Prediabetes in Acute Coronary Syndrome: An Overlooked Predictor of Adverse Outcomes

Introduction Hemoglobin A1c (HbA1c) is a well-established marker for long-term glycemic control and a diagnostic tool for diabetes mellitus (DM). The relationship between HbA1c levels and prognosis among acute coronary syndrome (ACS) patients is not well described. The aim of the current study was to evaluate the prognostic value of admission HbA1c levels in patients with ACS admitted to contemporary intensive cardiovascular care unit (ICCU). Methods A prospective single center study included all patients admitted to the ICCU between July 2019 and December 2024 with ACS. Patients were categorized by HbA1c levels into three groups: non-DM (< 5.7%), pre-DM (5.7–6.4%), and DM (≥ 6.5%). Demographics, clinical characteristics, in-hospital complications, and long-term (up to 60 months) mortality were analyzed. Results A total of 2,772 patients were admitted with a diagnosis of ACS and had HbA1c levels recorded at admission. Among them, 41.4% were non-diabetic, 29.1% had pre-diabetes, and 29.5% had diabetes. In-hospital mortality showed a gradual increase across these groups: 2.0% in non-diabetics, 1.6% in pre-diabetics, and 2.9% in diabetics (p = 0.294). Long-term mortality rose significantly with higher HbA1c categories, reaching 11.4%, 14.7%, and 18.1%, respectively (p < 0.001). Multivariate analysis confirmed DM as an independent predictor of mortality (HR 1.635, 95% CI: 1.280–2.08, p < 0.001). Conclusions Over half of patients admitted with an ACS have evidence of dysglycemia. Both pre-DM and DM groups were associated with increased long-term mortality in ACS patients. The findings highlight the need for greater recognition and management, especially of pre-DM ACS patients in acute cardiovascular care.