Alzheimer's disease and dementia can now be detected early and treated with personalized multimodal approaches—combining anti-amyloid therapies, biomarker screening, hormone replacement, and brain stimulation—that may stabilize or even reverse cognitive decline in some patients, challenging decades of irreversible decline dogma. Dementia exists on a spectrum rather than discrete diagnoses; most patients have mixed pathology combining Alzheimer's, vascular disease, and Lewy body features requiring individualized treatment strategies.