Are statins a key to preventing Alzheimer's disease?
Kermit Williams Jr. | 12/12/2016, 2:54 p.m. | Updated on 12/12/2016, 2:54 p.m.
(CNN) - Although doctors prescribe statins to help lower cholesterol, the drugs might have an added benefit: reducing Alzheimer's disease risk.
Regular use of statins is associated with a reduced risk for Alzheimer's, according to a study published in the journal JAMA Neurology on Monday. Statins are a class of drugs used to reduce low-density lipoprotein, LDL cholesterol, within the body. The drug works by inhibiting the enzyme involved in the body's ability to produce LDL cholesterol.
The significance of this reduction seems to vary based on sex and ethnicity, said Julie Zissimopoulos, an assistant professor at the University of Southern California's Sol Price School of Public Policy and lead author of the study.
"We found risk reduction was slightly higher for women compared to men. So for women, the risk reduction and the onset of Alzheimer's was 15%. For men, it was 12%," Zissimopoulos said, adding that for Hispanic men in particular, the size of the reduction was much larger at 29%.
However, "it's important to know that this is not a study that establishes causality, because it's not an experiment," she said. "It's really important to put this study in the context of where we are in Alzheimer's disease treatment and prevention, and there's still no treatment that exists to delay or prevent Alzheimer's disease."
Alzheimer's disease, the most common cause of dementia among older adults, damages memory and thinking skills. It is the sixth leading cause of death in the United States, according to the National Institute on Aging. More than 5 million Americans are estimated to have the disease.
Surprising differences across statins
The new study involved Medicare data on 399,979 statin users 65 or older. They had no diagnosis of Alzheimer's disease and used statins between 2006 and 2008. Whether or not each statin user was diagnosed with Alzheimer's was tracked in data from 2009 to 2013.
After analyzing the data, Zissimopoulos and her colleagues found that those who were exposed to higher levels of statins -- such as from filling more prescriptions than others in a given year -- were 10% less likely to have an Alzheimer's disease diagnosis in each of the subsequent five years than those with lower statin exposure.
Specifically, the statin drug simvastatin (sold under the brand name Zocor) was associated with a lower risk for white women, Hispanic women, black women, white men and Hispanic men. Atorvastatin (Lipitor) was associated with reduced risk among white, black and Hispanic women and Hispanic men. Pravastatin (Pravachol) and rosuvastatin (Crestor) were associated with reduced risk for only white women.
For black men, the sample size within the data was too small to identify any statistically significant reductions for any statin drug, Zissimopoulos said.
"All of the statins seem to have some risk reduction, although the findings are much more consistent for simvastatin and atorvastatin, meaning they consistently reduce the risk of Alzheimer's disease across men and women and across most race and ethnic groups," she said.
Simvastatin and atorvastatin are lipophilic, which means they can cross the blood-brain barrier to enter the brain, possibly holding clues to why these statin types showed a consistent association with reduced risk in the study.