An observational study in Mild Cognitive Impairment, Alzheimer Disease (AD) and Dementia, sponsored by University of South Florida. Recruiting at 1 site in United States. Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-21.
Sponsored by University of South Florida · Observational
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.
The Microbiome in Aging Gut and Brain (MiaGB) Study is a multisite observational study investigating relationships among the gut and oral microbiome, cognitive function, microbial metabolites, intestinal permeability, inflammation, and other biological characteristics associated with aging and cognitive impairment.
The study consists of two interconnected phases.
Phase 1 is a baseline cross-sectional assessment. A total of 700 participants are planned, including 100 young healthy adults, 300 cognitively healthy older adults, 200 older adults with mild cognitive impairment (MCI), and 100 older adults with Alzheimer's disease or related dementia. Baseline assessments include demographic and medical history information, cognitive function, dietary information, and selected physical function assessments. Biological samples may include stool, oral swabs, saliva, blood, and urine.
Laboratory analyses may include characterization of the gut and oral microbiome, metabolomics, markers of intestinal permeability and inflammation, proteomics, transcriptomics, genetic analyses, mitochondrial function, immunophenotyping, and other protocol-specified biological assessments. These data will be examined to determine whether microbial and biological patterns differ among participants with different levels of cognitive function.
Phase 2 is a prospective longitudinal follow-up. Young healthy adults, cognitively healthy older adults, and participants with MCI will be reassessed approximately annually for up to 5 years. Longitudinal assessments will be used to evaluate whether changes in the microbiome and related biological measures are associated with changes in cognitive function and whether these measures may help identify individuals at increased risk of cognitive decline. Participants with Alzheimer's disease or related dementia will undergo baseline assessment only and will not participate in the 5-year longitudinal follow-up.
This is an observational study. Participants are not assigned to a drug, biological product, behavioral treatment, or other research intervention.
3,872 studies on the registry are indexed under Cognitive Dysfunction; 1,119 are open to participants now.
This study's planned enrollment of 700 is above the median of 150 across 997 observational studies indexed under Cognitive Dysfunction.
Browse Cognitive Dysfunction studies →University of South Florida is the lead sponsor of 340 studies on the registry; 65 are open to participants now.
Of its 17 completed or terminated interventional studies of FDA-regulated products, 4 (24%) have results posted.
Counted across the registry records on this site, refreshed daily.
The study population includes young healthy adults aged 18-60 years and adults aged 60 years and older who are cognitively healthy or have mild cognitive impairment (MCI) or Alzheimer's disease/related dementia. Participants are recruited from participating clinical sites, memory and behavioral health clinics, senior living communities, and the community. The planned enrollment is 700 participants: 100 young healthy adults, 300 cognitively healthy older adults, 200 participants with MCI, and 100 participants with Alzheimer's disease/related dementia.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Healthy adults aged 18-60 years with normal cognitive function. Participants undergo baseline assessments and annual follow-up for up to 5 years.
Adults aged 60 years and older with normal cognitive function. Participants undergo baseline assessments and annual follow-up for up to 5 years.
Adults aged 60 years and older with mild cognitive impairment. Participants undergo baseline assessments and annual follow-up for up to 5 years.
Adults aged 60 years and older with Alzheimer's disease or Alzheimer's disease-related dementia. Participants undergo baseline assessment only and are not included in the 5-year longitudinal follow-up.
Gut Microbiome Shannon Diversity Index
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.
Time frame: Baseline for all participants and annually for up to 5 years for longitudinally followed participants
Montreal Cognitive Assessment (MoCA) Score
Cognitive function will be assessed using the Montreal Cognitive Assessment (MoCA). MoCA scores will be assessed at baseline across the study groups. Young healthy adults, cognitively healthy older adults, and participants with mild cognitive impairment (MCI) will also be assessed annually to evaluate longitudinal changes in cognitive function. Participants with Alzheimer's disease/dementia will undergo baseline assessment only.
Time frame: Baseline for all participants and annually for up to 5 years for longitudinally followed participants
Plan to share: Yes — De-identified individual participant data may be shared, including demographic characteristics, vital and anthropometric measures, dietary information, cognitive and physical function outcomes, and data associated with collected biological specimens, including oral swab, saliva, stool, urine, and blood samples. Direct identifiers and protected health information (PHI) will not be shared. Data sharing will be conducted in accordance with participant consent, applicable IRB approvals, and NIH data-sharing requirements.
Time frame: De-identified individual participant data will be considered for sharing after completion of the relevant analyses and publication of the primary study findings. The duration of availability will be governed by applicable NIH repository, institutional, and regulatory requirements.
Access criteria: Qualified researchers may be provided access to de-identified individual participant data through an applicable NIH data repository or other approved data-sharing mechanism. Access will be subject to applicable repository requirements, participant consent, institutional policies, and IRB approval, as appropriate. Direct identifiers and protected health information will not be shared.
Started Sep 2021 (actual). Primary completion is estimated for Sep 2031, 120 months after the start.
Of 504 non-industry observational studies under Cognitive Dysfunction, half reached primary completion within 49 months of starting (the median), counting those still running; a quarter within 22 and three quarters within 118. This study's planned 120 months is above that.
Counting every sponsor, half of 543 studies reached it within 47 months; a quarter within 21 and three quarters within 118.
How these figures are worked out, and which studies are left out of them.
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