Hypoglycemia and the Decision to Drive a Motor Vehicle by Persons With Diabetes

• Published in: JAMA : the journal of the American Medical Association 1999-08, Vol.282 (8), p.750-754
• Main Authors: Clarke, William L, Cox, Daniel J, Gonder-Frederick, Linda A, Kovatchev, Boris
• Format: Article
• Language: English
• Subjects: Adult; Associated diseases and complications; Automobile Driving; Biological and medical sciences; Decision Making; Diabetes; diabetes mellitus; Diabetes Mellitus, Type 1 - blood; Diabetes Mellitus, Type 1 - physiopathology; Diabetes. Impaired glucose tolerance; driving ability; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Humans; hypoglycemia; Hypoglycemia - diagnosis; Medical research; Medical sciences; Regression Analysis; Safety; traffic safety
• ISSN: 0098-7484; 1538-3598
• DOI: 10.1001/jama.282.8.750

CONTEXT Laboratory studies have shown impairments in driving performance among subjects with type 1 diabetes mellitus when their blood glucose (BG) level is between 2.6 and 3.6 mmol/L (47-65 mg/dL). However, to our knowledge, no data exist examining subjects' decisions to drive at various BG levels during their daily routine. OBJECTIVE To examine type 1 diabetic subjects' decisions to drive during their daily routine based on perception of BG levels compared with actual measured BG levels. DESIGN AND SETTING Two separate groups of patients were recruited 2 years apart from 4 academic medical centers. PARTICIPANTS All subjects were adults with type 1 diabetes who were drivers and who performed at least 2 BG tests per day. Group 1 (initial) subjects (n=65) had a mean (SD) age of 38.6 (8.9) years with a mean (SD) diabetes duration of 20.5 (10.6) years, were taking 38.8 (16.8) U/d of insulin, and had a mean (SD) glycosylated hemoglobin (HbA1) level of 10.0% (1.9%). Group 2 (replication) subjects (n=93) were 35.8 (8.0) years old with a mean diabetes duration of 17.0 (10.6) years, were taking 40.0 (15.5) U/d of insulin, and had a mean (SD) HbA1 level of 8.5% (1.6%). Each subject used a handheld computer to record data on symptoms, cognitive function, insulin dosage, food, activity, estimated and actual BG levels, and whether he/she would drive. Data were entered 3 to 6 times per day for a total of 50 to 70 collections per subject during a 3- to 4-week period. MAIN OUTCOME MEASURES Decisions to drive when subjects estimated their BG level to be less than 2.2 mmol/L (40 mg/dL), 2.2 to 2.8 mmol/L (40-50 mg/dL), 2.8 to 3.3 mmol/L (50-60 mg/dL), 3.3 to 3.9 mmol/L (60-70 mg/dL), 3.9 to 10 mmol/L (70-180 mg/dL), and more than 10 mmol/L (>180 mg/dL), and driving decisions when actual BG levels were in these ranges. RESULTS Subjects stated they would drive 43% to 44% of the time when they estimated their BG level to be 3.3 to 3.9 mmol/L (60-70 mg/dL), and 38% to 47% of the time when their actual BG level was less than 2.2 mmol/L (40 mg/dL). Logistic regression analysis demonstrated that number of autonomic symptoms, degree of impairment on cognitive function tests, and BG level estimate predicted 76% to 80% of decisions to drive (P