Severe hypoglycemia in type I diabetic patients with impaired kidney function.

Objective: To assess the frequency and possible risk indicators of severe hypoglycemia in insulin-dependent (type I) diabetic patients with impaired kidney function.
Research Design and Methods: Retrospective follow-up examination of case subjects and control subjects with mean follow-up periods of 2.9 and 1.3 yr, respectively. The setting was the diabetes center at the Düsseldorf University hospital. Subjects were consecutive type I diabetic patients. Case subjects consisted of 44 patients with initial serum creatinine levels of greater than or equal to 133 microM and pathological proteinuria. Control subjects consisted of 46 patients with normal serum creatinine levels matched for age, duration of diabetes, and hypertension; 57% of case subjects and 67% of control subjects were being treated with beta-blockers. Incidence of severe hypoglycemia (cases/patient-yr) was assessed through an interviewer-administered questionnaire.
Results: At comparable levels of HbA1c (7.9 +/- 1.8 vs. 7.6 +/- 1.1%), case subjects had a fivefold higher incidence of severe hypoglycemic episodes (1.28 vs. 0.25 cases/patient-yr, P less than 0.02) than control subjects. Within the group with impaired kidney function, patients with severe hypoglycemic episodes had lower HbA1c levels (7.4 +/- 1.6 vs. 8.7 +/- 2.0%, P less than 0.03) and a lower body mass index (22.0 +/- 3.4 vs. 24.4 +/- 3.8 kg/m2, P less than 0.04) than those without severe hypoglycemic episodes, whereas serum creatinine levels, body weight-related insulin dosage (U x kg-1 x day-1), prevalence of blindness, autonomic neuropathy, and treatment with beta-blockers were comparable.
Conclusions: Type I diabetic patients with impaired kidney function are at an excessively high risk of severe hypoglycemia. In addition to low HbA1c levels, a low body mass index appears to be a risk indicator for this adverse effect of insulin therapy.