title: The Relationship Between Caregiving and Mortality After Accounting for Time-Varying Caregiver Status and Addressing the Healthy Caregiver Hypothesis.
abstract: BACKGROUND
  Previous studies have shown inconsistent associations between caregiving and mortality. This may be due to analyzing caregiver status at baseline only, and that better health is probably related to taking on caregiving responsibilities and continuing in that role. The latter is termed The Healthy Caregiver Hypothesis, similar to the Healthy Worker Effect in occupational epidemiology. We applied common approaches from occupational epidemiology to evaluate the association between caregiving and mortality, including treating caregiving as time-varying and lagging exposure up to 5 years.
  
  
  METHODS
  Caregiving status among 1,068 women (baseline mean age = 81.0 years; 35% caregivers) participating in the Caregiver-Study of Osteoporotic Fractures study was assessed at five interviews conducted between 1999 and 2009. Mortality was determined through January 2012. Cox proportional hazards models were used to estimate adjusted hazard ratios and 95% confidence intervals adjusted for sociodemographics, perceived stress, and functional limitations.
  
  
  RESULTS
  A total of 483 participants died during follow-up (38.8% and 48.7% of baseline caregivers and noncaregivers, respectively). Using baseline caregiving status, the association with mortality was 0.77, 0.62-0.95. Models of time-varying caregiving status showed a more pronounced reduction in mortality in current caregivers (hazard ratios = 0.54, 0.38-0.75), which diminished with longer lag periods (3-year lag hazard ratio = 0.68, 0.52-0.88, 5-year lag hazard ratios = 0.76, 0.60-0.95).
  
  
  CONCLUSIONS
  Overall, caregivers had lower mortality rates than noncaregivers in all analyses. These associations were sensitive to the lagged period, indicating that the timing of leaving caregiving does influence this relationship and should be considered in future investigations.
authors: Epidemiology Department, Boston University School of Public Health, Massachusetts. lfredman@bu.edu.
authors: Lisa
authors: L
authors: Fredman
authors: Epidemiology Department, Boston University School of Public Health, Massachusetts.
authors: Jennifer G
authors: JG
authors: Lyons
authors: Epidemiology Department, University of Pittsburgh, Pennsylvania.
authors: Jane A
authors: JA
authors: Cauley
authors: Departments of Medicine and Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore.
authors: Marc
authors: M
authors: Hochberg
authors: Department of Environmental and Occupational Health, George Washington University, Milken Institute School of Public Health. Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts.
authors: Katie M
authors: KM
authors: Applebaum
mesh_terms: D000369:Aged, 80 and over; D017028:Caregivers / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D009026:Mortality; D016016:Proportional Hazards Models; D013997:Time Factors; D014481:United States / Q000453:epidemiology