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People With Early Alzheimer’s Disease May be More Likely to Have Lower BMI
St Paul, Minnesota—Studies have shown that people who are overweight in middle age are more likely to develop Alzheimer’s disease decades later than people at normal weight, yet researchers have also found that people in the earliest stages of Alzheimer’s disease are more likely to have a lower body mass index (BMI). A current study examines this relationship between Alzheimer’s disease and BMI.
The study, published in the November 22, 2011, print issue of Neurology, the medical journal of the American Academy of Neurology, examined 506 people with advanced brain imaging techniques and analyses of cerebrospinal fluid to look for biomarkers for Alzheimer’s disease, which can be present years before the first symptoms begin. Neuroimaging initiative included people with no memory problems, people with mild cognitive impairment, or mild memory problems, and people with Alzheimer’s disease.
The study found that in people with no memory or thinking problems and in people with mild cognitive impairment, those who had the Alzheimer’s biomarkers were also more likely to have a lower BMI than those who did not have the biomarkers.
For example, 85% of the people with mild cognitive impairment who had a BMI below 25 had signs of the beta-amyloid plaques in their brains that are a hallmark of the disease, compared to 48% of those with mild cognitive impairment who were overweight. The relationship was also found in people with no memory or thinking problems.
“These results suggest Alzheimer’s disease brain changes are associated with systemic metabolic changes in the very earliest phases of the disease,” said the study author Jeffrey M. Burns, MD, MS, of the University of Kansas School of Medicine in Kansas City and a member of the American Academy of Neurology. “This might be due to damage in the area of the brain called the hypothalamus that plays a role in regulating energy metabolism and food intake. Further studies should investigate whether this relationship reflects a systemic response to an unrecognized disease or a long-standing trait that predisposes a person to developing the disease.” (Source: EurekAlert! A service of AAAS and The American Academy of Neurology.)
Eating Fish Reduces Risk of Alzheimer’s Disease
Chicago—People who eat baked or broiled fish on a weekly basis may be improving their brain health and reducing their risk of developing mild cognitive impairment (MCI) and Alzheimer’s disease, according to a study presented today at the annual meeting of the Radiological Society of North America (RSNA).
“This is the first study to establish a direct relationship between fish consumption, brain structure and Alzheimer’s risk,” said Cyrus Raji, MD, PhD, from the University of Pittsburgh Medical Center and the University of Pittsburgh School of Medicine. “The results showed that people who consumed baked or broiled fish at least one time per week had better preservation of gray matter volume on MRI in brain areas at risk for Alzheimer’s disease.”
Alzheimer’s disease is an incurable, progressive brain disease that slowly destroys memory and cognitive skills. According to the National Institute on Aging, as many as 5.1 million Americans may have Alzheimer’s disease. In MCI, memory loss is present but to a lesser extent than in Alzheimer’s disease. People with MCI often go on to develop Alzheimer’s disease.
For the study, 260 cognitively normal individuals were selected from the Cardiovascular Health Study. Information on fish consumption was gathered using the National Cancer Institute Food Frequency Questionnaire. There were 163 patients who consumed fish on a weekly basis, and the majority ate fish 1 to 4 times per week. Each patient underwent 3D volumetric MRI of the brain. Voxel-based morphometry, a brain mapping technique that measures gray matter volume, was used to model the relationship between weekly fish consumption at baseline and brain structure 10 years later. The data were then analyzed to determine whether the gray matter volume preservation associated with fish consumption reduced the risk for Alzheimer’s disease. The study controlled for age, gender, education, race, obesity, physical activity, and the presence or absence of apolipoprotein E4 (ApoE4), a gene that increases the risk of developing Alzheimer’s.
Gray matter volume is crucial to brain health. When it remains high, brain health is being maintained. Decreases in gray matter volume indicate that brain cells are shrinking.
The findings showed that consumption of baked or broiled fish on a weekly basis was positively associated with gray matter volumes in several areas of the brain. Greater hippocampal, posterior cingulate, and orbital frontal cortex volumes in relation to fish consumption reduced the risk for 5-year decline to MCI or Alzheimer’s by almost 5-fold.
“Consuming baked or broiled fish promotes stronger neurons in the brain’s gray matter by making them larger and healthier,” Dr Raji said. “This simple lifestyle choice increases the brain’s resistance to Alzheimer’s disease and lowers risk for the disorder.”
