The study, “Association of statin use with Parkinson’s disease: Dose-response relationship,” was published in the journal Movement Disorders.
Statins are one of the most commonly prescribed medications to prevent cardiovascular disease. This group of molecules can lower cholesterol and have a potent anti-inflammatory effect with the capacity to reduce oxidative damage (cellular damage as a consequence of high levels of oxidant molecules).
As such, there is a hypothesis that statins can protect against neurodegenerative diseases. “Growing evidence has revealed that statins decrease the [alpha]-synuclein burden and dopaminergic cell death in animal and cell models of PD [Parkinson’s disease],” researchers wrote.
However, this link remains inconsistent. While some studies report that using statins lowers the likelihood of a person developing Parkinson’s, other studies report the exact opposite — that statin use increases Parkinson’s risk. Other studies report no association at all. Importantly, these studies haven’t typically divided statin users based on cholesterol levels, or on their time-varying status of statin use.
“[P]revious conflicting results regarding the association between statin use and PD risk might be derived from this complicated interrelationship among cholesterol levels, statin adherence, and PD risk,” researchers explained.
To gain insight into this possible relationship, researchers analyzed data from the Korean National Health Insurance Service, which insures 97% of the South Korean population and includes data on disease diagnoses and medication use. The investigators focused on patients who were older than 60 in 2002 and excluded patients who already had been diagnosed with Parkinson’s or had other neurological conditions like dementia.
The study group consisted of 87,797 individuals who were followed for 10 years, from the beginning of 2006 to the end of 2015.
The researchers also divided these individuals into statin users (~12% of the total population) and non-users, and they further divided statin users based on how much statin they used — both the dosage and the number of days in a year that they took the medicine. Total cholesterol levels also were taken into account.
Overall, statin users were more likely than non-users to develop Parkinson’s. However, the relationship was less clear-cut when researchers examined people who took different amounts of statins.
While those who used relatively low amounts of statins (for less than one year) were significantly more likely to develop Parkinson’s, this association disappeared among people who took more of the drug more frequently (365 to 540 days). “With increasing duration and adherence to statin treatment, the trend of statins facilitating PD disappeared,” the investigators wrote.
There is some data that low cholesterol might increase the risk of developing Parkinson’s. In accordance, the researchers note that in their study population, low cholesterol levels were associated with a slightly greater risk of Parkinson’s. So, it’s possible that statins increase the risk of Parkinson’s simply through their intended function.
An alternative explanation is that statins don’t cause Parkinson’s, but instead make its symptoms more noticeable. It follows that people taking statins would be more likely to be diagnosed, even if there’s no difference in how the disease actually progresses.
Both explanations are plausible, but because this study shows only a correlation, it’s impossible to say which, if either, is right. More research is needed.