Background: We aimed to examine the multidimensionality of the Zarit Burden Interview (ZBI) beyond the conventional dual-factor structure among caregivers of persons with cognitive impairment in a predominantly Chinese multiethnic Asian population, and ascertain how these dimensions vary across the spectrum of disease severity.
Methods: We studied 130 consecutive dyads of primary caregivers and patients attending a memory clinic over a six-month period. Caregiver burden was measured by the 22-item ZBI, and disease severity was staged via the Clinical Dementia Rating (CDR) scale. We performed principal component analysis (PCA) with varimax rotation to determine the factor structure of the ZBI. The magnitude of burden in each factor was expressed as the item to total ratio (ITR) and plotted against the stages of cognitive impairment. Descriptive and inferential statistics were applied to study the relationships between dimensions with disease and caregiver characteristics.
Results: We identified four factors: demands of care and social impact, control over the situation, psychological impact, and worry about caregiving performance. ITRs of the first three factors increased with severity of disease and were related to recipients' functional status and disease characteristics. ITR in the dimension of worry about performance was endorsed highest across the spectrum of disease severity, starting as early as the stage of mild cognitive impairment and peaking at CDR 1.
Conclusion: Multidimensionality of ZBI was confirmed in our local setting. Each dimension of burden was unique and expressed differentially across disease severity. The dimension of worry about performance merits further study.