The results also demonstrated increased levels of cognition in people who ate baked or broiled fish.
“Working memory, which allows people to focus on tasks and commit information to short-term memory, is one of the most important cognitive domains,” Dr Raji said. “Working memory is destroyed by Alzheimer’s disease. We found higher levels of working memory in people who ate baked or broiled fish on a weekly basis, even when accounting for other factors, such as education, age, gender and physical activity.”
Eating fried fish, on the other hand, was not shown to increase brain volume or protect against cognitive decline. (Source: EurekAlert! A service of AAAS and The Radiological Society of North America.)
Is it Alzheimer’s Disease or Another Dementia? Marker May Give More Accurate Diagnosis
St Paul, Minnesota—New research finds a marker used to detect plaque in the brain may help doctors make a more accurate diagnosis between 2 common types of dementia—Alzheimer’s disease and frontotemporal lobar degeneration (FTLD). The study is published in the November 30, 2011, online issue of Neurology, the medical journal of the American Academy of Neurology.
“These two types of dementia share similar symptoms, so telling the two apart while a person is living is a real challenge, but important so doctors can determine the best form of treatment,” said the study author Gil D. Rabinovici, MD, of the University of California San Francisco Memory and Aging Center and a member of the American Academy of Neurology.
For the study, 107 people with early-onset Alzheimer’s disease or FTLD underwent a brain positron emission tomography (PET) scan using a PIB marker, which detects amyloid or plaque in the brain that is the hallmark of Alzheimer’s disease but not related to FTLD. The participants underwent another PET scan using a fluorodeoxyglucose (FDG) marker, which detects changes in the brain’s metabolism and is currently used to help differentiate between the 2 types of dementia.
The study found the PIB PET scan performed at least as well as the FDG PET scan in differentiating between Alzheimer’s disease and FTLD but had higher sensitivity and better accuracy and precision of its qualitative readings. The study found PIB had a sensitivity of 89.5% compared to 77.5% for FDG.
“While widespread use of PIB PET scans isn’t available at this time, similar amyloid markers are being developed for clinical use, and these findings support a role for amyloid imaging in correctly diagnosing Alzheimer’s disease versus FTLD,” said Rabinovici. (Source: EurekAlert! A service of AAAS and The American Academy of Neurology.)
Depression Increases Risk of Dementia in Patients With Type 2 Diabetes
Oakland, California, December 5, 2011—Depression in patients with diabetes is associated with a substantively increased risk of development of dementia compared to those with diabetes alone, according to researchers from the University of Washington and Kaiser Permanente.
The study, among the first (and largest to date) to examine all-cause dementia in diabetes patients with and without depression, appears on the current online issue of the Archives of General Psychiatry.
Patients with type 2 diabetes who also had depression had a doubling in risk of dementia during years 3 to 5 after initial screening, compared to patients with diabetes who did not have depression, said the study’s lead author Wayne Katon, MD, Professor and Vice Chair of the University of Washington, Department of Psychiatry and Behavioral Sciences. This study was supported by the National Institutes of Health-funded Diabetes & Aging Study, which focuses on the special health problems of older patients with diabetes, and its parent study, Diabetes Study of Northern California (DISTANCE) which collected surveys from more than 20 000 adults with diabetes who are patients from the Kaiser Permanente Northern California Diabetes Registry.
“Prior research has shown that both depression and diabetes are risk factors for dementia. This study suggests that having both of these illnesses occurring together is associated with an even greater risk,” said Kaiser Permanente researcher and senior author Rachel Whitmer, PhD.
“Since depression affects up to 20 percent of diabetic patients, it is critical to understand this relationship and further evaluate whether depression interventions have an impact on dementia risk in patients with diabetes,” explained Andrew J. Karter, PhD, coauthor from Kaiser Permanente Division of Research and principal investigator for the Diabetes & Aging and DISTANCE Studies. “Earlier onset of diabetes in patients with depression and greater risk of dementia in younger compared to older patients with depression and diabetes underscore the importance of evaluating the potential for early depression interventions to reduce the incidence of dementia,” Katon said.
