A decade of disappointing clinical trial results for Alzheimer disease (AD)-modifying therapies in people suggests that treatment should be targeted at earlier stages in the disease—even before overt symptoms arise.
Profound brain alterations—such as accumulation of the protein fragment called beta-amyloid—are found 10 to 20 years before dementia or even mild cognitive impairment is diagnosed. Alzheimer disease investigators estimate that by the time memory begins to erode and other cognitive problems emerge, too much damage has occurred in the brain to be reversed by the experimental treatments.
Friedrich MJ. Researchers Test Strategies to Prevent Alzheimer Disease. JAMA. 2014;311(16):1596-1598. doi:10.1001/jama.2014.3891