The Epworth Sleepiness Scale for screening of the drowsy driving: comparison with the maintenance of wakefulness test in an Iranian sample of commercial drivers.

Traffic fatalities are a major cause of morbidity and mortality in Iran. Occupational sleep medicine field needs more cost-effective and applicable tests for screening purposes. This study reports on a pilot screening study for drowsy drivers in an urban Iranian sample of commercial drivers. The Maintenance of Wakefulness Test (MWT) measures the ability to remain awake objectively. Sleep latency in MWT is a reasonable predictor of driving simulator performance in drivers. In this study, we evaluate whether the Epworth Sleepiness Scale (ESS) and MWT are equally useful in drivers with possible Excessive Daytime Sleepiness (EDS). 46 consecutive road truck drivers in a transportation terminal entered into this study. The ESS score of patients with normal and abnormal MWT was 3.24±2.4 and 4.08±3 respectively which was not significantly differenced (P value = 0.34). No significant correlation was found between the ESS and sleep latency in MWT (r=-0.28, 95%CI= -0.58 to 0.02). By using the receiver operating characteristic analysis, the area under the curve was found to be 0.57 (95% confidence interval = 0.37- 0.77) which is not statistically acceptable (P value=0.46). Our finding showed that the MWT and ESS do not measure the same parameter.