title: Effect of Alzheimer caregiving stress and age on frailty markers interleukin-6, C-reactive protein, and D-dimer.
abstract: BACKGROUND
  Elevated plasma levels of interleukin (IL)-6, C-reactive protein (CRP), and D-dimer belong to the biological alterations of the "frailty syndrome," defining increased vulnerability for diseases and mortality with aging. We hypothesized that, compatible with premature frailty, chronic stress and age are related in predicting inflammation and coagulation activity in Alzheimer caregivers.
  
  
  METHODS
  Plasma IL-6, CRP, and D-dimer levels were measured in 170 individuals (mean age 73 +/- 9 years; 116 caregivers, 54 noncaregiving controls). Demographic factors, diseases, drugs, and lifestyle variables potentially affecting inflammation and coagulation were obtained by history and adjusted for as covariates in statistical analyses.
  
  
  RESULTS
  Caregivers had higher mean levels of IL-6 (1.38 +/- 1.42 vs 1.00 +/- 0.92 pg/mL, p =.032) and of D-dimer (723 +/- 530 vs 471 +/- 211 ng/mL, p <.001) than controls had. CRP levels were similar between groups (p =.44). The relationship between caregiver status and D-dimer was independent of covariates (p =.037) but affected by role overload. Age accounted for much of the relationship with IL-6. After controlling for covariates, the interaction between caregiver status and age was significant for D-dimer (beta =.20, p =.029) and of borderline significance for IL-6 (beta =.17, p =.090). Post hoc regression analyses indicated that, among caregivers, age was significantly correlated with both D-dimer (beta =.50, p <.001) and IL-6 (beta =.38, p =.001). Among controls, however, no significant relationship was observed between age and either D-dimer or IL-6.
  
  
  CONCLUSIONS
  The interaction between caregiving status and age for D-dimer and IL-6 suggests the possibility that older caregivers could be at risk of a more rapid transition to the frailty syndrome and clinical manifestations of cardiovascular diseases.
authors.affiliation: Department of General Internal Medicine, Division of Psychosomatic Medicine, University Hospital, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: von Känel
authors.forename: Joel E
authors.initials: JE
authors.lastname: Dimsdale
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Mills
authors.forename: Sonia
authors.initials: S
authors.lastname: Ancoli-Israel
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Patterson
authors.forename: Brent T
authors.initials: BT
authors.lastname: Mausbach
authors.forename: Igor
authors.initials: I
authors.lastname: Grant
mesh_terms: D000367:Age Factors; D000368:Aged; D000544:Alzheimer Disease / Q000523:psychology*; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D017028:Caregivers / Q000523:psychology*; D016022:Case-Control Studies; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D015999:Multivariate Analysis; D012380:Role; D013315:Stress, Psychological / Q000097:blood
chemical_list: D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products; D015850:Interleukin-6; C036309:fibrin fragment D; D002097:C-Reactive Protein