Impaired learning linked to family history of Alzheimer's
July 10, 2019
Science Daily/eLife
Adults with a first-degree relative with Alzheimer's disease perform more poorly on online paired-learning tasks than adults without such a family history, and this impairment appears to be exacerbated by having diabetes or a genetic variation in the apolipoprotein E (APOE) gene linked to the disease.
The findings, published on Tuesday in eLife, may help identify people who have increased risk for developing Alzheimer's disease and could uncover new ways to delay or prevent the disease.
"Identifying factors that reduce or eliminate the effect of a family history of Alzheimer's disease is particularly crucial since there is currently no cure or effective disease-slowing treatments," says lead author Joshua Talboom, PhD, a Postdoctoral Fellow at the Translational Genomics Research Institute in Arizona, US.
Having a family history of Alzheimer's disease is a well-known risk factor for developing the condition, but the effects on learning and memory throughout a person's life are less clear. Some studies have been conducted in this area, but most have been too small to draw significant conclusions.
To enable a larger study, Talboom and colleagues created an easy-to-use website, http://www.mindcrowd.org, that participants could log on to and complete a memory test. Participants were asked to learn 12-word pairs and were then tested on their ability to complete the missing half of the pair when presented with one of the words.
The 59,571 individuals who participated were also asked to answer questions about their sex, education, age, language, country and health, including a question about whether one of their parents or siblings had been diagnosed with Alzheimer's disease. Those with a family history of Alzheimer's were able to match about two and one-half fewer word pairs than individuals without a family history. Having diabetes appeared to compound the learning impairments seen in individuals with a family history.
A subset of 742 participants who had a close relative with Alzheimer's submitted a sample of dried blood or saliva that the researchers tested for a genetic variation in the APOE gene linked to the disease. "The APOE genotype is an important genetic factor that influences memory, and we found that those with the variation performed worse on the memory test than those without the variation," Talboom explains.
Some characteristics, however, appeared to protect against memory and learning impairments in people with a family history of Alzheimer's disease. Participants with higher levels of education experience less of a decline in scores on the learning and memory test than people with lower levels of education, even when they have a family history of the disease. Women also appear to fair better despite having Alzheimer's disease risk factors.
"Our study supports the importance of living a healthy lifestyle, properly treating diseases such as diabetes, and building learning and memory reserve through education to reduce the cognitive decline associated with Alzheimer's disease risk factors," concludes senior author Matthew Huentelman, Professor of Neurogenomics at the Translational Genomics Research Institute, Arizona.
https://www.sciencedaily.com/releases/2019/07/190710131936.htm
Diabetes treatment may keep dementia, Alzheimer's at bay
Study finds progression of dementia and Alzheimer's signature tangles are much faster in people with untreated diabetes
March 25, 2019
Science Daily/University of Southern California
A new study comparing people with diabetes, prediabetes and normal blood sugar finds that diabetes, left untreated, could mean a higher likelihood of developing dementia, including Alzheimer's disease.
Patients on medication for type 2 diabetes may be keeping Alzheimer's disease away.
USC Dornsife psychologists have found that those patients with untreated diabetes developed signs of Alzheimer's disease 1.6 times faster than people who did not have diabetes.
The study was published March 4 in the journal Diabetes Care.
"Our findings emphasize the importance of catching diabetes or other metabolic diseases in adults as early as you can," says Daniel A. Nation, a psychologist at USC Dornsife College of Letters, Arts and Sciences. "Among people with diabetes, the difference in their rate of developing the signs of dementia and Alzheimer's is clearly tied somehow to whether or not they are on medication for it."
Nation says that this study may be the first to compare the rate of developing the pathology for Alzheimer's disease and dementia among people with normal glucose levels, with pre-diabetes, or people with type 2 diabetes -- both treated and untreated.
For the study, the scientists were comparing the "tau pathology" -- the progression of the brain tangles that are the hallmark of Alzheimer's disease. When the tangles combine with sticky beta-amyloid plaques -- a toxic protein -- they disrupt signals between brain cells, impairing memory and other functions.
Nation and Elissa McIntosh, a USC Dornsife Ph.D. doctoral candidate in psychology, analyzed data collected by the Alzheimer's Disease Neuroimaging Initiative on 1,289 people age 55 and older. Data included biomarkers for diabetes and vascular disease, brain scans and a range of health indicators, including performance on memory tests.
For some participants, Nation and McIntosh were able to analyze 10 years' worth of data, while for others, they had one or four years.
Among 900 of those patients, 54 had type 2 diabetes but were not being treated, while 67 were receiving treatment.
Most people in the study -- 530 -- had normal blood sugar levels while 250 had prediabetes (hyperglycemia).
The researchers compared, among the different diabetic patient categories, the brain and spinal fluid test results that can indicate signs of amyloid plaques and the brain tangles.
"It is possible that the medicines for treating diabetes might make a difference in the progression of brain degeneration," Nation says. "But it's unclear how exactly those medications might slow or prevent the onset of Alzheimer's disease, so that is something we need to investigate."
Increasingly, scientists regard Alzheimer's disease as the result of a cascade of multiple problems, instead of triggered by one or two. The compounding factors range from pollution exposure and genetics (the ApoE4 gene, for instance) to heart disease and metabolic disease.
The study was supported by National Institutes of Health grants R21-AG-055034, P01-AG-052350 and P50-AG-005142 and Alzheimer's Association grant AA-008369.
The Alzheimer's Disease Neuroimaging Initiative is supported by the National Institute on Aging and the National Institute of Biomedical Imaging and Bioengineering, as well as other public and private partners.
https://www.sciencedaily.com/releases/2019/03/190325122011.htm