Between 8% and 20% of old man who for some reason need hospitalization have episodes of delirium, an acute and generally reversible disturbance of consciousness and cognition. In these cases, the person becomes disoriented, with a disconnected speech and it is common that he does not recognize his loved ones. This is a different picture from delirium – as hallucinations caused by mental illness are popularly known – and an important sign that the brain of the elderly is suffering.
In investigation of biomarkers that help diagnose the problem and also therapeutic targets, researchers from USP (University of São Paulo) analyzed the intestinal microbiota of 133 patients over 65 years hospitalized at HC (Hospital das Clínicas) in FM- USP (Faculty). in Medicine). The survey results were reported in The Journals of Gerontology.
“We identified that the elderly with a less diverse microbiota were at greater risk of developing dementia. And that the patients who actually developed the condition carried a greater number of enterobacteria – microorganisms associated with pro- inflammatory and modulation of important neurotransmitters”, says Flávia Garcez, first author of the article. The doctor collaborates with the research activities of the HC-FM-USP Geriatrics Service and received, in 2019, the Nidus Junior Investigator Award, which provides funding for research on delirium.
The work with elderly people hospitalized at Hospital das Clínicas is part of a larger project, supported by Fapesp, which investigates diagnostic and prognostic markers in critically ill patients treated in an emergency service.
“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 nonetheless, little was known about the relationship between microbiota and delirium, a disease that, although very prevalent, is still full of mystery”, 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, and one influences the other. “There is the brain-gut axis, connected by the vagus nerve, which serves as a bidirectional communication between the gastrointestinal tract and the brain. In addition, previous studies have already demonstrated the relationship between microbiota and a sister disease of delirium, Alzheimer’s.”, said the researcher.
nonetheless, he points out that the work is advanced in understanding this relationship. “The interesting thing about this study is that we were able to evaluate the microbiota of the same person repeatedly, before and after he had delirium. With this, we found the factor that the range of microorganisms in the intestinal tract changes when the same patient enters and leaves the delirium”, he pointed out.
For the study, the researchers collected sociodemographic, clinical and laboratory data throughout the hospitalization period. The intestinal microbiota was analyzed in the samples obtained by rectal swab (a type of cotton swab passed in the region of the anus) right of 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 confounding assessment method (CAM) to assess, twice a day, the presence of the disease during hospitalization.
Candidates who, up to 24 hours before hospital admission, used probiotics, prebiotics or artificial nutrition, as well as those with acute gastrointestinal diseases, severe traumatic brain injury, history of recent hospitalization or institutions, were excluded from analysis there.
In addition to analyzing the microbiota, the group also investigated factors related to inflammation, such as circulating levels of cytokines – molecules that signal the immune system that it needs to send more defense cells to the site of infection. nonetheless, no significant differences were found between patients who did or did not have delirium.
“Delirium is the most common neuropsychiatric change 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. To 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 medical course at FOB-USP (The Faculty Dentistry of Bauru) 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 changes in consciousness or dementia, dehydration and abuse of alcohol and other drugs. “In addition, there is likely to be an element linked to the stress that hospitalization 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, nonetheless, the expectation is that for delirium they find several markers instead of just one. “As many factors can cause this disease, it is possible that there are different triggers”, he assessed.