title: Effect of aging on A1C levels in individuals without diabetes: evidence from the Framingham Offspring Study and the National Health and Nutrition Examination Survey 2001-2004.
abstract: OBJECTIVE
  Although glycemic levels are known to rise with normal aging, the nondiabetic A1C range is not age specific. We examined whether A1C was associated with age in nondiabetic subjects and in subjects with normal glucose tolerance (NGT) in two population-based cohorts.
  
  
  METHODS
  We performed cross-sectional analyses of A1C across age categories in 2,473 nondiabetic participants of the Framingham Offspring Study (FOS) and in 3,270 nondiabetic participants from the National Health and Nutrition Examination Survey (NHANES) 2001-2004. In FOS, we examined A1C by age in a subset with NGT, i.e., after excluding those with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). Multivariate analyses were performed, adjusting for sex, BMI, fasting glucose, and 2-h postload glucose values.
  
  
  RESULTS
  In the FOS and NHANES cohorts, A1C levels were positively associated with age in nondiabetic subjects. Linear regression revealed 0.014- and 0.010-unit increases in A1C per year in the nondiabetic FOS and NHANES populations, respectively. The 97.5th percentiles for A1C were 6.0% and 5.6% for nondiabetic individuals aged <40 years in FOS and NHANES, respectively, compared with 6.6% and 6.2% for individuals aged >or=70 years (P(trend) < 0.001). The association of A1C with age was similar when restricted to the subset of FOS subjects with NGT and after adjustments for sex, BMI, fasting glucose, and 2-h postload glucose values.
  
  
  CONCLUSIONS
  A1C levels are positively associated with age in nondiabetic populations even after exclusion of subjects with IFG and/or IGT. Further studies are needed to determine whether age-specific diagnostic and treatment criteria would be appropriate.
authors.affiliation: Department of Medicine, Diabetes Center, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA. lpani@partners.org
authors.forename: Lydie N
authors.initials: LN
authors.lastname: Pani
authors.forename: Leslie
authors.initials: L
authors.lastname: Korenda
authors.forename: James B
authors.initials: JB
authors.lastname: Meigs
authors.forename: Cynthia
authors.initials: C
authors.lastname: Driver
authors.forename: Shadi
authors.initials: S
authors.lastname: Chamany
authors.forename: Caroline S
authors.initials: CS
authors.lastname: Fox
authors.forename: Lisa
authors.initials: L
authors.lastname: Sullivan
authors.forename: Ralph B
authors.initials: RB
authors.lastname: D'Agostino
authors.forename: David M
authors.initials: DM
authors.lastname: Nathan
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000097:blood / Q000453:epidemiology*; D005260:Female; D018149:Glucose Intolerance / Q000097:blood / Q000453:epidemiology*; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D008913:Minority Groups; D044469:Racial Groups; D012016:Reference Values
chemical_list: D006442:Glycated Hemoglobin