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Statins Not Associated with Reduced Dementia Risk Says New Study

July 11, 2005 - The use of statins and other lipid-lowering agents by older adults was not associated with a reduced risk of Alzheimer's disease or other types of dementia, according to a study of people over 65 that appears in the July issue of Archives of Neurology, one of the JAMA/Archives journals. An earlier study had raised the possibility of statins blocking dementia, based primarily on evidence that people with high blood pressure are more likely to develop cognitive impairment, a mild form of dementia.

Statins may reduce cardiovascular risk by inhibiting cholesterol synthesis or through anti-inflammatory effects, biological mechanisms which may play a role in the development of dementia, particularly Alzheimer's disease, according to background information in the article. Previous studies have suggested that statins may have a protective effect on the process of dementia, preventing or delaying onset.

Thomas D. Rea, M.D., M.P.H., of the University of Washington, Seattle, and colleagues assessed data on 2,798 participants 65 years or older in the Cardiovascular Health Study who underwent baseline magnetic resonance imaging (MRI) and took a standardized mental test to determine that they were free of dementia when enrolled in the study (between 1991 and 1994). 

At baseline, information on their health status, cognitive function and medication use, as well as laboratory assessments and diagnostic testing was collected. Participants were followed up annually to assess their health status, medication use and whether they had developed dementia.

During a total of 15,030 person years (number of individuals followed over time until development of disease or end of the study) of follow-up, there were 480 cases of dementia, including 245 attributable to Alzheimer's disease alone. 

After controlling for other known or suspected risk factors, the researchers found that patients who had ever used statins had no reduction in their risk of developing dementia from any cause (Alzheimer's disease, mixed Alzheimer's disease and vascular dementia or vascular dementia alone) compared with those who had never used statins.

"Several factors may explain why statin use was not associated with a lower risk of dementia," the authors write. "Participants were on average 75 years of age, and statin use was assessed for a median of five years. Statin exposure may need to occur earlier in adulthood or for longer periods to prevent dementia, although analyses that stratified the duration of statin use did not suggest a duration-dependent association."

"In this investigation, statin therapy was not associated with a lower risk of dementia," the authors concluded. "Although statin use is an important treatment for cardiovascular disease, additional investigation is needed to determine whether and for whom statin use may affect dementia risk."

In the earlier study published in January by JAMA those researchers looked at one study that showed a 50 percent reduction in the incidence of dementia in a group of patients with high blood pressure who were treated over four years with a calcium-channel blocking blood pressure drug. And patients who received the blood pressure drug had a lower chance of developing Alzheimer's disease, vascular dementia or mixed dementia.

This corresponds with observational data showing that people with high blood pressure are more likely to develop cognitive impairment, a mild form of dementia that often acts as a warning sign for later dementia, the authors said. And other observational studies have suggested that treatment for high blood pressure can protect against cognitive decline.

The authors were specifically looking at mixed dementia, which is a combination of Alzheimer’s and vascular dementia. One area they explored was evidence relating to drugs that reduce cholesterol or thin the blood. They found that prospective studies on cholesterol drugs called statins haven't shown a specific effect on dementia, but follow-up periods in such studies have been short.

There's other evidence that reducing cholesterol may help brain function, though, they reported.

“Some, but not all, observational studies have shown that people with high cholesterol in middle age are more likely to develop mild cognitive impairment and Alzheimer's disease. And since statins decrease risk of stroke, they can also decrease the risk of harm to thinking ability that often comes with stroke,” they said.

So, it appears neither study clearly shuts the door on the possibility of statins playing some role in dementia protection.

Editor's Note: This study was supported by grants from the National Heart, Lung, and Blood Institute, Bethesda, Md. and the National Institute on Aging, Bethesda, Md.

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