Of the 20 188 consenting adults in the DISTANCE study, 19.6% of the patients with diabetes met the criteria for clinically significant depression.
Among patients with diabetes, depression is associated with poorer adherence to diet and exercise programs, increased smoking and poorer blood sugar control as well as psychobiologic changes such as increases in cortisol and increased sympathetic nervous system tone, which could worsen the course of diabetes and increase the risk of dementia associated with depression, they added. (Source: EurekAlert! A service of AAAS and The University of Washington.)
Study Participants at Risk for Alzheimer’s Want to Know Their Potential Fate
Ann Arbor, Michigan—If you had a family history of developing Alzheimer’s disease, would you take a genetic test that would give you more information about your chances?
“Definitely,” said Gloria VanAlstine, 60, and Joyce Smith, 79. The 2 women took a controversial genetic test of a gene called apolipoprotein E (APOE). APOE is a susceptibility gene where certain variants have been found to significantly increase a person’s risk of developing Alzheimer’s disease. Both women have a family history of Alzheimer’s, which increases the risk.
The genetic test was conducted as part of the Risk Evaluation and Education for Alzheimer’s disease Study (REVEAL), a series of clinical trials taking place at U-M School of Public Health, with other sites including Harvard University, Howard University, and the University of Pennsylvania.
APOE testing is controversial in the medical community because the variant is neither necessary nor sufficient to cause Alzheimer’s disease. This limitation, along with a general lack of treatment options for Alzheimer’s, has raised concerns that the genetic information could burden rather than benefit patients. There have been numerous consensus statements and articles against using APOE genotyping for predicting Alzheimer’s risk.
However, most of the study participants who took the test, including VanAlstine and Smith, wanted to learn about their APOE test results and were not overtly distressed by them, said Scott Roberts, Associate Professor in U-M SPH, and Coprincipal Investigator of REVEAL, along with Robert Green at Harvard University School of Medicine.
The National Society of Genetic Counselors and American College of Medical Genetics recently developed practice guidelines for genetic counseling and testing for Alzheimer’s disease. Roberts is one of the authors.
The guidelines provide clinicians with a framework for assessing their patients’ genetic risk for Alzheimer’s disease, identifying which individuals may benefit from genetic testing and providing the key elements of genetic counseling. Alzheimer’s disease is traditionally subdivided into early-onset and late-onset types. Early onset occurs before age 60 to 65 years and accounts for 1% to 5% of all cases, while late onset occurs after 60 to 65 years and is the predominant form. (Source: EurekAlert! A service of AAAS and The University of Michigan.)
Form and Function: New MRI Technique to Diagnose or Rule Out Alzheimer’s Disease
Two Penn Medicine Studies Articulate Efficacy of Noninvasive MRI Test for Alzheimer’s
Philadelphia—On the quest for safe, reliable, and accessible tools to accurately diagnose Alzheimer’s disease (AD), researchers from the Perelman School of Medicine at the University of Pennsylvania found a new way of diagnosing and tracking AD, using an innovative magnetic resonance imaging (MRI) technique called arterial spin labeling (ASL) to measure changes in brain function. The team determined that the ASL-MRI test is a promising alternative to the current standard, a specific PET scan that requires exposure to small amounts of a radioactive glucose analog and costs approximately 4 times more than an ASL-MRI. Two studies now appear in Alzheimer’s and Dementia, the journal of the Alzheimer’s Association and Neurology, the medical journal of the American Academy of Neurology.
The ASL-MRI can be used to measure neurodegenerative changes in a similar way that fluorodeoxyglucose positron-emission tomography (FDG-PET) scans are currently being used to measure glucose metabolism in the brain. Both tests correlate with cognitive decline in patients with AD.
“In brain tissue, regional blood flow is tightly coupled to regional glucose consumption, which is the fuel the brain uses to function. Increases or decreases in brain function are accompanied by changes in both blood flow and glucose metabolism,” explained John A. Detre, MD, Professor of Neurology and Radiology at Penn, senior author of the papers, who has worked on ASL-MRI for the past 20 years. “We designed ASL-MRI to allow cerebral blood flow to be imaged noninvasively and quantitatively using a routine MRI scanner.”
