Lower blood levels of total cholesterol and low-density lipoprotein cholesterol (LDL-C), or “bad” cholesterol, are significantly associated with a higher risk of Parkinson’s disease, according to a study from South Korea.
In contrast, higher blood levels of high-density lipoprotein cholesterol (HDL-C), or “good” cholesterol, were linked to a lower risk. No significant association was found between levels of triglycerides — another type of fatty molecule, or lipid, in the blood — and the risk of Parkinson’s.
“Our results suggest that the [blood] total and low‐density lipoprotein cholesterol levels over time are inversely associated with the risk of PD [Parkinson’s disease],” the researchers wrote.
The study, “Association between serum lipid levels over time and risk of Parkinson’s disease,” was published in Scientific Reports.
Although Parkinson’s underlying mechanisms are not fully understood, potential risk and protective factors for the neurodegenerative disease have been identified, including the blood levels of fatty molecules such as cholesterol.
Cholesterol is an essential component of cell membranes with the brain containing the highest levels of it. The fatty molecule is involved in nerve cell communication and is part of myelin, the fatty sheath that surrounds nerve fibers.
It’s been suggested that impairment in how cholesterol is processed may be related to neurodegenerative processes in the brain. While previous studies investigated the potential association between blood lipids and Parkinson’s risk, inconsistent findings were reported and may have been due to methodology variabilities and potential influencing factors not being adequately controlled. Also, “most did not reflect the time-varying nature of [blood] lipid levels over time,” said researchers from South Korea, who evaluated the potential link between blood lipid levels over a mean follow-up period of 8.5 years and Parkinson’s occurrence.
They analyzed the complete lipid profile — the amount of cholesterol and triglycerides measured in the blood — of 200,454 people from the 2002–2019 Korean National Health Insurance Health Screening Cohort.
No participant had a medical record of Parkinson’s disease or secondary Parkinsonism before or during the first year of follow-up, or was deceased during the first year. Also, none were on statin therapy, which helps lower LDL-C, before being enrolled.
At the study’s start, participants had a mean age of 57.4, and 56.7% were men. Their mean blood levels of total cholesterol, which includes LDL-C and HDL-C, were 198.7 mg/dL (normal, less than 200 mg/dL). LDL-C levels were 118.6 (normal, below 100 mg/dL); HDL-C levels were 54.8 (normal, 60 mg/dL or higher). Their triglyceride levels were 131.4 mg/dL (normal, less than 150 mg/dL).
A total of 1,712 people (0.85%) developed Parkinson’s during the study. Also, 41,851 people (20.9%) started statins after entering the study.
Lowest total cholesterol levels, highest Parkinson’s risk seen
After adjusting for potential influencing factors such as age, sex, smoking, and time under statin treatment, participants with the lowest blood levels of total cholesterol had a significantly higher risk of Parkinson’s (by 17%) than those with middle concentrations. Similar findings were observed for LDL-C levels. Those with the lowest concentrations had a 19% higher risk of the neurodegenerative disease than those with middle levels.
No significant associations were found with the highest levels of either total or “bad” cholesterol.
On the other hand, those with the highest blood HDL-C levels had an 11% lower risk of Parkinson’s than those with medium concentrations. For those with the lowest levels, no difference was found in the risk of Parkinson’s compared with the middle concentrations.
No significant associations were found between blood triglyceride levels and Parkinson’s risk.
The team performed sensitivity analyses, wherein the definition of Parkinson’s cases was changed to include those using antiparkinsonian medications, with at least one hospital admission or ambulance visit for Parkinson’s, or with other forms of secondary parkinsonism.
They obtained similar results for LDL-C and triglycerides, but links between HDL-C and Parkinson’s were not always significant, although they all showed the same trend.
“The association between [blood] HDL-C level and PD was less robust, while other findings were similar to those of the main analysis,” the researchers wrote.
The study findings are consistent with some previous studies where lower levels of total cholesterol, LDL-C, and HDL-C were associated with a higher risk of Parkinson’s.
However, “the impact of [blood] cholesterol levels on the risk of PD was small or modest compared to previous studies that reported that the risk of PD differed by up to twofold according to the [blood] cholesterol level,” the researchers wrote, noting potential influencing factors “such as lifestyle factors, [simultaneous health conditions], and statin use, which were often neglected in other studies, might have contributed to this gap.”
They said more research is needed to understand the mechanisms behind these findings and determine the optimal range of blood cholesterol levels to minimize Parkinson’s risk.