The Link Between The Appendix And Parkinson's Just Got Even More Confusing

Actor Michael J Fox was diagnosed with Parkinson's aged just 29. Krista Kennell/Shutterstock

Sorry, we have bad news for anyone who has had their appendix out – new research has linked appendectomies to Parkinson's. 

Indeed, according to a study due to be presented at this year's Digestive Disease Week (DDW), having your appendix removed can increase your risk of developing the condition by as much as 300 percent.

Not that long ago, the appendix was dismissed as junk tissue, an evolutionary throwback or vestigial organ. Its purpose was poorly understood. Its presence in the human body a scientific mystery. Charles Darwin himself suggested it was a legacy of an ancestor species, who needed an appendix to chow down on leafy snacks.

More recently, biologists have started to get to grips with the appendix and its place in human anatomy. The current understanding is that it serves as a form of "reservoir" or breeding ground for good bacteria of the gut, allowing it to repopulate when supplies deplete.

(Edited) diagram of the stomach and intestines, pointing to the appendix. design36/Shutterstock

It is this association with the gut that (potentially) links the appendix (or lack thereof) to Parkinson's disease, widely considered to be a neurodegenerative or motor system disorder. Like many other conditions – depression being one – new insights suggest it could be tied to specific strains of gut bacteria. In this case, a protein called alpha synuclein. 

"Recent research into the cause of Parkinson's has centered around alpha synuclein, a protein found in the gastrointestinal tract early in the onset of Parkinson's," lead author Mohammed Z. Sheriff, a physician at Case Western Reserve University and University Hospitals Cleveland Medical Center, Ohio, said in a statement. "This is why scientists around the world have been looking into the gastrointestinal tract, including the appendix, for evidence about the development of Parkinson's."

Sheriff's study is the largest of its kind so far, examining any possible correlation between the removal of the appendix and the development of Parkinson's. His team studied more than 62.2 million medical records, collated from 26 different health systems. 

The data revealed that of the 488,190 patients who had had their appendix removed, 4,470 (0.92 percent) were later diagnosed with Parkinson's. As for the remaining 61.7 million patients who did not, 177,230 (0.29 percent) developed the condition.

The good news here is that only a tiny fraction of either group went on to have Parkinson's and the team found no increased risk related to age, gender, or race. Yet, it does suggest that having an appendectomy more than triples your chances of developing the disease.

Still, it is worth remembering that this is a correlation, meaning it does not prove appendectomies cause Parkinson's. It is unclear at this stage exactly what the relationship between the two is.

It is also important to note that, as the author's mention themselves, previous studies have come back with conflicting results. Just last November, for instance, a study involving 1.6 million people found a negative correlation between appendectomies and Parkinson's. The researchers concluded that having the operation slashes your risk of developing Parkinson's by a fifth and that those who did start showing symptoms did so an average of 3.5 years later.

Referring to his research, Sheriff said it "shows a clear relationship between the appendix, or appendix removal, and Parkinson's disease, but it is only an association. Additional research is needed to confirm this connection and to better understand the mechanisms involved."

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