April 13, 2011 -- Treating high blood pressure and other so-called vascular risk factors in people who have mild cognitive impairment may reduce their risk of progressing to Alzheimer's disease, according to a new study.
"Recent animal studies suggest that vascular risk factors play roles in the development of Alzheimer's disease," says researcher Yan-Jiang Wang, MD, PhD, a professor of neurology at Third Military Medical University in Chongqing, China.
"But it still remains unclear whether vascular risk factors cause Alzheimer's disease in humans," he tells WebMD in an email. "Our study provides important evidence in humans which supports the idea that vascular risk factors play a critical role in the development of Alzheimer's disease."
Reducing the Risk of Alzheimer's Disease: Study Details
The researchers enrolled 837 men and women, all aged 55 and older.
All had a condition known as mild cognitive impairment (MCI), which is a mental condition less severe than dementia, with symptoms such as forgetting recent events, difficulty multitasking, and taking longer to perform mental tasks. MCI increases the risk of progressing to Alzheimer's disease.
At the start of the study, 414 had one or more vascular risk factors, such as high blood pressure, high cholesterol, or diabetes.
Wang's team evaluated the participants each year for five years with standard tests of cognitive function and their ability to do daily activities.
After some dropped out, 650 completed the follow-up. During that time, 298 progressed to Alzheimer's, while the others remained with mild cognitive impairment. Participants who had vascular risk factors were twice as likely to develop Alzheimer's over the five-year follow-up as those who did not have any of the vascular risk factors.
However, study participants who received treatment for all their vascular risk factors were 39% less likely to get Alzheimer's disease over the follow-up period than those who got no treatment.
Even treating some of the risk factors helped. It reduced the risk of progression by 26%.
The study is strictly observational, the researchers say. Therefore, it cannot prove cause and effect. However, they write, ''active intervention for vascular risk factors might reduce progression in MCI to Alzheimer's disease dementia."
Although the link is not proven, Wang tells WebMD ''there would be no downside to treating the vascular risk factors."
Vascular Risk Factors and Delaying Alzheimer's: Explaining the Link
Researchers say it's unclear why the risk factors appear to speed the progression from MCI to Alzheimer's disease.
Some of the vascular risk factors may directly affect the metabolism of a protein known as beta-amyloid. The protein has been linked with Alzheimer's disease. When it accumulates in the brain, it is believed to disrupt cells and cellular functioning.
That may indicate that vascular risk factors play a pivotal or causal role in Alzheimer's, the researchers write.
Delaying Alzheimer's Disease: Perspective
The new study findings offer a great message for people, says William Thies, PhD, chief medical and scientific officer for the Alzheimer's Association. "Get your cardiovascular risk factors checked, and get treatment if you need it," he says."The benefits for you may be far more than [preventing] vascular disease."
He reviewed the study for WebMD but was not involved in the research.
He adds, however, that the study is simply observational, not a clinical trial. So it does not prove that treating vascular risks will definitely delay the progression to Alzheimer's.