Major journal reports study findings
A study in the JAMA Neurology (formerly the Archives of Neurology) suggests that controlling or preventing risk factors such as hypertension earlier in life may limit or delay the brain changes associated with Alzheimer's disease and other age-related neurological deterioration.
Dr. Karen Rodrigue, assistant professor in the UT Dallas Center for Vital Longevity (CVL), was lead author on a study that looked at whether people with both hypertension and a common gene associated with risk of Alzheimer's disease (the APOE-4 gene carried by about 20 percent of the population) had more buildup of the brain plaque (amyloid protein) associated with Alzheimer's disease. Many scientists believe the amyloid plaque is the first symptom of Alzheimer's disease and shows up a decade or more before Alzheimer's symptoms of memory impairment and other cognitive difficulties begin.
Until recently, amyloid plaque could only be seen at autopsy, but new brain scanning techniques allow scientists to see the amyloid plaque in living brains of healthy adults. Findings from both autopsy and amyloid brain scans show that at least 20 percent of normal older adults carry elevated levels of amyloid, a substance made up mostly of protein and deposited in organs and tissues.
"I became interested in whether hypertension was related to increased risk of amyloid plaques in the brains of otherwise healthy people," Rodrigue said. "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."
Based on evidence that hypertension was associated with Alzheimer's disease, Rodrigue suspected that the double-whammy of hypertension and presence of the APOE-e4 gene might lead to particularly high levels of amyloid plaque in healthy adults.
Rodrigue's research was part of the Dallas Lifespan Brain Study, a comprehensive study of the aging brain in a large group of adults of all ages funded by the National Institute on Aging. As part of this study, the research team recruited 147 participants (ages 30-89) to undergo cognitive testing, magnetic resonance imaging (MRI) and PET imaging, using Amyvid, a compound that when injected travels to the brain and binds with amyloid proteins, allowing the scientists to visualize the amount of amyloid plaque. Blood pressure was measured at each visit.
Rodrigue classified participants in the study as hypertensive if they reported a current physician diagnosis of hypertension or if their blood pressure exceeded the established criteria for diagnosis. The participants were further divided between individuals who were taking anti-hypertensive medications and those who were not medicated, but showed blood pressure elevations consistent with a diagnosis of hypertension. Finally, study subjects were classified in the genetic risk group if they were in the 20 percent of adults who had one or two copies of an APOE ε4 allele, a genetic variation linked to dementia.