Inpatient Hypoglycaemia—The Next Prognostic Factor: A Retrospective Case–Control Study of Hospital Inpatients with and Without Diabetes Mellitus

Background: Hospital inpatient hypoglycaemia is a common complication associated with poor patient outcomes. With the rising prevalence of diabetes mellitus (DM) and approximately 20% of hospital beds occupied by patients with DM, inpatient hypoglycaemia is an important safety concern. We aimed to determine the incidence of and risk factors for inpatient hypoglycaemia and their association with mortality and hospital length of stay (LOS). Methods: A retrospective single-centre case–control study was conducted at Nepean Hospital, New South Wales, Australia, over 12 months (July 2018–June 2019). The cases were inpatients who experienced hypoglycaemia, defined as capillary blood glucose <4 mmol/L. Patients with hypoglycaemia were stratified into those with and without DM. The controls were randomly selected inpatients with DM admitted during the same period who did not experience hypoglycaemia. Results: A total of 251 episodes of hypoglycaemia occurred in 234 patients; 202 events (80%) occurred in 187 patients with DM and 49 (20%) in 47 patients without DM. In the patients with DM, the factors associated with hypoglycaemia included basal–bolus insulin (aOR 26.6; 95% CI 7.9–106.6), premixed insulin (aOR 5.9; 95% CI 1.6–25.9), sulfonylureas (aOR 3.2; 95% CI 1.1–9.6), and malnutrition (aOR 4.2; 95% CI 1.2–18.0). Compared with the controls, patients with DM and hypoglycaemia had higher inpatient mortality (10.2% vs. 3.0%), 12-month mortality (20.9% vs. 5.5%), and a longer median LOS (12 vs. 4 days). The twelve-month mortality was 36.2% in patients without DM who experienced hypoglycaemia. Conclusions: Inpatient hypoglycaemia is associated with high mortality and increased LOS, highlighting the need for greater awareness and effective prevention strategies.