Aims: To assess the influence of glycaemic control on long-term mortality from ischaemic heart disease (IHD) in patients with newly diagnosed diabetes.
Methods and results: In a large population study in Norway, people > or =40 years with non-fasting glucose > or =8 mmol/L were invited to a fasting glucose test, and if the fasting value was <7 mmol/L, an oral glucose tolerance test was also performed. Among people who were diagnosed with diabetes, 205 patients were followed with annual measurements of HbA1c in order to monitor glycaemic control. Stratified Cox regression analysis was used to compare IHD mortality rates during 20 years of follow-up, with comparison of newly diagnosed diabetes patients and a matched group of 205 individuals without diabetes. Among patients, we also assessed the relation of HbA1c with IHD mortality. After adjustment for potentially confounding factors, IHD mortality in the total diabetes group was substantially higher (HR 1.8, 95% CI, 1.0-3.4) compared with the comparison group. However, the increased risk was particularly high in patients with HbA1c in the highest quartile (HR 4.2, 95% CI, 2.1-8.1). Analysing HbA1c as a continuous time-varying variable showed 30% (HR 1.3, CI 1.1-1.5) higher risk per increment of HbA1c among diabetes patients without known CVD at baseline.
Conclusion: Poor long-term glycaemic control is associated with a substantial increase in the risk of dying from IHD in patients with diabetes, whereas in patients with reasonably good control, risk of dying from IHD may not substantially differ from that of people without diabetes.