Keeping your blood pressure under control may help to ward off Alzheimer’s in old age, a new study found.
The study included 118 men and women, ages 47 to 89, who were part of the Dallas Lifespan Brain Study, a large and ongoing study of brain changes that occur with aging. Participants underwent brain scans that measured levels of beta-amyloid, a toxic protein that builds up in the brains of those with Alzheimer’s, forming the telltale plaques of the disease.
Amyloid plaque may be among the first signs of Alzheimer's disease, appearing a decade or more before Alzheimer's symptoms like memory impairment begin. Earlier research has shown that at least 20 percent of older adults have high levels of beta-amyloid, putting them at increased risk of developing Alzheimer’s in old age.
Study volunteers also underwent gene testing to see whether they carried the APOE-E4 gene, which increases Alzheimer’s risk. People who carry two copies of this gene, inherited from each parent, are at 10 to 12 times higher risk of developing Alzheimer’s than those who don’t carry the gene. Carrying just one copy of the gene also increases Alzheimer’s risk, by two- to four-fold. About 20 percent of the population carries the APOE-E4 gene.
"I became interested in whether hypertension was related to increased risk of amyloid plaques in the brains of otherwise healthy people," said Dr. Karen Rodrigue, the lead author of the study and an assistant professor in the University of Texas, Dallas, Center for Vital Longevity. She suspected that the double-whammy of hypertension and the presence of the APOE-E4 gene might lead to particularly high levels of amyloid plaque in healthy adults.
The most striking result of the study, published in the journal JAMA Neurology, was that adults with untreated high blood pressure who also carried a genetic risk factor for Alzheimer's disease showed much higher beta-amyloid levels than all other groups. Adults who were taking blood pressure medicines, even those with genetic risks for Alzheimer’s, however, had levels of plaque buildup that were equivalent to those who did not have high blood pressure or a genetic risk.
The findings suggest that keeping blood pressure under control may significantly decrease the risk of developing beta-amyloid deposits, even in those genetically predisposed to plaque buildup. Other research has shown that taking blood pressure medications for those with hypertension may lower the risk of Alzheimer’s. Keeping blood pressure under control also is proven to lower the risk of stroke and other serious ailments.
Scientists aren’t sure why high blood pressure increases plaque buildup, though studies in animals suggest it may make it easier for beta-amyloid to enter the brain.
More research is needed to better understand the link between high blood pressure and Alzheimer’s. But this study, which looked at otherwise healthy middle-aged men and women, sheds important light on risk factors that may be modified to lower Alzheimer’s risk.
"Identifying the most significant risk factors for amyloid deposition in seemingly healthy adults will be critical in advancing medical efforts aimed at prevention and early detection of Alzheimer’s," Dr. Rodrigue said.
Karen M. Rodrigue, PhD; Jennifer R. Rieck, MS; Kristen M. Kennedy, PhD; et al: “Risk Factors for β-Amyloid Deposition in Healthy Aging: Vascular and Genetic Effects.” JAMA Neurology, published online, March 13, 2013.