Introduction: Lecanemab, an anti-amyloid-beta antibody, is approved in over 40 countries. Patient demographic data exist for the US but are limited elsewhere. This study examined early real-world lecanemab use in Japan.
Methods: Using claims data from 18 municipalities, we identified patients prescribed lecanemab between December 2023 and September 2024. The study outcome was the discontinuation rate, with discontinuation defined as a ≥42-day prescription gap. Covariates included age, sex, long-term care certification, municipality size, comorbidities, Mini-Mental State Examination (MMSE) score, and Clinical Dementia Rating (CDR).
Results: We identified 123 lecanemab recipients (median age: 76 years, interquartile range: 73-79 years; women: 73.2%). Most had mild impairment: 60.9% with MMSE ≥24 and 79.3% with CDR 0.5. The discontinuation rate was 1.04/100 person-months, with most occurring within 1.5 months.
Discussion: In this first Asian report, lecanemab was mainly prescribed to older women with milder cognitive impairment. Early discontinuation may reflect cautious adoption in Japan.
Keywords: Alzheimer's disease; dementia; discontinuation rate; lecanemab; real‐world evidence.
© 2026 The Author(s). Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring published by Wiley Periodicals LLC on behalf of Alzheimer's Association.