Sleep loss countermeasures

The Walter Reed Army Institute of Research s Department of Behavioral Biology has developed a field-deployable version of a commercial Psychomotor Vigilance Task (PVT) that has been widely used in sleep research. The software runs on handheld PDAs running the Palm Operating System (Palm OS). It is modeled after the simple reaction time task of Wilkinson and Houghton,57 as modified by Dinges and Powell.58 The Palm OS version incorporates additional stimulus, feedback, control, and data options developed by Dr. Thome. In laboratory studies, performance on the PDA task has been shown to be sensitive to time-on-task fatigue effects, sleep deprivation, and circadian variation.18 Field studies have utilized the PVT to measure the efficacy of caffeine gum as a sleep loss countermeasure. 

Population-based surveys typically have found that a substantial percentage of people report that they do not get sufficient sleep (1). While the exact prevalence may be disputed, it is an accepted fact that many people get insufficient sleep. In addition to those recognizing their insufficient sleep are other individuals who show objective evidence of excessive sleepiness, deny difficulty with sleepiness, and yet show normalization of their alertness with extended time in bed (TIB) (2). Consciously or subconsciously, people employ various stratagems to counteract the disruptive effects of their sleep loss. While the functionally disruptive effects and health risks associated with sleep loss and its consequent daytime sleepiness are generally recognized, questions remain regarding what behavioral and environment factors act as countermeasures to sleep loss and daytime sleepiness, as well as to their effectiveness and duration of effect. 

This chapter will review all of the behavioral and environmental interventions that may act as countermeasures to the disruptive effects of sleep loss on waking function. The literature addressing this question is very limited, not well organized, and quite diverse. Many questions remain unanswered. Before reviewing the evidence regarding countermeasures, we will provide a conceptual analysis of the issues surrounding them. 

The analysis above and the literature reviewed below approach the definition of a countermeasure as the external application of stimuli or conditions that counteract the impact of sleep loss. However, in the real world people often either consciously or unconsciously make behavioral choices when experiencing sleep loss. Those behavioral choices might also be considered as countermea-... 

As the above brief review indicates, very little systematic study has been done to address any of the many countermeasures reported to be beneficial to individuals experiencing sleep loss. Studies comparing the effectiveness and duration of the various countermeasures are critical to defining their use. It is only after these two questions are answered that any particular countermeasure can be appropriately used. Will the countermeasure help the sleepy driver get to the next exit or all the way home ... 

The literature on countermeasures, while incomplete and limited, suggests that most of the countermeasures studied have small and time-limited capacities to counteract the impact of sleep loss. The most difficult problem for any of the various countermeasures is the inevitable adaptation that occurs to their alerting effects. Ultimately the most effective countermeasure to sleep loss is sleep. 

Second to sleep as a countermeasure is knowledge. People tend to underestimate the impairment and risks associated with sleep loss and to overestimate the effectiveness of any given countermeasure. Risks increase when individuals are sleepy, working and driving in isolation, in a quiet darkened environment, and on long, boring tasks and roads. When one is sleepy, the potential of any countermeasure is limited in effectiveness and duration but knowledge about these facts can be a countermeasure. 

This study investigated the efficacy of using dextroamphetamine (Dexedrine ) as a countermeasure to deep loss during sustained operations in which it is impossible for persotmel to gain any restorative sleep for up to 40 hours. Although, previously published reports have proven that amphetamines are effective for enhancing performance and alertness (see Caldwell et al., 1994, for a review there had been no controlled aviation studies. However, there was evidence that amphetamines would effectively counter sleep loss and fotigue in aviation personnel. 

Thus, there was good reason to beheve that dextroamjdietamine would be an effective countermeasure for sleep loss in sustained aviation operations. However, because there were no controlled aviation studies, 12 sul ects (6 males and 6 females) were exposed to 2 periods of 40 hours of continuous wake-... 

---