Incidence of hypoglycaemia associated with transient loss of consciousness. A retrospective cohort study

Summary Objective To define the incidence of hypoglycaemia associated with transient loss of consciousness (TLoC). Design Retrospective cohort study using a nested case–control analysis. Setting Presentations to the emergency departments (EDs) of four general metropolitan hospitals in Azienda Sanitaria 10, Florence, Italy during 2012. Participants The cohort consisted of 133,285 patients extracted from the database of ED presentations. All patients with TLoC were identified by nurse triage, and their levels of glycaemia were recorded. Clinical investigations were undertaken using patients’ charts and witness statements. Patients were matched with controls according to year of birth, year of cohort entry and gender. Results Of the 133,285 patients, 3964 (2.9%) presented with TLoC, and 39 (1%) of the patients with TLoC had transient hypoglycaemia. Mean glycaemia in these 39 patients was 52 mg/dl (a level of 112 mg/dl was in controls). Symptoms associated with TLoC during hypoglycaemia differed from those characteristic of syncope. TLoC during hypoglycaemia mainly occurred in elderly patients with diabetes, who had relatively long disease duration, were receiving treatment, often also had renal failure and were experiencing symptoms as a result of lack of food intake. Together, these factors make it easier to diagnose hypoglycaemia associated with TLoC, and our results may prompt modification in medical practice. Conclusion Correct diagnosis of hypoglycaemia associated with TLoC has economic benefits if a protracted and costly series of clinical investigations can be avoided. A diagnosis of hypoglycaemia might also facilitate the resolution of patients’ symptoms through lifestyle changes and adjustment of therapy.