Supplementary Material for: VALIDATION AND PSYCHOMETRIC PROPERTIES OF THE VIETNAMESE VERSION OF THE NEUROPSYCHIATRIC INVENTORY (V-NPI) IN COMMUNITY-DWELLING OLDER ADULTS WITH DEMENTIA

Abstract Background: Behavioral and psychological symptoms of dementia (BPSD) substantially contribute to functional decline and caregiver burden, yet culturally validated assessment tools remain limited in Vietnam. Objective: To translate, culturally adapt, and assess the reliability and selected aspects of construct validity of the Vietnamese version of the Neuropsychiatric Inventory (V-NPI). Methods: A cross-sectional study was conducted among 399 individuals with dementia and their caregivers in Hai Duong province. The V-NPI was administered alongside the Clinical Dementia Rating (CDR), Geriatric Depression Scale–15 (GDS-15), and Pittsburgh Sleep Quality Index (PSQI). Internal consistency, domain-level associations, and convergent and discriminant validity were assessed. Results: The V-NPI demonstrated excellent internal consistency for both the severity (Cronbach’s α = 0.91) and caregiver distress (Cronbach’s α = 0.93) subscales. Domain–total correlations ranged from 0.44 to 0.64, indicating moderate internal convergence alongside meaningful heterogeneity across symptom domains. The depression domain showed a modest correlation with the GDS-15, and the night-time disturbances domain showed a weak but statistically significant correlation with the PSQI, supporting domain-level construct validity. Neuropsychiatric symptoms were highly prevalent, with night-time disturbances (71.2%), apathy/indifference (60.2%), and depression/dysphoria (59.6%) being the most frequently reported domains. Conclusion: The V-NPI appears to be a reliable and culturally appropriate instrument for assessing BPSD and caregiver distress among older adults with dementia in Vietnam, supporting its use in both clinical practice and research. Keywords: dementia; neuropsychiatric symptoms; caregiver burden; validation; Vietnam.