When AD is suspected, patients typically receive an MRI initially to look for structural changes that could indicate other medical causes, such as a stroke or brain tumor. Adding about 10 to 20 minutes to the test time, ASL can be incorporated into the routine MRI and capture functional measures to detect AD upfront, turning a routine clinical test (structural MRI) into both a structural and functional test.
“If ASL-MRI were included in the initial diagnostic work-up routinely, it would save the time for obtaining an additional PET scan, which we often will order when there is diagnostic uncertainty, and would potentially speed up diagnosis,” said David Wolk, MD, Assistant Professor of Neurology and Assistant Director of the Penn Memory Center, and a collaborator on this research.
The studies being reported this week show a comparison of ASL-MRI and FDG-PET in a group of Alzhiemer’s patients and age-matched controls. Cerebral blood flow and glucose metabolism were measured simultaneously by injecting the PET tracer during the MRI study. The data were then analyzed in 2 different ways.
In the first study, now online in Alzheimer’s and Dementia, ASL-MRI and FDG-PET images from 13 patients diagnosed with Alzheimer’s and 18 age-matched controls were analyzed by visual inspection. Independent, blinded review of the 2 tests by expert nuclear medicine physicians demonstrated similar abilities to rule out (sensitivity) and diagnose (specificity) Alzheimer’s. Neither ASL-MRI nor FDG-PET showed a clear advantage from quantitative testing.
In the second study, published in Neurology, the ASL-MRI and FDG-PET images were compared statistically at each location in the brain by computerized analysis. Data from 15 patients with AD were compared to 19 age-matched healthy adults. The patterns of reduction in cerebral blood flow were nearly identical to the patterns of reduced glucose metabolism by FDG-PET, both of which differed from the patterns of reduction in gray matter seen in AD.
“Given that ASL-MRI is entirely non-invasive, has no radiation exposure, is widely available and easily incorporated into standard MRI routines, it is potentially more suitable for screening and longitudinal disease tracking than FDG-PET,” said the Neurology study authors.
Additional studies will focus on larger sample sizes including patients with mild cognitive impairment and other kinds of neurodegenerative conditions. (Source: EurekAlert! A service of AAAS and The University of Pennsylvania School of Medicine.)
Why Bigger is Better When it Comes to Our Brain and Memory?
The hippocampus is an important brain structure for recollection memory, the type of memory we use for detailed reliving of past events. Now, new research published by Cell Press in the December 22 issue of the journal Neuron reveals the characteristics of the human hippocampus that allow scientists to use anatomical brain scans to form predictions about an individual’s recollection ability. The new research helps to explain why this relationship has been hard to find in the past and provides evidence for a possible underlying mechanism.
The hippocampus, a deep brain structure named for its curving sea horse shape, can be divided into anterior and posterior portions. Although research has generally linked smaller hippocampi with worse recollection in neuropsychological patients and during aging, this relationship has not held up among healthy young adults. “There is some evidence that extensive spatial memory acquisition leads to enlargement of the posterior hippocampus and a decrease in the anterior hippocampus,” explains the lead study author, Dr Jordan Poppenk who conducted the study at Baycrest’s Rotman Research Institute. “This suggested to us that the crucial predictor of individual differences in recollection ability might not be the overall size of the hippocampus but the separate contributions of the posterior and anterior segments of the hippocampus.”
Dr Poppenk and coauthor Dr Morris Moscovitch analyzed high-resolution magnetic resonance imaging brain scans of healthy adults who had participated in recollection memory tests. Better recollection was associated with a larger posterior hippocampus and a smaller anterior hippocampus. The overall size of the hippocampus did not predict recollection, as larger posterior hippocampi were offset by smaller anterior hippocampi. The researchers went on to show that the link between the posterior hippocampus and recollection depended on the interactions with other parts of the brain between the times that memories were learned and retrieved, particularly regions involved in perception, which form the basis of recollected experience.
“Our results show for the first time that the size of the posterior hippocampus, especially when expressed as a ratio to the size of the anterior hippocampus, reliably predicts recollection in healthy adults. This finding explains the longstanding failure to correlate the overall size of the hippocampus with memory,” concludes Dr Poppenk. “We also provide evidence that it is the functional connections, possibly related to memory consolidation, between the posterior hippocampus and other parts of the brain that may underlie enhanced memory recollection.” (Source: EurekAlert! A service of AAAS and Cell Press.)