Gut Microbial Dysbiosis Progresses from Health to Genetic Risk to Clinical Parkinson’s Disease, Correlating with Disease Severity

A new study published in Nature Medicine reveals that changes in the gut microbiome can identify individuals at risk of developing Parkinson’s disease, including those with genetic predispositions who have not yet shown symptoms.

The research, led by scientists analyzing fecal metagenomics data from 271 patients with Parkinson’s disease, 43 carriers of GBA1 gene variants who do not yet have symptoms (GBA-NMC) and 150 healthy controls, found that approximately 25% of the gut microbiome in genetically at-risk individuals shows an intermediate state between healthy controls and those with clinically diagnosed Parkinson’s disease.

Progressive Changes in Gut Microbiome Linked to Disease Risk

The study demonstrates that microbial changes in the gut evolve progressively: from healthy individuals to those genetically at risk due to GBA1 variants, and finally to patients with clinically evident Parkinson’s disease. This gradient of dysbiosis correlates with disease progression and can detect early signs of neurodegeneration even before motor symptoms appear.

Validation Across Independent Cohorts

To confirm the robustness of their findings, researchers validated the microbiome signature in three independent cohorts from the United States, Korea, and Turkey, encompassing a total of 638 Parkinson’s disease patients and 319 healthy controls. The consistency across geographically diverse populations strengthens the potential of gut microbial alterations as a biomarker for Parkinson’s risk.

Implications for Early Detection and the ‘Body-First’ Model

The results support the “body-first” hypothesis of Parkinson’s disease, which proposes that the condition may originate in the enteric and autonomic nervous systems before spreading to the brain. According to the study authors, alterations in the gut microbiome can identify individuals with both genetic and non-genetic risk factors who may be progressing toward Parkinson’s disease, offering a potential tool for early intervention in the premanifest phase.

One of the most significant genetic risk factors for Parkinson’s disease is carrying variants of the GBA1 gene, which increases susceptibility up to 30-fold. However, only about 20% of GBA1 variant carriers go on to develop the disease. The identification of a microbiome signature in asymptomatic carriers provides insight into why some individuals with the genetic risk remain healthy while others progress to clinical illness.

The study was published online in Nature Medicine on April 20, 2026, under the title “Microbiome signature of Parkinson’s disease in healthy and genetically at-risk individuals.”