New Finding Could Mark Shift in Alzheimer's Research
THURSDAY, April 29 (HealthDay News) -- New research could change the way scientists view the causes -- and potential prevention and treatment -- of Alzheimer's disease.
A study published online this month in the Annals of Neurology suggests that "floating" clumps of amyloid beta (abeta) proteins called oligomers could be a prime cause of the disorder, and that the better-known and more stationary amyloid-beta plaques are only a late manifestation of the disease.
"Based on these and other studies, I think that one could now fairly revise the 'amyloid hypothesis' to the 'abeta oligomer hypothesis,'" said lead researcher Dr. Sam Gandy, a professor of neurology and psychiatry and associate director of the Alzheimer's Disease Research Center at Mount Sinai School of Medicine in New York City.
The new study could herald a major shift in Alzheimer's research, another expert said.
Maria Carrillo, senior director of medical and scientific relations at the Alzheimer's Association, said that "we are excited about the paper. We think it has some very interesting results and has potential for moving us in another direction for future research."
According to the Alzheimer's Association, more than 5.3 million Americans now suffer from the neurodegenerative illness, and it is the seventh leading cause of death. There is no effective treatment for Alzheimer's, and its origins remain unknown. For decades, research has focused on a buildup of amyloid beta plaques in the brain, but whether these deposits are a cause of the disease or merely a neutral artifact has remained unclear.
The new study looked at a lesser-known factor, the more mobile abeta oligomers that can form in brain tissue. In their research, Gandy's team first developed mice that only form abeta oligomers in their brains, and not amyloid plaques.
Based on the results of tests gauging spatial learning and memory, these mice were found to be impaired by Alzheimer's-like symptoms.
Next the researchers inserted a gene that would cause the mice to develop both oligomers and plaques.
Similar to the oligomer-only rodents, these mice "were still memory impaired, but no more memory impaired for having plaques superimposed on their oligomers," Gandy said.
Another result further strengthened the notion that oligomers were the prime cause of Alzheimer's in the mice.
"We tested the mice and they lost memory function, and when they died, we measured the oligomers in their brains," Gandy said. "Lo and behold, the degree of memory loss was proportional to the oligomer level," he said.
Gandy noted that PET scans are not able to detect oligomers in the human brain, but they do see amyloid plaques. This could help explain why recent trials of the experimental Alzheimer's drug bapineuzumab showed a reduction in plaques, but no improvement in patients' cognitive function, Gandy said.
Bapineuzumab is targeted to amyloid plaques. Whether the drug also affected the oligomers is not known, Gandy said, because the PET scans could not see them. "We don't even know whether bapineuzumab 'sees' them," he said.
The new study could help change the focus of ongoing research. "Our new 'oligomer only' mice may enable the development of imaging agents and drugs that lower oligomer levels without having plaques around to muddy the picture," Gandy said.
Researchers have long been trying to figure out the stages that lead up to plaques and tangles, Carrillo noted. "We [now] know that plaques and tangles are really the end stage of this disease," she said.
Oligomers are "toxic clumps" that could be the cause of Alzheimer's disease, Carrillo said. This study confirms for the first time that these toxic clumps are a cause of memory problems, she said.
Carrillo noted that these results also confirm that the disease starts developing 10 to 15 years before it is diagnosed. This understanding could lead to new ways of diagnosing and treating the illness, she added.
"Perhaps future therapeutics attacking oligomers instead of plaques would be a strategy," Carrillo said.
One expert did have some reservations about that possibility, however.
"The larger unresolved issue is how these oligomers relate to people where plaques accumulate many years prior to disease onset," said Greg M. Cole, professor of medicine and neurology and associate director of the UCLA Alzheimer's Center. "One would expect the little oligomer aggregates to arise prior to the bigger plaque aggregates, that is, decades before important memory problems [surface]."
That could mean that "targeting oligomers may work best for prevention," rather than the treatment of existing disease, he said. "Ongoing efforts to track and specifically target the oligomers in clinical trials with memory deficit patients should soon tell us how much good we can do hitting the oligomers. It may be a huge success or too little, too late."
For more information on Alzheimer's disease, visit the Alzheimer's Association.
Mediterranean Diet Helps Protect Aging Brain
TUESDAY, April 27 (HealthDay News) -- Eating a Mediterranean diet may help keep your brain healthy as you age, findings from an ongoing study show.
"This diet emphasizes vegetables, fruits, fish, olive oil, lower meat consumption, and moderate wine and non-refined grain intake," study author Dr. Christy Tangney, of Rush University Medical Center in Chicago, said in a news release from the American Society for Nutrition.
