Researchers found that patients with type 2 diabetes and chronic heart failure (CHF) have a lower risk of mortality when administered drugs that maintain their glycemic levels far from either extreme, whether very low or very high. The study, titled “Mean HbA1c and mortality in diabetic individuals with heart failure: a population cohort study,” was published in the European Journal of Heart Failure.
CHF patients frequently also have type 2 diabetes, with population-based studies pointing to estimates of between 11% and 28%, and rising to 25% to 30% in patients hospitalized for CHF. This association can have a serious impact on CHF patient outcomes, since type 2 diabetes is suggested to be an independent risk factor for increasing CHF morbidity and mortality.
A debate still exists on whether glycemic control is important in type 2 diabetes patients with CHF, with previous reports suggesting that glycemic control significantly reduces both the risk for micro- (diabetic nephropathy, neuropathy, and retinopathy) and macrovascular (coronary artery disease, peripheral arterial disease, and stroke) disease.
The research team performed multiple measurements over time of serial glycosylated haemoglobin (HbA1c) levels, an established predictor of diabetic complications, accounting for the time span that the patient was at that level, in a large cohort of 1,447 patients who developed incident CHF after being diagnosed with type 2 diabetes. Researchers determined the time-weighted mean HbA1c and patients’ outcomes in a follow-up period of 2.8 years, during which 826 patient deaths (57.1%) were registered.
Researchers observed a U-shaped relationship between mortality and glycemic control in this patient cohort, with a higher mortality risk in patients in the lower HbA1c categories (HbA1c ≤6% and HbA1c 6.1–7%) but also a poor outcome in CHF patients with the highest HbA1c. Notably, this U-shaped relationship was observed only in drug-treated type 2 diabetes patients (but not in diet-treated patients).
In conclusion, the findings suggest that in patients with type 2 diabetes and CHF, the lowest mortality risk occurs in those with modest glycemic control (HbA1c, 7.1–8.0%). The team proposes that the use of low hypoglycaemia risk medications, such as metformin, is a safe and efficacious strategy (at least in this cohort of patients). The authors highlighted that the results support the need to redefine the optimal HbA1c level, as well as the treatments more advantageous for high-risk patients with co-existing type 2 diabetes and CHF.