Key Inclusion Criteria:  Participant has a diagnosis of Alzheimer's Disease (AD) and is prescribed aducanumab-avwa by their treating physician. Participant's treating physician has made the decision to initiate aducanumab-avwa prior to participant inclusion and independently of the purpose of the study.  Key Exclusion Criteria:  Participant concurrently participates in any interventional clinical study. Participant has ever been treated with aducanumab-avwa at a dose of 3 milligrams per kilogram (mg/kg) or greater prior to signing ICF. Participant has ever been treated with aducanumab-avwa and discontinued treatment prior to signing ICF.  NOTE: Other protocol defined Inclusion/Exclusion criteria may apply