Study says metabolic abnormalities may be risk factor for Parkinson’s
Having metabolic syndrome linked to nearly 40% higher risk of disease
People with metabolic syndrome, a cluster of metabolism-related abnormalities — like a larger waist circumference, high blood sugar, and abnormal blood levels of fatty molecules — may have a higher risk of Parkinson’s disease, according to the findings of a new study by an international team of researchers.
Having metabolic syndrome was significantly linked to a 39% increased risk of Parkinson’s, while having both metabolic syndrome and certain genetic risk factors was associated with more than double the risk. Still, whether there is a cause-and-effect relationship between these two conditions remains unclear, the researchers noted.
“Our findings suggest that metabolic syndrome may be a modifiable risk factor for Parkinson’s disease,” and that “maintaining metabolic health may be especially important for people who have genes that increase their risk for Parkinson’s disease,” Weili Xu, PhD, the study’s senior author at the Karolinska Institutet in Sweden, said in a press release from the American Academy of Neurology (AAN).
The study, “Metabolic Syndrome and Incidence of Parkinson Disease,” was published in Neurology, the medical journal of the AAN.
The AAN release noted that “after adjusting for age, smoking status, physical activity and genes that increase the risk of Parkinson’s disease, researchers found that people with metabolic syndrome were about 40% more likely to develop Parkinson’s disease than people without the syndrome.”
According to Xu, “future studies are needed to see whether working to control metabolic syndrome could help prevent Parkinson’s disease.”
A chronic, progressive condition marked by motor and nonmotor symptoms, Parkinson’s is caused by the death of certain neurons in the brain. As in many other diseases, several genetic and environmental factors can impact a person’s risk of developing Parkinson’s.
Some previous research has suggested a potential link between metabolic syndrome and Parkinson’s risk, but most of these studies have been limited by a short-term follow-up. Now, the team of scientists sought to learn more.
Metabolic syndrome “is a well-established risk factor of a diverse spectrum of chronic diseases … and is also highly modifiable, making it an ideal target for preventive strategies,” the team wrote.
Most metabolic abnormalities are ‘highly modifiable’
Clinicians define metabolic syndrome as having at least three of five specific metabolic symptoms. These are larger waist circumference, characterized as abdominal obesity, high blood pressure, high blood sugar, high blood levels of a type of fat called triglycerides, and low blood levels of high-density lipoprotein cholesterol (HDL-C), a fatty molecule commonly called good cholesterol.
Here, the research team explored the connection between these factors — both individually and combined — and the risk of Parkinson’s. Their study involved 467,200 individuals from the U.K. Biobank, who had a mean age of 56.53. Slightly more than half were female. None had Parkinson’s at the beginning of the study.
Altogether, 38% of these individuals met metabolic syndrome criteria. They tended to be older, male, white, of higher socioeconomic status, and less physically active than their counterparts without metabolic syndrome.
About 0.7% of all participants — 3,222 of the more than 465,000 — developed Parkinson’s over a median follow-up period of 14.6 years, data showed.
Having metabolic syndrome was significantly associated with a 39% higher risk of Parkinson’s. Also, a higher number of metabolic syndrome components was linked to a higher risk, which increased by 14% with each additional metabolic syndrome criterion that an individual met. Having all five components was linked to a twofold higher risk.
[The findings suggest] that there may be specific constellations of [metabolic syndrome] components that are most strongly related to PD [Parkinson’s disease] and which might benefit most from preventive strategies aimed at reducing their PD risk.
Among individual metabolic symptoms, all but high triglyceride levels correlated with a high Parkinson’s risk. For example, people with low HDL-C levels had a 43% greater risk of Parkinson’s than their counterparts within normal ranges, and those with abdominal obesity had a 33% higher risk.
“This finding suggests that there may be specific constellations of [metabolic syndrome] components that are most strongly related to PD [Parkinson’s disease] and which might benefit most from preventive strategies aimed at reducing their PD risk,” the team wrote.
Greatest risk seen with metabolic abnormalities and genetic susceptibility
Additionally, the scientists discovered that the risk of Parkinson’s was greatest among individuals with metabolic syndrome and a genetic susceptibility for Parkinson’s — there are numerous genetic variants known to increase a person’s risk of the disease. Individuals with both metabolic syndrome and these genetic variants face a 2.5 times higher risk relative to those without any of these factors, the researchers noted.
According to Xu, “we … found a higher risk of Parkinson’s disease for people with both metabolic syndrome and a genetic susceptibility for Parkinson’s disease.”
To extend these results, the researchers repeated their analyses using other published data about metabolic syndrome and Parkinson’s risk. This meta-analysis included data from nearly 25 million individuals.
The team found that the association between these two conditions was slightly lower than in the original population, with a 29% higher risk of Parkinson’s among those with metabolic syndrome.
More research needed to determine cause and effect, scientists say
Overall, these findings support a relationship between Parkinson’s and metabolic syndrome, although the researchers could not determine the nature of this relationship. It remains unclear whether metabolic syndrome raises Parkinson’s risk, Parkinson’s raises metabolic syndrome risk, or some combination, according to the team.
For example, people with Parkinson’s may be less likely to engage in physical activities, even before diagnosis. This could then increase their risk of metabolic syndrome.
Future research could explore this relationship and consider potential interventions.
“Whether the prevention or mitigation of [metabolic syndrome] can alter PD risk among those with a high genetic predisposition requires further investigation in future studies,” the researchers wrote.
The team noted, however, that because about 90% of participants in the U.K. Biobank portion of the study were white individuals, studies involving a more diverse population are needed to determine whether these findings can be generalized to other ethnicities.
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