For most of the last century, Alzheimer's disease has been understood as a single condition with a single cause. The evidence increasingly suggests that is the wrong framework. Alzheimer's is not one disease. It is many, and that changes everything about how we approach it.

One of the most damaging myths in medicine is that cognitive decline is simply what ageing looks like. The neuroscience tells a different story. The brain retains the ability to change throughout life - what varies is not the capacity itself, but the conditions that support or suppress it.