Changes in Gut Health May Appear in Alzheimer’s Before Cognitive Symptoms, Study Finds

An imbalance of gut bacteria has been linked with a variety of illnesses, including inflammatory bowel disease, irritable bowel syndrome, breast cancer spread, and even diabetes. A new study provides more evidence that it may be linked with Alzheimer’s, too.

Research recently published in the journal Science Translational Medicine investigated the gut microbiome of patients with evidence of preclinical Alzheimer’s. This builds on past research that has shown the gut bacteria in symptomatic patients is different from their peers without the disease. The new study, conducted by a team from Washington University School of Medicine, showed that there’s a difference even before cognitive symptoms occur.

The findings could help with earlier treatment for Alzheimer’s patients.

Dr. Beau M. Ances, study co-author and professor of neurology, explains, “By the time people have cognitive symptoms, there are significant changes that are often irreversible. But if you can diagnosis someone very early in the disease process, that would be the optimal time to effectively intervene with a therapy.”

To conduct their research, the team recruited 164 cognitively normal people and looked at their brain scans, cerebrospinal fluid, and stool samples. They used these to study each participant’s gut microbiome and to see if they had signs of amyloid beta and tau accumulation, which are associated with Alzheimer’s and were present in 49 participants.

Of those with tau and amyloid beta accumulation, there were marked differences in gut bacteria compared with the other participants, including in the types of bacteria present and in the processes they help drive. The team found that these changes were only linked with the biomarkers of beta amyloid and tau, not with neurodegeneration. They say this suggests the changes happen very early in the disease’s progression.

Though more research is needed, the study could help determine which specific gut markers may be linked with Alzheimer’s.

Dr. Gautam Dantas, study co-author and professor of laboratory and genomic medicine, explains, “We don’t yet know whether the gut is influencing the brain or the brain is influencing the gut, but this association is valuable to know in either case. It could be that the changes in the gut microbiome are just a readout of pathological changes in the brain. The other alternative is that the gut microbiome is contributing to Alzheimer’s disease, in which case altering the gut microbiome with probiotics or fecal transfers might help change the course of the disease.”

Dr. Ances adds that, should this link be confirmed, stool samples could also be an easy way to learn if you’re at high risk for Alzheimer’s.