Mohammed Z. Sheriff, M.D.

People who have had an appendectomy are more than three times as likely to develop Parkinson’s disease as those who have not, according to the largest study to date to address the relationship between the two conditions.

“This research shows a clear relationship between the appendix, or appendix removal, and Parkinson’s disease, but it is only an association,” said Mohammed Z. Sheriff, M.D., the lead author of the study and a physician at Case Western Reserve University and University Hospitals, Cleveland. “Additional research is needed to confirm this connection and to better understand the mechanisms involved.”

For the retrospective study, investigators analyzed the electronic records of more than 62.2 million people from 26 health systems to identify those who had appendectomies and then a Parkinson’s disease diagnosis at least six months later.

They found that among 488,190 patients who had undergone appendectomies, Parkinson’s developed in 4,470, or 0.92%. Of the remaining 61.7 million patients without appendectomies, they identified only 177,230, or 0.29%, in whom the disease developed. The scientists found similar risk levels across all age groups, regardless of gender or race.

“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,” Sheriff said. “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.”