Changes over Time in Hemoglobin A1C (HbA(1C)) Levels Predict Long-Term Survival Following Acute Myocardial Infarction among Patients with Diabetes Mellitus

Frequent fluctuations of hemoglobin A1c (HbA(1C)) values predict patient outcomes. However, data regarding prognoses depending on the long-term changes in HbA(1C) among patients after acute myocardial infarction (AMI) are scarce. We evaluated the prognostic significance of HbA(1C) levels and changes among diabetic patients (n = 4066) after non-fatal AMI. All the results of HbA(1C) tests up to the 10-year follow-up were obtained. The changes (∆) of HbA(1C) were calculated in each patient. The time intervals of ∆HbA(1C) values were classified as rapid (<one year) and slow (≥one year) changes. The outcome was all-cause mortality. The highest mortality rates of 53.8% and 35.5% were found in the HbA(1C) < 5.5–7% and ∆HbA(1C) = −2.5–(−2%) categories. A U-shaped association was observed between HbA(1C) and mortality: adjOR = 1.887 and adjOR = 1.302 for HbA(1C) < 5.5% and ≥8.0%, respectively, as compared with 5.5–6.5% (p < 0.001). Additionally, ∆HbA(1C) was associated with the outcome (U-shaped): adjOR = 2.376 and adjOR = 1.340 for the groups of <−2.5% and ≥2.5% ∆HbA(1C), respectively, as compared to minimal ∆HbA(1C) (±0.5%) (p < 0.001). A rapid increase in HbA(1C) (but not decrease) was associated with a greater risk of mortality. HbA(1C) values and their changes are significant prognostic markers for long-term mortality among AMI-DM patients. ∆HbA(1C) and its timing, in addition to absolute HbA(1C) values, should be monitored.