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23 apnea. A subsequent study by Young, Blustein, Finn, and narcolepsy). While sleep apnea is more prevalent in drivers Palta (1997) determined that the relative risk of being involved who are male, middle-aged, and slightly overweight, nar- in a motor vehicle crash if one has sleep apnea is approxi- colepsy affects both men and women, can run in families, and mately four times normal risk. can appear at an earlier age. Excessive daytime sleepiness Findley et al. (1989) conducted a driving simulator experi- occurs every day, regardless of the amount of sleep obtained ment in patients with and without sleep apnea. The patients at night and can therefore put drivers at an increased risk for with sleep apnea hit a greater number of obstacles during their crash involvement. 30-min simulated drive than did the control group (drivers with Findley et al. (1995) conducted a study on vigilance and no known sleep apnea). However, studies have also shown automobile accidents in patients with narcolepsy as well as that drivers who are successfully treated for sleep apnea those with sleep apnea. A computer program simulating a reduced their crash risk significantly (George et al. 1996). long and monotonous highway drive was presented to drivers Young et al. (1993) have also suggested that increased preva- for 30 min. The patients with untreated narcolepsy hit a higher lence of sleep apnea occurs due to many factors that drivers percentage of obstacles while performing on the simulator, could detect themselves, such as age, gender, weight, and indicating a greatly increased likelihood of crash involvement. snoring. However, commercial drivers may be reluctant to be George, Boudreau, and Smiley (1996) also conducted a screened or treated for sleep apnea due to cost and concerns laboratory-based divided attention driving test (DADT) in of job security. Further, the method for treatment (e.g., con- a simulated environment on patients with narcolepsy and tinuous positive airway pressure [CPAP], surgery) can be con- patients with sleep apnea. Their study showed that narcolepsy sidered costly, too obtrusive, or too burdensome if treatment patients were sleepier than patients with obstructive sleep is needed nightly (Flemons 2002). Long-term health conse- apnea, and tracking error was much worse in both sets of quences of sleep apnea and the long-term relationship of this patients when compared with a control group. disorder to crash risks are major concerns. Aldrich (1989) also conducted a study of automobile crashes Pack et al. (2002) estimated the prevalence of sleep apnea in patients with sleep disorders, primarily narcolepsy and sleep among commercial drivers and quantitatively assessed the apnea. Aldrich found the highest sleep-related crash rates in effects of sleep apnea on driving-related performance. narcoleptics. Aldrich (1989) and Findley et al.'s findings sug- The study found that mild sleep apnea occurs in 17.6% of gest that both sleep apnea and narcolepsy are sleep disorders those holding CDLs, moderate sleep apnea in 5.8%, and that need to be investigated further. severe sleep apnea in 4.7%. Deficits in vigilance and various sensory-motor tasks were associated with the increasing 4.4.3 Diabetes severity of sleep apnea. Objective measures associated with sleep apnea severity included sleep latency (a standard mea- Diabetes, a common chronic disease, is of concern to licens- sure of drowsiness), Psychomotor Vigilance Test (PVT) ing agencies because individuals with diabetes may experience reaction time and lapses, and tracking errors on a divided periods of hypoglycemia when treated with insulin. Hypo- attention task. Sleep apnea was associated with shorter glycemia can alter judgment and perception and can even lead sleep durations, but neither sleep apnea severity nor sleep to a loss of consciousness while driving. Laberge-Nadeau duration was associated with subjective self-reports of (2000) estimated the impact of diabetes on crash risk in a study sleepiness by driver subjects. Thus, driver self-monitoring consisting of commercial drivers and truck-permit holders. of their levels of alertness and drowsiness is not likely to Data on permits, medical conditions, and crashes of 13,453 per- provide valid assessments. mit holders from 1987 to 1990 were used in the analysis as Obesity is a prime risk factor for sleep apnea, and the inci- well as a telephone survey conducted from 1990 to 1991 that dence of obesity among CMV drivers is approximately twice collected information on driving patterns and exposure. The that of the general population (Roberts and York 2000). Other findings showed that there was an increased crash risk for health conditions and behaviors for which commercial drivers the permit holders and for the professional drivers with the compare unfavorably with the general population include diet, same type of permit and with uncomplicated diabetes not exercise, hypertension, stress, and smoking. treated with insulin. Permit holders for single-unit trucks who are diabetic without complications and not using insulin had an 4.4.2 Narcolepsy increased crash risk of 1.68 when compared with healthy per- mit holders of the same permit class. Commercial drivers with Narcolepsy is principally characterized by a permanent and a single-unit truck permit and the same diabetic condition overwhelming feeling of sleepiness and fatigue. Other symp- had an increased risk of 1.76. Surprisingly, the findings also toms involve abnormalities of dreaming sleep, such as dream- showed that insulin use was not identified with higher crash like hallucinations and finding oneself physically weak or risk. However, this could be due to the limited number of com- paralyzed for a few seconds. It impacts 1 in every 2,000 mercial drivers with severe diabetes. Many fleets screen their Americans ( drivers and applicants for insulin-based diabetes.