Even at the earliest (preclinical) stage of AD, when the affected individuals remain cognitively intact with no apparent neurodegeneration, changes in the brain are already occurring. These changes include the accumulation of proteins called amyloid beta (Aβ) and tau.

There is a growing consensus that therapeutic intervention should be initiated at this stage for meaningful disease modification in AD. Thanks to evolving research on biomarkers related to AD pathology, it is now possible to identify the disease even at the preclinical stage before the occurrence of the first clinical symptoms.