title: The prevalence of limited health literacy.
abstract: OBJECTIVE
  To systematically review U.S. studies examining the prevalence of limited health literacy and to synthesize these findings by evaluating demographic associations in pooled analyses.
  
  
  METHODS
  We searched the literature for the period 1963 through January 2004 and identified 2,132 references related to a set of specified search terms. Of the 134 articles and published abstracts retrieved, 85 met inclusion criteria, which were 1) conducted in the United States with > or =25 adults, 2) addressed a hypothesis related to health care, 3) identified a measurement instrument, and 4) presented primary data. The authors extracted data to compare studies by population, methods, and results.
  
  
  RESULTS
  The 85 studies reviewed include data on 31,129 subjects, and report a prevalence of low health literacy between 0% and 68%. Pooled analyses of these data reveal that the weighted prevalence of low health literacy was 26% (95% confidence interval [CI], 22% to 29%) and of marginal health literacy was 20% (95% CI, 16% to 23%). Most studies used either the Rapid Estimate of Adult Literacy in Medicine (REALM) or versions of the Test of Functional Health Literacy in Adults (TOFHLA). The prevalence of low health literacy was not associated with gender (P=.38) or measurement instrument (P=.23) but was associated with level of education (P=.02), ethnicity (P=.0003), and age (P=.004).
  
  
  CONCLUSIONS
  A pooled analysis of published reports on health literacy cannot provide a nationally representative prevalence estimate. This systematic review exhibits that limited health literacy, as depicted in the medical literature, is prevalent and is consistently associated with education, ethnicity, and age. It is essential to simplify health services and improve health education. Such changes have the potential to improve the health of Americans and address the health disparities that exist today.
authors.affiliation: Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA. mpo@bu.edu
authors.forename: Michael K
authors.initials: MK
authors.lastname: Paasche-Orlow
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Parker
authors.forename: Julie A
authors.initials: JA
authors.lastname: Gazmararian
authors.forename: Lynn T
authors.initials: LT
authors.lastname: Nielsen-Bohlman
authors.forename: Rima R
authors.initials: RR
authors.lastname: Rudd
mesh_terms: D004522:Educational Status; D005260:Female; D006266:Health Education; D006801:Humans; D008297:Male; D014481:United States