March 19, 2013
Getting A Handle On Stress May Reduce Risk Of Dementia
Lawrence LeBlond for redOrbit.com - Your Universe Online
Stress, hypertension, high blood pressure — no matter what you call it, researchers are warning it can increase the risk of dementia. And by controlling or preventing risk factors that lead to hypertension earlier in life, people may limit or delay the changes in their brain associated with Alzheimer´s disease and other age-related cognitive declines, according to new research published in JAMA Neurology.
The study, led by Dr. Karen Rodrigue, assistant professor in the UT Dallas Center for Vital Longevity (CVL), has found stress hormones, which are elevated in the brain when a person is harassed, inhibit brain activity. And if the hormone levels are chronically elevated, it can lead to the development of neurological disease.
Rodrigue and her colleagues looked specifically to see if people with both hypertension and a common gene (APOE-e4) associated with Alzheimer´s disease had more brain plaque (amyloid protein) buildup associated with that neurological disease.
Many scientists believe the buildup of this amyloid protein is the first symptom of Alzheimer´s and may show up a decade or more before symptoms of memory impairment and other cognitive difficulties begin.
New brain scanning techniques allow scientists to see amyloid plaque in living brains of healthy adults. Before this new method, plaque buildup had only been observed through autopsy. But between autopsy and the new brain scans experts know at least 20 percent of normal older adults carry elevated levels of the protein in their brain.
"I became interested in whether hypertension was related to increased risk of amyloid plaques in the brains of otherwise healthy people," Rodrigue said in a statement. "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 believed hypertension and the presence of the APOE-e4 gene could lead to significantly higher levels of amyloid in otherwise healthy adults.
Sara Bengtsson, a PhD student from Umea University in Sweden, found similar evidence in a study of mice.
Bengtsson found mice with higher levels of the stress hormone in their brains suffered impaired learning and memory. These mice also had increased brain levels of beta-amyloids.
Her study found high levels of these amyloids are associated with malfunctioning brain synapses — the connectors between brain cells. It is believed to be the loss of these synapses that brings about memory loss and communication problems associated with neurological disease.
Bengtsson believes the effect of stress hormones on the brain could mean the difference between living independently and needing to be put into care.
However, since Bengtsson´s research was carried out on mice, her findings may not be viewed accordingly in a human subset, noted Dr. Simon Ridley, Head of Research at Alzheimer´s Research UK.
“Some research has already highlighted a possible link between chronic stress, cognitive decline and the development of Alzheimer´s, and further study in people is needed to fully investigate these links,” Ridley told Mail Online´s Emma Innes. “If we can better understand the risk factors for Alzheimer´s we can also empower people to make lifestyle changes to reduce their risk.”
Hence Rodrigue´s research, which was a comprehensive study of the aging brain in a large group of adults of all ages who were part of the comprehensive Dallas Lifespan Brain Study. Rodrigue recruited 147 participants (ages 30-89) to undergo cognitive testing, MRI and PET imaging, and use Amyvid, an injected compound that binds with amyloid proteins in the brain. This compound allowed scientists to visualize the amount of amyloid plaque buildup in the brain. The researchers also measured blood pressure at each visit.
Rodrigue classified participants as hypertensive if they reported a current diagnosis of hypertension or if their blood pressure exceeded the established criteria for diagnosis. The participants were divided into groups who were taking anti-hypertensive medications and those who were not medicated, but had shown blood pressure elevations consistent with a hypertensive diagnosis. And then the participants 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-e4 allele, a genetic variant of the gene associated with dementia.
The researchers found the unmedicated hypertensive adults who carried the genetic risk factor for Alzheimer´s showed much higher amyloid levels than all other groups. Adults on hypertensive drugs, even those with the genetic risk, had levels of amyloid plaque equivalent to participants without the risk factors.
Rodrigue said the study suggests controlling hypertension may significantly lower a person´s risk of developing amyloid deposits (even those with genetic risk) in middle-age and older adults. She noted long-term studies of many people are needed to be certain the use of hypertensive medications are the causal link in the decreases in amyloid deposits seen.
Still, the findings highlight the potential benefits of controlling hypertension earlier in life, indicating not only will it decrease the risk of stroke and heart disease, but that it may also halt cognitive decline.
Rodrigue said her team plans to continue long-term longitudinal follow-up studies with the participants to determine which proportion of the subjects eventually develop Alzheimer´s disease or dementia.
The study was funded by the National Institute on Aging and the Alzheimer´s Association. Avid Radiopharmaceutical provided doses of Amyvid that allowed the researchers to image the amyloid plaque with a PET scan.