Higher risk of Parkinson’s disease linked to lower total ‘bad’ cholesterol

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 diseaseaccording to a South Korean study.

In contrast, higher blood levels of high-density lipoprotein cholesterol (HDL-C), or “good” cholesterol, were associated with 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 disease.

“Our results suggest that the [blood] total cholesterol and low-density lipoprotein cholesterol levels over time are inversely associated with PD risk [Parkinson’s disease]“, wrote the researchers.

The study, “Association between serum lipid levels over time and risk of Parkinson’s diseasewas published in Scientific reports.

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Although Parkinson’s disease underlying mechanisms are not fully understood, potential risk and protective factors for neurodegenerative disease have been identified, including blood levels of fatty molecules like cholesterol.

Cholesterol is an essential component of cell membranes, with the brain containing the highest levels. The fatty molecule is involved in nerve cell communication and is part of myelin, the fatty sheath that surrounds nerve fibers.

It has been suggested that an alteration in the way cholesterol is processed may be linked to neurodegenerative processes in the brain. While previous studies have investigated the potential association between blood lipids and the risk of Parkinson’s disease, inconsistent results have been reported and may be due to methodological variabilities and insufficiently controlled potential influencing factors. Further, “most did not reflect the time-varying nature of [blood] lipid levels over time,” said researchers from South Korea, who assessed the potential link between blood lipid levels over an average follow-up period of 8.5 years and the occurrence of Parkinson’s disease.

They analyzed the complete lipid profile – the amount of cholesterol and triglycerides measured in the blood – out of 200,454 people from the Korean National Health Insurance screening cohort 2002-2019.

None of the participants had a medical history of Parkinson’s disease or secondary parkinsonism before or during the first year of follow-up, or had died during the first year. Additionally, none were on statin therapy, which helps lower LDL-C, before being enrolled.

At the start of the study, the participants had an average age of 57.4 years and 56.7% were men. Their average 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, less than 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 disease during the study. Additionally, 41,851 people (20.9%) started taking statins after participating in the study.

Lowest Total Cholesterol Levels, Highest Observed Parkinson’s Risk

After adjusting for potential influencing factors such as age, sex, smoking, and duration of statin therapy, participants with the lowest blood total cholesterol levels had a significantly higher risk of disease. Parkinson’s disease (by 17%) than those with average concentrations. Similar results were seen for LDL-C levels. Those with the lowest levels had a 19% higher risk of neurodegenerative disease than those with medium levels.

No significant association was found with higher levels of total cholesterol or “bad” cholesterol.

On the other hand, those with the highest HDL-C blood levels had an 11% lower risk of Parkinson’s disease than those with average levels. For those with the lowest levels, no difference was found in the risk of Parkinson’s disease compared to the average levels.

No significant association was found between blood triglyceride levels and Parkinson’s risk.

The team performed sensitivity analyses, in which the case definition of Parkinson’s was modified to include those using antiparkinsonian drugs, with at least one hospitalization or ambulance visit for Parkinson’s disease, or with other forms of secondary parkinsonism.

They found similar results for LDL-C and triglycerides, but the links between HDL-C and Parkinson’s disease were not always significant, although they all showed the same pattern.

“The association between [blood] HDL-C level and PD were less robust, while other results were similar to the primary analysis,” the researchers wrote.

The study results 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 disease.

However, “the impact of [blood] cholesterol ratios on PD risk were low or modest compared to previous studies that reported PD risk differed up to two-fold by [blood] cholesterol levels,” the researchers wrote, noting potential influencing factors “such as lifestyle factors, [simultaneous health conditions]and the use of statins, often overlooked in other studies, may have contributed to this discrepancy.

They said further research was needed to understand the mechanisms behind these findings and to determine the optimal range of blood cholesterol levels to minimize the risk of Parkinson’s disease.