Abstracts

Driving performance is a skill in which impaired vigilance due to diabetic hypoglycemia (HG) has both personal and public health consequences. Studies with the use of a driving simulator show that driving impairment occurs coincident with impaired vigilance measured by EEG that accompanies onset of hypoglycemic symptoms. We evaluate whether recent driving history or awareness of HG during driving are associated with changes in EEG-vigilance measured while driving during euglycemia (EG) or during HG. Simulated driving was monitored in two 30 minute trials on 2 consecutive days. During EG driving, blood glucose (BG) was maintained through an insulin clamp to levels [sim]100 mg/dl. For HG driving, BG was gradually decreased from an initial target of [sim]70 mg/dl to [sim]50 mg/dl. Self-treatment of hypoglycemia was scored as [ldquo]present [ldquo] or [ldquo]absent[rdquo] depending on whether the patient drank a [ldquo]sugar soda[rdquo] (a non-sugar, diet soda) to correct perceived HG symptoms during simulated driving. Recent driving mishaps were scored according to the patients[apos] self-report of driving accidents or moving citations within the past two years. Multi-channel digital EEG was acquired was acquired during simulated driving trials. Relative EEG spectral power data was averaged into five-minute epochs to correspond with BG sampling rate. The difference between relative alpha and theta powers at the central vertex (ATDiff) was used to quantify vigilance. Outcomes were modeled using binary logistic regression with self-treament (+/-) and driving mishaps (+/-) as dependent variables, and BG and ATDiff during EG and HG epochs as independent variables.[sim] Thirty-two subjects completed both EG and HG trials. 60% self-treated HG during HG driving, and 68% admitted to recent driving mishaps. Driving history and self-treatment were not significantly associated (Chi square = 2.54, p = 0.28). Subjects overall showed increasing delta power with decreasing BG. In the case of driving mishaps, increasing ATDiff during both EG (B=4.13, p=0.008) and HG (B=3.41, p=0.02) driving trials predicted driving mishaps. In the case of self-treatment of HG, decreasing ATDiff during HG driving did not significantly predict self-treatment. However, values of ATDiff increasingly diverged with worsening BG, with self-treating subjects experiencing decreasing ATDiff. Task-acquired EEG shows worse vigilance in diabetics who successfully recognize and treat HG. EEG vigilance is impaired in diabetics who have no self-reported history of driving mishaps. These findings suggest that mechanisms independent of EEG vigilance may allow compensation for hypoglycemia-associated performance.