Objective: While it is clear that progressive diabetic hypoglycemia leads to neuroglycopenia, which impairs driving, it is not clear what contributes to patients' detection and subsequent self-correction of hypoglycemia/driving impairments. Drivers with Type 1 Diabetes Mellitus (T1DM) who did and did not engage in self-treatment during experimental hypoglycemia driving are compared physiologically and psychologically.
Method: 38 drivers with T1DM drove a sophisticated driving simulator during euglycemia and progressive hypoglycemia. Subjects were continually monitored for driving performance, EEG activity and whether they self-treated with a glucose drink. Every 5 min measures were taken of blood glucose (BG) and epinephrine levels, perceived neurogenic and neuroglycopenic symptoms and driving ability. For the four weeks prior to this hospital study, subjects participated in a field study. Using a hand-held computer just prior to routine self-measurements of BG, subjects rated neurogenic and neuroglycopenic symptoms and made judgements about BG level and ability to drive as they did in the hospital.
Results: Drivers who did and did not self-treat did not differ in terms of their pre-hospital exposure to hypoglycemia, their depth and rate of BG fall during experimental testing, or their epinephrine response to hypoglycemia. Subjects who self-treated detected more neurogenic and neuroglycopenic symptoms than those who did not self-treat. They also experienced less EEG defined neuroglycopenia during the progressive hypoglycemic drive as compared to those who did not self-treat. Perceived need to self-treat and EEG parameters correctly classified 88% of those who did treat from those who did not self-treat. Further, subjects who self-treated were more aware of hypoglycemia and when not to drive while hypoglycemic in the field study.
Conclusion: There is a narrow window between a patient's detection of hypoglycemic symptoms and the need to self-treat, and neuroglycopenia, which impairs self-treatment. Consequently, drivers with T1DM should be vigilant for signs of hypoglycemia and driving impairment (e.g. trembling, uncoordination, visual difficulties) and encouraged to treat themselves immediately when they suspect hypoglycemia while driving.