[Caregiver burden in dementia: evaluation with a Japanese version of the Zarit caregiver burden interview]

Dementia patients need assistance or supervision in their daily activities. This often places a major burden on their caregivers. The caregiver burden is reportedly a critical determinant for negative caregiving outcomes. However, in Japan, no study evaluating the burden experienced by caregivers for patients with established dementia diagnosis with a standardized instrument has been carried out. The Zarit Caregiver Burden Interview (ZBI) is a standardized, validated, reliable tool for assessment of the burden of caregivers for dementia patients, and has been used in many studies in North America. In this study, we arranged a Japanese version of the ZBI and applied it to caregivers who were caring dementia patients. After examining the reliability and validity of this version, we then studied a relationship between patients' impairments and caregivers' burden.

Subjects were 117 dementia patients. Diagnosis of dementia was made through extensive examinations including MRI and PET/SPECT of the brain and based on appropriate clinical diagnostic criteria of each disorder, which included Alzheimer's disease (n = 76), frontotemporal dementia (n = 10), vascular dementia (n = 11), progressive supranuclear palsy (n = 3), corticobasal degeneration (n = 5), dementia with Lewy bodies (n = 11), and normal pressure hydrocephalus (n = 1). The patients included 80 women and 37 men; the mean age was 72.3 +/- 7.7 (SD) years. Trained nurses interviewed a principal caregiver of each patient by using the ZBI. The caregivers included the patients' spouses (n = 62), offsprings (n = 17), offspring's spouses (n = 37), and sibling (n = 1). Cognitive, functional, and neuropsychiatric impairments and severity of dementia were assessed with standardized instruments of the Mini-Mental State Examination (MMSE), Hyogo Activities of Daily Living Scale (HADLS), Neuropsychiatric Inventory (NPI), and Clinical Dementia Rating (CDR), respectively.

The mean total ZBI score was 28.6 +/- 15.3 (SD), the Personal strain (PS) score was 17.4 +/- 8.9, and Role strain (RS) score was 6.5 +/- 5.7. All three scores had high Cronbach's alpha coefficients (Total: 0.88, PS: 0.78, RS: 0.80) and had high Pearson's correlation coefficients with a single global rating of burden (Total: 0.69, PS: 0.65, RS: 0.60). All ZBI scores were significantly correlated with MMSE, CDR, HADLS, and NPI scores. A stepwise regression analysis revealed only the HADLS score and NPI score as significant predictors of ZBI scores.

This Japanese version of the ZBI has a sufficient reliability and validity comparable to those reported for the original version. Our results suggested that the patients' functional and neuropsychiatric impairments were main patient's factors to increase the caregiver's burden.