Background: The impact of admission glycated hemoglobin (HbA1c) on hospital outcome is controversial.
Objectives: To evaluate the association between admission glucose and HbA1c levels and mortality 1 year after hospitalization in the internal medicine ward.
Methods: HbA1c level of consecutive patients was measured during the first 24 hours of admission to the internal medicine ward and divided at the cutoff point of 6.5%. Three groups of patients were prospectively identified: patients with preexisting diabetes mellitus (DM), patients with glucose > 140 mg/dl (hyperglycemia) on admission and no known diabetes (H), and patients without diabetes or hyperglycemia (NDM). The primary end-point was 1 year all-cause mortality.
Results: A total of 1024 patients were enrolled, 592 (57.8%) belonged to the DM group, 119 (11.6/6) to the H group and 313 (30.6%) to the NDM group. At 1 year, death occurred in 70 (11.9%) in the DM group, 12 (10.0%) in the H group and 15 (4.8%) in the NDM group (P = 0.002). Elevated admission glucose levels did not influence outcome in any of the groups. HbA1c levels were similar for survivors and non-survivors (P = 0.60). Within-group multivariate analysis adjusted for comorbidities and age showed that in the H group HbA1C levels of 6.5% or above were associated with increased mortality risk [hazard ratio (HR) 8.25, 95% confidence interval (CI) 1.93-35.21]. In the DM group, HbA1c levels below 6.5% were associated with increased mortality risk (HR = 2.05, 95% CI 1.25-3.36).
Conclusions: Glucose levels upon admission did not affect mortality. However, HbA1c levels below 6.5% had opposite effects on 1 year mortality in diabetes patients and patients with hyperglycemia.