On the left is a PET scan showing normal levels of glucose metabolism, indicated in yellow and red. The levels of glucose metabolism in the brain are decreased in patients with mild cognitive impairment (middle) and with Alzheimer's disease (right). Courtesy of Cindee Madison and Susan Landau, UC Berkeley.
While legislators stake out their positions on health care reform in Washington, thousands of researchers from across the globe have convened in Vienna to address a disease that could collapse our health care system: Alzheimers. Today there are an estimated 5.3 million Americans living with Alzheimer's disease (AD). With the first baby boomers on the cusp of Medicare eligibility, experts predict there will be nearly a half a million new cases of AD each year. And studies have shown that patients with AD cost the Medicare system three times as much as those without the disease.
At the Alzheimer's Association 2009 International Conference on Alzheimer's Disease in Vienna, most of the news has centered around prevention and early detection. "By the time a patient is diagnosed with Alzheimer's disease, there is usually little one can do to stop or reverse the decline," said Dr. William Jagust, a faculty member of UC Berkeley's Helen Wills Neuroscience Institute. "Researchers are trying to determine whether treating patients before severe symptoms appear will be more effective, and that requires better diagnostic tools than what is currently available."
Jagust and his collegues at Berkeley have been searching for an early warning system to help detect Alzheimer's before cognitive signs of impairment are obvious. As they reported Tuesday, July 14th at the conference in Vienna, they looked at a series of measurements that had shown promise as early detectors of AD, including the volume of the hippocampous, the presence of a gene that has been linked to increased risk of Alzheimers and certain proteins in cerbrospinal fluids. "What's really novel about our study is that we evaluated all of these biomarkers in the same subjects, so we could more easily compare the predictive value of any one measure over the others," said lead author, Susan Landau, a post-doctoral fellow at UC Berkeley's Helen Wills Neuroscience Institute. "The Auditory-Verbal Learning Test, which measures memory recall ability, and the PET scans measuring glucose metabolism were the two markers that clearly stood out over the others." In fact, the research found that among 85 participants in the study with mild cognitive impairment, those with low scores on a memory recall test and low glucose metabolism in particular brain regions, had a 15-fold greater risk of developing Alzheimer's disease within two years, compared with the others in the study.
The researchers pointed out that other measurements - in particular, hippocampus volume and the cerebrospinal fluid markers - also showed promise in predicting disease progression. However, when considering all the measurements together, PET scans and memory recall ability were the most consistent predictors. The researchers expect to have more complete information about which measures serve as the best predictors in a year as they continue to gather data for this ongoing study.An earlier study led by Jagust, a professor with joint appointments at UC Berkeley's School of Public Health and the Lawrence Berkeley National Laboratory, found that PET scans and magnetic resonance imaging (MRI) could detect neurological changes in asymptomatic people who subsequently developed dementia or mental impairment, although it was too soon to say if those people would go on to develop Alzheimer's.The research is part of the nationwide Alzheimer's Disease Neuroimaging Initiative, a 60-center study funded by the National Institute on Aging. The ultimate goal of the initiative is to find a biomarker for Alzheimer's that would predict individuals who will later develop Alzheimer's disease. Ideally, this marker would be identifiable very early, even in individuals who do not yet show signs of mental impairment.
