The preliminary results from a US study suggest a link between low LDL (or 'bad') cholesterol and Parkinson's disease, which could have implications for LDL-lowering drugs such as statins. The possibility of such a link has been discussed for many years, although the benefits of taking statins for those with high LDL levels far exceeds any possible increased risk of developing Parkinson's.
The retrospective study at the University of North Carolina, published in the December 2006 issue of Movement Disorders and highlighted in a recent article in Chemistry and Industry, showed that patients with low LDL cholesterol levels (less than 114 mg per decilitre) were more than three times likely to develop Parkinson's than those with higher levels (above 138 mg per decilitre).
However, the study also showed that participants taking statins to reduce their LDL cholesterol levels were less likely to have Parkinson's disease. Huang believes this could be because those most at risk are those patients who have had low LDL levels all their lives.
If a link between taking statins and Parkinson's does exist, a surge in Parkinson's diagnoses is likely to occur within the next five years, as statins will have been in common usage for over a decade.
Xuemei Huang, lead author of the study, said that two questions need to be answered: "One is whether lower cholesterol predates the onset of Parkinson's.
Number two, what is the role of statins in that? In other words, does taking cholesterol-lowering drugs somehow protect against Parkinson's? We need to address these questions."
The world's biggest selling drug, Pfizer's LDL-reducing statin Lipitor (atorvastatin) had worldwide sales of $12.1bn in 2005. Until it came off patent mid-2006, Merck's Zocor (simvastatin) had annual sales of $4.8bn and was ranked in the top five-bestselling drugs.
Professor Yoav Ben-Shlomo, chair of clinical epidemiology at the University of Bristol, believes the study fails to show whether low LDL cholesterol is a consequence or a cause of Parkinson's.
Huang claims that previous studies linking Parkinson's with a gene associated with low LDL levels, apoE2, supports her theory that low LDL levels are the cause.
The authors are now instigating a large-scale study into the findings and are currently planning a 16,000 patient prospective study to research the link. Another large scale study is underway at Harvard University.