title: Caregiving frequency and physical function: the Women's Health Initiative.
abstract: 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.
authors: Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pennsylvania. alr143@pitt.edu.
authors: Andrea L
authors: AL
authors: Rosso
authors: Department of Epidemiology and Biostatistics, School of Public Health, Drexel University, Philadelphia, Pennsylvania.
authors: Brian K
authors: BK
authors: Lee
authors: Stanford Prevention Research Center, Stanford University, School of Medicine, Palo Alto, California.
authors: Marcia L
authors: ML
authors: Stefanick
authors: Kaiser Permanente Division of Research, Oakland, California.
authors: Candyce H
authors: CH
authors: Kroenke
authors: Department of Social Sciences and Health Policy, Wake Forest School of Medicine, Winston Salem, North Carolina.
authors: Laura H
authors: LH
authors: Coker
authors: School of Nursing, University of Washington, Seattle.
authors: Nancy F
authors: NF
authors: Woods
authors: Department of Epidemiology and Biostatistics, School of Public Health, Drexel University, Philadelphia, Pennsylvania.
authors: Yvonne L
authors: YL
authors: Michael
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D017028:Caregivers / Q000706:statistics & numerical data*; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D005684:Gait; D015577:Geriatric Assessment; D018737:Hand Strength; D006801:Humans; D016015:Logistic Models; D057566:Self Report; D016387:Women's Health
keywords: Aging; Caregiving; Physical function; Women’s health.