Contemporary risk estimates of three HbA1c variables in relation to heart failure following diagnosis of type 2 diabetes

Background We evaluated the association between glycaemic control and the risk of heart failure (HF) in a contemporary cohort of persons followed after diagnosis of type 2 diabetes (T2D). Methods and results Persons with T2D diagnosed between 1998 and 2012 were retrieved from the Clinical Practice Research Data Link in the UK and followed from diagnosis until the event of HF, mortality, drop out from the database due to any other reason, or the end of the study on 1 July 2015. The association between each of three different haemoglobin A(1C) (HbA1c) metrics and HF was estimated using adjusted proportional hazard models. In the overall cohort (n= 94 332), the increased risk for HF per 1% (10 mmol/mol) increase in HbA(1c) was 1.15 (95% CI 1.13 to 1.18) for updated mean HbA(1c), and 1.06 (1.04 to 1.07) and 1.06 (1.04 to 1.08) for baseline HbA(1c) and updated latest HbA(1c), respectively. When categorised, the hazard risk (HR) for the updated mean HbA(1c) in relation to HF became higher than for baseline and updated latest HbA(1c) above HbA(1c) levels of 9%, but did not differ at lower HbA(1c) levels. The updated latest variable showed an increased risk for HbA(1c) < 6% (42 mmol/mol) of 1.16 (1.07 to 1.25), relative category 6-7%, while the HRs for updated mean and baseline HbA(1c) showed no such J-shaped pattern. Conclusions Hyperglycaemia is still a risk factor for HF in persons with T2D of similar magnitude as in earlier cohorts. Such a relationship exists for current glycaemic levels, at diagnosis and the overall level but the pattern differs for these variables.