Section 9: Metabolic Diseases

Hypoglycemia Unawareness

Hypoglycemic unawareness is commonly defined as an inability to recognize the autonomic symptoms (sweating, tremor, hunger, anxiety, and palpitations) of decreased plasma glucose concentrations or a failure of the warning signs to occur before development of neuroglycopenia (Gerich et al., 1991). In some European countries, unawareness of hypoglycemia is considered the most important reason for denying driving privileges to individuals with diabetes mellitus (Veneman, 1996). A review of the literature suggests that hypoglycemic unawareness is a frequent phenomenon among insulin treated diabetics. Table 27 provides a summary of those studies that have investigated the frequency of hypoglycemia unawareness in individuals with diabetes. Despite the varying methodologies (e.g., populations, categorization of hypoglycemic unawareness, retrospective versus prospective surveys, etc.), the best current estimate is that hypoglycemia unawareness occurs in about 25 percent of individuals with IDDM, with estimates ranging from eight percent to 70 percent. Bergada, Suissa, Dufresne, and Schiffrin (1989) report the highest rate (70 percent). However, their total study population consisted of 350 diabetic children and some of the episodes not preceded by warning symptoms occurred during the night. The higher rates (50 and 51 percent, respectively) reported by Arias, Kernerm Zier, Navacues, and Pfeiffer (1985) and the DCCT Research Group (1991) may be the result of therapeutic regime. In both investigations, the samples consisted of IDDM individuals undergoing intensive insulin therapy.

Table 27 Summary of Studies Investigating the Frequency of Hypoglycemia Unawareness

(Reproduced from Spinger-Verlag Diabetologica, Hypoglycemic reactions in 172 Type 1 [Insulin Dependent] diabetic patients, Gerich et al., 24, 95-99, 1991 with permission from Springer-Verlag)