Changes in levels of haemoglobin A1c during the first 6 years after diagnosis of clinical type 2 diabetes

Objective: To assess the variability in levels of glycosylated haemoglobin (HbA(1c)) during the first six years after diagnosis of clinical type 2 diabetes in relation to possible predictors. Material and methods: Data were from a population-based sample from general practice of 581 newly diagnosed diabetic patients aged 40 or over. Estimation of HbA(1c) was centralized. The changes in levels of HbA(1c) were described by HbA(1c) at diagnosis and a regression line fitted to the HbA(1c) measurements after 1-year follow-up for each patient. The predictive effect of patient characteristics for changes in HbA(1c) was investigated in a multivariate mixed model. Results: During the first year after diabetes diagnosis, HbA(1c) dropped to near normal average level and then started rising almost linearly. A sharp rise in long-term glycaemic level was observed in approximately a quarter of the patients, especially the relatively young. Of 581 patients, 156 (26.9%) patients, however, experienced a fall in HbA(1c) after 1-year follow-up and another quarter showed constant or only slowly rising HbA(1c). The changes in levels of HbA(1c) were only predicted by diagnostic HbA(1c) and age. Conclusions: During the first 6 years after the diagnosis of clinical type 2 diabetes, changes in levels of HbA(1c) show considerable inter-individual variability with age as the only long-term predictor. The results indicate that it is important to monitor changes in HbA(1c) more closely and intensify treatment of those often relatively young patients who actually experience the beginning of an apparently relentless deterioration of their glycaemic control.