Hypoglycemia Unawareness in Older Compared With Middle-Aged Patients With Type 2 Diabetes

OBJECTIVE - Older patients with type 2 diabetes are at a particularly high risk for severe hypoglycemic episodes, and experimental studies in healthy subjects hint at a reduced awareness of hypoglycemia in aged humans. However, subjective responses to hypoglycemia have rarely been assessed in older type 2 diabetic patients. RESEARCH DESIGN AND METHODS - We tested hormonal, subjective and cognitive responses (reaction time) to 30-min steady-state hypoglycemia at a level of 2.8 mmol/l in 13 older (>= 65 years) and 13 middle-aged (39-64 years) type 2 diabetic patients. RESULTS - Hormonal counterregulatory responses to hypoglycemia did not differ between older and middle-aged patients. In contrast, middle-aged patients showed a pronounced increase in autonomic and neuroglycopenic symptom scores at the end of the hypoglycemic plateau that was not observed in older patients (both P < 0.01). Also, seven middle-aged patients, but only one older participant, correctly estimated their blood glucose concentration to be <3.3 mmol/l during hypoglycemia (P = 0.011). A profound prolongation of reaction times induced by hypoglycemia in both groups persisted even after 30 min of subsequent euglycemia, CONCLUSIONS - Our data indicate marked subjective unawareness of hypoglycemia in older type 2 diabetic patients that does not depend on altered neuroendocrine counter-regulation and may contribute to the increased probability of severe hypoglycemia frequently reported in these patients. The joint occurrence of hypoglycemia unawareness and deteriorated cognitive function is a critical factor to be carefully considered in the treatment of older patients.