Development of the J apanese Version of the A lzheimer's Disease Cooperative Study—Activities of Daily Living in Mild Cognitive Impairment Scale

ABSTRACT Background Assessment scales to detect subtle declines in activities of daily living (ADL) among patients with mild cognitive impairment (MCI) are needed for early diagnosis and support. This study examined the psychometric properties of the Japanese version of the Alzheimer's Disease Cooperative Study‐Activities of Daily Living for Mild Cognitive Impairment (ADCS‐MCI‐ADL‐J), an ADL assessment scale adapted for patients with early‐stage Alzheimer's disease (AD). Methods This multisite study recruited patients with MCI due to AD or mild AD dementia (ADD), and healthy controls (HC) between March 2024 and March 2026. Reliability (internal consistency, inter‐rater reliability, and test–retest reliability) and validity (discriminative, concurrent, convergent, and construct validities) were analysed as psychometric properties. As an interpretability analysis, we also checked the score distributions of the ADCS‐MCI‐ADL‐J to investigate a ceiling effect compared with other existing ADL assessment scales. Results A total of 102 participants were included in the analysis (HC, n = 30; MCI due to AD, n = 37; mild ADD, n = 35). Sixty participants (58.8%) were female and the overall mean age (standard deviation) was 72.6 (9.1). The Cronbach's α for the ADCS‐MCI‐ADL‐J was 0.893, indicating acceptable internal consistency. The inter‐rater and test–retest reliabilities were excellent, indicated by intraclass correlation coefficients of 0.917 and 0.915, respectively. Areas under the curve were 0.937 for MCI versus HC and 0.859 for MCI versus mild ADD. The ADCS‐MCI‐ADL‐J significantly distinguished MCI due to AD from HC and mild ADD. The ADCS‐MCI‐ADL‐J score was significantly correlated with other ADL scales and the severity of dementia, cognitive impairment, and neuropsychiatric symptoms. The ADCS‐MCI‐ADL‐J was divided into three factors. The ADCS‐MCI‐ADL‐J scores showed a wider distribution without a ceiling effect compared to other existing scales. Conclusions This study examined several psychometric properties of ADCS‐MCI‐ADL‐J. This assessment scale is useful for reliably detecting subtle declines in ADL at the MCI stage. Trial Registration UMIN‐CTR: UMIN000055015