Parkinson's disease has long been considered a brain disease, but several studies indicate the role of the digestive system. In a study published on Wednesday in the United States, the small body considered an unnecessary addition is particularly interested.
The authors of this study, based on medical data of 1.7 million Swedes for about half a century, found that those who had an appendix removed early in life had a risk of developing Parkinson's disease is reduced by 19%. The effect seems to be specific to the Swedes living in rural areas. For them, the risk is reduced by 25%, while the risk reduction can not be observed in urban areas.
As for those who developed Parkinson's disease, the researchers found that appendectomy (removal of the appendix) was associated with a later onset of an average of three and a half years, said lead author Viviane Labrie, from the Van Andel Research Institute in Michigan, during a conference call with the press on Tuesday.
"Our work suggests that the supplement may play a role in the onset of Parkinson's disease," she explained, noting that this role was probably not exclusive.
Patients with Parkinson's also suffer from gastrointestinal problems such as constipation, a decade or longer before symptoms such as tremor and other motor problems. This prompted the scientific community to become interested in the role of the digestive system.
The supplement is the storage site for intestinal bacteria and also seems to play a role in the immune response. It is also a "reservoir" of key protein in Parkinson's disease, called alpha-synuclein, especially in an abnormal form.
But this protein is abundant in addition to all, sick or not. This suggests to the researchers that the abnormal protein sometimes manages to escape from the appendages to the brain, where it can cause damage.
"This protein does not like to stay in one place," said Viviane Labrie. "It moves from a neuron to a neuron."
And just the nerve, the vagus nerve, connects the digestive tract with the brain. Experiments have shown that the protein is able to follow this path.
"If it enters the brain, it can turn on and develop until it triggers the neurotoxic effects that can lead to Parkinson's disease," says the scientist.
The authors of the study warned the press that everyone should not be advised to remove the supplement. "We're not saying that if you had the removal, you will not have Parkinson's disease," warns Viviane Labrie.
But this work is another indication of the role of a small organ that can one day lead to therapy to neutralize this reservoir.
At present, no causal relationship has been established. As with this type of research, many factors that have not been taken into account can explain the difference between those who have been ablated and others.