Caregiving frequency and physical function: the Women's Health Initiative.

Background: Informal caregiving is common for older women and can negatively affect health, but its impact on physical function remains unclear. Using inverse probability weighting methods, we quantified the association of caregiving with physical function over 6 years.

Methods: Study participants were 5,649 women aged 65 years and older at baseline of the Woman's Health Initiative Clinical Trial (multicenter recruitment, 1993-1998) with complete caregiving data and function at baseline and at least one follow-up. Caregiving was self-reported (low-frequency if ≤2 times per week and high-frequency if ≥3 times per week). Performance-based measures of physical function including timed walk (meters/second), grip strength (kilograms), and chair stands (number) were measured at baseline and years 1, 3, and 6. Associations and 95% confidence intervals of baseline caregiving with physical function were estimated by generalized estimating equations with inverse probability weighting by propensity and attrition scores, calculated by logistic regression of baseline health and demographic characteristics.

Results: Over follow-up, low-frequency caregivers had higher grip strength when compared with noncaregivers (mean difference = 0.63kg, confidence interval: 0.24, 1.01). There were no observed differences between high-frequency caregivers and noncaregivers on grip strength or for either caregiver group when compared with noncaregivers on walk speed or chair stands. Rates of change in physical function measures did not differ by caregiving status.

Conclusions: Caregiving was not associated with poorer physical function in this sample of older women. Low-frequency caregiving was associated with better grip strength at baseline which persisted through follow-up. This study supports the concept that informal caregiving may not have universally negative health consequences.