The worldwide team of scientists reviewed two datasets, including a large registry from Sweden, and found that removal of the appendix was associated with a decreased risk of developing Parkinson's disease.
Using health registries in Sweden covering some 1.7 million people followed for 50 years, and a second U.S. dataset encompassing 849 people, researchers found that those who had their appendix removed in early adulthood generally saw their risk of developing Parkinson's disease cut by 19 per cent, said the study in the journal Science Translational Medicine.
Why? "The hallmark pathology of Parkinson's disease in the brain is Lewy bodies, which is characterized by a clumped form of a protein called alpha-synuclein", Labrie explained.
Knowing that people with Parkinson's also suffer from gastrointestinal disorders like constipation at least 10 years before the disease's better known symptoms like tremors, stiffness, and poor balance surface, researchers made a decision to take a closer look at the appendix and its potential role. Researchers say that Parkinson's is more prevalent in rural areas due to increased exposure to pesticides.
So, "we think that if in rare events [such protein clumps] were to escape the appendix and enter the brain, this could lead to Parkinson's disease." How? The chemical structure of the protein found in the appendix of a Parkinson's patient was found to be different from what was found in healthy persons, the researchers noted. If Parkinson's can be caught early on, it might be possible to block the alpha synuclein from ever moving from the gut to the brain, forestalling brain damage.
What's more, after honing in on the specific experiences of about 850 Parkinson's patients, the researchers determined that appendix removal was also associated with a 3.6-year delay in the onset of Parkinson's among those who had the surgery and still developed the disease.
Like this story? Share it with a friend!James Beck, chief scientist at the Parkinson's Foundation, tells Susan Scutti at CNN that even if the disease might start in the gut, surgery is not the answer.
Claire Bale, head of research at Parkinson's United Kingdom, said the findings "build on previous research indicating that, for some, Parkinson's starts in the gut".
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"It plays into this whole booming field of whether Parkinson's possibly starts in the gut", Per Borghammer, a neuroscientist at Aarhus University in Denmark who was not involved in the study, tells Science.
Given the appendix's potential role in maintaining the gut microbiome as well as in the immune system, perhaps there's actually some link between fluctuations in the microbiome or inflammation and Parkinson's as well, said Labrie.
In addition, the researchers only looked at the appendix in this study, but there could be other places in the GI tract that also have these clumps "that we just haven't looked at yet", Labrie said.
"This knowledge will be invaluable as we explore new prevention and treatment strategies".
Moreover, the human appendix appeared to be a reservoir for alpha-synuclein aggregates in healthy people, even at young ages, according to Viviane Labrie, PhD, of the Van Andel Research Institute in Grand Rapids, Michigan, and colleagues in a study published inScience Translational Medicine.
The study, which looked at data on 1.7 million people over half a century, says that the appendix contains toxic proteins that are also found in the brains of Parkinson's sufferers.
This often includes constipation and the need to urinate frequently, and the issues can predate a Parkinson's diagnosis by many years.
The condition remains poorly understood and has no effective treatment. All they had to do was compare people who still had appendixes to those without them and see if rates of Parkinson's changed.
But decades of research suggest there has to be more to this accumulation than genes alone, with interactions between the brain and gut looking increasingly suspicious.