Why has a decade with untold millions of dollars in research based on the amyloid hypothesis of Alzheimer’s yielded no clinical benefit for patients? One possible answer is that by the time amyloid is seen on PET scans, medications that are able to clear it from the brain do not improve brain function. Two new studies also weigh in on this question.
One autopsy study of a large number of Alzheimer’s disease patients concluded that the primary cause of cognitive decline and memory loss was more likely accumulation of tau (neurofibrillary tangles) than amyloid plaques.
The second concluded that declines in memory and hippocampal volume occur earlier than findings of abnormal amyloid on PET scans. Memory and hippocampal volume, the hippocampus being a critical area of the brain in memory, worsen continuously from age 30 before abnormal amyloid PET appears. The lead author concludes that these declines are a fundamental characteristic of typical aging.
Intensive research into the cause of Alzheimer’s continues, but the target may be changing.
See: (1) Brain, March 23, 2015; (2) JAMA Neurology, March 16, 2015.
Jack Florin, MD
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