Changes that occur in the brain cells of Parkinson’s disease patients also impact nerve cells in the spinal cord and the intestinal wall. This can lead to unpleasant symptoms in the gastrointestinal tract such as constipation and irritable bowel syndrome.
But could this process actually occur in reverse? Could the gut act as the starting point for the neurological disease which then spreads towards the central nervous system?
Scientists set up a study to see if this was conceivable and had a surprise finding along the way.
The idea that Parkinson’s starts in the gut is not new. It was first proposed twenty years ago by Heiko Braak from Germany. He suggested the protein alpha-synuclein, which misfolds and forms clumps called Lewy bodies in the brains of Parkinson’s patients, spreads from the gut to the brain via the vagus nerve.
Mr. Braak’s hypothesis has been confirmed in mice but in humans this could take many years. Meanwhile, scientists from the Mayo Clinic, Johns Hopkins and experts from Belgium set up an observational study to see if gut problems routinely occur before the onset of Parkinson’s symptoms.
Three Gut Problems Double Parkinson’s Risk
For the study the research team analyzed medical records of 24,624 Americans with Parkinson’s disease and compared them to similar numbers of patients with Alzheimer’s disease, cerebrovascular disease (brain bleeds/clots) and healthy people.
All four groups were similar in terms of age, gender, race, ethnicity, and time since diagnosis in those with neurological conditions.
Then the researchers compared the frequency of gut conditions starting about six years before patients received a Parkinson’s diagnosis. The investigators also looked at it from another angle. They analyzed people diagnosed with any one of 18 gut conditions, matched them to others without these conditions and then found out which of them went on to develop Parkinson’s or the other neurological conditions over the following five years.
The results, published in the journal Gut in August, showed that Parkinson’s patients were more likely to have gut problems before diagnosis, and people with gut problems had a higher chance of developing Parkinson’s.
But of the 18 conditions only four proved significant:
- Dysphagia (difficulty swallowing)
- Gastroparesis (delayed stomach emptying)
- Irritable bowel syndrome with diarrhea
The first three more than doubled the risk of Parkinson’s while IBS increased the risk by 17 percent.
The study authors explained, saying, “This study is the first to establish substantial observational evidence that the clinical diagnosis of [these gut conditions] might specifically predict the development of Parkinson’s disease.”
Other gut issues also noted to be more prevalent before onset in all three neurological groups were functional dyspepsia (burning sensation or fullness of the stomach with no obvious cause), IBS with diarrhea, and diarrhea with fecal incontinence.
There’s also another gut factor that’s of increasing interest.
The Influence of The Appendix
The scientists were reported to be “surprised to learn” that those who had had their appendix removed saw their relative risk of developing the disease drop by 52 percent.
Dr. Tim Bartels, group leader at the UK Dementia Research Institute at University College London, explained, saying, “An interesting side point of the study is the seemingly protective association of appendectomy with Parkinson’s disease, implying in addition that the appendix might be the origin of the pathological insult that spreads through the gut and ultimately to the brain.”
His view is backed up by scientists writing in the Journal of Parkinson’s Disease in 2019. “[T]he molecular events leading to Parkinson’s disease and the mechanisms by which alpha-synuclein aggregates transfer from gut to brain may be identifiable in the human appendix.”
Scientists have been reviewing the function of the appendix in recent years and report that it “serves as an immune tissue in the gut that is also capable of regulating the intestinal microbiome.” They now believe the appendix may contribute to initiating Parkinson’s disease because, in both sick and healthy humans, the appendix is home to an abundance of alpha-synuclein clusters.
In one study, researchers detected Lewy pathology in the gastrointestinal tract of patients, including the appendix, up to 20 years before these patients were diagnosed with Parkinson’s. In another, researchers followed 1,698,000 individuals for up to 52 years comparing those who had their appendix removed with those that didn’t. They found the overall risk of developing Parkinson’s was significantly decreased by 19.3 percent among those who had an appendectomy (removal of the appendix).
I’m not surprised by these findings. We’ve reported repeatedly on the importance of the gut microbiome to maintaining a sharp memory. Of course, research into the gut-brain axis is still in its infancy, but we’re following along closely and will report back on any new findings.
The Awakening From Alzheimer’s Team