It has been the tradition to confirm the presence of Alzheimer's disease during autopsy. However new guidelines proposed on Sunday by the U.S. National Institute on Aging and the Alzheimer's Association seek to distinguish between memory changes or dementia diagnosed by doctors when people are alive, and the changes pathologists can see in an autopsy.
These new guidelines hope to offer additional information about the disease that will help as scientists develop tests that measure biological changes in the brain, blood or spinal fluid to diagnose Alzheimer's at an earlier stage. This effort is supported by several companies, including Eli Lilly and Co, Bayer and General Electric Co. They are attempting on compounds to identify Alzheimer's-related brain changes on positron emission tomography or PET scans. Many other companies and researchers are working on other types of biomarkers as well.
Dr. Creighton Phelps of the National Institute on Aging's division of neuroscience, said in an interview at the Alzheimer's Association International Conference in Paris, “Someday biomarkers are probably going to replace pathology.” Pathologists now look in the brain for clumps of a protein called beta amyloid and a protein called tau to diagnose Alzheimer's disease. But studies have shown that people can die with lots of plaques and tangles in their brain and still have normal cognitive function. Phelps explained, “We know people die with Alzheimer's changes in the brain but they had no dementia.”
Bill Thies of the Alzheimer's Association said knowing the location of the plaques in a person's brain may provide clues about why some people develop dementia and others do not. For example if these protein deposits are clustered in memory centers of the brain that could cause more problems than if they are in other parts he explained.
According to the proposed guidelines, patients who have memory problems caused by the disease will be diagnosed with Alzheimer's dementia, or in milder cases, mild cognitive impairment (MCI) due to Alzheimer's dementia. The term Alzheimer's disease will be used to refer to the underlying changes in the pathology, Phelps said. He added, “Classically, it's all been one big pool but they are not equivalent…You might have something on a slide that doesn't match what the person was like in life.” Phelps also explained that dementia can be caused by many diseases, including vascular disease, so it is important to be clear about what is causing the problem.
Earlier this year, the NIA, part of the National Institutes of Health, and the Alzheimer's Association issued new diagnostic criteria to help doctors better classify patients who are tested for signs of dementia. The proposed pathology guidelines, which are part of that process, will be available for public comment until September 1. Phelps said he hopes final guidelines will published in January 2012.
Alzheimer's, the memory-robbing progressive brain disease, is believed to affect more than 5.4 million people in the U.S. and is projected to be diagnosed in as many as 16 million by 2050, according to the Alzheimer's Association. Available treatment options are limited to drugs that merely treat symptoms; nothing yet can slow or reverse the disease.
Antipsychotics for dementia associated with elevated risks of serious adverse outcomes