Whether the same association exists for younger patients — ages 59 or younger — remains to be determined, according to the researchers.
The study, “Older patients with IBD might have higher risk of Parkinson’s disease,” was published in the journal Gut.
The chronic activation of pro-inflammatory mechanisms, which occurs in autoimmune conditions, has been increasingly recognized as a critical contributor of neurodegenerative disorders.
Studies suggest that this may happen due to the “gut-brain axis” — the two-way communication between the nervous system and the intestine that monitors gut function and links certain regions of the brain to intestinal functions, such as immune activation or intestinal permeability.
In line with the findings, some studies have already reported that patients with IBD — an autoimmune condition characterized by chronic inflammation of the gut — are 22-41% more likely to develop Parkinson’s than those without IBD.
However, a case-control study that examined Medicare data from 89,790 Parkinson’s cases and 118,095 population-based controls suggested that IBD actually reduced the risk for Parkinson’s by 15%.
To clarify this association, a team at Sichuan University in China reviewed all studies investigating the link between IBD and risk of Parkinson’s. Five studies met the inclusion criteria defined by the team, including a total of 9,174,766 participants.
Overall, IBD patients did not have a significantly higher risk of Parkinson’s than reference individuals, nor did patients with ulcerative colitis or Crohn’s disease — the two main forms of IBD — when examined individually.
However, patients 60 years or older were found to have a 32% higher risk of developing Parkinson’s. Patients 50 years or younger did not show this association, the researchers said.
“Our meta-analysis showed that patients with IBD did not have an increased risk of PD; however, subgroup analysis with cohort studies showed that they might be associated with increased risk of PD,” the researchers wrote.
“Age has been regarded as an important risk factor for Parkinson’s disease,” they added, but the findings suggest that “age at IBD diagnosis might be a risk factor of Parkinson’s disease.”
Interestingly, the team found that some studies reported medication-related side effects in the IBD population that resembled parkinsonism in the older population.
“It is necessary to take it into consideration whether older people will take more medications, and whether these medications lead to a higher risk of Parkinson’s also needs further studies to verify in the future,” they said.
Additional well-designed observational studies are still warranted to further explore the risk of Parkinson’s disease within the younger IBD population, the team noted.