Validation of 'personal strain' and 'role strain': Subscales of the short version of the Japanese version of the Zarit Burden Interview (J-ZBI_8)

The eight-item short version of the Japanese version of the Zarit Burden Interview (J-ZBI_8) has been confirmed for reliability and validity, and its two subscales (personal strain and role strain) are based on the factor structure of the ZBI. It has been demonstrated that these subscales have good reliability. The aim of the present study was to confirm their construct validity. A total of 51 impaired elderly who had been receiving regular nurses' visits in Kyoto Prefecture, Japan and their family primary caregivers, participated in the present study. Each caregiver was asked to complete a questionnaire which included the J-ZBI_8, the hours spent in caregiving, and the physical and cognitive disability of the impaired elderly. A principal component analysis identified the following two principal components of these variables: 'Activities of Daily Living deficits' and 'behavioral disturbances'. Consequently, Barthel Index (BI) and Troublesome Behavior Scale (TBS) were selected as the representative variable, respectively, for each component. We subsequently calculated the Spearman's rank correlations among the subscales of J-ZBI_8, BI and TBS. Personal strain was found to be correlated with TBS (rho = 0.48, P < 0.01), while role strain was correlated with the BI (rho = -0.29, P = 0.04). The correlation between personal strain and BI was not significant, nor was the correlation between role strain and TBS. These findings indicate that the personal strain and role strain measured by J-ZBI_8 correspond to the personal strain and role strain of the ZBI originally described by Whitlatch et al. Therefore, the construct validity of the J-ZBI_8 subscales is confirmed.