Parkinson's is an insidious disease, and by the time most people are diagnosed due to motor problems such as tremors, portions of the brain have already been destroyed.

Earlier diagnosis could lead to better treatments, and researchers at the University of Luxembourg may have found a key. They have shown that bacteria in the guts of Parkinson's patients are very different from that of healthy people even at very early stages of the disease.

Experts have long suspected that Parkinson's disease originates far outside the brain. According to the "dual hit" hypothesis, an unknown pathogen invades into the body through two ports of entry: the nose or the gastrointestinal tract.

Once established, the pathogen starts a process that causes misfolding of the protein alpha-synuclein. Although the protein's exact function remains unknown, it is believed to be involved in the flow of messenger chemicals such as dopamine.

The misfolding of this protein could spread through the nerve pathways, where — decades later — it produces the typical clumping in the dopaminergic cells, known as Lewy bodies, that are characteristic of Parkinson's. Ultimately, nerve cells start to die off causing the typical symptoms of Parkinson's disease.

Scientists took samples from the nose and gut of 76 Parkinson's patients and 78 healthy control people who are taking part in a long-term study. They also examined the microbiome of 21 subjects diagnosed with iRBD or Idiopathic Rapid-Eye-Movement Sleep Behavior Disorder. People with this sleep disorder have a substantial risk of developing Parkinson's disease later in life.

The researchers discovered that the bacterial community of the gut differed considerably between all three groups, although there were no differences in the samples from the subjects' nasal cavities. "Parkinson's patients could be differentiated from healthy controls by their respective gut bacteria," said Dr. Anna Heintz-Buschart. The majority of the bacteria that was different in the Parkinson's patients showed similar trends in the iRBD group.

"We hope that, by comparing the groups, we will learn to better understand the role of the microbiome in the process of the disease and to find out what changes occur and when," said researcher Paul Wilmes.

"This might deliver new starting points for early treatment of the disease," he said. "It would also be essential knowledge for one day being able to use the absence or presence of certain bacteria as a biomarker for early detection of the disease."

Study results were published in the scientific journal Movement Disorders.

Up to 1 million Americans suffer from Parkinson's disease, and 60,000 new cases are diagnosed every year.

A recent multinational study found that regular exercise can slow progression of Parkinson's disease. The study, which was published in the Journal of Parkinson's Disease, found that people who exercised for 150 minutes a week showed a significantly smaller decline in mobility and quality of life than those who exercised less or didn't exercise at all, even if they only started exercising after being diagnosed with Parkinson's.