title: White blood cell counts, insulin-like growth factor-1 levels, and frailty in community-dwelling older women.
abstract: BACKGROUND
  Elevated white blood cell (WBC) counts and decreased insulin-like growth factor-1 (IGF-1) levels are individually associated with frailty in older adults. WBC subpopulations are known to produce IGF-1 and express IGF-1 receptors in vitro. However, in vivo relationships between WBC and IGF-1 and their joint contribution to frailty have not been investigated.
  
  
  METHODS
  Baseline data from 696 community-dwelling older women in the Women's Health and Aging Study I were included in this cross-sectional analysis. Multivariate linear regression analysis was performed to assess the relationship between WBC counts and IGF-1 levels. Odds ratios (ORs) for frailty were evaluated across tertiles of WBC counts and IGF-1 levels, adjusting for age, race, education, body mass index, and smoking.
  
  
  RESULTS
  WBC counts correlated with IGF-1 levels (Spearman coefficient: .10, p < .01). Compared with participants in the low WBC and high IGF-1 tertiles (reference group), those in the low WBC and low IGF-1 tertiles had OR of 2.33 for frailty (95% confidence interval [CI]: 1.04-3.65, p < .05), those in the high WBC and high IGF-1 tertiles had OR of 3.86 (95% CI: 1.13-4.07, p < .01), and those in the high WBC and low IGF-1 tertiles had OR of 3.61 (95% CI: 1.64-4.97, p < .01), adjusting for covariates.
  
  
  CONCLUSIONS
  These findings demonstrate in vivo correlation between WBC and IGF-1. They suggest U-shaped joint associations of WBC and IGF-1 with frailty, with the strongest association at adverse levels of both. They also provide a basis for further investigation into the complex immune-endocrine dysregulations in frailty.
authors.affiliation: Division of Geriatric Medicine and Gerontology, 5505 Hopkins Bayview Circle, Johns Hopkins School of Medicine, Baltimore, MD 21224, USA. sleng1@jhmi.edu
authors.forename: Sean X
authors.initials: SX
authors.lastname: Leng
authors.forename: Will
authors.initials: W
authors.lastname: Hung
authors.forename: Anne R
authors.initials: AR
authors.lastname: Cappola
authors.forename: Qilu
authors.initials: Q
authors.lastname: Yu
authors.forename: Qian-Li
authors.initials: QL
authors.lastname: Xue
authors.forename: Linda P
authors.initials: LP
authors.lastname: Fried
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis*; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D016330:Frail Elderly; D015577:Geriatric Assessment; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007958:Leukocyte Count; D016017:Odds Ratio; D011336:Probability; D012111:Residence Characteristics; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D016387:Women's Health
chemical_list: D015415:Biomarkers; D007334:Insulin-Like Growth Factor I