The effects of ageing on glycation and the interpretation of glycaemic control in Type 2 diabetes.

To investigate the discrepancy in the assessment of glycaemic control using glycated haemoglobin (HbA1C) and glycated proteins (fructosamine), the effect of age on these variables was measured in non-diabetic individuals. In 232 non-diabetics, there was a linear relationship between HbA1C and age (r = 0.49, p < 0.0001). Mean HbA1C rose from 3.82% to 4.44% between the ages of 20 and 70. Consequently, when Type 2 diabetic patient samples (n = 128, median age 63 years) were classified according to European guidelines into good or poor glycaemic control using both an age-matched (n = 101) and a younger (n = 108, median age 37 years) non-diabetic reference population, fewer patients were in good control (14% vs. 25%) and more in poor control (73% vs. 53%) when the younger reference population was used (both p < 0.05). In a subgroup of 126 non-diabetic subjects, HbA1C rose with age (r = 0.48), but serum fructosamine and fasting glucose did not (r = 0.07, r = 0.009, respectively, p = NS). Age-associated differences in non-diabetic HbA1C values may affect the assessment of glycaemic control in diabetic patients. It may also partly explain discrepancies found when comparing fructosamine with HbA1C as a measure of glucose control. Age-related HbA1C reference intervals may therefore be required for the treatment of patients and the accurate auditing of clinic performance.