Long before a diagnosis is spoken aloud, the brain may already be quietly rewriting itself — a process that research now suggests can begin a decade or two before dementia becomes clinically visible. The US National Institute on Aging and other researchers have traced this slow, silent progression, finding that what families often dismiss as ordinary forgetfulness or aging may carry deeper significance. Understanding that dementia is not a sudden arrival but a long becoming changes what we owe to our attention — and to one another.