The research, “Inflammatory bowel disease increases the risk of Parkinson’s disease: a Danish nationwide cohort study 1977–2014,” was published in the journal Gut.
Inflammation plays a key role in the development of Parkinson’s and multiple system atrophy (MSA), two conditions that belong to the “parkinsonism” group of disorders and cause motor problems such as tremors, slow movement and stiffness.
Both Parkinson’s and MSA patients have aggregates of the protein alpha-synuclein in the brain.
IBD is a chronic condition mainly characterized by inflammation of the gut. In fact, chronic inflammatory immune activity is increasingly being recognized as a fundamental element of neurodegenerative disorders, and in Parkinson’s, inflammation in the intestine may reflect the earliest symptom of the disease.
This may occur due to the so-called “gut-brain axis”, a system that incorporates two-way communication between the nervous and endocrine (hormonal) systems and regulates immune responses in the gut and brain. All aspects of this system appear to be heavily influenced by the activity of intestinal microbes.
Previous research has indicated that the LRKK2 gene, the greatest genetic contributor to Parkinson’s disease and a regulator of inflammation and alpha-synuclein clearance, also is associated with Crohn’s disease, one of the two most common forms of IBD.
To provide “real-life” evidence of the link between IBD and the risk of Parkinson’s and MSA, Danish researchers conducted a nationwide study involving all 76,477 patients diagnosed with IBD in Denmark from 1977 to 2014.
A total of 7.5 million non-IBD individuals from the general population were used as controls.
Individuals were followed from IBD diagnosis to the occurrence of Parkinson’s or MSA, using data from the Danish National Patient Register. This was the first epidemiological study assessing the risk of parkinsonism in a nationwide group of IBD patients with long-term follow-up, researchers noted.
Over the study duration, 335 IBD patients (0.4%) and 39,784 non-IBD individuals (0.5%) were diagnosed with Parkinson’s, while MSA was detected in 13 patients with IBD (0.02%) and 866 controls (0.01%).
Importantly, the results showed that patients with IBD had a 22% higher risk of developing Parkinson’s in comparison with non-IBD individuals, independent of age at IBD diagnosis, gender, or length of follow-up.
Although the incidence of MSA was low, results also showed a tendency toward higher risk in IBD patients compared to controls.
Specifically, the risk of developing Parkinson’s or MSA was 35% higher in patients with ulcerative colitis — another main type of IBD — but not in those with Crohn’s disease.
“The study suggests that clinicians should be aware of symptoms of parkinsonism in patients with IBD,” researchers wrote. They also underscored the need to further study the role of gut inflammation and the brain-gut axis in the development of Parkinson’s-related disorders.
As for potential treatment advances, the authors said that “the identification of risk factors associated with [early] phases of Parkinson’s disease may allow for early intervention studies that could modify or slow down disease progress.”