Low LDL Cholesterol Levels Linked to Parkinson's Disease
Doctors consider low LDL cholesterol levels one of the gold standards for good health as this type of "bad" cholesterol increases the risk of cardiovascular disease, the nation's leading killer. New data from a small, retrospective study show a link between low LDL levels and Parkinson's disease. If future research proves LDL levels actually cause the disease, then minimizing Parkinson's risk–which is already complicated because the cause of the degenerative neurological disease remains unclear and smoking paradoxically protects against it–will be even messier for doctors to explain.
The study, which will be published in the January edition of Movement Disorders, compared 124 people with Parkinson's with their spouses who didn't have the disease. It found that people with low LDL levels (lower than 114 mg/dL) had a 3.5-fold higher occurrence of the disease than those with higher LDL levels (more than 138 mg/dL). For comparison, the average LDL level of Americans 20 and above is 123 mg/dL.
"However, people absolutely should not change their diet or try to change their cholesterol levels," says study author Xuemei Huang, a University of North Carolina School of Medicine neurologist who specializes in Parkinson's. She strongly emphasizes that her results, though intriguing, need to be confirmed by additional prospective studies.
Huang's study is considered retrospective by scientists because it recruited participants who already had Parkinson's and then looked backward at factors like age, sex, cholesterols levels, use of cholesterol-lowering drugs, and smoking habits to see if any of these characteristics were associated with the disease. A prospective study, in contrast, starts with healthy patients and follows them forward. Retrospective studies show associations but not necessarily causation, while well-designed prospective studies make more compelling cases for causation. Doing a prospective study, however, is difficult for chronic diseases because it often involves following participants for years or decades.
"One problem is that we don't know if the low-LDL levels caused the Parkinson's or if Parkinson's caused the low-LDL levels," says David Standaert, a Parkinson's expert at the University of Alabama who commented on the new study. Interestingly, Huang's study also found that participants with Parkinson's were much less likely to take cholesterol-lowering drugs called statins than their Parkinson's-free spouses. It is possible, then, that statins might protect against Parkinson's disease. But, again, more research is needed to confirm this theory, cautions Huang.