FREQUENCY OF SEVERE HYPOGLYCEMIA IN PATIENTS WITH TYPE-1 DIABETES WITH IMPAIRED AWARENESS OF HYPOGLYCEMIA

OBJECTIVE - To determine the frequency of hypoglycemia in patients wit h type I diabetes and impaired awareness of hypoglycemia by prospectiv e assessment. RESEARCH DESIGN AND METHODS - A prospective study was un dertaken for 12 months in 60 patients with type I diabetes: 29 had imp aired awareness of hypoglycemia and 31 retained normal awareness of hy poglycemia. The two groups of patients were matched for age, age at on set of diabetes, duration of diabetes, and glycemic control. Episodes of severe hypoglycemia were recorded within 24 h of the event and veri fied where possible by witnesses. RESULTS - During the 12 months, 19 ( 66%) of the patients with impaired awareness had one or more episodes of severe hypoglycemia with an overall incidence of 2.8 episodes . pat ient(-1) . year(-1). By comparison, 8 (26%) of the patients with norma l awareness experienced severe hypoglycemia (P < 0.01) with an annual incidence of 0.5 episode . patient(-1) . year(-1) (P < 0.001). Severe hypoglycemia occurred at different times of the day in the two groups: patients with impaired awareness experienced a greater proportion of episodes during the evening (P = 0.03), and patients with normal aware ness experienced a greater proportion in the early morning (P = 0.05). An assessment of fear of hypoglycemia revealed that patients with imp aired awareness of hypoglycemia worried more about hypoglycemia than d id patients with normal awareness (P = 0.008), but did not modify thei r behavior accordingly. CONCLUSIONS - This prospective evaluation demo nstrated that impaired awareness of hypoglycemia predisposes to a sixf old increase in the frequency of severe hypoglycemia, much of which oc curred at home during waking hours.