Age‐related increase in haemoglobin A1c and fasting plasma glucose is accompanied by a decrease in β cell function without change in insulin sensitivity: evidence from a cross‐sectional study of hospital personnel

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Abstract
Aims To examine the influence of age on glucose homeostasis in a population of healthy, non‐diabetic hospital personnel.Methods One hundred and twenty female and 71 male non‐diabetic individuals (fasting plasma glucose < 7.0 mmol/l) were fasted overnight prior to blood sampling. Glycated haemoglobin (HbA1c), fasting plasma glucose (FPG) and fasting plasma insulin (FPI) were measured using a BioRad Diamat automated HPLC, a Hitachi 747 analyser and a sensitive in‐house radioimmunoassay, respectively. Mathematical modelling of the fasting glucose and insulin pairs (homeostasis model assessment (HOMA)) generated indices of pancreatic β cell function, HOMA‐B and tissue insulin sensitivity HOMA‐S.Results Spearman rank correlation analysis showed that in the whole group there was a significant negative correlation between age and HOMA‐B (rs= −0.218, P = 0.0022) and a significant positive correlation between age and both HbA1c (rs= 0.307, P = 0.0001) and FPG (rs= 0.26, P = 0.0003). There was no correlation between age and either FPI (rs= −0.08, P = 0.266) or HOMA‐S (rs= 0.024, P = 0.75). Analysis by gender showed the above associations to be present in the females (rs= −0.243, P = 0.0076; rs= 0.304, P = 0.0007; rs= 0.32, P = 0.0004 for age vs. HOMA‐B, HbA1c, and FPG, respectively). Again there was no correlation of age with FPI or insulin sensitivity. In the males there was a significant correlation of HbA1c with age (rs= 0.35, P = 0.002), but no significant correlation of age with any of the other parameters.Conclusions Glycaemic control deteriorates with age in healthy, non‐diabetic individuals. Age‐related rises in FPG and haemoglobin A1c result from a small but steady decline in pancreatic β cell function.Diabet. Med. 19, 254–258 (2002)