How far back do things present themselves before we get an official diagnosis?

We know that amyloid accumulates in the brain 15-20 years before people develop dementia. At this stage, intervention is possible. There are also different markers on the brain that accumulate at different times. Tau proteins accumulate in the brain much earlier to when people actually develop memory problems. We see changes in the brain’s glucose utilization, where the brain doesn’t use glucose very well which can be identified early on.