Relative importance of patient disease indicators on informal care and caregiver burden in Alzheimer's disease.

BACKGROUND: Cognition, abilities in activities of daily living (ADL), and behavioral disturbances in patients with Alzheimer's disease (AD) all influence the number of hours informal caregivers spend caring for their patients, and the burden caregivers experience. However, the direct effect and relative importance of each disease severity measure remains unclear. METHODS: Cross-sectional interviews were conducted with 1,222 AD patients and primary caregivers in Spain, Sweden, the U.K. and the U.S.A. Assessments included informal care hours, caregiver burden (Zarit Burden Inventory; ZBI), cognition (Mini-mental State Examination; MMSE), ADL-abilities (Disability Assessment for Dementia scale; DAD), and behavioral symptoms (Neuropsychiatric Inventory Questionnaire; NPI-severity). RESULTS: Multivariate analyses of 866 community-dwelling patients revealed that ADL-ability was the strongest predictor of informal care hours (36% decrease in informal care hours per standard deviation (SD) increase in DAD scores). Severity of behavioral disturbances was the strongest predictor of caregiver burden (0.35 SD increase in ZBI score per SD increase in NPI-Q severity score). In addition, the effect of ADL-abilities was, although attenuated, not negligible (0.28 SD increase in ZBI score per SD increase in DAD score). Decreasing cognition (MMSE) was associated with more informal care hours and increased caregiver burden in univariate, but not in adjusted analyses. CONCLUSIONS: For patients residing in community dwellings, the direct influence of patients' cognition on caregiver burden is limited and rather mediated by other disease indicators. Instead, the patients' ADL-abilities are the main predictor of informal care hours, and both ADL-abilities and behavioral disturbances are important predictors of perceived caregiver burden, where the latter has the strongest effect. These results were consistent across Sweden, U.K. and the U.S.A.

Predictors of costs of care in Alzheimer's disease: a multinational sample of 1222 patients.

BACKGROUND: The costs of care for patients with Alzheimer's disease are correlated with key measures of disease severity. This relationship is important in the economic evaluation of new treatments and is used to translate treatment efficacy into effects on costs through economic modeling. We aimed to identify what measures of disease severity are the most important predictors of societal costs of care and whether their relationship differs across countries. METHODS: Interviews were conducted with 1222 patient and caregiver pairs residing in the community or in residential care settings in Spain, Sweden, United Kingdom, and the United States. Assessments included costs of care (Resource Utilization in Dementia) and key disease severity measures: cognitive function (Mini-Mental State Examination), ability to perform Activities of Daily Living (ADL-ability, Disability Assessment for Dementia [DAD]), and behavioral symptoms (Neuropsychiatry Inventory (NPI)-severity). RESULTS: ADL-ability was the most important predictor of societal costs of care of community-dwelling patients in all countries. A one-point decrease in DAD resulted in a 1.4% increase in costs of care in Spain, United Kingdom, and the United States on average, and a 2% increase in Sweden. This translated into a 45% increase from a standard deviation decrease in DAD on average. NPI-severity and Mini-Mental State Examination were also significant predictors but with lesser effect. Although mean costs of care differed across countries, the important predictors were the same. CONCLUSION: ADL-ability is the most important predictor of societal costs of care in community dwellings irrespective of country and should therefore be central in the economic evaluation of Alzheimer's disease therapies.