NCT07799402 · University of South Florida
Microbiome in Aging of Gut and Brain
(MiaGB)
What this study is about
The Microbiome in Aging Gut and Brain (MiaGB) Study is an observational study designed to examine whether differences in the microorganisms living in the gut and mouth are associated with cognitive health and cognitive decline.
View original scientific description
The Microbiome in Aging Gut and Brain (MiaGB) Study is an observational study designed to examine whether differences in the microorganisms living in the gut and mouth are associated with cognitive health and cognitive decline. The study includes young healthy adults, cognitively healthy older adults, older adults with mild cognitive impairment (MCI), and older adults with Alzheimer's disease or related dementia. At the baseline visit, participants complete assessments of medical history, cognitive function, physical function, and diet and provide biological samples that may include stool, saliva, oral swabs, blood, and urine. Researchers will study the gut and oral microbiome and related biological factors, including metabolites and markers of intestinal permeability and inflammation, to determine whether these measures differ according to cognitive status. Young healthy adults, cognitively healthy older adults, and participants with MCI will be followed annually for up to 5 years to evaluate changes in the microbiome and cognitive function over time. Participants with Alzheimer's disease or related dementia will participate in the baseline assessment only. No drug, treatment, or other research intervention is assigned as part of this study.
Primary outcome measures
Gut Microbiome Shannon Diversity Index
Time frame: Baseline for all participants and annually for up to 5 years for longitudinally followed participants
Gut microbiome alpha diversity will be quantified from stool samples using the Shannon diversity index. At baseline, Shannon diversity will be assessed across young healthy adults, cognitively healthy older adults, participants with mild cognitive impairment (MCI), and participants with Alzheimer's disease/dementia. Young healthy adults, cognitively healthy older adults, and participants with MCI will also be assessed annually to evaluate longitudinal changes in gut microbiome diversity. Participants with Alzheimer's disease/dementia will undergo baseline assessment only.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Age 18-60 years for young healthy participants, or age 60 years and older for older adult participants. Participants meeting one of the following cognitive categories: Normal cognitive function Mild cognitive impairment (MCI) Alzheimer's disease or Alzheimer's disease-related dementia Able to participate in the informed consent process as applicable. For participants unable to provide informed consent because of cognitive impairment, consent may be obtained from a legally authorized representative (LAR) according to the approved protocol.
Exclusion criteria
- History of brain or gastrointestinal surgery within the past 5 years. History of cancer and/or cancer treatment within the past 5 years, except non-melanoma skin cancer. History of systemic cancer treatment within the past 5 years. Neurological disorders including epilepsy, Parkinson's disease, or amyotrophic lateral sclerosis. Antibiotic use within the past 30 days. Diarrhea, vomiting, and/or food poisoning within the past 30 days. History of inflammatory bowel disease. Body mass index (BMI) greater than 45 kg/m² or less than 18 kg/m². Weight loss of more than 10 pounds within the past 2 weeks.
Where
- Tampa, Florida
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Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Sep 21, 2026 · Source of record for eligibility and locations