EDITOR’S NOTE: Since this article was published, additional research has been conducted that challenge the results of this study. Continued research is needed to understand the connection between the appendix and Parkinson’s disease.
A study published in October 2018 suggests that people who have had their appendix removed are 19-25% less likely to develop Parkinson’s disease (PD). Researchers looking for a connection between the appendix and PD analyzed medical data from 1.6 million people in Sweden. They also looked specifically at those with PD and found that an appendectomy was associated with a delayed onset of the disease by an average of 3.6 years.1,2
What does the appendix have to do with Parkinson’s?
The appendix is a small organ attached at the end of the large intestine. Some people develop appendicitis, which requires urgent surgery to remove the organ. While in the past the appendix was viewed as largely unnecessary, doctors now believe it plays an important role in our immune system with the colony of bacteria that are a normal part of our bodies.1
The connection between Parkinson’s and the intestines has been an area of research for some time. Previous research has found that people with PD can have gastrointestinal symptoms up to 20 years before movement symptoms. Aggregates, or clumps, of the alpha-synuclein protein, which is found in the brain in people with PD, can also be found in the gut. Some researchers have suggested that the clumps of alpha-synuclein travel from nerve cell to nerve cell, from the gut up to the brain. This new study suggests that if the clumps of alpha-synuclein are removed with the appendix before they spread, the development of PD may be slowed or stopped.1,2
Findings from the study
The recent study included two data sets: the nationwide Swedish National Patient Registry (SNPR) and the Parkinson’s Progression Markers Initiative (PPMI), which included 1,698,000 individuals followed over several decades. In the individuals who had an appendectomy, the risk of PD was 19.3% lower. The risk was even greater in people who lived in rural communities: those living in rural areas who had an appendectomy had a 25.4% reduced risk of PD. This is significant because PD is often more prevalent in rural communities, where the increased use of pesticides is thought to be a factor.1,3
Appendectomy did not seem to reduce the risk of PD in people with a family history of the disease. Although family members may share both genetic and environmental risk factors, those with a known genetic mutation did not benefit from having their appendix removed.3
A closer look
Looking at the data from the PPMI from individuals who have Parkinson’s, the appendectomy surgery seemed to delay the onset of the disease, on average, by 3.6 years in those who had an appendectomy at least 30 years before their diagnosis of PD. Once the individuals had developed PD, there was no difference in the severity of symptoms between those who had an appendectomy and those who hadn’t.3
The researchers also found that clumps of alpha-synuclein were present in nearly all the appendix samples – both those who later developed PD and those who did not. Aggregates of alpha-synuclein were also found across the age spectrum, in young (under 20 years old) and older (aged 48-84) individuals. This indicates that the presence of these protein clumps in the appendix is not a singular cause of PD. Other factors must also play a role in the disease.1,3
Limitations of the research
While the findings from the Swedish study are compelling, it’s too early to suggest using appendectomy as a preventive measure for PD. Some critics have noted that people who have had their appendix removed may also share other similarities that may account for their reduced risk of PD, and that it’s impossible to determine cause-and-effect from this one study.2
Regardless, the study provides additional clues to the development – and potential prevention – of PD and supports the idea that the disease may begin in the intestines in at least some people.
Appendix identified as a potential starting point for Parkinson’s disease. Science Daily. Available at https://www.sciencedaily.com/releases/2018/10/181031141606.htm. Accessed 11/19/18.
Scutti S. Had your appendix removed? Your Parkinson’s risk may be 20% lower. Available at https://www.cnn.com/2018/10/31/health/appendectomy-parkinsons-disease-study/index.html. Accessed 11/19/18.
Killinger BA, Madaj Z, Sikora JW, et al. The vermiform appendix impacts the risk of developing Parkinson’s disease. Science Translational Medicine. 2018 Oct; 10(465): eaar5280. DOI: 10.1126/scitranslmed.aar5280