Study associates intestinal microbiota and delirium in the elderly – 09/08/2023 – Science

Between 8% and 20% of the elderly who for some reason need to be hospitalized have episodes of delirium, an acute and generally reversible disorder of consciousness and cognition.

In these cases, the individual becomes disoriented, with a disconnected speech and it is common that he does not recognize loved ones. This is a different picture from delirium –as hallucinations caused by mental illness are popularly known– and an important sign that the elderly’s brain is suffering.

In search of biomarkers that help diagnose the problem and also therapeutic targets, researchers from the University of São Paulo (USP) analyzed the intestinal microbiota of 133 patients over 65 years of age hospitalized at the Hospital das Clínicas (HC) of the Faculty of Medicine (FM -USP). The results of the survey were published in The Journals of Gerontology.

“We identified that elderly people with a less diverse microbiota were more likely to develop delirium. And that patients who actually developed the condition carried a greater amount of enterobacteria – microorganisms associated with pro-inflammatory pathways and the modulation of important neurotransmitters”, he says. Flávia Garcez, first author of the article.

The doctor collaborates with the research activities of the Geriatrics Service of HC-FM-USP and received, in 2019, the award NIDUS Junior Investigator Awardwhich provides funding for research on delirium.

The work with the elderly hospitalized at the Hospital das Clínicas is part of a larger project, supported by Fapesp, which investigates diagnostic and prognostic markers in critically ill patients treated at an emergency service.

“The gut microbiota has gained attention in recent years. It has been linked to several conditions, such as obesity, insulin resistance and inflammatory bowel disease. Disturbances in the microbiota have also been linked to chronic neuropsychiatric diseases, such as depression and Alzheimer’s disease. No However, little was known about the relationship between microbiota and delirium, a disorder that, although very prevalent, is still full of mysteries”, says Heraldo Possolo de Souza, coordinator of the study supported by FAPESP.

brain-gut axis

According to Garcez, the association between microbiota and delirium was already expected and the work showed that this relationship is possibly bidirectional, with one influencing the other.

“There is the brain-intestine axis, connected by the vagus nerve that serves as a bidirectional communication between the gastrointestinal tract and the brain. Apart from that, previous studies had already demonstrated the relationship between the microbiota and a disease that is the sister of delirium, Alzheimer’s”, he says. the researcher.

However, she emphasizes, the work advanced in the understanding of this relationship. “The interesting thing about this study is that we were able to evaluate the microbiota of the same individual repeatedly, before and after he had delirium. With that, we found that the set of microorganisms in the intestinal tract changed when the same patient entered and left delirium”, highlights.

For the research, sociodemographic, clinical and laboratory data were collected throughout the hospitalization period. The intestinal microbiota was analyzed from samples obtained by rectal swabs (a kind of cotton swab that is passed in the anus region) right on admission and 72 hours after the patients were admitted to the hospital.

A third sample was collected as soon as the volunteer had delirium. The group used the Confusion Assessment Method (CAM) to assess, twice a day, the presence of the disorder during hospitalization.

Candidates who, up to 24 hours before hospital admission, used probiotics, prebiotics or artificial nutrition, as well as those with acute gastrointestinal disorders, severe traumatic brain injury, history of recent hospitalization or institutionalization, were excluded from the analysis.

In addition to analyzing the microbiota, the group also investigated factors related to inflammation, such as the circulating level of cytokines – molecules that signal to the immune system the need to send more defense cells to the site of infection. However, no significant differences were found between patients who had or did not have delirium.

“Delirium is the most common neuropsychiatric alteration in hospitalized patients and can be defined as the brain suffering. That is why it is so important to advance in the investigation and identify markers. When talking about renal failure, there is a blood test. For respiratory failure , it is possible to see the patient with shortness of breath. But for cerebral insufficiency, such as delirium, there is still no definitive marker”, explains Júlio César Garcia de Alencar, professor of the Medicine course at the Faculty of Dentistry of Bauru (FOB- USP) and co-author of the study.

Alencar points out that patients with delirium are twice as likely to die. And that the known predisposing factors are: male gender, previous alteration of consciousness or dementia, dehydration and abuse of alcohol and other drugs. “In addition, it is likely that there is a component linked to the stress that the hospital causes.”

It is worth noting that the risk factors for delirium are the same as for dysbiosis, a clinical condition characterized by an imbalance between beneficial and pathogenic bacteria in the digestive tract.

For Garcez, however, the expectation is that for delirium several markers are found instead of just one. “As many factors can cause this disorder, it is possible that there are different triggers”, he assesses.

The study Association Between Gut Microbiota and Delirium in Acutely Ill Older Adults can be read here.