The statin, Simvastatin, has been found to cut the risk of developing Alzheimer’s and Parkinson’s disease by 50 percent.

Researchers at Boston University School of Medicine analyzed diagnostic, pharmaceutical, and demographic data of around 4.5 million people. This data was collected from various medical centers across the country.
To analyze the effects, researchers used three different models and examined the effects of the statins simvastatin, lovastatin, and atorvastatin on people.

They found a considerable decline in the occurrence of Alzheimer’s as well as Parkinson’s disease in people on simvastatin in each of the three models.
It is speculated that simvastatin is more beneficial as it possesses both high potency and the capability to enter the brain.

Source: Boston University