In a study of more than 17,000 people 60 and older, use of statin drugs appeared to cut the risk of developing dementia by more than half.
The study does not prove that statins prevent cognitive decline, and no one should start taking them as a dementia preventive, doctors stress. But the findings are compelling enough to justify further study, says Alina Solomon, MD, a researcher in the department of neurology at the University of Kuopio in Finland.
The study was presented at the Alzheimer's Association 2009 International Conference on Alzheimer's Disease.
Other studies have had conflicting results on the ability of statins to protect against memory loss, dementia, and Alzheimer's disease, but this study is one of the largest to date. The trial included Finnish people enrolled in a larger, ongoing study examining risk factors for heart disease and stroke.
The current analysis involved 17,257 participants 60 and older who had not been diagnosed with dementia or Alzheimer's disease in 1995. Over the next 12 years, 1,551 of them were diagnosed with dementia. Of those, 281, or 18%, had taken statins for at least one year prior to the diagnosis.
One advantage of the current study is that data about statin use was obtained from a drug reimbursement registry, Solomon tells WebMD. Some of the previous trials relied on patients to self-report use of cholesterol-lowering drugs, which can be especially problematic when working with people with dementia, she explains.
After adjusting for risk factors for dementia, including age, sex, education level, place of residence, body mass index, blood pressure, and cholesterol levels, the researchers found that people who took statin drugs were 58% less likely to develop dementia than those who did not.
Statins and Insulin Levels in Brain
Statins help protect against heart attacks and strokes by lowering low-density lipoprotein (LDL), or "bad" cholesterol. But since the current analysis was adjusted for participants' cholesterol levels, that action alone does not fully explain statins' apparent punch against dementia, Solomon says.
So what is going on? A risk factor for dementia is high insulin; one theory is that statins may lower the high insulin levels in the brain. Statins have also been shown to reduce levels of C-reactive protein (CRP), a marker of inflammation that has been linked to the pathology that can lead to dementia, researchers say.
"There's a lot more work to be done," Solomon says. The next step for her team: determining whether the type of statin drug, dosage, or duration of treatment affects the results. "Two other studies didn't show that the type of statin made a difference, but we're checking that," she says.
Ronald Petersen, MD, PhD, professor of neurology at the Mayo Clinic in Rochester, Minn., and chair of the Alzheimer's Association Medical & Scientific Advisory Council, notes that two large studies showed that statins do not appear to prevent Alzheimer's disease.
But dementia develops before Alzheimer's, and it could be that it "was a matter of too little too late. More and more research suggests you have to give interventions early to have an impact on Alzheimer's disease," he tells WebMD.
The best way to settle the issue, doctors agree, is a primary prevention trial in which half of people take statins and half don't. Then, they are followed over time to see how many in each group develop dementia or Alzheimer's. "That's the gold standard," Solomon says.