Type 1 Diabetic Drivers With and Without a History of Recurrent Hypoglycemia–Related Driving Mishaps: Physiological and performance differences during euglycemia and the induction of hypoglycemia

OBJECTIVE: Collisions are more common among drivers with type 1 diabetes than among their nondiabetic spouses. This increased risk appears to be attributable to a subgroup of drivers with type 1 diabetes. The hypothesis tested is that this vulnerable subgroup is more at risk for hypoglycemia and its disruptive effects on driving. RESEARCH DESIGN AND METHODS: Thirty-eight drivers with type 1 diabetes, 16 with (+history) and 22 without (−history) a recent history of recurrent hypoglycemia-related driving mishaps, drove a virtual reality driving simulator and watched a videotape of someone driving a simulator for 30-min periods. Driving and video testing occurred in a double-blind, randomized, crossover manner during euglycemia (5.5 mmol/l) and progressive hypoglycemia (3.9–2.5 mmol/l). Examiners were blind to which subjects were +/−history, whereas subjects were blind to their blood glucose levels and targets. RESULTS: During euglycemia, +history participants reported more autonomic and neuroglycopenic symptoms (P ≤ 0.01) and tended to require more dextrose infusion to maintain euglycemia with the same insulin infusion (P < 0.09). During progressive hypoglycemia, these subjects demonstrated less epinephrine release (P = 0.02) and greater driving impairments (P = 0.03). CONCLUSIONS: Findings support the speculation that there is a subgroup of type 1 diabetic drivers more vulnerable to experiencing hypoglycemia-related driving mishaps. This increased vulnerability may be due to more symptom “noise” (more symptoms during euglycemia), making it harder to detect hypoglycemia while driving; possibly greater carbohydrate utilization, rendering them more vulnerable to experiencing hypoglycemia; less hormonal counterregulation, leading to more profound hypoglycemia; and more neuroglycopenia, rendering them more vulnerable to impaired driving.