ATLANTA — Simvastatin use for at least 7 months reduced the incidence of Alzheimer's disease by 30% and Parkinson's disease by 24% in older people, according to an analysis of a Department of Veterans Affairs pharmaceutical database.
Neither lovastatin nor atorvastatin provided similar benefits.
The protective effects of simvastatin were more prominent in people who do not have hypertension. In this subgroup, the incidence of Alzheimer's disease was reduced by 76% and the incidence of Parkinson's disease was reduced by 65%, the study's lead investigator Dr. Benjamin Wolozin reported at the annual meeting of the Society for Neuroscience.
Dr. Wolozin, a professor of pharmacology at Boston University, analyzed data from a large VA pharmaceutical database that included 4.5 million patients and more than 110 million annual medication prescriptions. Individuals were excluded if they were less than 65 years of age or had a pre-existing diagnosis of senile dementia of the Alzheimer's type.
The incidence of Alzheimer's disease among patients taking statins was compared with the incidence among patients who were not taking statins. After adjusting for age, cardiovascular disease, hypertension, and diabetes, only simvastatin use significantly lowered the incidence of Alzheimer's disease (hazard ratio 0.694).
Two different mechanisms might explain the unique effects of simvastatin compared with those of the other two statins analyzed, Dr. Wolozin said. For atorvastatin, the inability to cross the blood-brain barrier may explain its ineffectiveness. Lovastatin and simvastatin both reduce inflammation, he explained. Only simvastatin, however, inhibits cholesterol strongly enough to reduce inflammation sufficiently to protect against Alzheimer's or Parkinson's disease. Studies have shown that a biosynthetic precursor of cholesterol is required to signal inflammation. Why simvastatin is unable to reduce inflammation associated with hypertension is unclear.
Dr. Wolozin is currently analyzing the effects of several medications used chronically by older patients to investigate their impact on the incidence and progression of Alzheimer's disease. “In addition to finding medications that are therapeutically beneficial, these analyses may also tell us what kinds of factors precipitate AD in elderly people.”
Only simvastatin inhibits cholesterol enough to reduce inflammation to protect against AD and Parkinson's. DR. WOLOZIN
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