Could a breath test reveal Parkinson's risk?
NCT ID NCT07786116
First seen Aug 25, 2026 · Last updated Aug 26, 2026 · Updated 1 time
Summary
This study explores whether methane gas produced by gut microbes is linked to the progression of Parkinson's disease and related conditions like dementia. Researchers will measure breath methane levels in 200 adults—including those with Parkinson's, those at high risk (REM sleep behavior disorder), those with cognitive impairment, and healthy controls—and track changes over 18 months. A small sub-study will test whether a probiotic (Lactobacillus reuteri) can lower methane production in 15 people with Parkinson's. The goal is to understand if gut health influences brain disease progression.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- Probiotic supplementation with Lactobacillus reuteri
- What this could lead to
- If gut methane is linked to faster disease progression, this could point to a simple breath test for risk and open the door to probiotic-based therapies for Parkinson's and related conditions.
- What could go wrong
- This is an observational study with a small probiotic sub-study, so it can only show associations, not cause and effect. The probiotic part involves only 15 people, so any benefits would need much larger trials to confirm.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Not a phased trial
Phase numbers describe drug development. The registry uses this when they do not apply, as it does for trials of devices, procedures or behaviour changes, and for observational studies.
- Participants
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About 215 people
The number the study aims to enrol. It can still change while the study runs.
- Started
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Nov 2025
- Expected to finish
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Mar 2028
An estimate. End dates often move.
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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55 years and older
- Sex
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Anyone
- Healthy volunteers
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Accepted
You do not need to have the condition being studied to take part.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: People with PD: * 55 years of age or above; * MDS criteria for Idiopathic PD; * H\&Y\<3. People at high risk of developing PD (people with REM Sleep behaviour disorders): * 55 years of age or above; * RBD diagnosis confirmed by polysomnography. Other conditions affecting cognition (e.g. dementia, mild cognitive impairment): * 55 years of age or above; * Diagnosis of non-PD dementia or MCI, or, MoCA score ≤25 Healthy Controls: * 55 years of age or above * MoCA total score ≥26. Exclusion Criteria: * Presence of other neurological disorder, chronic inflammatory/autoimmune disorder, active cancer, active metabolic disease, diabetes type I and II, and active or latent infection; * Use of immunosuppressive drugs within the preceding 12 months; * Use of oral/intravenous steroids within the preceding 3 months; * Regular use (more than twice per week) of non-steroidal anti-inflammatory drugs (e.g. ibuprofen, naproxen, diclofenac, meloxicam) or over 75mg aspirin; * Participation in other interventional studies, within the preceding 3 months; * Consumption of laxatives, stool softeners, stool bulking agents, motility agents, iron supplements and probiotics within the preceding 3 months; * Current smoker * Inability to understand or speak English fluently. For participants in Component 2 of the study (Experimental Medicine Study), additional exclusion criteria will be in place, namely, known allergy to any of the probiotic's ingredients: Bulking agent (isomalt), sweetener (xylitol), L. reuteri DSM 17938, strawberry flavouring and flavour enhancer (citric acid).
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
How to take part
Only the study team decides who joins. These are the ways to reach them.
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The places running it
1 site. The list below names each one and where it is.
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The official record
ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.
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A doctor treating you
A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.
Contacts and locations
Locations
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John Van Geest Centre for Brain Repair - Forvie Site, Robinson Way
RECRUITINGCambridge, CB2, 0PY, United Kingdom
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