Aging is associated with increased HbA1clevels, independently of glucose levels and insulin resistance, and also with decreased HbA1cdiagnostic specificity

AIM To determine whether using HbA1c for screening and management could be confounded by age differences, whether age effects can be explained by unrecognized diabetes and prediabetes, insulin resistance or postprandial hyperglycaemia, and whether the effects of aging have an impact on diagnostic accuracy. METHODS We conducted a cross-sectional analysis in adults without known diabetes in the Screening for Impaired Glucose Tolerance (SIGT) study 2005-2008 (n=1573) and the National Health and Nutrition Examination Survey (NHANES) 2005-2006 (n=1184). RESULTS Both glucose intolerance and HbA(1c) levels increased with age. In univariate analyses including all subjects, HbA(1c) levels increased by 0.93 mmol/mol (0.085%) per 10 years of age in the SIGT study and by 1.03 mmol/mol (0.094%) per 10 years in the NHANES; in both datasets, the HbA(1c) increase was 0.87 mmol/mol (0.08%) per 10 years in subjects without diabetes, and 0.76 mmol/mol (0.07%) per 10 years in subjects with normal glucose tolerance, all P