title: Red cell distribution width and mortality in older adults: a meta-analysis.
abstract: BACKGROUND
  Red cell distribution width (RDW) is a quantitative measure of variability in the size of circulating erythrocytes with higher values reflecting greater heterogeneity in cell sizes. Recent studies have shown that higher RDW is associated with increased mortality risk in patients with clinically significant cardiovascular disease (CVD). Whether RDW is prognostic in more representative community-based populations is unclear.
  
  
  METHODS
  Seven relevant community-based studies of older adults with RDW measurement and mortality ascertainment were identified. Cox proportional hazards regression and meta-analysis on individual participant data were performed.
  
  
  RESULTS
  Median RDW values varied across studies from 13.2% to 14.6%. During 68,822 person-years of follow-up of 11,827 older adults with RDW measured, there was a graded increased risk of death associated with higher RDW values (p < .001). For every 1% increment in RDW, total mortality risk increased by 14% (adjusted hazard ratio [HR]: 1.14; 95% confidence interval [CI]: 1.11-1.17). In addition, RDW was strongly associated with deaths from CVD (adjusted HR: 1.15; 95% CI: 1.12-1.25), cancer (adjusted HR: 1.13; 95% CI: 1.07-1.20), and other causes (adjusted HR: 1.13; 95% CI: 1.07-1.18). Furthermore, the RDW-mortality association occurred in all major demographic, disease, and nutritional risk factor subgroups examined. Among the subset of 1,603 older adults without major age-associated diseases, RDW remained strongly associated with total mortality (adjusted HR: 1.32; 95% CI: 1.21-1.44).
  
  
  CONCLUSIONS
  RDW is a routinely reported test that is a powerful predictor of mortality in community-dwelling older adults with and without age-associated diseases. The biologic mechanisms underlying this association merit investigation.
authors.affiliation: Laboratory of Epidemiology, Demography, and Biometry, National Institute on Aging, Bethesda, Maryland 20892-9205, USA. kushang.patel@nih.gov
authors.forename: Kushang V
authors.initials: KV
authors.lastname: Patel
authors.forename: Richard D
authors.initials: RD
authors.lastname: Semba
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.forename: Linda P
authors.initials: LP
authors.lastname: Fried
authors.forename: Robert B
authors.initials: RB
authors.lastname: Wallace
authors.forename: Stefania
authors.initials: S
authors.lastname: Bandinelli
authors.forename: Caroline S
authors.initials: CS
authors.lastname: Phillips
authors.forename: Binbing
authors.initials: B
authors.lastname: Yu
authors.forename: Stephanie
authors.initials: S
authors.lastname: Connelly
authors.forename: Michael G
authors.initials: MG
authors.lastname: Shlipak
authors.forename: Paulo H M
authors.initials: PH
authors.lastname: Chaves
authors.forename: Lenore J
authors.initials: LJ
authors.lastname: Launer
authors.forename: William B
authors.initials: WB
authors.lastname: Ershler
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
authors.forename: Dan L
authors.initials: DL
authors.lastname: Longo
authors.forename: Jack M
authors.initials: JM
authors.lastname: Guralnik
mesh_terms: D000368:Aged; D000375:Aging; D002318:Cardiovascular Diseases / Q000097:blood / Q000401:mortality*; D004909:Erythrocyte Indices; D004912:Erythrocytes / Q000166:cytology*; D006801:Humans; D012307:Risk Factors; D015996:Survival Rate / Q000639:trends; D014481:United States / Q000453:epidemiology