Admission glucose as a prognostic marker for all-cause mortality and cardiovascular disease

Background Diabetes and prediabetes are known risk factors for cardiovascular disease and associated with increased mortality risk. Whether patients with a random elevated blood glucose level but no history of diabetes are at a higher mortality and cardiovascular risk is not entirely known. Methods A retrospective cohort study where patients (18-80 years) with no history of diabetes between 2006 and 2016 attending the emergency department (ED) in Sweden were included. Based on the first (index) blood glucose level patients were categorized into four groups: hypoglycemia (< 3.9 mmol/L), normal glucose tolerance (NGT) (3.9-7.8 mmol/L), dysglycemia (7.8-11.1 mmol/L), and hyperglycemia (> 11.1 mmol/L). Data was collected from four nationwide registers (National Patient Register, National Cause of Death Register, Prescribed Drug Register and Statistics Sweden). Cox regression was used to calculate adjusted hazard ratios (HR) with 95% confidence intervals (CI) for all-cause mortality and cardiovascular outcomes using NGT as reference. Results 618,694 patients were included during a mean follow-up time of 3.9 years. According to the index blood glucose level: 1871 (0.3%) had hypoglycemia, 525,636 (85%) had NGT, 77,442 (13%) had dysglycemia, and 13,745 (2%) patients had hyperglycemia, respectively. During follow-up 44,532 (7.2%) deaths occurred. After multiple adjustments, mortality risk was highest in patients with hypoglycemia HR 2.58 (2.26-2.96) followed by patients with hyperglycemia HR 1.69 (1.63-1.76) and dysglycemia HR 1.16 (1.13-1.19). Risk for cardiovascular events: i.e., myocardial infarction, stroke and heart failure, were highest among patients with hyperglycemia HR 2.28 (2.13-2.44), HR 1.62 (1.51-1.74) and HR 1.60 (1.46-1.75), respectively. Conclusion Patients with disturbed blood glucose level at ED admission have a higher mortality risk than patients with NGT. Patients with hyperglycemia have almost a two folded increased long-term mortality risk and more than a doubled risk for cardiovascular events compared to patients with NGT.