gut Microbiome and Metabolites Aids Diagnosis and Prediction of Progression in Mild Cognitive Impairment, MedComm (2026). DOI: 10.1002/mco2.71045
Key medical concepts
Mild Cognitive ImpairmentCognitive Declines
Clinical categories
NeurologyGastroenterologyHealthy agingCommon illnesses & Prevention Provided by Cardiff University Who's behind this story?
Swati Mestri
Swati Mestri holds a bachelor's degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space. Full profile →
Robert Egan
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