People with type 2 diabetes have an increased risk of developing Parkinson’s disease, based on an analysis of both genetic factors and real-world observational data published in the journal Movement Disorders.
Parkinson’s disease is a nervous system disorder that affects movement, causing symptoms like tremors, stiffness and slowed movement that tend to get worse the longer someone has the condition. Like type 2 diabetes, it disproportionately affects older adults, so it’s logical to look into whether having one of the two conditions puts you at an increased risk for the other. But so far, studies looking at this topic have yielded unclear or conflicting results, and there hasn’t been much research into biological features that could be shared by both conditions — potentially explaining how, if at all, the two are connected.
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Type 2 diabetes and Parkinson’s link
In the latest analysis, researchers looked at both population-based data on the two conditions and genetic markers that the two conditions could share. For the observation part of the analysis, they pooled data from studies that looked at either the risk of developing Parkinson’s, or the risk of the disease progressing in people who already had it, in people with type 2 diabetes. Based on the nine studies that looked at the risk of developing Parkinson’s, the researchers estimated that people with type 2 are 21% more likely to develop Parkinson’s than similar people without diabetes. Based on three studies that provided information on how long participants had diabetes, the link between diabetes duration and Parkinson’s was somewhat surprising — people with type 2 for less than 10 years were 46% more likely to develop Parkinson’s, while those with diabetes for 10 years or longer were only 20% more likely. When people with cardiovascular disease were excluded from the analysis, the link between type 2 and Parkinson’s remained, with a 29% higher risk for Parkinson’s in this group.
Based on three studies that looked at Parkinson’s disease progression in people with type 2, the researchers found that diabetes is linked to a faster rate of both the progression of motor symptoms (those related to movement) and cognitive decline. Separately, the researchers looked at how DNA variations known to influence the risk of type 2 diabetes were linked to the risk of developing Parkinson’s. They found that based on an analysis of 191 DNA variations linked to type 2, being predisposed to type 2 diabetes also makes a person about 8% more likely to develop Parkinson’s. The difference between this increased risk level based genes alone, and the larger effect found in observational data, may reflect certain lifestyle factors in people that also contribute to the risk of Parkinson’s.
Overall, the researchers wrote, these results provide “convincing evidence” that having type 2 diabetes increases both the risk of developing Parkinson’s, and the risk of Parkinson’s progression in people who already have it. More research is needed to know whether any behavioral factors, such as lifestyle factors or blood glucose control, could raise or lower the risk of developing Parkinson’s in people with diabetes.
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