The Caregiver Activity Survey (CAS): longitudinal validation of an instrument that measures time spent caregiving for individuals with Alzheimer's disease.

Family members incur substantial financial costs during the course of caring for an individual with Alzheimer's disease. Much of this cost is associated with time spent in caregiving tasks, including supervision and communication with the patient, and assisting with activities of daily living. We have previously reported on the cross sectional reliability and validity of a scale that measures time spent caregiving, the Caregiver Activity Survey (CAS). This study extends our results to a longitudinal study of the validity of the instrument. Forty-four outpatients with Alzheimer's disease who lived with a primary caregiver were followed over a period of 1 year 6 months. At six month intervals, the patients were administered the Mini Mental State Exam (MMSE), Alzheimer's Disease Assessment Scale (ADAS), and the Physical Self Maintenance Scale (PSMS). Caregivers completed the CAS. Over time, the CAS correlated significantly with the MMSE (r=-0.58, p=0.000), ADAS cognitive subscale (r=0.56, p=0. 000) and PSMS (r=0.49, p=0.000). As patients declined, caregivers spent less time communicating with and more time supervising the patient. Excluding the communication item, time spent caregiving increased significantly over time. This prospective study longitudinally validates the CAS with Alzheimer's patients.