O B J E C T I V E -P ro g ressive hypoglycemia leads to cognitive-motor and driving impairments. This study evaluated the blood glucose (BG) levels at which driving was impaired, imp a i rment was detected, and corrective action was taken by subjects, along with the mechanisms underlying these three issues. RESEARCH DESIGN AND METHODS -T h e re were 37 adults with type 1 diabetes who drove a simulator during continuous euglycemia and pro g ressive hypoglycemia. During testing, driving perf o

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... nce, EEG, and corrective behaviors (drinking a soda or discontinuing driving) were continually monitored, and BG, symptom perception, and judgement concern i n g i m p a i rment were assessed every 5 min. Mean ± SD euglycemia perf o rmance was used to quantify z s c o res for perf o rmance in three hypoglycemic ranges (4.0-3.4, 3.3-2.8, and 2.8 mmol/l). R E S U LT S -During all three hypoglycemic BG ranges, driving was significantly impaire d , and subjects were aware of their impaired driving. However, corrective actions did not occur until BG was 2.8 mmol/l. Driving impairment was related to increased neurogenic symptoms and increased theta-wave activity. Aw a reness of impaired driving was associated with n e u roglycopenic symptoms, increased beta-wave activity, and awareness of hypoglycemia. High beta and low theta activity and awareness of both hypoglycemia and the need to tre a t low BG influenced corrective behavior. C O N C L U S I O N S -Driving perf o rmance is significantly disrupted at relatively mild hypoglycemia, yet subjects demonstrated a hesitation to take corrective action. The longer t reatment is delayed, the greater the neuroglycopenia (increased theta), which precludes corrective behaviors. Patients should treat themselves while driving as soon as low BG and/or imp a i red driving is suspected and should not begin driving when their BG is in the 5.0-4.0 mmol/l range without prophylactic tre a t m e n t .