Associations of HbA1c and educational level with risk of cardiovascular events in 32871 drug-treated patients with Type2 diabetes: a cohort study in primary care

Aims To explore the association of HbA1c and educational level with risk of cardiovascular events and mortality in patients with Type2 diabetes. Methods A cohort of 32871 patients with Type2 diabetes aged 35years and older identified by extracting data from electronic patient records for all patients who had a diagnosis of Type2 diabetes and had glucose-lowering agents prescribed between 1999 and 2009 at 84 primary care centres in Sweden. Associations of mean HbA1c levels and educational level with risks of cardiovascular events and all-cause mortality were analysed. Results The associations of HbA1c with risk of all-cause and cardiovascular mortality were J-shaped, with the lowest risk observed for cardiovascular mortality at an HbA1c level of 51mmol/mol (6.8%) for subjects on oral agents and 56mmol/mol (7.3%) in insulin-treated patients. The lowest risk observed for all-cause mortality was at an HbA1c level of 51mmol/mol (6.8%) for subjects on oral agents and 56mmol/mol (7.3%) in insulin-treated patients. There was an increased risk for cardiovascular death [hazard ratio1.6 (1.22.1), P=0.0008] at the lowest HbA1c decile for subjects in the low education category. For subjects with higher education there was no evident J curve for cardiovascular death [hazard ratio1.2 (0.81.6), P=0.3873]. Conclusions Our results lend support to the recent American Diabetes Association/ European Association for the Study of Diabetes position statement that emphasizes the importance of additional factors, including the propensity for hypoglycaemia, which should influence HbA1c targets and treatment choices for individual patients. (Clinical Trials Registry No; NCT 01121315)