Caregiving Frequency and Physical Function: The Women’s Health Initiative

Caregiving has been associated with an increased risk for poor mental health and quality of life, particularly when caregiving circumstances are stressful (1,2). Stressful conditions are often related to more frequent provision of care and to greater disability in the care recipient (2,3). The psychological and physical stresses of caregiving may lead to declines in physical health over time, and therefore, greater frequency of care provision may indicate greater risk for poor outcomes. However, studies have also reported a beneficial effect of caregiving on physical health, cognition, and mortality (4–8). Caregiving may promote the maintenance of physical function through regular physical activity as part of daily care activities (5,9) and may provide positive psychological benefits (10–12). Studies of informal caregiving have traditionally been grounded in stress frameworks that predict poor health outcomes from provision of caregiving and greater caregiving burden (13). In contrast, the Healthy Caregiver Hypothesis posits that individuals who become and remain caregivers may be healthier and more physically robust, resulting in better health outcomes for caregivers when compared with noncaregivers (4,9); this may be particularly true for those caregivers providing more frequent care. Longitudinal research is necessary to address this possibility (14). Declines in physical function in older adults, particularly women, have been shown to negatively affect health and increase risk of disability (15,16). Assessments of the relation of caregiving with changes in physical function over time are sparse and findings are inconsistent (5,9,17,18). Low-frequency, but not high-frequency caregiving, was associated with poorer overall physical functioning over 2 years in a biracial cohort of older women (9). Caregiving was also associated with incident mobility limitations in older white, but not black, adults (5). In contrast, caregiving was not associated with walking speed over 1 year follow-up (17) or with incident frailty in a biracial cohort of adults aged 65 years or older (18). These inconsistencies may be due to different outcome measures, sample selection, or to the observational nature of these studies. Studies using population-based samples have generally found a smaller effect of caregiving on health outcomes relative to convenience samples (2). Further, as caregiving status is not randomized, differences in baseline characteristics of the caregivers and noncaregivers may lead to biased effect estimates (19). In addition, differential attrition through death or drop-out by caregiver status may affect estimates (20). We assessed changes in performance-based measures of physical functioning among noncaregivers and low- or high-frequency caregivers over 6 years using data from the Women’s Health Initiative clinical trials. We used weighting procedures to mitigate some of the inherent biases in observational studies of exposures such as caregiving that cannot be evaluated in intervention studies, including differences in baseline characteristics and in loss to follow-up (19,20). We hypothesized a decline in physical function among caregivers relative to noncaregivers after accounting for selection and attrition by weighting.