[Impact of duration of caregiving on stress among primary caregivers of elderly]

This study examined (1) the direct effect of the duration of caregiving on caregiver psychological distress, and (2) two- or three-way interactions between duration, stressors (elderly's physical and cognitive impairments), and personal (caregiver's economic or work status) or social (informal or formal supports) resources. We interviewed 833 primary family caregivers of non-institutionalized frail elderly who had been selected through a screening process of all residents aged 65 and over (21,567 persons) in a suburban area of Tokyo. Caregiver psychological distress was evaluated by "Caregiving Burden Scale" as a caregiving-specific psychological measurement, and "Center for Epidemiologic Studies Depression Scale (CES-D)" as a general psychological measurement. The results were as follows. 1. For Caregiving Burden, duration showed a direct effect, as those who had been providing care for a longer duration of time reported higher burden. We found no interactions between duration, stressors, and resources on caregiving burden. 2. For CES-D, duration had interactions, but no direct effect. (1) Two-way interactions were observed between duration and caregiver's economic or work status, as caregivers with a low economic status or who were unemployed showed a stronger negative impact from duration of caregiving. (2) Three-way interactions were observed between duration, the elderly's ADL impairment, and informal support. Informal support, such as a secondary caregiver, buffered the negative impact of the elderly's ADL impairment in cases with a shorter duration of caregiving, but not for those with longer duration. (3) Three-way interactions were observed between duration, the elderly's cognitive impairment, and formal emotional support. Formal emotional support buffered the negative impact of the elderly's cognitive impairment for those with a longer duration of caregiving, but not for those with a shorter duration. These findings suggest that stress-buffering resources differ according to duration of caregiving.