title: Frequency of biochemical hypoglycaemia in adults with Type 1 diabetes with and without impaired awareness of hypoglycaemia: no identifiable differences using continuous glucose monitoring.
abstract: OBJECTIVE
  Impaired awareness of hypoglycaemia (IAH) is a major risk factor for severe hypoglycaemia in Type 1 diabetes. Although biochemical hypoglycaemia is asserted to be more frequent in IAH, this has not been estimated accurately. The aim of this study was to use Continuous Glucose Monitoring (CGM) to quantify hypoglycaemia in IAH and evaluate its use in identifying impaired awareness of hypoglycaemia.
  
  
  METHODS
  Ninety-five patients with Type 1 diabetes were classified as having normal (n = 74) or impaired awareness (n = 21) using an established method of assessing hypoglycaemia awareness. Hypoglycaemia exposure was assessed prospectively over 9-12 months using weekly 4-point capillary home blood glucose monitoring (HBGM), 5 days of CGM and prospective reporting of severe hypoglycaemia. The frequencies of biochemical and severe hypoglycaemia were compared in patients with normal and impaired awareness of hypoglycaemia.
  
  
  RESULTS
  Patients with impaired awareness had a 3-fold higher incidence of severe hypoglycaemia than those with normal awareness [incidence rate ratio (IRR) 3.37 (95% CI 1.30-8.7); P = 0.01] and 1.6-fold higher incidence of hypoglycaemia on weekly HBGM [IRR 1.63 (95% CI 1.09-2.44); P = 0.02]. No significant differences were observed with CGM [IRR for sensor glucose < or = 3.0 mmol/l 1.47 (95% CI 0.91-2.39); P = 0.12; IRR for sensor glucose < or = 2.2 mmol/l 1.23 (95% CI 0.76-1.98); P = 0.40].
  
  
  CONCLUSIONS
  Patients with Type 1 diabetes with impaired awareness had a 3-fold higher risk of severe hypoglycaemia and 1.6-fold higher incidence of biochemical hypoglycaemia measured with weekly glucose monitoring compared with normal awareness, but 5 days of CGM did not differentiate those with impaired from those with normal awareness.
authors.affiliation: Academic Department of Diabetes, University of Sheffield, Sheffield, UK.
authors.forename: P
authors.initials: P
authors.lastname: Choudhary
authors.forename: J
authors.initials: J
authors.lastname: Geddes
authors.forename: J V
authors.initials: JV
authors.lastname: Freeman
authors.forename: C J
authors.initials: CJ
authors.lastname: Emery
authors.forename: S R
authors.initials: SR
authors.lastname: Heller
authors.forename: B M
authors.initials: BM
authors.lastname: Frier
mesh_terms: D000328:Adult; D001364:Awareness / Q000502:physiology*; D001786:Blood Glucose / Q000032:analysis; D015190:Blood Glucose Self-Monitoring; D003922:Diabetes Mellitus, Type 1 / Q000150:complications*; D005260:Female; D006801:Humans; D007003:Hypoglycemia / Q000453:epidemiology / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013223:Statistics as Topic; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D001786:Blood Glucose