LOW (loss of warning of hypoglycaemia)

The Diabetes Audit and Research in Tayside, Scotland (DARTS) study of 367,501 people, 8655 of whom had diabetes, identified a total of 244 episodes of severe hypoglycemia in 160 patients

• overall prevalence was 7.1% in patients with type 1 diabetes and 7.3% in patients with type 2 diabetes treated with insulin, compared with 0.8% in patients with type 2 diabetes treated with an oral sulfonylurea

Loss of warning of hypoglycaemia is a well recognised phenomenon in diabetics

• repeated hypoglycemic events can lead to hypoglycemia unawareness, whereby hormonal, autonomic, sympathetic neural, and adrenomedullary responses are attenuated, such that the warning symptoms of developing hypoglycemia are essentially lost
  • subsequently compromises natural behavioral defenses against hypoglycemia, such as the ingestion of food, so that instead of an episode of mild hypoglycemia developing that can be easily self-managed by the patient, more serious episodes of hypoglycemia may occur that require external intervention
• hypoglycemia unawareness occurs as a result of a physiological response to recurrent hypoglycemic events known as hypoglycemia-associated autonomic failure
  • suggested that repeated episodes of mild hypoglycemia cause the normal glycemic thresholds for initiating sympathoadrenal, symptomatic, and cognitive responses to subsequent hypoglycemia to shift towards lower blood glucose concentrations
  • hypoglycemia unawareness ultimately leads to a significantly reduced detection of hypoglycemia in the clinical setting and to further and more severe episodes of hypoglycemia
  • there is some study evidence that as little as 2-3 weeks of scrupulous avoidance of hypoglycemia can reverse hypoglycemia unawareness
• loss of awareness of hypoglycaemia in the elderly (3)
  • distinct hypoglycemia unawareness in the presence of pronounced hypoglycemia-induced reaction time prolongation in older type 2 diabetic patients
    • may, at least in part, explain why older patients are at a particularly high risk of suffering from severe hypoglycemic episodes

Reference:

• 1) Leese GP et al.Frequency of severe hypoglycemia requiring emergency treatment in type 1 and type 2 diabetes: a population-based study of health service resource use. Diabetes Care. 2003 Apr;26(4):1176-80.
• 2) Unger J.Uncovering undetected hypoglycemic events.Diabetes Metab Syndr Obes. 2012;5:57-74. Epub 2012 Mar 8.
• 3) Bremer JP, Jauch-Chara K, Hallschmid M, Schmid S, Schultes B.Hypoglycemia unawareness in older compared with middle-aged patients with type 2 diabetes. Diabetes Care. 2009 Aug;32(8):1513-7