Purpose: The present study describes the epidemiology of severe hypoglycemia and identifies patient characteristics or behaviors associated with severe hypoglycemia in patients with insulin-dependent diabetes mellitus (IDDM) participating in the Diabetes Control and Complications Trial (DCCT).
Patients and methods: The DCCT is a multicenter randomized clinical trial designed to compare the benefits and risks of intensive therapy with those of conventional management of IDDM. The DCCT's feasibility phase demonstrated that intensive therapy, with the aim of achieving glucose levels as close to the non-diabetic range as possible, was accompanied by a threefold increase in severe hypoglycemia compared with conventional therapy. This report is based on the first 817 subjects who entered the DCCT, with a mean follow-up of 21 months.
Results: Two hundred sixteen subjects reported 714 episodes of severe hypoglycemia; 549 (77%) occurred in intensively treated subjects. The incidence of severe hypoglycemia in the intensive treatment group ranged from two to six times that observed with conventional treatment. Severe hypoglycemia occurred more often during sleep (55%); 43% of all episodes occurred between midnight and 8 AM. Of episodes that occurred while subjects were awake, 36% were not accompanied by warning symptoms. In intensively treated subjects, predictors of severe hypoglycemia included history of severe hypoglycemia, longer duration of IDDM, higher baseline glycosylated hemoglobin (HbA1c) levels, and a lower recent HbA1c. Multivariate analyses failed to yield predictive models with high sensitivity.
Conclusions: In the DCCT, intensive treatment of IDDM increased the frequency of severe hypoglycemia relative to conventional therapy. Intensive treatment may cause even more frequent severe hypoglycemia when applied to less selected and less motivated populations in the clinical practice setting. These findings underscore the importance of determining the benefit-risk ratio of intensive and standard therapy of IDDM.