Caregiver rating bias in mild cognitive impairment and mild Alzheimer's disease: impact of caregiver burden and depression on dyadic rating discrepancy across domains.

BACKGROUND Caregivers of individuals with dementia are biased in their rating of mental health measures of the care receiver. This study examines caregiver burden and depression as predictors of this bias for mild cognitive impairment and mild Alzheimer's disease in different domains. METHODS The sample consisted of 202 persons: 60 with mild cognitive impairment, 41 with mild Alzheimer's disease, and 101 caregivers. Discrepancy scores were calculated by subtracting the mean caregiver score from the respective mean patient score on the following assessment instruments: the Geriatric Depression Scale, Apathy Evaluation Scale, Bayer-Activities of Daily Living Scale, and Quality of Life-AD scale. Caregiver burden and depression were assessed by the Zarit Burden Interview and the Center for Epidemiologic Studies Depression Scale. RESULTS Intraclass correlation coefficients were low for apathy (0.38), daily functioning (0.38), and quality of life (0.30) and moderate for depression (0.49). These domains showed negative rating discrepancies, which indicates caregiver rating bias for all four domains. Regression analyses revealed that caregiver burden significantly contributed to explaining these discrepancies in the domains apathy, daily functioning, and quality of life. CONCLUSION Caregiver rating bias can be attributed to caregiver burden. When caregiver burden is present, data based on caregiver ratings should therefore be interpreted with caution.