EFFECTS ON DRIVING ABILITY
Hypoglycemia is a common adverse effect of insulin treatment in people with diabetes, potentially leading to cognitive impairment, altered levels of consciousness, and delayed reactions (Diamond, Collins, and Rohl 2005). If such reactions occur while operating a motor vehicle, a crash is likely. These authors note that the gold standard of care recommended by the American Diabetes Association for the strict glycemic control of individuals with Type I diabetes to prevent long-term complications of the disease is not without risk, and has the potential to result in more frequent and catastrophic hypoglycemia.33 Diabetic drivers are potentially at increased risk for motor vehicle crashes as a result of both their therapy (insulin induced hypoglycemia) and diabetic complications (e.g., retinopathy with visual disturbances).
Szlyk et al. (2004) queried 25 licensed drivers age 34 to 72 with diabetic retinopathy regarding the number of crashes in which they had been involved in the prior 5-year period. Blood was also drawn to determine glycosylated hemoglobin levels. Unlike blood glucose levels that vary between days, glycosylated hemoglobin levels measure hyperglycemia over a period of 2 to 3 months, and have been shown to predict the progression of diabetic retinopathy. The mean glycosylated hemoglobin level was 9.2 percent, with a range of 6.4 percent to 11.6 percent. Szlyk et al. (2004) report that the normal range of glycosylated hemoglobin in nondiabetic individuals is 4.0 to 6.0 percent, and that the American Diabetes Association recommends a target goal of less than 7.0 percent for diabetic patients. Nineteen of the 25 subjects in the study had glycosylated hemoglobin levels greater than 7.0 percent. Subjects who had one or more crashes within the past 5 years had a significantly higher glycosylated hemoglobin level than those not reporting crashes. The authors concluded that the majority of the study group had not achieved the target level for glycosylated hemoglobin recommended by the American Diabetes Association, which mirrors the findings of epidemiologists who indicate that the majority of people with diabetes do not achieve a target goal for glycosylated hemoglobin (Klein et al., 1988). This puts them at higher risk of the progression of diabetic retinopathy, as well as at higher risk of automobile crashes.