The study led by Mary Haan, epidemiology professor at the University of Michigan School of Public Health consisted of older Mexican-Americans in Sacramento, Calif., who suffered from metabolic conditions that put them at risk for developing dementia, Alzheimer's or cognitive impairment without dementia,
Some of the risk factors for dementia include high cholesterol, Type 2 diabetes, obesity and hypertension.
"The bottom line is that if a person takes statins over a course of about 5-7 years, it reduces the risk of dementia by half, and that's a really big change," said Haan, who notes that the study did not look at statins as a treatment for existing dementia, only as a preventative. Statins are drugs that specifically lower LDL or bad cholesterol.
"In older people you have so many different chronic conditions, especially in this group, that the chance of any intervention having an effect is fairly limited.
"Say you're 75 or 80 and you've got six diseases. How much is a treatment really going to help? This showed if you started using statins before the dementia developed you could prevent it in about half of the cases," she added.
Haan hopes the study will help fuel randomized trials to test statins and their ability to prevent dementia.
Of 1,674 participants who were free of dementia at the start of the study, 27 percent, or 452 people, took statins at some point in the study.
Over the five-year follow up period, 130 participants developed dementia or cognitive impairment.
"We aren't suggesting that people should take statins for purposes other than what they are indicated for, but hopefully this study and others will open the door to statin testing for dementia and other types of cognitive impairment," said Haan.
The paper, "Use of Statins and Incidence of Cognitively Impaired Not Demented and Dementia in a Cohort Study," will appears journal Neurology.