The MSLT/MWT Should be Used for the Assessment of Workplace Safety

Increased awareness of the role of sleepiness as a contributing or causative factor in workplace accidents and driving fatalities has resulted in a new role for sleep specialists. Some regulatory agencies including the Federal Aviation Association (FAA), and the Federal Motor Carriers Safety Association (FMCSA), have looked to the sleep specialist to evaluate the safety of returning an individual to their workplace after the transportation employee has been diagnosed and treated for sleep disorders. This has placed an incredible responsibility on the sleep specialist. While the sleep specialist may not want to embrace this responsibility, it is clearly within the realm of sleep medicine and there is no other group of professionals better equipped to make such decisions. The American Academy of Sleep Medicine (AASM) recognizes this role for sleep specialist and has stated in its Practice Parameters that “the sleep clinician is responsible for assessing response to treatment, and making clinical decisions that affect individual and public safety.” 1 (p114) To aid the sleep clinician in the decision process, there are both objective and subjective measures available. However, given the implications of releasing an individual to return to an occupation with a high safety risk, the focus has been on objective testing rather than just subjective reports which are prone to bias and manipulation. The two objective tests available for evaluation of sleepiness and alertness are the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT), respectively. They have been used for decades in the evaluation of medications, diagnosis of sleep disorders, and in evaluation of response to treatment for patients with sleep disorders. In response to the increasing awareness of the dangers of impaired alertness on personal and public safety in the workplace especially in high risk occupations, the use of these tests has expanded to include the assessment of workplace safety. In particular, the MWT has become the logical test to use in the evaluation of patients with sleep disorders associated with daytime sleepiness and other individuals who have been identified as posing a potential risk in the workplace due to impaired alertness. With new research demonstrating the usefulness and validity of the MWT in the assessment of safety, the MWT should now be a routine part of any evaluation of individuals for workplace safety. Reliability and Validity of the MSLT and MWT An important aspect of the MSLT and MWT is that they are de facto gold standards with demonstrated validity. The MSLT has been shown to be a reliable and valid measure of sleepiness. Its validity is based on numerous studies that show decreased latencies following sleep deprivation, 2 sleep fragmentation, 3-5 and use of hypnotic medications. 6,7 In addition, increased latencies have been demonstrated following extended sleep 2 and the use of stimulant medication. 8-11 The MSLT has also been shown to have a high test-retest reliability of 0.97 in normal subjects which is not affected by test intervals or level of sleepiness. 12 Based on these and numerous other studies, the Practice Parameters state that “the MSLT is a validated objective measure of the ability or tendency to fall asleep.” 1 (p115)