Early Detection Through the Gut Could Change the Course of Alzheimer’s

It may soon be possible to learn whether someone has Alzheimer’s disease before they show symptoms by examining the bacterial makeup in their intestines, according to a Washington University School of Medicine study.

Published June 14 in Science Translational Medicine, the study looked at the gut microbe community, called the microbiome, of 164 participants. Markedly different bacterial species were found in 49 participants, who were deemed at higher risk of developing dementia based on brain scans and cerebrospinal fluid.

Previous studies have made the connection between dysbiosis, or imbalance, of the gut microbiome and Alzheimer’s disease, though research remains unclear on whether a shift in the microbiome causes the disease or if the disease leads to a change in the bacterial composition. However, the new findings support that measures can be taken to delay symptom onset.

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

Research suggests that more than a decade before memory and cognitive symptoms appear, complex brain changes are emerging that are associated with Alzheimer’s, such as the formation of amyloid plaques or tau tangles.

This stage happens before dementia, but it doesn’t always lead to dementia. The National Institutes of Health has classified this stage as preclinical. There are also mild, moderate, and severe categories of dementia.

All study participants were cognitively normal and provided stool, blood, and cerebrospinal fluid samples; kept food diaries; and underwent PET and MRI brain scans.

Detecting Dementia

Only in the past two decades can biomarkers of the disease be detected in a living person, typically through a battery of tests. Blood tests alone can’t be used to diagnose Alzheimer’s, which was previously diagnosed only through autopsies.

Blood tests measure levels of beta-amyloid, a protein that accumulates abnormally in the brains of people with Alzheimer’s. These tests should be used in conjunction with other tests, such as imaging.

To distinguish participants already in the early stage of Alzheimer’s disease from those who were healthy, the researchers looked for signs of amyloid beta and tau accumulation through brain scans and cerebrospinal fluid.

“The nice thing about using the gut microbiome as a screening tool is its simplicity and ease,” Ances said. “One day, individuals may be able to provide a stool sample and find out if they are at increased risk for developing Alzheimer’s disease. It would be much easier and less invasive and more accessible for a large proportion of the population, especially underrepresented groups, compared to brain scans or spinal taps.”

Prevention Is Possible

Dr. Ann Hathaway, who specializes in reversing Alzheimer’s disease, said the real benefit of the study is that it gives doctors another tool to predict the disease in a phase during which prevention is entirely possible.

Another tool is the Montreal Cognitive Assessment, recommended by the Alzheimer’s Society, which measures cognitive function and can screen for dementia on a 30-point scale. Normal range is 26–30 points, with anything below 26 indicating dementia.

She’s seen patients scoring as low as 18 experience symptom reversal. Hathaway and others across the United States are currently recruiting for a study to see whether precision medicine and lifestyle interventions can reverse early and mild forms of dementia.

“Once you’ve had cognitive decline for five years or 10 years, it does become much harder to reverse,” Hathaway said. “That’s why it’s our mission to try to catch this early.”

Hathaway often collaborates with Dr. Dale Bredesen, who has done research and written about the reversal of dementia in two books, the most recent “The First Survivors of Alzheimer’s.” Many doctors and programs now offer protocols aimed at stopping cognitive decline.

Sharp Again Naturally provides online group and individual coaching that addresses environmental risk factors of the disease through lifestyle changes. Hathaway employs health coaches to work with patients. Reversal takes determination and commitment, along with the willingness to change eating and other habits.

“People still don’t know it’s reversible. The word is very much not out there,” Hathaway said. “We do see Alzheimer’s disease as a multifactorial diagnosis and we do think everyone should start to understand what their risk is, ideally in their 40s, for all the common diseases that take us down.”

Microbiome Matters

The microbiome’s role is still not widely understood. The Washington University researchers have started a five-year follow-up study designed to figure out whether dysbiosis is a cause or a result of the brain changes seen in early Alzheimer’s disease.

“If there is a causative link, most likely the link would be inflammatory,” said co-corresponding author Gautam Dantas, professor of pathology and immunology, biomedical engineering, molecular microbiology, and pediatrics.

“Bacteria are these amazing chemical factories, and some of their metabolites affect inflammation in the gut or even get into the bloodstream, where they can influence the immune system all over the body,” he added. “All of this is speculative at this point, but if it turns out that there is a causal link, we can start thinking about whether promoting ‘good’ bacteria or getting rid of ‘bad’ bacteria could slow down or even stop the development of symptomatic Alzheimer’s disease.”

Most people have some “bad,” or pathogenic, bacteria in their guts, and scientists are trying to figure out what an ideal microbiome is.

Research suggests eating probiotics regularly helps establish a healthier bacterial balance. Probiotics, found in food and supplements, are health-promoting bacteria.

Harvard Health Publishing pointed to two promising studies: one showing that milk with four probiotic strains may help improve cognitive scores in Alzheimer’s patients and one indicating that yogurt consumption helped women react more calmly to irritating stimuli.