Rather than asking people to avoid certain foods, the study found data that "adults over age 65 should look to include more olive oil, legumes, nuts, and seeds in their diet in order to improve their recall times and other cognitive skills, such as identifying symbols and numbers," Tangney said.
The study included 4,000 adults aged 65 and older who were given a series of tests to examine their cognitive (or thinking) skills every three years over a 15-year period. Those who scored highest in following a Mediterranean diet were least likely to suffer cognitive decline, the study authors found.
"We [also] want older adults to remember that physical activity is an important part of maintaining cognitive skills," Tangney added.
The findings were slated to be presented Monday at the Experimental Biology 2010 meeting in Anaheim, Calif.
The AGS Foundation for Healthy Aging offers cognitive vitality tips for older adults.
Imaging Costs Soar for Medicare Cancer Patients
TUESDAY, April 27 (HealthDay News) -- Among cancer patients on Medicare, the costs for medical scans have increased twice as fast as overall costs for cancer care, Duke University researchers report.
"There has been a significant increase in the utilization of imaging services for cancer patients since 1999, especially advanced imaging services such as CAT scans, MRI and PET scans -- the most expensive studies," said lead researcher Dr. Kevin A. Schulman, a professor of medicine and business administration and associate director of the Duke Clinical Research Institute.
Schulman noted that more scans do not necessarily result in better treatment or outcomes. Patients, he added, can play a role in limiting the number of unnecessary scans.
"It's OK to ask your physicians why they are ordering an imaging test and how you might benefit from the result," he said.
The Duke report is published in the April 28 issue of the Journal of the American Medical Association.
For the study, Schulman's group collected data on imaging costs of 100,954 cancer patients on Medicare who were diagnosed with breast, lung, prostate or colon cancer, leukemia or lymphoma between 1999 and 2006.
The researchers found that while overall costs for treating these patients rose 2 percent to 5 percent a year, the cost for imaging scans increased between 5 percent and 10 percent.
Although the costs for imaging increased faster than costs for overall care, imaging costs make up only about 6 percent of Medicare costs for each patient, the researchers noted.
The most growth was seen in the number of PET scans. The average annual number of PET scans grew from 36 percent to 53 percent, but they still remain the least-used scanning technology. However, these scans are the most expensive, running as much as six times higher than CT scans.
When PET scans were first introduced, Medicare did not pay for them, but by 2005 about 50 percent of patients with lung cancer and lymphoma were getting one or more PET scans, Schulman noted.
In 1999, patients diagnosed with lung cancer had about 21 imaging scans during the first two years of treatment. By 2006, that had increased to 24.
The highest imaging costs were for patients with lung cancer and lymphoma, averaging $3,000 during the first two years of treatment, the researchers found.
In addition, bone density studies increased in popularity. In fact, the number of breast cancer patients getting bone density studies almost doubled by 2005, with about one-third of all patients receiving one or more scans.
Michael T. French, a professor of economics, epidemiology and public health at the University of Miami, isn't surprised that these costs have gone up so dramatically.
"Imaging has advanced considerably in recent years," he said. "So, it's logical that it would be used more often, and along with the higher costs of increased use are the costs of improved technology."
French thinks that some of the increased use of imaging is related to increased reimbursement and competitiveness among hospitals. "Is there excessive use of imaging to improve profits? Yes," French said.
In addition, there is a defensive aspect to the increased use of imaging, French said. "If the technology is present and physicians don't use it, then if something happens to the patient there is a possibility for a lawsuit," he said.
The bottom-line question is how imaging is being used, French said. "It's a question of whether it's wasteful or whether it's higher cost to produce better outcomes," French said. "Right now, we don't know what all this leads to in terms of better outcomes."
A group representing the medical imaging industry believe they have an answer to that question, however.
The Access to Medical Imaging Coalition point to a recent study, conducted by Columbia University professor of business Frank Lichtenberg and based on data from the National Cancer Institute and Thomson Medstat. That study found that, "cancer imaging innovation accounted for 40 percent of the reduction in U.S. cancer deaths between 1996 and 2006, making it likely the largest single contributor to decreased cancer mortality during this time period," according to a news release from the coalition.
"Given that previous researchers have equated a one percent reduction in cancer mortality to nearly $500 billion in health care savings per year," the findings suggests a role for medical imaging in cutting health care costs, the group said.
For more information on cancer, visit the American Cancer Society.