Neuropsychiatric Symptom Severity, Caregiver Distress, and Caregiver Burden in Dementia Outpatients.

BACKGROUND: Neuropsychiatric symptoms are major contributors to caregiver burden in older adults with cognitive disorders. The Neuropsychiatric Inventory Questionnaire (NPI-Q) measures both symptom severity and caregiver distress, but whether caregiver distress conveys information beyond symptom severity remains unclear. METHODS: We conducted a cross-sectional study of consecutive first-visit patients at a dementia outpatient clinic in Japan between April 2020 and October 2025. Caregiver burden was assessed with the 22-item Zarit Burden Interview (ZBI-22). Excess distress was defined as the residual from a linear regression of NPI-Q distress on NPI-Q severity. Associations with ZBI-22 were examined using multivariable linear regression adjusted for demographic and clinical covariates. Missing data were handled with multiple imputation by chained equations. RESULTS: The cohort included 538 participants (mean age 81.4 ± 8.6 years; 61.5% female). In complete-case analyses (n = 400), excess distress was independently associated with higher ZBI-22 scores (B = 1.08, 95% confidence interval 0.46-1.71, p < 0.001) and improved model fit beyond severity alone (adjusted R² 0.289 to 0.308). Multiple-imputation analyses were similar. In analyses restricted to spouse and child caregivers (n = 326), child caregivers had higher burden than spouse caregivers, but interaction by caregiver relationship was not supported. CONCLUSIONS: Caregiver distress beyond neuropsychiatric symptom severity was independently associated with caregiver burden in this dementia outpatient cohort. Assessing excess distress may provide supplementary information during the initial outpatient evaluation of caregiver burden.