A Postmarketing Study of LEQEMBI in United Kingdom (UK) Participants With Alzheimer's Disease (AD)

The primary purpose of the study is to describe the incidence and severity of known adverse events (AEs), including Amyloid-Related Imaging Abnormalities Oedema/Effusion (ARIA-E), Amyloid-Related Imaging Abnormalities-Microhemorrhage and Haemosiderin Deposit (ARIA-H), intracerebral hemorrhage greater than (\>) 1 centimeter (cm) in diameter, and anaphylaxis (stratified by apolipoprotein E4 variant \[APOE4\] genotype, concomitant antithrombotic therapy, and comorbid Cerebral Amyloid Angiopathy \[CAA\]), of LEQEMBI in routine clinical practice.

Inclusion Criteria: * The participant (and/or legally authorised representative) has provided written informed consent to participate in the Post-Authorisation Safety Study (PASS) and for use of their protected health information (PHI). * The participant is registered in the Controlled Access Programme (CAP) and has been prescribed LEQEMBI. Exclusion Criteria: -Participation or planning to participate in randomised controlled trials (RCTs) for mild cognitive impairment (MCI) or AD, and patients who have had prior exposure to anti-amyloid monoclonal antibody (mAb) treatment including prior use of lecanemab.