Abstract

Objective: Although glycemic levels are known to rise with normal aging, the non-diabetic A1C range is not age-specific. We examined whether A1C was associated with age in non-diabetic subjects and subjects with normal glucose tolerance (NGT) in two population-based cohorts.

Methods: We performed cross-sectional analyses of A1C across age categories in 2473 non-diabetic participants of the Framingham Offspring Study (FOS) and in 3270 non-diabetic participants from NHANES 2001-2004. In FOS, we examined A1C by age in a subset with NGT i.e. after excluding impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). Multivariate analyses were performed, adjusting for gender, BMI, fasting and 2-hr post-glucose (2hPG) values.

Results: In the FOS and NHANES cohorts, A1C levels were positively associated with age in non-diabetic subjects. Linear regression revealed a 0.014 and 0.010-unit increase in A1C per year in the non-diabetic FOS and NHANES populations, respectively. The 97.5^th percentiles for A1C were 6.0 and 5.6 for non-diabetic persons aged <40 in FOS and NHANES, respectively, compared with 6.6 and 6.2 for persons 70 years or older (p for trend <0.001). The association of A1C with age was similar when restricted to the subset of FOS subjects with NGT and after adjusting for gender, BMI, fasting and 2hPG values.

Conclusions: A1C levels are positively associated with age in non-diabetic populations even after excluding subjects with IFG and/or IGT. Further studies are needed to determine if age-specific diagnostic and treatment criteria would be appropriate.